Differential Diagnosis for the Patient's Eye Findings

The patient's presentation of painless decrease in visual acuity in the right eye, alongside the given medical history and current health status, suggests several potential diagnoses. These can be categorized as follows:

• Single Most Likely Diagnosis

  • Candida Endophthalmitis: This is a likely diagnosis given the patient's immunocompromised state due to chronic illness and total parenteral nutrition (TPN), which increases the risk of fungal infections. Candida endophthalmitis is a known complication in patients with indwelling catheters for TPN, especially when they have a history of bowel surgery and are at risk for bacterial translocation and subsequent fungemia.

• Other Likely Diagnoses

  • Cytomegalovirus Retinitis: Although more commonly associated with HIV/AIDS, CMV retinitis can occur in other immunocompromised patients. The patient's condition, requiring chronic TPN and having undergone multiple surgeries, may compromise his immune system, making him susceptible to opportunistic infections like CMV.
  • Hyperglycemia: High blood glucose levels can cause changes in the lens of the eye, leading to blurred vision. However, this typically would not cause a unilateral decrease in visual acuity as described.
  • Retinal Vein Occlusion: This condition can cause sudden painless loss of vision and is associated with various risk factors, including hypercoagulability, which might be present in a patient with chronic illness and possible dehydration or coagulopathy.

• Do Not Miss Diagnoses

  • Retinal Detachment: Although less likely given the lack of symptoms such as flashes or floaters, retinal detachment is an emergency that requires prompt treatment to preserve vision. It can occur in anyone but might be more likely in patients with significant systemic disease or those on chronic steroid therapy.
  • Endogenous Endophthalmitis due to Bacterial Causes: While Candida is a common cause of endophthalmitis in this context, bacterial endophthalmitis, especially due to gut flora, is a possibility given the patient's history of bowel resections and could be life-threatening or vision-threatening if not promptly treated.

• Rare Diagnoses

  • Toxoplasmosis: Reactivation of toxoplasmosis can occur in immunocompromised patients, leading to retinochoroiditis. However, this would be less likely without a history of exposure or previous infection.
  • Other Opportunistic Infections: Depending on the patient's specific immune status and exposure history, other opportunistic infections could potentially cause similar symptoms, though they would be less common than the aforementioned diagnoses.