Healing indicators after pterygium excision by optical coherence tomography

Abstract

Purpose: To establish the sequence of tomographic changes in the tissue recovery process after pterygium excision and to propose healing indicators.

Methods: Optical coherence tomography (OCT) images were taken at 1 week, 1, 3 and 6 months after lesion excision in 73 eyes of 73 patients (33 male, 40 female; mean age 50, S.D. 5.0, range 40-70 years) with primary nasal pterygium. Biomicroscopy was performed at each visit and at 12 months, to diagnose clinical healing or lesion recurrence. The presence of well demarcated corneal epithelium, conjunctival epithelium, limbal demarcation area, and graft thickening were analysed. Comparisons between tomographic data of both clinical situations were made at each time point using contingency tables.

Results: Eleven eyes displayed lesion recurrence (R group) and 62 eyes showed no recurrence (NR group). Normal anatomical structures, corneal and conjunctival epithelium and limbal demarcation area, were identified by OCT images in a higher percentage of NR cases over time, compared to the R group where most of the cases presented without these markers of tissue recovery. In contrast, the variable graft thickening, which analysed a pathological event, revealed similar results in both groups (p > 0.05; Fisher's exact statistic), with a clear decrease of cases which showed graft thickening over time. Differences between groups started at 1 month, when no eye had yet presented clinical recurrence, with greater identification of corneal epithelium in the NR group (p = 0.04; Fisher's exact statistic). At 3 months, corneal and conjunctival epithelium identification tended to be more frequent in the NR than in the R group (in both cases, p = 0.0001; Fisher's exact statistic). Finally, at 6 months these different patterns consolidated, with a significantly higher number of limbal demarcation areas being identified in the NR group (p = 0.001; Fisher's exact statistic). In fact, this landmark of a normally structured limbus was never found in the R group.

Conclusions: The sequence of tissue restoration, according to OCT images, seems to start in the cornea and end in the limbal area, similar to the process of pterygium injury in reverse. Although the visualisation of corneal epithelium could be an early indicator of successful surgery, identification of the limbal demarcation area, as a normal limbal pattern in OCT images, seems to be a better positive predictive value in diagnosing healing.

Keywords: autograft; healing process; optical coherence tomography; pterygium; recurrence.