Accuracy and predictability of novel MS Excel-based surgically induced astigmatism calculator

Study of steepening, flattening, clockwise, and counter-clockwise torque effect is indispensable to understand and design surgical induced astigmatism calculator. Hence, in this study by constructing a novel Microsoft Office Excel 2007 based astigmatic calculator following cataract surgery, analysis on the accuracy and predictability evaluated for the performance. Post-cataract surgery patients from May 2019 to January 2020 at a tertiary medical institution recruited for this present study. Based on Pythagoras principle, MS Excel calculator designed and the law of cousins for calculating the vector magnitude and axis respectively. Manual keratometry measurements for pre and postoperative horizontal (Kh) and vertical (Kv) curvatures established, and statistical analysis for the resultant SIA magnitude and axis deduced with Medcalc software comparing with the existing SIA 2.1 version calculator. A total of 29 eyes of 25 patients studied with a mean age of 62.55 (±8.08) years, males contributing to 14 (56%), and right laterally in 17 (58%) eyes. MS Excel and SIA 2.1 versions calculated a mean SIA magnitude of 0.66 (±0.47) D and 0.64 (±0.55) D respectively. Pearson coefficient correlation (r=-0.16, p=0.40), paired-two sample test (t value= 0.11, p= 0.91) and ROC curve analysis (AUC = 0.75, p= 0.34, 95% CI= 0.25 to 0.99) calculated. Regression equation (y = 0.75 + -0.14 x) and limits of agreements (95% CI -0.29 to 0.31) analyzed, and, 95% of data points distributed within ±1.96 SD of the line of equality on Bland-Altman difference plots.The present calculator proclaimed an acceptable accuracy and agreement with a prediction of 0.61 Diopter for every unit change in the magnitude of SIA 2.1 software in addition to consideration of interchangeability.

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.

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.

A COMPARATIVE PROSPECTIVE STUDY OF EFFICACY AND VISUAL OUTCOME OF PHACOEMULSIFICATION AND SICS IN NORTH INDIAN POPULATION IN AND AROUND LUCKNOW.

PURPOSE: To evaluate efcacy and visual outcome of manual small incision cataract surgery (SICS) and phacoemulsication. METHODS: A prospective, interventional, observational, follow up study was conducted on 120 patients with clinically signicant senile cataract undergoing cataract surgery by either SICS or phacoemulsication, at a tertiary eye care centre in Lucknow. The follow up evaluations were carried out at post-operative day st rd th 1, 1 week, 3 week and 6 week. RESULTS: On rst postoperative day, there was signicantly better visual outcome with phacoemulsication than SICS (p = 0.005) with 80% patients in SICS group and 90% patients in phacoemulsication group, th had best corrected visual acuity (BCVA) better than equal to 6/18. However at 6 week, nal visual recovery was similar in both the groups (BCVA 6/18 in 96.7% in SICS group and 100% in phacoemulsication group) with no statistically signicant difference. There was no signicant difference in overall per operative and post operative complications between SICS and phacoemulsication. SICS and phacoemulsication did not show signicant difference in surgery induced astigmatism (SIA) with SIA of 0.733D and 0.775D in SICS and phacoemulsication group respectively. CONCLUSIONS: Phacoemulsication is superior to SICS in terms of early visual rehabilitation. But there is no signicant difference in nal visual outcome and complication rates between the two techniques.

Posterior Corneal Asphericity Effect on Postoperative Astigmatism after EDOF Intraocular Lens Implantation in Cataract Patients

Aim. To assess the impact of posterior corneal asphericity on postoperative astigmatism. Methods. We included retrospectively 70 eyes of 70 patients that underwent cataract surgery. We included data of the Q value, Kmax, K1, K2, astigmatism AL, and ACD. We performed a vectorial analysis to calculate the astigmatic vectors. Results. Seventy eyes were evaluated. 40 eyes were of females (58%) and 30 of males (42%). The average cohort age was 73 ± 8.9 years. Axial length (AL) was 23.5 ± 0.9, anterior chamber depth (ACD) was 3.13 ± 0.3, and the average posterior Q value was −0.35 ± 0.2. The only significant predictive variable for the correction index (CI) was the posterior Q value (r = 0.24, p < 0.05) and for the surgically induced astigmatism (SIA) (β = 0.34, r = 0.58, p < 0.05). Conclusion. Posterior corneal surface asphericity significantly influences the surgically induced astigmatism and the overcorrection for cataract patients after Lucidis EDOF IOL implantation.

