In humans, multiple tests exist for functional vision measurement.
7–9 These include microperimetry, best-corrected visual acuity (BCVA), contrast sensitivity (CS), reading speed, and visual-guided mobility tests.
7–9 To correctly extrapolate results of preclinical testing of a drug from animals to humans, it is important that tests of functional vision are also performed as part of preclinical animal studies. However, some of the routine visual acuity-based tests that require structured linguistic abilities such as BCVA and reading speed are not feasible in animals. Some of the more frequently used functional vision tests for rodents include visual water test, optomotor reflex test, pattern electroretinography, and pattern visual evoked potentials.
10 Most of these tests, however, measure what is called the pattern vision—an ability of our visual system to recognize stimuli arranged in a certain pattern and do not provide a complete picture of functional vision.
11 Furthermore, some of these tests require sedation in large animals, such as nonhuman primates, swine, or canines, or are not feasible or reliable because of animal size and their ability to use nonvisual cues, such as smell, for navigation.
12,13 Previously, tests have been developed to determine operant-based contrast sensitivity and visual texture modulation in monkeys, as well as visual acuity of pigs at different light intensities.
14–16 More recently, significant success has been made using a visually guided navigation test of large animals for the assessment of cell and gene therapies.
17,18 In fact, some of this work led to the development of the first US Food and Drug Administration (FDA)–approved gene therapy for a deficiency of RPE65 leading to childhood-onset blindness, underscoring the importance of developing such tests.
3 However, one challenge with a visually guided navigation test is the confounding issue of animals’ ability to use non-vision-related olfactory abilities for navigation. It requires additional evaluation of parameters such as position of animals’ head during test performance. In any case, this is a powerful test for functional vision in large animals but does not allow for discrimination of fine changes in vision.