In vivo confocal microscopy characteristics of equine epithelial and subepithelial nonulcerative keratomycosis

Abstract

With in vivo confocal microscopy, both epithelial and subepithelial keratomycosis appear as unique clinical entities. Equine epithelial keratomycosis is a potential precursor to subepithelial keratomycosis.

Fungal keratitis in a mare: case report in Costa Rica

“…In addition, in a study using in vivo confocal microscopy, Ledbetter et al (2018) were able to evidence the presence of fungal organisms even when the epithelium is still present, which suggests a similar tropism for the corneal epithelial basement membrane.…”

“…Several fungal genera are associated with keratomycosis, including Aspergillus, Fusarium, Candida, Curvularia, Penicillium, Cylindrocarpon, and Mucor (Galán et al 2009;Utter et al 2010;Galera & Brooks 2012;Wada et al 2013;Samanta 2015;Sherman et al 2017;Ledbetter et al 2018), the first two being the most frequently reported and with the worst prognosis (Galán et al 2009;Utter et al 2010;Cafarchia et al 2013;Sherman et al 2017;Roberts et al 2020). Since these genera are also found in healthy eyes (Khosravi et al 2014), a fungal culture must be conducted with histopathology and/or cytology to verify whether the tissue has been compromised with hyphae or yeast.…”

“…It has been reported and assumed that fungal organisms have a tropism for the glycosaminoglycans in the equine deep corneal stroma close to Descemet's membrane (Utter 2015;Ledbetter et al 2018).…”

“…When a superficial epithelial lesion exists, the release of proteolytic enzymes from fungi, leukocytes, and keratocytes results in the progression of keratomycosis to deeper layers of the cornea, threatening vision (Wada et al 2013;Ledbetter et al 2018). The use of topical antimicrobials and topical corticosteroids can impair the local immune defenses, and opportunistic pathogens such as fungi can proliferate easily.…”

“…Some of the diagnostic tests used to determine a fungal etiology include culture, cytology, histopathology, polymerase chain reaction, and in vivo laser scanning confocal microscopy (Galera & Brooks 2012;Ledbetter et al 2018), all of which, except for the last one, are currently available in Costa Rica at affordable prices. However, depending on the lesion's progression and the availability of the specimen collection, taking the samples and choosing the tests could be a challenge (Ledbetter et al 2018). For example, in a five-year retrospective study using medical records of twenty-one horses with subepithelial keratomycosis, only ten cases of mycotic etiology were cytologically confirmed and only four cases were positive for fungal isolates: Candida spp.…”