POSTERIOR POLYMORPHOUS DYSTROPHY AND LASIK

POSTERIOR POLYMORPHOUS DYSTROPHY AND LASIK

DISTROFIA POLIMORFA POSTERIOR Y LASIK

HUERVA V1_{, MATEO AJ}2

Received: 5/3/07. Accepted: 2/9/08.

1_{Ph.D. in Medicine. Arnau de Vilanova University Hospital.}

2_{Ph.D. in Medicine. Lozano Blesa University Clinical Hospital. Zaragoza.}

Correspondence: Valentín Huerva C/. Río Ara, 20 22520 Fraga (Huesca) Spain E-mail: vhuerva@mixmail.com

RESUMEN

Objetivo/Método:Mujer hipermétrope de 50 años desea información sobre cirugía refractiva. En la córnea se aprecia vesículas y bandas en la membra-na de Descement y endotelio catalogándose de dis-trofia polimorfa posterior (DPP). El recuento endo-telial resulta bajo por lo que se le contraindica cual-quier cirugía refractiva corneal.

Resultados/Conclusiones:La presencia de vesícu-las y bandas a nivel de la membrana de Descement y endotelio es característico de una DPP. En estos casos resulta obligatorio realizar una microscopía especular previa a una cirugía refractiva con láser excimer. Un recuento de células endoteliales bajo puede constituir una contraindicación para el LASIK hipermetrópico en casos de DDP por el posible riesgo de descompensación endotelial.

Palabras clave:Distrofia polimorfa posterior, PPD, distrofias corneales posteriores, distrofia endotelial de Fuchs, LASIK, hipermetropía.

ABSTRACT

Objective/Method:A 50-year-old hyperopic woman requested information about refractive surgery. Vesi-cle and band lesions at Descemet’s membrane and endothelium were suggestive of posterior polymorp-hous dystrophy (PPD). Lower than normal endothe-lial cell densities were detected. A corneal refractive procedure was not recommended in this case.

Results/Conclusions:The presence of vesicles and bands at Descemet’s membrane and endothelium is suggestive of PPD. Specular microscopy is manda-tory in such patients, although corneal decompensa-tion is not evident. A low endothelial cell count may be a contraindication for a hyperopic LASIK proce-dure in cases of PPD because of the possible risk of corneal decompensation (Arch Soc Esp Oftalmol 2008; 83: 607-614).

Key words: Posterior Polymorphous Dystrophy, PPD, posterior corneal dystrophies, Fuchs corneal dystrophy, LASIK, hyperopia.

INTRODUCTION

Posterior Polymorphous Dystrophy (PPD) is one of the posterior corneal dystrophies together with Fuchs’ dystrophy and congenital hereditary dystro-phy (CHED) (1,2). PPD is a dominant autosomal hereditary disease (1,2) and its typical lesions involve Descemet’s membrane and the

endotheli-um, although it exhibits a high degree of variability. Less frequently, the disease develops with corneal edema, peripheral anterior synechiae and endothe-lial guttae (1,2). The majority of patients do not exhibit symptoms and the diagnostic arises during an exploration for other reasons. Rarely do they require keratoplasty due to corneal decompensa-tion. When associated to a refractive defect and

A 50 year-old woman without relevant history or known eye diseases who visits the practice due to hyperopic refractive defect. She expresses an inter-est in refractive surgery and requinter-ests information. The subjective examination of refraction and visual acuity was as follows: Right eye (RE): 20º –0.75+2.25 = 10/10, left eye (LE): 30º –1.75+3 = 0.7, requiring the addition of 2 dioptres for near vision in both eyes. Under cyclopegy the refractive defect was in RE: 20º –0.50 + 2.50 and in LE: 30º –1.75 + 4. The patient did not refer having used contact lenses in the past. Figures 1 and 2 show the results of corneal topography and pachymetry. The biomicroscopic study showed a high number of vesicles at the endothelial level, as well as band-shaped images which were more acute in the left eye (fig. 3). The existence of this polymorphism at the posterior corneal level was suggestive of a PPD. IOP and eye fundus were normal. To decide whether the patient could undergo refractive surgery, a broad field mirror microscopy was made on the corneal endothelium to assess the endothelial

