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A. Jindal, B. E. Leiby, D. Fleischman, J. S. Myers, G. L. Spaeth, L. J. Katz; Effect of Acutely Lowering Intraocular Pressure on Multifocal Visual Evoked Potential Testing. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2238.
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There have been many reports in the literature on the apparent reversal of optic nerve damage in glaucoma patients after lowering of intraocular pressure clinically, on visual field testing (Katz et al, Tsai et al), and using nerve fiber layer thickness on OCT (Aydin et al). There are no studies to date that have looked at improvement of multifocal visually evoked potentials (mfVEP), after lowering intraocular pressure.
Prospective study of 20 consecutive patients seen in the glaucoma department at Wills Eye Institute with elevated IOP. Exclusion criteria included: intraocular surgery within 6 weeks, visual acuity less than 20/40, pathology unrelated to glaucoma (retinal disease, stroke, etc) with visual field defect, and prior corneal diseases with resultant edema, scarring, or transplant. The patients were administered mfVEP(Accumap V2.0), 24-2 Humphrey visual field, and HRT at baseline and 2-3 hours post-IOP reduction. Target IOP reduction was 30%.
Of the 20 patients enrolled, 3 patients failed to complete all studies and were excluded. Data from the remaining 17 patients were analyzed and Spearman rank correlation coefficients were calculated between change scores for IOP reduction and: Accumap Severity Index(ASI; pre-IOP reduction range 4-254, post-IOP reduction ), Accumap average superior hemifield (pre-reduction 57-161nV, post-reduction 53-242 nV) and inferior hemifield values(pre-reduction 66-270 nV, post-reduction 6-297 nV), Humphrey mean deviation(MD; pre-reduction -29.37- -1.10DB, post-reduction -29.37- -0.08 DB); HRT rim (pre-reduction 0.54-2.5mm2, post -reduction 0.58-2.5 mm2) and cup area (pre-reduction 0.001-1.7 mm2, post-reduction 0.003-1.7 mm2) . The initial IOP treated ranged from 23-50 mmHg with a reduction between 19-80%. The Spearman rank correlations were: for change in ASI 0.37(p =0.14), Accumap superior hemifield 0.049(p=0.85), Accumap inferior hemifield 0.030(p=0.91), MD was 0.081(p=0.76), HRT rim area was 0.17(p=0.51), and HRT cup area was -0.006(p=0.98).Weak positive but insignificant correlations were seen for all parameters, except cup area, with the strongest correlation seen between decrease in IOP and improvement in ASI.
This pilot study did not show statistically significant correlations between IOP reduction and Accumap, HVF, and HRT measures, however positive correlations were seen for some measures. Further studies with a larger sample size are needed.
Clinical Trial: :
www.clinicaltrials.gov NCT00799994 Wills Eye Institue
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