Abstract
PurposeTo determine the interocular retinal nerve fiber layer (RNFL) thickness difference of normal subjects.MethodsBoth eyes of 230 normal adults received peripapillary RNFL thickness measurements using OCT. The effect of ocular cyclotorsion on the RNFL thickness profile was mathematically corrected. The fractional and absolute interocular RNFL thickness differences at 256 points of peripapillary area were calculated. We divided the subjects into 3 groups according to the locations of superior and inferior peak thickness, respectively, and compared the interocular RNFL thickness differences between the subgroups.ResultsThe fractional interocular RNFL thickness difference exhibited smaller regional variations than the absolute interocular difference. The means of fractional interocular differences were 0.100 ± 0.077 in the temporal half area and 0.146 ± 0.105 in the nasal half area, and the tolerance limits for the 95th and 99th distributions were about 0.246 and 0.344 in the temporal half area and 0.293 and 0.408 in the nasal half area, respectively. The fractional interocular differences of subgroups classified by the locations of superior and inferior peak RNFL thickness showed difference at smaller areas than the absolute interocular differences (19 and 8 points versus 49 and 23 points, respectively).ConclusionGlaucoma can be strongly suspected, if interocular fractional RNFL thickness difference is over 25% at 5 consecutive points or over 35% at 3 consecutive points in the temporal half area. The fractional interocular comparison is a better diagnostic approach because the fractional interocular RNFL thickness difference is less influenced by the locations of peak RNFL thickness.
Highlights
Diagnosing glaucoma using OCT usually consists of comparing retinal nerve fiber layer (RNFL) thickness of a patient to the built-in normative RNFL thickness, and the normative RNFL thickness usually has its peak RNFL thickness at the 11 and 7 o’clock position
The fractional interocular differences of subgroups classified by the locations of superior and inferior peak RNFL thickness showed difference at smaller areas than the absolute interocular differences (19 and 8 points versus 49 and 23 points, respectively)
Glaucoma can be strongly suspected, if interocular fractional RNFL thickness difference is over 25% at 5 consecutive points or over 35% at 3 consecutive points in the temporal half area
Summary
Diagnosing glaucoma using OCT usually consists of comparing retinal nerve fiber layer (RNFL) thickness of a patient to the built-in normative RNFL thickness, and the normative RNFL thickness usually has its peak RNFL thickness at the 11 and 7 o’clock position (on the right eye orientation). Considering that myopia has an association with glaucoma [10,11], diagnosing glaucoma in patients who have deviated RNFL thickness profiles is very important, even though these patients are a minority. In these cases, interocular comparison of the RNFL thickness can be an alternative diagnostic approach because the RNFL thickness profiles of healthy right and left eyes are generally mirror images of each other. We investigated the difference between the interocular RNFL thickness difference of normal eyes with deviated RNFL thickness profiles and normal eyes with nondeviated RNFL thickness profiles
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