Comparison of surgically induced astigmatism between horizontal and X-pattern sutures in the scleral tunnel incisions for manual small incision cataract surgery

Refractive surprise of irregular astigmatism following cataract surgery in two patients with neglected subclinical corneal ectasia: two case reports

BACKGROUND

Corneal ectatic diseases are a group of corneal disorder characterized by the steepening and thinning of the cornea. Older people are not a high-risk population for corneal ectatic diseases; due to the lack of typical preoperative topographic manifestations, there is a high possibility that corneal ectasia is undetected.

CASE PRESENTATION

Two patients with subclinical corneal ectasia and senile cataracts presented with irregular astigmatism after steep-axis incision during cataract surgery. The two cases presented in this case report are rare because both patients experienced tremendous changes in astigmatism after cataract surgery.

CONCLUSION

This case report may shed some light on astigmatism-correcting steep-axis incisions in cataract surgeries.

Re-inventing the straight incision with a single central suture in manual small-incision cataract surgery to minimize surgically induced astigmatism

Purpose

To calculate the surgically induced astigmatism (SIA) in MSICS through a superiorly placed straight scleral incision closed with a single, central, perpendicular 10-0 polyamide suture and to document any suture-related complaints and complications.

Methods

A retrospective, hospital-based study was carried out in 50 cases of uncomplicated senile cataract (>50 year) with nuclear sclerosis ≥ grade 4, "with the rule" astigmatism who underwent MSICS through a superior, straight incision with a single, central, perpendicular 10-0 nylon suture. Patients with "against the rule" astigmatism, keratoconus, pre-existing corneal opacity, astigmatism >2D, distorted or oblique mires, and previous ocular surgeries and unwilling to participate were excluded.

Results

The mean age of the patients was 64.81 + 2.824 years, with a male: female ratio of 1.38:1. The mean SIA at day 7, week 6, and 12 weeks was 0.539 + 0.118, 0.529 + 0.134, and 0.524 + 0.129, respectively. Only 6 patients (12%) complained of foreign body sensation. No patient developed any suture-related complications.

Conclusion

SIA is significantly reduced in straight incision by applying a single, central, and perpendicular 10-0 polyamide suture, as compared to a straight incision without a suture.

Postoperative astigmatic considerations in manual small-incision cataract surgery - A review

Cataract remains a major cause of visual impairment worldwide including in India. The sutureless manual small-incision cataract surgery (MSICS) as an alternative to phacoemulsification, gives equivalent visual results at lower expenses. Still the procedure is often discredited for higher astigmatism due to the larger size of the incision. High astigmatism is an important cause of poor uncorrected visual acuity after cataract surgery. However, there are enough studies in the literature to prove that surgically induced astigmatism (SIA) can be minimized and also eliminated by adopting appropriate wound construction techniques during surgery. Even pre-existing astigmatism if any can be neutralized by changing wound architecture during surgery. Here, we review the various techniques of scleral tunnel construction described in the literature to care for postoperative astigmatism in MSICS.

Factors affecting surgically induced astigmatism in manual small-incision cataract surgery

Cataract is the most common cause of avoidable blindness in the world. While cataract surgery is continually evolving, manual small-incision cataract surgery (MSICS) still remains highly relevant, especially with the threat of the coronavirus disease 2019 (COVID-19) still looming large over the world. MSICS today has a renewed significance, since it does not involve the use of any advanced machinery and relies mainly on easily sterilizable instruments, thereby making it a safe and inexpensive option. A self-sealing valvular tunnel entry forms the basis of MSICS, and proper positioning and construction of the tunnel is imperative to the success of the surgery. With more and more people demanding spectacle independence after surgery, it becomes important to have a thorough understanding of the factors that may influence surgically induced astigmatism in MSICS. These include the incision location, size and shape, configuration of the sclero-corneal tunnel, pre-existing ocular pathology, role of sutures, amongst others. With proper knowledge, many of these factors can be modulated to achieve best results.

