Preoperative Biometry and Uncorrected Visual Outcome Following Cataract Surgery at a Teaching Hospital at Western Part of Nepal

Introduction: Proper preoperative biometry in cataract surgery provides expected postoperative uncorrected visual outcome. Astigmatism is one of the major problems to achieve best postoperative unaided visual acuity. Aims: To determine the distribution of biometric parameter and unaided visual outcome in the cataract patients operated at Nepalgunj medical college, Banke, Nepal. Methods: The patients who underwent cataract surgery between January 2019 and December 2020 at Nepalgunj medical college were studied. Patient’s demographic parameter, keratometric value, anterior chamber depth, lens thickness and axial length data, type of surgery, preoperative and post-operative visual acuity and other clinical details were collected and analyzed. Results: This study enrolled 261 eyes of 261 patients who had undergone cataract surgery. The mean age of patients was 60.8 ± 14.62 years. The mean corneal astigmatism was 1.30±1.43 D. Corneal astigmatism was higher than 1.00 D in almost 40% of cases. With-therule astigmatism was the most common type (46.4%) of astigmatism observed in this study. The mean average keratometry was 44.83±2.05 D. The mean preoperative LogMAR VA of 1.52±0.83 improved to 0.48 ± 0.48 postoperatively without statistically significant differences between manual small incision cataract surgery and phacoemulsification technique (p=0.496). Conclusion: The biometric data helps to improve surgical procedure and select most appropriate intraocular lens to attain maximal postoperative uncorrected visual acuity following cataract surgery. This study found superior convention incision is better for cataract surgery with equivalent visual outcome following manual small incision cataract surgery and phacoemulsification.

Effect of Trabeculectomy on Mean and Centroid Surgically Induced Astigmatism

This study aimed to investigate the arithmetic mean of surgically induced astigmatism (M-SIA) and the centroid of surgically induced astigmatism (C-SIA) after standard trabeculectomy. We comprised 185 eyes of 143 consecutive patients (mean age ± standard deviation, 67.7 ± 11.6 years) who underwent trabeculectomy and completed at least a 3-month routine follow-up. In all cases, the scleral flap was made at the nasal-superior location. Corneal astigmatism was measured with an automated keratometer. We calculated the M-SIA and the C-SIA using vector analysis and applied the astigmatism double angle plot. The magnitude of corneal astigmatism increased significantly, from 1.17 ± 0.92 D preoperatively to 1.77 ± 1.05 D postoperatively (paired t-test, p < 0.001). The M-SIA was 1.12 ± 0.55 D, and the C-SIA was 0.73 D @64° ± 1.02 D in the right eye group, and the M-SIA was 1.08 ± 0.48 D and the C-SIA was 0.60 D @117° ± 1.03 D in the left eye group. The C-SIA showed an astigmatic shift toward the nasal-superior location of the scleral flap creation. Our results revealed that trabeculectomy induced the SIA in the direction of the scleral flap location and that the C-SIA was much lower than the M-SIA in eyes undergoing trabeculectomy.

Combination of Violet Light Irradiation and Collagenase Treatments in a Rabbit Model of Keratoconus

Purpose: We evaluated the use of collagenase treatment to generate a rabbit model of keratoconus and the impact of violet light (VL) irradiation on the disease model in six Japanese White rabbits. Methods: After epithelial debridement, the collagenase group was treated with a collagenase type II solution for 30 min; the control group was treated with a solution without collagenase. Three rabbits also underwent VL irradiation (375 nm, irradiance 310 μW/cm2) for 3 hours daily for 7 days after topical collagenase application. Slit-lamp microscopy results, steep keratometry (Ks), corneal astigmatism, central corneal thickness, and axial length were examined before and after the procedure. The corneas were obtained on day 7 for biomechanical evaluation. Results: A significant increase in Ks and corneal astigmatism was observed in the collagenase and VL irradiation groups compared with the control group at day 7. No significant difference was found in the change in corneal thickness between the groups. The elastic modulus at 10% strain, but not at 3% and 5% strain, was significantly lower in the collagenase group than in the control group. There was no significant difference in the elastic modulus at each level of strain between the collagenase and VL irradiation groups. The average axial length at day 7 was significantly longer in the collagenase group than in the control group. Collagenase treatment induced a keratoconic model by steepening the keratometric and astigmatic values. There was no significant difference in the observed elastic behaviour of normal and ectatic corneas under physiologically relevant stress levels. Conclusion: VL irradiation did not cause regression of corneal steepening in collagenase-induced model during short-term observation.

