Refractive Outcome of Femtosecond Assisted Laser in situ Keratomileusis in 1564 cases of Myopia and Compound Myopic Astigmatism.

OBJECTIVE: To determine the outcomes of Femtosecond Assisted Laser in situ Keratomileusis (Femto LASIK) on eyes with myopia and compound myopic astigmatism in terms of efficacy, safety, accuracy, predictability, and stability of the procedure. STUDY DESIGN: Quasi-experimental study. Place and Duration of the Study: Refractive Surgical Department, Armed Forces Institute of Ophthalmology (AFIO), Rawalpindi, Pakistan, from January 2014 to August 2019. METHODOLOGY: Participants aged 18 years and above with upto -12D (dioptre of myopia, underwent preoperative detailed work-up with history, ocular examination, subjective refraction and assessment on topography, tomography, and aberrometry. Suitable candidates underwent Femto LASIK and were re-evaluated at 1st postoperative day, end of 1st week, 1 month, 3 months, 6 months and 1 year. Results were analysed and represented in form of standard graphs for refractive surgery.  Results: Postoperative UDVA (uncorrected distance visual acuity) of 20/40 was achieved in 99% of patients. Efficacy index was 1.02 + 0.15. Safety index was 1.04 + 0.199. None of the patients lost more than one line in postoperative CDVA (corrected distance visual acuity) when compared to preoperative CDVA. All the eyes (100%) were accurately treated within +1.0 DS of intended spherical equivalent (SEQ) range. Mean SEQ showed stability with 1% eyes recorded to have more than 0.5D change or more over 12 months. CONCLUSION: Femto LASIK is an effective, safe, accurate, predictable, and stable procedure for correction of myopia and compound myopic astigmatism. KEY WORDS: Femtosecond, Laser in situ Keratomileusis, Refractive surgery, Myopia, Compound myopic astigmatism, Uncorrected distance visual acuity.

Mechanical Epithelial Debridement versus Transepithelial Phototherapeutic Keratectomy Followed by Accelerated Corneal Collagen Crosslinking for Progressive Keratoconus.

OBJECTIVE: To compare the visual and topographic outcomes between mechanical epithelial debridement followed by accelerated corneal collagen cross linking (CXL) vs. transepithelial phototherapeutic keratectomy followed by accelerated CXL for treatment of progressive keratoconus. STUDY DESIGN: Quasi experimental study. Place and Duration of the Study: Armed Forces Institute of Ophthalmology (AFIO), National University of Medical Sciences, Rawalpindi, Pakistan, from December 2020 to December 2021. METHODOLOGY: On the basis of surgical technique used, patients were divided into two groups, Group A comprising of twenty eyes that underwent mechanical epithelial removal followed by accelerated CXL, and Group B comprising of twenty-two eyes that underwent transepithelial phototherapeutic keratectomy (t-PTK) followed by accelerated CXL. All variables were recorded preoperatively and 6 and 12 months postoperatively and included uncorrected visual acuity (UCVA), corrected distance visual acuity (CDVA), MRSE (manifest refraction spherical equivalent), and keratometric indices (flat K, steep K, Kmax , mean K, thinnest pachymetry, KPI, K prob, CLMIaa, and I-S). RESULTS: Forty-two eyes of twenty-nine patients were included in the study and were divided into two groups; Group A (mechanical epithelial removal followed by accelerated CXL) and Group B (t-PTK followed by accelerated CXL). The visual acuity improved in both the groups at 6 and 12 months, with more significant improvement in Group B in both UCVA (p=0.005) and CDVA (p=0.004) parameters. Keratometric outcomes showed significant differences in median values for flat K (p=0.048) and thinnest pachymetry (p=<0.001) in Group A, while significant difference in Kmax (p=0.024) and thinnest pachymetry (p=<0.001) in Group B. At 6 and 12 months, the CLMIaa, PPK, and I-S values were significantly lower in Group B (p=0.002 for all three indices). CONCLUSION: Transepithelial PTK followed by accelerated CXL yielded better outcomes regarding visual acuity and keratomertic indices as compared to mechanical epithelial removal followed by accelerated CXL and did not show any significant decrease in corneal pachymetry. KEY WORDS: Mechanical, Corneal Collagen Crosslinking (CXL), Transepithelial, Phototherapeutic keratectomy, Keratoconus.

