A comparison between nomogram vs. trial fitting of rigid gas permeable contact lenses

To determine the differences between prescribing a trial fitted vs. nomogram (System 10) selected rigid gas permeable contact lens, 42 subjects were fit with one lens design on one eye and the other lens design on the opposite eye. Subjective responses for comfort and vision, objective signs of central corneal clouding, conjunctival injection, post keratometry readings, 3-9 staining, over-refraction, post refraction and lens position were ranked and assigned to success levels for each eye. Subjects were evaluated at 1 week, 1 month, and 3 months. The first fit success rates were 92 percent for the trial fit and 86 percent for the nomogram fit. The trial fit lens attained significantly better outcomes in individual categories of comfort and over-refraction. It was noted that the lens diameters differed significantly and a large percentage of both types of lenses benefited from a slight blend and edge modification. Although trial fitting remains the method of highest success, nomogram fitting (using System 10) appears consistent enough to consider it an option for certain practice situations.