Jin Kook Kim, MD, Sung Soo Kim, MD, Hyung Keun Lee, MD, In Sik Lee, MD, Gong Je Seong, MD, Eung Kweon Kim, MD, Sueng Han Han, MD

a r t i c l e s

Laser in situ keratomileusis versus laser-assisted

subepithelial keratectomy for the correction

of high myopia

Jin Kook Kim, MD, Sung Soo Kim, MD, Hyung Keun Lee, MD, In Sik Lee, MD,

Gong Je Seong, MD, Eung Kweon Kim, MD, Sueng Han Han, MD

Purpose: To compare the visual and refractive outcomes of laser in situ kerato-mileusis (LASIK) and laser-assisted subepithelial keratectomy (LASEK) in the treat-ment of high myopia.

Setting: Institute of Vision Research, Department of Ophthalmology, College of Medicine, Yonsei University, and Balgeunsesang Ophthalmology Clinic, Seoul, South Korea.

Methods: Four hundred seventy eyes of 240 patients with manifest refraction spherical components greater than –6.00 diopters (D) were assigned to 2 groups: 324 eyes (167 patients) were treated with LASIK and 146 eyes (73 patients), with LASEK. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), remaining refractive error, corneal haze, and complications were fol-lowed in both groups for 12 months.

Results: At 12 months, the mean spherical equivalent (SE) was within⫾0.50 D of emmetropia in 205 eyes (63.3%) in the LASIK group and 81 eyes (55.5%) in the LASEK group and within⫾1.00 D in 261 eyes (80.6%) and 104 eyes (71.2%), re-spectively. The UCVA was 20/25 or better in 269 LASIK eyes (83.0%) and 111 LASEK eyes (76.0%). There was more than a 1-line loss of BSCVA in 4 LASIK eyes (1.2%) and 21 LASEK eyes (14.3%). The between-group differences in SE, magnitude of cylinder, UCVA, and haze were statistically significant (P⬍.05). Conclusions: Both LASIK and LASEK were safe and effectively treated eyes with high myopia. Laser in situ keratomileusis provided superior results in visual pre-dictability and corneal opacity.

J Cataract Refract Surg 2004; 30:1405–1411  2004 ASCRS and ESCRS

Laser-assisted subepithelial keratectomy (LASEK) is

an-L

aser in situ keratomileusis (LASIK) has shown

en-other approach to photorefractive keratectomy (PRK),

couraging results in the treatment of high myopia

which creates an epithelial flap that is replaced after

and astigmatism.

1–3

_{Despite the advantages of the}

pro-photorefractive ablation. It is hypothesized that the

epi-cedure, epithelial ingrowth, corneal flap-related

compli-thelial flap decreases changes in stromal keratocytes and

cations, and corneal ectasia have been reported.

4–6

reduces the production of extracellular matrix and

colla-gen.

7

_{This may result in less postoperative haze than}

with PRK and more favorable visual outcomes. In

addi-tion, since no lamellar flap is created, LASEK may retain

Accepted for publication December 5, 2003.

the biomechanical stability seen with PRK and therefore

Reprint requests to Hyung Keun Lee, MD, Department of

Ophthalmol-be an alternative to LASIK, in which corneal thickness

ogy, Yong-Dong Severance Hospital, 146-92 Dogok-dong,

Kangnam-Gu, Seoul 135-720, South Korea. E-mail: shadik@yumc.yonsei.ac.kr.

may be reduced.

12 o’clock and 5 o’clock positions. A Hansatome威

micro-With moderate degrees of myopia, the visual

out-keratome (Bausch & Lomb Surgical) was used to create a

comes and incidence of postoperative stromal haze in

flap of 160␮m. Excess liquid was removed with a Merocel威

LASEK patients appear to be superior to those in PRK

sponge (Medtronic Solan). The flap was raised using a spatula

patients.

8–10

_{Additionally, LASEK has more favorable}

and the stromal bed exposed. The Nidek EC-5000 excimer

results than LASIK.

11

laser was fired on the dried corneal surface with the ablation

With surface ablation, the correction of high de-

_{centered over the entrance pupil. The flap was replaced using}

grees of myopia produces more corneal haze and regres-

a spatula and the peripheral epithelial markings. The epithe-lial and stromal portions of the flap were then irrigated with

sion than the correction of low degrees of myopia.

12,13

a cannula.

If the cornea is thick enough, LASIK may be preferred

Postoperatively, ofloxacin 0.3% (Tarivid威) and

diclo-to PRK in eyes with high myopia because of reduced

fenac 0.1% were instilled in the treated eye. The lid speculum

postoperative discomfort, improved immediate acuity,

_{was removed, and a therapeutic contact lens (Focus威,}

and less corneal haze.

