39 Rhegmatogenous retinal detachment

Background

Retinal detachment is a relatively rare condition but comprises a significant proportion of the workload of vitreoretinal surgeons. As opposed to tractional or exudative retinal detachment, the pathognomonic feature of rhegmatogenous (Greek rhegma, “tear”) retinal detachment is the presence of a full-thickness break or hole in the retina through which fluid from the vitreous cavity can pass and accumulate in the subretinal space. Central vision is impaired if this fluid accumulates under the fovea, and left untreated the retina may become totally detached, scarred and irreparable. A potentially blinding condition, considered untreatable until the 1920s, its prognosis has significantly improved in recent decades with advances in surgical techniques.

Aetiology

For a primary or secondary rhegmatogenous retinal detachment to occur, three factors must coexist: a fullthickness retinal break, liquefied vitreous and, arguably, traction on the adjacent retina.

In primary detachments, full-thickness retinal breaks occur spontaneously. These may be either as atrophic round holes often found in areas of lattice degeneration, as U- shaped tears in the retinal periphery complicating posterior vitreous detachment formation, or as retinal dialyses (disinsertions) at the ora serrata.

Posterior vitreous detachment (PVD) is considered a normal process and is age-related: vitreous lacunae have been reported in 90% of the population over the age of 40, and posterior vitreous detachment is found in 27% of individuals aged 60 to 69, and in 63% aged 70 or over.1 In comparison to the high incidence of normal syneresis and PVD formation, progression to retinal U-tear formation is rare. Tears may form either as a result of unusually strong vitreo-retinal adhesion or at an area of relatively thin or weak retina, often in the region of lattice degeneration or a retinal blood vessel, resulting in vitreous haemorrhage. Round holes and operculated breaks rarely progress to retinal detachment, in contrast to retinal U-tears, giant tears or dialyses, in which the risk of detachment is high. The latter three conditions all have associated vitreal traction on

the edge of the full-thickness tear. Once started, the retinal detachment usually progresses with the accumulation of further subretinal fluid until the entire retina including the macula is detached and floating freely, constrained by its attachments to the ora serrata and the optic nerve.

Prognosis

The natural history of total retinal detachment is for the retina to become ischaemic and to lose function. Usually proliferative retinopathy ensues as a typical scarring response, but this results in stiffening and contraction of the retina. Once the contraction involves the ciliary body, ocular hypotony and, later, phthisis follows. Sometimes the retinal detachment becomes stable and remains localised, usually inferiorly, the long-standing nature reflected by the development of a pigmented tide-mark at the edge of the detachment. Rarely the ischaemic retina develops surface neovascularisation and rubeosis iridis.

With surgical repair, approximately 95% of retinal detachments will be reattached. Visual acuity is usually maintained if the macula is not involved. However, if the acuity has fallen due to macular involvement the recovery of acuity is less predictable and usually partial.

Treatment of retinal detachment is surgical and has been evaluated in some prospective randomised controlled trials. Easily measured end-points in most studies are the first-time and final reattachment rates, final visual acuity and the incidence of complications.

Question

Which is the best method of retinopexy?

The evidence

In vitro2 and in vivo experiments3 have studied retinal adhesion and methods of retinopexy. There is little to choose between laser and cryotherapy as methods of retinopexy. Cryotherapy is quicker, in that a larger area can be treated with one application, and indentation with the cryotherapy probe may allow holes to be treated in the presence of subretinal fluid. Laser is more precise, less

inflammatory and perhaps better if extensive areas require treatment. The ultimate adhesive strength of both laser and cryotherapy scars is twice normal by two to three weeks, but laser adhesion takes one day compared with five for cryotherapy. Cryotherapy also disperses pigment epithelial cells, which theoretically may increase the risk of proliferative vitreoretinopathy (PVR) formation, but this has not been proven. Cryotherapy and laser have not been formally compared in a prospective randomised controlled trial (RCT).

Comment

Thus, all forms of retinopexy appear to be effective in the long run, presumably by inducing scar formation; however, if a rapid bond is required, laser photocoagulation or diathermy are probably preferable.

Question

Is there a need for drainage of subretinal fluid?

The evidence

120 consecutive patients undergoing scleral buckling procedures. The study excluded cases in which drainage was either impossible (due to the shallow nature of the subretinal fluid) or essential (for example, for very bullous detachments) and matched the two populations very accurately. Surgery was carried out by a single surgeon, and the decision on whether to drain subretinal fluid was assigned at random preoperatively, and there was no significant difference in the first time rate of flattening (87% in the drainage group v 82% in the non-drainage group), final flattening rate (97% in both groups) or visual acuity outcome.

