Early onset of presbyopia.

Of the 800 presbyopes studied, 286 (35.75%) entered presbyopia at or before the age of 38 years. About 63% of these patients lived in rural areas and 37% in urban areas. Environmental conditions including high average temperature, much ultraviolet radiation, chronic deficiency of essential amino acids, and exposure to toxic factors, particularly hair dye, may play a significant role in precipitating the early onset of presbyopia.