▁the ▁form ▁expected ▁on ▁the ▁basis ▁of ▁simple ▁geometry . ▁Rec ently , ▁pla us ible ▁explanation ▁has ▁been ▁provided ▁to ▁this ▁deviation , ▁showing ▁that ▁the ▁empir ical ▁hor opter ▁is ▁adapted ▁to ▁the ▁statistics ▁of ▁ret inal ▁dispar ities ▁normally ▁experienced ▁in ▁natural ▁environments . ▁In ▁this ▁way , ▁the ▁visual ▁system ▁is ▁able ▁to ▁optimize ▁its ▁resources ▁to ▁the ▁stim uli ▁that ▁are ▁more ▁likely ▁to ▁be ▁experienced . ▁ ▁The oret ical ▁Bin oc ular ▁Hor opter ▁▁ ▁Later ▁Hermann ▁von ▁Hel m hol tz ▁and ▁E wald ▁Her ing ▁worked ▁out ▁the ▁exact ▁shape ▁of ▁the ▁hor opter ▁almost ▁at ▁the ▁same ▁time . ▁Their ▁descri ptions ▁identified ▁two ▁components ▁for ▁the ▁hor opter ▁for ▁symmet rical ▁fix ation ▁closer ▁than ▁infinity . ▁The ▁first ▁is ▁in ▁the ▁plane ▁which ▁contains ▁the ▁fix ation ▁point ▁( where ver ▁it ▁is ) ▁and ▁the ▁two ▁nod al ▁points ▁of ▁the ▁eye . ▁ ▁The ▁geometric ▁loc us ▁of ▁hor opter ic ▁points ▁in ▁this ▁plane ▁takes ▁the ▁form ▁of ▁the ▁arc ▁of ▁a ▁circle ▁( the ▁Vi eth - M üller ▁circle ) ▁going ▁from ▁one ▁nod al ▁point ▁to ▁the ▁other ▁in ▁space , ▁passing ▁through ▁the ▁fix ation ▁point . ▁ ▁The ▁second ▁component ▁is ▁a ▁line ▁( the ▁Pr év ost – B ur ck hardt ▁line ) ▁which ▁is ▁per pend icular ▁to ▁this ▁arc ▁in ▁the ▁median ▁plane , ▁cutting ▁it ▁at ▁the ▁point ▁mid way ▁between ▁the ▁two ▁eyes ▁( which ▁may ,