SIM in Ophthalmology

(1)

Self-Instructional Materials

in Ophthalmology

Edited By

Marissa N. Valbuena M.D., MHPEd

Associate Professor

Department of Ophthalmology and Visual Science

College of Medicine

University of the Philippines Manila

(2)

Authors iv

Preface vi

1. Anatomy of the Eye

1 Marissa N. Valbuena M.D., MHPEd

2. Physiology of the Eye

18 Richard C. Kho, MD

3. Ocular Symptomatology

33 Marissa N. Valbuena M.D., MHPEd & Arnold T. Salud M.D.

4. Eye Examination

38 Teresita R. Castillo, MD, MHPEd

5. Disturbance in Vision

5.1 Disorders of the Cornea

53 Ruben LimBonSiong, MD

5.2 Cataract

67 Leonardo R. Mangubat, MD

5.3 Disorders of the Retina, Choroid and Vitreous

73 Pearl T. Villalon, MD

5.4 Glaucoma

88 Norman M. Aquino, MD & Marissa N. Valbuena M.D., MHPEd

5.5 Disorders of the Optic Nerve

98 Raul D. Cruz, MD

5.6. Errors of Refraction

107 Juan Ma. Pablo R. Nañagas, MD, MPH, MSNA

6. Red Eye , Tearing and Discharge

6.1 The Red Eye

115 Leo D. P. Cubillan, MD, MS

6.2 Uveitis and Scleritis

120 Teresita R. Castillo, MD, MHPEd

6.2 Tearing

146

(3)

Marissa N. Valbuena M.D., MHPEd

7.2 Proptosis

167 Prospero Ma. C. Tuaño, MD

8. Special Topics

8.1 Retinoblastoma

179 Rolando Enrique D. Domingo, MD

8.2 Ocular Manifestations of Systemic Diseases

187 Romulo N. Aguilar, MD, PhD & Teresita R. Castillo, MD, MHPEd

8.3 Eyelid Malposisitons

206 Franklin P. Kleiner, M.D.

8.4 Ocular Trauma and Emergencies

221 Ma. Margarita L. Luna, MD, Marissa N. Valbuena M.D., MHPEd &

Paulo Ma. N. Pagkatipunan, MD, MHA

8.5 Ocular Pharmacology

235 Rosie R. Noche, MD

(4)

Romulo N. Aguilar, MD, PhD Clinical Associate Professor

Department of Ophthalmology and Visual Science

College of Medicine

University of the Philippines Manila

Ocular Manifestations of Systemic Diseases

Richard C. Kho, MD

Clinical Associate Professor

College of Medicine

Physiology of the Eye

Norman M. Aquino, MD Clinical Associate Professor

College of Medicine

Glaaucoma

Franklin P. Kleiner, MD Clinical Associate Professor

College of Medicine

Eyelid Malpositions

Teresita R. Castillo, MD, MHPEd Clinical Associate Professor

College of Medicine

Eye Examination ; Uveitis and Scleritis ; Ocular Manifestations of Systemic Diseases

Ruben LimBonSiong, MD Clinical Associate Professor

College of Medicine

Disorders of the Cornea

Leo D. P. Cubillan, MD, MS Clinical Associate Professor

College of Medicine

Red Eye

Ma. Margarita L. Luna, MD Clinical Associate Professor

College of Medicine

Ocular Trauma and Emergencies

Raul D. Cruz, MD

College of Medicine

Disorders of the Optic Nerve

Leonardo R. Mangubat, MD Associate Professor

College of Medicine

Cataract

Rolando Enrique D. Domingo, MD Clinical Associate Professor

College of Medicine

Retinoblastoma

Juan Ma. Pablo R. Nañagas, MD, MPH, MSNA Professor

College of Medicine

(5)

College of Medicine

Ocular Trauma and Emergencies

College of Medicine

Proptosisi

Rosie R. Noche, MD

College of Medicine

Ocular Pharmacology

Marissa N. Valbuena, MD, MHPEd Associate Professor

College of Medicine

Anatomy of the Eye ; Ocular Symptomatology ; Glaucoma ; Strabismus ; Ocular Trauma and Emergencies

Arnold T. Salud, MD

College of Medicine

Ocular Symptomatology

Pearl T. Villalon, MD Associate Professor

College of Medicine

Disorders of the Retina, Choroid and Vitreous

Alexander D. Tan, MD Clinical Associate Professor

College of Medicine

(6)

Preface

In the Organ System Integration Curriculum of the UP College of Medicine the medical student will

have their first exposure to the field of Ophthalmology at Year Level IV. The Sensory Organs –

Eye Module is a 4-day rotation consisting of didactic lectures, small group discussions and practicum

of skills in history taking and ocular examination. Aside from the introductory lectures in Anatomy

and Physiology of the Eye and Ocular History and Eye Examinations, the rest of the module will be

problem based, covering the different eye problems that patients may present in the clinic. This

series of self-instructional materials is organized in the same manner, with additional topics of

Ocular Manifestations of Systemic Diseases, Ocular Trauma and Emergencies and Ocular

Pharmacology at the end of the series. These study materials will supplement the lectures the

medical students will receive and will also help them in preparing for the small group discussions.

Marissa N. Valbuena MD, MHPEd

(7)

ANATOMY OF THE EYE

Marissa N. Valbuena M.D., MHPEd

INTRODUCTION

An understanding of the anatomy of the eye, orbit, visual pathway and the central control of ocular movements is essential in understanding the eye diseases and other diseases which have ocular manifestations. This module is an overview of the anatomy of the eye and the student is advised to read the references listed at the end of the module for more details.

OBJECTIVES

After the completion of this instructional material, the student is expected to 1. Describe the different parts of the eye and adnexae.

2. Describe the functions of the parts of the eye and adnexae.

PREREQUISITE KNOWLEDGE AND PREPARATION

The materials discussed in this module is the prerequisite of all the subsequent modules.

INTENDED USERS

This module was developed to provide the medical student with the background knowledge of the anatomy of the eye and adnexae. Together with the module on “Physiology of the Eye”, this module will help the student understand how the eye functions, how patients can be evaluated and examined and how the different eye disorders manifest in patients..

CONTENT

Outline : A. Orbit B. Eyeball 1. Conjunctiva 2. Tenon’s capsule 3. Sclera and episclera 4. Cornea

5. Uveal tract – iris, ciliary body, choroid 6. Lens

7. Aqueous

8. Anterior chamber angle 9. Retina 10. Vitreous C. Extraocular muscles D. Ocular adnexae 1. Eyebrows 2. Eyelids 3. Orbital septum

(8)

4. Lid retractors 5. Lacrimal Comples E. Optic nerve

ORBIT

The orbit is a pear shaped structure with the optic nerve as its stem. It is 30 cc in volume in adults and the eye occupies 20 % of the space and the muscles and fat accounts for the rest. The orbit is limited anteriorly by the orbital septum, which serves as a barrier between the eyelid and the orbit. It is also related to the frontal sinus above, maxillary sinus below and the ethmoid and sphenoid sinuses medially.

