The effectivity of Fresnel prisms for visual field enhancement.

An objective method for placement of Fresnel prisms has been used to enhance constricted visual fields at the Eastern Blind Rehabilitation Center in West Haven, CT since 1975. To study the effectiveness of this method, 22 patients fitted with prisms since 1986 participated in a survey regarding their level of satisfaction with the prisms. Nineteen out of 22 patients continued to wear the prisms successfully, resulting in a retention rate of 86.3 percent. Of those still wearing the prisms, their reported overall satisfaction level averaged 3.63 on a scale of 1-4 (4 representing very satisfied). The reported satisfaction levels of the patients wearing the prisms were statistically analyzed with respect to pathology, months of wear, age of the patient, binocular versus monocular fitting, size of the residual field, visual acuity, the power of the prism used, and ocular rotation to enter the prism. No significant predictive value was found with any of these variables in trying to determine the level of satisfaction. However, this may be due to the small sample size. These same variables were used in comparing the patients who continued to wear the prisms with the patients who had discontinued prism use. None of these variables was found to be significant in predicting a successful outcome, possibly in part to small sample size, and the low number of unsuccessful patients. In an effort to make improvements on the existing methods being used for field enhancement, questions were asked regarding technical use of the prisms, mobility with the prisms, the spectacle carrier lens, and the maintenance of the prisms.(ABSTRACT TRUNCATED AT 250 WORDS)