Retinal detachment and PVR

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CHAPTER 60 Retinal detachment and PVR

Louisa Wickham, George William Aylward

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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 annually ¹, 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 RRD ⁵. 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-attachment ⁶. 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.

Pneumatic retinopexy

Pneumatic retinopexy involves the injection of an expansile gas, usually sulfur hexafluoride (SF6) (0.4–0.5 ml), into the vitreous cavity to close retinal breaks, allowing subretinal fluid to be absorbed and chorioretinal adhesion to develop. Retinopexy is achieved using cryopexy at the time of gas injection or laser retinopexy once sufficient fluid has been resorbed. An anterior chamber paracentesis is often performed prior to injection of the gas to allow sufficient space for gas expansion without the risk of a large rise in intraocular pressure.

Success of this procedure requires good compliance with an appropriate posturing regimen to ensure apposition of the retina to the RPE and is therefore more suitable for superior breaks in one quadrant, although a larger area may be treated if a longer acting gas is used, for example perfluoropropane (C3F8) (0.3–0.4 ml).

Expansion of the intraocular gas may cause vitreous traction to the inferior retina and is therefore not recommended in patients with inferior pathology such as lattice degeneration. Other relative contraindications to the procedure include presence of PVR, any media opacity limiting adequate detection of retinal breaks, such as vitreous hemorrhage, and giant retinal tears.

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.

At the end of surgery the position of the buckle is checked in relation to the position of the retinal breaks and the optic nerve checked for signs-arterial pulsation or occlusion indicating raised intraocular pressure. Once the surgeon is satisfied, the buckle is trimmed and the conjunctiva resutured.

Vitrectomy

The use of vitrectomy to manage all forms of retinal detachment is increasing, particularly with the introduction of wide angled viewing systems and improved visualization of the anterior retina.

This technique is particularly suited to patients with a poor fundal view secondary to media opacities such as vitreous hemorrhage, giant retinal tears, multiple breaks in many quadrants, posterior tears when the causal break cannot be identified, and cases of scleromalacia where buckling would be difficult. It is not, however, the procedure of choice in patients who present with round hole detachments without a PVD as inducing a PVD in these cases is technically demanding.

A limited conjunctival peritomy is followed by the siting of an infusion line into the vitreous cavity 3.5–4 mm posterior to the limbus. This is followed by the creation of two further sclerostomies allowing insertion of a light pipe and vitreous cutter. Surgery aims to relieve vitreous traction by trimming the vitreous gel down to the vitreous base, to drain subretinal fluid through the primary break or drainage retinotomy, and to reduce intraocular currents. Injection of a long-acting gas or silicone oil at the end of the procedure closes the retinal break and provides retinal tamponade while chorioretinal adhesion develops. Chorioretinal adhesion around the retinal break is achieved with cryopexy or laser retinopexy.

Following the introduction of air in the treatment of retinal detachment by Ohm in 1911, the use of intraocular gases has become indispensable in the treatment of many vitreoretinal conditions. Pure SF6 expands to about twice its volume in the first 24–48 hours after surgery due to nitrogen from human tissue entering the intravitreal bubble in response to the partial pressure gradient ⁷. SF6 remains within a vitrectomized eye for approximately 10–14 days, being absorbed more slowly than air due to its high molecular weight, low diffusion coefficient, and low water solubility⁷. The non-expansile concentration of SF6 is 18%. C3F8 has a longer duration of action than SF6, expands to four times its volume, and lasts for 55–65 days in the vitrectomized eye. The non-expansile concentration of C3F8 is 12%⁷. Prolonged tamponade may also be achieved using silicone oils, which are linear synthetic organic–inorganic polymers consisting of a chain made of repeating units of siloxane [-Si-O-] units.

Controversy persists about the value of supplementary scleral buckling, and the SPR study gave conflicting results on this issue. The addition of a buckle (which was at the discretion of the surgeon) resulted in better success rates in the pseudophakic/aphakic group but not in the phakic group ⁸. In the treatment of inferior break retinal detachment, some smaller studies have also failed to show an advantage in combining vitrectomy with scleral buckling over vitrectomy alone⁹^–¹¹. Combining scleral buckling with vitrectomy is technically more demanding and is associated with an increased risk of choroidal hemorrhage¹², requires a longer operating time¹³ and has all the associated complications of a scleral buckle, i.e. exposure, refractive change, diplopia, possible decreased retinal blood flow, and risk of anterior segment ischemia¹⁴^–¹⁹.

