<prompt> A patient with ptosis, upper 4mm of cornea is covered by upper eyelid. Grade of ptosis is-MildModerateSevereProfound  <response>: In unilateral cases of ptosis, difference between the veical height of palpebral fissures of the two sides indicates the degree of ptosis. In bilateral cases it can be determined by measuring the amount of cornea covered by the upper eyelid and then subtracting 2mm. Depending upon its amount the ptosis is graded as:- Mild : 2mm Moderate : 3mm Severe : 4mm In this question, 4mm of cornea is covered by upper eyelid. Subtracting 2mm from this means there is 2mm of ptosis, i.e. mild grade. Ref: Khurana 7the p.395 