Orbital Walls

1. Roof : frontal bone, sphenoid bone

2. Lateral wall : sphenoid bone, zygomatic bone 3. Floor : maxillary bone, zygomatic bone

4. Medial wall : ethmoid, lacrimal bone, frontal bone, maxillary bone

Fig 1. Orbital walls

Orbital Apex

The orbital apex is the entry site of all the nerves and blood vessels to the eye and all the extraocular muscles except the inferior oblique

(9)

Blood Supply

A. Arterial Supply : Ophthalmic Artery (branch of internal carotid artery) 1. Central retinal artery

2. Lacrimal artery – supplies lacrimal gland and upper eyelid

3. Muscular branches to the muscles – continue to form the anterior ciliary arteries and supply the sclera, episclera, limbus and conjunctiva and contribute to the major arterial circle of the iris.

4. Long posterior ciliary arteries – supplies the ciliary body. The 2 long posterior ciliary arteries anastomose with each other and with the anterior ciliary arteries to form the major arterial circle of the iris.

5. Short posterior ciliary arteries – supply choroid and part of the optic nerve 6. Medial palpebral arteries to both eyelids

B. Venous Drainage :

Superior and inferior ophthalmic veins, into which drains the vortex veins, anterior ciliary veins and the central retinal vein. The ophthalmic veins communicate with the cavernous sinus. The skin of the periorbital region drain to the angular vein, and to the supraorbital and supratrochlear vein branches of the superior ophthalmic vein. This provides a direct communication between the skin of the face and the cavernous sinus.

EYEBALL

1. CONJUNCTIVA

The conjunctiva is a thin transparent mucous membrane consisting of 2 parts

1. Palpebral conjunctiva – lines the posterior surface of the eyelid and is adherent to the tarsus.

2. Bulbar conjuctiva – is loosely attached to the orbital septum in the fornices and is folded many times. This allows the eye to move and enlarge the secretory conjunctival surface. The semilunar fold is a thickened fold of bulbar conjunctival at the inner canthus and corresponds to the nictitating membrane of lower animals.

The conjunctiva has the following layers:

1. Conjunctival epithelium – consists of 2-5 layers of stratified columnar epethelial cells. The superficial epithelial cells consists of mucous secreting goblet cells. The basal epithelial cells are deeper and may contain pigments near the limbus.

2. Conjuctival stroma has an adenoid (superficial) layer and a fibrous (deep) layer. The adenoid layer contains lymphoid tissue and ‘follicle-like” structures without germinal centers. and develops after the 2nd_{or 3}rd_{month of life. The fibrous layer is composed of connective tissue that attaches to the}

tarsus and is loosely arranged over the globe. The accessory lacrimal glands (glands of Krause and Wolfring) located in the stroma resemble the lacrimal gland in structure and function.

The conjunctival arteries are derived from the anterior ciliary and palpebral arteries and anastomose freely. Conjuctival veins follow the arterial pattern. The conjuctival lymphatics with the lymphatics of the eyelids form a rich lymphatic plexus. The conjunctiva is innervated by the ophthalmic (first) division of the trigeminal nerve.

2. TENON’S CAPSULE

The Tenon’s capsule is a fibrous membrane covering the globe from the limbus to the optic nerve At the limbus, the conjuctiva, Tenon’s capsule and the episclera are fused together. Posteriorly the inner surface of the Tenon’s capsule lies against the sclera and the outer aspect lies in contact with the orbital fat and structures within the extraocular muscle cone. At the point where Tenon’s capsule is pierced by the tendons

(10)

of the extraocular muscles, it sends out tubular reflections around each of the muscles. These fascial reflections become continuous with the fascia of the muscles and the fused fascia send out expansions to the surrounding structures and to the orbital bones called check ligaments. Inferiorly, the Tenon’s capsule fuse with the fascia of the inferior rectus and inferior oblique to form the suspensory ligament of Lockwood, upon which the globe rests.

3. SCLERA AND EPISCLERA

The sclera is the fibrous outer layer of the eye consisting mainly of collagen. It is dense and white and continuous with the cornea anteriorly and the optic nerve dural sheath posteriorly. It is thinnest at the insertion of the recti mucles (0.3 mm); elsewhere it is 0.6 mm thick. The outer layer of the anterior sclera is covered with a thin layer of fine elastic tissue, the episclera, which contains blood vessels that nourish the sclera.

Fig 3. Cross section of the eye

4. CORNEA

The cornea is a transparent tissue inserted to the sclera at the limbus. It is thicker at the periphery (0.65 mm) than at the center (0.52 mm). Its horizontal diameter (11.75 mm) is slightly bigger than its vertical diameter (10.6 mm)

There are 5 layers of the cornea :

1. Epithelium : 5-6 layers of cells, continuous with the epithelium of the bulbar conjunctiva 2. Bowman’s membrane : clear acellular layer, a modified portion of the stroma.

3. Stroma : 90 % of corneal thickness; composed of intertwining lamellae of collagen fibrils that run parallel to the surface of the cornea and because of their size and proximity are optically clear. The lamellae run within the ground substance of hydarated polyglycans in association with the keratocytes that produce the collagen and ground substance.

4. Descemet’s membrane : basal lamina of corneal endothelium

5. Endothelium : single layer of cells ; responsible for maintaining the deturgescence of the cornea and failure of function leads to corneal edema. Cell loss occurs with age and injury. Endothelial repair occurs with cell enlargement and sliding of existing cells with minimal capacity for cell division.

(11)

The cornea gets its nutrition from the vessels of the limbus, the aqueous and the tears. The superficial cornea gets most of its oxygen from the tears. The sensory nerves of the cornea is from the ophthalmic division of the trigeminal nerve.

The transparency of the cornea is due to its uniform structure, avascularity, and deturgescence. 6. UVEAL TRACT

The uveal tract is composed of the iris , the ciliary body and the choroid. It is the middle vascular layer of the eye and contributes to the blood supply of the retina.

A. IRIS

Is a flat surface with a central opening, the pupil. The iris lies in contiguity with the anterior surface of the lens, dividing the anterior chamber from the posterior chamber, both of which contains aqueous humor. Within the stroma of the iris are the sphincter and dilator muscles. The 2 pigmented posterior layers of the iris represent anterior extensions of the neuroretina and the retinal pigment epithelium (RPE).

The blood supply of the iris is from the major circle of the iris. The iris capillaries are non fenestrated. Sensory supply is from fibers of the ciliary nerve.

The pupil controls the light entering the eye. The papillary size is determined by the balance between constriction due to parasympathetic activity via the oculomotor nerve and dilation due to sympathetic activity.

B. CILIARY BODY

The ciliary body consists of 2 zones

1. Pars plicata : 2 mm wide; ciliary processes arise from this zone. The ciliary processes are composed mainly of large fenestrated capillaries and veins that drain to the vortex veins. The 2 layers of the ciliary epithelium are the internal non pigmented layer (representing the anterior extension of the neuroretina) and the external pigmented layer (representing the RPE). The ciliary processes produce the aqueous.

2. Pars plana – 4 mm ; flattened posterior zone

The ciliary muscle is composed of longitudinal, circular and radial fibers.

1. Circular fibers: contraction and relaxation of the zonular fibers alters the capsule of the lens thus giving variable focus for far and near objects of fixation.

2. Longitudinal fibers : insert to the trabecular meshwork, influencing its pore size 3. Radial fibers

The blood supply of the ciliary body is from the major circle of the iris and the nerve supply is from the ciliary nerves.

