Corneal steepening induced by apical clearance lenses

Apical clearance contact lenses induced corneal steepening after short-term wear, a clinical study found. The study authors said that although corneal molding has been implicated as the primary factor causing this shape change, they found that corneal edema and tear film pressures played roles as well.

Helen Swarbrick, PhD, FAAO, and colleagues studied 10 young adults who wore apical clearance lenses fitted about 0.3 mm steeper than the flattest keratometric reading for 4 hours. The PMMA lens was worn in one eye and a Boston XO lens (Bausch & Lomb) in the other. The lenses were nonfenestrated in a first trial, and a single midperipheral fenestration was added for a second trial.

Significant central corneal edema was demonstrated in the PMMA lens eyes only. Fenestration did not reduce the edema response. The researchers found “significant corneal steepening over a 5- to 6-mm central zone” that was more pronounced in the PMMA-lens-wearing eye and was modified by lens fenestration.

The study is published in Optometry and Vision Science.