Mastering corneal inlays

Corneal inlay and centration

The KAMRA intracorneal inlay (AcuFocus) is a 5 micron thick microperforated inlay that functions on the principles of small-aperture optics. It measures 3.8 mm in diameter and can be combined with excimer ablation to simultaneously address presbyopia and ametropia. As with photoablative surgery, correct centration of the inlay is a factor in both distance and near visual acuity, as well as overall quality of vision. Decentred ablations may cause side effects such as glare, ghosting, halos, loss of contrast, monocular diplopia and irregular astigmatism.^1,2 In the initial phases of KAMRA inlay use, achieving centration within 100 microns of the intended target was thought to be necessary. However, recent findings have proven centration to be more forgiving, with best results possible when the inlay is placed within 300 microns of the target location. As an investigator for a clinical trial of the small-aperture inlay, I published experience with the recentration of the inlay in two cases.³

The inlay is recentred by lifting the flap and moving the inlay gently until it is in the correct position. In the first patient, the inlay was moved 600 microns temporally, leaving the final position of the inlay very close to the entrance pupil centre. The patient showed remarkable improvement in visual acuity and symptoms. In the second patient, the inlay was perfectly centred on the corneal vertex. However, the patient's visual acuity was still not satisfactory. I recentred the inlay between the corneal vertex and the entrance pupil centre and this significantly improved the patient's quality of vision.