Abstract
Purpose: :
To date there is no knowledge about the impact of optic disc size on the RNFL as measured with GDx-VCC or GDx-ECC. Since the size of the optic disc is not taken into account for the analyses carried out by the GDx it might affect sensitivity in large optic discs and specificity in small ones. It was the aim of the present study to quantify the influence of optic disc size on the peripapillary RNFL thickness as measured with the current and upcoming SLP technologies in healthy subjects.
Methods: :
Topographic optic disc measurements and RNFL thickness values of 80 subjects of both sexes aged between18 and 69 years were measured using HRTIII and Gdx -VCC and -ECC. Subjects were divided into 3 equally large groups depending on the optic disc area (group 1: <1.84 mm2; group 2: 1.85 mm2 to 2.23 mm2; and group 3: >2.23 mm2). We compared parameters of HRT III (optic disc morphology: rim area, rim volume, c/d area ratio, linear c/d ratio; measures of RNFL: mean RNFL thickness, RNFL crosssectional area), as well as parameters of Gdx VCC and ECC (NFI, TSNIT average, superior average, inferior average, TSNIT Sdev., TSS) between the 3 groups using ANOVA.
Results: :
For all parameters of optic disc morphology as measured with HRTIII, ANOVA showed statistical significance between the three groups of different optic disc areas (p<0.001 to p=0.019). In contrast the HRT measures of RNFL did not reach the level of significance. None of the tested parameters of GDx VCC and ECC demonstrated a significant effect of the optic disc area in ANOVA.
Conclusions: :
We could not find an impact of optic disc size on any retinal nerve fibre parameter measured with GDx VCC or ECC and with HRT III. In contrast parameters of optic disc morphology as measured with HRT III were significantly influenced by the size of the optic disc.
Keywords: imaging/image analysis: non-clinical • retina • optic disc