(12)

Fig 5. Vascu;lar supply of the eye

C. CHOROID

The choroid is the posterior portion of the uveal tract, located between the retina and the sclera. The internal portion of the choroidal vessels is called the choriocapillaries. Blood from the choroidal vessels drain via 4 vortex veins, one in each posterior quadrant. The choroid nourishes the outer portion of the retina.

Fig 6. Cross section of the choroid

7. LENS

The lens is a biconvex, avascular clear structure, 4 mm thick and 9 mm in diameter. It is suspended behind the iris by the zonules which connects it with the ciliary body. Anterior to the lens is the aqueous and posterior to it is the vitreous.

The lens capsule is a semi-permeable membrane (to water and electrolytes). A subcapsular epithelium is present anteriorly. The lens nucleus is harder than the cortex. With age, the subepithelial lamellar fibers are continuously produced, gradually making the lens larger and less elastic.

(13)

The lens consists of 65 % water and 35% protein and minerals. There are no blood vessels, pain fibers of nerves in the lens.

Fig. 7. Magnified view of a section of the lens showing lens capsule and epithelium

8. AQUEOUS

The aqueous is a clear fluid that fills the anterior and posterior chambers of the eye. Its volume is about 230 µL and its rate of production which is subject to diurnal variation is 2.5 µL/ min. Its composition is similar to plasma except for higher concentration of ascorbate, pyruvate and lactate and lower concentrations of protein, urea and glucose.

Aqueous is produced by the ciliary epithelium. From the posterior chamber, the aqueous pass through the pupil to go to the anterior chamber and then to the trabecular meshwork, to the Schelemm’s canal and into the venous system. Some aqueous passes between the bundles of the ciliary body and through the sclera (uveoscleral pathway).

9. ANTERIOR CHAMBER ANGLE

The anterior chamber angle lies at the junction of the periphearal cornea and the root of the iris. Its main anatomic features are Schwalbe’s line, trabecular meshwork ( which overlies the Schlemms’s canal) and the scleral spur.

The Schwalbe’s line corresponds to the termination of the corneal endothelium. The trabecular meshwork is triangular in cross section with the base directed to the ciliary body. I is composed of perforated sheets of collagen and elastic tissue with decreasing pore size as the canal of Schlemm is approached. The longitudinal muscles of the ciliary body insert into the trabecular meshwork. The scleral spur is an inward extension of the sclera between the ciliary body and the Schlemm’s canal, to which the ciliary body and the iris are attached.

(14)

Fig 8. Anterior chamber angle

10. RETINA

The retina is a thin, semi-transparent, multilayered sheet of neural tissue that lines the inner aspect of the posterior 2/3 of the wall of the eye. It extends anteriorly as the ora serrata. The outer surface of the retina is apposed to the retinal pigment epithelium (RPE). Except at the disc and the ora serrata, the retina and RPE are easily separated to form a subretinal space, such as occurs in retinal detachment. The inner layer of the retina is apposed to the vitreous

The 10 layers of the retina, from the inner aspect are the following: 1. internal limiting membrane

2. nerve fiber layer – ganglion cell axons passing to the optic nerve 3. ganglion cell layer

4. inner plexiform layer – connections of the ganglion cells with the amacrine and bipolar cells 5. inner nuclear layer – cell bodies of the bipolar, amacrine and horizontal cells

6. outer plexiform layer – connections of the bipolar and horizontal cells with the photoreceptors 7. outer nuclear layer – cell nuclei of photoreceptors

8. external limiting membrane

9. phototreceptor layer – rod and cones inner and outer segments

10. retinal pigment epithelium (RPE) – The inner layer of the Bruch’s membranes is actually the basement membrane of the RPE

The retina is 0.1 mm thick at the ora serrata and 0.56 mm thick at the posterior pole. In the center of the posterior retina is the macula. It is clinically seen as a 3 mm area of yellowish pigmentation (due to xanthophylls pigments) and bounded by the temporal vascular arcades. In the center of the macula is the fovea, clinically seen as a depression and corresponds to the “foveal reflex”. It corresponds to the retinal avascular zone of fluorescein angiography. Histologically, the fovea is characterized by thinning of the outer nuclear layer and the absence of the other parenchymal layers. The foveola is the most central portion of the fovea, in which the photoreceptors are all cones, and the thinnest part of the retina. All these histologic features provide for fine visual discrimination. The normally empty extracellular space of the retina is potentially greatest at the macula, and diseases that can lead to accumulation of fluid causes thickening of this area.

(15)

Fig 9. Layers of the retina

The retina receives its blood supply from

1. choriocapillaries – supply outer third of retina, from outer plexiform layer to RPE 2. central retinal artery – supply the inner 2/3 of the retina

The fovea is supplied entirely by the choriocapillaries and is susceptible to irreparable damage when the macula is detached. The retinal blood vessels have a nonfenestrated endothelium, which forms the inner blood-retinal barrier. The endothelium of the choroidal vessels is fenestrated. The outer blood-retinal barrier lies at the level of the RPE.

Fig 10. Macula

(16)

Fig 11. Histophotograph of the retina at the area of the macula

Fig 12. Diagram of the layers of the retina in the area of the macula

11. VITREOUS

The vitreous is a clear, avascular body, comprising 2/3 of the volume and weight of the eye. It fills the space bounded by the lens, retina and optic disc. The hyaloid membrane, the outer surface of the vitreous is in contact with the posterior lens capsule, zonules, pars plana epithelium, retina and optic nerve head. The base of the vitreous maintains a firm attachment through out life with the pars plana epithelium and the retina immediately behing the ora serrata. The attachment to the lens capsule and the optic nerve head is firm early in life but soon disappears.

The vitreous is 99% water. Collagen and hyaluronic acid makes the vitreous gel like because of their ability to bind large amounts of water.

EXTRAOCULAR MUSCLES

The 4 recti muscles originate from the annulus of Zinn at the apex of the orbit and are named after their insertion at the sclera on the medial, lateral, superior and inferior aspect of the eye. The superior oblique is the longest and thinnest of the extraocular muscles. The inferior oblique originates from the nasal side of the orbital wall and is the only extraocular muscle that does not originate from the apex of the orbit. Table 1

(17)

Muscle Origin Insertion Direction of pull

Action from Primary

Position Cranial NerveInnervation

Medial rectus

(MR) Annulus of Zinn 5.5 mm from medial limbus 90 ° Adduction III Lateral rectus

(LR) Annulus of Zinn 6.9 mm from lateral limbus 90° Abduction VI Superior rectus

(SR) Annulus of Zinn 7.7 mm from superior limbus 23° Elevation Intorsion Adduction

III Inferior rectus

(IR) Annulus of Zinn 6.5 mm from inferior limbus 23° Depression Extorsion Adduction

III Superior oblique

(SO) Orbit apex above Annulus of Zinn (functional origin at trochlea) Posterior equator at superotemporal quadrant 51° Intorsion Depression Abduction IV Inferior oblique

(IO) Behind lacrimal fossa Posterior to the equator in infero-temporal quadrant

51° Extorsion Elevation Abduction

III

Table 1. Extraocular Muscles

Fig 13. Spiral of Tillaux, showing the insertion of the recti muscles to the sclera

The blood supply to the extraocular muscles is from the musclular branchs of the ophthalmic artery. The lateral retus and inferior obliques are also supplied by the branches from the lacrimal artery and infraorbital artery respectively.