14,15

_{With the suggested advantages}

Bausch & Lomb) was placed on the cornea. Patients were

of LASEK over PRK, there is a potential for less postop-

_{instructed to apply 1 drop of Tarivid and artifical tears}

(hyal-erative discomfort, faster visual rehabilitation, and re-

uronic acid 0.1% [Hyalrein威]) every 2 hours. One day post-operatively, the therapeutic contact lens was removed and

duced haze in highly myopic patients.

Tarivid and flurorometholone 0.1% (Fluorometholone) were

To our knowledge, there has been no comparison

administrated 4 times daily for 1 week, 2 times daily for 1

of the visual and refractive outcomes of LASIK and

month, and once a day for 1 month.

LASEK in the treatment of high myopia by a single

surgeon. In this study, we retrospectively compared the

_{Laser-Assisted Subepithelial Keratectomy}

visual and refractive outcomes, changes in best spectacle-

_{A speculum was applied to the patient’s eye, and}

propara-corrected visual acuity (BSCVA), and associated compli-

_{caine hydrochloride (Alcaine威) was instilled. An alcohol}

solu-cations in patients who had LASIK or LASEK for high

_{tion cone (J2905, Janach) with an 8.5 mm diameter was}

myopia and myopic astigmatism.

placed on the eye. Twenty percent of the alcohol solution was instilled inside the cone, left for about 20 seconds, and then carefully washed off with a balanced salt solution so the

Patients and Methods

epithelium around the flap was not disturbed. The epithelial

flap was gently lifted with an epithelial microhoe (J2915A, Two hundred forty patients were enrolled in this study

Janach) and peeled back as a single sheet toward the 12 between December 2001 and June 2002 for a sample of 470

o’clock position using a spatula (J2910A, Janach). Excimer consecutive eyes. Laser in situ keratomileusis was performed

laser treatment was performed in the usual manner using the in 324 eyes of 167 patients and LASEK, in 146 eyes of 73

same nomogram and laser system as in LASIK. The flap was patients. In all patients, myopia was greater than ⫺6.00

washed with a balanced salt solution and then repositioned diopters (D) (range ⫺6.00 to ⫺12.50 D) and astigmatism

carefully with a spatula. A therapeutic soft contact lens was was less than 4.50 D. The preoperative ophthalmic

examina-then placed on the eye. tion included slitlamp biomicroscopy, intraocular pressure,

Postoperatively, the eyes were checked daily until the fundoscopy, measurement of pupil diameter, Schirmer test,

epithelial defect was completely closed. The patients were manifest refractions, corneal keratometry, corneal

topogra-instructed to apply 1 drop of diclofenac and Tarivid every phy, corneal pachymetry, and visual field examination. No

2 hours and artificial tears every hour until epithelial healing patient had a history of refractive procedures, keratoconus,

was complete. After complete reepithelialization had oc-cataract surgery, diabetes, glaucoma, connective tissue

disor-curred, Tarivid and Fluorometholone were administered 4 ders, or retinal disease. All refractive surgery was performed

times daily for 1 week and 2 times daily for 1 month. by the same surgeon (J.K.K). Both procedures, including the

potential advantages, disadvantages, and complications, were Routine postoperative examinations were scheduled at fully described to patients who met the criteria. Each patient 1 week and then monthly up to 1 year. In the LASEK eyes, was then allowed to select the procedure. daily follow-up examinations were scheduled until epithelial healing was complete; subsequent examinations were as

Laser In Situ Keratomileusis

above. The uncorrected visual acuity (UCVA), manifest re-fraction, tonometry, and slitlamp biomicroscopy were per-Laser in situ keratomileusis was performed under topical

formed at all examinations. Subepithelial corneal haze levels anesthesia with proparacaine hydrochloride 0.5% (Alcaine威).

were checked at the slitlamp at 6 and 12 months and graded A rigid eyelid speculum was used. Two radial marks were

Table 1. Preoperative independent variables.

