a. What does the alternating cover test show (see picture above)? b. Why is it more desirable for a person to have a small amount of exophoria at 40 cm than to have a small amount of esophoria at the same distance?
b. Why is it more desirable for a person to have a small amount of exophoria at 40 cm than to have a small amount of esophoria at the same distance?
Answer to a Esophoria. The eye is orthophoric in the primary position but with alternative cover test there is esophoria. Answer to b Exophoria requires the use of positive fusional vergence, which is a well-developed function, while esophoria requires the use of negative fusional vergence, which is not a well-developed function. The constant use of negative fusional vergence may results in headache or other forms of asthenopia. Go to station 1 Return to mock examination 7
