Treatment of hyperopia: a new ablation profile to reduce corneal eccentricity

Hyperopic treatment normally increases corneal eccentricity (the measure of corneal asphericity). Information derived from treating corneal white scars occurring after hyperopic ablations suggests that reducing corneal eccentricity through central corneal flattening followed by smoothing eliminates scarring and prevents its recurrence.

We treated two groups of patients; Group 1 included 18 eyes of 18 patients with whitish corneal scar due either to photorefractive keratectomy (PRK) (n = 16, 88.9%) or laser in situ keratomileusis (LASIK) (n = 2, 11.1%). Mean preoperative spherical equivalent refraction was +1.20 +/- 2.30 D, and mean corneal eccentricity was +1.2 +/- 0.8. We performed phototherapeutic keratectomy (PTK) to achieve central corneal flattening and decrease corneal eccentricity, coupled with smoothing, using the Nidek EC-5000 excimer laser. Group 2 included 27 eyes of 27 consecutive patients with mean preoperative spherical equivalent refraction of +2.40 +/- 1.30 D; these patients had laser epithelial keratomileusus (LASEK) with the Nidek EC-5000 excimer laser. A new Nidek aspheric ablation profile with a wider optical zone (6.7 mm) and transition zone (9.5 to 10.00 mm) was applied.

In Group 1 eyes, the apical scar disappeared in all eyes. Postoperative spherical equivalent refraction was +1.8 +/- 1.02 D and mean postoperative eccentricity was +0.9. In Group 2 eyes after 9 months of follow-up, mean postoperative spherical equivalent refraction was -0.30 +/- 0.30 D, with no loss of lines of BSCVA. Low corneal eccentricity values were maintained, which created a gradual change in the rate of curvature.

The new Nidek profile for hyperopia treatment allowed successful refractive correction and maintained low eccentricity values that approached those of a normal cornea.