Factors predicting the rate of functional progression in early and suspected glaucoma.

PURPOSE: Clinical trials in glaucoma have often sought to predict whether a patient will progress or remain stable. This study proposes to combine and support results from earlier studies, forming a model to predict the actual rate of functional change in glaucoma.
METHODS: Data were taken from 259 eyes of 150 participants with early or suspected glaucoma in the ongoing Portland Progression Project. A total of 3854 study visits were available, each consisting of visual acuity, confocal scanning laser ophthalmoscopy (CSLO), and perimetry. The rate of functional change was calculated over each of 1541 series of six consecutive visits. Mixed effects models were formed to predict these rates using baseline perimetric measurements and CSLO parameters, together with IOP, age, and change in visual acuity through the series (to remove any confound from media changes).
RESULTS: Cup volume from CSLO was predictive of subsequent rate of functional change (P = 0.036), together with baseline mean deviation (P < 0.001) and pattern standard deviation (P = 0.097), age (P = 0.013), maximum IOP during the sequence (P = 0.004), and change in acuity during the sequence (P = 0.022). In a similar model, rim area was less predictive of functional change (P = 0.066).
CONCLUSIONS: A larger optic cup and/or a more damaged visual field are predictive of more rapid perimetric sensitivity loss. The structural parameters most closely correlated with current functional status may not be the parameters that are most useful for predicting the future course of a patient's disease. Maximum IOP may be a more important risk factor than mean IOP over the same time period.