Neuro-optometry and Binocular Vision
Core concepts
Understand the anatomy and clinical testing of cranial nerves III, IV, and VI, and the patterns of strabismus and diplopia they produce. Know how to evaluate binocular vision: cover test, alternate cover test, Maddox rod, Worth four-dot, and stereopsis testing. Recognize accommodative and convergence disorders (convergence insufficiency, accommodative insufficiency, accommodative excess). Be familiar with supranuclear and internuclear lesions, such as internuclear ophthalmoplegia, and with pupil abnormalities (Horner syndrome, Adie tonic pupil, relative afferent pupillary defect).
Traps
Questions often reverse the affected muscle in a palsy. Remember CN IV palsy causes vertical diplopia worse on downgaze and contralateral head tilt; CN VI palsy causes esotropia worse on ipsilateral gaze. Distinguish comitant from incomitant deviations. Do not confuse convergence insufficiency (near exophoria, reduced near point of convergence) with divergence excess.
Worked rule of thumb
For diplopia, use the "red lens" or Maddox rod to identify the deviating eye and direction. If the deviation increases in one gaze direction, the affected muscle is the one acting in that direction. For convergence insufficiency, prescribe base-in prism or vision therapy and measure the near point of convergence before and after treatment.