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J Shankar, J Nair Sahni, R Hagan, SB Kaye, D Isherwood, M Brown, C Willoughby, A Fryer; Tyrosinase Activity and VER Asymmetry in Oculo-Cutaneous Albinism (OCA) . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1805.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To assess the correlation between tyrosinase activity and Visual Evoked Response (VER) asymmetry in patients with oculo-cutaneous albinism (OCA). Methods: Patients with clinically diagnosed OCA underwent electro-diagnostic testing (EDT) including flash and pattern reversal VER recording. The inter-hemispherical difference between the right and the left eyes were calculated for 200 ms and 150 ms using Pearson's correlation coefficient. Tyrosinase activity was assessed by observing microscopically, the production of melanin granules in hair roots after incubation for 8 hours in phosphate buffer (pH 6.8) containing 400mg/L of tyrosine alone or with 400mg/L of cysteine hydrochloride. The mean Pearson's correlation values were compared with the results of tyrosinase activity. Results: Twenty-five children with OCA had electro-diagnostic testing (EDT) of whom 19 had reliable and repeatable VERs for hemispherical asymmetry. The mean Pearson's correlation coefficient was -0.176 + 0.473 at 200 ms and -0.183 + 0.499 at 150 ms. Seven of the children with OCA were available for a reliable hair bulb test result to assess tyrosinase activity. There were five children with weakly positive tyrosinase activity and two who were tyrosinase negative. The mean Pearson's correlation in the weakly tyrosinase positive group was 0.130 + 0.563 at 200 ms and 0.124 + 0.561 at 150 ms. In the two patients who were tyrosinase negative OCA, the Pearson's correlation was - 0.824 and -0.579 at 200 ms and - 0.780 and -0.638 at 150 ms respectively. Conclusion: The mean Pearsons coefficient of correlation was negative in OCA. There was a trend for patients with Tyrosine negative OCA to have a greater degree of VER asymmetry as compared to patients who had weakly positive tyrosinase activity. Overall, there was a correlation between the degree of VER asymmetry and tyrosinase activity.
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