The concept of the average eye

R.D. Van Gool
2005 African Vision and Eye Health  
For most quantitative studies one needs to calculate an average. In the case of refraction an average is readily computed as the arithmetic average of dioptric power matrices. Refraction, however, is only one aspect of the first-order optical character of an eye. The question is: How does one determine an average that rep-resents the average optical character of a set of eyes completely to first order? The exponen-tial-mean-log transference has been proposed recently but it is not without its
more » ... fficulties. There are four matrices, naturally related to the transference and called the characteristics or characteristic matrices, whose mathematical features suggest that they may provide alterna-tive solutions to the problem of the average eye. Accordingly the purpose of this paper is to propose averages based on these characteristics, to examine their nature and to calculate and compare them in the case of a particular sample of 30 eyes. The eyes may be stigmatic or astig-matic and component elements may be centred or decentred. None turns out to be a perfect average. One of the four averages (that based on one of the two mixed characteristics) is proba-bly of little or no use in the context of eyes. The other three, particularly the point-characteristic average, seem to be potentially useful.
doi:10.4102/aveh.v64i2.212 fatcat:a5cqf6rv4fe27fihad5rzxvu44