Variable LASIK (n⫽ 324 Eyes) LASEK (n⫽ 146 Eyes) P Value

Age* Mean⫾ SD 28.37⫾ 6.71 27.91⫾ 4.31 NS* Range 21_{⬃ 39} 20_{⬃ 41} Sex (male/female) 55/112 20/53 NS† Spherical equivalent (D) Mean⫾ SD ⫺7.91 ⫾ 1.26 ⫺8.01 ⫾ 1.85 NS* Range ⫺6.00 ⬃ ⫺11.50 ⫺6.00 ⬃ ⫺12.50 Degree of cylinder Mean⫾ SD 1.99⫾ 0.66 2.13⫾ 0.63 NS* Range 0.00⬃ 4.50 0.00⬃ 4.50

LASEK⫽ laser-assisted subepithelial keratectomy; LASIK ⫽ laser in situ keratomileusis; NS ⫽ not significant * Unpaired Student t test

†_{Chi-square test}

Data analysis was performed using the Statistical Analysis

_{⫹0.51 ⫾ 1.15 D in the LASEK group; P ⫽ .067).}

System (version 6.12, SAS Institute Inc.). The probability

_{From the third month, the between-group difference}

value of P⬍.05 was considered statistically significant.

in the mean SE was statistically significant:

⫺0.29 ⫾

0.89 D in the LASIK group and

⫺0.61 ⫾ 1.09 D in

Results

_{the LASEK group at 3 months;}

_{⫺0.71 ⫾ 1.14 D and}

⫺1.11 ⫾ 1.23, respectively, at 6 months; and ⫺0.77 ⫾

The preoperative characteristics of the patients are

1.01 D and

⫺1.24 ⫾ 1.31 D, respectively, at 12 months

shown in Table 1. At the preoperative examination, the

between-group differences in the independent variables

(all P⬍.05). Additionally, in the LASEK eyes, there

were not statistically significant.

was a gradual increase in the mean SE at 6 months. In

The mean postoperative spherical equivalent (SE)

the LASIK eyes, there was little change in the mean SE

changes are shown in Figure 1. From the first month,

_{after 3 months.}

the remaining SE was higher in the LASEK group than

_{At 12 months, in the LASIK eyes, the mean SE}

in the LASIK group. At 1 month, the SE appeared

_{refraction was within}

_{⫾1.00 D of emmetropia in 261}

slightly hyperopic in both groups but the between-

_{eyes (80.6%) and within}

_{⫾0.50 D in 205 eyes (63.3%).}

group difference was not statistically significant

_{In the LASEK eyes, it was within}

_{⫾1.00 D of}

emmetro-(

⫹0.43 D ⫾ 0.78 [SD] in the LASIK group and

_{pia in 104 eyes (71.2%) and within}

_{⫾0.50 D in 81}

eyes (55.5%) (P

⫽ .00) (Table 2).

In LASIK eyes, the mean postoperative astigmatism

remained stable from 1 to 12 months. At 1 month, the

magnitude of cylinder was within

⫾1.00 D of the

intended correction in 303 LASIK eyes (93.5%) and

135 LASEK eyes (92.5%) (P⬎.05). At 12 months, it

was within

⫾1.00 D in 295 LASIK eyes (91.1%) and

109 LASEK eyes (74.7%) (P

⫽ .00) (Table 3).

The between-group difference in UCVA was

statis-tically significant from 1 to 12 months postoperatively

(Table 4). At 12 months, the UCVA was 20/20 or

better in 232 LASIK eyes (71.6%) and 88 LASEK eyes

(60.3%); 20/25 or better in 269 (83.0%) and 111

(76.0%), respectively; and 20/40 or better in 307

Figure 1. (Kim) The mean SE after LASIK and LASEK.

Table 2. Attempted and achieved SE after LASIK (n⫽ 224) and LASEK (n ⫽ 146).

Month After Surgery (% of Eyes)

1* 6* 12*

Diopter LASIK LASEK LASIK LASEK LASIK LASEK

ⱕ⫾0.50 81.5 71.2 70.1 69.2 63.3 55.5 ⱕ⫾1.00 89.7 82.4 88.6 62.3 80.6 71.2 ⬎⫾1.00 10.3 17.8 11.4 37.7 19.4 44.5 LASEK⫽ laser-assisted subepithelial keratectomy; LASIK ⫽ laser in situ keratomileusis; SE ⫽ spherical equivalent

* P⬍.05, chi-square test

Table 3. Magnitude of postoperative refractive cylinder after LASIK (n⫽ 224) and LASEK (n ⫽ 146).

Month After Surgery (% of Eyes)

1 6* 12*

Diopter LASIK LASEK LASIK LASEK LASIK LASEK

ⱕ⫾0.50 77.5 80.3 78.7 58.2 76.5 54.8 ⱕ⫾1.00 93.5 92.5 92.6 76.0 91.1 74.7 ⬎⫾1.00 6.5 7.5 7.4 24.0 8.9 25.3 LASEK⫽ laser-assisted subepithelial keratectomy; LASIK ⫽ laser in situ keratomileusis

* P⬍.05, chi-square test

Table 4. Uncorrected visual acuity after LASIK (n⫽ 224) and LASEK (n ⫽ 146).