OCULAR ADNEXA 1. EYEBROWS

The eyebrows are folds of thickened skin covered with hair. The glabella is the hairless prominence in between the eyebrows.

(18)

2. EYELIDS

The upper and lower lids (palpebrae) are folds of skin that can close to protect the anterior portion of the eye. Blinking helps spread the tear film, keeping the cornea and conjunctiva wet.

Layers of the eyelids

1. Skin – thin, loose, elastic, few hair follicles and no subcutaneous fat.

2. Orbicularis oculi muscle – Circular muscle fibers surround the palpebral fissure which functions to close the eyelids. It is innervated by the facial nerve.

3. Areolar tissue – under the orbicularis oculi, communicates with the subaponeurotic layer of the scalp. 4. Tarsal plates – dense fibrous tissue layer ; main support of the eyelids

5. Palpebral conjunctiva – adheres firmly to tarsal plate

Lid Margin – free lid margin is 25-30 mm long and 2 mm wide. It is divided by the gray line (mucocutaneous junction) into anterior and posterior margin.

1. Anterior margin a. Eyelashes

b. Glands of Zeis – modified sebaceous glands ; open onto hair follicles at the base of eyelashes

c. Glands of Moll – modifies sweat glands ; open in a row near the base of the eyelashes 2. Posterior margin – in close contact with the globe ; along margins are the small orifices of the

meobomian glands (modified sebaceous glands)

3. Lacrimal punctum – at the medial end of posterior margin of the lid ; small elevation with a central opening ; carry tears through the canaliculus to the lacrimal sac.

Fig 14. Lid margin, medial portion of the eyelids

(19)

Fig 15. Cross-section of the eyelids

4. ORBITAL SEPTUM

The orbital septum is the fascia behind the portion of the orbicularis muscle that lies between the orbital rim and the tarsus. It serves as a barrier between the lid and the orbit

5. LID RETRACTORS

The lid retractors are responsible for opening the eyelids; have striated and smooth muscle components A. Upper lid

1. Levator palpebrae superioris

2. Muller’s muscle (superior tarsal muscle) B. Lower lid

1. Inferior rectus muscle 2. Inferior tarsal muscle 6. LACRIMAL COMPLEX

A. Lacrimal gland ; has orbital portion and palpebral portion

B. Accessory lacrimal glands of Krause and Wolfring – located in the sustantia propria of palpebral conjunctiva

C. Canaliculi D. Lacrimal sac

E. Nasolacrimal duct- drains out to the nasal cavity

Blood supply of the lacrimal gland is from the lacrimal artery and venous blood drain to ophthalmic vein. Lymphatics drain into preauricular lymph nodes.

Nerve supply to the lacrimal gland is by

a. lacrimal nerve (sensory), a branch of the trigeminal first division b. great superficial petrosal nerve (secretory)

(20)

Fig .16. Lacrimal drainage system

OPTIC NERVE

The trunk of the optic nerve consists of about 1 million axons arising from the ganglion cells of the retina a. intraocular portion – optic nerve head ; 1.5 mm in diameter

b. orbital portion – 3 mm in diameter, 25-30 mm long, located within the muscle cone c. intracanalicular portion – 4-9 mm long

d. intracranial portion- 10 mm long, and with the opposite optic nerve joins to from optic chiasm

Fig 17. Optic nerve

Fibers of the optic nerve consist of

a. visual fibers – 80%, synapse in the lateral geniculate body on neurons whose axons terminate in the visual cortex of the occipital lobe

b. pupillary fibers – 20% , bypass the geniculate body en route to the pretectal area.

The ganglion cells of the retina and their axons are part of the central nervous system and as such, do not regenerate if severed.

(21)

The surface layer of the optic disc receives blood from the branches of the retinal arterioles. The rest of the nerve in front of the lamina cribrosa is from the peripaillary choroidal vessels. At the region of the lamina cribrosa, the blood supply is from the short posterior ciliary arteries. Retrolaminar nerve receive blood from branches of the central retinal artery. The rest of the introrbital portion, intracnalicular and intracranial portions are supplied by pial vessels from branches of ophthalmic artery and other branches of the internal carotid artery.

Fig 18. Cross-section of the optic nerve

(22)

SUMMARY

An understanding of the anatomy of the eye, ocular adnexae, orbit, visual pathways and the cranial nerves is important in the proper diagnosis of ocular diseases and other disorders with ocular manifestations.

REFERENCES

1. Duane, Thomas and Jaeger, Edward . Clinical Ophthalmology, Philadelphia : Harper and Row , latest edition

2. Riordan-Eva, Whitcher, John. Vaughn and Ashbury’s General Ophthalmology , 16th_{Edition, New York:}

Lange Medical Books/ McGraw Hill, 2004

3. Scheie, Harold, Albert, Daniel. Textbook of Ophthalmology, Philadelphia : W.B. Saunders Co, latest edition

4. Selected images from the lecture of Leonardo Mangubat, Anatomy of the Eye and Adnexae, SELF-TEST

1. Decrease in aqueous production can best be achieved by destruction of which part of the eye? A. Pars plicata

B. Choroid C. Iris D. Pars plana

2. Which one of the following rectus muscle tendons inserts on the sclera farthest from the corneal limbus? A. superior rectus

B. inferior rectus C. medial rectus D. lateral rectus

3. The levator palpebrae is innervated by what nerve A. III

B. IV C. V D. VII

4. The following structures are part of the medial orbital wall, EXCEPT A. ethmoid bone

B. lacrimal bone C. maxillary bone D. sphenoid bone

5.What layer of the retina does the the choriocapillary supply with oxygen? A. ganglion cell layer

B. nerve fiber layer C. photoreceptors D. inner nuclear layer

(23)

6.Which of the following statements regarding the cornea is FALSE ?

A. The corneal endothelium is important in maintaining corneal dehydration. B. The water content of the cornea is less than that of the sclera.

C. Normal central corneal thickness is 1.00 mm

D. Corneal diameter is greater horizontally than vertically. 7. Which is not a layer of the eyelid ?

A. Skin B. Conjunctiva C. Tenon’s capsule D. Orbicularis muscle E. Tarsus

8.The following structures must maintain their clarity in order good vision EXCEPT A. Cornea

B. aqueous C. lens D. vitreous E. choroid

9. The optic nerve consists of axons from what cells in the retina? A. amacrine cells

B. bipolar cells C. ganglion cells D. photoreceptor cells 10. Which muscle is an adductor?

A. medial rectus B. lateral rectus C. superior oblique D. inferior oblique ANSWERS TO SELF-TEST 1. A 2. A 3. A 4. D 5. C 6. C 7. C 8. E 9. C 10. A .

(24)

P

H

Y

S

I

O

L

O

G

Y

O

F

T

H

E

Y

E

Richard C. Kho, M.D.

INTRODUCTION

This self-instructional material (SIM) is designed to help the medical student acquire an overview of the biophysical elements at work within (and outside) the human eye, for the latter to function as a sense organ subserving vision. Understanding basic concepts of light energy, its “transformation” in the human eye, its conversion to nerve impulses and eventual visual perception, is a pre-requisite to effective diagnosis and subsequent management of eye diseases.

