CORNEAL BIOMECHANICAL CHANGES FOLLOWING KERATOPLASTY PLUS (INTRASTROMAL LAMELLAR KERATOPLASTY COMBINED WITH COLLAGEN CROSS-LINKING) PROCEDURE IN PROGRESSIVE KERATOCONUS – PILOT STUDY

Intrastromal tissue additional transplantation procedure with corneal donor lenticule is a less invasive procedure. This study aims to evaluate the improvement in visual outcomes, corneal biomechanical strength, and stability, following intrastromal lamellar keratoplasty combined with collagen crosslinking (CxL) in progressive keratoconus (KCN) with corneal thickness not suitable for CxL.

A prospective longitudinal study in progressive keratoconus eyes was conducted at a tertiary care centre in New Delhi, India.

A prospective longitudinal study of intrastromal donor corneal lenticule (comprising of Bowman’s membrane(BM) with anterior stroma) implantation along with accelerated CxL was performed on 10 cases of progressive keratoconus. Patients of progressive keratoconus with thinnest pachymetry >380 µm, best corrected spectacle visual acuity (BCSVA) <6/18, those who were intolerant/unwilling for contact lens wear were included. Donor corneal lenticule comprising of BM and anterior stroma prepared using automated microkeratome of 150 microns blade was inserted into femtosecond laser assisted lamellar pocket (created at 180 µm), followed by accelerated CxL treatment. VA (UCVA/BSCVA), MRSE, Scheimpflug corneal topography (Pentacam), ASOCT, Corneal aberrations (i-Trace aberrometry) & CORVIS-ST was performed preoperative, and on post-operative day 1, month-1, 3 & 6 follow-up. Primary outcome measure assessed was corneal tectonic stability; secondary outcome measure was refractive outcome, changes in topography, pachymetry, lenticule thickness and CORVIS-ST parameters.

Mean age of patients was 20.1 ± 3.6 years. Observations at M-6 noted change in CCT from 428.8 ± 22.91μm to 557.5 ± 30.76 µm(p=0.0002); corneal densitometry 14.36 to 20.87 (p<0.05); corneal curvature: flattening of keratometry; K1 (from 50.56±3.23 to 48.83±2.12 D; p=0.04), K2 (55.8±3.09 to 51.78±2.88 D; p=0.0079) and Kmax (61.26±3.45 to 56.78±4.51 D; p=0.007). CORVIS ST parameters, SPA1 (49.21±4.51 to 67.13±18.59, p=0.035) & Deformation Amplitude (1.22±0.10 to 1.14±0.11, p=0.01) improved at M-6. Pre-op UCVA improved from 1.348±0.30 to 1.22±0.27 (p=0.54) and preop BSCVA from 0.673 ± 0.2 to 0.54±0.16 (p=0.83) at M-6. No significant change noted in corneal aberrations.

Preliminary results show that Keratoplasty PLUS procedure comprising of Intrastromal keratoplasty with donor corneal lenticule [comprised of Bowman’s membrane and anterior stroma], combined with CxL may be an effective modality in enhancing tectonic stability, increasing biomechanical strength and to achieve corneal flattening with visual acuity improvement in cases of progressive keratoconus. Current evidence points toward KERAOPLASTY PLUS as an alternative modality to stabilising progressive KCN with thin corneas not suitable fo CxL.