Factors Associated with the Successful Separation of Corneal Epithelium in Epi-LASIK

Kyun-Hyung Kim; Joon-Heon Kim; Jong-Suk Song; Hyo-Myung Kim

doi:10.3341/jkos.2007.48.12.1623

Journal List > J Korean Ophthalmol Soc > v.48(12) > 1007981

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Kim, Kim, Song, and Kim: Factors Associated with the Successful Separation of Corneal Epithelium in Epi-LASIK

Original Article

J Korean Ophthalmol Soc 2007;48(12):1623-1629.

Published online: 30 August 2007

DOI: https://doi.org/10.3341/jkos.2007.48.12.1623

Factors Associated with the Successful Separation of Corneal Epithelium in Epi-LASIK

Kyun-Hyung Kim, M.D., Joon-Heon Kim, M.D., Jong-Suk Song, M.D. Ph.D., Hyo-Myung Kim, M.D. Ph.D.

Department of Ophthalmology, College of Medicine Korea University, Seoul, Korea

Address reprint requests to Hyo-Myung Kim, M.D. Ph.D., Department of Ophthalmology, Anam Hospital, College of Medicine, Korea University, #126-1 Anam-dong 5ga, Sungbuk-gu, Seoul 136-705, Korea, Tel: 82-2-920-5366, Fax: 82-2-924-6820, E-mail: hyomkim@kumc.or.kr

Received 27 February 2007 Accepted 14 August 2007

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose

To determine the incidence and perioperative factors of flap-related complications from Epi-LASIK.

Methods

In this study, 122 eyes of 66 patients who had Epi-LASIK using Centurion SES^TM epikeratome (Norwood Eye Care, Australia) were enrolled. Associations of pre-operative corneal curvature, white-to-white distance, central corneal thickness, refractive error, dry eye, punctate corneal erosion, pannus, and history of wearing contact lenses with flap-related complications were investigated. To decrease flap-related complications, surgeons pressed patients’ eyelids with a speculum during epithelial separation, and the effect of this method was verified.

Results

Complete epithelial separation was achieved in 74 eyes (60.6%), incomplete separation in 29 eyes (23.8%), and free epithelial sheet in 19 eyes (15.6%). Thin corneas (P=.041), a history of wearing contact lenses (P=.008), and the duration of contact lens use (P=.003) significantly decreased the incidence of successful epithelial separation. Pressing down the eyelids with a speculum while separating the epithelial sheet increased the incidence of complete separation from 50.6% to 83.8% (P=.003).

Conclusions

The risk of flap-related complications from Epi-LASIK may be higher in people who use contact lenses and in people who have thin corneas. The risk can be reduced by pressing the eyelids with a speculum during epithelial separation.

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Keywords: Epi-LASIK, Epithelial separation, Flap, Incomplete separation, Speculum

References

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Figure 1.

(A) Diagram of corneal surface to describe punctate erosion. The whole cornea was divided into 5 parts: superior, inferior, nasal, temporal, and central (4 mm in diameter in the center). (B) Diagram of the corneal surface to describe pannus.

The whole cornea was divided into 4 parts: superior, inferior, nasal, and temporal.

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Figure 2.

(A) Normal orbital structure with speculum (arrow). (B) Changes after pressing down the eyelids. Increased mtraorbital pressure makes the eyeball to protrude and corneal curvature steeper.

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Figure 3.

Hypothesis for incomplete separation. (A) In the early stage, the curvature of the cornea is so steep that it is enough to make counter-force against the separator. (B) In the middle stage, counter-force keeps up. (C) In the late stage, the curvature of the cornea flattens gradually and the decreased counter-force may cause incomplete separation.

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Table 1.

Preoperative patients parameter and flap-related complications

Parameters	Mean (±SD)			P
Parameters	Complete flap	Incomplete flap	Free flap	P
No. of cases (%)	74 (60.6%)	29 (23.8%)	19 (15.6%)
Amount of ablation	-4.32±1.8D	-4.31± 1.5 D	-4.17±1.3D	.934
Corneal thickness	547±27 μm^†,‡	536±26 μm;^†	534±31 μm;^‡	.041^*
White-to-white distance	11.5±0.3 mm	11.5±0.4 mm	11.7±0.3 mm	.095
Corneal curvature (5 mm)	42.8± 1.4	43.2±1.5	42.2±1.9D	.079

^* Statistically significant. One-way ANOVA

^†,‡ The same symbols indicate significant difference between groups based on Tukey's multiple comparison test.

Table 2.

Dry eye and flap-related complications

Tearfilm break-up time (second)	Incidence (%)			Total
Tearfilm break-up time (second)	Complete flap	Incomplete flap	Free flap	Total
< 5	5 (62.5)	1 (12.5)	2 (25)	8
5- 9	8 (61.5)	3 (23.1)	2 (15.4)	13
10 ≤	61 (60.4)	25 (24.8)	15 (14.8)	101

Chi-square, P=.914

Table 3.

Punctate erosion and flap-related complications

Punctate erosion^*	Incidence (%)			Total
Punctate erosion^*	Complete flap	Incomplete flap	Free flap	Total
0	57 (58.2)	23 (23.5)	18 (18.3)	98
1	7 (58.4)	4 (33.3)	1 (8.3)	12
2	5 (71.4)	2 (28.6)	0 (0)	7
2 <	3 (60)	1 (20)	1 (20)	5

Chi-square, P=.857

^* Sum of each scale of five corneal regions (superior, inferior, nasal, temporal, and central) graded using a 0-4 scale.

Table 4.

Pannus and flap-related complications

Pannus^*	Incidence (%)			Total
Pannus^*	Complete flap	Incomplete flap	Free flap	Total
0	71 (60.2)	28 (23.7)	19 (16.1)	118
1	2 (66.7)	1 (33.3)	0 (0)	3
1 <	1 (100)	0 (0)	0 (0)	1

Chi-square, P=.866

^* Numbers of quadrant of corneal involvement.

Table 5.

Contact lens wear and flap-related complications

	Incidence (%)			Total	P
	Complete flap	Incomplete flap	Free flap	Total	P
Contact lens use
Non user	41 (75.9)	7 (13)	6 (11.1)	54	.008^*
user	33 (48.5)	22 (32.4)	13 (19.1)	68	.008^*
Type of contact lens
Soft contact lens	24 (47.1)	18 (35.3)	9 (17.6)	51	.648
Hard contact lens	9 (53)	4 (23.5)	4 (23.5)	17	.648

Chi-square

^* Statistically significant.

Table 6.

Pattern of contact lens wear and flap-related complications

Pattern	Mean±SD			P
Pattern	Complete flap	Incomplete flap	Free flap	P
Frequency of CL wear (day/week)	4.06±2.03	6.10±1.09	5.38±1.69	.133
Period of CL wear (year)	6.72±4.21	9.53±4.07^†	5.43±4.04^†	.003^*

^* Statistically significant. One-way ANOVA

^† The same symbols indicate significant difference between groups based on Tukey's multiple comparison test.

Table 7.

Eyeball protrusion method and flap-related complications

Method	Incidence (%)			Total
Method	Complete Incomplete	Free flap	flap flap	Total
Conventional method	43 (50.6%)	25 (29.4%)	17 (20.0%)	85
Eyeball protrusion method	31 (83.8%)	4 (10.8%)	2 (5.4%)	37

Chi-square, P= .003

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