MONOCULAR DIPLOPIA OCCURRING IN CASES OF SQUINT

Abstract

MNIONOCULAR diplopia whichissometimes complained ofandat other times canbeevokedartificially, isfoundincasesofsquint whichhavenophysical defect inthelenses, corneae, pupils, retina etc., toaccount forthisphenomenon, buthavesomeabnormal retinal correspondence. Asearly as1854, vonGraefe hadremarked upontheanomalous diplopia whichoccurred after cases ofoperationforsquint, andthatinsomecases thediplopia wouldchange frommomenttomoment,beingattimescrossed andatothers uncrossed. Thischangeinthediplopia wasduetothefact that inthese cases whichhavebothanabnormal andanormalcorrespondence, eachretinal pointhastwospacevalues according to whether theabnormal correspondence orthenormalcorrespondenceisbeingused.ButitwasJaval, who,duetothebringing toconsciousness ofthetwospacevalues simultaneously, actually notedafurther stageofthisphenomenon anddescribed thefirst caseofmonocular diplopia occurring ina squinting child. His case, whichheexamined in1864, wasthatofanalternating squint whichdated frombirth andhadsomeweakness oftheleft external rectus. On examining thepatient's binocular vision bymeansof a stereoscope, Javal foundthathehadmonocular diplopia with theleft eye,andconcluded thatthepatient sawoneimagein correct projection andtheother imageinfalse projection. Unfortunately, thiscase, asmanycasesofsquint do,disappeared after sixweeks, andwhenJaval wrotetofindoutwhathadhappened, thepatient replied thatvonGraefe hadoperated uponhim andthathewasnowsuffering fromacrossed binocular diplopia. Javal, inhisbookonsquint, quotes afewfurther casesofthis monocular diplopia, usually associated withpoorvisual acuity inthesquinting eye. Classen, in1870, noted thesecond example anddescribed thecase ofapatient aged28years, whohaddiplopia following anoperation foraright convergent squint associated withamblyopia andnoted thatattimesthediplopia wascrossed andatothers uncrossed. After operation, oncovering theleft eyeandfixing withtheright eyeandthenuncovering theleft eyequickly, thepatient sawthree imagesofthelight, acentral clear oneseenbytheleft eyeand twofaint imagesseenbytheright eye,oneontheleft andone ontheright oftheclear image.Theauthor, however, simply says