Abstract
Abstract: :
Purpose: To investigate the differences of keratometric power, axial length, and associated intraocular lens (IOL) powers among eight world populations. Methods: Biometry measurements from an urban United States population (n=157; Temple University Hospital, Philadelphia) and seven non–US populations (treated during surgical missions from 1997–2002) were compared. Those countries included the Dominican Republic (n=100), El Salvador (n=97), Ethiopia (n=109), Guyana (n=61), Honduras (n=81), Nicaragua (n=204), and Vietnam (n=100). Only adults (≥18 years old) were studied. Patients were excluded if they had conditions that distorted the ocular anatomy (e.g. previous ocular surgery). Certified ophthalmic technicians, using standardized instruments, measured axial length and keratometry in each patient. The SRK formula (A constant of 118.2) was used to calculate the associated PCIOL power to achieve emmetropia. One–way ANOVA was used to evaluate the data. This study is a follow–up to research presented in 2003. Results: Among the eight populations, there was a statistically significant difference in axial length, average keratometric power, and associated IOL power. Mean age was not statistically different among the groups. Mean axial lengths ranged from 23.64 mm to 22.73 mm. The groups, in order of longest to shortest eyes, were: US, Ethiopia, Guyana, Nicaragua, El Salvador, Dominican Republic, Honduras, and Vietnam. Among the groups, the average keratometric power ranged from 42.96D to 44.13D. The populations, in order from flattest to steepest corneas, were Nicaragua, Ethiopia, Guyana, Honduras, US, El Salvador, Vietnam, and Dominican Republic. Mean IOL power ranged from 19.77D to 21.87D among the eight groups; in order of lowest to highest, the groups were: US, Ethiopia, Guyana, El Salvador, Dominican Republic, Vietnam, Nicaragua, and Honduras. Conclusions: This study shows that corneal curvature, axial length, and IOL measurements may vary significantly between world populations. To our knowledge, this is one of the most extensive studies comparing these parameters between different groups. Ocular measurements and corresponding IOL powers of one population should not be applied directly to other populations. This research, and further studies of other world populations, may be useful for planning surgical missions involving those respective groups.
Keywords: cataract • clinical (human) or epidemiologic studies: biostatistics/epidemiology methodology