▁imag ing ▁by ▁digital ▁h olog raph y ▁can ▁measure ▁blood ▁flow ▁in ▁the ▁ret ina ▁and ▁ch or oid , ▁whose ▁Do pp ler ▁responses ▁exhib it ▁a ▁pul se - sh aped ▁profile ▁with ▁time ▁ ▁. ▁This ▁technique ▁enables ▁non ▁invas ive ▁functional ▁micro ang i ography ▁by ▁high - contr ast ▁measurement ▁of ▁Do pp ler ▁responses ▁from ▁end ol um inal ▁blood ▁flow ▁profiles ▁in ▁vessels ▁in ▁the ▁posterior ▁segment ▁of ▁the ▁eye . ▁D iffer ences ▁in ▁blood ▁pressure ▁drive ▁the ▁flow ▁of ▁blood ▁throughout ▁the ▁circul ation . ▁The ▁rate ▁of ▁mean ▁blood ▁flow ▁depends ▁on ▁both ▁blood ▁pressure ▁and ▁the ▁hem od ynamic ▁resistance ▁to ▁flow ▁presented ▁by ▁the ▁blood ▁vessels . ▁ ▁G loss ary ▁ ▁AN H Ac ute ▁Norm ov ole mic ▁Hem od il ution ▁ ▁AN H u Number ▁of ▁Units ▁During ▁AN H ▁ ▁B L H Max imum ▁Blood ▁L oss ▁Possible ▁When ▁AN H ▁Is ▁U sed ▁Before ▁Hom olog ous ▁Blood ▁Trans f usion ▁Is ▁Ne eded ▁B LI In crement al ▁Blood ▁L oss ▁Possible ▁with ▁AN H .( BL H ▁– ▁B L s ) ▁ ▁B L s Max imum ▁blood ▁loss ▁without ▁AN H ▁before ▁hom olog ous ▁blood ▁trans f usion ▁is ▁required ▁ ▁E B VE st im ated ▁Blood ▁Volume ( 7 0   m L / kg ) ▁ ▁H ct Ha emat oc rit ▁Always ▁Ex pressed ▁Here ▁As ▁A ▁Fra ction ▁ ▁Hi Initial ▁Ha emat