The Biomechanics of Scleral Buckles in the Treatment of Retinal Detachment

Scleral buckling is a surgical intervention used primarily to treat rhegmatogenous retinal detachment. By placing an external explant on the sclera, the surgeon creates an indentation that mechanically supports the retina. This paper reviews the biomechanical principles governing how these buckles function, specifically focusing on how they modify the eye's shape, reduce vitreoretinal traction, and alter intraocular fluid dynamics to promote healing.

A scleral buckle fundamentally changes the eye's geometry, transforming it from a sphere into a prolate spheroid or even a dumbbell shape, depending on the buckle's tightness and position. This transformation often results in changes to the axial length, which can induce temporary myopia or, in some cases, hyperopia. Furthermore, the buckle can cause corneal astigmatism, particularly when using radial sponges that transmit tension to the anterior segment. The paper emphasizes that these refractive changes are often transient as the buckle material undergoes stress relaxation over time.

The primary goal of the buckle is to counteract the forces that lead to detachment, such as vitreous traction and fluid flux through retinal breaks. By indenting the sclera, the buckle reduces the circumference of the vitreous base, thereby decreasing transvitreal traction. It also creates a favorable vector force: while epiretinal membranes naturally pull the retina inward (promoting detachment), a buckle can reverse this, creating an outward force that presses the retina against the eye wall. This works in concert with natural physiologic mechanisms, such as the retinal pigment epithelium (RPE) pump, to seal retinal tears.

The study highlights that the effectiveness of the procedure relies on precise tension and placement. The "fishmouth phenomenon," where a radial fold crosses a retinal tear, illustrates the risk of excessive circumferential shortening. Understanding the relationship between scleral chord length and arc length is essential for surgeons to place sutures accurately. Ultimately, the success of the buckle relies on balancing the reduction of mechanical traction with the creation of a stable chorioretinal adhesion, ensuring long-term retinal integrity.