Chemical Conjunctivitis or Keratitis: This is the most likely diagnosis when feces get into the eye. Feces contain bacteria and other harmful substances that can cause an inflammatory reaction in the conjunctiva or cornea, leading to symptoms like redness, pain, and discharge.

Conjunctivitis: Bacterial conjunctivitis is a common infection that can occur when bacteria from feces enter the eye. Symptoms include redness, itching, and discharge.
Corneal Ulcer: A corneal ulcer can develop if the bacteria in the feces infect the cornea, potentially leading to serious complications if not treated promptly.
Endophthalmitis: Although less common, endophthalmitis, an infection of the inner eye, is a possible diagnosis if bacteria from the feces penetrate deeper into the eye.

Gonococcal Conjunctivitis: In cases where the feces are contaminated with Neisseria gonorrhoeae (from anal intercourse), gonococcal conjunctivitis is a critical diagnosis not to miss due to its potential for severe consequences, including vision loss if not treated promptly and effectively.
Herpes Simplex Keratitis: If the individual has a herpes simplex infection, introducing fecal matter into the eye could potentially reactivate the virus, leading to herpetic keratitis, which requires specific antiviral treatment.

Toxocariasis: While rare, toxocariasis (an infection caused by the Toxocara parasite found in cat and dog feces) could potentially affect the eye if fecal matter containing the parasite's eggs enters the eye, leading to ocular larva migrans.
Toxoplasmosis: Reactivation of toxoplasmosis in an immunocompromised individual could occur if they introduce fecal matter contaminated with Toxoplasma gondii into their eye, though this would be extremely rare and more commonly associated with direct contact with cat feces.