Abstract
Purpose: :
To assess the correlation between the 5-year risk of developing POAG (as calculated by the OHTS-EGPS risk calculator) and the optic nerve head and RNFL morphometrical indices as evaluated by Stratus OCT, GDx ECC, HRT III in Ocular Hypertensive (OHT) patients.
Methods: :
Seventy two OHT patients with an untreated IOP between 22 and 32 mmHg in both eyes, an ophthalmoscopically normal optic disc with a c/d ratio asymmetry between the two eyes ≤ 0.2, and a visual field with GHT within normal limits, and normal PSD were enrolled. A comprehensive glaucoma work-up and examination by means of OCT, GDx ECC and HRT III were performed in all of the patients. Probability of developing POAG in 5 years was calculated by means of the OHTS-EGPS risk calculator (RC score), which has been developed by the OHTS-EGPS Collaborative Study Group by taking into account Age, and the mean values of CCT, IOP, PSD and C/D ratio collected in the two eyes. Correlations between the individual risk estimate and the OCT, GDx and HRT parameters were then assessed by regression analysis (exponential and linear), with a statistically significant level of p < 0.01.
Results: :
Mean age was 62.1 (sd 9.6), mean IOP was 23.4 (sd 2), mean CCT was 569.6 (sd 33.01), mean c/d ratio was 0.38 (sd 0.17), and mean PSD was 1.79 (sd 0.44). The individual risk of the 72 patients ranged between 1.5 and 28.6%, with a mean of 10.2% (sd 6.4). Only OCT RNFL-related parameters showed a statistically significant correlation with the RC score. Average RNFL Thickness had an exponential regression r2 of 0.21 (p<0.0001) and a linear regression r2 of 0.14 (p=0.0012); Superior Average RNFL Thickness had an exponential regression r2 of 0.26 (p<0.0001) and a linear regression r2 of 0.23 (p<0.0001); Nasal Average RNFL Thickness only had an exponential regression r2 of 0.12 (p=0.0031). Neither GDx RNFL-related parameters, nor HRT disc-related parameters showed statistically significant correlations with RC score.
Conclusions: :
This explorative study showed that the individual risk to develop POAG within 5 years in OHT individuals is statistically significantly correlated with OCT RNFL parameters, but not with GDx RNFL parameters or HRT disc parameters. OCT parameters could explain about 20-25% of the variability in individual RC score. The RC score seems to take into account sub-clinical RNFL thinning shown by the OCT.
Keywords: clinical (human) or epidemiologic studies: risk factor assessment • imaging/image analysis: clinical • nerve fiber layer