Abstract
Purpose: :
1. To determine whether interocular retinal nerve fiber layer (RNFL) asymmetry correlates significantly with visual field asymmetry in a population of glaucoma patients and glaucoma suspects 2. To examine the correlation of age and RNFL thickness to interocular RNFL asymmetry.
Methods: :
Retrospective study of 79 patients (30 male, 49 female): 58 Glaucoma Suspects, 21 Primary Open Angle Glaucoma. All subjects tested on SITA-standard white on white SAP and Cirrus HD-OCT. Patients with unreliable visual fields were excluded.Main Outcome Measure: The RNFL symmetry score, obtained from the glaucoma analysis software found on the Cirrus OCT system, is the correlation coefficient, converted to a percentage, derived by comparing 256 points between the OD and OS profile (1). To determine visual field asymmetry, the mean deviation (MD) was obtained and the AGIS score was derived. The absolute values of the difference in mean deviations (|MDOD- MDOS|) were calculated. The absolute values of the difference in AGIS scores between the right and left eyes were calculated. These values were correlated with the Cirrus OCT Symmetry Parameter using the Pearson correlation coefficient and assessed for statistical significance.
Results: :
Interocular RNFL symmetry correlates significantly with measures of visual field asymmetry (differences in MD and AGIS) in a population consisting of glaucoma patients and glaucoma suspects (r: -0.48 (P<0.0001)). Interocular RNFL asymmetry correlates significantly with visual field asymmetry in glaucoma patients (r: -0.44 (P<0.05)), but not glaucoma suspects (r: 0.17 (P=0.20)). RNFL asymmetry does not appear to correlate with age (P=0.51), but RNFL asymmetry becomes greater as the RNFL becomes thinner (P<0.005).
Conclusions: :
Glaucoma suspects with full automated visual fields may vary widely in their interocular RNFL asymmetry. RNFL asymmetry values appear independent of interindividual variation from age. More research is needed to determine whether glaucoma suspects with greater RNFL asymmetry are more likely to develop glaucoma than suspects with symmetric nerve fiber layers.1. Cirrus HD-OCT User Manual, 2008 Carl Zeiss Meditec, Inc.
Keywords: imaging/image analysis: clinical • ganglion cells • nerve fiber layer