Pain and photophobia come from irritation of the corneal surface and its nerves. An infectious ulcer provokes a strong inflammatory response as invading organisms and their toxins trigger abundant neutrophils and inflammatory mediators, deeply irritating corneal nerves and creating a lot of pain. The exposed and damaged epithelial surface, along with ongoing inflammation, makes light uncomfortable, so photophobia is prominent. In contrast, sterile inflammatory ulcers can cause discomfort, but they typically provoke less intense pain and photophobia because there isn’t an active infectious process driving nerve irritation. Therefore, the infectious ulcer is the type most associated with moderate to severe pain and photophobia.

When regression fails to occur after the critical period, the vessels that formed during neovascularization don’t completely disappear; they leave behind ghost vessels. These are non-perfused, linear remnants—essentially empty sleeves of former vessels—that appear as pale, thread-like lines rather than a branching, active network. The key idea is that the vascular pattern becomes a nonfunctional trace of what once grew, not new branching or occlusion. This fits because the other possibilities imply active growth or blockage: branching vessels at the limbal arcades would indicate new angiogenesis; vascular occlusion would mean blocked flow within vessels; epithelial edema is a surface epithelial issue, not a vascular pattern. Ghost vessels precisely capture the scenario of incomplete regression, leaving behind nonperfunded, nonbranching vessel remnants.

Tight lens syndrome happens when a contact lens fits so tightly that it doesn’t move with the eye. Movement is key for refreshing the tear layer under the lens and bringing in oxygen to the cornea. When the lens barely moves, tear exchange under the lens is reduced, which stresses the ocular surface and vessels. This mechanical compression of the conjunctiva can cause blanching (a pale appearance) and congestion (redness) from altered blood flow under the lens. At the same time, the lack of movement and the tight fit create friction between the conjunctiva and the lens as the eye moves, leading to conjunctival drag. So the combination of no movement, reduced tear exchange, and the resulting vascular changes and friction best describes tight lens syndrome.

Short-term metabolic responses of the corneal epithelium to contact lens wear are mainly driven by tear-film disruption and reduced oxygen, leading to surface damage and swelling. Erosions are breaches of the epithelial surface from dryness or mechanical irritation, reflecting immediate injury. Edema is fluid buildup in the epithelial layers due to altered tear exchange and hypoxic stress, another direct short-term metabolic reaction. Warpage represents a temporary mechanical distortion of the corneal shape caused by the lens pressing on the cornea, a structural change rather than a metabolic one. Microcysts, however, are tiny cystic spaces within epithelial cells that arise from longer-term metabolic disturbances and sustained edema, so they do not fit the pattern of a short-term epithelial metabolic effect.