Nerve Fiber Layer Thickness in Glaucoma Patients With Asymmetric Visual Field Loss

Abstract

Abstract: : Purpose: To investigate the alterations in retinal nerve fiber layer (RNFL) thickness corresponding to hemifields with early and advanced glaucomatous visual field loss and determine the relationship between RNFL thickness and visual field sensitivity loss. Methods: Nineteen glaucoma patients with asymmetric hemifield visual field loss and 10 age matched normal control subjects were included in the study. RNFL thickness was measured using optical coherence tomography (OCT) and visual field sensitivity was measured using standard automated perimetry. Glaucoma patients with advanced field loss in one hemifield and no field loss in the other hemifield based on the pattern standard deviation plot were included. The hemifields with no loss of sensitivity on pattern deviation however did show some loss of sensitivity on the total deviation plot. The hemifields in each eye were categorized as early glaucomatous (mean deviation (MD) > – 6dB) and advanced glaucomatous (MD < – 6dB) hemifields. The mean RNFL thickness was measured in the superior and inferior quadrants. Visual field sensitivity and mean deviation were averaged separately in each of the 2 hemifields. Results: The hemifield MD in early glaucomatous hemifields (–2.8 + 2.6 dB) was significantly different than the advanced glaucomatous hemifields (–15.1 + 5.8 dB) (P < 0.001). RFNL thickness measured in corresponding advanced glaucomatous hemifields (61 + 14 microns) was significantly lower than the normal control hemifields (117 + 11 microns) (P < 0.001). RFNL thickness measured in corresponding early glaucomatous hemifields (90 + 25 microns) was significantly lower than in normal control hemifields (117 + 11 microns) (P = 0.003). RNFL thickness in corresponding advanced glaucomatous hemifields (61 + 14 microns) was significantly lower than in the early glaucomatous hemifields (90 + 25 microns; N =19) (P < 0.001). Based on the normative database supplied with the OCT software, 79% and 42% of glaucomatous eyes had abnormal (outside the 95% confidence interval) RNFL thickness in corresponding advanced and early glaucomatous hemifields, respectively. A linear relationship was noted between mean RNFL thickness and visual sensitivity in the superior (r = 0.7; P < 0.001) and inferior (r = 0.7; P = 0.002) hemifields. Conclusions: In glaucomatous eyes, corresponding RNFL thinning was present in hemifields with advanced visual field loss. RNFL thinning was also present in hemifields with no sensitivity loss on pattern deviation. A linear relationship was found between mean RNFL thickness and visual sensitivity loss in the superior and inferior hemifields.

Keywords: nerve fiber layer • visual fields