Adult Human Ocular Volume: Scaling to Body Size and Composition

Objectives: Little is currently known on how human ocular volume (OV) relates to body size or composition across adult men and women. This gap was filled in an exploratory study on the path to developing anthropological and physiological models by measuring OV in young healthy adults and related brain, head, and body mass along with major body components. Methods: Thirty-six men and 44 women, ages 20-35 yrs, were evaluated with magnetic resonance imaging and dual-energy X-ray absorptiometry that provided estimates of OV, brain, head, fat, lean soft tissue (LST), and bone mineral mass. Associations between OV and other components were evaluated first followed by development of allometric models relating OV and other components to body size as defined by stature. Results: Mean OV was non-significantly larger in men (X ± SD; 6.35 ± 0.69 cm3) than in women (6.26 ± 0.53 cm3; P=NS), although OV in women was significantly larger relative to brain and head mass than in men (both p<0.001). While larger body components (e.g., LST) scaled to height with powers as expected from previous studies, these associations for OV were weak or non-significant. Our findings are consistent with a systematic review of earlier autopsy, surgical, and imaging OV studies. Conclusions: Unlike most other lean tissues and organs, the absolute eye volume is largely independent of a person’s sex and body size or composition. As a small anatomic body component, the adult human eye appears to function within relatively narrow dimensional constraints. Future larger sample studies are needed to explore age and racial/ethnic differences in OV.