Impact of different clear corneal incision sizes on anterior corneal aberration for cataract surgery

Tan, Qing-Qing; Tian, Jing; Liao, Xuan; Lin, Jia; Wen, Bai-Wei; Lan, Chang-Jun

doi:10.5935/0004-2749.20200089

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ORIGINAL ARTICLE • Arq. Bras. Oftalmol. 83 (6) • Nov-Dec 2020 • https://doi.org/10.5935/0004-2749.20200089 copy

Impact of different clear corneal incision sizes on anterior corneal aberration for cataract surgery

Impacto de diferentes tamanhos de incisões em córnea clara nas aberrações da córnea anterior em cirurgia de catarata

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

Purpose:

To investigate the impact of different sizes of steep meridian clear corneal incisions for phacoemul sification on anterior corneal higher-order aberrations.

Methods:

Medical records of patients who underwent 2.2-mm coaxial micro-incision cataract surgery or 2.75-mm coaxial small-incision cataract surgery were retrospectively reviewed. Only patients with preexisting anterior corneal astigmatism <2.00 diopters (D) and ≥0.50 D who underwent a steep meridian clear corneal incision were included. Primary outcomes were 3^rd- to 6^th-order anterior corneal higher-order aberrations with an 8-mm pupil. Anterior corneal astigmatism and effective phaco time were evaluated as secondary outcomes. Preoperative and 3-month postoperative outcomes were evaluated.

Results:

Anterior corneal astigmatism significantly decreased after both procedures; however, there was no significant difference found in surgically induced anterior corneal astigmatism between the two procedures (p=0.146). Although the total higher-order aberrations did not significantly change after both procedures, the group comparison showed a significant difference in surgically induced total higher-order aberrations (a decrease of 0.337 ± 1.156 mm in 2.2-mm coaxial micro-incision cataract surgery and an increase of 0.106 ± 0.521 mm in 2.75-mm coaxial small-incision cataract surgery, p=0.046). Spherical aberrations significantly decreased after 2.2-mm coaxial micro-incision cataract surgery (p=0.001), whereas they did not change significantly after 2.75-mm coaxial small-incision cataract surgery (p=0.564). Coma did not significantly change after either of the procedures. Trefoil did not significantly change after 2.2-mm coaxial micro-incision cataract surgery (p=0.361), whereas it significantly increased after 2.75-mm coaxial small-incision cataract surgery (p<0.001). There was no significant difference shown in effective phaco time between the procedures. A significantly positive correlation was shown between surgically induced anterior corneal astigmatism and coma in 2.75-mm coaxial small-incision cataract surgery (r=0.387, p=0.006). There was no significant correlation found between any surgically induced higher-order aberration changes and effective phaco time.

Conclusions:

The results showed that 2.2-mm coaxial micro-incision cataract surgery and 2.75-mm coaxial small-incision cataract surgery did not significantly degrade the total higher-order aberrations of the anterior cornea. However, the surgically induced changes in total higher-order aberration showed a significant difference between the two procedures, with a slight reduction after 2.2-mm coaxial micro-incision cataract surgery and a slight increase after 2.75-mm coaxial small-incision cataract surgery. Phaco time and power used during surgery had no impact on corneal aberrations.

Keywords:
Phacoemulsification; Astigmatism; Cornea/surgery; Surgical wound; Treatment outcome

	2.2-mm C-MICS N=48	2.75-mm C-SICS N=50	p-value
Sex (female, %)	50	58	0.427^a a Chi-squared test;
Laterality (surgery in the right eye, %)	58.3	42	0.106^a a Chi-squared test;
Nuclear density (% in grades 2, 3, and 4)	25%, 58.3%, 16.7	26, 56, 18	0.971^a a Chi-squared test;
Age (years)	65.63 ± 4.983	67.26 ± 4.81	0.102^b b Independent t-test;
Axial length (mm)	23.413 ± 1.227	24.186 ± 2.515	0.091^c c = Mann-Whitney test.

	2.2-mm C-MICS			2.75-mm C-SICS
	Preoperative	Postoperative	p-value	Preoperative	Postoperative	p-value
BCVA (mean ± SD, logMAR)	1.107 ± 0.961	0.045 ± 0.068	<0.001^* * Statistical significance;	1.376 ± 0.862	0.032 ± 0.06	<0.001^* * Statistical significance;
ACA (mean ± SD, D)	0.938 ± 0.353	0.473 ± 0.329	<0.001^* * Statistical significance;	0.858 ± 0.302	0.539 ± 0.326	<0.001^* * Statistical significance;
t-HOA (mean ± SD, μm)	2.124 ± 1.087	1.788 ± 0.381	0.069	1.838 ± 0.394	1.944 ± 0.401	0.313
SA (mean ± SD, μm) ^¶ ¶ Paired t-test was used; the remaining variables were analyzed using the Wilcoxon signed-rank test.	1.463 ± 0.406	1.253 ± 0.146	0.001^* * Statistical significance;	1.371 ± 0.425	1.33 ± 0.353	0.564
Coma (mean ± SD, μm)	0.79 ± 0.563	0.625 ± 0.294	0.4	0.794 ± 0.374	0.786 ± 0.248	0.942
Trefoil (mean ± SD, μm)	0.555 ± 0.706	0.46 ± 0.185	0.361	0.362 ± 0.173	0.651 ± 0.209	<0.001^* * Statistical significance;

	Surgically induced changes^# # For this comparison, negative signs indicate an increase in the variables after surgery; no sign indicates a decrease.
	2.2-mm C-MICS	2.75-mm C-SICS	p-value
BCVA (mean ± SD, logMAR)	1.063 ± 0.979	1.343 ± 0.849	0.079
EPT (mean ± SD, s)	12.578 ± 11.632	19.237 ± 17.129	0.07
ACA (mean ± SD, D)	0.464 ± 0.545	0.32 ± 0.428	0.146^¶ ¶ Independent t-test was used; the remaining data were analyzed using the Mann-Whitney test.
t-HOA (mean ± SD, μm)	0.337 ± 1.156	-0.106 ± 0.521	0.046^* * Statistical significance.
SA (mean ± SD, μm)	0.21 ± 0.421	0.041 ± 0.501	0.075^¶ ¶ Independent t-test was used; the remaining data were analyzed using the Mann-Whitney test.
Coma (mean ± SD, μm)	0.165 ± 0.551	0.008 ± 0.459	0.323
Trefoil (mean ± SD, μm)	0.095 ± 0.67	-0.289 ± 0.255	<0.001^* * Statistical significance.

Corneal HOA changes (μm)	2.2-mm C-MICS				2.75-mm C-SICS
Corneal HOA changes (μm)	ACA changes (D)	p-value	EPT (s)	p-value	ACA changes (D)	p-value	EPT (s)	p-value
t-HOA	0.245	0.093	0.119	0.419	0.240^§	0.093	-0.280	0.048*
SA	0.065^§	0.66	-0.032	0.829	0.142^§	0.325	-0.092	0.523
Coma	-0.099	0.502	0.162	0.273	0.387^§	0.006*	-0.058	0.687
Trefoil	-0.159	0.28	0.047	0.751	0.105^§	0.467	0.01	0.946

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[1] Corresponding author: Chang-Jun Lan. E-mail: eyelanchangjun@163.com