Monday, January 30, 2023

Scleral Buckle

Overview

Background

A scleral buckle is performed to repair a retinal detachment by reestablishing the anatomic proximity of separated retina from its underlying tissue. An acute retinal detachment is an ophthalmologic emergency that can rapidly progress to irreversible vision loss in the affected eye.

The neurosensory retina depends on its underlying layers (the retinal pigment epithelium and choroid) for delivery of oxygen, trophic factors, and nutritional substrates. Therefore, any damage or disruption in the conduit between the layers has great potential to lead to ischemic damage and cell death. The vast majority of detachments are caused by the formation of tears (rhegma) in the retina, which allow the entrance of liquefied vitreous into the subretinal space, leading to subsequent separation of the neurosensory retina from the underlying retinal pigment epithelium.

The principle of scleral buckling is based on the need to collapse the anatomic space created between the detached sensory retina and the retinal pigment epithelium. This is done by the inward indentation of the sclera from the exterior, creating a ridge (or buckle) that reduces the fluid underneath the tear and allows for the re-apposition of separated layers, thus reestablishing their physiologic connection. The sclera itself is most commonly indented by placement of a permanent explant or intrascleral implant with sutures, although temporary buckles have been used in variations.

The external indentation from the buckle explant reduces the volume of the globe, and in doing so relieves a portion of the vitreous traction contributing to the retinal tear and detachment. Although this procedure involves exposure of the globe and considerable intraorbital manipulation, it is most often performed on an outpatient basis.

In addition to the placement of the explant to displace the eye wall inward, it is important that the retinal tears are sealed by the formation of chorioretinal adhesions. This is performed by inducing a chorioretinal scar via cryotherapy, diathermy, or laser energy. In conjunction with the generation of such adhesions, the physical closure of the break by the explant/implant enables the attachment of the retina. The dynamic forces that generated the detachment (vitreoretinal traction and inflow of liquefied vitreous) are thus countered by these maneuvers.

Once secured, the normal physiologic and metabolic forces preventing separation may then maintain retinal attachment. Depending on the extent of detachment, the degree of fluid and any associated pathologies, there may also be indications for auxiliary procedures during the placement of the scleral buckle, such as the removal of accumulated subretinal fluid and/or the injection of intravitreal gas.

Although modalities such as vitrectomy and pneumatic retinopexy are increasingly used to manage retinal detachments, buckling continues to be an important and useful approach in many clinical scenarios. In addition to the placement of scleral buckles as a primary and solitary procedure, they are often used in combination with pars plana vitrectomy in order to address complicated retinal detachments and provide further support. Given the poor visual outcomes that attend the course of an uncorrected detachment, scleral buckling is most often performed on an emergent to urgent basis, especially in the setting of macula-sparing detachments.

Indications

Scleral buckling is indicated for the following conditions:

Rhegmatogenous retinal detachment, especially in phakic eyes

Young patients with attached posterior hyaloid

Detachments due to dialysis without retinal tear

Complex retinal detachments involving multiple tears

The most common mechanism causing retinal detachments is the formation of rhegmas or full-thickness tears in the retina. Rhegmatogenous detachments account for 90% of detachments, resulting from the traction exerted on the retina by the posterior vitreous. As the rhegma forms, liquefied vitreous is allowed access to a pathway into the subretinal space. It subsequently acts as a wedge to separate the neurosensory retina from the retinal pigment epithelium.

Although the initial presentation of patients with symptomatic detachment can vary widely, there are common salient features, including the following symptoms:

Photopsia (flashing lights related to mechanical stimulation of the retina through vitreous traction)

Floaters (due to detachment of vitreous with or without vitreous hemorrhage)

Visual field defects (often described by the patient as a sudden black curtain or veil that may enlarge over time)

Decreased visual acuity (noted in detachments involving or threatening the macula)

Detachments may be due to dialysis, in which the retina detaches circumferentially from its insertion point at the ora serrata on the retinal periphery. This is a less common etiology and is most often seen in the setting of trauma and in young patients.

Rhegmatogenous retinal detachments complicated by tractional forces from proliferative vitreoretinopathy, as well as other proliferative processes such as diabetic retinopathy, require vitrectomy along with scleral buckling when the traction is present in the peripheral retina in order to achieve high success rates of reattachment. These surgeries may also require advanced surgical techniques, such as intraocular gas insufflation, membrane peeling, silicone oil instillation, and creation of retinectomies (incisions in the retina).

