The eye, refractive errors and their significance and correction, accommodation and presbyopia, and the use of different types of multifocal lenses are first discussed. The functioning of the binocular visual system is considered, particularly in relation to efficient visual performance. Convergence fatigue is of special importance, as is the common association of binocular instability and discomfort with photophobia. Possible reasons for complaints of discomfort with lighting using fluorescent lamps are considered, and the need for closer cooperation between those concerned with different aspects of vision is indicated. Some typical case histories are described in an appendix.
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