Analysis of Changes in Anterior, Posterior and Total Corneal Astigmatism after On-Axis Cataract Surgery

Kee Il Lee; Yu Li Park; Hyun Seung Kim

doi:10.3341/jkos.2016.57.1.25

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Lee, Park, and Kim: Analysis of Changes in Anterior, Posterior and Total Corneal Astigmatism after On-Axis Cataract Surgery

Original Article

J Korean Ophthalmol Soc 2015;57(1):25-35.

Published online: 29 August 2015

DOI: https://doi.org/10.3341/jkos.2016.57.1.25

Analysis of Changes in Anterior, Posterior and Total Corneal Astigmatism after On-Axis Cataract Surgery

Kee Il Lee, M.D, Yu Li Park, M.D, Hyun Seung Kim, M.D, PhD

Department of Ophthalmology and Visual Science, College of Medicine, The Catholic University of Korea, Seoul, Korea

Address reprint requests to Hyun Seung Kim, MD, PhD Department of Ophthalmology, Yeouido St. Mary's Hospital, #10 63-ro, Yeongdeungpo-gu, Seoul 07345, Korea Tel: 82-2-3379-1243, Fax: 82-2-761-6869 E-mail: Sara514@catholic.ac.kr

‗ This study was presented as a narration at the 112th Annual Meeting of the Korean Ophthalmological Society 2014.

Received 10 April 20155 August 2015 Accepted 1 October 2015

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 assess the changes in anterior, posterior, and total corneal astigmatism after cataract surgery with on-axis clear corneal incision cataract surgery.

Methods

This study included 48 eyes (24 eyes with ‘with-the-rule [WTR]’ and 24 eyes with ‘against-the-rule [ATR]’) that under-went phacoemulsification and intraocular lens insertion through on-axis clear corneal incision. The ATR group with vertically steep axis of posterior corneal astigmatism was divided into subgroups 1 and 2 for the opposite axis. Autorefraction, uncorrected and best-corrected visual acuities were measured. Corneal astigmatism (anterior, posterior and total) was measured using Pentacam^® preoperatively and 1 week, 1 month, and 2 months postoperatively.

Results

Multivariate linear regression analysis of preoperative data showed positive correlations among anterior, posterior and total astigmatism. Anterior corneal astigmatism showed a significant decrease in both WTR and ATR groups in all measured points (all p < 0.05). Posterior corneal astigmatism showed no statistical difference in the WTR group and ATR subgroup 2 ( p > 0.05) and significant decrease in the ATR subgroup 1 ( p < 0.05) at 2 months postoperatively. Total corneal astigmatism showed significant decrease 2 months after surgery in the WTR group and ATR subgroup 1 (all p < 0.05), but not in the ATR subgroup 2 ( p > 0.05). According to correlation analysis based on trend line equations, 1.7 diopters of anterior astigmatism could expect 0.3 diopters of posterior astigmatism and 0.5 diopters of total astigmatism for the WTR group and 0.4 diopters of anterior astigma-tism could expect 0.2 diopters of posterior astigmatism and 0.4 diopters of total astigmatism for the ATR group.

Conclusions

Considering the majority of cataract patients have vertically steep posterior corneal astigmatism, temporal incision for ATR patients is generally effective. Moreover, for patients with WTR astigmatism of more than 1.7 diopters or ATR astigma-tism greater than 0.8 diopters, additional preoperative correction based on posterior astigmatism is needed for more precise pre-diction of postoperative total corneal astigmatism.

Keywords: Against-the-rule (ATR), On-axis incision, Posterior corneal astigmatism, With-the-rule (WTR)

References

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Figure 1.

Location of steep meridian on anterior and posterior corneal astigmatism. ^* Vertical alignment of the steep corneal meridian was seen in 50.0% for the anterior cornea; ^† Vertical alignment of the steep corneal meridian was seen in 83.3% for the posterior cornea.

Figure 2.

Double-angle plots of corneal astigmatism and SIA using Pentacam® (Oculus, Wetzlar, Germany) from WTR group. Red dots denote for mean values of the amount and axis of corneal astigmatism for each group in (A) to (C). (A) Preoperative anterior (left), posterior (middle) and total (right) corneal astigmatism. (B) Postoperative 2 months anterior (left), posterior (middle) and total (right) corneal astigmatism. (C) SIA in anterior (left), posterior (middle) and total (right) corneal astigmatism. SIA = surgically in-duced astigmatism; WTR = with-the-rule.

Figure 3.

Double-angle plots of corneal astigmatism and SIA using Pentacam® (Oculus, Wetzlar, Germany) from ATR subgroup 1. Red dots denote for mean values of the amount and axis of corneal astigmatism for each group in (A) to (C). (A) Preoperative ante-rior (left), posterior (middle) and total (right) corneal astigmatism. (B) Postoperative 2 months anterior (left), posterior (middle) and total (right) corneal astigmatism. (C) SIA in anterior (left), posterior (middle) and total (right) corneal astigmatism. SIA = surgi-cally induced astigmatism; ATR = against-the-rule.

Figure 4.

Estimated cut-off value for preoperative consideration of posterior astigmatism in WTR group. (A) Trend line equation was calculated with preop.‘A’ and ‘P’. (B) Trend line equation was calculated with preop. ‘P’ and postop ‘T’ corneal astigmatism. WTR = with-the-rule; A = anterior; P = posterior; T = total; preop = preoperative; postop = postoperative; Post. = posterior astigmatism.

Figure 5.

