|Title||WHICH ARE THE MOST 'INFORMATIVE' ACUITY TESTS FOR INFANTS?|
|Author, Co-Author||T. Candy, Martin Banks|
|Abstract|| PURPOSE. There are many different acuity tests available to the clinician, especially when assessing infants and children. They involve a variety of tasks such as recognition, matching or detection and classically, have been calibrated empirically using large numbers of patients. This study directly analyses the spatial frequency content of different tests and compares their sensitivity to blur. In this way the suitability of actual stimulus optotypes can be assessed in isolation from any complex cognitive requirements. METHOD. Grating, Tumbling E, picture and letter acuity tests were considered. Two-dimensional Fourier analyses were performed on each optotype of each test. It is the differences between the optotypes, within a test, which represents the information available for completing the task and the effect of blur upon this 'difference' information was calculated.
RESULTS. As might be predicted, the more complex the optotype, the more complex the spatial frequency content was found to be. When considering the 'difference' or discrimination information, complex pictorial tests were often contaminated by low frequency differences which could be used to solve the test. This low frequency 'larger detail' made these tests less able to detect blur.
CONCLUSIONS. This study demonstrates that when trying to test an acuity limit the crucial question is not 'what size is the smallest detail in the optotype?' but 'what size is the largest detail in the difference between the optotype choices?'. The present technique enables this to be quantified and compared across tests, resulting in significant implications for both standardisation and validation of clinical acuity tests.SUPPORT. T.R. Candy is supported by an AOF Ezell Fellowship and the laboratory by NIH HD19927.
|Affiliation of Co-Authors|