Outside of the eye is in direct contact with the environment, it is susceptible to infections and injuries. There are also a number of hereditary diseases that can impact the outer eye. The major signs of external eye disease are redness that does not improve with treatment and poor vision not explained by retina problems. One common external eye condition is conjunctivitis (usually called “pink eye”), an infection marked by red, itchy eyes and tearing. Pink eye can be caused by cold viruses, allergic reactions or bacteria. Other common conditions include inflammation of the sclera (the tough outer layer of the eye) and inflammation of the cornea caused by a skin disease known as rosacea. About one-fifth of all patients with keratoconus will require a corneal transplant-for information. External incisions lead to scarring, so making external eyelid incisions or punctures is inadvisable, unless the hordeolum already is pointing externally. A large abscess may have multiple pockets and require multiple stabs. Internal incisions should be made vertically to minimize the area of cornea swept by a scar during blinking; external incisions should be made horizontally for optimal cosmesis. When draining a lesion that points both externally and internally, make the incision internally and as far as possible from the site of external pointing. Combined overlying internal and external drainage increases the risk of later fistulae through the lid.