POINTWISE TOPOGRAPHICAL AND LONGITUDINAL MODELING OF THE VISUAL-FIELDIN GLAUCOMA

Purpose. To develop a suitable mathematical model for the description of the pointwise distribution of sensitivity across the visual field i n glaucoma. Methods. The pointwise distribution of sensitivity at any given stimulus location for any given examination was described by a j oint topographical and longitudinal model. The topographical element m odeled the pointwise distribution of sensitivity using a second-order polynomial function in terms of the respective stimulus coordinates wh ereas the longitudinal element modeled the pointwise distribution of s ensitivity using multiple linear regression in terms of the sensitivit y at the given location determined at one or more previous examination s. The sample comprised Humphrey Field Analyser (Humphrey Instruments, San Leandro, CA) Program 30-2 and 24-2 fields from 49 patients attend ing a glaucoma clinic for an average of 3 years. Results. The constant term of the polynomial correlated highly with the mean deviation and moderately with the pattern standard deviation. The goodness-of-fit be tween the modeled and the measured field increased as an exponential f unction of the number of previous examinations. The median R2 was 19.6 % for the first examination and 83.6% for the sixth examination. The g roup median optimum percentage of error between the measured and model ed sensitivity at each test location was below 10% (i.e., less than 3 dB), increased with increase in eccentricity, was greater at the extre mities of the superior field and varied as a function of the severity of the field loss. Conclusion. The model seems to be a promising way t o evaluate visual field progression.