Month After Surgery (% of Eyes)

1* 6* 12*

UCVA LASIK LASEK LASIK LASEK LASIK LASEK

ⱖ20/20 82.1 69.9 75.3 63.0 71.6 60.3 ⱖ20/25 90.1 84.3 83.6 77.4 83.0 76.0 ⱖ20/40 98.5 92.5 94.4 89.0 94.8 91.1 ⬍20/40 1.5 7.5 5.6 11.0 5.2 8.9 LASEK⫽ laser-assisted subepithelial keratectomy; LASIK ⫽ laser in situ keratomileusis; UCVA ⫽ uncorrected visual acuity

* P_{⬍.01, chi-square test}

Figure 3. (Kim) Changes in BSCVA after LASIK (n⫽ 224) and

Figure 2. (Kim) Changes in BSCVA after LASIK (n⫽ 224) and

Corneal flap displacements were found on the first

postoperative day in 4 LASIK eyes (1.2%). In all 4,

corneal flap folds that required repositioning surgery

on the same day were found. Epithelial ingrowth, severe

diffuse lamellar keratitis, and flap infection were not

found in LASIK eyes.

Discussion

In our study, LASIK and LASEK corrected high

myopic refractive errors successfully up to 1 year

postop-eratively. However, the LASIK procedure was found to

Figure 4. (Kim) Changes in BSCVA after LASIK (n⫽ 224) and

be a more favorable method for correcting high myopia

LASEK (n⫽ 146) at 12 months.

than LASEK.

Helmy and coauthors

17

_{report that residual}

refrac-(94.8%) and 133 (91.1%), respectively (P⬍.01). The

tive errors were within

⫾1.00 D of emmetropia after

BSCVA was better in the LASIK eyes than the LASEK

LASIK in 34 (85.0%) of 40 eyes with more than

eyes (Figures 2 to 4). There was a 1- or 2-line loss of

_{⫺6.00 D of myopia 12 months after surgery using the}

BSCVA in 4 LASIK eyes (1.2%) and 21 LASEK eyes

Summit OmniMed excimer laser. Zaldivar and

coau-(14.7%) at 12 months. No LASIK eye lost more than

thors

2

_{report that 70 (83.3%) of 84 eyes were within}

2 lines of BSCVA. Four LASEK eyes (2.7%) had lost

_{⫾1.00 D of emmetropia 6 months after surgery using}

3 lines at 12 months. Sixteen LASIK eyes (4.9%) and

_{the Nidek EC-5000, which was the laser system used}

2 LASEK eyes (1.4%) gained 1 or 2 lines of BSCVA

_{in our study. In LASIK eyes, our outcomes were similar}

(Figure 4). The main reasons for decreased BSCVA in

_{to those in previous reports of LASIK for high myopia.}

LASEK eyes were stromal opacity with myopic regres-

_{However, when comparing our LASEK results with}

sion (12.3%), irregular astigmatism (1.4%), and eccen-

_{those in PRK reports, the LASEK method showed}

supe-tric ablation (0.7%); in LASIK eyes, the reasons were

_{rior refractive predictability in correcting high myopia.}

flap-related complications, which were the result of ir-

_{Previous studies report that 12 months after PRK, the}

regular astigmatism, interface haze, and a combination

_{remaining SE was within}

_{⫾1.00 D in 29.0% to 68.0%}

of both.

of eyes.

12,17–19

At 1 month, the corneal haze score was less than

There is controversy about comparing visual and

grade 1 in all eyes. At 12 months, the score was above 2

refractive outcomes of LASEK and PRK.

10,20,21

_However,

in 11 LASEK eyes (7.5%). No LASIK eye had detectable

generally, LASEK eyes have more favorable refractive

outcomes than PRK eyes.

13,22

_{The mechanism}

ex-haze (Table 5) (P

⬍.01).

Table 5. Incidence and grade of corneal haze after LASIK (n⫽ 224) and LASEK (n ⫽ 146).

Month After Surgery (% of Eyes)

1* 6* 12*

Haze Grade LASIK LASEK LASIK LASEK LASIK LASEK

0 96.0 53.4 63.9 19.9 56.3 15.1 0.5 4.0 32.2 32.4 19.9 38.3 28.1 1 0 14.4 3.1 34.9 2.8 31.5 2 0 0 0.6 19.2 0.6 17.8 3 0 0 0 6.1 0 7.5 4 0 0 0 0 0 0 * P⬍.05, chi-square test

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