Rate of functional and structural change in glaucoma suspects.

Abstract

Abstract: : Purpose: To determine the rate of change in functional and structural measurements in a population of eyes at risk of developing glaucoma. Methods: Longitudinal Heidelberg Retinal Tomograph (HRT), Nerve Fibre Layer Analyzer (GDx) and Humphrey 24–2 full threshold field (HFA) data were obtained from 230 ‘high risk’ Caucasian eyes (ocular hypertensive or fellow eye with POAG). The majority of the eyes were on topical anti–glaucoma medication. The global and sectoral parameters of rim area and average retinal nerve fibre layer thickness were taken from the HRT and GDx, along with the corresponding mean pattern deviation values from the HFA. Linear regression was used to determine rates of change. Results: The mean age and length of follow–up were 60.36 ± 17.06 and 3.18 ± 0.95 years. The mean global rates of change within the population were –0.046 dB/yr (HFA pattern deviation), –0.61 µm/yr (GDx average nerve fibre layer thickness) and –0.0052 mm²/yr (HRT neural retinal rim area). Each measure showed rapid deterioration in only few cases. Using an outlier classification of exceeding the 75^th percentile by more than 3 times the difference between the 75^th and 25^th percentiles (0.60 dB/yr, 0.094mm²/yr, 5.08 µm/yr), to differentiate between those with and without rapid deterioration, 5 HFA, 4 HRT and 3GDx cases showed rapid deterioration (5% of cases). There was very little overlap between the cases classified as rapidly deteriorating by the 3 tests for the sectoral parameters and none for the global parameters. Conclusions: The rate of change in functional and structural measurements in an ‘at risk’ population is very low. In the few patients that demonstrated a rapid rate of deterioration, there was little agreement between functional and structural change and no evidence that patients developed structural change before functional loss.

Keywords: imaging/image analysis: clinical • visual fields • optic disc