Abstract
Purpose :
Scleral buckling influences the shape of the cornea, anterior chamber, and axial length. Corneal thinning from disease or refractive surgery can cause different morphologic changes compared to normal corneal thicknesses. We evaluated how the application of an encircling scleral buckle changes the anterior chamber depth, shape of the cornea, and refractive properties of the eye in models of normal and thin corneas and with increased scleral compliance.
Methods :
A three-dimensional finite element model of the eye was developed to investigate the effect of an encircling scleral buckle on eye deformation. Linearly elastic mechanical properties of the eye tissues were assumed with the elastic modulus and Poisson’s ratio of the sclera, cornea, retina, zonules and lens taken to be (3 MPa, 0.47), (1.5 MPa, 0.42), (0.02 MPa, 0.49), (360 MPa, 0.4) and (6.88 MPa, 0.49), respectively. Complaint, stiff, and high stiff models were created with elastic module of sclera at 1.8, 3, and 5.5 MPa and cornea at 1.5, 1.5, and 3 MPa. Initial intraocular pressure and anterior chamber depth were assumed to be 15 mmHg and 2.75mm. Central corneal thickness was 0.6 mm and 25% and 50% thinning of the cornea were considered. The band was assumed to be 2.5, 3, or 3.5mm wide. Buckle heights of 0.5, 1 and 1.5 mm were evaluated. Anterior, equatorial, and posterior positioning of the band was assumed to be 11.5, 12.6, 13.7mm, and 14.8mm behind the limbus respectively.
Results :
Axial length and overall power of the eye increased with buckling, with larger increases in eyes with greater buckle indentation, anterior band positioning, or corneal thinning. Anterior chamber depth was decreased after buckling in eyes with normal corneal thicknesses, with a greater effect seen with a more anterior band. Conversely, for eyes with 50% thinning of the cornea, an increase in anterior chamber depth was noted. Stiff and high stiff elastic models had 0.43% and 0.75% less axial lengthening than the compliant model.
Conclusions :
Anterior chamber depth and overall power of the eye increase after encircling buckles, with greater effect seen with a more anterior buckle and in eyes with corneal thinning. While anterior chamber depth generally decreases after buckling, eyes with 50% corneal thinning showed an increase in depth. Increased scleral compliance causes greater increases in axial length after buckling.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.