A 27-year-old Japanese man with a history of keratoconus (KC) and atopic dermatitis presented with sudden onset of decreased vision in his left eye. Best corrected visual acuity was 20/200 in the left eye. Slit-lamp examination and cross-sectional imaging with anterior segment optical coherence tomography revealed marked corneal stromal and epithelial edema with corneal protrusion in his left eye (Figure A). Thus, he was diagnosed with acute corneal hydrops. Pressure patching with an ophthalmic ointment improved the corneal edema gradually.