What finding would suggest a diagnosis of iritis over conjunctivitis?

A disturbance in visual acuity is a significant finding that suggests a diagnosis of iritis rather than conjunctivitis. Iritis involves inflammation of the uveal tract, particularly the iris, and can lead to complications that affect vision, such as swelling and changes in intraocular pressure. Patients with iritis often experience blurred vision or diminished visual acuity, which is not commonly associated with conjunctivitis, where vision is typically unaffected.

In contrast, other symptoms like itching sensations and the presence of pus or discharge are more characteristic of conjunctivitis. Itching is often linked to allergic conjunctivitis, while discharge is commonly seen in bacterial forms. Additionally, pain or discomfort that is relieved with blinking is more indicative of conditions affecting the surface of the eye, such as dry eye or conjunctivitis, rather than iritis, which tends to cause deep, aching pain. Therefore, visual acuity disturbance stands out as a critical distinguishing factor for iritis.