Purpose: To determine whether base-in prism glasses could diminish asthenopia, and improve reading abilities (speed, accuracy and comprehension).
Methods: All patients aged 8-18 years, from one practice, were examined and considered prospectively over a six month period. Ten percent (72) of these 703 patients met initial criteria of an exodeviation greater at near than distance and reading discomfort. At initial examination these 72 were asked to read orally, with and without base-in prisms. If the senior examiner noted they read faster and with fewer mistakes, and the patient reported increased reading comfort, then reading (only) glasses with 2 to 3 diopters base-in prism OU were prescribed. Of the 72, 33 were so treated. After 3 weeks they were given the Gray Oral Reading Test (GORT-3). This test has two equal parts which were administered one with, and one without, prisms. A subjective questionnaire was also administered.
Results: The overall mean improvement in reading speed, accuracy and comprehension on the GORT- 3 with base-in prisms, was from the 34th to the 66th percentile. The improvements in reading were "statistically significant" at p<.001. Patients also reported subjective improvement in asthenopic symptoms and headaches.
Conclusion: Base-in prism glasses improve subjective reading comfort and abilities (speed, accuracy and comprehension) in these patients.