ABSTRACT
To evaluate the effect of implantation depth of Intacs microthin prescription inserts [Addition Technology Inc, Fremont, California] on visual and topographic outcomes in patients with post- laser-assisted in situ keratomileusis [LASIK] ectasias. Retrospective, observational case series. In this case series, 16 eyes of 12 patients were evaluated. All cases were post-LASIK ectasia that had undergone intrastromal corneal ring segment [ICRS] implantation. The planned insertion depth was 70% of stromal thickness using a manual dissector. At least 12 months postoperatively, all eyes underwent Visante [Carl Zeiss Meditec] AS-OCT to determine insertion depth. Cases were categorized into 3 groups based on the measured implantation depth: 40-59% thickness; 60-79% thickness; and >/= 80% thickness. Visual, refractive and topographic outcomes were evaluated relative to implantation depth. The lowest improvement in the study parameters ocurred when the implantation depth was >/= 80%. In this group, uncorrected visual acuity [UCVA] and best spectacle corrected VA [BSCVA] improved less than 0.5 lines. Manifest refractive spherical equivalent [MRSE] and mean keratometry [Km] change was less than 0.5 diopters [D]. The greatest improvements were observed with implantation depth of 60-79% where UCVA and BSCVA increased by 4.5 and 2.5 lines respectively, and MRSE and Km changed by approximately 2.00 D. Less improvement was found when ICRS were implanted between 40-59% of stromal thickness. Implantation of ICRS greater than 80% of stromal thickness may have no effect on visual and topographic status