OBJECTIVES

Upon completion of this SIM, the student should be able to discuss the following :: 1. The physical properties of light

2. The processes involved as soon as light strikes the human eye

3. The internal bending of light as it focuses on the retina, i.e., optics and refraction in the human eye 4. Retinal processes which transform light energy that result in visual perception

5. Basic neuro-anatomic architecture of the visual pathway, as well as topographical localization of lesions

PREREQUISITE KNOWLEDGE AND PREPARATION

Students should have a working knowledge of the basic anatomy of the human eye. A general knowledge of the neuro-anatomy of the afferent visual pathways would likewise be useful.

INTENDED USERS

This SIM was prepared for the medical student just embarking on the study of the anatomy and physiology of the human eye. It does not aim to supplant ophthalmology textbooks which provide a more detailed discussion of advanced concepts in optics and refraction, retinal physiology, and neuro-ophthalmology.

CONTENT

This module is divided into two parts:

PART I: The Eye as an Optical Instrument A. Physical Optics

-The physical properties of light

B. Geometric Optics

-The process in which external light energy is focused on the retina

PART II: The Eye as a Sense Organ C. Physiologic Optics

-The biochemical and functional processes that occur in the retina to produce visual energy

(25)

D. Psychologic Optics or Neuro-Ophthalmologic Optics

-The conduction of visual energy to the occipital visual center

PART I: The Eye as an Optical Instrument A. Physical Optics

Light is the basic stimulus for vision. This comprises only a small portion of the electromagnetic spectrum of energy:

Fig 1. The Electromagnetic Spectrum

This small portion, called the visible spectrum, is the ONLY portion of the spectrum that can stimulate the photoreceptors of the human retina. It extends from 380 micra (3800 angstrom units) to 760 micra (7600 angstrom units). Right after the UV spectrum (violet), the wavelength of each color increases as it moves toward the direction of infrared rays (red).

There are 3 Important Characteristics of Light:

1) Velocity or Speed

-3 X 1010_{cm/sec in vacuum; slower in clear air and in denser media.}

2) Wavelength

-size determines the color; with violet (380µ ) the shortest, and red (760µ ) the longest.

Fig 2. Wavelength

3) Frequency

-number of complete cycles moving past a specific point over a given period of time.

(26)

PART I: The Eye as an Optical Instrument B. Geometric Optics

This process, in-between physical optics and physiologic optics, comprise of events that occur from the moment light strikes the eye, and eventually gets focused on the retina. Its principal basis is the transmission and bending of the direction of travel of light rays, i.e., REFRACTION.

Refraction of Light

As light passes through a transparent solid or liquid media, it slows down depending on the density of the media. The relative unit of measurement of this capacity is called the index of refraction.

The Refractive Index (n) is a constant depending on the material; it determines the angle of deviation. air = 1.0

water = 1.33 glass > 1.40

It is simply a relative unit compared to air.

As light passes from one medium to another of a different index of refraction and at a certain angle, there is bending of light, i.e. light is Refracted.

Fig 3. Refraction of Light

Prism

Any media whose 2 sides are not parallel will refract light rays ---- light is deviated towards the base of the prism.

apex

light source

base

(27)

Basis of Lenses

Lenses can be viewed as a certain arrangement of prisms (remember that light is deflected towards the base of the prism). A converging lens (positive lens) can be thought of as two prisms joined at the base, while a diverging lens (negative lens) can be thought of as two prisms joined at the apex.

converging diverging

Fig 5. Converging and Diverging Lenses

Power of the Lens

A Diopter is a unit of measurement of lens power. It is a measure of convergence or divergence, and a reciprocal of focal distance. The power of the lens depends on its curvature and the difference in refractive indices.

The Eye

Can be thought of as a series of lenses whose main goal is to focus light rays from the external world unto the retina:

–

cornea

–

aqueous

–

lens

–

vitreous

The average human eye has a total converging power of about 60 diopters. The main refractive components are as follows:

Cornea ~ +40 Diopters Lens ~ +20 Diopters

Emmetropia is a condition wherein parallel light rays fall into a pinpoint focus on the retina.

(28)

Ammetropia is a condition wherein parallel light rays DO NOT fall into a pinpoint focus on the retina:

•

Myopia

•

Hyperopia

•

Astigmatism

Myopia, commonly known as “nearsightedness”, is a condition wherein parallel light rays focus at a point in front of the retina. It can be axial (eyeball longer than average) or refractive (corneal curvature steeper than average).

Fig 7. Myopia: Light is focused IN FRONT OF the retina

To Correct Myopia, one would need a divergent lens (“negative” or biconcave lens to neutralize the convergent effect of the myopic eye) in order to focus light rays on the retina.

Fig 8. A Negative Lens “pushes back” the image unto the retina

Hyperopia, commonly known as “farsightedness”, is a condition wherein parallel light rays focus at a point behind the retina. It can be axial (eyeball shorter than average) or refractive (corneal curvature flatter than average).

(29)

To Correct Hyperopia, one would need a convergent lens (“positive” or biconvex lens) in order to focus light rays on the retina.

Fig 10. A Positive Lens “pulls frontward” the image unto the retina

Astigma ism is a condition wherein the curvature of the cornea or of the lens is not the same in different meridians. Here, parallel light rays focus on 2 separate lines or planes. One can imagine that the curvature of the eye in astigmatism resembles one side of a football, instead of a basketball (in eyes without astigmatism). To correct astigmatism, one would need cylindrical lenses (lenses each with power in two different meridians/axes)

t

spherical astigmatic

Fig 11.The front curvature of two different balls illustrate the difference in the curvature of spherical corneas (basketball) vs. astigmatic corneas (football).

Types of Astigmatism:

1. Simple Myopic - one image on the retina, one image in front of the retina 2. Simple Hyperopic - one image on the retina, one image behind the retina 3. Compound Myopic - both images in front of the retina

4. Compound Hyperopic - both images at the back of the retina

5. Mixed Astigmatism - one image in front of the retina, one image at the back of the retina Correction of Ammetropia:

1. Spectacles 2. Contact lenses

• soft, rigid gas permeable, hard, etc. • multifocal

3. Refractive Surgery

• PRK (photorefractive keratectomy) • RK (radial keratotomy)

• LASIK (laser-assisted in situ keratomilieusis) Principle of Accommodation

To focus on a nearby object, the brain sends out signals to contract the smooth muscles of the ciliary body; this enables the zonules to loosen up, which in turn increases the lens curvature (lens thickens), and thereby increasing its converging power.

Presbyopia

With aging (around 40 years old), there is loss of focusing or accommodative power of the human eye. One would need “plus lenses” (presbyopic glasses/reading adds) to make up for the lost automatic focusing power of the lens.

(30)

The Human Retina is a thin, semi-transparent, multilayered sheet of neural tissue that lines the inner aspect of the posterior 2/3 of the wall of the globe. The young, adult retina contains approximately 120 million rods, and about 6million cones.

Fig 12. Layers of the Human Retina

The human retina is capable of perceiving the following visual senses:

•

Light sense

•

Form sense

•

Color sense

Light Sense: The Role of Visual Pigments

For the eye to perceive light, the latter has to be converted into the biochemical energy of the visual nerve impulse. First, it must be absorbed by the visual pigments located at the outer segments of the rods and cones. These visual pigments (rhodopsin, Iodopsin, etc.) are lipid-protein complexes of a fat-soluble aldehyde of Vitamin A, plus a protein called opsin.

