Microvascular complications in orthokeratology (Ortho-K): A real-time study on the microvasculature of the bulbar conjunctiva in Ortho-K treatment.

Abstract

Orthokeratology (Ortho-K) is an over-night hard contact lens therapy, which physically reshapes the corneal curvature in order to stabilize or temporally eliminate myopia in patients. We hypothesize that the prolonged physical contact and mechanical pressure induced by the Ortho-K lenses may create lasting inadvertent effects and damages (microangiopathy), and may bring about unwanted changes in the microvasculature of the bulbar conjunctiva. Computer-assisted intravital microscopy (CAIM) was used to view, document (via videotaping) and objectively quantify (via computer-assisted image analysis) the real-time dynamic and morphometric characteristics of the conjunctival microcirculation in long-term (at least over one year) Ortho-K patients (n = 11) and matched non-user control subjects (n = 8). Ortho-K patients were instructed to wear their lenses overnight following standard protocol. During the study, the conjunctival microcirculation of the left eye of all Ortho-K lens users was viewed, frequently re-focused and videotaped, without and with the lens in place, as outlined in Methods. The matched control subjects (non-lens wearing) were videotaped and studied in like manner. The dynamic and morphometric characteristics of each user and control subject were analyzed, quantified and summated as a severity index (SI) collectively for comparison. SI of Ortho-K lens users (4.18±1.08) differed significantly from SI of control subjects (1.75±1.39, p≤0.05). In addition, changes in the conjunctival microcirculation (e.g., flow velocity, vessel diameter, shape change, etc) were viewed and videotaped immediately after the myopic patients put on the Ortho-K lenses. Eight of the 11 Ortho-K lens users displayed significant percentage changes (p≤0.05) in flow velocity and 10 of 11 displayed significant percentage changes (p≤0.05) in vessel diameter, without and with the Ortho-K lenses. The results clearly indicated that significant microvascular changes via tissue remodeling occurred, and were caused directly by the physical presence of the Ortho-K lenses.