EFFECT OF MYOPIC LASIK ON RETINAL NERVE FIBER LAYER THICKNESS- IS IT SAFE OR UNSAFE?

Transcription

1 24. Glaucoma: Imaging EFFECT OF MYOPIC LASIK ON RETINAL NERVE FIBER LAYER THICKNESS- IS IT SAFE OR UNSAFE? Chief Author: Dr. Amit porwal 1 Co-Authors: Dr. Kavita Porwal 2, Dr. Puja Rai 1 1. Choithram Netralaya, Indore, India. 2. Sanghvi Netralaya, Belgaum, India BACKGROUND Refractive surgery has been accepted for correcting ametropias; however these procedures may lead to complications. LASIK has become one of the most popular options for correction of low to moderate myopia worldwide. Posterior segment complications including posterior vitreous detachment, retinal tears, retinal detachments, macular edema, macular holes, retinal hemorrhages, and choroidal neovascular membranes have been reported in the past. LASIK has also been noted to have an effect on RNFL thickness in few studies. The purpose of this study was to evaluate the safety of LASIK on RNFL thickness of patients undergoing myopic LASIK.

2 METHODS This was a prospective, observational, case series. Data was collected over a period from June 2012 to September Patients attending the Department of cornea, Choithram Netralaya, Indore, from June 2012 to September 2013, diagnosed as myopia and were willing for LASIK were included. 108 eyes of 54 myopic patients were studied. OCT was performed through dilated pupils using Spectral Domain Cirrus Zeiss HD-OCT (4000) optic disk scans. Pre-operative and one month post-operative optic nerve cube images were taken by the same technician. Patients underwent wavefront guided LASIK on MEL 80 excimer laser (Carl Zeiss Meditech AG, Germany). Individual treatment planning was done using the CRS- Master. RESULTS: Out of the 54 patients enrolled, 4 patients were not included in study analysis because of poor OCT signals in OCT imaging. For the purpose of this study, they were not included in the analysis. Therefore, 100 eyes of 50 patients were included. The following tables highlight our results: Gender distribution Gender No. of patients Percentage (%) Male Female 29 58

3 Above table shows 42% (n=21) were males and 58% (n=29) of them were females, giving a Male: Female Ratio of 1:1.38. Gender distribution Male 42% Female 58% OCT changes in RNFL thickness and Central Macular thickness pre and post-lasik RNFL thickness (µ) Central subfield thickness (µ) Outer Ring Pre-operative Mean±SD Post-operative Mean±SD P value 92.62± ± ± ±

4 Superior (µ) ± ± Inferior (µ) 264.1± ± Nasal (µ) 298.3± ± Temporal (µ) ± ± Inner ring Superior (µ) 324± ± Inferior (µ) ± ± Nasal (µ) ± ± Temporal (µ) 303.2± ± The mean RNFL thickness of the 100 eyes pre and post-lasik was 92.62±9.41µ and 91.72±9.52µ respectively. The mean central subfield thickness pre and post-lasik was ±8.36µ and ±7.80µ respectively. The analysis of OCT measurements of RNFL and Central Subfield thickness as well as the inner and outer ring values indicate that there was no statistically significant difference between the pre and post-lasik values. (P>0.05, Student t test). DISCUSSION: The results at the end of the study suggested no significant effect of LASIK on the RNFL thickness at one month. This was consistent with the results of Choplin NT et al 1 [2005], Sharma N et al 2 [2006] and Hosny et al 3 [2013] who studied RNFL thickness using either scanning laser polarimetry or OCT. However Hlavacova P et al 4 [2007] differed and stated that statistically significant difference of the RNFL thickness at the 1% level of significance was found in the superior quadrant after 3 months and in the inferior quadrant after 3 and 6 months after LASIK. Yi-Yu Tsai et al [2000] showed that the postoperative averages were statistically significantly lower than the

5 preoperative values, except in the temporal quadrant. So LASIK did have a significant effect on RNFL thickness in their study. Feng L et al 6 in 2012 compared retinal measurements obtained by time domain optical coherence tomography (OCT) devices before and after myopic LASIK. Total macular volume (TMV) changed significantly between preoperative and postoperative measurements but the exact mechanism for this change could not be determined. However no statistical differences were found between preoperative and postoperative disc area, rim area, cup/disk vertical ratio, or average foveal thickness. CONCLUSION: Variable conclusions are made in different studies upon the topic of effect of LASIK on RNFL thickness. This calls for more research on the same with large sample sizes to have an effective answer to the question. However, we conclude that LASIK does not have a significant effect on the RNFL thickness of myopic eyes, as measured by SDOCT. Therefore myopic LASIK is safe for retinal nerve fibre layer. REFERENCES: 1. Choplin N, Schallhorn SC, Sinai M, Tanzer D, Tidwell JL, Zhou Q. Retinal nerve fiber layer measurements do not change after LASIK for high myopia as measured by scanning laser polarimetry with custom compensation. Ophthalmology 2005; 112: Sharma N, Sony P, Gupta A, Vajpayee RB. Effect of laser in situ keratomileusis and laser-assisted subepithelial keratectomy on retinal nerve fiber layer thickness. J Cataract Refract Surg 2006;32:446-50

6 3. Hosny M, Zaki RM, Ahmed RA, Khalil N, Mostafa HM. Changes in retinal nerve fibre layer thickness following mechanical microkeratome-assisted versus femtosecond laser-assisted LASIK. Clin Ophthalmol 2013; 7: Hlavacova P, Horackova M, Vlkova E, Goutaib M. the influence of LASIK to the retinal nerve fiber layer in myopia. Cesk Slov Oftalmol 2007; 63: Yi-Yu Tsai, Jane-Ming Lin. Effect of Laser Assisted in situ Keratomileusis on the retinal nerve fiber layer. Retina 2000; 20: Feng L, Burns SA, Shao L, Yang Y. Retinal measurements using time domain OCT imaging before and after myopic Lasik. Ophthalmic Physiol Opt 2012; 32: For any query contact: DR. AMIT PORWAL