Effects of Eye Registration on the Astigmatism Correction in the Surface Laser Ablation

Deoksun Cha; Sang Kyoon Kim; Gyeoung Hwan Roh; Hyo Myung Kim; Jong Suk Song

doi:10.3341/jkos.2010.51.6.809

Journal List > J Korean Ophthalmol Soc > v.51(6) > 1008832

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Cha, Kim, Roh, Kim, and Song: Effects of Eye Registration on the Astigmatism Correction in the Surface Laser Ablation

Original Article

J Korean Ophthalmol Soc 2010;51(6):809-815.

Published online: 3 June 2010

DOI: https://doi.org/10.3341/jkos.2010.51.6.809

Effects of Eye Registration on the Astigmatism Correction in the Surface Laser Ablation

Deoksun Cha, MD¹, Sang Kyoon Kim, MD², Gyeoung Hwan Roh, MD³, Hyo Myung Kim, MD¹, Jong Suk Song, MD¹

¹Department of Ophthalmology, Korea University College of Medicine, Seoul, Korea

²Department of Ophthalmology, Hongseong Medical Center, Hongseong, Korea

³Hansol Eye Clinic Center, Daejeon, Korea

Address reprint requests to Jong Suk Song, MD Department of Ophthalmology, Guro Hospital, Korea University College of Medicine #97, Guro-dong, Guro-gu, Seoul 152-703, Korea Tel: 82-2-818-6144, Fax: 82-2-857-8580, E-mail: crisim@freechal.com

Received 4 January 2010 Accepted 14 April 2010

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 compare the effect of astigmatism correction upon Mel 80 excimer laser surgery with or without an eye registration system.

Methods

This retrospective analysis investigates a group (eye registration group) of surface laser ablation surgeries for myopic astigmatism correction, with operation on 27 eyes from 15 patients with guidance of the eye registration system and 40 eyes from 29 patients without guidance from the eye registration system. The evaluation of astigmatism correction was performed by the Alpins method, measuring the amount and axis of astigmatism before and after the operations.

Results

The average of the correction index (the ratio of the surgically induced amount of astigmatism correction to the intended amount of astigmatism correction) for the eye registration group was calculated to be 0.94±0.30 and, for non-eye registration group, was 0.92±0.41, showing no statistical significant difference between the two groups (p=0.762). However, the comparison of the index of success (the ratio of the difference vector to the intended amount of astigmatism correction) favorably demonstrated the effectiveness of eye registration (0.23±0.34 for eye registration group, 0.47±0.54 for non-eye registration group, p=0.03). The absolute angle of error (AE), a measure of difference in angle between the ablated axis of astigmatism correction and the desired axis of astigmatism correction, was lower on average for the eye registration group than for the non-eye registration group (3.52±7.69 to 12.5±20.69 degrees, p=0.015).

Conclusions

Eye registration-guided surface laser ablation is suggested to be beneficial for the reduction of errors in astigmatism correction.

Keywords: Alpins method, Astigmatism correction, Eye registration, Laser surface ablation

References

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Figure 1.

VECTrAK (version 1.500) program used to calculate astigmatism change.

Figure 2.

Ocular cyclotorsion in eye registration group and non eye registration group. In non eye registration group, there was a trend of excylotorsion.

Table 1.

Baseline characteristics between two groups

	Eye registration group	Non eye registration group	p-value
Male : Female	4:11	16:13	0.11
Age (yrs)	29.0±4.75	26.7±5.76	0.70
Spherical equivalent	-4.50±2.01	-3.98±2.30	0.33
Astigmatism	0.83±0.56	0.57±0.54	0.06

Table 2.

Comparison of TIA, SIA, CI between two groups

	Eye registration group	Non eye registration group	p-value
TIA	0.83±0.56	0.57±0.54	0.06
SIA	0.72±0.47	0.47±0.45	0.06
CI (SIA/TIA)	0.94±0.30	0.92±0.41	0.76

TIA=target-induced astigmatism TIA; SIA=surgically induced astigmatism; CI=correction index (the ratio of the surgically induced amount of astigmatism correction to the intended amount of astigmatism correction).

Table 3.

Comparison of DV, TIA, IOS between two groups

	Eye registration group	Non eye registration group	p-value
DV	0.18±0.23	0.22±0.25	0.48
TIA	0.83±0.56	0.57±0.54	0.06
IOS (DV/TIA)	0.23±0.34	0.47±0.54	0.03

DV=difference vector; IOS=index of success.

Table 4.

Comparison of mean AE, mean absolute AE between two groups

	Eye registration group	Non eye registration group	p-value
Mean AE	1.52±8.34°	1.55±24.21°	0.994
Mean absolute AE	3.52±7.69°	12.5±20.69°	0.015

AE=angle of error.

Table 5.

Comparison of AE (angle of error) between eyes

	Eye registration group	Non eye registration group
OD	+0.60±9.86°	-2.94±18.0°
OS	+2.67±6.17°	+4.87±27.9°

(+)=counter clockwise AE (angle of error); (-)=clockwise AE (angle of error)

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