Ans: b (Diplopia usually present) Ref: Khurana, 4th ed, p. 321Squint is a tough topic as far as postgraduate entrance exam is concerned. But there is no way out.Atleast try to learn the difference between concomitant and inconcomitant squint byheart. That will help a lot.Squint:Misalignment of the visual axes of the two eyes is squintType:* Pseudostrabismus or apparent squint* Heterophoria or latent squintHeterotropia or manifest squint|||----- a) Concomitant----- b) InconcomitantApparent squint: Visual axes parallel but eyes seem to have squintPseudo esotropia (app. Convergent) -> e.g., prominent epicanthal foldPseudo exotropia (app divergent )-> e.g., hypertelorismHeterophoria (latent squint)Tendency of eyes to deviate is kept latent by fusion types* Exophoria-tendency to diverge* Esophoria - tendency to converge* Hyperphoria - tendency to deviate upwards* Hypophoria - tendency to deviate downwards* Cyclophoria - tendency to rotate around anteroposterior axisTreatment of heterophoria (decompensated)1. Correct refractive errors2. Orthoptic treatment3. Prescription of prism/ glasses4. Surgical treatmentHeterotropia (manifest squint) - Cover test confirms heterotropiaTypes:1. Concomitant: Amount of deviation in squinting eye constant in all directions of eye2. Incomitant: Amount of deviation varies in different directionsConcomitantIncomitant* Convergent (esotropia)* Divergent (exotropia)* Vertical (hypertropia)* Paralytic* 'A' and 'V' pattern heterotropias* Special ocular motility defects e.g., Duane retraction syndrome,Brown's oblique tendon sheath syndromeTests in paralytic squint* Diplopia charting* Hess screen test* Field of binocular vision* Forced duction testDifferentiating features between concomitant and incomitant squint Incomitant squintConcomitant squintMagnitudeVaries with eye positionSame in all positionDiplopiaPresentNormalOcular movementsRestrictedFullFalse projectionPresentAbsentAbnormal head posturePresentAbsentSecondary deviation> primary deviationEqual to primary deviationTreatment of manifest squint1. Treatment of the cause2. Conservative measures-vit B, steroids, wait and watch policy3. Treatment of diplopia4. Surgical treatmentLaws governing ocular movements:1. Herring's law of equal innervation2. Sherrington's law of reciprocal innervation