Although most of the current literature refers to the use of 20-gauge vitrectomy in the treatment of retinal detachment, more recently surgeons have been using small gauge sutureless vitrectomy systems for treating this condition. Initial anecdotal reports suggested that 25-gauge vitrectomy for retinal detachment was associated with a lower success rate, but this may have been learning-curve related. More recent publications show acceptable success rates for 25-gauge and the results of 23-gauge systems are awaited ²⁰.

Intraoperative complications

The risk of intraoperative complications will largely depend on the surgical technique employed.

Pneumatic retinopexy

Following injection of the gas into the vitreous cavity the gas bubble may become trapped at the injection site or in the anterior hyaloid space. Alternatively the gas may form multiple small bubbles; these can be encouraged to coalesce by gently ‘flicking’ the globe. Rises in intraocular pressure are detected by observing the central retinal artery, looking for pulsation or arterial occlusion. If present, the intraocular pressure may be lowered by performing anterior chamber paracentesis.

Scleral buckling

Complications may arise due to deterioration of media clarity required to localize and treat breaks such as a small pupil, corneal edema, perioperative vitreous hemorrhage or lens touch. This may result in incomplete treatment of all retinal pathology and may require a secondary procedure such a laser retinopexy or vitrectomy.

Perforation of the sclera may occur as a result of indentation on unidentified areas of scleral thinning, or placement of deep scleral sutures. Perforation during scleral suturing may be addressed by removing the suture and re-siting it so that the perforation is supported by the buckle. Any retinal perforation should be treated with retinopexy. Perforation following indentation of thinned sclera may be more difficult to manage and in some cases may require a scleral patch graft.

Raised intraocular pressure as a result of scleral indentation occurs commonly and should be monitored regularly during the operation, either digitally or by observing the optic disc for arterial pulsation. Anterior chamber paracentesis, or relaxing one or more of the scleral sutures, may be required to lower the intraocular pressure.

Vitrectomy

The siting of the infusion line at the start of the procedure is a critical step in performing a vitrectomy. If the infusion line is not placed fully into the vitreous cavity at the start of the procedure the infusion fluid will enter the subretinal or choroidal space. Patients with retinal detachments that are bullous or associated with choroidal infusion may require a longer infusion line (6 mm); however, this is associated with an increased risk of lens touch in phakic patients.

Trimming vitreous down to the vitreous base and relieving vitreous traction from retinal tears carries the risk of iatrogenic retinal tears or retinal touch. The risk of iatrogenic retinal trauma is increased when there are media opacities such as vitreous hemorrhage, particularly at the start of the procedure when the retina is not easily identifiable. Iatrogenic tears will require retinopexy and may impact on posturing instructions given to the patient in the postoperative period.

The introduction and removal of instruments during vitrectomy risks retinal or vitreous incarceration into the sclerostomy ports, particularly in the management of bullous retinal detachments. Control of large pressure gradients through lowering the level of the infusion fluid, turning off the infusion during removal of instruments, and plugging sclerostomies may reduce the risk of incarceration. Incarceration may be reversed by performing a fluid gas exchange, but inevitably results in a retinal tear. Introduction of instruments may also result in entry site breaks, and a thorough internal search of the retina at the end of the procedure should identify these.

Lens touch may occur during a vitrectomy, but does not require peroperative treatment unless the view is compromised or there is a large breach of the posterior capsule. Any lens touch should be clearly documented so that future cataract surgery can be planned appropriately.

Postoperative care

Following surgery all patients will require the application of topical antibiotics and anti-inflammatory drops such as dexamethasone. In addition a cycloplegic is often used to reduce ciliary spasm and improve patient comfort.

Patients who have endotamponade in the form of intraocular gas or silicone oil may be required to posture. This is particularly important in those patients who have undergone pneumatic retinopexy.

Rises in intraocular pressure are often seen in patients in the early postoperative period and therefore this should be checked and treated accordingly.

