Ganglion cell loss and dysfunction: relationship to perimetric sensitivity.
OBJECTIVE
To describe two methods of neural damage quantification from perimetric data, and to discuss their theoretical implications.


METHODS
A recently published model of retinal ganglion cell (GC) receptive field density is used to obtain best estimates of the receptive fields per solid degree at each stimulus point in the 24-2 test pattern array. A method of age related change compensation is proposed and a functional relationship between perimetric sensitivity and GC survival is used for loss quantification.


RESULTS
Data for the 24-2 test pattern array for the right eye are presented. These can be adjusted for age related loss, but are also expressed as percentages which are considered to be age invariant. Simple models relating receptive field density to sensitivity are proposed for quantification.


CONCLUSIONS
Equations relating GC receptive field densities at points in the visual field to normative data on sensitivity are proposed to estimate GC loss in glaucoma. If 1/Lambert sensitivity is <800, (29 dB), a linear relationship applies and a loss factor of 1-10, where TD is the signed total deviation in decibels, may be applied to values in a percentage chart which are provided to give the percentage loss for each stimulus. Higher sensitivities are non-linearly related. Two equations are proposed to cover the range corresponding to thresholds from 0 dB to 33 dB. Hypothetical examples are given and the relationship between visual field defects and pattern electroretinograms is discussed in quantitative terms.
Drasdo
Neville
N
School of Optometry and Vision Sciences, Cardiff University, Cardiff, Wales, United Kingdom.
Mortlock
Katharine E
KE
North
Rachel V
RV
D000328:Adult; D000375:Aging; D016923:Cell Death; D002470:Cell Survival; D005901:Glaucoma / Q000503:physiopathology*; D006801:Humans; D016014:Linear Models; D008954:Models, Biological; D017711:Nonlinear Dynamics; D012165:Retinal Ganglion Cells; D012680:Sensitivity and Specificity; D058609:Visual Field Tests; D014794:Visual Fields