Herpes simplex virus PCR in 2230 explanted corneal buttons

To determine herpes simplex virus (HSV) DNA prevalence and mean cycle threshold of polymerase chain reaction (PCR) in corneal tissue of patients with penetrating keratoplasty (PKP), with (HSK+) and without (HSK-) previous clinical herpetic keratitis history.

Retrospective review of recipient corneal buttons which were explanted through PKP between March 2010 and September 2018 at the Department of Ophthalmology, Saarland University Medical Center in Homburg/Saar, Germany. Corneal tissue samples were analysed by real-time PCR for the presence of HSV DNA. For each subject, clinical data, including patients' demographics and clinical diagnoses, were collected.

In total, 2230 corneal samples (age at the time of the surgery 57.3 ± 19.2 years) of 1860 patients were analysed. HSV PCR was positive in 137 (6.1%) corneal samples, with a 30.57 ± 6.01 (range 14-39) mean cycle threshold (Ct) value. Two hundred ninety-eight (13.4%) corneas of 266 patients were clinically HSK+, and 1932 (86.6%) corneas of 1600 patients were clinically HSK-. HSV DNA was detected significantly more frequently (p < 0.0001) in HSK+ corneal samples (108 corneal samples; 36.2%), than in HSK- corneal samples (29 corneal samples; 1.5%). Ct value was significantly lower in HSK+ than in HSK- corneal samples (29.8 ± 5.8 versus 32.6 ± 5.9; p = 0.008).

Our data demonstrate that a positive clinical history of HSK is related to HSV PCR positivity in about every 2.8th patient. In addition, about every 66th explanted corneal tissue is HSV PCR-positive despite the lack of clinical suspicion. These patients may need additional local/systemic antiviral treatment to avoid newly acquired HSK following penetrating keratoplasty.