Vitamin A occurs only in animal tissue. A molecule of its precursor (beta-carotene) derived from plants, is split into two to form molecules of Vitamin A in the form of an alcohol. Vitamin A occurs in two forms (isomers), a cis-retinal and a trans-retinal structure. Only the cis-retinal isomer combines with opsin to form rhodopsin.

Photochem s ry of V sion i t i

When light strikes rhodopsin, it is split into cis-retinal (cis-retinene) and opsin after passing through a series of orange intermediate compounds (lumirhodopsin, metarhodopsin, etc).

Two major events occur with the split of rhodopsin:

1) A sudden reduction of sodium influx through the photoreceptor plasma membrane together with increased permeability of the membrane to calcium ions result in a relative hyperpolarization of the plasma

(31)

2) The transformation of cis-retinene to trans-retinene releases energy.

Trans-retinal is reconverted to cis-retinal by the action of the retinene isomeraze enzyme with energy provided by the DPNH2-DPN dehydrogenase system. Cis-retinal, as soon as it is formed combines with opsin to form the stable product rhodopsin. This combination also releases energy which is utilized in the oxidation of retinol (Vit A-alcohol) to retinal (Vit A-aldehyde or retinene).

Fig 13. The Photochemistry of Vision

Form Sense: Visual Acuity

Form sense discriminates between stimuli, i.e., to see two stimuli separately as two instead of fusing them into one. It determines the acuity of vision. Simply put, it is the minimum amount of separation between two light sources at a given distance from the eye so that they can still be seen as two. These two lights subserve an angle at the nodal point of the eye called the minimum visual angle.

i

Minimum V sual Angle

Experimentally, the smallest detectable line subtends one minute of arc.

Fig 14. Minimum Visual Angle

• The big “E” on the Snellen Chart subtends an angle of 5 minutes

Fig 15. The Snellen E and its corresponding visual angles.

(32)

Testing Visual Acuity using the Snellen Chart

•

Letters are constructed so that they subtend the same visual angle when viewed at distances of up to 200ft

Fig 16. Construction of the Snellen Chart for consistency

One usually measures visual acuity at 20ft (6m) and is recorded as two numbers: The numerator represents the distance between chart and patient, while the denominator represents the smallest row of letters that the patient’s eye can read. For example, a visual acuity of 20/40 simply means that the patient’s eye can only read from 20 ft, what a normal (emmetropic) eye can read at 40ft.

E

_{20/200 6/60}

Feet Meters

20/100 6/30

20/70 6/21

20/50 6/15

20/40 6/12

20/30 6/9

20/25 6/7.5

20/20 6/6

F

P

T O Z

L P E D

P E C F D

E D F C Z P

F E L O P Z D

D E F P O T E C

Fig 17 and Table 1. Recording Visual Acuity Using the Snellen Chart

Color Sense: A Function of the Cone Photoreceptors

White light or sunlight is a composite of different colors corresponding to each wavelength in the visible spectrum.

(33)

Color Blindness

“Color blindness” occurs in about 10% of all males and about 1% of all females. It has a sex-linked, recessive pattern of inheritance. True color blindness (total absence of one type of photo pigment or color-sensitive cone) is rare. Most of the time, all photo pigments are present except for a relative deficiency of one color----an “anomaly”.

• In Trichromats, all 3 colors are present but has a relative deficiency in one.

–

Deuteranomalous (green anomaly)

–

Protanomalous (red anomaly)

–

Trianomalous (blue anomaly)

• In Dichromats, there is total loss of one color pigment

–

Deuteranopes (no green)

–

Protanopes (no red)

–

Trianopes (no blue)

• Monochromats or Cone Monochromats (atypical) have only one color pigment • Achromats or Rod Monochromat (typical) are totally color blind.

PART II: The Eye as a Sense Organ D. Neuro-ophthalmic Optics

Basic Concepts

Monocular vision, seen in lower vertebrates, is a less-advanced form of visual function wherein visual impressions from one side cross-over to the contralateral cerebral cortex completely (there is complete decussation).

Fig 19. Visual Pathway in Monocular Vision

In Binocular vision, there is nasal (partial) decussation of fibers from the two sides. As a result, both retinas send the same visual impressions to the visual cortex.

(34)

Fig 20. Visual Pathway in Binocular Vision

Stereopsis or depth perception is possible only with binocular vision Neuro-anatomic Pathways

These are structures which perceive, relay, and process visual information.

From the external world, all the way to its end terminal, the following are its components:

• Eye (retina)

• Optic Nerve (CN II)

• Chiasm

• Optic Tract

• LateralGeniculate Nucleus

(LGN)

• Optic Radiation

• Striate Cortex

Fig 21. The Afferent Visual Pathway

Note that the visual field and the retina are optically inverted, i.e., the right visual fields (both the right field of right eye and the right field of left eye) are projected to the left hemi-retina of both eyes and, retro-chiasmally, the left visual pathway until its termination in the left occipital lobe. Vertically, visual field and retinal projections follow a similar pattern of optical inversion. In addition, there is direct one-to-one correspondence between visual direction in space and retinal location. This retino-topic organization is preserved throughout the entire visual pathway, and this logical architecture is the basis for localization of

(35)

Understanding the neuro-anatomy of the visual pathway is the key to effective evaluation, localization, and eventual diagnosis of many intracranial lesions.

Fig 22. Location of lesion with corresponding visual field defects

A. left optic nerve – central scotoma/generalized depression of the left eye B. optic chiasm- bitemporal hemianopia

C. left optic chiasm (lateral aspect)- left nasal hemianopia D. left optic tract- Right Homonymous Hemianopia

E. left optic radiation (temporal lobe)- Right Superior Homonymous Quadrantanopia (“pie in the sky”) F. left optic radiation (parietal lobe)- Right Inferior Homonymous Quadrantanopia (“pie on the floor’) G. left occipital lobe (visual/striate cortex)- Right Homonymous Hemianopia

SUMMARY

•

PART I: The Eye as an Optical Instrument A. Physical Optics • 3 properties of light: 1) velocity 2) wavelength 3) frequency B. Geometric Optics • refractive index (n) • prisms

• lenses (converging and diverging) • emmetropia

(36)

o myopia o hyperopia o astigmatism simple myopic simple hyperopic compound myopic compound hyperopic mixed astigmatism • correction of ammetropia o spectacles o contact lenses o refractive surgery

•

• light sense: role of visual pigments o photochemistry of vision • form sense: visual acuity

o minimum visual angle

o testing visual acuity with the Snellen Chart • color sense: a function of photoreceptors

o color blindness Trichromat Dichromat Monochromat Achromat

D. Psychologic Optics or Neuro-Ophthalmologic Optics • monocular vision

• binocular vision

• neuroanatomy of the afferent visual pathway

o lesions and corresponding visual field defects

REFERENCES

1) Espiritu RB. Ophthalmologic Optics. Manila: Department of Ophthalmology and Visual Sciences-UP-PGH Medical Center; 2001.

2) Vaughan D, Asbury T, Riordan-Eva P, editors. General ophthalmology. 13th_{ed. Appleton and}

Lange; 1992.

