An optometrist uses a powerful ophthalmic penlight to examine a patient's pupillary light reflex. Initially, the patient sits in a dimly lit examination room, and then the penlight is shone directly into their left eye.
Diagram X and Diagram Y show the front view of the patient's iris and pupil under these two different lighting conditions.
Diagram Y shows the patient's eye when the bright penlight is shone directly into it. Explain how you can deduce this from Diagram Y, and describe the antagonistic muscle action within the iris that achieves this physiological change.
The optometrist then assesses the refractive errors of two other patients, Patient A and Patient B. The diagrams below show how parallel light rays from a distant object are focused in their eyes without correction.
Diagnose the specific vision defect affecting each patient:
- Patient A
- Patient B
Determine the type of corrective lens required for each patient, and explain the physical mechanism by which each lens corrects the focal point to restore normal vision.