Abstract
PurposeTo analyze the histological and (ultra)structural stromal tissue changes after femtosecond (Fs) laser–assisted intracorneal ring segment (ICRS) implantation and their refractive and topographic effects in patients with keratoconus.MethodsThis monocentric retrospective case series included 15 consecutive patients with clinical peri-segmental lamellar channel deposits after treatment with Fs-ICRS implantation for keratoconus. The stromal changes were investigated using in vivo confocal microscopy. Two patients underwent a penetrating keratoplasty after the Fs-ICRS implantation; the explanted corneas were processed for histopathology and transmission electron microscopy (TEM). Refractive and topographic effects were investigated comparing the uncorrected (UDVA) and corrected (CDVA) distance visual acuity, spherical equivalent (SE), flat (K1), steep (K2), and steepest (Kmax) keratometry before and after detection of lamellar channel deposits.ResultsIn vivo confocal microscopy revealed diffuse linear and focal granular hyperreflective structures. Histologically, there was mild proliferation of fibroblasts and fibrosis. TEM demonstrated focal accumulations of degenerated keratocytes with cytoplasmic lipid inclusions. There were no significant changes for UDVA (Δ = 0.0 ± 0.2 logMAR; p = 0.67), CDVA (Δ = 0.0 ± 0.1 logMAR; p = 0.32), SE (Δ 0.1 ± 0.9 D; p = 0.22), K1 (Δ = 0.3 ± 1.0 D; p = 0.28), K2 (Δ = 0.1 ± 0.9 D; p = 0.51), and Kmax (Δ = 0.3 ± 1.5 D; p = 0.17).ConclusionsTwo types of structural stromal changes were identified: (1) diffuse peri-segmental fibrosis and (2) lamellar channel deposits. These structural changes showed no evidence of a relevant refractive or topographic effect.
Highlights
Intracorneal ring segments (ICRS) are crescent-shaped arcs of polymethylmethacrylate (PMMA) developed to be surgically inserted into the deep corneal stroma for the purpose of remodeling the corneal curvature
Since 2004 and the approval of the Food and Drug Administration (FDA) for Intacs (Addition Technology Inc., Des Plaines, IL, USA) [6], the surgical procedure has been proven effective in improving the refractive and topographic outcomes of patients with KC [7,8,9,10,11], and the method has been extended to a larger spectrum of corneal ectasia, such as pellucid marginal degeneration (PMD) [12,13,14] and corneal ectasias after laser vision correction (LVC), e.g., after laser in situ keratomileusis (LASIK) [15, 16]
Ruckhofer et al analyzed these deposits using in vivo confocal imaging and scanning electron microscopy on explanted ICRS [24] and supported the hypothesis of lipid deposits in the free space between the ICRS and the stromal tissue
Summary
Intracorneal ring segments (ICRS) are crescent-shaped arcs of polymethylmethacrylate (PMMA) developed to be surgically inserted into the deep corneal stroma for the purpose of remodeling the corneal curvature. Since 2004 and the approval of the Food and Drug Administration (FDA) for Intacs (Addition Technology Inc., Des Plaines, IL, USA) [6], the surgical procedure has been proven effective in improving the refractive and topographic outcomes of patients with KC [7,8,9,10,11], and the method has been extended to a larger spectrum of corneal ectasia, such as pellucid marginal degeneration (PMD) [12,13,14] and corneal ectasias after laser vision correction (LVC), e.g., after laser in situ keratomileusis (LASIK) [15, 16]. The Intacs SK (for “Severe Keratoconus”) (Addition Technology Inc., Des Plaines, IL, USA) was developed for the 6–7 mm optical zone with the aim to correct larger myopic and astigmatic refractive errors in more advanced forms of corneal ectasia [17]. New designs with asymmetric progressive thickness emerged to treat KC with specific asymmetric phenotypes in corneal topography such as “duck” and “snowman” phenotypes [18, 19]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
