Rate of Parental Consanguineous Marriage among Patients with Visual Impairments in Turkey

We aimed to describe the causes, characteristics, and rate of parental consanguineous marriage associated with patients with visual impairments in Turkey. This study involved 236 patients with visual impairments. The 10th revision of the International Classification of Diseases was used to categorize the causes of visual impairments (based on the main cause in both eyes). The mean age of the patients was 38.5 ± 24.2 years (range, 6-95 years), and most were in the 15-30-year age group (35.6%). There were more male patients (65%) than female patients. Blindness, severe visual impairment, and mild to moderate visual impairment were observed in 30 (12.7%), 84 (35.6%), and 122 (51.6%) patients, respectively. Choroidal and retinal diseases were identified as the main underlying cause of visual impairment (62.7%), followed by nystagmus (23.7%), optic tract and nerve diseases (11.0%), congenital cataracts (0.8%), and glaucoma (1.7%). Parental consanguinity was present for 26.3% of the patients, and it was significantly more common in the 15-30-year age group (50%) compared to the other age groups. In Turkey, the main cause of visual impairment was choroid and retinal diseases in all the age groups above 14 years, while nystagmus was the most common cause in the age group below 15 years. Parental consanguinity was significantly higher among the patients with macular dystrophy and those with retinitis pigmentosa than with retinopathy of prematurity, optic nerve diseases, age-related macular degeneration, and diabetic retinopathy. Genetic factors are known to be involved in the development of these diseases, indicating that the issue of consanguineous marriage remains a problem in Turkey.