The clinical expression of PPD varies consider-ably, from isolated endothelial lesions to corneal decompensation, anterior synechiae and glaucoma in members of the same family (1,2,4). The disease is bilateral but asymmetric. In the majority of cas-es it is non-symptomatic and is diagnosed in a rou-tine exploration (1) as in the instant case. It usual-ly appears between the second and third decade of life, developing at the endothelial level and Descemet membrane. It can be divided in three pat-terns: vesicular lesions, band lesions and diffuse opacities (1). The main lesions of PPD are vesicles, which arise in isolation in 42% of cases and 48% in combination with bands (1,4). Only 10% of cases are associated to diffuse opacities (1,4). Vesicles are described as vacuolar, nodular, annular or crater lesions, transparent and surrounded by a whitish-grayish halo (1,2). The lesions can attain a variety of sizes and appear in isolation or in groups, as well as gather in form of bands (1,2). There are no data about the prevalence of the dis-ease. The fact that it does not exhibit symptoms suggests that many vesicles may go unnoticed in a

Table I.

Endothelial alterations after excimer laser corneal refractive surgery

Authors

Refractive defect

Prevous endothelial

Corneal refractive

Follow-up

Results in endothelial density

dystrophia procedure Amano S et al. Myopia PRK 12 months

Without alterations in cellular density

Am J Opthalmol 1993; 116: 692-94

Pérez-Santonja JJ

Myopia

PRK

6 months

No significant alterations, migration of cells

et al. J Refract

from the periphery to the centre of the

Corneal Surg

cornea. This beneficial effect is attributed

1994; 10: s194-8.

to discontinue use of contact lenses.

Carones F et al.

Myopia up to

PRK

12 months

Without significant cellular density losses.

Arch Ophthalmol

–13,5 Diopters

However, in 18% of cases the loss

1994; 112: 920-24.

exceeds 5%.

Maldonado MJ

Reply to the article:

Some ammetrope eyes are predisposed to

et al. Arch

Carones F et al. Arch

endothelial loss when a corneal

Opthalmol 1995;

Ophthalmol 1994; 112:

aggression occurs. Polymorphism and

113: 697.

920-24.

variability in cellular size are indicators of cellular stress. Their presence must be taken into account because it indicates possible alterations after corneal surgery.

Soto-Pedre E et al.

Reply to the article:

They suggest that endothelial losses could

Arch Ophthalmol

Carones F et al.

have been significant if the depth of

1995; 113; 697.

Arch Ophthalmol

ablation is taken into account.

1994; 112: 920-24.

Rosa N et al.

High myopia up to

PRK

6 months

Without endothelial alterations.

Ophthalmologica –17 Dp 1995; 209: 17-20 Mardelli PG et al. Myopia PRK 12-55 months

No damages are found in the central

Ophthalmology

endothelium. However, 34% of eyes

1995; 102: 544-49.

exhibit endothelial losses above 5%.

Maldonado MJ et al.

Reply to the article:

The endothelial count should be made in

Ophthalmology

Mardelli PG et al.

two groups; one in contact lens users prior

1995; 102:

Ophthalmology 1995;

to surgery and the other in non-users to

1736-37.

102: 544-49.

determine whether the loss is insignificant between both groups. The identification of prior morphometric alterations is useful for identifying subjects who are vulnerable to endothelial loss after laser.

Carones F et al.

Myopia up to

PRK

1 month

Without significant alterations.

Eur J Ophthalmol –12,50 diopters 1995; 5: 204-13. Nagy ZZ et al. Experimentation Animal. PRK

Three weeks after

The deepest ablations, added to the effect of

Acta Chir Hung

Ablation of –5, –15

the ablation, the

UV light, exaggerate the physiological loss

1995-96; 35:

and –30 Dp

corneae were

due to age, with the appearance of

325-32.

irradiated with

polymorphism and variations in size.

Table I.

Endothelial alterations after excimer laser corneal refractive surgery

(continuation) Authors Refractive defect Prevous endothelial Corneal refractive Follow-up

Results in endothelial density

dystrophia procedure Amano S et al. Myopia PRK 12 months

Without alterations in cellular density

Spadea L et al. J Cataract Refract

Myopia up to

PRK

11,4 months (±6,1)

Without changes in endothelial density.

Surg 1996; 22: –17 Diopters 188-93. Stulting RD et al. Mean Myopia PRK 24 months

Same endothelial density in the centre of the

Ophthalmology

cornea. Loss of endothelial cells in peripheral

1996; 103: 1357-65.

cornea per year. Improvements in the variation coefficient after two years.

Güell JL et al. J Refract

High Myopia:

LASIK

6

months

Without noteworthy alterations.

