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The need for precision in visual acuity assessment for low vision research led to the design of the Bailey-Lovie letter chart. This paper describes the decisions behind the design principles used and how the logarithmic progression of sizes led to the development of the logMAR designation of visual acuity and the improved sensitivity gained from letter-by-letter scoring. While the principles have since been adopted by most major clinical research studies and for use in most low vision clinics, use of charts of this design and application of letter-by-letter scoring are also important for the accurate assessment of visual acuity in any clinical setting. We discuss the test protocols that should be applied to visual acuity testing and the use of other tests for assessing profound low vision when the limits of visual acuity measurement by letter charts are reached.

A more scientific method than the Snellen chart for determining visual acuity is imperative for research studies and is desirable in many clinical situations. The psychometric method using the constant contour interaction S-chart of Flom has been regarded as an accurate and reliable visual acuity measure and has been used widely for research purposes. This paper compares visual acuity measured by the S-chart with that measured by the Snellen and Bailey-Lovie charts. The results indicate that the Baily-Lovie chart is a valid, reliable and rapid method of measuring threshold visual acuity for research purposes.

The LVP-FVQ is a reliable, valid, and simple questionnaire that can be used to measure functional vision in visually impaired children in developing countries such as India.

As the size of a binocular central scotoma increases, mobility performance decreases.