Retinal Nerve Fiber Layer Optical Texture Analysis

PURPOSE To apply retinal nerve fiber layer (RNFL) optical texture analysis (ROTA) to investigate the prevalence, patterns, and risk factors of RNFL defects in patients with ocular hypertension (OHT) who had normal optic disc and RNFL configuration in clinical examination, and normal optical coherence tomography (OCT) RNFL thickness analysis and visual field (VF) results. DESIGN Cross-sectional study. PARTICIPANTS 600 eyes of 306 patients with OHT METHODS All participants received clinical examination of the optic disc and RNFL, OCT RNFL imaging, and 24-2 standard automated perimetry. ROTA was applied to detect RNFL defects. The risk score for glaucoma development was calculated according to the Ocular Hypertension Treatment Study and European Glaucoma Prevention Study (OHTS-EGPS) risk prediction model. Risk factors associated with RNFL defects were analyzed using multilevel logistic regression analysis. MAIN OUTCOME MEASURES Prevalence of RNFL defects RESULTS The average intraocular pressure (IOP) measured from three separate visits within six months was 24.9±1.8 mmHg for the eye with higher IOP and 23.7±1.7 mmHg for the eye with lower IOP; the respective central corneal thickness was 568.7±30.8 μm and 568.8±31.2 μm. Of 306 patients with OHT, 10.8% (33 patients, 37 eyes) demonstrated RNFL defects in ROTA in at least one eye. Of the 37 eyes with RNFL defects, the superior arcuate bundle was the most frequently involved (62.2%), followed by the superior papillomacular bundle (27.0%), and the inferior papillomacular bundle (21.6%). 10.8% of eyes had papillofoveal bundle defects. The smallest RNFL defect spanned 0.0° along the Bruch's membrane opening margin, whereas the widest RNFL defect extended over 29.3°. Age (OR:1.08, 95% CI: 1.03-1.13), VF pattern standard deviation (OR:1.82, 95% CI: 1.01-3.29), and cup volume (OR:1.24, 95% CI: 1.01-1.53) were associated with RNFL defects. For each percentage increase in the OHTS-EGPS risk score, the odds of RNFL defects increased by 4% (95% CI: 1.01-1.07). CONCLUSION A considerable proportion of patients with OHT, who had no signs of optic disc and RNFL thickness abnormalities in clinical examination and OCT, showed RNFL defects in ROTA. Axonal fiber bundle defects in ROTA may represent the earliest discernible sign of glaucoma in the glaucoma continuum.