A study in the US found at least 30 per cent of people over age 75 have differing visual requirements between eyes – or anisometropia. The study also noted anisometropia becomes more prevalent with age – previous studies showed its prevalence in children is two to four per cent. The condition was found to be at least 10 times more common in those over 75 years of age.
Researchers from University of California, Berkeley followed 118 older adults over 12 years-from an average age of 67 to 79 years at the end of the study.
During the study period, the prevalence of anisometropia increased significantly. For each of the four prescription components, the prevalence of anisometropia approximately doubled. As the participants approached 80 years of age, 32 per cent met the study definition of anisometropia.
Most cases were related to differing degrees of hyperopia between eyes. Others were caused by early but unequal blurring of the lens of the eye, which did not meet the usual clinical definition of cataracts.
The researchers emphasised the importance of appropriate vision correction in both eyes for older adults, especially at more advanced ages.