A study of the depth of hemianopic field defects for optimizing computerized perimetry

Abstract

Although the test point pattern of the computerized perimeter ‘Competer’ has been enlarged, focal diagnosis is difficult in many cases since the area outside 35° of eccentricity cannot be examined. Further improvements of the instrument requires knowledge about the depth at various eccentricities of common neurological field defects. This was calculated in 41 eyes with chiasmal defects and in 36 eyes with suprageniculate defects. Twenty-six normal visual fields were used for comparison. Generally, the central area was more or less intact in relative hemianopic defects, probably because of the large proportion of macular fibres in the visual pathway, and the depth was found to increase towards the mid-periphery. These results indicate that with a simplified test strategy for the mid-peripheral area, few hemianopic defects would be missed by the ‘Competer’. In this way, the examination of the mid-peripheral area could be shortened. Without prolonging the total test session, which is already 15–20 minutes per eye, focal diagnosis could be facilitated by adding and testing a number of points in the area outside 35° of eccentricity.

Key Words:

• computerized perimetry
• bitemporal hemianopic defects
• homonymous hemianopic defects
• depth
• eccentricity
• macular sparing
• visual pathway
• visual acuity