Vector Analysis of High Astigmatism (≥2.0 Diopters) Correction after Small-Incision Lenticule Extraction with Stringent Head Positioning and Femtosecond Laser-Assisted Laser in Situ Keratomileusis with Compensation of Cyclotorsion

PURPOSE： To compare the astigmatic correction by vector analysis in the high myopic astigmatism between femtosecond laser-assisted laser in situ keratomileusis with compensation of cyclotorsion (FS-LASIK) and small-incision lenticule extraction(SMILE) with stringent head positioning.SETTING: Beijing Aier-Intech Eye Hospital, Beijing, China.DESIGN: Retrospective case series. METHOD: Patients who had correction of myopic astigmatism of 2 diopters (D) or more had either FS-LASIK with compensation of cyclotorsion or SMILE with stringently control the head position were included. Results of vision and refraction were analyzed and compared between groups with the right eye.RESULT: The study enrolled 94 patients (41eye in the FS-LASIK with compensation of cyclotorsion and 53 eyes in SMILE with stringently control the head position). The mean preoperative manifest cylinder was -2.65±0.77D in FS-LASIK and 2.51±0.56D in SMILE group. (P=0.302). At 12-month, there was no significant difference between the two groups in uncorrected distance visual acuity (UDVA, P = 0.274) and postoperative spherical equivalent (P=0.107). 46.3% and 24.5% of eyes were within 0.25D post-op cylinder, 78% and 66% of eyes were within 0.5 D post-op cylinder for FS-LASIK group and SMILE group, respectively (P=0.027, P = 0.202). Vector analysis showed comparable target-induced astigmatism (TIA, P=0.114), surgically induced astigmatism vector (SIA, P=0.057), difference vector (DV, P=0.069) and the angle of error (AE, P=0 .213) between groups. Index of success (IOS) was 0.18 in the FS-LASIK and 0.24 in the SMILE (P=0.024), and significant difference for two groups.CONCLUSION: FS-LASIK with compensation of cyclotorsion had favorable correction in high myopic astigmatism (≥2.0 diopters) compared to SMILE with stringent head positioning at 12-month.

Comparison of surgically induced astigmatism between anterior and total cornea in 2.2 mm steep meridian incision cataract surgery

Background This study aimed to compare surgically induced astigmatism (SIA) on the anterior and total cornea during cataract surgery through a 2.2 mm steep meridian incision. Methods The study included 69 left eyes of 69 patients who had undergone cataract surgery. The 69 eyes were classified into three subgroups according to the preoperative steep meridian. Following phacoemulsification, an intraocular lens was inserted into the bag. The keratometric measurements were taken 12 months postoperatively, on the anterior cornea (automated keratometer and anterior keratometry [K] from a rotating Scheimpflug camera) and total cornea (equivalent K reading [EKR] 3.0 mm, EKR 4.5 mm, total corneal refractive power (TCRP) 2.0 mm ring, TCRP 3.0 mm zone, TCRP 4.0 mm zone). The SIA was analyzed for each parameter. Results On the double-angle polar plot, the summated vector mean values of SIA determined by the automated keratometer and Scheimpflug anterior K were 0.28 diopter (axis: 177°) and 0.37 diopter (axis: 175°) in with-the-rule (WTR) astigmatism; 0.03 diopter (axis: 156°) and 0.18 diopter (axis: 177°) in oblique astigmatism; 0.15 diopter (axis: 96°) and 0.17 diopter (axis: 73°) in against-the-rule (ATR) astigmatism. The mean SIAs on the total cornea ranged from 0.31 to 0.42 diopter in WTR astigmatism; from 0.16 to 0.27 diopter in oblique astigmatism; from 0.04 to 0.11 diopter in ATR astigmatism. Mean magnitude SIA ranged from 0.41 to 0.46 diopter on anterior corneal surface and 0.50 to 0.62 diopter on total cornea. J0 and J45 of the posterior cornea showed no significant changes after cataract surgery, and the changes in J0 and J45 did not show any statistical differences between the anterior and total cornea (all p > 0.05). Conclusions There were no differences in the summed vector mean values of SIA between the anterior cornea and the total cornea.

