Optical coherence tomography measurement of retinal nerve fibre layer thickness and comparison with visual field analysis in patients with primary open angle glaucoma

INTRODUCTION: Glaucoma is among the leading causes of irreversible blindness in the developing world and a major health problem in the developed world. World Health Organisation statistics indicate that glaucoma accounts for blindness in 5.1 million persons, or 13.5% of global blindness. Primary open angle glaucoma is explicitly characterized as a “multifactorial optic neuropathy with a characteristic acquired loss of optic nerve fibres”, developing in the presence of open anterior chamber angles and manifesting characteristic visual field abnormalities in the absence of other known causes of the disease. AIMS AND OBJECTIVES: PURPOSE To quantitatively assess the retinal peripapillary nerve fibre layer using optical coherence tomography and compare with standard automated perimetry in eyes with primary open angle glaucoma. AIMS: • To quantitatively assess the retinal peripapillary nerve fibre layer in eyes with primary open glaucoma and evaluate its efficacy in diagnosing glaucoma • To correlate the retinal nerve fibre layer thickness with a diagnostic gold standard, in this case standard automated perimetry by Humphrey’s visual field analyser • To compare the efficacy of each of these investigations in diagnosing primary open angle glaucoma. • To investigate the agreement in glaucomatous damage detection between structural changes by OCT and functional alteration by automated perimetry. MATERIALS AND METHODS: A prospective study to quantitatively measure the peripapillary retinal nerve fibre layer using optical coherence tomography and compare it with standard automated perimetry using Humphrey visual field analyser in patients with primary open angle glaucoma was undertaken in the Department of Glaucoma Services, Aravind Eye Hospitals, Madurai. The study was conducted for a period of two years from1st July 2003 to 31st July 2005 during which time 76 eyes of 38 patients were studied and analysed. SUBJECTS - INCLUSION CRITERIA: Best corrected visual acuity of at least 6/12 or better Age < 60 years Patients diagnosed with Primary open angle glaucoma at the time of diagnosis or after investigation Open angles (angle grading >2 by Shaffer’s system) Patients cooperative for visual field analysis and OCT Refractive errors Myopia < -5D Hypermetropia < +3.5D Astigmatism < 2D EXCLUSION CRITERIA: Age > 60 years of age Closed angles by Gonioscopy Media opacities – cataractous lenticular changes, vitreous haemorrhage, corneal edema/ opacity - which preclude examination of the posterior segment Retinal pathology – advanced diabetic retinopathy, age related macular degeneration, retinitis pigmentosa, maculopathy. All secondary glaucomas All juvenile glaucomas All subjects had a complete ophthalmologic examination including thorough slit lamp examination, Gonioscopy, dilated direct and indirect ophthalmoscopy, intra ocular pressure measurement using Goldmann Applanation tonometry, central corneal thickness measurement and refraction. DISCUSSION AND CONCLUSION: This study was done to evaluate a relatively new diagnostic modality – the Optical coherence tomography in the diagnosis and management of Primary Open Angle Glaucoma (POAG). To achieve this we evaluated the association between functional findings as determined by perimetry, and structural findings as measured by OCT Peripapillary Nerve Fibre Layer (NFL) thickness. The assessment also included the correlation of OCT NFL measurements with ophthalmoscopically visible optic nerve head changes. The current study shows significant agreement of peripapillary NFL thinning measured by OCT and detection of glaucomatous optic nerve head changes by dilated slit lamp biomicroscopic fundus evaluation (p