Comparison of Higher Order Aberrations between Wavefront Optimized Photorefractive Keratectomy and Laser in situ Keratomileusis in Myopic Patients.

OBJECTIVE: To compare the higher order aberrations (HOA) between wavefront optimized (WFO) laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) in myopic patients. STUDY DESIGN: Quasi-experimental study. Place and Duration of the Study: Armed Forces Institute of Ophthalmology, Rawalpindi, Pakistan, from December 2021 to December 2022. METHODOLOGY: Forty-four patients underwent wavefront optimized PRK and fifty-seven patients underwent wavefront optimized LASIK. All variables were recorded before the procedure and at 1, 3, 6, and 12 months postoperatively and included uncorrected visual acuity (UCVA), corrected distance visual acuity (CDVA), root mean square (RMS) of HOAs, spherical aberration (SA), and coma aberration (CA). RESULTS: A total of 101 eyes of 51 patients were considered in the final analysis. Patients were divided into two groups. Group A comprised of 44 (43.6%) eyes of 22 patients who underwent PRK while group B comprised of 57 (56.4%) eyes of 29 patients who underwent LASIK. UCVA significantly improved postoperatively at 3 and 6 months in both PRK and LASIK groups (p<0.001 for both groups). In this study, the increase in root mean square (RMS) of higher order aberrations from baseline value was 77% after PRK and 28% after LASIK, similar ratio was observed in spherical aberration (SA). The trend of rise in Coma aberrations was more in LASIK group 66.49% as compared to 46.2% in PRK group. CONCLUSION: Both Wavefront Optimized PRK and LASIK are safe and have elicited comparable results of post-procedure visual recovery. There was a marked increase in RMS of HOAs in PRK group as compared to WFO LASIK group while coma aberration increased more in LASIK as compared to PRK postoperatively. KEY WORDS: LASIK, PRK, RMSh, HOAs, Spherical aberration, Coma, Myopia.

Assessment of Refractive Outcome of Photo Refractive Keratectomy in Myopia and Myopic Astigmatism.

OBJECTIVES: To determine the refractive outcomes of wavefront optimized photo refractive keratectomy (PRK) in patients having myopia and myopic astigmatism in terms of efficacy, safety, accuracy, stability and predictability of the procedure. STUDY DESIGN: Quasi-experimental study. PLACE AND DURATION OF STUDY: Refractive Surgical Unit, Armed Forces Institute of Ophthalmology, National University of Medical Sciences, Rawalpindi, Pakistan, from October 2013 to August 2018. METHODOLOGY: Patients having myopia and myopic astigmatism, consented to be a part of the study, underwent meticulous screening consisting of detailed medical history, ocular examination and investigations. Each case was compiled and evaluated. Those who satisfied the criteria for refractive surgery were subjected to PRK procedure. Postoperative follow-up was carried out and parameters were recorded at designated intervals of 1 week, 1, 3, 6 and 12 months. RESULTS: This study included 208 eyes of 106 patients with mean age of 25.33 + 5.196 years. At the end of one year, 97% (202 out of 208) eyes had uncorrected distance visual acuity (UDVA) better than 20/25 with efficacy index of 1.009 ± 0.132 and safety index of 1.019 ± 0.126. None of the eyes lost two or more lines. In this study, 207 out of 208 eyes remained within + 0.50 diopter (D) of intended spherical equivalent (SEQ). Results showed 100% accuracy of procedure since all the study patients achieved SEQ within + 1D. CONCLUSION: PRK is an effective, predictable, and safe treatment procedure for correcting myopia and myopic astigmatism. Key Words: Photorefractive keratectomy, Myopia, Refractive surgery, Myopic astigmatism, Uncorrected distance visual acuity.

Assessment of Refractive Outcomes of Femtosecond-assisted Laser in Situ Keratomileusis (LASIK) for Hyperopia.