Surg 1996; 12: 222-28. – 7 t o –18,5 Diopters

Rosa N et al. Ophthalmologica

Myopia up to

PRK

24 months

Absence of significant changes.

1997; 211: 32-39.

–14 Diopters

Kent DG et al. J Cataract Refract

Myopia Magnus

PRK and LASIK

Extraction of

No endothelial toxicity with laser in any of the

Surg 1997; 23: globes obtained corneae after two methods 386-97. from autopsies photoablation (–10 to –25 Diopters)

and maintaining 7 days in culture.

Cennano G et al.

Myopia between

PRK

12 months

Without endothelial damage

Acta Ophthalmol –7 and -13 Diopters Scand 1997; 75: 128-30. Pérez-Santonja JJ et al. High myopia LASIK 6 months

Absence of endothelial damage in the central

J Cataract Refract

(–8,25 a –18,50 Diopters)

cornea.

Surg1997; 23:

and density attributable to discontinued use

177-83. of contact lenses. Pérez-Santonja JJ et al. High myopia LASIK 12 months

Absence of endothelial damage is in the central

Arch ophthalmol

(–8,25 to –18,50 Diopters)

cornea. Improvement in endothelial morphology

1997; 115: 841-46.

and density attributable to discontinued use of contact lenses.

Isager P et al. Myopia and astigmatism PRK 52 months

They prove that laser can be potentially damaging.

Acta Ophthalmol

Endothelial loss occurs only during ablation or

Scand 1998; 76:

in early times. Even though the central loss

304-7.

s small, it could be significant.

Joness et al.

Myopia up to

LASIK

12 weeks

Absence of variation in endothelial density and

Am J Ophthalmol

–14,5 Diopters

morphology

1998, 125: 465-71.

Kim T et al.

Middle Myopia and

LASIK

1

day

LASIK can cause acute changes in endothelium,

Cornea 2001;

astigmatism

causing corneal edema.

Table I.

Endothelial alterations after excimer laser corneal refractive surgery

(continuation) Authors Refractive defect Prevous endothelial Corneal refractive Follow-up

Results in endothelial density

dystrophia procedure Collins MJ et al. Myopia up to LASIK 3 6 months

Without changes in central endothelial density.

The

Am J Ophthalmol

–14,5 Diopters

variation coefficient improves after three years.

2001: 131; 1-6.

Jabbur NS et al.

Hypermetropia

PRK

12 months

Without significant changes in the corner centre

J Refract Surg 2003;

and periphery.

19: 142-48.

Nawa and et al.

Hypermetropia

LASIK

1

2 months

Endothelial density without alterations

J Cataract Refract Surg 2003; 29: 1543-45.

Dastjerdi MH et al.

Middle myopia

Fuchs Dystrophy

LASIK

67 days

Corneal edema and loss of pre-op VA.

Cornea 2003; (Case report) (cornea guttata 22: 379-81. without edema) Moshirfar M et al.

Myopia and myopic

Cornea guttata and

LASIK

1

2 months

Endothelial loss, corneal edema, loss of visual

J Cataract Refract

astigmatism.

family history

acuity and myopic regression

Surg 2005; 31: of Fuchs Dystrophy 2281-86. (7 eyes of 4 patients) Moshirfar M et al. Moderate myopia Posterior polymorphic LASIK 1 2 months

2.3% of endothelial loss without clinical relevance.

Cornea 2005;

dystrophy

24. 230-32

(vesicular form) 4 eyes

Vroman DT et al.

Hypermetropia

Cornea guttata and

LASIK

1

4 months

Corneal edema in right eye which regressed.

J Cataract Refract

Case report:

Fuchs dystrophy

Corneal decompensation in left eye plus

Surg 2002; 28: OD: +1,5 Dp penetrating keratoplasty. 2045-49. OI: + 3,5 Dp Diakonis VF et al. Myopia PRK with intra-op 12 months

Absence of differences in the count of both groups.

Am J Ophthalmol mitomycine C, 2007; 144: Epi-Lasik in the 99-103. contralateral eye Tsiklis NS et al. Moderate myopia PRK 12 months

Without changes in endothelial density.

J Cataract Refract Surg 2007; 33: 1866-70.

Kato N et al.

Myopia

LASIK

6

0 months

1.2% of endothelial loss after five years,

Ophthalmology

statistically significant. However, they conclude

2008; 115:

it is similar to what occurs with age.

routine examination and therefore many undiag-nosed cases may exist.

