▁shape ▁of ▁the ▁cor nea ▁and ▁ref ract ive ▁error . ▁If ▁the ▁shape ▁of ▁the ▁cor nea ▁is ▁fairly ▁regular ▁and ▁ref ract ive ▁error ▁is ▁similar ▁to ▁that ▁of ▁the ▁other ▁eye , ▁it ▁is ▁usually ▁possible ▁to ▁fix ▁any ▁error ▁with ▁glass es ; ▁if ▁not , ▁a ▁hard ▁l ens ▁may ▁be ▁necessary ▁to ▁correct ▁vision . ▁ ▁Cor ne al ▁gra ft ▁re jection ▁ ▁One ▁of ▁the ▁largest ▁causes ▁for ▁issue ▁in ▁pen etr ating ▁ker at op last y ▁is ▁the ▁natural ▁imm une ▁re jection ▁of ▁a ▁trans pl anted ▁cor ne al ▁button ▁which ▁can ▁cause ▁revers ible ▁or ▁irre vers ible ▁damage ▁to ▁the ▁gra ft ed ▁cor nea . ▁The ▁types ▁cor ne al ▁re jection ▁include ▁ep ith el ial ▁re jection , ▁chron ic ▁re jection , ▁hyper ac ute ▁re jection ▁and ▁end oth el ial ▁re jection ▁and ▁these ▁can ▁occur ▁individually , ▁or ▁in ▁some ▁cases ▁in ▁conj unction . ▁ ▁There ▁are ▁however , ▁two ▁main ▁prevent ative ▁methods ▁to ▁reduce ▁the ▁possibility ▁of ▁imm une ▁re jection ; ▁prevent ion ▁and ▁management . ▁Pre vention ▁involves ▁increasing ▁compatibility ▁of ▁the ▁don or ▁t issue ▁with ▁that ▁of ▁the ▁patient ▁and ▁suppress ing ▁host ▁imm une ▁response . ▁These ▁anal ys es ▁of ▁don or ▁cor ne as ▁are ▁done ▁during ▁a ▁screen ing ▁phase ▁soon ▁after ▁receiving ▁the ▁don ation . ▁The ▁management ▁aspect ▁mainly ▁involves ▁early ▁detection ▁and ▁ther apy ▁with ▁cort ic ost