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M. G. Uva, M. Di Pietro, A. Longo, K. Lauretta, M. Reibaldi, A. Reibaldi; Pattern ERG and RNFL Thickness in Hypertensive Eyes With Normal Blue-yellow Visual Field. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4412.
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To evaluate the transient pattern-electroretinogram (t-PERG) and the retinal nerve fiber layer (RNFL) thickness in eyes with ocular hypertension (OH) with normal short-wavelength automated perimetry (SWAP).
In 29 patients (age 25-65 yrs, mean 46±3) with bilateral OH with normal SWAP and in 29 healthy controls (age 23-61 yrs, mean 43±3) t-PERG recording and RNFL thickness measurement were performed.All subjects had best-corrected visual acuity (BCVA) of 20/20 (refraction range: -6D - +3D, with astigmatism lower than 1D), central corneal thickness (CCT) between 530 and 570 microns, and no ocular, metabolic, or neurological diseases.IOP (mean of 4 daytime readings) was >22mmHg in OH eyes (without any treatment) and <18 mmHg in controls. All had C/D ratio lower than 0,5. One eye for each subject was considered. All subjects were well trained in performing SWAP (at least 3 previous reliable SWAP, full threshold 24-2, performed by 745i HFAII); normal SWAP had MD and PSD within 95% confidence limits and glaucoma hemifield test within normal limits. Mean deviation (MD) and pattern standard deviation (PSD) were considered. Monocular PERG were recorded by using a black and white checkerboard pattern (check size 0.9°, contrast 80%, mean luminance 80 cd/m2) generated on a monitor and reversed in contrast (4 reversals per second) at a distance of 70 cm (field 22°x16°). The signal was amplified, filtered and averaged with automatic rejection of artifacts (BM 6000, Biomedica Mangoni, Pisa, Italy). Peak-to peak amplitude of P50 and N95 waves, and implicit time of P50, were considered. RNFL thickness was determined by OCT3 (Fast RNFL thickness program).
Between the two groups, no difference was seen in mean values of age, BCVA, refraction, CCT, MD, PSD, N95 amplitude and P50 implicit time. Compared to controls, in OH eyes were found a reduction of P50 amplitude (2,49±1,05 vs 1,88±0,91 micronvolts, p=0.023)(with a correlation between P50 amplitude and IOP), and a reduction in average RNFL thickness (84±14 vs 96±11 microns, p=0.001) and in RNFL thickness in superior (p=0.003) and inferior (p=0.000) 90° quadrants.
In OH eyes, Pattern ERG and RNFL thickness changes occur also in presence of an undamaged SWAP; PERG amplitude is correlated to the IOP and not to the RNFL thickness.
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