Introduction

Retinal detachment is a rare, but sight-threatening condition characterized by separation of the retina from the underlying retinal pigment epithelium (RPE). Treatment was ineffective prior to the pioneering work of Jules Gonin in the 1920s. Since then the success of treatment has improved so that at least 95% of retinal detachments can now be repaired, although more than one operation may be required.

Epidemiologic considerations and terminology

In the majority of cases, the retinal detachment is due to fluid which gains access to the subretinal space via a retinal hole, so called rhegmatogenous retinal detachment (RRD) (Fig. 60.1). In non-rhegmatogenous detachment the separation arises from serous exudation, or for other reasons, and will not be considered further in this chapter.

Fig. 60.1 Fundus photograph of a retinal detachment.

RRD affects about one in 10 000 adults annually¹, and has a higher incidence in myopes², pseudophakes³, and following trauma⁴.

Clinical features, diagnosis, and differential diagnosis

Patients with RRD may present in a number of different ways. Rarely, asymptomatic detachments are picked up on routine ophthalmic examination. Round hole detachments in young patients tend to present with loss of vision, or a peripheral field defect. In older patients, visual loss is usually preceded by floaters and temporal flashing lights caused by posterior vitreous detachment (PVD).

Anatomical considerations

The subretinal space is a potential one, normally kept dry by the pumping action of RPE cells. If the rate of fluid flow through a retinal hole is greater than the rate at which it can be pumped out, then RRD occurs. The balance between ingress and outflow of fluid can be affected by a number of different factors (Fig. 60.2). Dynamic traction from the vitreous, for example following a PVD, can rapidly accelerate the progression of retinal detachment. Similarly increased concavity in the case of a posterior staphyloma, combined with a presumed reduction in the quality of the RPE pump in high myopes, can produce retinal detachments from macular holes, which do not otherwise occur in macular hole patients.

Fig. 60.2 Factors influencing the balance between ingress and outflow of fluid in the subretinal space. Elasticity of the retina applied to a concave surface produces a resultant force in favor of detachment, which is exacerbated by dynamic traction from the vitreous. These forces are opposed by the pumping action of the RPE.

Ideally, RRD should be treated before the macula becomes detached. Once subretinal fluid has spread to involve the macula (macula off retinal detachments), then permanent damage occurs resulting in reduced acuity and metamorphopsia in the majority of patients.

Retinal holes can be classified into three groups: (i) round holes; (ii) traction, or ‘U’ tears; and (iii) other breaks. Round holes are very common, but rarely lead to RRD⁵. They are usually associated with patches of lattice degeneration. In a small subset of young myopic patients, they can cause slowly progressive retinal detachment, accounting for approximately 5% of patients requiring treatment. The majority of RRDs are caused as a result of one or more traction, or ‘U’ tears secondary to a PVD. The most common location for such tears is the superior temporal quadrant.

Fundamental principles

The principle of treatment for RRD is prevention of fluid flow through the retinal hole. This can be achieved by closing then sealing the hole. Closure of the hole refers to the apposition of retina and underlying RPE, closing the gap between them. Sealing of the retinal hole refers to the creation of a permanent adhesion between the retina and the underlying tissue. As current methods of sealing require the passage of time, it is usual to combine sealing with temporary closure, thus keeping the edges of the hole apposed until the adhesion has developed. Buckles work by creating an indentation of the sclera, thereby closing holes, but also creating a convex surface in favor of re-attachment⁶. Tamponade with gas or silicone oil blocks the retinal hole by surface tension, preventing fluid flow through it. Both cryotherapy and laser create tissue injury which results in chorioretinal adhesion 5–10 days later.

Goals of surgery

The goal of surgery is to achieve permanent retinal reattachment. This should be done using the simplest and safest technique minimizing the risk of complications. Involvement of the macula by the retinal detachment is associated with permanent loss of vision and metamorphopsia. Hence patients with macula-on RRD should be treated urgently.

Indications for surgery

While the majority of retinal detachments require treatment, there are a small number of cases which remain stable, or can even regress. These tend to be young, myopic patients with asymptomatic round holes. Such detachments progress slowly, if at all, and it may be safe to manage such patients conservatively. However, in the majority of cases treatment is required.

Preoperative assessment

The aim of preoperative assessment is to confirm the diagnosis, identify the retinal holes, and plan the most appropriate surgical technique. Although the vast majority of patients presenting with retinal detachments have RRD, the possibility of an exudative retinal detachment must always be considered, particularly if a retinal hole is not seen. The presence of pigment cells in the anterior vitreous (’tobacco dust’) is strongly correlated with the presence of a retinal hole, though a similar sign can occur as a result of iris trauma during cataract surgery (Fig. 60.3). Examination of the anterior segment is important, as it may give clues to the etiology, but is also helpful in determining the quality of the view that the surgeon will get during surgery.

