Depth of Intrastromal Corneal Ring Segments by OCT

Abstract

The ICRS actual depth was less than expected. There was mild variability in segment depth, both between segments and along the same segment. No significant difference was found between the depth of Intacs and Kerarings.

Depth evaluation of intended vs actual intacs intrastromal ring segments using optical coherence tomography

“…Although designed for corneal implantation at a depth of 70-80%, this is rarely achieved, as proven by our study and others. 8,13,14 Various methods of assessing segment depth using OCT and Pentacam 14 are referred to in the literature; 8,13,15,16 including measuring from the anterior corneal surface to the apex of the segment; 8 and from the anterior corneal surface to the inner ring of the segment. 13 The method of quantifying segment depth common to all mentioned studies is measurement of the anterior corneal thickness only.…”

“…7 The most common types of ICRS used in clinical practice are Intacs (Addition Technology, Inc., Sunnyvale, CA, USA) and Ferrara rings (Ferrara Ophthalmics, Brazil). 8 Although both are made of polymethylmethacrylate (PMMA), they vary in their radius of curvature and crosssectional shape. The original Intacs segments had 6.77 mm internal radius, 8.10 mm outer radius, 250-450 μm thicknesses, 150 degrees arc length, and a hexagonal cross-section; 9 vs 4.4 mm, 5.60 mm, 200-350 μm, 160 degrees, and a triangular cross-section respectively for Ferrara rings.…”

“…The original Intacs segments had 6.77 mm internal radius, 8.10 mm outer radius, 250-450 μm thicknesses, 150 degrees arc length, and a hexagonal cross-section; 9 vs 4.4 mm, 5.60 mm, 200-350 μm, 160 degrees, and a triangular cross-section respectively for Ferrara rings. 8 Ferrara rings are hence implanted closer to the centre of the cornea and presumably have a stronger flattening effect. 10 Intacs SK are a new segment design by Addition Technology, intended for the treatment of moderate to severe keratoconus.…”

“…11 Shallow implantation is associated with complications such as implant exposure due to corneal thinning over the implant, 12 implant extrusion, 11 anterior stromal compression, 13 compromised diffusion of nutrients to the corneal epithelium, 13 and segment superficialization. 8 Assessing ICRS depth may help predict future complications. Slit lamp examination, Pentacam imaging (Oculus Optikgerate GmBH), and anterior segment optical coherence tomography (OCT) are common methods for assessing ICRS implantation depth, with the latter two techniques providing the most precise assessment.…”

“…Slit lamp examination, Pentacam imaging (Oculus Optikgerate GmBH), and anterior segment optical coherence tomography (OCT) are common methods for assessing ICRS implantation depth, with the latter two techniques providing the most precise assessment. 8,11,14 Patients and methods This is a prospective study approved by the Helsinki Board at Padeh Medical Centre, Poriya, Israel. All applicable institutional and governmental regulations concerning the ethical use of human volunteers were followed during this research.…”