Abstract
Purpose: :
To determine whether the multifocal visual evoked potential (mfVEP) can detect visual field defects and progression in glaucoma suspect (GLS) eyes with normal achromatic perimetry results.
Methods: :
69 GLS eyes of 39 patients were followed for 1–3 yrs. The criteria for GLS included vertical cup–disc ratio>=0.6, and/or disc asymmetry>=0.2, and/or a parapapillary nerve fiber layer defect, and/or focal disc notching, and/or disc hemorrhage. All eyes had normal achromatic perimetry, as defined by a PSD within 95% and a glaucoma hemifield test within normal limits on the Humphrey visual field 24–2 program. Monocular mfVEPs were obtained from each eye using a pattern–reversal dartboard array, 44.5 deg in diameter, and containing 60 sectors. Recording electrodes were placed at the inion (I) and I+4 cm, and also at two lateral locations up 1 cm and over 4 cm from I. Monocular and interocular analyses were performed [1,2]. For the mfVEP, a hemifield was defined as abnormal based on the following cluster test [3,4]: if 2 or more contiguous points had p<0.01, or 3 or more contiguous points had p<0.05 with at least one of these points with p<0.01. An eye was defined as abnormal if either one or both hemifields had a cluster of abnormal points. Progression was defined as an addition of a new cluster and/or expansion (more abnormal points) of an existing cluster.
Results: :
Of the 69 GLS eyes, 14 eyes (20%) had abnormal mfVEPs on the first visit. On follow–up, 10 of these eyes retained their abnormal mfVEP hemifields with 4 showing progression, all had normal achromatic perimetry. Of the 55 eyes (80%) without a deficit, 49 (71%) remained stable and 6 (8%) developed clusters of abnormal points at follow–up.
Conclusions: :
The mfVEP can detect field defects in GLS eyes that are not detected by achromatic automated perimetry. The mfVEP also detects progression of the deficits. Ref: 1.Hood et al (2002) Arch Ophthalmol. 2.Hood and Greenstein (2003) Prog Ret Eye Res. 3.Chauhan et al (1998) Doc Ophth 4. Goldberg et al (2002) Am J Opthalmol.
Keywords: electrophysiology: clinical • visual fields • perimetry