The diagnostic of the entity is biomicroscopic and it can be confirmed by broad field mirror microscopy. The band forms are documented with less frequency (1,4). This case also studies the topography of the posterior cornea surface without observing changes corresponding to the bands visi-ble in biomicroscopy. The topographic and pachy-metric results do not contraindicate intervention to eliminate the astigmatism and hyperopia. In PPD, endothelial count is usually lower than in normal subjects. However, it has been documented that

ageing does not involve a faster loss of endothelial cells (4). Therefore, PPD gives rise to problems when corneal refractive surgery is desired. In most studies a significant loss of central endothelial cells has not been found after LASIK in healthy corneas (Table I). When the LASIK technique has been per-formed to correct hyperopia in a cornea with Fuchs dystrophy (5), the case evolved towards corneal decompensation and keratoplasty. In hyperopic LASIK, ablation is peripheral and therefore the endothelial cellularity must be taken into account at this level (5). In the two described LASIK cases for correcting myopia in PPD corneas (3), the endothe-lial loss after one year was of 2.3%. This loss is sig-nificant when compared to the loss in healthy sub-jects, which is usually of about 0.5% (3). During a one-year follow-up no corneal decompensation was observed (3). It is noteworthy that the endothelial count prior to surgery was greater than 2,200 cells/mm2 in the first case and greater than 2,600 cells/mm2_{in the second case.}

In our opinion and taking into account that the band and diffuse forms of PPD have a lower endothelial count (4), the result of the hyperopic laser in Fuchs dystrophy (5), the possibility of los-ing 2.3% per year after LASIK (3) plus the pro-gressive age-related endothelial loss, we advise against refractive surgery due to a high risk of corneal decompensation in these patients. Our unproved hypothesis is that a minimum count of 1,500 cells/mm2 _{in peripheral areas would be the}

bare minimum to perform LASIK surgery safely.

Fig. 4: Broad field mirror microscopy of peripheral cor-neal areas. Vesicles or craters surrounded by healthy endothelial cells in right eye.

Fig. 5: Broad field mirror microscopy in left eye. Diffu-se loss of endothelial cells.

Fig. 3: Biomicroscopy. Abundant vesicles at the endot-helial and Descemet membrane level. Right eye: Orange skin pattern (A,B). Left eye, presence of vesicles forming bands (CD).

Between 1,000 and 2,000 cells/mm2involves lower risk, but still tending to decompensation. Any endothelial alteration which compromises the endothelial pump may produce corneal disc adher-ence problems post-op. This is a further reason for advising against this operation in these patients. Although this would be avoidable with a surface procedures such as PRK, there is no certainty about subsequent endothelial loss. Even though PRK would exclude ablation of the endothelium, it is submitted to a functional burden due to stromal hydration through the denuded epithelium and to greater penetration of and exposure to somewhat toxic components of eye drops. Some studies do not refer significant losses of endothelial cells six months after PRK, whereas others refer a highly significant endothelial loss when a count is taken 50 months after surgery (Table I). According to these data, we believe that said procedures should be avoided in PPD patients.

In conclusion, this paper documents a new case of PPD identified in the course of routine explo-ration. The presence of vesicles at the level of

Descemet membrane and the endothelium point to the presence of PPD. Even though the cornea is transparent and no signs of focal or diffuse corneal edema can be found, mirror microscopy is a requirement prior to an indication of Excimer laser refractive surgery.

REFERENCES

1. Weisenthal RW, Streeten BW. Posterior membrane dys-trophies. In: Krachmer JH, Mannis MJ, Holland EJ. Cor-nea. Philadelphia: Elsevier Mosby; 2005; I: 929-954. 2. Barraquer RI, de Toledo MC, Torres E. Distrofias y

dege-neraciones corneales atlas y texto. Barcelona: Expaxs; 2004; 222-234.

3. Moshirfar M, Barsam CA, Tanner MC. Laser in situ kera-tomileusis in patients with posterior polymorphous dys-trophy. Cornea 2005; 24: 230-232.

4. Laganowsky HC, Sherrard ES, Kerr Muir MG. The poste-rior corneal surface in posteposte-rior polymorphous dystrophy: a specular microscopical study. Cornea 1991; 10: 224-232. 5. Vroman DT, Solomon KD, Holzer MP, Peng Q, Apple DJ, Bowie EM. Endothelial decompensation after laser in situ keratomileusis. J Cataract Refract Surg 2002; 28: 2045-2049.