Epithelial abrasion precipitates stromal ulceration in the vitamin A--deficient rat cornea.

ABSTRACT

Although the role of vitamin A deficiency in the development of xerophthalmia is well established, there is still some question as to whether the deficiency alone is sufficient cause for the development of keratomalacia. This article describes the clinical, histologic, and microbiologic changes occurring in eyes of vitamin A-deficient rats when keratomalacia-like stromal ulceration is induced by epithelial injury alone. The corneal epithelia of 21 severely vitamin A-deficient rats and 11 pair-fed controls were totally removed either by scraping or by n-heptanol. At 96 hr after epithelial removal, 93% of the deficient animals showed extensive epithelial defects and stromal ulceration. Histologically, an intense acute inflammatory response and abundant bacterial forms were consistently evident. Staphylococcus aureus and Streptococcus fecalis were the most frequent pathogens cultured from these ulcerating eyes. In contrast, the control corneas showed essentially complete re-epithelialization, with no ulceration, minimal inflammatory reaction, and an absence of morphologically demonstrable bacteria. Bacterial cultures from the control eyes showed abundant Pasteurella, with pathogens also present. These observations suggest that abnormal epithelial recovery, acute inflammation, and bacterial infection may be important factors for the development of keratomalacia-like corneal ulceration in experimental vitamin A deficiency.