Evolution of manual small-incision cataract surgery from 8 mm to 2 mm - A comprehensive review

Cataract is the most common cause of reversible blindness worldwide, accounting for approximately 50% of blindness worldwide. Cataract surgery is the most common surgical procedure performed in routine ophthalmic practice. It has undergone tremendous evolution, and the incision size has progressively reduced from 10-12 mm in extracapsular cataract surgery (ECCE) to 6-8 mm for manual small-incision cataract surgery (MSICS) and 2.2-2.8 mm in phacoemulsification. In a developing country like India, with a massive backlog of cataract, everyone cannot afford private surgery like phacoemulsification. Moreover, annual maintenance of the machine, cost of foldable IOLs, need for greater skill, learning curve, and difficulty in performing the surgery in mature and brown cataracts are other barriers. Due to these factors, MSICS is the surgery of choice in the developing world, with profound societal and economic benefits and similar visual recovery compared to phacoemulsification. During the last two decades, MSICS gained popularity in developing countries and has undergone tremendous advances. This article aims to review the various techniques of MSICS and how the surgery has evolved over the years, particularly focusing on the current technique of 2-mm MSICS.

Surgically induced astigmatism and refractive outcomes following phacotrabeculectomy

Purpose

To objectively evaluate surgically induced astigmatism (SIA) after phacotrabeculectomy using keratometry and topography and to compare the magnitude of SIA and the refractive outcomes of single-site and twin-site phacotrabeculectomies.

Methods

Forty prospective subjects were enrolled in the study and were randomized into single-site and twin-site cohorts. SIA was objectively assessed using keratometry and Orbscan before and at three months after surgery. For both cohorts, the changes in SIA were assessed using power vector analysis compared at the third month after surgery.

Results

Each cohort consisted of 20 eyes. The preoperative parameters and postoperative IOP were comparable and similar, respectively, in both the cohorts (P = 0.1). Majority of the patients in both the cohorts had preoperative against-the-rule (ATR) astigmatism. The median change in SIA at the three-month postoperative visit was similar in both the cohorts, with a small increase in ATR astigmatism. Although the SIA change measured by keratometry in the J0 component was similar in both the groups (P = 0.54), that of J45 was significantly different (P = 0.01). However, the median change in SIA was similar in both the groups for both the J0 (P = 0.52) and J45 components (P = 0.94) when measured by Orbscan. The SIA in both the groups measured with keratometry (P = 0.62) and topography (P = 0.52) were clinically and statistically similar. In both the groups, the refraction was similar at 1 month and 3 months.

Conclusion

The SIA as measured with keratometry and topography was similar in the single-site and twin-site phacotrabeculectomy cohorts at the end of 3-months. The postoperative refraction was stabilized in 1-month in both the groups.

Minimizing surgically induced astigmatism in non-phaco manual small incision cataract surgery by U-shaped modification of scleral incision

Purpose:

To evaluate the amount and type of surgically induced astigmatism (SIA) in manual small incision cataract surgery (SICS) with a 4.5 mm U-shaped scleral incision.

Methods:

A prospective cross-sectional study was done on a total of 61 patients above 40 years of age with senile cataract. All patients underwent complete examination including preoperative uncorrected visual acuity (UCVA), refraction, best-corrected visual acuity (BCVA), and keratometry using a manual keratometer (Bausch and Lomb). All 61 patients underwent manual SICS with a 4.5 mm U-shaped scleral incision within the astigmatic neutral incisional funnel. Patients were thoroughly examined on immediate postoperative day 1 and findings of UCVA, BCVA, refraction, and keratometry were noted at the end of the 1^st week, 4^th week, and 6^th week follow-up visits. SIA was calculated for all the follow-ups using the SIA calculator version 2.1, a free software program. The changes in the amount and type of postoperative SIA were tested for statistical significance using Fischer's exact test. Variance was tested using intraclass score effect. The threshold for statistical significance was set to P < 0.001.

Results:

Postoperatively, the average SIA was 0.43 ± 0.13 D at the end of 1^st week, 0.29 ± 0.20 D at the end of the 4^th week, and remained the same 0.29 ± 0.21 D at the end of 6^th week. The type of astigmatism shifted more towards against-the-rule (ATR) type in 45.9% of cases during the final postoperative follow-up.

Conclusion:

In our study, we conclude that the incision within the funnel of astigmatic neutralization is one of the major determinants of SIA in manual SICS. We were able to achieve phacocomparable SIA in our study mainly because of our type of incision.

Surgically induced astigmatism in canines following sutured dorsonasal vs dorsotemporal clear corneal incisions

OBJECTIVES

To investigate use of the Pentacam® HR for evaluation of surgically induced corneal astigmatism (SIA) in canines undergoing bilateral phacoemulsification and determine differences between dorsonasal and dorsotemporal clear corneal incisions.

ANIMALS

Client-owned canines undergoing bilateral phacoemulsification.

