Assessment and Alterations in Retinal nerve Fiber Layer Thickness before and following Glaucoma Filtration Surgery Using Optical Coherence Tomography: A Clinical Study

Abstract

Background: Retinal nerve fiber layer thickness is measured at a 3.5mm distance from the optic nerve head center. This thickness alteration is present even in absence of vision loss warranting continuous monitoring of the affected eyes. A high correlation is seen between alteration of retinal nerve fiber layer thickness and vision loss, allowing accurate assessment of progression of glaucoma. Aims: the present study was conducted to assess the alterations in RNFL (Retinal Nerve Fiber Layer) thickness and intraocular pressure following glaucoma filtration surgery. Materials and Methods: 36 subjects were evaluated from both genders and within the age range of 37-64 years and mean age of 53.82±12.94 years. For ocular examination, slit-lamp examination, tonometry, gonioscopy, and fundus examination were done. This was followed by the filtration surgery (trabeculectomy) where a tissue piece was removed in the drainage angle of the eye which made an opening at 0-4 months before and 2-4 months following Glaucoma filtration surgery along with intraocular pressure alteration. The collected data were subjected to the statistical evaluation. Results: Significant increase in RNFL thickness for overall quadrant and all individual quadrants (p<0.05). For the temporal quadrant, the RNFL thickness increased from 43.45±14.07 to 46.73±16.69 with p=0.067. In the inferior quadrant, it increased from 53.39±25.77 to 60.92±30.70 (p=0.002) and for the nasal quadrant, it was increased from 47.91±19.30 to 54.47±20.11 (p=0.007). For the overall quadrant, RNFL thickness increased from 52.58±17.38 to 58.50±20.18 with p=0.0001. For age >50 years and <50 years, RNFL thickness increased significantly for all age groups and intraocular pressure decreased significantly. In the present study, RNFL thickness was increased for both females and males with reduced intraocular pressure significantly (p<0.05). Conclusion: The present study concludes that RNFL thickness increase with a decrease in intraocular pressure following glaucoma filtration surgery. This increase in thickness was also seen with age and gender.