Abstract
Purpose: :
To determine the ability of blue-on-yellow (BONY) multifocal VEPs (mfVEP) to identify functional loss in pre-perimetric glaucoma
Methods: :
24 patients with atleast one optic disc highly suspicious of glaucoma (as adjudged by 2 glaucoma specialists) AND bilaterally normal, reliable and repeatable achromatic Humphrey visual fields (HVF) were recruited. Abnormal discs were identified on one or more of the following criteria which suggest glaucoma: 1) definite focal rim notching (2) cup-disc asymmetry ≥ 0.2 with no disc size asymmetry, plus rim irregularity (3) markedly thinner inferior than superior rim of an eye with no abnormal disc configuration (eg tilting). Cataract or other ocular abnormality were exclusion criteria.BONY mfVEP testing was performed as described earlier.1 Amplitude and amplitude asymmetry at each segment were compared to a normal database. A defect was defined as (at minimum) a cluster of 3 abnormal points on the amplitude deviation plot with 2 segments P<2% and 1 segment P<1%, or a cluster of 3 abnormal segments on asymmetry deviation plot with P<1% or 2 zones with P<0.5%. Latency was analyzed based on sectors with similar waveforms (superior, superior horizontal, inferior and inferior horizontal)2.MfVEP was followed by optic disc stereo-photography. Abnormal rim regions were identified and the worst affected region in each patient was noted.
Results: :
Mean patient age was 64±8.2 yrs. 13 patients had unilateral and 11 had bilateral disc changes. Amplitude defects as defined were identified by mfVEP in atleast one eye of 13 (54.2%) patients.In 4 of 13 patients with unilateral disc changes,mfVEP identified a defect in the affected eye, topographically corresponding with the worse rim. None of them had bilateral mfVEP defects.Of 11 patients with bilateral disc changes, 5 had mfVEP defects in one eye, which topographically corresponded with the worst affected rim. Bilateral mfVEP defects were noted in 4 of these patients.Delayed latency in atleast one sector was seen in 17 patients (70.8%, 12 bilateral), including 11 (10 bilateral) of 13 patients with amplitude defects and 6 (2 bilateral) of 11 patients without defects. There was, however, no correlation between the eye/sector with disc changes and the eye/sector with delayed latency.
Conclusions: :
Amplitude of blue-on-yellow mfVEP appears to be a promising tool to topographically identify functional loss in pre-perimetric glaucoma. Latency delay may be an early general change with no lateralizing or localizing value.1Klistorner et al. Ophthalmology 2007; 114:1613-212Klistorner et al. Doc Ophthalmol 1999; 98:183-96
Keywords: electrophysiology: clinical