Correlations of magnitude of the ‘A’, ‘P’ and ‘T’ corneal astigmatism in WTR group. (A) Correlations of magnitude of preop ‘A’ and ‘T’ corneal astigmatism. (B) Correlations of magnitude of preop ‘A’ and postop ‘T’ corneal astigmatism. (C) Correlations of magnitude of preop ‘T’ and ‘P’ corneal astigmatism. Trend line equations for each correlation were calculated. WTR = with-the-rule; A = anterior; P = posterior; T = total; preop = preoperative; postop = postoperative.

Figure 6.

Estimated cut-off value for preoperative consideration of posterior astigmatism in WTR group. (A) Trend line equation was calculated with preop. ‘A’ and ‘P’. (B) Trend line equation was calculated with preop. ‘P’ and postop ‘T’ corneal astigmatism. WTR = with-the-rule; A = anterior; P = posterior; T = total; preop = preoperative; postop = postoperative; Post. = posterior astigmatism; ATR = against-the-rule.

Figure 7.

Table 1.

Patient characteristics

Variables	With-the-rule group	Against-the-rule group	p-value^*
No. of eyes	24	24
Laterality (OD:OS)	9:15	12:12
Sex (M:F)	5:19	8:16
Age (years)	61.71 ± 9.56	63.91 ± 17.62	0.173
IOP (mm Hg)	14.32 ± 2.53	14.68 ± 2.47	0.244
Pachymetry (μ m)	550.66 ± 33.40	551.29 ± 30.53	0.861
Endothelial cell count (cells/mm²)	2,798 ± 346	2,638 ± 494	0.370
Axial length (mm)	24.02 ± 1.40	23.76 ± 2.09	0.167

Values are presented as mean ± SD unless otherwise indicated. IOP = intraocular pressure.

^* By Mann-Whitney U-test.

Table 2.

Data summary of UCVA, BCVA, SE and topographic astigmatism

	With-the-rule group	Against-the-rule group	p-value^*
Pre-op
UCVA (log MAR)	0.291 ± 0.175	0.292 ± 0.195	0.860
BCVA (log MAR)	0.462 ± 0.220	0.441 ± 0.217	0.925
SE (diopter)	-0.719 ± 3.318	-0.646 ± 3.561	0.992
Auto-refractive astigmatism (diopter)	-1.417 ± 1.433	-1.542 ± 0.783	0.130
Post-op 2 months
UCVA (log MAR)	0.468 ± 0.229	0.496 ± 0.262	0.747
BCVA (log MAR)	0.815 ± 0.122	0.780 ± 0.212	0.814
SE (diopter)	-1.156 ± 0.699	-0.875 ± 0.864	0.208
Auto-refractive astigmatism (diopter)	-0.802 ± 0.840	-0.990 ± 0.640	0.089

Values are presented as mean ± SD unless otherwise indicated. UCVA = uncorrected visual acuity; BCVA = best corrected visual acuity; SE = spherical equivalent; Pre-op = preoperative; Post-op = postoperative.

^* By Mann-Whitney U-test.

Table 3.

Changes of anterior, posterior, and total corneal astigmatism before and after surgery

	Pre-op (D)	Post-op 1 week (D)	Post-op 1 month (D)	Post-op 2 months (D)
With-the-rule group
Ant.	1.246 ± 0.999	0.608 ± 0.475	0.621 ± 0.436	0.717 ± 0.466
Post.	0.258 ± 0.102	0.383 ± 0.114	0.346 ± 0.110	0.313 ± 0.128
Total	1.104 ± 0.991	0.429 ± 0.291	0.558 ± 0.491	0.588 ± 0.410
Against-the-rule group (Post. corneal steep meridian with 90 ± 30°)
Ant.	1.127 ± 0.492	0.653 ± 0.360	0.673 ± 0.299	0.707 ± 0.274
Post.	0.327 ± 0.181	0.227 ± 0.110	0.247 ± 0.145	0.220 ± 0.125
Total	1.480 ± 0.587	0.820 ± 0.495	0.867 ± 0.299	0.900 ± 0.510
Against-the-rule group (Post. corneal steep meridian with 180 ± 30°)
Ant.	1.478 ± 1.398	0.878 ± 0.485	0.889 ± 0.472	0.733 ± 0.394
Post.	0.211 ± 0.141	0.300 ± 0.250	0.289 ± 0.252	0.378 ± 0.218
Total	1.222 ± 0.746	0.978 ± 0.552	0.889 ± 0.326	1.044 ± 0.541

Values are presented as mean ± SD. Pre-op = pre-operative; Post-op = post-operative; D = diopter; Ant. = anterior; Post. = posterior.

Table 4.

Comparisions of anterior, posterior, and total corneal astigmatism before and 2 months after surgery

	Pre-op (D)	Post-op 2 months (D) △	△ Astigmatism p-value^*
With-the-rule group
Ant.	1.246 ± 0.999	0.717 ± 0.274	p = 0.018
Post.	0.258 ± 0.102	0.313 ± 0.125	p = 0.055
Total	1.104 ± 0.991	0.588 ± 0.510	p = 0.023
Against-the-rule group (Post. corneal steep meridian with 90 ± 30°)
Ant.	1.127 ± 0.492	0.707 ± 0.394	p = 0.016
Post.	0.327 ± 0.181	0.220 ± 0.218	p = 0.049
Total	1.480 ± 0.587	0.900 ± 0.541	p = 0.008
Against-the-rule group (Post. corneal steep meridian with 180 ± 30°)
Ant.	1.478 ± 1.398	0.733 ± 0.466	p = 0.018
Post.	0.211 ± 0.141	0.378 ± 0.128	p = 0.094
Total	1.222 ± 0.746	1.044 ± 0.410	p = 0.605

Values are presented as mean ± SD unless otherwise indicated. Pre-op = pre-operative; Post-op = post-operative; D = diopter; Ant. = anterior; Post. = posterior.

^* By Mann-Whitney U-test.

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