Toric Intraocular Lenses for the Management of Corneal Astigmatism at the Time of Cataract Surgery

Aims/Background. To assess astigmatic outcomes with the use of toric intraocular lenses (IOLs) for patients with significant amounts of corneal astigmatism undergoing cataract surgery. Methods. This audit was conducted in a UK ophthalmology department and included 48 eyes of 42 patients. Surgery was performed during 2019 in patients with 2.50 diopters (D) or more corneal astigmatism. Anterior keratometry readings were used to determine the toric IOL power. Vector analysis using the Alpins method was used to assess changes in astigmatism pre to postoperatively. Results. There were 18 right and 26 left eyes included. In terms of gender, 61% of patients were female and 39% were male. The mean (±standard deviation (SD)) age was 70 (±11) years. The mean (±SD) axial length, K1, K2, and delta K was 23.55 (±1.4) mm, 42.71 (±1.39) D, 45.78 (±1.60) D, and 3.01 (±0.89) D, respectively. Postoperatively, the median spherical, cylinder, and spherical equivalent refraction was 0.00 D, −1.00 D, and 0.00 D, respectively. Postoperatively, 41% of the eyes had ≤0.50 D of spectacle astigmatism and 80% had ≤1.00 D. No patient required a secondary procedure to reposition the IOL from rotation. In vector analysis with the use of polar diagrams, there was a tendency for overcorrection of with-the-rule astigmatism and undercorrection of against-the-rule astigmatism. Conclusions. Significant reductions in astigmatism can be achieved with the use of toric IOLs in patients undergoing cataract surgery. Further improvements may be possible with surgeon-specific determination of their surgically induced astigmatism and flattening effect from the main corneal incision. Furthermore, the use of an optical biometer that directly measures the posterior corneal curvature and permits automatic toric IOL power determination with modern formulas avoiding the need for manual data entry may reduce the risk of human error and improve visual and refractive outcomes.

Astigmatism Correction during Femtosecond Laser-assisted Transepithelial Arcuate Keratotomy Using the Wound Open Method

Purpose: The purpose of this study was to compare corneal astigmatism correction between “wound open” and “wound intact” methods during femtosecond laser-assisted transepithelial arcuate keratotomy.Methods: From April 2016 to December 2018, a retrospective survey was conducted on patients undergoing femtosecond laser cataract surgery at the Ophthalmology Department of Samsung Medical Center. Size comparison and vector analysis of corneal astigmatism before and after surgery were performed in the wound open and wound intact groups.Results: In the wound open and wound intact groups, the target-induced astigmatism (TIA) was 1.28 ± 0.55; and 1.26 ± 0.29 diopters, the surgically induced astigmatism (SIA) was 0.80 ± 0.52; and 0.53 ± 0.32 diopters, and the correction index (CI) was 0.63 ± 0.28; and 0.43 ± 0.26, respectively. The astigmatism correction was superior in the wound open group (p = 0.048, p = 0.025). In a subgroup with TIA < 1.2 diopters, there were no significant differences in SIA or CI between the two groups; however, in the subgroup with a TIA > 1.2 diopters, the SIA was 1.09 ± 0.59; and 0.54 ± 0.37 diopters and the CI was 0.60 ± 0.28; and 0.36 ± 0.23 in the wound open and wound intact groups, respectively (p = 0.022, p = 0.047). Thus, astigmatism correction was superior in the wound open group.Conclusions: The wound open method during femtosecond laser-assisted transepithelial arcuate keratotomy was superior for astigmatism correction compared to the wound intact method.

Impact of Ocular Residual Astigmatism On Anterior Corneal Astigmatism In Children With Low And Moderate Myopia

Background: To assess the influence of ocular residual astigmatism to anterior corneal astigmatism in children with low and moderate myopia.Methods: Refractive astigmatism was obtained by subjective manifest refraction. Anterior corneal astigmatism was obtained by IOL Master. Using Thibos vector analysis to calculate ocular residual astigmatism. Correlation analysis was used to assess the relationship between the magnitude of ocular residual astigmatism and anterior corneal astigmatism. The influence of ocular residual astigmatism to anterior corneal astigmatism was evaluated by Physical method.Results: The study analyzed 241 right eyes of 241 children aged 8 to 18 years old. In this study, the median magnitude of ocular residual astigmatism was 1.02 D, with interquartile range was 0.58 D. Against-the-rule ocular residual astigmatism was seen in 232 eyes (96.3%). There was a significant and moderate correlation between ocular residual astigmatism and anterior corneal astigmatism (r = 0.50, P < 0.001). The ocular residual astigmatism in 240 eyes (99.6%) had a compensatory effects on anterior corneal astigmatism. The mean compensation value was 1.00 ± 0.41 D (rang 0.02 D to 2.34 D). Based on this effect, 37 eyes had different axial classification of anterior corneal astigmatism and refractive astigmatism. By contrast, one eye (0.4%) had oblique ocular residual astigmatism and superimposed with-the-rule anterior corneal astigmatism.Conclusions: The magnitude of ocular residual astigmatism was relatively huge in myopia children and predominantly compensated anterior corneal astigmatism. The ocular residual astigmatism should be assessed first before fitting orthokeratology.

