[4] Reduction in melanin production specifically in the peripheral retina during embryonic development can trigger other symptoms such as abnormal nerve fiber projection that causes defects in neuronal migration that interrupts visual pathways and creates reduced visual acuity in the range of 20/60 to 20/400.
This protein coding gene produces tyrosinase, an enzyme which catalyzes a total of three steps in the conversion of tyrosine to the end product, melanin.
[8] OCA Type 1A is an autosomal recessive condition, meaning there is a homozygous or compound heterozygous mutation related to the TYR gene.
The mutations on this gene lead to a complete lack of tyrosinase activity as the inactive enzyme is produced.
[10] The seven types are not evenly distributed amongst ethnic groups with OCA1 being the subtype most prominent in Caucasians - "accounting for approximately 50% of cases worldwide.
"[10][3][11] Previously, diagnosis was done from observation of hypopigmentation which is obvious at birth, but this is now insufficient early on to distinguish between the seven major types of OCA.
[2] Prenatal testing has been achieved through fetal skin biopsy followed by subsequent histologic and electron microscope examination for melanin levels.
[12] Clinical findings have established that molecular genetic testing of TYR,[12] the gene encoding tyrosinase, can distinguish between 1A and 1B because the phenotypes can be identical during the first year of life.
[2] The histological approach for prenatal diagnosis is useful for all families at risk for OCA1 whereas the molecular genetic test is only helpful when at least one mutation is known.
[4] Individuals affected by OCA1A should be attentive to the amount of sun exposure they experience and wear proper protection such as clothing that covers the skin.
[1] Additionally, symptoms that could be heterozygous mutations, such as abnormal iris translucency occurred in 70% of the parents and children of individuals affected with this condition.