Developments in Vision Testing Technologies

The most basic and important tool the Ophthalmologist has to assess an individual’s eye health is vision testing. Subtle differences between visits in visual acuity, contrast sensitivity, glare and other indicators of visual performance may yield important clues on the progression of an array of diseases. Unfortunately, vision testing is often not considered to be a critical part of an eye examination by many busy Eye M.D.s, since the process can be a cumbersome, frustrating experience. Vision testing is an art and science onto itself, and inexperienced eye care professionals may spend 10-20 minutes on vision testing. This length of time, while spent for an important cause, prevents a busy practice from running smoothly, and patients themselves often become frustrated for spending too long on a seemingly trivial part of the examination. On the other hand, some subspecialty eye clinics literally spend seconds to get an estimate of the vision before proceeding on to the clinical examination. Clearly, both patients and physicians could benefit from ways to assess vision more quickly yet accurately.

While visual acuity testing is straightforward, contrast sensitivity and glare testing sometimes can be a challenge to assess through traditional methods. Contrast sensitivity testing measures the patient’s ability to recognize differences in both size and contrast of an optotype. The test determines a patient’s threshold for contrast detection, which is the lowest contrast at which a pattern is seen. Typically, a patient is asked to identify which way a series of stripes is tilted; individuals who can determine the direction of very light, very thin bars are judged to have excellent contrast sensitivity. Glare testing usually involves reading an optotype under conditions that simulate ‘glare’ – that is, with backlit acuity testing (BAT). Individuals whose visual acuity decreases with a backlight may have, among other diseases, a posterior subcapsular cataract causing difficulty seeing with glare.

An ideal vision tester would be able to assess visual acuity, potential visual acuity, contrast sensitivity, glare and color. Such a machine would be able to automatically refract and allow small refinements in sphere and cylinder to provide the optimal subjective refraction. The entire process would be complete within seconds to a few minutes. Ideally, the vision tester would be portable or semi-portable to be able to transport for field testing, school screenings, or even for use in international ophthalmology. The readout would be simple to interpret for both the physician and the patient.

Traditionally, each part of the vision assessment is performed separately, and each type of test is chosen to provide needed information in the given amount of time. For example, a patient who presents with visually significant cataracts may undergo visual acuity and glare testing, but the ophthalmologist may not see a need to assess contrast sensitivity or color on that particular visit. On the other hand, a patient presenting post – LASIK with vague visual complaints may have visual acuity, glare and contrast sensitivity measured. A directed vision testing approach - as opposed to a complete vision assessment - is chosen in part because many ophthalmologists find it impractical to tackle the entire spectrum of vision assessment techniques on any given appointment. However, what if a vision tester was available that incorporated all of the available vision assessment tools? Would ophthalmologists be able to obtain a more complete understanding of their patients’ visual status? While such a vision tester does not exist today, several commercially – available testers have begun incorporating multiple features into a single machine.

For example, some currently available vision testers can perform distance and near visual acuity testing, glare testing, contrast sensitivity analysis and potential acuity testing all in one sitting. Several instruments also incorporate peripheral visual field analysis in their testers. A variety of vision testers perform automated refractometry to assist the eye care professional in a busy clinical setting.

Incorporation of vision testing techniques into single machines promises to transform vision assessment from a labor – intensive, frustrating experience into a rapid, high – yield measurement integral to an ophthalmologist’s increasingly busy practice. The next generation of vision testers likely will incorporate most, if not all, of the parts of vision assessment into an ultra – rapid screening instrument. In this scenario, patients will be assessed with minimal help from ancillary staff, and report to their ophthalmologist with a complete vision assessment printout detailing not only their visual acuity but also results such as contrast sensitivity and glare testing data. Such complete assessments hopefully will benefit both the patient and the Eye M.D. by providing a wealth of useful information in a short period of time.