The presbyopic add. II. Age-related trend and a gender difference.

New transverse clinical data are presented which confirm and extend earlier results to be found in the literature describing the time course of presbyopia-as indicated by the magnitude of the binocular spectacle add--in normally sighted male and and female Caucasian subjects. An initial steep increase in add requirement beginning in the early forties becomes relatively slower but still of significance beyond the mid-fifties. This observation is correlated with the age-related progressive decline in the amplitude of accommodation, itself a consequence of physiological changes in the crystalline lens and capsule. The continuing need for an increase, albeit at a reduced rate, in the positive near supplement beyond the mid-to-late fifties-by which time little or no useful accommodation is available-is now attributed to the visually disruptive effects within the high spatial frequency domain of progressive age-related lenticular changes. The magnification afforded by the positive add increases spatial grain and thereby enhances visibility of detail in an ageing visual system free of any gross senile visual pathology. A small but consistent gender difference is revealed in presbyopic corrections: physiological and physical bases are suggested for the observation that females require an add of greater magnitude than their age-matched male counterparts.