Prism Glasses (IMAGE) Mass Eye and Ear Caption This shows permanent peripheral prism glasses for a patient with left hemianopia, providing about 30 degrees of visual field expansion into the blind left visual field. Credit Mass. Eye and Ear/Schepens Eye Research Institute Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.