▁to ▁ 8 5 ▁percent . ▁ ▁Path ogen esis ▁CE A ▁is ▁caused ▁by ▁impro per ▁development ▁of ▁the ▁eye . ▁ ▁Fail ure ▁of ▁the ▁cells ▁of ▁the ▁posterior ▁portion ▁of ▁the ▁opt ic ▁ves icles ▁to ▁express ▁growth ▁h orm one ▁affect s ▁the ▁different iation ▁of ▁other ▁cells ▁of ▁the ▁eye . ▁ ▁The ▁ch or oid , ▁especially ▁later al ▁to ▁the ▁opt ic ▁disc , ▁is ▁hyp op last ic ▁( under develop ed ). ▁ ▁A ▁col ob oma , ▁or ▁hole , ▁may ▁form ▁in ▁or ▁near ▁the ▁opt ic ▁disc ▁due ▁to ▁a ▁failed ▁closure ▁of ▁emb ry onic ▁t issue . ▁ ▁The ▁degree ▁of ▁these ▁ab normal ities ▁var ies ▁between ▁individual ▁dogs , ▁and ▁even ▁between ▁the ▁same ▁dog ' s ▁eyes . ▁ ▁CE A ▁is ▁inherited ▁as ▁an ▁aut os om al ▁re cess ive ▁trait ▁that ▁has ▁a ▁pen et rance ▁reaching ▁ 1 0 0 ▁percent , ▁and ▁has ▁been ▁local ized ▁to ▁can ine ▁chrom os ome ▁ 3 7 . ▁ ▁Sign s ▁The ▁most ▁common ▁sign ▁of ▁CE A ▁is ▁the ▁presence ▁of ▁an ▁area ▁of ▁und e velop ed ▁ch or oid ▁( app ear ing ▁as ▁a ▁pale ▁spot ) ▁later al ▁to ▁the ▁opt ic ▁disc . ▁ ▁The ▁ch or oid ▁is ▁a ▁collection ▁of ▁blood ▁vessels ▁supp lying ▁the ▁ret ina . ▁ ▁CE A ▁can ▁also ▁cause ▁ret inal ▁or ▁s cler al ▁col ob oma , ▁col