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Diagnosing protan heterozygosity using the Medmont C-100 colour vision test
1Department of Optometry and Vision Sciences, The University of Melbourne, 374 Cardigan Street, Carlton, VIC 3053, Australia.
Clinical & Experimental Optometry
|August 9, 2005
Summary
The Medmont C-100 test can clinically identify carriers of protan color vision deficiency, a genetic trait affecting 15% of Caucasian women. This test detects Schmidt's sign, indicating reduced red light sensitivity in heterozygotes.
Area of Science:
- Ophthalmology
- Genetics
- Vision Science
Background:
- 15% of Caucasian women are carriers of abnormal color vision genes.
- No current clinical method exists to identify these carriers.
- Protan heterozygotes may exhibit Schmidt's sign, a reduced luminous sensitivity to red light due to mosaicism.
Purpose of the Study:
- To evaluate the Medmont C-100 color vision test's ability to diagnose protan color vision deficiency carriers.
- To determine if the Medmont C-100 can detect Schmidt's sign.
Main Methods:
- Tested six known protan heterozygotes using the Medmont C-100.
- Assessed relative spectral sensitivity via flicker photometry.
- Tested daughters of known heterozygotes to assess carrier detection rates.
Main Results:
- All six protan heterozygotes achieved settings at or beyond the normal range on the Medmont C-100.
- Two previously reported cases of protan heterozygotes using the Medmont C-100 or OSCAR.
- 66% of likely heterozygote daughters tested also made protan settings.
Conclusions:
- The Medmont C-100 is effective for the clinical diagnosis of protan color vision deficiency carriers.
- The test's ability to differentiate protans and deutans aids in identifying carriers.
- Clinical application of the Medmont C-100 can improve carrier identification for genetic counseling.