Long-sightedness in old wild bonobos during grooming.

Some scientists have suggested that, among Hominidae, prolonged postmenopausal longevity evolved uniquely in humans [1], while others disagree [2]. There have, however, been few empirical studies on how physiological aging and somatic durability in humans compare to our closest relatives - chimpanzees and bonobos [3]. If prolonged lifespan is selected for in humans, physiological aging, including reproductive and somatic senescence, might be different for Pan and Homo. But it seems that the parameters of reproductive senescence, such as the age of having their final offspring and the number of years between generations, are not very different between chimpanzee and human females [4]. Here, we report evidence for five cases of long-sightedness (presbyopia) in old wild bonobos, exhibited during grooming. Our results suggest that senescence of the eye has not changed much since the divergence of Pan and Homo from their common ancestor.

Lens diameter and thickness as a function of age and pharmacologically stimulated accommodation in rhesus monkeys.

Uncertainty exists regarding accommodative and age changes in lens diameter and thickness in humans and monkeys. In this study, unaccommodated and accommodated refraction, lens diameter, and lens thickness were measured in rhesus monkeys across a range of ages. Iridectomized eyes were studied in 33 anesthetized monkeys aged 4-23 years. Refraction was measured using a Hartinger coincidence refractometer and lens thickness was measured with A-scan ultrasound. Lens diameters were measured with image analysis from slit-lamp images captured via a video camera while a saline filled, plano perfusion lens was placed on the cornea. Accommodation was pharmacologically stimulated with 2% pilocarpine via the perfusion lens in 21 of the monkeys and lens diameters were measured until a stable minimum was achieved. Refraction and lens thickness were measured again after the eye was accommodated. Unaccommodated lens thickness increased linearly with age by 0.029 mm/year while unaccommodated lens diameter showed no systematic change with age. Accommodative amplitude decreased by 0.462 D/year in response to pilocarpine. The accommodative increase in lens thickness decreased with age by 0.022 mm/year. The accommodative decrease in lens diameter declined linearly with age by 0.021 mm/year. Rhesus monkeys undergo the expected presbyopic changes including increasing lens thickness and a decreasing ability of the lens to undergo changes in thickness and diameter with accommodation, however without an age-related change in unaccommodated lens diameter. As in humans, the age-related decrease in accommodative amplitude in rhesus monkeys cannot be attributed to an age-related increase in lens diameter.