OBJECTIVE: To determine the effect of refractive treatment in terms of safety, efficacy, stability, accuracy, and predictability with Wavefront Optimized Laser-assisted in situ keratomileusis (LASIK) on hyperopia. STUDY DESIGN: Descriptive, analytical study. PLACE AND DURATION OF STUDY: Armed Forces Institute of Ophthalmology, National University of Medical Sciences, Rawalpindi, Pakistan from August 2013 to June 2018.  Methodology: Participants were selected after detailed history, careful ocular examination and meticulous relevant assessment on refractive scans. Preoperative measurements were recorded. Refractive strategy was designed, considering individual requirements for each patient. Postoperative readings were taken at 1 day, 1 week, 1, 3, 6 and 12 months. RESULTS: A total of 54 patients participated with mean age of 28.07 + 8.13 years. Out of the 54 patients, 33 (61%) were males and 21 (39%) were females. Uncorrected distance visual acuity (UDVA) and Spherical equivalent (SEQ), which is algebraic sum of sphere and half of cylinder, were recorded pre- and postoperatively. These parameters were changed significantly at 12 months (p <0.001). SEQ reduced from 2.146 + 2.027 to 0.079 ± 0.269 Diopter (D) (p <0.001). UDVA improved from 0.672 ± 0.270 (20/93) to 0.153 ± 0.182 (20/28) (p <0.001). A total of 48 (out of 54) patients had uncorrected vision better than 20/40; and 49 patients showed either same or gain of Snellen lines when pre- and postoperative corrected distance visual acuity (CDVA) was compared. Two patients showed loss of two or more lines. All the patients had postoperative SEQ within + 1.0 D range. CONCLUSION: LASIK, performed to correct hyperopia, demonstrated satisfactory outcomes in terms of safety, efficacy, stability, accuracy, and predictability. LASIK is an effective treatment option for moderate (<6 D) hyperopia. Key Words: LASIK, Refractive surgery, Hyperopia, Spherical equivalent, Uncorrected distance visual acuity.

Screening Thresholds for the Corneal Tomography in Hyperopic Pakistani Population.

OBJECTIVE: To evaluate key corneal tomography parameters for screening mixed astigmatism and hyperopic males and females for refractive surgery and to compare the data to a previously studied myopic group in Pakistani population. STUDY DESIGN: Cross-sectional, observational study. PLACE AND DURATION OF STUDY: Armed Forces Institute of Ophthalmology AFIO, National University of Medical Sciences, Rawalpindi, Pakistan, from August 2013 to August 2018. METHODOLOGY: WaveLight Allegro Oculyzer II diagnostic device was used to examine eyes of 106 adult hyperopic patients in order to determine normal values of 20 parameters, which are considered most clinically applicable for refractive surgery screening. Kolmogorov-Smirnov test was used to evaluate normality of data. Results for outliers were displayed as 2.5%, 5%, 95% and 97.5% percentiles. RESULTS: Two hundred and nine eyes were examined; 110 men and 99 women with overall mean age of 31+11.7 years. Normal mean anterior segment values included: flat simulated keratometry (K1) 42.1±1.84 diopters (D), steep K2 43.8 ± 1.93 D, K maximum 44.4 ± 1.93 D, K mean 42.9 ± 1.75 D, astigmatism -1.3 ± 1.75 D, pachymetry at thinnest point 546.9 ± 33.3 um, front elevation at thinnest point 5.2 ± 3.47 um, and at the back was 14.1 ± 6.60 um, Ambrosio relational thickness maximum 472.0 ± 88.73, progression index (PI) maximum 1.2 ± 0.18, and anterior chamber depth (ACD) 2.7 ± 0.35 mm. CONCLUSION: Hyperopic patients had greater front and back elevation and pachymetry but lesser keratometry, anterior chamber depth and chamber volume as compared to myopic patients in Pakistani population. Front and back elevation data in this hyperopic study population was slightly higher than previously published studies. Key Words: Refractive surgery, Corneal tomography, Screening, Hyperope.

Screening Thresholds for the Corneal Tomography in a Myopic Pakistani Population.