Relation between different grades of pterygium and amount of induced corneal astigmatism

Background: Pterygium is more prevalent among people exposed to ultraviolet (UV) light. It occurs more often in people who live in warm climates and spend a lot of time outdoors in sunny or windy environments. Objective: The objective of this study was to determine and the relation of different grade of pterygium with amount of induced corneal astigmatism. Methodology: This was observational study done in LRBT hospital Multan road LHR. A self-designed Performa was filled after clinically examining the patients. Frequency distribution/percentages of data were described, simple frequency tables and cross tables were formed to calculate the statistical results. Results: A total patients 50 with grades of pterygium and induce amount of astigmatism. There 31(62.0%) were male and 19(38.0%) were female and the mean age of the patient is 2.5. 21(42.0%) patients were grade 1 pterygium and 21(42.0%) patients were grade 2 and 8(16.0%) patents have grade 3 pterygium. The amount of astigmatism in grade 1 from 0.00 to 1.00 DC is 17(34.0%) patients, from 1.00 to 2.00 DC are 2(4.0%) patients and from 2.00 to 4.00 DC are 2 (4.0%). In grade 2 from 1.00 to 2.00 DC are 10(20.0%) patients, from 2.00 to 4.00 DC are 10(20.0%) patients and from greater than 4.00 DC 1(2.0%). In grade 3 from 1.00 to 2.00 DC are 2(4.0%) patients, from 2.00 to 4.00 DC are 4(8.0%) patients and from greater than 4.00 DC are 2(4.0%) patients. Conclusion(s): Result show that the present study verifies that as the pterygium reaches more than 1.00mm in size from the limbus it induce with the rule astigmatism and pterygium size increases, the amount of induced astigmatism also increases with direct proportion.

Analysis of the effect of intraocular lens tilt and decentration on induced astigmatism by ray tracing on the model eye

Purpose. Determination of the influence of the intraocular lens (IOL) inclination and decentration on the magnitude of induced astigmatism in a theoretical study using software on an eye model. Material and methods. An eye model with the specified parameters was performed to carry out the calculation. Modulation of the change in the wavefront was carried out using the Zemax program (LLC, USA). In the model eye, the probability of induction of astigmatism was analyzed depending on the change in the position of the aspherical IOL Acrysof IQ 16.0, 22.0 and 24.0 diopters and the toric model Acrysof IQ Toric SN6AT3, SN6AT4 and SN6AT5. The angle of inclination of the IOL relative to the horizontal plane was examined from 0° to 10° with a step of 1°, decentration from 0.1 to 1.5 mm with a step of 0.1 mm. At each IOL position, aberration data of the 2nd order Z (2, 2) were recorded. The obtained results were used to calculate the critical tilt angle and decentration. Results. The magnitude of induced astigmatism increased with the rise of the degree of inclination and decentration, corresponding to an increase in the optical power of the IOL. Accordingly, critically significant were the values of 3.0° inclination for the aspherical IOL with an optical power of 22.0 and 22.0 diopters and 3.5° for 16.0 diopters, decentration – 0.7 mm and 1.0 mm. The inclination of the TIOL relative to the horizontal plane revealed the induction of the magnitude of inverse astigmatism, according to an increase in the inclination angle of 0.3 diopters at a slope of 3–4°. Conclusions. The tilt and decentration of the aspherical and TIOL patterns induce astigmatism depending on the increase in IOL power. The inclination of the TIOL in relation to the horizontal plane set at 90 ° promotes the induction of astigmatism. Key words: astigmatism, toric intraocular lenses, tilt and decentration of the intraocular lens, ray tracing