PROCEDURES

Patients received anterior segment imaging pre-operatively, immediately post-operatively, and 2-4 months post-operatively (follow-up). Total corneal refractive power was used to determine SIA. Surgically induced astigmatism was compared between right and left eyes, representing dorsotemporal and dorsonasal incisions, respectively. Repeated measures analyses were used between time points and paired t test compared SIA between eyes.

RESULTS

Complete imaging series were obtained for seven patients. Follow-up imaging occurred at a median of 112 days (range 60-132 days) post-operatively. For repeated measures analyses, significant differences were found between pre- and immediate post-operative values (P < 0.01), and between immediate post-operative and follow-up values (P < 0.01). There was no significant difference between pre-operative and follow-up values. Surgically induced astigmatism was significantly different between right and left eyes, with values of 2.01 ± 1.24 D and 3.05 ± 1.58 D at 3 mm radius (P < 0.05), and 2.04 ± 1.18 D and 3.06 ± 1.27 D at 4 mm radius (P < 0.05) for dorsotemporal and dorsonasal incisions, respectively.

CONCLUSIONS

Preliminary investigation revealed improvement of corneal SIA 2-4 months post-operatively, but development of significantly more SIA in dorsonasal vs dorsotemporal incisions. This prompts consideration of patient or microscope rotation to create a more dorsotemporal incision when possible.

Axial Length Shortening After Cataract Surgery: New Approach to Solve the Question

Purpose

To check if optical biometry can detect eventual corneal power (Km) and axial length (AL) cataract surgery-related changes that could influence the refractive outcome.

Methods

Patients scheduled for sequential bilateral cataract surgery between January and September 2017 were included in the present study. One hundred ninety-six eyes of 98 patients (48 males) were selected. Before surgery of the first eye, patients underwent a complete ophthalmic examination, including IOLMaster biometry; the same evaluations were repeated in both eyes the day before the fellow eye cataract surgery, performed at least 2 months after the first one. The differences in Km and AL in the first operated eyes were evaluated, and the fellow eyes were used as controls.

Results

Km differences in the operated eyes ranged from −1.97 to +0.98 diopter (D) (mean = −0.02 ± 0.36 D) (P = 0.89); in the nonoperated eyes they ranged from −0.6 to +0.7 D (mean = 0 ± 0.20 D) (P = 0.91). The AL differences (pseudophakic option) in the operated eyes ranged from −0.35 to +0.15 mm (mean = −0.10 ± 0.08 mm) (P < 0.001); with the aphakic option they ranged from −0.24 to + 0.26 mm (mean = 0.01 ± 0.08 mm) (P= 0.38). In the nonoperated eyes, the AL differences ranged from −0.04 to +0.06 mm (mean= 0 ± 0.02 mm) (P = 0.02).

Conclusions

The modern phaco-technique seems not to induce changes in Km and AL, supporting the hypothesis that the differences in AL are due to an incorrect estimation in pseudophakic eyes.

Translational Relevance

The results of our study may improve the AL measurements in pseudophakic eyes.

Postoperative Corneal and Surgically Induced Astigmatism following Superior Approach Manual Small Incision Cataract Surgery in Patients with Preoperative Against-the-Rule Astigmatism

The aim of the study was to report postoperative corneal and surgically induced astigmatism (SIA) in patients with preoperative against-the-rule (ATR) astigmatism who underwent superior approach manual small incision cataract surgery (MSICS). 58 eyes of 58 cataract patients with preoperative ATR astigmatism were involved in this study. All patients had operable cataracts and underwent superior approach MSICS. Keratometric (K) readings were taken prior to surgery and at 12 weeks after surgery. Centroid values of SIA, preoperative astigmatism, and postoperative astigmatism were calculated using Cartesian coordinates based analysis. Wilcoxon signed rank test was used to compute statistical significance between mean preoperative and postoperative corneal astigmatism. Cohen's d was used as effect size measure. Centroid values of 1.42 D × 179, 2.48 D × 0, and 1.07 D × 1 were recorded, respectively, for preoperative astigmatism, postoperative astigmatism, and SIA. Wilcoxon signed rank test indicated that mean ± SD postoperative corneal astigmatism (2.80 ± 1.40 D) was statistically significantly greater than preoperative corneal astigmatism (1.49 ± 1.34 D), Z = −6.263, p < 0.0001. A high Cohen's d of 1.32 was found. Our results suggest statistical and clinically significant greater postoperative corneal astigmatism than preoperative corneal astigmatism for ATR astigmatism cataract patients who underwent superior approach MSICS.