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Abstract #12733 Published in IGR 7-3
Prevalence of oblique insertion of the arcuate nerve fibre layer bundle in normal eyes and its influence on GDx parameters
Raju P; Arvind H; George R; Ve Ramesh S; Baskaran M; Vijaya LAsian Journal of Ophthalmology 2005; 7: 91-95
AIM: Anatomical variations of the retinal nerve fibre layer are known to influence GDx parameters, but have not been extensively studied. The aim of this study was to assess the prevalence of oblique insertion of the temporal arcuate retinal nerve fibre bundle at the optic disc and its influence on GDx parameters. PATIENTS AND METHODS: 463 healthy eyes of 234 participants underwent complete ophthalmic examination, including scanning laser polarimetry by GDx. Participants with optic nerve pathology, tilted discs, or split nerve fibre bundles were excluded. The retardation images of the symmetry analysis printouts were analysed by 2 masked observers for oblique or normal insertion of the temporal arcuate nerve fibre bundle, which was confirmed using actual thickness values. An oblique insertion was defined as an arcuate bundle, one-third or more of which crossed the nasal or temporal demarcation lines. A control group of 25 eyes with normal insertion (defined as those in which the bundles lay entirely within the demarcation lines) was selected for comparison. GDx parameters were compared between the groups using Student's t test. RESULTS: Sixteen eyes (3.46%) had oblique insertion in the superior quadrant, and 7 (1.51%) in the inferior quadrant. Superior, inferior, and superior/nasal ratios, maximum modulation, nasal and temporal averages, and nasal and temporal medians differed significantly between those eyes with oblique insertion of the nerve fibre bundles and those with normal insertion (p ≤ 0.001). CONCLUSIONS: Oblique insertion of the temporal arcuate retinal nerve fibre bundle was found in 4.97% of eyes. Significant changes in GDx parameters were noted in eyes with oblique insertion, which may lead to misinterpretation of a healthy eye as glaucomatous. Hence, GDx parameters in patients noted to have oblique insertion of the temporal arcuate retinal nerve fibre bundle need to be interpreted with caution.
Dr. L. Vijaya, Vision Research Foundation, 18 College Road, Chennai 600 006, India
Classification:
6.9.1 Laser scanning (Part of: 6 Clinical examination methods > 6.9 Computerized image analysis)