Geometric changes of the eye with an encircling scleral buckle

ABSTRACT

PURPOSE: To investigate the postoperative changes and the mechanism of retinal reattachment, the geometric changes of the eye with an encircling scleral buckle was analyzed using a simplified eye model. METHODS: The simplified eye model is an inelastic sphere with an external diameter of 25 mm and an internal diameter of 23.6 millimeters. With an encircling scleral buckle, it was assumed that the circumference of the eyeball would decrease, and in particular with tightening of the buckle, the cross-section of eyeball would be deformed to an ellipsoid shape. The changes in radius, internal surface area, and volume of the eyeball in relationship to the changes in height and span of the silicone buckle were estimated. RESULTS: The radius of eyeball decreased by 0.19-0.90 mm with an encircling scleral buckle, and varied according to the increment of the tightening of the encircling band. The axial length of the eye increased and the volume of the eye decreased also with increased tightening of the band. The scleral arc of the buckle was shorter than the retinal arc of the buckle by 0.09-0.55 mm and the scleral surface area of the buckle was smaller than the retinal area of the buckle by 56-219 mm 2 ; therefore the retina would be redundant. CONCLUSIONS: An encircling scleral buckle changes the axial length and decreases the volume and internal surface area of the eye, making the retina redundant. This redundancy helps resolve or alleviate the problem of a foreshortened retina in retinal reattachment procedures.