Activation phase of cone phototransduction and the flicker electroretinogram in retinitis pigmentosa

This study examined the relationship between the activation phase of cone phototransduction and the flicker electroretinogram (ERG) in 15 patients with retinitis pigmentosa (RP) and 12 age-equivalent, visually normal control subjects. Values of R mp3 (maximum amplitude of P3, the massed cone photore...

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Bibliographic Details
Published in:Vision research (Oxford) 2006-09, Vol.46 (17), p.2773-2785
Main Authors: Alexander, Kenneth R., Rajagopalan, Aruna S., Raghuram, Aparna, Fishman, Gerald A.
Format: Article
Language:English
Subjects:
Adult
Aged
Biological and medical sciences
Cone
Electroretinogram
Electroretinography
Female
Flicker
Humans
Lighting
Male
Medical sciences
Middle Aged
Ophthalmology
Photic Stimulation - methods
Retinal Cone Photoreceptor Cells - physiology
Retinitis pigmentosa
Retinitis Pigmentosa - physiopathology
Retinopathies
Vision, Ocular
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Summary:This study examined the relationship between the activation phase of cone phototransduction and the flicker electroretinogram (ERG) in 15 patients with retinitis pigmentosa (RP) and 12 age-equivalent, visually normal control subjects. Values of R mp3 (maximum amplitude of P3, the massed cone photoreceptor response) and S (sensitivity of cone phototransduction) were derived from a delayed Gaussian model applied to the leading edge of the ERG a-wave. Fundamental amplitude and phase of the flicker ERG were derived from responses to sinusoidal flicker presented at temporal frequencies ranging from 7.8 to 100 Hz. Patients with RP who had a reduced value of R mp3 alone had an overall reduction in flicker ERG amplitude with a normal response phase across temporal frequency. Patients with RP who had a reduced value of S, whether or not R mp3 was reduced, had the greatest amplitude reduction at temporal frequencies above 40 Hz and phase lags across a range of temporal frequencies. At high temporal frequencies, the amplitude reduction of the flicker ERG was predicted by the product of R mp3 and S for all of the subjects except the three patients with RP who had the lowest fundamental amplitudes. The results indicate that there is a systematic relationship between the derived parameters of the activation phase of cone phototransduction and the characteristics of the flicker ERG in patients with RP, although the phase changes in the flicker ERG were generally greater than predicted by the derived parameters alone.
ISSN:0042-6989
1878-5646
DOI:10.1016/j.visres.2006.01.007