The far interpupillary distance. A gender-specific variation with advancing age.

A knowledge of the magnitude of the far interpupillary distance (FIPD) in relation to a specific population is of clinical, practical and theoretical interest. A FIPD database is presented here, comprising material collated from the spectacle dispensing records of n = 1800 subjects seen in routine optometric practice. All measurements were taken by the author on healthy Caucasian (white, Northern European) males and females. The data were equi-partitioned either across three age bands (16-25, 26-40, 41-65 years: mixed refractive types, total n = 900) or between the three distance refractive types (emmetropia, hypermetropia, myopia: all subjects aged between 41-65 years, total n = 900). A consistent gender difference (male > female) was confirmed throughout this material, irrespective of age group; refractive type, however, had no influence on the magnitude of this facial parameter. Summary results of this anthropometric survey are presented in tabular form, facilitating reference by ophthalmic and dental clinicians and by the designers of binocular optical instruments. There was also revealed evidence of a gender-specific pattern of change in the FIPD variable with advancing age. An approximately 3% increase in the magnitude of the human FIPD from the mid-teens to later middle age was attained in males by early middle age, being little altered thereafter: in contrast females continued to record an increase in this facial parameter into later middle age. An explanation for this hitherto unremarked feature of human facial anthropometry might be sought in the gender-specific changes post-puberty of the cranial skeletal anatomy and in the soft tissues of the orbital region.