Measuring eye deviation using the alternating cover test and prism bar. One or other eye is always covered during the test. To elicit the presence or absence of a heterophoria along with type of deviation (eso-, exo-, hyper- and cyclophoria), effect of refractive correction, accommodation and CHP. The alternating cover test cannot differentiate between heterophoria and heterotropia but can be used to detect an intermittent heterotropia i.e. a heterophoria that changes (breaks down) to heterotropia on repeated cover testing. If the heterophoria breaks down it is likely to recover quickly during remainder of eye examination. The alternating cover test is fully dissociative and reveals the total deviation i.e. the habitual heterotropia or heterophoria experienced day-to-day by the patient. A prism bar can be used with increasing prism value and appropriate base direction until eye movement during alternating cover ceases.
The near point of convergence is the point where visual axes intersect under maximum convergence effort while binocular single vision is maintained. Some practitioners measure the near point of convergence routinely, but especially when a patent presents with near vision symptoms.
This is a measure of the maximum amount of accommodation an individual can exert. It can be described as the dioptric distance between the near and far points of accommodation and is usually measured using the RAF rule. It should be conducted monocularly and binocularly and may be repeated two or...
The measurement of stereoacuity is important as it gives an indication of the integrity of the binocular visual system. When the level of stereoacuity is within expected ranges then normal motor and sensory function are present. It is particularly useful for evaluating binocular vision in childre...
