Purchase this article with an account.
S. Kling, L. Remon, A. Pérez-Escudero, J. Merayo-Lloves, S. Marcos; Biomechanical Response of Normal and Cross-linked Porcine Corneas. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5477.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Knowledge of the corneal biomechanical response is important to understand refractive or therapeutic corneal treatments. Corneal collagen cross-linking with riboflavin (CXL) aims at increasing corneal stiffness to treat keratoconus or ectasia. We studied corneal response of cross-linked and untreated porcine corneas to variable intraocular pressure (IOP).
Enucleated pig eyes were infused with saline solution and IOP monitored with a transducer. A Scheimpflug-imaging 3-D corneal topographer (Pentacam, Oculus) was used to measure anterior and posterior corneal shape and thickness. We used 26 eyes: 6 controls (CXL and noCXL, under constant IOP) and 20 with varying IOP. The epithelium was removed and 0.125% riboflavin solution instilled in all eyes. Test eyes were illuminated with UV-light (365 nm, 2.038 mW), 12-mm diameter, for 30 minutes. Both eyes were placed in a wet chamber (humidity and temperature monitored) and Scheimpflug images were obtained alternatively and automatically while the IOP increased from 5 to 50 mm Hg (and then decreased) at 5 mm Hg steps. The eyes were preserved at 3.5ºC and measured 24 hours later. Control eyes were measured during the same period. The optical parameters were analysed with routines written in Matlab.
(1) Instillation of riboflavin reduced corneal thickness (by 286±20 µm on average). (2) Immediately after treatment corneal thickness changes are dominated by hydration (no significant difference between constant and varying IOP). (3) The cornea (anterior and posterior) flattened with increased IOP and steepened with decreased IOP, but the effects were higher in noCXL than in CXL corneas. Differences were observed on the vertical meridian immediately after CXL, but were larger and on both meridians after 24 hours. Average anterior vertical radius changed at 26.3 (noCXL) and 15.1 (CXL) µm/mmHg -increased IOP and -22.1 (noCxL) and -13.4 (CXL) -decreased IOP-, inmediately after treatment. Anterior horizontal radius changed at 12.4 (noCXL) and -0.9 (CXL) µm/mmHg -increased IOP-, and -14.2 (noCXL) and -0.9 (CXL) -decreased IOP- after 24 hours. The largest differences occurred for the posterior horizontal radius: 18.92 (noCXL) and -0.7 (CXL) µm/mmHg -increased IOP- and -24.2 (noCXL) and -0.3 (CXL) µm/mmHg -decreased IOP-. (4) Differences also occurred in asphericity, that increased with IOP.
CXL alters the biomechanical corneal response to variable IOP, consistent with increased stiffness. Corneal biomechanical models can use this data to improve the predictability of the procedure.
This PDF is available to Subscribers Only