Correlations of the Neuroretinal Rim Area with Ocular and General Parameters in Normal Eyes

Abstract

The neuroretinal rim as equivalent of the retinal nerve fibers is the target in the evaluation of glaucomatous optic nerve heads. Its area was measured in absolute size units using photographs of 234 normal optic disks and correcting the photographic magnification according to Littmann’s method. High myopic eyes ( < -8.00 dptr) were excluded. The mean rim area was 2.09 ± 0.60 (0.80–3.80 mm²). It was significantly correlated (p < 0.00001) to the optic disk area. In optic disks without cupping, the neuroretinal rim area was identical with the disk area (r = 1.0, slope of the regression line = 1.0). In disks having cups with temporal flat slopes, the rim area increased by a factor of 0.71 with the disk size, in disks with circular steep cups, by a factor of 0.26. This interindividual variability and the correlations between rim and disk area might be clinically important for morphometry of glaucomatous optic nerve heads. There were no significant correlations between rim area and age, sex, refraction or axial length.

The definition and classification of glaucoma in prevalence surveys

“…Potential weaknesses in the use of VCDR as a defining feature for glaucoma include variation in the size of the optic disc between individuals, 11 12 variation in the number of axons in the optic nerve, from a minimum of 816 000 to a maximum of 1 502 000 (mean 1 159 000 plus or minus 196 000) in Europeans 13 and the observation that larger optic nerves have a larger neuroretinal rim area 14 and contain more axons. 15 Correction for variation in disc size when assessing the CDR has been suggested.…”

Cilioretinal Arteries in Large Optic Disks

“…The optic disk and cup size are correlated with each other [25,26]. The correlation between the num ber of cilioretinal arteries and the glaucoma tous visual field loss, however, cannot be explained on the basis of a different optic disk size: there is no significant difference in optic disk size between normal and glauco matous optic nerve heads [27], and glauco matous neuroretinal rim loss is not more marked in larger or smaller optic nerve heads [28].…”

Optic Disk Size and Glaucoma

“…There is consistent evidence, regardless of the measurement technique that rim area increases with increasing disk size. 21,22,24,31,48,49,79,86,110 This raises the question, as to whether large disks have more optic nerve fibers than small disks. A larger number of nerve fibers may represent a larger anatomical reserve in various optic neuropathies including glaucoma.…”