April 2010
Volume 51, Issue 13
ARVO Annual Meeting Abstract  |   April 2010
Restricted Field ERG Measurement of Central Retinal Dark Adaptation in Monkeys With Macular Drusen
Author Affiliations & Notes
  • B. G. Jeffrey
    Neuroscience, Oregon National Primate Research Center, Beaverton, Oregon
  • L. M. Renner
    Neuroscience, Oregon National Primate Research Center, Beaverton, Oregon
  • M. Neuringer
    Neuroscience & Ophthalmology, ONPRC,Oregon Health & Science University, Beaverton, Oregon
Investigative Ophthalmology & Visual Science April 2010, Vol.51, 5567. doi:
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      B. G. Jeffrey, L. M. Renner, M. Neuringer; Restricted Field ERG Measurement of Central Retinal Dark Adaptation in Monkeys With Macular Drusen. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5567.

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      © ARVO (1962-2015); The Authors (2016-present)

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Purpose: : In humans, slowed dark adaptation (DA), measured psychophysically, is correlated with age and early AMD. The restricted field ERG (rfERG) isolates the rod photoreceptor response from a 40o field of the central retina1. Here we developed a rfERG method for measuring DA and examined central DA in aged monkeys with macular drusen.

Methods: : Full field ERG (ffERG) and rfERG measures of rod phototransduction and DA were made in 14 rhesus monkeys aged 22-30 yrs (ca. 66-90 human yrs). Retinal color photographs were graded for drusen as either none/mild (N=6) or moderate/severe (N=8). For rfERGs, a reversible ophthalmoscope was used to align the macula with the Ganzfeld opening; the flash subtended 40o on the retina at the 30 cm recording distance. For DA, ERGs were recorded to paired flashes (4.4 log sc td-s with 1.2 - 2 sec separation) every 2 mins after a 100% bleach. Rod isolated ERGs were obtained by subtracting the second flash response, generated by the cones (ffERG) or cones+scatter (rfERG) from the first flash. Derived parameters were the time constant of DA recovery (τDA) and the time to 50% full recovery (T50). Rod phototransduction was assessed from a P3 model fit to ERG a-waves recorded to bright flashes (2.1 to 4.8 log sc td-s) presented alone or 2 sec after a conditioning flash. Rod-isolated ERGs were obtained as for DA.

Results: : Central τDA was significantly correlated with age (p<0.01). For all monkeys combined, central τDA and T50 (mean±SE; 3.8 ± 0.2 min; 18.9 ± 0.6 min) were significantly longer (p<0.03) than full field values (τDA = 3.3 ± 0.2 min; T50 = 16.7 ± 0.8 min). In monkeys with moderate/severe drusen the delay in central field T50 relative to full-field T50 was greater than in monkeys with no/mild drusen (22% vs. 7%, p<0.07). Maximal rod response (RmaxP3) and rod sensitivity (S) were reduced by 70% in the central field but did not differ between drusen groups.

Conclusions: : These results suggest that central field DA measured with the rfERG can provide a specific and sensitive measure of early changes in central retinal function associated with aging and drusen in the monkey.1Nusinowitz et al (1995) J Opt Soc Am A 12:2259-66

Keywords: electroretinography: non-clinical • electroretinography: clinical • age-related macular degeneration 

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