3) Spalton DJ, Hitchings RA, Hunter PA, editors. Atlas of Clinical Ophthalmology. 2nd_{ed. London:}

Wolfe Publishing; 1994.

4) Goldberg S. Clinical Neuroanatomy Made Ridiculously Simple. Miami: Medmaster Inc; 1979. 5) DeMyer W. Technique Of The Neurologic Examination: A Programmed Text. 3rd_{ed. McGraw-Hill}

Book Company; 1980.

(37)

SELF TEST

1. In the visible spectrum, which of the following colors has the shortest wavelength? A. blue

B. green C. orange D. red

2. Which of the following happens to the velocity of light as it passes from a medium of higher refractive index, to one of lower refractive index?

A. slows down B. speeds up C. stays the same D. is dissipated

3. True or False? A diverging (negative) lens can be thought of as 2 prisms with the bases adjacent. 4. Which of the following structures accounts for the highest refractive omponent of the human eye?

A. lens B. cornea C. vitreous D. aqueous

5. Match the following refractive states in reference to the location of the image relative to the retina.

___A.. myopia 1. on the retina

___B.. hyperopia 2. in front of the retina ___C.. emmetropia 3. behind the retina 6. To correct astigmatism, one would need which type of lens?

A. diverging (negative) lens B. cylindrical lens

C. converging (positive) lens D. prisms

7. To correct hyperopia, one would need which lens? A. diverging (negative) lens

B. cylindrical lens

8. Which type of astigmatism has both images focused at the back of the retina? A. simple myopic

B. simple hyperopic C. compound myopic D. compound hyperopic E. mixed astigmatism

(38)

9. In presbyopia, one would need which type of lens to make up for the lost converging power of the human lens?

A. diverging (negative) lens B. cylindrical lens

10. Rhodopsin is formed by the combination of which molecules? A. opsin and beta-carotene

B. beta-carotene and Vit A alcohol C. cis-retinal isomer and opsin D. lumirhodopsin and metarhodopsin

11. Each arm (1/5 its total height) of the big “E” in the Snellen Chart subtends how much angle? A. 5 min

B. 1 min C. 10 min D. 20 min

12. True or False? In recording visual acuity, the numerator represents the distance between the chart and the patient.

13. Which condition is described as having total loss of red color? A. protanope

B. protanomaly C. deuteranope D. deeuteranomaly

14. A lesion of the optic chiasm would most likely present with which kind of visual field defects? A. binasal hemianopia

B. left homonymous hemianopia C. bitemporal hemianopia

D. left superior homonymous quadrantanopia

15. Which of the following lesions would most likely give rise to a left superior homonymous quadrantanopia?

A. left temporal lobe B. right temporal lobe C. left parietal lobe D. right parietal lobe

ANSWERS TO SELF-TEST 1) A 2) B 3) F 4) B 5) A-2, B-3, C-1 6) B 7) C 8) D 9) C 10) C 11) B 12) T 13) A 14) C 15) B

(39)

OCULAR SYMPTOMATOLOGY

Marissa N. Valbuena M.D., MHPEd

Arnold T. Salud M.D.

INTRODUCTION

One should have a good understanding of ocular symptomatology to be able to perform a complete ophthalmic evaluation/ examination, which in turn is necessary to come up with accurate diagnoses.

OBJECTIVES

Upon completion of this unit of instruction, the student should be able to 1. discuss the different ocular symptoms.

2. to be able to perform a good ocular history.

PREREQUISITE KNOWLEDGE AND PREPARATION

The student should have basic knowledge of the anatomy and physiology of the eye and adnexae. Skills in interviewing a patient will also be helpful.

INTENDED USERS

Although this material was developed to provide the medical students with knowledge on ocular symptomatology, this should be supplemented by small group learning directed to developing their skills in taking ocular history.

CONTENT

Ocular symptoms can be classified into three general types: 1. abnormalities of vision

2. abnormalities of ocular appearance

3. abnormalities of ocular sensation – pain and discomfort These symptoms should always be described according to

1. onset – gradual, rapid or asymptomatic

Example of asymptomatic onset is that the blurring of vision was discovered only when patient inadvertently covered one eye.

2. duration – brief, chronic

3. frequency – continuous, intermittent 4. degree – mild, moderate or severe

5. location – focal or diffuse, unilateral or bilateral

Determine if forms of treatment have already been initiated/tried. If so, to what extent have they helped to relieve the symptoms? Are there circumstances that provoke or worsen the condition? Is this the first time these symptoms are experienced? No associated other signs/symptoms?

(40)

1. ABNORMALITIES OF VISION

A. Visual Loss

Patients can describe visual loss as “nanlalabo”, “maulap ang panningin”, “nawawala ang

paningin” or “nabulag”

When a patient reports impairment of vision, the examiner should determine when it occurred, whether onset was sudden or gradual, whether one or both eyes were affected. If both eyes are involved, which is worse, which failed first and how much time has elapsed between the two.

Actual onset of visual impairment may not coincide with the time given by the patient. Vision in one eye may have been deteriorating over the years, becoming noticeable when the patient accidentally covered one eye.

One should distinguish between decreased central acuity and peripheral vision. Disturbances in peripheral vision may be focal such as scotoma, or may involve a bigger area as in hemianopsia. A scotoma is a blind or partially blind area in the visual field while hemianopsia is blindness in one-half of the visual field. Abnormalities in the central nervous visual pathway disturb the visual field more than the central visual acuity.

Is the visual loss transient or permanent? Transient loss of vision may be to vascular disorders anywhere from the retina to the occipital cortex.

Is the patient’s vision worse or better in some circumstances ? Patients with error of refraction may have better vision when they squint their eyes. Patients with presbyopia will read better if they position their reading material further away from their eyes. Patients with central focal cataracts may have worse vision in bright sunlight.

Decline in visual acuity may be due to abnormalities anywhere along the optical and neurologic pathway. Consider the following as possible causes:

1. refractive error 2. ptosis

3. ocular media disturbance (corneal edema, hyphema, cataract, vitreous hemorrhage)

4. retinal abnormalities 5. optic nerve diseases

6. intracranial visual pathway abnormalities

B. Visual Aberrations

1. GLARE, PHOTOPHOBIA

(41)

Irritative disease of the conjunctiva or cornea specially foreign bodies of the cornea may induce photophobia. Acute inflammation of the iris may likewise make the eye sensitive to ordinary light.

Glare may also result from uncorrected EOR, scratches on spectacle lenses, excessive pupillary dilatation, hazy ocular media

2. VISUAL DISTORTION

Manifests as irregular patterns of dimness, wavy or jagged lines, image magnification/ minification. May be caused by migraine, optical distortion from strong corrective lenses, lesions involving the macula and optic nerve.

3.FLASHING/FLICKERING LIGHTS

Patients may describe this as “may parang kidlat”, “biglang may maliwanag” May indicate retinal traction, or migrainous scintillations.

4.FLOATING SPOTS

“May lumulutang sa harap ng mata”

May represent normal vitreous strands due to “normal” vitreous changes.Or may be secondary to pathologic presence of pigments, blood, or inflammatory cells.

