Corneal biopsy as a primary diagnostic tool in microbial keratitis patients on poly-antimicrobials

To evaluate the role of corneal biopsy in nonhealing keratitis patients on multiple antimicrobials.

In a randomized, prospective, interventional study conducted at a tertiary eye center in India, 44 patients with infectious keratitis were recruited from February 2022 to October 2023. The cases that were on ≥2 topical antimicrobial drugs belonging to 2 different classes for ≥1 week with no signs of healing and corneal ulcer size of ≥4 mm were included. They were randomized into two groups: the corneal scraping group and the corneal biopsy group. The primary outcome measure was culture positivity rate, while the secondary outcome measures were smear positivity rate and complication rates in both groups.

The culture positivity rate of the corneal scraping group was 59.09% and the corneal biopsy group was 77.27% in cases of bacterial keratitis (P = 0.32). However, in cases of fungal keratitis, the culture positivity rate of the biopsy group was better than the scraping group (P = 0.012). The sensitivity and specificity of the Gram stain of the corneal scraping sample were found to be 55.56% and 92.31%, respectively. The sensitivity and specificity of the potassium hydroxide stain of the corneal scraping sample were found to be 50% and 94.4%, respectively. The sensitivity and specificity of histopathological samples obtained from biopsy to detect fungal elements were 66.6% and 90%, respectively. No complications were noted in both the groups during the procedure.

In nonhealing keratitis with suspected fungal cause, corneal biopsy may be used as a primary diagnostic modality in a referral center.