OBJECTIVE: To evaluate key corneal tomography parameters for screening refractive surgery patients in Pakistani population. STUDY DESIGN: Cross-sectional, observation study. PLACE AND DURATION OF STUDY: Armed Forces Institute of Ophthalmology AFIO, National University of Medical Sciences, Rawalpindi, Pakistan, from August 2013 to December 2016. METHODOLOGY: Myopic patients were evaluated by two separate observers on Allegro OculyzerII (Wavelight) for normal ocular examination. A total of 20 tomographic parameters, used for pre-refractive surgical evaluation, were included. Normality of data was evaluated using Kolmogorov-Smirnov test. Results for outliers were displayed as 2.5%, 5%, 95% and 97.5% percentiles. RESULTS: The sample of 451 patients (895 eyes), comprised of 61% (n=277) females and 39% (n=174) males (39%). The mean age was 26 +6.4 years (range of 18-62 years, M=F). Normal mean anterior segment values included; flat simulated keratometry (K1) 42.9 ±1.44 diopters (D), steep K2 43.9 ±1.52 D, K mean 43.4 ±1.43 D, K maximum 44.6 ±1.56 D, astigmatism -0.96 ±0.97 D, anterior chamber depth (ACD) 3.19 ±0.28 mm, front elevation at the thinnest point 4.11 ±2.44 um, and that at the back was 7.56 ±4.52 um progression index (PI) maximum 1.14 ±0.17, Ambrosio relational thickness maximum (ART max) 487.5 ±89.0 and pachymetry at thinnest point 542.2 ± 31.1 um. CONCLUSION: The study demonstrates key corneal tomography parameters, which can be useful for screening refractive surgery patients in Pakistani population.

Transepithelial corneal crosslinking in treatment of progressive keratoconus: 12 months' clinical results.

OBJECTIVE: The purpose of this study was to evaluate the safety and efficacy of transepithelial corneal collagen cross linking (TE-CXL) with modified riboflavin and accelerated UVA irradiance in thin corneas with pachymetry less than 400 microns at thinnest point, untreatable by epithelium off corneal collagen cross linking (CXL) in adult Pakistani population with progressive keratoconus. METHODS: This quasi experimental study included twenty six eyes of 26 patients with progressive keratoconus who underwent accelerated transepithelial CXL in Armed forced institute of ophthalmology with 12 months follow up. Modified riboflavin, ParaCel ((riboflavin 0.25%, Benzalkonium chloride, EDTA, Trometamol, hydroxypropyl methylcellulose) and vibeX Xtra (riboflavin 0.25%) (Avedro, USA)) were applied to cornea in two stages. Uncorrected and Corrected Distant Visual Acuities (UDVA, CDVA), spherical equivalent (SE), astigmatism, pachymetry at thinnest point (Pachy thin), apex keratometry (Kmax), simulated and steep keratometry (Sim K, steep K) were measured at baseline and at 3, 6 and 12 months post operatively. The cornea was then exposed to accelerated UVA irradiance of 9mW/cm2 for 10 min (total dose 30 mW/cm2). RESULTS: The mean age of the patient was 24.54±5.16 years. UDVA, CDVA, SE, astigmatism significantly improved at all postoperative test points (p=0.000, 0.004, 0.000, 0.004 respectively). Kmax and pachy thin were significantly reduced over baseline at 1 year (p=0.000, 0.004 respectively). Topographic indices Sim K and steep K did not show significant changes. No intra or post-operative complications were reported. CONCLUSION: Transepithelial accelerated CXL with modified riboflavin is a safe and effective procedure which halt disease progression in thin corneas with progressive keratoconus.

Comparison of transepithelial corneal crosslinking with epithelium-off crosslinking (epithelium-off CXL) in adult Pakistani population with progressive keratoconus.

