To evaluate in vivo confocal microscopy (IVCM) findings of ocular surface squamous neoplasia (OSSN) during treatment with topical interferon alfa-2b (IFN alfa-2b).

In this prospective interventional case series, 20 eyes from 20 patients with OSSN were treated with topical IFN alfa-2b 3 million IU/mL four times a day. Treatment was continued for 2 or 3 months after clinical resolution. IVCM was done at baseline, on monthly basis and at the end of treatment. Confocal images were evaluated in conjunction with clinical findings during treatment. Limbal dendritic cells (DCs) density within the involved areas was calculated manually in confocal images.

Topical therapy resulted in clinical resolution of neoplasia in 80% of eyes. Main features of OSSN on IVCM were hyper-reflectivity of epithelium, demarcation line between neoplastic and normal epithelium, and pleomorphic cells. These findings became less prominent in response to IFN alfa-2b therapy. However, some degree of residual epithelial hyper-reflectivity could be detected in 9 (56.2%) subjects who responded to therapy at time of treatment cessation. Limbal DCs density within involved areas was significantly increased at 1 follow up compared to baseline in both responders (P<0.0001) and non-responders (P< 0.036). There was a trend toward higher limbal DCs density in responders to topical IFN alfa-2b than non-responders (208.6±53.5 vs. 153.1±48.2 cell/mm2, respectively; P=0.07) at 1 month follow up.

IVCM is proposed as an adjunctive tool for monitoring OSSN during topical treatment. Limbal DCs density increases with topical IFN therapy, which may contribute to complete clinical response. IVCM could not replace the clinical examinations for cessation of topical treatment in OSSN.