Postoperative complications

Early complications following scleral buckling surgery include refractive changes, particularly increased astigmatism, diplopia due to muscle trauma, acute angle closure glaucoma secondary to forward rotation of the ciliary body, anterior segment necrosis, infection, and choroidal detachment. Late complications include exposure of the buckle, extrusion of the buckle into the vitreous cavity, and surgically induced necrosis of the sclera (SINS) and macular pucker.

The most frequent complication following vitrectomy is the development of cataract. This may occur acutely, when it is observed as a ‘feathery’ posterior capsular opacity and is usually reversible, or as a late complication, usually as nuclear sclerosis or posterior capsular opacification.

In addition, the use of intraocular gases is associated with raised intraocular pressure ⁷. Raised intraocular pressure is more likely following an injection of an expansile concentration of gas. The incidence of elevated pressure ranges from 26–59% however this is usually transient and can be managed medically in most cases⁷.

The clinical complications observed with silicone oil use are thought to occur either from direct toxicity or secondary to the migration and subsequent sequestration of silicone oil in ocular tissues and the associated inflammatory response ²¹. Sequestration of silicone oil within the retina and posterior migration in the optic nerve has also been observed^21,²². Silicone oil is frequently used as a tamponading agent in the treatment of complicated retinal detachments, however its benefits must be weighed against the risk of the complications associated with its use for example cataract, band keratopathy, secondary glaucoma and potentially reduced visual acuity.

Failure of surgery

Regardless of the surgical technique employed, the most frequent complication seen following retinal detachment is that of surgical failure.

Reported primary success rates for RRD repair ranges from 64 to 91%^13,^23,²⁴. Retinal redetachment following initial surgery may occur secondary to the development of PVR, the failure of treatment, e.g. missed or partially treated breaks, or the development of new retinal breaks. A meta-analysis comparing surgical outcomes following pneumatic retinopexy, scleral buckling, and vitrectomy did not find a statistical difference between the final attachment rates of these surgical techniques²⁴.

Risk factors

Conclusive evidence regarding the significance of risk factors for failure of primary retinal detachment repair is difficult to find. Studies investigating risk factors show a number of inconsistencies relating to the different study designs, inclusion criteria and the surgical techniques employed. Furthermore the majority of studies are retrospective. Reported preoperative characteristics that may be associated with an increased risk of surgical failure include the duration of symptoms, the extent of retinal detachment and the involvement of inferior quadrants, an absence of detectable retinal breaks, high myopia, and hypotony. In addition, risk factors associated with the development of PVR including aphakia, uveitis, the presence of vitreous hemorrhage, the presence of PVR preoperatively, raised intraocular pressure, and increased age will also increase the risk of primary failure ²⁵.

PVR

PVR is defined as the growth and contraction of membranes within the vitreous cavity and on both surfaces of the retina following rhegmatogenous retinal detachment. These membranes can exert traction and reopen previously closed breaks, create new breaks, and distort or obscure the macula ²⁶. A revised classification of PVR was produced in 1991²⁷, which was based on that published in 1983 with additional staging of the location and type of grade C PVR (Table 60.1).

Table 60.1 The 1991 classification of PVR ²⁵

(a) General classification of PVR
Grade	Features
A	Vitreous haze; pigment clumps; pigment clusters on inferior retina
B	Wrinkling of inner retinal surface; retinal breaks with rolled or irregular edges; retinal stiffness; vessel tortuosity; decreased mobility of vitreous
CP1-12	Posterior to the equator; focal, diffuse or circumferential full-thickness rigid retinal folds; subretinal strands
CA1-12	Anterior to equator; focal, diffuse or circumferential full-thickness rigid retinal folds; subretinal strands; anterior displacement; condensed vitreous with strands

(b) Sub-classification of Grade C PVR
Type	Location (in relation to equator)	Features
Focal	Posterior	Starfold posterior to vitreous base
Diffuse	Posterior	Confluent starfolds posterior to vitreous base; optic disc may not be visible
Subretinal	Posterior/anterior	Proliferations under the retina: annular strands near disc; linear strands; moth-eaten-appearing sheets
Circumferential	Anterior	Contraction along posterior edge of vitreous base with central displacement of the retina; peripheral retina stretched; posterior retina in radial folds
Anterior displacement	Anterior	Vitreous base pulled anteriorly by proliferative tissue; peripheral retinal trough; ciliary processes may be stretched, may be covered by membrane; iris may be retracted.

