Evaluation of heidelberg retinal tomography and optic coherence tomography findings in cases with primary open angle glaucoma, pre-perimetric glaucoma and ocular hypertension

This study was carried out to compare the Heidelberg retina tomography (HRT) and optic coherens tomography (OCT) findings in patients with primary open angle glaucoma (POAG), preperimetric glaucoma (PPG) and ocular hypertension (OHT), and to evaluate the compatibility of these findings with visual field test indices. Fifty nine POAG patients, 19 PPG patients, 20 OHT patients and 16 healthy people were included to the study. Patients with POAG were divided into 3 groups according to the degree of visual field defects using Hodapp-Parrish-Anderson criteria. All patients underwent detailed ophthalmologic examination, Swedish interactive testing algorithm (SITA) standard programme (Humphrey Field Analyzer III, Model 750 I), optic nerve head and retina nerve fiber layer imaging with the aid of OCT (Cirrus HD-OCT, Carl Zeiss Meditec Inc, Dublin, CA) and HRT (Heidelberg Engineering GmbH 2001, Germany). In all groups, disc area (DA), rim area (RA) measured with HRT and cup area (CA), cup volume (CV) and vertical cup/disc ratio (C/D) measured with OCT were significantly larger (p<0.05). The difference between the C/D value obtained by OCT and HRT was decreased when the C/D increased. Cup/ disc ratio measured by HRT was significantly correlated with C/D measured by OCT in only moderate and severe POAG groups (p>0.05). The best valuable RNFL parameter was mean RNFL thickness in the differentiation of glaucomatous patients from non-glaucomatous eyes. Mean RNFL thickness measured by HRT and OCT were significantly correlated, although the numeric values were highly different. There was significant correlation between mean RNFL thickness measured by HRT and inferior RNFL quadrant thickness measured by OCT in early and moderate POAG groups, while these parameters were not correlated in OHT and advanced POAG groups. Mean deviation (MD) measured by automated perimetry was correlated with superior quadrant RNFL thickness; pattern standard deviation (PSD) was correlated with CA, CV, C/D measured by OCT in moderate POAG group, while MD was correlated with superior, inferior and temporal quadrant rim thickness measured by HRT in severe POAG group. Superior, inferior quadrant RNFL thickness measured by OCT and RA, mean RNFL thickness measured by HRT; C/D and mean, inferior, superior quadrant RNFL thickness measured by OCT and all OCT-HRT parameters except temporal quadrant RNFL thickness were significantly valuable in the differentitation of PPG from early POAG, OHT groups and healthy eyes, respectively. Visual field defect was detected when the 25% of total RNLF thickness was damaged. In conclusion, OCT and HRT analyse optic nerve head and RNFL parameters using different principles, and shows good correlations to each other in patients with moderate or advanced glaucoma. OCT RNFL parameters are significant in eyes with no visual field damage.