Fig. 60.3 Tobacco dust is pigment in the anterior vitreous, and is strongly correlated with the presence of a retinal hole.

Detailed drawings of the fundus are now rarely performed, but it is very important for scleral buckling surgery to know in advance the number and location of the retinal holes. The fundal view during scleral buckling surgery may be worse perioperatively than preoperatively, in contradistinction to vitrectomy, where the peroperative visualization of the retina is usually better, particularly when wide-angle viewing systems are used. If a decision has been made to carry out vitrectomy, then further detailed examination for detection of retinal holes can safely be left until surgery.

An assessment of the degree of proliferative vitreoretinopathy (PVR) should also be made. The proximity of ‘star folds’ near retinal breaks may mean that vitrectomy is required (Fig. 60.4). Contraction of the vitreous base may be an indication for an encircling buckle.

Fig. 60.4 Fundus photograph of a retinal ‘star fold’, a local contraction of the detached retina due to surface membrane. If close to a retinal break, it can prevent closure, and it may therefore need to be removed.

Anesthesia

Most retinal procedures can be carried out using either local or general anesthesia. Sceral buckling surgery involves traction on muscles, so requires a more effective local block than vitrectomy. The presence of previous buckling surgery is a relative contraindication for local anesthesia, since the presence of the buckle and surrounding scar tissue can prevent the effective dissemination of the anesthetic. Any technique of local anesthesia can be utilized; however, since the conjunctiva is being opened in most cases, a subTenon’s approach is convenient. Both retrobulbar and peribulbar anesthesia have a small risk of globe perforation, particularly in myopic patients.

Operation techniques

There are a number of operative techniques that may be employed by vitreoretinal surgeons in the repair of retinal detachment according to the clinical characteristics of the detachment, presence of PVR, and surgeon preferences.

Scleral buckling

Scleral buckling is a surgical procedure in which indentation of the scleral surface is achieved by suturing a silicone support to the sclera, thus sealing the retinal break, relieving vitreoretinal traction and reducing the flow of fluid into the subretinal space (Fig. 60.5). When combined with retinopexy, chorioretinal adhesion results maintaining retinal reattachment even when the indent subsequently fades.

Fig. 60.5 Fundus photograph showing indentation of the retina following retinal detachment surgery with a scleral buckle.

Scleral buckling is often the procedure of choice in round hole detachments where no PVD is present, in retinal dialysis and rhegmatogenous retinal detachments where breaks are confined to one or two quadrants, and in some cases may also be used in the treatment of detachments with PVR. Relative contraindications include media opacities preventing localisation of all the retinal breaks, giant retinal tears, posterior tears, and the presence of a large number of retinal tears in different meridia.

When placing a scleral buckle, a conjunctival peritomy is performed, followed by scleral inspection to ensure sufficient scleral thickness for safe indentation and placement of scleral sutures. The rectus muscles are isolated and bridled to allow manipulation of the eye during the procedure. Breaks within detached retina are then localized and marked using diathermy to demonstrate their posterior and lateral extension. The position and distribution of retinal breaks dictate the size, position and sometimes the orientation of the scleral explant. Explants may be radial (perpendicular to the ora serrata) or circumferential (parallel to the ora serrata), and may be segmental or held in place with an encircling band. Encircling bands may be used when a permanent indent is required such as in the treatment of PVR or when there is difficulty in detecting breaks for example small anterior breaks found in pseudophakic patients. Once a scleral explant has been selected, retinal breaks are treated with cryopexy prior to suturing the explant to the scleral surface using non-absorbable suture material. Laser retinopexy may also be used, either following drainage of subretinal fluid and application of the buckle or as a secondary procedure once sealing of the break by the indent has allowed sufficient absorption of SRF to allow laser uptake.

During the procedure, drainage of subretinal fluid may be desirable, for example in bullous detachments where the sclera cannot be apposed to the retina, the presence of multiple breaks requiring a large buckle, and in glaucoma patients where significant rises in intraocular pressure are undesirable. Although there are a number of techniques that may be used to drain SRF, they all run the risk of choroidal hemorrhage, retinal incarceration, vitreous loss, and retinal perforation. Subretinal hemorrhage, if subfoveal, can cause permanent visual loss.

Injection of intraocular gas or air may be used to provide additional retinal support in the event of fish-mouthing of retinal breaks, i.e. a meridional retinal fold formed by redundant retina on the posterior slope of the scleral indent, or to reform the vitreous cavity if the eye becomes hypotonous following drainage of SRF.

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