Comment

It can be concluded that drainage of subretinal fluid is only indicated in specific situations, many of which (for example, giant retinal tears, detachments due to macular breaks and proliferative vitreoretinopathy) have since been managed by vitrectomy.

Current practice for drainage in scleral buckling surgery is to allow closure of the retinal breaks during cryotherapy, in order to make space within the eye to allow a large scleral indent and to allow better visualisation of breaks in bullous detachments. Drainage is not free from potential

complications, which include choroidal haemorrhage, retinal incarceration and intraocular infection.

Question

Which is the best method of drainage?

The evidence

Several methods of drainage have been described: scleral cut-down and choroidal puncture with diathermy, needle drain where the sclera and choroid are punctured in one stab with a 3 mm suture needle, and the laser drain where a scleral cut-down is performed and the choroid punctured by argon laser via an indirect ophthalmoscope or endoprobe.

Three trials have prospectively compared needle and laser drainage. Das and Jalali5 showed an increased complication rate in the needle drainage group (4/25) than in the lasered group but provided no statistical analysis. Ibanez et al.6 similarly randomised 175 patients to either laser drainage choroidotomy using an endoprobe, or needle drainage. No significant difference was found in the complication rate between the two groups (13% v 16%). Aylward et al.7 performed a randomised prospective, controlled trial comparing suture needle drainage with argon laser drainage in 1995. Argon laser drainage was associated with a higher rate (98%) of complete or partial but adequate drainage, compared with suture needle drainage (85%), and a lower rate of clinically significant subretinal haemorrhage (4·3% v 28·3.%, respectively). The larger sclerostomy created by the argon laser drain was not associated with any increase in the rate of retinal incarceration between the two groups.

Comment

Subretinal haemorrhage is problematic if it tracks back under the macula. Therefore, current practice favours the expediency of a needle drain when the macula is attached and the submacular space is closed, while the safer laser drain is preferred when the macula is off.

Question

When should cryotherapy be carried out if drainage is necessary?

The evidence

Cryotherapy is thought to dilate the choroidal vasculature. Traditionally the sequence of surgical steps was

to carry out cryotherapy after drainage in order to decrease the risk of choroidal haemorrhage. Pearce et al.8 randomised 80 cases undergoing scleral buckle procedures either to the surgical sequence of drain, air, cryotherapy, explant or cryotherapy, drain, air, explant. The incidence of subretinal haemorrhage in each of the groups was low and not significantly different.

Comment

Current opinion is that providing needle drainage is technically well performed with elevation of the intraocular pressure at the time of drainage, the sequence of steps is less important.

Question

Is it necessary to soak silicone sponge explants preoperatively?

the vitreous base. Which should be used in aphakic patients: this was the subject of a randomised trial by Singh.10 Eighty-four patients with aphakic retinal detachments were randomised either to local scleral buckling or one combined with scleral encirclement. Both techniques had similar first time anatomical reattachment rates (90% and 91%, respectively).

Comment

Encirclement offers no advantage over local buckling, except that the indent is permanent. Aphakic retinal detachment is less common though still an issue in developing countries where intracapsular extraction is still performed.

Question

Does pneumatic retinopexy have a role in retinal detachment repair?

The evidence

The two commonly used types of scleral explant are silicone sponges or the harder solid silicone bands. A higher infection rate has been associated with silicone sponges compared with the solid elements, probably due to their porous nature, which means the sponge can harbour bacteria if it is contaminated preoperatively. Arribas et al. carried out a prospective trial to determine whether preoperative soaking of the sponge would reduce the rate of infection and extrusion. In 921 consecutive cases in which a sponge was used, for every alternate case the sponge was soaked in a 2 ml aqueous solution of penicillin (500 000 units) and gentamicin (40 mg). Peroperative soaking was associated with a seven-fold reduction of infection and extrusion of the explant.9

Comment

Although this trial was not a properly randomised study, it suggests that soaking sponge explants in antibiotic reduces the rate of infection.

Question

Is encirclement necessary in aphakic patients?

The evidence

An explant may be either a localised buckle placed over the break or an encircling band placed around the region of

The evidence

Pneumatic retinopexy was described by Rosengren in 193811 but did not become popular until the 1980s in United States.12 The technique involves treating the retinal break with cryotherapy and then injecting a gas bubble into the vitreous cavity to tamponade the break. The patient is required to posture in order to allow the gas bubble to press against the break and flatten the retina allowing adhesion to occur. It is a relatively quick procedure that can be carried out under local anaesthetic with the patient as an outpatient. Several controlled trials have evaluated the results.

