Pupil size following dark adaptation in patients with retinitis pigmentosa
Braz. j. med. biol. res
;
34(8): 1037-1040, Aug. 2001. ilus
Article
in English
| LILACS
| ID: lil-290153
RESUMO
According to the equivalent light hypothesis, molecular defects in the photoreceptor lead to a continuous activation of the photoreceptor cascade in a manner equivalent to real light. The consequences in diseases such as retinitis pigmentosa (RP) are as disruptive to the cells as real light. Two forms of the equivalent light hypothesis can be distinguished strong - mutations in rhodopsin or other cascade proteins in some forms of RP continuously excite the visual phototransduction cascade; weak - disruption of outer segments in all patients with RP eliminates circulating dark current and blocks neurotransmitter release in a manner similar to real light. Both forms of the equivalent light hypothesis predict that pupils of patients with RP will be constricted like those of normal subjects in the light. The purpose of this study was to test the equivalent light hypothesis by determining whether steady-state pupil diameter following full dark adaptation is abnormally small in any of a sample of patients with RP. Thirty-five patients with RP and 15 normal subjects were tested. Direct steady-state pupillometric measures were obtained from one eye in a full-field dome after 45 min of dark adaptation by videotaping the pupil with an infrared camera. Mean pupil diameter in the dark was comparable (t = -0.15, P = 0.88) between patients with RP (6.85 Ý 0.58 mm) and normal subjects (6.82 Ý 0.76 mm). The results of the present study are clearly counter to the prediction of the second (weaker) form of the equivalent light hypothesis:
Full text:
Available
Index:
LILACS (Americas)
Main subject:
Pupil
/
Retinitis Pigmentosa
/
Dark Adaptation
/
Light
Type of study:
Observational study
/
Risk factors
Limits:
Adult
/
Humans
Language:
English
Journal:
Braz. j. med. biol. res
Journal subject:
Biology
/
Medicine
Year:
2001
Type:
Article
/
Project document
Affiliation country:
United States
Institution/Affiliation country:
Retina Foundation of the Southwest/US
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