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T. M. Grippo, D. C. Hood, F. N. Kanadani, I. Ezon, B. Wangsupadilok, C. Tello, J. M. Liebmann, R. Ritch; The Effects of Optic Nerve Head Drusen on the Latency of the Multifocal Visual Evoked Potential. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3174.
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© ARVO (1962-2015); The Authors (2016-present)
To determine the effect of optic nerve head drusen (ONHD) on the latency of the multifocal visual evoked potential (mfVEP) and to better understand the pathophysiology of this condition.
Monocular mfVEPs were recorded from a group of 10 patients (18 eyes) with ONHD, 18 patients (26 eyes) with high tension glaucoma (HTG), 19 patients (31 eyes) with low tension glaucoma (LTG) and a control group of 19 subjects (38 eyes). Mean age was 62.0 ± 11 (LTG); 62.0 ± 10.8 (HTG); 59.7 ± 9.3 (ONHD) and 53.0 ± 9.5 (controls) years. Average mean deviation (MD) was - 6.4 ± 5 (LTG); - 6.2 ± 4.3 (HTG) - 5.2 ± 7.0 (ONHD) and - 0.5 ± 0.9 (controls) dB. Mean recorded maximum intraocular pressure (IOP) was 17.2 ± 4.9 (LTG); 26.3 ± 5.5 (HTG); 15 ± 3.7 (ONHD) and 14 ± 3.5 (controls) mmHg. Glaucoma eyes were defined by the presence of a glaucomatous disc and an abnormal 24-2 visual field as described previously  and were characterized as LTG or HTG based on IOP. The mfVEPs were elicited by a 60-sector dartboard display. The mfVEPs monocular latencies were measured using custom software  and analyzed in two ways: 1) average relative latency (i.e. the latency relative to a normative group ) of all individual mfVEPs for an eye, and 2) percent of the 60-sectors with significantly delayed latencies.
For 50% (9/18) of the ONHD eyes, mfVEP latency values fell above the 95% limits for the controls, while for 39% (7/18) of the ONHD eyes, the percent of delayed sectors fell above the 95% limit. All patient groups showed an increase in mfVEP latency with average relative latencies, and percent of sectors delayed, of 4.5 ms & 15% (ONHD), 2.8 ms & 9.3% (LTG) and 5.5 ms & 20.9% (HTG) compared to 1 ms and 4.9% (controls). When one eye (the eye with the worse MD on perimetry) of each subject was analyzed, the difference between ONHD (4.5 ms; 15.6%), HTG (5 ms; 20.5%) and controls (1 ms; 4.5%) was significant (Wilcoxon test; p < 0.05).
ONHD causes an optic neuropathy that produces significant latency delays on the mfVEP. These delays are greater than those seen in LTG and ischemic optic neuropathy , similar to those for HTG, where mechanical compression may play an important role, and below those seen in compressive optic neuropathy  were mechanical compression is involved. Mechanical compression may contribute to visual field loss in patients with ONHD. 1. Grippo et al IOVS (2006); 2. Hood et al Doc. Ophthal. (2004); 3. Fortune et al Doc. Ophthal. (2004); 4. Odel et al ARVO 2005; 5. Semela et al BJO (2006).
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