Article
Contrast sensitivity testing comes of age
Contrast sensitivity testing has long been a technology that clinicians know has value, but the interpretation and implementation of the results were not clear. A number of recent scientific publications and new FDA standards have paved the way for contrast sensitivity to be more easily incorporated into routine clinical practice. This article traces the background of contrast sensitivity testing and some of the exciting developments related to its use in FDA clinical trials, for the management of "quality of vision," and for the monitoring and treatment of disease.
Contrast sensitivity testing has long been a technology that clinicians know has value, but the interpretation and implementation of the results were not clear. A number of recent scientific publications and new FDA standards have paved the way for contrast sensitivity to be more easily incorporated into routine clinical practice. This article traces the background of contrast sensitivity testing and some of the exciting developments related to its use in FDA clinical trials, for the management of "quality of vision," and for the monitoring and treatment of disease.
Historical background Thirty years have passed since contrast sensitivity was first used clinically to evaluate a vision problem. However, it was not an ophthalmologist who first found this technology useful, but rather a Columbia University-based neurologist, Ivan Bodis-Wolner, MD.
Some of Dr. Bodis-Wolner's patients were car accident victims who complained of vague visual disturbances, but they retained good acuity. He learned about contrast sensitivity from European scientists and decided to measure this in his patients. He was surprised to find that the loss of vision in his patients could be easily detected with contrast sensitivity testing, but they were completely hidden from the acuity measurements. Patients retained excellent acuity, but yet had significant cerebral lesions in the occipital area. Dr. Bodis-Wolner published this work in 1972 in Science.
Numerous research publications and wide clinical use show that contrast sensitivity is useful for determining the vision loss from the cataract, the vision recovery after surgery, and the need for YAG surgery related to posterior subcapsular (PSC) opacification. Acuity is relatively insensitive to cataract vision loss, until the cataract is well advanced. This is particularly true for PSC cataracts that cause considerable light scatter.
When reimbursement for cataract surgery fell in the late 1980s, so did the rapid adoption of contrast sensitivity technology. Now, as contrast sensitivity has become more recognized as the best tool for measuring quality of vision, many cataract surgeons have "re-adopted" the testing for routine cataract evaluation and documentation.
FDA steps in The FDA developed an interest in contrast sensitivity in the late 1980s and early 1990s during the emergence of multifocal IOLs and the excimer lasers. Agency scientists noted that many patients who had undergone procedures with some of these new ophthalmic devices retained good acuity, but in some cases they had poor quality of vision.
In 1991, the FDA began to require ophthalmic device companies to use contrast sensitivity to evaluate new devices when obtaining market approval. No standards existed for contrast sensitivity and the ophthalmic device companies began using many different forms of tests.
These tests included sine-wave grating types of tests, such as the VectorVision CSV-1000 or StereoOptical FACT chart, letter contrast sensitivity tests, such as the Pelli-Robson, or low-contrast acuity tests, such as the Reagan Letters or Holladay Cards. Since many of the companies provided the contrast sensitivity results in these different test formats, the results were hard to interpret and standardize. In the late 1990s, the FDA embarked on a mission to standardize contrast sensitivity testing for clinical trials.
Setting standards Recently, the FDA has finalized the standards for contrast sensitivity testing. The agency has determined that sine-wave grating tests are the most sensitive and accurate for evaluating new ophthalmic devices. Letter contrast sensitivity tests and low-contrast acuity were rejected for a variety of reasons. Currently the standards for FDA clinical trials are:
Numerous publications are now surfacing using these standards, which allow the comparison of results from different studies and different devices. These standards also allow the clinicians to use contrast sensitivity for routine patient evaluation and compare their results with other clinicians and the published literature.
