Aims To analyse high-order aberrations (HOA), modulation transfer function (MTF) and Strehl ratio in patients with a history of herpes simplex keratitis (HSK) and apparently normal vision.

Methods Fifteen patients with a history of recurrent unilateral HSK and normal Snellen visual acuity (0 logMAR) were enrolled. Eyes with HSK (HSK group) were statistically compared with normal fellow eyes (Control group). HOA, MTF and Strehl ratio were measured using the OPD-SCAN II (Nidek Co, Gamagori, Japan) aberrometer. Measures were performed at least 3 months after the last episode of herpes. Statistical significance was indicated by p<0.05.

Results Despite apparently normal vision in both eyes (as assessed by routine visual acuity charts), significantly higher total HOA, trefoil and tetrafoil were present in the HSK group compared with the Control group. The MTF and strehl ratio were lower in the HSK group compared with the Control group. In the HSK group, eyes with corneal opacities tended to present with greater optical aberrations than eyes with a clear cornea.

Conclusions Using patients as their own controls, the outcomes of this study indicate that eyes with recurrent HSK with no apparent decrease in visual acuity (0 logMAR) have significantly greater optical aberrations than eyes with no past history of herpetic disease. This outcome may explain some visual complaints of HSK patients, such as a decrease in contrast quality or reduced colour perception, compared with the unaffected contralateral eye despite apparently normal vision in both eyes.