Contraindications

Detachments that emanate from breaks anterior to the equator (the anterior-posterior circumferential midpoint of the globe) are more amenable to placement of buckles. Breaks significantly posterior to the equator are anatomically more difficult to approach owing to hindrances from the bony orbit and poor surgical exposure. As such, posteriorly located breaks are best addressed with vitrectomy.

Opaque media may preclude visualization of retinal tears and thus proper discovery of all the breaks. This is most often seen in scenarios of vitreous hemorrhage, such as in the setting of severe retinal neovascularization due to diabetic retinopathy.

In patients with significant vitreoretinal traction, such as with proliferative vitreoretinopathy and diabetic neovascularization, using a scleral buckle exclusively is usually insufficient to reattach the retina. However, buckling may be used as part of the surgical approach in addition to vitrectomy.

Many surgeons prefer to avoid possible anterior ischemia caused by buckling in patients with vaso-occlusive disease, such as sickle cell anemia and, to a lesser extent, severe diabetic retinopathy.

Technical Considerations

Best Practices

If there is a significant tractional component to the retinal detachment, such as in proliferative vitreoretinopathy and proliferative diabetic retinopathy, a vitrectomy approach needs to be used in order to mechanically peel away the causative membranes.

If subretinal drainage is used, it is important to avoid retinal incarceration into the drainage tract.

Procedure Planning

The most crucial aspect of any approach to treating rhegmatogenous detachments is the ability to localize and account for all the retinal tears. Failure to locate and treat a tear would predispose any technique to failure because it allows for the new influx of subretinal fluid. When placing a primary buckle, this is performed with intra-operative indirect ophthalmoscopy via the aid of a condensing lens, typically a 20- or 28-D lens. The use of scleral indentation to bring the peripheral retina into view is necessary in order to achieve full visualization.

Initially, full visual acuity testing should be performed to assess the patient’s baseline level of vision. This is crucial in the primary care or emergency department setting. A drastically reduced visual acuity may be an indication of macular involvement and thus may lessen the need for a more urgent intervention. However, even macula involving detachment are best repaired within 7-10 days for optimum visual acuity recovery.

Extraocular muscle testing is important to establish a baseline because strabismus may develop postoperatively.

Tonometry is indicated because retinal detachment frequently lowers intraocular pressure. Postoperatively, buckling may increase intraocular pressure as a function of volume reduction. As such, it is important to establish any history of glaucoma.

Laboratory tests, as guided by the medical history, may be requested as part of the preoperative evaluation. Coexisting systemic diseases may increase anesthetic and surgical risks, as well as the potential for local complications (eg, thrombocytopenia).

Outcomes

Postsurgical visual outcomes are related to the extent of initial macular involvement. Anatomic reattachment is achieved in close to 90% of cases. However, there may be a significant discrepancy between favorable anatomic correction and functional visual outcomes.

The most important issue dictating success in restoring visual acuity is the presence of macular involvement. In macula-off detachments (in which the detachment includes the central retina, the macula), only 50%-60% of patients have restored visual acuity of 20/50 or better.
Visual restoration is much more likely in detachments sparing the macula,
with one large series reporting that 90% of such patients had vision of 20/40 or better following surgery.

Factors predicting poor visual function include the following:

Age (>70 y)

Macular detachment occurring more than 7 days prior to surgery

Severe proliferative vitreoretinopathy

Intraoperative hemorrhage

Overall, and not surprisingly, the most reliable predictor for poor postoperative outcome is poor preoperative visual acuity.

Relevant Anatomy

The sensory retina, composed of photoreceptors and adjacent ganglion cells, overlies the retinal pigment epithelium. The blood supply for the sensory retina is derived from two circulations, both originating from the ophthalmic artery. The anterior circulation comes from the retinal artery as it branches into arterioles that course along the surface of the sensory retina and supply the inner (more proximate to the vitreous) layers. Changes in this circulation are seen with vitreous retinopathy, most commonly in patients with diabetes, who are predisposed to tractional detachments. The posterior (uveal) circulation supplies the outer segments of the retina (the photoreceptors and the retinal pigment epithelial). It is the loss of contact with this supply that proves disastrous in the course of detachment.

The peripheral edge of the retina is defined by the ora serrata, the junction with the ciliary body located anteriorly. In this region, the inner and outer retinal layers are tightly adherent.

The sclera is the protective outer covering of the eye composed of fibrous connective tissue. It has the structural integrity to support the placement of an explant. The sclera itself is contained within the Tenon capsule, which merges anteriorly with the conjunctiva. These two structures must be penetrated to place the buckle.

For more information about the relevant anatomy, see Retina Anatomy.

RELATED ARTICLES
- Advertisment -

Most Popular