Abstract
Purpose: :
This pilot study compares the preliminary clinical data obtained from a Heidelberg Edge Perimeter with Standard Achromatic Perimetry (SAP) and Heidelberg Retinal Tomography (HRT).Since both HEP and SAP report values in the same manner, it is essential to understand any differences between the actual values measured. HEP uses Flicker defined form (FDF) to generate the stimuli used for early detection of glaucoma.
Methods: :
Preliminary data of this prospective cross sectional observational investigation had glaucoma patients with varying severity graded on basis of Hodapp-Anderson-Parrish Criterion and controls. All subjects underwent SAP on the Humphrey’s Field Analyzer HFA 750 II, using the 24-2 testing protocol by SITA-Standard strategy and HEP using the 24-2 testing protocol by ASTA Standard strategy. Standard clinical data, including visual acuity, intraocular pressure and HRT (for structure -function correlation) was obtained for each patient. Patients with an abnormal appearing disc such as tilted disc or congenital disc anomalies were excluded from the study. Mean deviation and Pattern deviation measurements by both machines were correlated using Spearmen’s correlation coefficient.
Results: :
Data obtained from 11, 2 and 9 patients with mild, moderate and severe glaucoma respectively and 12 controls were analysed. HEP mean deviation parameters were highly correlated to those of SAP(r=0.72; p<0.0001) while the HEP and SAP pattern deviation were not significantly correlated (r=-0.11;p=0.52).Visual field indices showed statistically significant correlation with HRT 3 cup disc ratio(HVF MD p=0.03;HEP MD p=0.005),disc area(HVF MD p=0.20;HEP MD p=0.04), rim volume(HVF MD p=0.003;HEP MD p=0.001) and RNFL parameters(HVF MD p=0.0001;HEP MD p<0.0001).Five controls had MD>2dB (False positives),while 1 glaucoma patient had MD <2dB (False negative )on HEP.
Conclusions: :
This pilot study shows that HEP results have similarities to SAP results. HEP and HVF have significant correlations to each other and HRT parameters in glaucoma and controls. The potential utility of HEP in the clinical management of glaucoma deserves further investigation.
Keywords: imaging/image analysis: clinical • perimetry • visual fields