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Eccentricity-dependent changes in local onset and offset responses in patients with progressive cone dystrophy
K Holopigian1, P Wynn, W Seiple
1Department of Ophthalmology, New York University School of Medicine, BEL 5N15, 462 First Avenue, New York, NY 10016, USA. kh19@nyu.edu
Vision Research
|July 7, 2007
Summary
Patients with cone dystrophy (CD) show a selective deficit in visual system ON-pathway responses. This study found reduced onset responses compared to offset responses, particularly in central vision, supporting the ON-system deficit hypothesis.
Area of Science:
- Ophthalmology
- Neuroscience
- Visual electrophysiology
Background:
- Cone dystrophy (CD) is a retinal disease affecting photoreceptor cells.
- Previous research suggested a potential selective ON-system deficit in CD patients.
- Understanding the specific visual pathway involvement is crucial for diagnosis and treatment.
Purpose of the Study:
- To investigate the hypothesis of a selective ON-system deficit in cone dystrophy patients.
- To analyze visual responses (onset and offset) as a function of eccentricity.
- To utilize long-duration stimuli to differentiate ON and OFF pathway function in CD.
Main Methods:
- Recruited nine cone dystrophy patients (mean age 36.1, visual acuity 20/200).
- Performed Humphrey visual fields, standard mfERGs, and mfERGs with long-duration (100ms on/off) LED stimuli using Retiscan.
- Obtained full-field photopic and flicker ERGs for comparison.
Main Results:
- Control subjects showed larger onset than offset responses across all eccentricities.
- Cone dystrophy patients exhibited overlapping onset and offset response amplitudes.
- The difference between onset and offset responses was greatest centrally and decreased with eccentricity.
- Onset responses (visual field, mfERG) were poorest centrally, while offset responses showed the opposite pattern.
Conclusions:
- The findings support a selective loss of ON-pathway responses in cone dystrophy.
- Differential responses to onset and offset stimuli provide evidence for ON-system vulnerability in CD.
- This selective deficit may explain the clinical presentation of cone dystrophy.
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