Intrastromal corneal ring segments: Effect of relationship between alignment and topographic keratometric meridians

Abstract

No author has a financial or proprietary interest in any material or method mentioned.

Predictors of Successful Outcome following Intrastromal Corneal Ring Segments Implantation

“…Tu et al (2012) reported greater but non-significant reduction in refractive errors and keratometric astigmatism for incisions on the flat meridian compared to those performed on the steep meridian or oblique sites. 24 Although there is no general agreement on a particular reference site, in most studies, the steepest corneal meridian was used as an optimal location. 40 The location used in the current study was on the steepest topographic meridian.…”

“…20 In order to obtain the optimal clinical outcomes after the ICRS implantation, each manufacture provides a specific nomogram to help clinicians select the best ring characteristics according to clinical data. The available nomograms A c c e p t e d M a n u s c r i p t 5 were mainly developed based on the distribution of ectatic corneal region, its symmetry status, and the spherical/cylindrical components of refractive error, while other factors such as preoperative visual acuity, 9 mean keratometry, corneal topographic pattern, 21 keratoconus grading, 15,22,23 aberrations, 10 coincidence between refractive, topographic and comatic axes, 24,25 incision location, 24,26 corneal biomechanical properties, 22,27,28 and internal astigmatism 15 may affect the surgical outcome.…”

Polar Value Analysis of Corneal Astigmatism in Intrastromal Corneal Ring Segment Implantation

“…Segments 6 mm in diameter decreased the corneal astigmatism by 1.54 D at 99° from the preoperative steep meridian. Vectorial analysis of ICRS implantation was performed in a few studies [ 7 , 8 ]. Our results agreed with an earlier study in that the corneal astigmatism decreased after vector analysis.…”

“…Our results agreed with an earlier study in that the corneal astigmatism decreased after vector analysis. Meanwhile, reports by Tu et al [ 7 , 8 ] indicated that the maximum reduction in astigmatism (–2.67 D) occurred when the incision was placed in the flat meridian (perpendicular group) and the least effect (–0.65 D) was when the incision was placed in the steep meridian (meridional group). The differences in study design and analysis make it difficult to directly compare these previous results with those of the present study.…”

“…Vector analysis research indicated that the maximum reduction in astigmatism was obtained when the incision and segments were placed along the flat topographic meridian [ 7 , 8 ]. However, the nomogram for choosing the segment size and incision meridian in these previous studies differed from that recommended by the manufacturer.…”