PURPOSE Prisms used for field expansion are limited by the optical scotoma at a prism apex (apical scotoma). For a patient with two functioning eyes, fitting prisms unilaterally allows the other eye to compensate for the apical scotoma. A monocular patient's field loss cannot be expanded with a conventional or Fresnel prism because of the apical scotoma. A newly invented optical device, the mul...

The absence of short-wave-sensitive (S-) cones in the human foveola normally goes unnoticed, but the resulting foveal S-cone, or blue, scotoma can be visualized as the negative afterimage of a short-wavelength adapting field on a larger white background. The afterimage has an annular shape with a lighter inner region that corresponds to Maxwell's spot, and a small bright spot in the center corr...

PURPOSE To investigate the effects of age-related macular degeneration (ARMD) on mobility performance and to identify the vision determinants of mobility in subjects with ARMD. METHODS Walking speed and the number of obstacle contacts made on a 79-m indoor mobility course were measured in 21 subjects with ARMD and 11 age-matched subjects with normal vision. The mobility measures were transfor...

PURPOSE No prismatic solution for peripheral field loss (PFL) has gained widespread acceptance. Field extended by prisms has a corresponding optical scotoma at the prism apices. True expansion can be achieved when each eye is given a different view (through visual confusion). We analyze the effects of apical scotomas and binocular visual confusion in different designs to identify constraints on...

Communication impairments pose a major threat to an individual's quality of life. However, the impact of visual impairments on communication is not well understood, despite the important role that vision plays in the perception of speech. Here we present 2 experiments examining the impact of discrete central scotomas on speech perception. In the first experiment, 4 patients with central vision ...

BACKGROUND Recent years have seen a marked increase in laser-pointerrelated injuries, which sometimes involve severe retinal damage and irreversible visual impairment. These injuries are often caused by untested or incorrectly classified devices that are freely available over the Internet. METHODS We reviewed pertinent publications retrieved by a systematic search in the PubMed and Web of Sci...

Crowding impairs the perception of form in peripheral vision. It is likely to be a key limiting factor of form vision in patients without central vision. Crowding has been extensively studied in normally sighted individuals, typically with a stimulus duration of a few hundred milliseconds to avoid eye movements. These restricted testing conditions do not reflect the natural behavior of a patien...