Inflammation - Human tissue’s natural reaction to trauma; often accompanied by discomfort, redness and swelling            

Intacs - Intrastromal corneal rings; a non-laser refractive surgical option for low degrees of nearsightedness

Implant, Aphakic - A small artificial lens placed into the eye to restore the eye's focus after cataract surgery to remove a cloudy natural lens

Implant, Phakic - A small artificial lens placed into the eye along with the eye's natural lens to reduce significant amounts of refractive error such as myopia

Iris - The colored portion of the eye behind the cornea
 

Intraocular pressure - The pressure the fluid contained within the eye exerts on the globe.

Irregular astigmatism - A refractive error caused by an irregular shape of the cornea in which the curve on one side of the meridian or axis is not symmetrical with the curve on the other side.