Which of the following conditions is not hereditary?

Conjunctivitis, commonly known as pink eye, is primarily caused by infections, allergies, or irritants rather than hereditary factors. While certain individuals may have a genetic predisposition to allergies that could lead to allergic conjunctivitis, the condition itself is not inherited in the same manner as genetically influenced diseases.

In contrast, asthenopia (eye strain), keratoconus, and sudden vision loss can relate more directly to hereditary factors. Asthenopia may arise from various causes but is not inherently a hereditary condition. Keratoconus is a progressive eye disorder that has been linked to genetic factors, and certain types of sudden vision loss can also be associated with hereditary conditions like retinal detachment or other genetic eye diseases. Thus, identifying conjunctivitis as a non-hereditary condition underscores the importance of differentiating between conditions based on their underlying causes, especially when considering their management and treatment options in the field of ophthalmology.