Fovea Case Study

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How does visual acuity vary across the visual field? What is the anatomical basis for this reduction?
Visual acuity was found to decrease as the subjects moved across the visual field. Overall, visual acuity was found to be best when the target being viewed was in the centre of the visual field. According to Levin, cone density is highest at the fovea. As eccentricity from fovea increases, convergence of cone photoreceptors onto ganglion cells also increases, leading to a reduction in sharp images.

b) Use the rotating polaroid system to view Haidinger’s brushes, which appear as black rotating propeller blades. Observe how as you change fixation the location of the brushes changes also. What is the anatomical basis for this entopic phenomenon? …show more content…
Draw a labeled diagram showing the different layers of the retina. How does the structure of the retina vary at the fovea?

The foveal structure differs from other parts of the retina, as it is pitted. This indentation within the retinal tissue produces a pit which consequently acts as a concave mirror. It is well known that the fovea contains the highest density of cones within the retina. As a result of this, the light at the center of the visual field is focused onto the retina, producing the clearest and sharpest image.

d) Use the direct ophthalmoscope to view the macular region of the retina. Ask your subject to stare directly at the light. What do you observe, and what is the anatomical cause of this effect?
The macula appeared to be one of the darkest regions of the retinal tissue, which made it slightly easier to identify when viewing through the ophthalmoscope. The macula was viewed front on to the subject, using a dim, circular light. Once the macula was examined, the subject was asked to look directly at the light source from the ophthalmoscope. This caused the foveal reflex to appear (as a small, bright almost star-like spot within the

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