* Expressed in the number of clock hours involved.

PVR is the most common cause of failure following retinal detachment surgery, with a reported incidence of 5.1–11.7%²⁸. Where there is a final failure of retinal detachment surgery, in over 75% of cases PVR is responsible²⁸. Elucidation of the risk factors and pathogenesis of PVR has informed research aimed at developing pharmacologic adjuncts to surgical management. Although there have been some successes these agents have failed make a significant impact clinically. The addition of 5-fluorouracil (5FU) and low molecular weight heparin (LMWH) to the infusion fluid at the time of vitrectomy improved success rates in high risk cases; however, in established PVR this combination did not have a positive treatment effect^29,³⁰. In unselected primary detachments, combined 5FU and LMWH appeared to reduce final visual acuity in macula-sparing detachments and this adjunctive combination may have only a limited role in PVR management³¹. Similarly, a perioperative infusion of daunorubicin, although shown to reduce re-operations in established PVR, has not gained widespread acceptance³². Corticosteroids modify cellular proliferation and reduce inflammation, and might therefore be a useful adjunct in the management of PVR³³. Three small studies of intravitreal triamcinolone (TA) in established PVR showed a possible beneficial effect³⁴^–³⁶. In addition to ocular adjuncts, some success has been achieved with systemic agents such as isotretinoin (Accutane), which improved retinal reattachment rates following complex retinal detachment repair³⁷.

Treatment of retinal detachments with PVR can be distilled down to three basic principles:

1 Closure of all retinal breaks

2 Counteraction of traction

3 Minimizing the recurrence of traction

Closure of breaks

Closure of retinal breaks is achieved by stimulating chorioretinal adhesion as described above. In addition to chorioretinal adhesion, closure of retinal breaks may be aided by the use of a scleral indent. Mild cases of PVR with a mobile retina may be treated by conventional, external buckling techniques without vitrectomy, although a broad and moderately high encircling buckle is required to counteract further progression of tractional forces.

Counteraction of traction

Contraction of epiretinal and subretinal membranes may cause new retinal breaks to form or prevent closure of those that have already been treated. Relief of traction may be achieved by a number of surgical techniques including peeling of membranes, retinectomy or retinotomy, scleral buckling, segmentation of periretinal membranes, and long-acting internal tamponade. With the exception of scleral buckling, these techniques require an internal approach.

Membrane peeling

Peeling of epiretinal membranes relieves tangential traction that results in retinal folds. Identification of preretinal membranes may be aided with the use of adjuncts for example,triamcinolone, trypan blue and brilliant blue ³⁸. Epiretinal membranes can be engaged using a vitreoretinal pick, usually by gently moving the pick along the trough of a retinal fold. Once engaged a pair of membrane forceps may be used to peel the membrane off the retinal surface. Movement should commence at the posterior retina moving anteriorly because the retina is thicker posteriorly and provides stronger countertraction than the thinner anterior retina.

Countertraction may be increased further by using a perfluorocarbon liquid, for example perfluorodecalin. Perfluorocarbons possess high density (1.6–2.1 specific gravity) and low viscosity (2–3 centistokes) and are particularly useful in the surgical management of PVR as they may reduce surgical time, decrease trauma from retinal manipulation, aid countertraction, and may be used to stabilize the macula.

Dissection of membranes can be achieved only as far as the posterior border of the vitreous base. Anterior traction extending into the vitreous base requires additional surgical techniques.

Scleral buckle

A circumferential buckle may be used as a way of relieving anterior traction caused by contraction of the vitreous base. In order to achieve sufficient height to the buckle the eye needs to be softened. In a vitrectomized eye, drainage of aqueous fluid through a corneal paracentesis or vitreous cavity fluid via a pars plana needle is usually sufficient to create the space required. In an unvitrectomized eye, aqueous paracentesis may not create enough space and additional procedures may be require, for example, drainage of subretinal fluid, aspiration of vitreous fluid, or limited vitrectomy. In a study of 95 eyes, a combined approach of vitrectomy and scleral buckling resulted in retinal reattachment in 75% of patients with severe PVR (grade D1–D3) compared to a much lower success rate of 19–23% using scleral buckling alone ³⁹.