Correction of Pre-Existing Astigmatism with Phacoemulsification Using Spherical Intraocular Lens and Wave front Guided Surface Ablation: A Retrospective Case Series

Objective: To evaluate safety and efficacy of using spherical intraocular lens followed by wavefront guided surface ablation in correction of preexisting regular corneal astigmatism. Methods: This retrospective case series study included 20 eyes of 16 patients having visually significant cataracts and co-existing regular corneal astigmatism. The patients underwent phacoemulsification with spherical intraocular lens and wavefront guided PRK three months later. Results: There was a statistically significant difference for Uncorrected Visual Acuity UCVA, Best Corrected Visual Acuity BCVA, Manifest Refraction Spherical Equivalent MRSE, and refractive astigmatism postoperatively regarding all these parameters (P˂0.05). Conclusion: Astigmatism correction during or even after cataract surgery is a safe and effective method to improve visual outcomes. Longer period of follow up are required to evaluate stability of this technique and possibility of regression.

Comparison between the change in total corneal astigmatism and actual change in refractive astigmatism in transepithelial photorefractive keratectomy (tPRK), laser in situ keratomileusis (LASIK) and femtosecond laser assisted laser in situ keratomileusis (FsLASIK)

Purpose To compare changes in astigmatism by refraction and total corneal astigmatism after tPRK, LASIK and FsLASIK. Setting Specialty Eye Hospital Svjetlost, Zagreb, Croatia. Design Partially masked, semi-randomized, prospective, case-by-case, interventional, clinical study. Methods Patients with a stable refraction (-0.75DS to −8.00DS, astigmatism ≤1.00DC) underwent tPRK, LASIK or FsLASIK without complication. Astigmatism was measured at both corneal surfaces over the central 3.2 mm zone (approximately using Pentacam HRTM) preoperatively and 3 months postoperatively. Pentacam and refraction data were subjected to vector analysis to calculate the surgically induced changes in i) total corneal astigmatism (SIATCA) ii) any astigmatism by refraction (SIAR) and the vectorial difference (DV) between SIATCA and SIAR. Results Reporting key findings (p < .01), there was a significant difference between mean SIATCA and SIAR powers after tPRK (75eyes) but not after LASIK (100eyes) or FsLASIK (100eyes). Mean (±sd,95% CIs) values for DV powers were, tPRK −1.13DC(±0.71, −1.29 to −0.97), LASIK −0.39DC(±0.23,-0.44 to −0.34), FsLASIK −0.55DC(±0.38,-0.62 to −0.47). The differences were significant. For the tPRK and FsLASIK cases, linear regression revealed significant associations between I) SIATCA (x) &DV (z) powers (tPRK z = 1.586x-0.179, r = 0.767, p < .01; FsLASIK z = 0.442x-0.303, r = .484,p < .01), II) sines of SIATCA (x1) &DV (z1) axes (tPRK, z1 = 0.523 × 1 + 0.394, r = .650,p < .01; FsLASIK z1 = 0.460 × 1-0.308, r = .465,p < .01). Conclusions tPRK is more prone to unintended changes in astigmatism. The difference between SIATCA & SIAR after tPRK or FsLASIK is mediated by SIATCA. Photoablating deeper regions of the cornea reduces the gap between SIATCA & SIAR.

1 year posterior corneal changes after Bowman Layer Transplant for keratoconus

Introduction To report the posterior corneal changes after Bowman Layer Transplant for keratoconus in a tertiary hospital in the UK. Methods 5 eyes of 5 patients receiving Bowman Layer Transplant for advanced keratoconus in Royal Gwent Hospital (Newport, UK) were included. Pre and postoperative posterior corneal astigmatism, posterior Kmean, and back surface elevation were analysed. Results No significant changes were seen in the posterior corneal astigmatism, posterior Kmean, or back surface elevation between the pre- and postoperative period. Conclusion This results would support the idea that the corneal changes seen after Bowman Layer Transplant are mainly in the anterior corneal surface.