PURPOSE: The purpose of this study is to compare the safety and efficacy of transepithelial corneal crosslinking (CXL) with epithelium-off crosslinking (epithelium-off CXL) in the treatment of progressive keratoconus in adult Pakistani population. MATERIALS AND METHODS: Sixty-four eyes of 64 consecutive patients of progressive keratoconus were included in this quasi-experimental study. Thirty-two eyes received transepithelial CXL with Peschke TE (0.25% riboflavin (Vitamin B2), 1.2% hydroxypropyl methylcellulose (HPMC), 0.01% benzalkonium chloride) and 32 eyes received epithelium-off CXL with Peschke M (0.1% riboflavin (Vitamin B2) 0.1%, HPMC 1.1%.) The cornea was then exposed to ultraviolet A light at an irradiance of 3 mW/cm2 for 30 min. The primary outcome measure, clinical stabilization of keratoconus was defined as an increase of no more than 1D in Kmax at 1 year. Other parameters evaluated at baseline and 3, 6, 12, and 18 months postoperatively were uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), spherical equivalent (SE), astigmatism (Ast), simulated keratometry, steep keratmetry (steep K), and corneal thickness at thinnest point (pachy thin). RESULTS: Both epithelium-off CXL and transepithelial CXL groups showed a significant reduction in Kmax, steep K, simulated K, corneal pachymetry at all test points (P < 0.05) with significantly greater reductions achieved in epithelium-off CXL group at 18 months follow-up. The mean UDVA, CDVA, SE, Ast significantly improved in both groups (P < 0.05). The mean postoperative UDVA and CDVA between the groups were not significant at 12 months (P = 0.650, 0.018, respectively). Clinical stabilization was achieved in 94% of eyes in epithelium-off CXL and 75% of eyes in transepithelial CXL. In epithelium-off CXL, three eyes exhibited stromal haze resolved by corticosteroid treatment. No complication was documented in transepithelial CXL group. CONCLUSION: Transepithelial CXL is not recommended to be replaced completely by standard epithelium-off CXL due to continued ectatic progression in 25% of cases. However, thin corneas, unfit for standard epithelium-off CXL, can benefit from transepithelial CXL.

Effect of wavefront optimized LASIK on higher order aberrations in myopic patients.

OBJECTIVE: To determine mean change induced in root mean square value of higher order aberrations in myopic patients undergoing wavefront optimized laser assisted in situ keratomileusis. METHODS: This quasi experimental study was conducted at Armed Forces Institute of Ophthalmology, Rawalpindi, Pakistan from Jan 2014 to Dec 2014. Sixty eyes of 35 myopic patients were included in the study. All patients underwent wavefront optimized (WFO) laser assisted in situ keratomileusis (LASIK) using femtosecond laser (FM 200Wavelight technologies) and excimer laser (Ew 500Wavelight technologies). Higher order aberrations (HOAs) were measured with aberrometer (Wavelight allegro analyzer version 1073) during preoperative assessment and one month after surgery. RESULTS: All 35 patients ranged from 20 to 32 years with a mean age of 24 ± 3.41 years. Refractive error ranged from -1.00 to -9.50 DS with a mean spherical equivalent (SE) of -3.73 ± 1.95 before surgery and - 0.36 ± 1.50DS one month after LASIK. Uncorrected visual acuity (UCVA) was improved to 0.00 or better in all 60 eyes. An increase of 1.56 fold was observed in RMS of total HOAs. Among the HOAs, a statistically significant positive correlation was observed between spherical aberrations (4(th) order aberration) and preoperative spherical equivalent. CONCLUSION: In spite of excellent improvement in refractive error, significant amount of higher order aberrations were induced after WFO LASIK.

Comparison of higher order aberrations in patients with various refractive errors.

OBJECTIVE: To compare the mean root mean square (RMS) of total higher order aberrations (HOAs), coma and spherical aberrations in individuals with myopia, hypermetropia and myopic astigmatism. METHODS: This prospective analytical study was conducted at Armed Forces Institute of Ophthalmology, Rawalpindi, Pakistan from Jan 2014 to Dec 2014. Two hundred eyes of 121 patients with age ranging from 18-40 years were included in the study. Patients were divided into 4 group namely Low myopia, High myopia, Astigmatism and Hypermetropia on the basis of refractive error. Included were the patients who had refractive error more than ± 0.5D and best corrected visual acuity (BCVA) of 0.00 or better. Patients who had history of surgery and / or eye disease were excluded from the study. Visual acuity (VA), Spherical equivalent (SE) of refractive error, RMS value of total HOAs, coma and spherical aberrations were evaluated. HOAs were measured with aberrometer (Wavelight analyzer version 1073) at 6 mm pupil size. RESULTS: Age of the patients ranged from 18 years to 40 years with mean age of 29.10±10.6 years. Seventy one (35.5%) were males and 129 (64.5%) were female. Mean RMS value of HOAs, coma and spherical aberrations was calculated in all four groups. RMS of total HOAs and spherical aberrations in hypermetropia was 0.96±0.96 and 0.30±0.42 respectively and it was higher than other three groups. CONCLUSIONS: In overall comparison the mean RMS of total HOAs and spherical aberrations was significantly increased in hypermetropia group and there was a statistically significant negative correlation of SE of hypermetropia with RMS of total HOAs and spherical aberration.