Biomedical Engineering Reference
In-Depth Information
Left eye
visual field
Right eye
visual field
Left
Right
Optic nerve
B
Optic chiasm
C
Optic tract
Optic radiation
Striate cortex
E
FIgUre 10.18
Visual field deficits resulting from damage at different points along the primary visual pathway. The diagram
on the left illustrates the basic organization of the primary visual pathway and indicates the location of vari-
ous lesions. The right panels illustrate the visual field deficits associated with each lesion. From the top: loss
of vision in right eye. Bitemporal (heteronomous) hemianopsia. Left homonymous hemianopsia. Left superior
quadrantanopsia. Left homonymous hemianopsia with macular sparing.
allow for a detailed measurement of all of the areas with a diminished field of vision, but
they are able to show us field asymmetries and the most serious reductions.
10.2.2.10 Superior Perceptive Abilities
Several superior perceptive abilities can be examined during an optometric evaluation.
The most important ones are the skills of recognition of a target in a range of conditions
of crowding with interfering stimuli, with rotations and modifications to the enlarging
modulus, against a more or less confounding background; the short and long-term span
visual memory; and the spatial relationship among the target and between the targets and
the perceptual space (Denes and Pizzamiglio 1996). The perceptual span is also important.
It is the amount of space containing all of the information that can be acquired through a
single fixation (Greene, Pollatsek, Masserang, Lee, Rayner 2010). Sensitivity to perceptual
crowding is the degrading of the recognition of peripheral stimuli when surrounded by
other elements (Levi Dennis 2008; Nisha, Yeotikar, Sieu Khuu, Asper, Suttle 2011).
All of these skills and many others can be critical in some clinical cases. However, their
impact on the significance of the test is often reduced.
10.2.2.10.1 Methods
Most of these tests have a standardized procedure, but they often have to be carried out
with nonstandardized procedures to adapt them to the needs of the patient. This prevents
