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Abstract #22986 Published in IGR 11-1
Ganglion cell loss and dysfunction: relationship to perimetric sensitivity
Drasdo N; Mortlock KE; North RVOptometry and Vision Science 2008; 85: 1036-1042
PURPOSE: 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.
Dr. N. Drasdo, School of Optometry and Vision Sciences, Cardiff University, Cardiff, Wales, UK
Classification:
6.6.2 Automated (Part of: 6 Clinical examination methods > 6.6 Visual field examination and other visual function tests)
11.8 Neuroprotection (Part of: 11 Medical treatment)
