Abstract
Abstract: :
Purpose: To evaluate structural asymmetry in the macula using optical coherence tomography (OCT) in glaucomatous eyes with visual field defects localized to one hemifield. Methods: Complete examination, automated achromatic perimetry (AAP), and OCT imaging (512 A–scans) of the peripapillary retina and macula were performed. Exclusion criteria were visual acuity > 20/40, diseases other than glaucoma, and AAP defects localized to both hemifields. Macular OCT images were obtained using four 5 mm radial scans centered on the foveola and passing obliquely through the macula (15 and 30 degrees superotemporally and inferotemporally). RNFL OCT images were obtained using a circular scan (3.4 mm diameter) centered on the optic disc. Macular measurements temporal to the fovea (zone 1) were further sub–divided into nasal (zone 2) and temporal (zone 3) segments and macular symmetry testing (MST) was performed by comparing corresponding segments in the glaucomatous and normal hemifields. Results: 40 eyes of 40 patients (20 normal, 20 glaucomatous) were enrolled (mean age 60 ± 19 years, range 21–89). All eyes with glaucoma had associated hemifield defect (average MD = –7.23 ± 4.8 dB, range –0.9 to –15.4). Mean RNFL thickness was significantly (P = 0.001) reduced in the glaucomatous hemifield (49.6 ± 15.9µm) compared to the normal hemifield (64.7 ± 18.9µm). Mean retinal thickness in the glaucomatous segments (15 degree scan) of zones 1, 2 and 3 (222.3 ± 13.8µm, 223.9 ± 16.6µm, 220.7 ± 13.5µm respectively) were significantly less (P = 0.002, P = 0.004, P = 0.001 respectively) than the corresponding zones in the normal macular hemifield (234.9 ± 16.7µm, 236.8 ± 18.4µm, 233.3 ± 17.0µm respectively). Conclusions: The MST is a surrogate indicator of localized retinal ganglion cell loss and represents a novel strategy for detection and monitoring of glaucomatous structural damage.
Keywords: imaging/image analysis: clinical • imaging methods (CT, FA, ICG, MRI, OCT, RTA, S • nerve fiber layer