5.OSCILLOPSIA

“Gumagalaw o lumilikot and paningin”

Shaking field of vision may be due to harmless lid twitching (myokymia), or to certain forms of nystagmus

6. DOUBLE VISION

“Nagdadalawa ang paningin” “doble ang paningin”, naduduling”

Monocular diplopia manifests as a split shadow or ghost image. Causes include uncorrected error of refraction, media abnormalities such as cataract, corneal irregularities

Binocular diplopia disappears when one eye is covered may be vertical, horizontal, diagonal or torsional. The diplopia may be more severe ( 2 images more widely separated) in certain gazes or head position.

(42)

2 ABNORMALITIES OF APPEARANCE A. Red Eye

Must differentiate between redness of the lids and periocular area (ocular adnexa) from that of the globe. Preseptal cellutitis VS Conjunctivitis “namumula ang mata”, “sore eyes”

Orbital cellulits Subconjunctival hemorrhage “dumugo ang mata” “Namamaga ang mata” Scleritis

Iritis

Acute glaucoma Pterygium etc Color abnormalities other than redness

1. jaundice

2. hyperpigmented spots (on the iris/ocular surface) – examples are Nevus of Ota , subepithelial melanosis

B. Ptosis – drooping of the eyelids, “Napipikit”, “kirat ang mata” C. Focal growths – in the eyelids or eye surface , “bukol”, “maga” D. Exopthalmos – protrusion of the eyeball, “lumuluwa ang mata”

E. Ocular deviation or misalignlent – “duling”, “banlag” ; esodeviation (inward turning of the eye), exodeviation (outward turning of the eye), hypertropia (upward turning of the eye) or hypotropia (downward turning of the eye)

3. ABNORMALITIES OF OCULAR SENSATION A. Eye Pain

“Masakit”, “makirot”, “mahapdi”

Must be characterized in terms of location:

1. periocular (may be tenderness of the lid, tear sac, sinuses or temporal artery) 2. retrobulbar (due to orbital inflammation, orbital myositis, optic neuritis)

3. ocular (may be due to corneal abrasion, corneal foreign body, glaucoma, endophthalmitis) 4. non-specific (fatigue from ocular accommodation, binocular fusion, or referred discomfort from

non-ocular tension or fatigue)

Deep seated aching, boring or throbbing pain may be may be due to inflammation of the iris and ciliary body. Orbital infection can give rise to severe pain. Herpez zoster may give pain in the eye before any visible involvement of the eye and may persist after the disease has resolved.

Tenderness, soreness or pain on pressure may be due to inflammation of the lids, corneal foreign body or any anterior segment inflammation.

B. Eye Irritation

(43)

2. Dryness – Burning, gritty, mild foreign body sensation. Can occur with dry eyes or other types of mild corneal irritation, “may buhangin”, “maaligasgas”

3. Tearing – may be due to irritation of the ocular surface; or may be a sign of abnormal lacrimal

drainage , “nagluluha”

4. Ocular Secretions – “nagmumuta”, Characretize discharge as to color, consistency, amount a Mucoid discharge – allergic

b Mucopurulent – bacterial/viral conjunctivitis c Dried matter/crusts on lashes – Blepharitis C. Headache

Uncorrected errors of refraction and presbyopia frequently cause headache referred to the eyes or brow and comes with reading and computer work. Migraine headaches and sinusitis are frequent causes of headache. Headaches may not come from the eye. High and low blood pressure may also give rise to headaches around the eyes. Headache from rise in intracranial pressure is usually severe and associated with nausea and vomiting.

SUMMARY

Ocular symptoms consist of abnormalities in vision, appearance and sensation. The student should ask clarifying questions in order to get sufficient detail to pinpoint the etiology of the ocular disorder.

REFERENCE

1. Riordan-Eva, Whitcher, John. Vaughn and Ashbury’s General Ophthalmology , 16th_{Edition, New York:}

Lange Medical Books/ McGraw Hill, 2004

2. Scheie, Harold, Albert, Daniel. Textbook of Ophthalmology. Philadelpia : W.B Saunders LEARNING ACTIVITY

Students should pair and role play. One will be the doctor and the other the patient. The doctor should take the history of the patient with any of the following chief complaint :

1. “Malabo ang mata” 2. “may sore eyes” 3. “mahapdi ang mata” 4. “banlag”

The “doctor” will write the patient’s history and the partner will comment on the completeness and accuracy of the history.

(44)

BASIC EYE EXAMINATION

Teresita R. Castillo, MD, MHPEd

INTRODUCTION

This self-instructional material is designed to help the student learn important concepts on proper eye examination. It will explain how to examine the eye and basic visual function.

The proper method of basic eye examination in an individual is an important skill that every physician should possess. Performing a systematic eye examination will enable the physician to evaluate ocular complaints and subsequently provide immediate emergency care whenever the need arises. Furthermore, this will enable the physician to recognize ocular conditions that may require further referral to an ophthalmologist for definitive management. An eye examination may also provide the physician with information on the status or condition of certain systemic diseases such as diabetes, hypertension and thyroid diseases.

OBJECTIVES

Upon completion of this unit of instruction, the student should be able to discuss the principles of performing the basic eye examination. Specifically, he/she should be able to

1. discuss the value and rationale of the various parts of the basic eye examination 2. determine a patient’s visual acuity

3. assess the pupillary reflexes 4. evaluate ocular motility

5. determine intraocular pressure

6. perform direct ophthalmoscopy for a systematic fundus examination 7. record the results of the eye examination properly and accurately

PREREQUISITE KNOWLEDGE AND PREPARATION

Students should have a working knowledge of the basic anatomy of the eye and its adnexa. It is advised that this written material be completed first prior to performance of the eye examination on an actual patient. The students should likewise familiarize themselves with the basic eye instruments utilized in examining the eye. These include distance and near vision eye charts, penlight, tonometer and the direct ophthalmoscope.

INTENDED USERS

Although this material was developed to provide the medical student with the principles of each area of the eye examination, this should be supplemented by small group

sessions directed at actual performance of these skills.

CONTENT

All patients should have an eye examination as part of a general physical examination. Visual acuity, gross examination of the eye and its adnexae, extraocular muscle

(45)

movements, intraocular pressure determination and fundus examination using the direct ophthalmoscope constitute the basic eye examination. These will be discussed individually.

VISUAL ACUITY TESTING

Measurement of the visual acuity provides clinicians with a standard tool for reporting and recording a patient’s vision. Standard notations used for recording of visual acuity are shown in Table 1.

Table 1. Notations used in Recording Visual Acuity VA visual acuity

OD (oculus dexter) Right eye OS (oculus sinister) Left eye OU (oculus uterique) Both eyes sc without correction cc with correction

ph pinhole NV near vision DISTANCE VISUAL ACUITY

Distance visual acuity measurement should be performed in all patients, including children because of the importance of early detection of amblyopia. Determination of visual acuity is done prior to any manipulation of the eye to avoid any medico-legal issues that may arise in the future.

Distance visual acuity is recorded as a ratio or fraction which compares the performance of the patient with an agreed upon standard.

VA = distance from the patient to the chart __ distance at which normal eye can read the given line Example:

VA = 20/40 indicates that the patient can recognize at 20 ft, a symbol that can be recognized by a person with normal visual acuity at 40 ft.

Visual acuity of 20/20 represents normal vision. Alternative notations are shown in Table 2.