Corneal refractive therapy, uncorrected visual acuity, and "E" values: personal experiences

The author describes selected aspects of his clinical experience in fitting and prescribing orthokeratology lenses to temporarily reduce or eliminate myopia. The precision of videokeratography (VK) data in determining corneal sagittal depth is examined. Treatment outcomes are analyzed after overnight wear of two proprietary corneal remodeling systems. Two case reports describing off-label treatments are presented.

A retrospective analysis was performed of the baseline VK data of 25 consecutive candidates (50 eyes) for corneal remodeling, captured with a Keratron topographer. Sixteen consecutive patients fitted with Paragon corneal refractive therapy (CRT) lenses were compared against an age- and sex-matched group of patients fitted with the Mountford BE lens for 1-day, 1-week, and 1-month uncorrected visual acuity.

The mean +/- SD of the apical radius ("Ro") and corneal eccentricity ("E") values was 0.03 +/- 0.01 mm and 0.03 +/- 0.01 degrees , respectively, indicating a spread of 24 microm in the sagittal elevation data. Mean target myopia and 1-day uncorrected visual acuity were -1.71 +/- 0.71 diopters and 20/20 +/- 20/0.86, respectively, for the Paragon CRT lenses and -2.30 +/- 0.89 diopters and 20/31 +/- 20/20.6, respectively, for the Mountford BE lenses.

The Paragon CRT and the Mountford BE lenses delivered impressive reductions in uncorrected visual acuity after the first night of overnight wear. The Paragon CRT lens had the advantage of not requiring a previous overnight lens trial before commencing the treatment program.