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Naheed W Khan, Kari E Branham, Sarwar Zahid, Ashley Thompson, Jillian Huang, Thiran Jayasundera, John R Heckenlively; Relationship between Visual Fields and the Electroretinogram in RPGR-X-linked Retinitis Pigmentosa. Invest. Ophthalmol. Vis. Sci. 2014;55(13):1397.
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© ARVO (1962-2015); The Authors (2016-present)
To quantify disease severity by investigating the relationship between Goldmann visual field (GVF) area and the full-field electroretinogram (ERG) parameters in patients with RPGRORF15 and RPGR1-19 mutations.
A retrospective chart review of both eyes of 20 RPGRORF15 patients, ages 6 -42 yrs., and 12 RPGR1-19 patients, ages 6 - 56 yrs. The horizontal diameter (HD) and GVF planimetric areas were measured for isopters IV4e and I4e. Normal range from 8 normally sighted observers ages 23 to 50 yrs. was IV4e: 4.2±0.04 SD log deg2 for area and 149.7±6.73° SD for HD and I4e: 4.09±0.026 SD log deg2 for area, and 131.32±5.86° SD for HD. ERG parameters included amplitude and implicit time for the ISCEV standard.
In all subjects visual acuity ranged from 20/20 to 20/200. Square root of GVF area was statistically significantly related linearly to HD for both isopters and for each genotype. RPGRORF15: 16 of 20 (80%) patients had < 30% normal photopic flash and flicker amplitude including 3 with non-detectable (ND) ERG. These subjects had retained 23% to 80% of normal IV4e area and about 1% to 53% of I4e area. Their IV4e HD was in the range 23.9° to 139° and I4e HD from 5.7 to 53°. There was a significant linear correlation between scotopic rod-cone b-wave (Bmax) for I4e (R=0.8, p<0.0001) and for IV4e (R=0.6, p<0.0086). The relationship was poor between photopic amplitude and GVF area. However, both flicker and flash ERG implicit time had a statistically significant linear relationship with I4e (R=-0.89, p<0.0001) and with IV4e (R=-0.66, p<0.0015). RPGR1-19 patients had more severely affected ERG and GVF. Ten of 12 patients had ND scotopic ERG; of these, 6 had ND photopic ERG. Photopic implicit times fell in one of two clusters, ND or delayed (>35 ms). There were no significant correlations for any of the ERG parameters with GVF area. Patients in these categories had 2.4% - 44% normal area or 21.5° - 55° HD with IV4e and 0.18% - 2.2% normal area or 5.8° - 14.5° HD with I4e.
The strongest relationship was for decreasing GVF area with increasing photopic ERG implicit time and for decreasing scotopic Bmax amplitude in RPGRORF15. Central GVF areas were retained despite reduced ERGs in both groups, but were variable when the photopic and/or scotopic ERG was non-detectable.
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