To examine histopathological findings of filamentary keratitis due to corneal occlusion.

We analyzed filamentary keratitis in 11 eyes with corneal occlusion due to blepharospasm, ptosis and paralytic strabismus, 11 eyes with keratoconjunctivitis sicca, and 13 eyes with both corneal occlusion and keratoconjunctivitis sicca. The following protocols were used for filament analyses: slit lamp examination for counting filament numbers, impression cytology for grading mucin content, and histopathology (hematoxylin and eosin staining) and immunohistochemistry (with AE1/AE3, MUC1, 5AC, 16) for histological analysis.

Slit lamp biomicrosopy showed a significantly smaller number of filaments in the corneal occlusion group (11 eyes, 2.7 ± 1.4) than the keratoconjunctivitis sicca group (11 eyes, 5.1 ± 2.2, p = 0.009). In impression cytology, the standard photograph grade of mucin content was significantly higher in the corneal occlusion group (2.7 ± 0.9) than the keratoconjunctivitis sicca group (1.9 ± 0.8, p = 0.034). On pathological exam, filaments showed a central filament with peripheral mucin. The central filaments were composed of core and cortex, and the core contained multiple deformed nuclei. However, the cortex was not stained by AE1/AE3, MUC1, 5AC, 16.

Filamentary keratitis due to corneal occlusion showed a smaller number of filaments and higher mucin content than filamentary keratitis induced by keratoconjunctivitis sicca and should be considered during treatment.