ABSTRACT
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
ABSTRACT
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/cm[2] for 10 min [total dose 30 mW/cm[2]]
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
ABSTRACT
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. 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. 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. 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
ABSTRACT
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. 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 SOOWavelight technologies]. Higher order aberrations [HOAs] were measured with aberrometer [Wavelight allegro analyzer version 1073] during preoperative assessment and one month after surgery. 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. In spite of excellent improvement in refractive error, significant amount of higher order aberrations were induced after WFO LASIK
ABSTRACT
To compare the effect of rapid and conventional methods of corneal collagen cross linking [CXL] on visual acuity [VA] and corneal parameters in Keratoconus. Randomized control trial. Armed Forces Institute of Ophthalmology, Feb 2012 to Apr 2013. Thirty patients, fifteen in each group, were randomized by non probability consecutive sampling to rapid or conventional CXL group. Pre and post operative [6 months] best corrected visual acuity [BCVA], anterior and posterior keratometric [K] values and pachymetry were recorded. Intra and inter group comparison of all these parameters were statistically analyzed. All thrty patients showed either stabilization or improvement in BCVA. Both groups showed comparable results in terms of improvement BCVA [p = 0.682], reduction in the corneal thickness at thinnest point [p = 0.062], anterior flat and steep K [p = 0.633, p = 0.443 respectively] and posterior flat and steep K values [p = 0.130, p = 0.068] at six months duration. Conventional and rapid methods of CXL are comparable in terms of their effect on VA and corneal parameters