Reliability and variability of visual acuity assessments

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Estimation of visual acuity is fundamental to any ophthalmological assessment, and with new treatment options, such as retinal prostheses and gene therapy, the accurate monitoring of acuity is becoming increasingly important. However, acuity measurements are not as straightforward as the first glance suggests. Studies in other areas of visual performance have demonstrated that the outcome of a measurement depends substantially on factors beyond the physiological parameter to be assessed. Many of these factors are related to the decision process in individual subjects during identification of the optotypes. Other issues include the willingness of the patient to perform a test (potential malingering), and the ability of an acuity test to predict real-life performance of a patient depending on the specific disease. We propose a series of experiments that will shed light on these issues with the aim of understanding and ultimately reducing sources of variability in acuity assessments. One fork of the project will assess discrepancies between VEP-based and psychophysical acuity estimates that occur in certain cases, e.g. in amblyopia. In a second fork we will evaluate applications of cognitive event-related potentials in patients. The third fork will focus on the factors determining the outcome of the subjective acuity estimates, which are still the gold standard.