Retinotomy and retinectomy

Since its introduction by Machemer, relaxing retinotomy (a linear cut in the retina) in conjunction with a retinectomy (removal of contracted retina) has become an accepted technique to mobilize stiff retina. The procedure involves cutting the retina in either a circumferential or a radial manner to relieve traction followed by retinopexy to attach the residual retina, which is then supported by a long-acting intraocular tamponade.

This technique is associated with a poor anatomic and visual outcome and an increased incidence of hypotony ⁴⁰. In a retrospective study of 302 patients who underwent retinectomy, 51% achieved retinal reattachment following one procedure, but only 11.9% had a final visual acuity of greater than 6/24. Using silicone oil as a tamponading agent appears to decrease the risk of postoperative hypotony⁴⁰.

Long-acting endotamponade

The clinical dilemma of whether to use gas or silicone oil as a tamponade agent when treating cases of retinal detachment with PVR was addressed in the Silicone Study. This was a multi-centered, randomized clinical trial designed to evaluated the benefits and risks of using a long-acting gas bubble or silicone oil as an intraocular tamponade following vitrectomy in eyes with severe PVR (grade C3 or greater). When the use of silicone oil was compared with that of a longer-acting gas, C3F8 ⁴¹, there was no statistical difference in the anatomic success rate (73% vs. 64%) or in the number achieving a final visual acuity of greater than or equal to 5/200 (43% vs. 45%) at 18 months. More long-term follow-up (36 months) suggested an advantage favoring C3F8 in achieving complete posterior retinal reattachment (83% vs. 60%, P = 0.045). In a later study, use of silicone oil was associated with a better visual outcome in patients with anterior PVR; however, the anatomic success rate was no better than that observed with C3F8⁴².

Minimizing recurrence of traction

The effects of recurrent traction are minimized by the use of long-acting tamponade agents as described above, which allows the process of PVR to burn out over a 6–8 week period.

Assessment of surgery

Reported primary success rates for rhegmatogenous retinal detachment repair ranges from 64 to 91%⁴³^–⁴⁵. The consequences of failure as a result of PVR on visual function are well documented, with only 11–25% of patients achieving a visual acuity of 20/100⁴¹; however, the functional results following failure without PVR are less well known.

Visual acuity is widely recognized as a major determinant of visual function and as such ophthalmologists rely primarily on visual acuity to define surgical success, and to plan patient management. It is increasingly recognized, however, that patients are more interested in how interventions affect their well being than unidimensional indicators of visual function ⁴⁶. Nevertheless, poor visual acuity has been associated with decreased performance of many activities of daily living, poor cognitive ability, and ultimately poorer health related quality of life (QOL)^47,⁴⁸.

References

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2 Burton TC. The influence of refractive error and lattice degeneration on the incidence of retinal detachment. Trans Am Ophthalmol Soc. 1989;87:143-155. discussion 155–7

3 Tuft SJ, Minassian D, Sullivan P. Risk factors for retinal detachment after cataract surgery: a case–control study. Ophthalmology. 2006;113:650-656.

4 Johnston PB. Traumatic retinal detachment. Br J Ophthalmol. 1991;75:18-21.

5 Byer NE. What happens to untreated asymptomatic retinal breaks, and are they affected by posterior vitreous detachment? Ophthalmology. 1998;105:1045-1049. discussion 1049–50

6 Michels RG, Thompson JT, Rice TA, et al. Effect of scleral buckling on vector forces caused by epiretinal membranes. Am J Ophthalmol. 1987;104:667-670.

7 Chang S. Intraocular gases. In: Wilkinson CP, editor. Retina. St. Louis: Mosby Inc.; 2001:2147-2161.

8 Heimann H, Bartz-Schmidt KU, Bornfeld N, et al. Scleral buckling versus primary vitrectomy in rhegmatogenous retinal detachment: a prospective randomized multicenter clinical study. Ophthalmology. 2007;114:2142-2154.

9 Wickham L, Connor M, Aylward GW. Vitrectomy and gas for inferior break retinal detachments: are the results comparable to vitrectomy, gas, and scleral buckle? Br J Ophthalmol. 2004;88:1376-1379.

10 Sharma A, Grigoropoulos VG, Williamson TH. Management of primary rhegmatogenous retinal detachment with inferior breaks. Br J Ophthalmol. 2005;88:1372-1375.