[Focusing strength and a subjective method for determining refraction]

Three hundred and seventy-four eyes were examined by a subjective method, by using trial lenses in natural accommodation. This yielded the following distribution of clinical refraction: hypermetropia (43.6%), emmetropia (30.8%), myopia (12.8%), and astigmatism (12.8%). The classical subjective method of refractometry is based on the schematic eye having no focusing strength. The currently available data by a number of authors show that the focusing strength of more than 0.5 diopters is typical of the human eye, which affects the results of refractometry. When the collecting glass +0.25 D or +0.5 D is applied, the eye with a visual acuity of 1.0 or more retains the level of vision due to the holding the focusing strength across the retina rather than the accommodation strength. By taking in account the correction, the distribution in the study group was as follows: emmetropia (73.0%), myopia (12.8%), astigmatism (12.8%), and hypermetropia (1.4%).