Humphrey matrix frequency doubling technology perimetry and optical coherence tomography measurement of the retinal nerve fiber layer thickness in both normal and ocular hypertensive subjects

Abstract

Purpose: The purpose of this study was to determine by means of the Humphrey Matrix frequency doubling technology (FDT) perimetry and the optical coherence tomography (OCT) retinal nerve fiber layer (RNFL) thickness measurement whether functional and/or structural differences exist between normal and ocular hypertensive (OHT) subjects.

Patients and methods: One eye of 60 consecutive normal individuals and 60 OHT subjects was enrolled in this prospective observational comparative case series study. All subjects were examined at either the Ophthalmology Clinic, University of Chieti-Pescara, Chieti, Italy or the Department of Ophthalmology, S. Maria della Misericordia Hospital, Udine, Italy. All subjects underwent a full ophthalmic examination, including visual acuity, slit-lamp biomicroscopy, central corneal thickness ultrasound pachymetry measurement, achromatic automated perimetry, Matrix FDT perimetry, stereoscopic optic nerve head photography, and OCT. Matrix FDT perimetry mean deviation (MD), pattern standard deviation, glaucoma hemifield test, and 12 OCT RNFL thickness parameters were examined. Student t test, Bonferroni correction for multiple comparisons and receiver operator characteristics curve areas (AUROCs) were used to find any discrimination function between healthy and OHT eyes. Sensitivities at 83% and 92% specificities were reported.

Results: The FDT MD scores ranged from -1.10 to +3.80 decibels (db) in normal individuals and from -4.75 to +3.20 db in OHT subjects. The comparison between the average MD in the 2 groups showed a statistically significant difference (P=0.024). OCT showed a statistically significant difference between the 2 groups when examining the ratio between the inferior and the superior mean RNFL thickness (P=0.004). For OCT, the parameter with the largest AUROC for discriminating between healthy and hypertensive eyes was the ratio between the mean inferior and superior RNFL thickness (AUROC=0.85, sensitivity=75% at specificity=83%, sensitivity=67% at specificity=92%). For Matrix FDT perimetry, the parameter with the largest AUROC was MD (AUROC=0.78, sensitivity=67% at specificity=83%, sensitivity=58% at specificity=92%).

Conclusions: Our results suggest that OHT eyes having a normal achromatic automated perimetry and a normal clinical disc appearance cannot be differentiated from normal eyes using conventional OCT parameters. When analyzing the ratio between inferior and superior average RNFL thickness, however, a significant difference is evident between healthy and hypertensive eyes. Using Matrix FDT perimetry, a significant difference in MD seems to exist between these 2 groups of eyes. The AUROCs confirm that OCT Iavg/Savg and Matrix FDT MD show the greatest sensitivity and specificity among the examined OCT and Matrix FDT parameters.