Injecting gas and applying cryotherapy, without performing a vitrectomy (pneumatic retinopexy), was found to have a comparable success rate to vitrectomy with cryotherapy and gas in a prospective randomised controlled trial of 120 cases in 1987.13 The Retinal Detachment Study Group conducted a multi-centre trial comparing pneumatic retinopexy with scleral buckling, and reported results in 198 patients at six months14 and in 179 patients at two years follow up.15 At six months, there was no significant difference in either first time (82% v 73%) or final (98% v 99%) reattachment rate for scleral buckling and pneumatic retinopexy, respectively. Pneumatic retinopexy, however, had less morbidity and better visual acuity. Importantly, this study showed that aphakic or pseudophakic eyes had lower reattachment rates with pneumatic retinopexy. At two years follow up, the retinal detachment recurrence rate was small (1%) in each group, but the incidence of cataract was significantly greater in the scleral buckling group. Better visual outcome in the pneumatic retinopexy group persisted.

Mulverhill et al.16 randomised 20 consecutive patients, who met inclusion criteria, to be treated either by scleral buckling or pneumatic retinopexy. Retinal flattening was achieved in one operation in 90% of the pneumatic retinopexies and 100% of the scleral buckles. Visual outcome was comparable between the two groups.

However, in a meta-analysis of pneumatic retinopexy compared to primary scleral buckling procedures, scleral buckling was found to have a higher primary success rate than pneumatic retinopexy.17

Comment

Pneumatic retinopexy is an effective procedure and has found its strongest advocates in the United States where office-based procedures are more common. Since the success rate is only marginally less than scleral buckling, it is a viable alternative and is often used in patients unfit for general anaesthetic or when access to an operating theatre is difficult.

Question

Is an internal approach the best method?

The evidence

There have been no randomised controlled trials comparing an external and internal approach, although one multi-centre trial is currently under way in Europe.

Comment

Internal approach by vitrectomy, internal search, retinopexy and internal tamponade is increasing in popularity as the primary approach for retinal detachment repair. It offers the advantages of easier visualisation with internal illumination, magnification from the microscope and scleral indentation, arguably reducing the risk of failure from a missed retinal break. The disadvantages of vitrectomy are that cataract is very common postoperatively, there is a risk of endophthalmitis (not present in an external approach not requiring drainage), and there is a higher risk of inflammation and proliferative vitreoretinopathy. The internal approach is thought to be specifically indicated if the retinal break is large and/or posteriorly placed, for giant retinal tears (since it allows the tear to be unfolded and the vitreous cleared from behind the tear), and in any retinal detachments that require internal manipulation, such as clearance of vitreous haemorrhage, removal of PVR membranes or retinectomy. Retinal detachments in pseudophakic eyes are also more easily managed by

vitrectomy, since the breaks are usually small and close to the ora serrata, and hence difficult to visualise externally. Vitrectomy may also be combined with scleral indentation, either segmentally or by encirclement.

Question

Is silicone oil superior to long-acting gas in retinal detachment repair by vitrectomy?

The evidence

The choice of intraocular tamponade in vitrectomy depends on the duration of tamponade required and the size and location of the tear. Agents currently available are sulphahexafluoride (SF6), hexafluoroethane (C2F6), perfluoropropane (C3F8) and silicone oil.

When using intraocular gas as a tamponading agent, the use of nitrous oxide as an anaesthetic agent is generally considered contraindicated as this can adversely affect the size of the gas bubble. In a small prospective randomised trial comparing patients given nitrous oxide or propofol as an anaesthetic agent the postoperative volumes of intraocular gas were found to be similar.18

Peyman et al.19 carried out a randomised trial comparing the use of gas (20% C3F8 or 30% C3F8) and silicone oil in a group of 50 patients with complex retinal detachments or vitreous haemorrhage. Unfortunately, the patients were of mixed diagnoses, including proliferative diabetic retinopathy (PDR) with or without retinal detachment and with or without vitreous haemorrhage, proliferative vitreoretinopathy (PVR), and traumatic retinal detachment. Both groups achieved a high anatomical success rate (82% in the oiltreated and 83% in the gas-treated groups), and there was no significant difference in the visual outcome. However, the gas-treated group was associated with a greater incidence of late elevation of intraocular pressure and with postoperative vitreous haemorrhage.

The Silicone Oil Study Group conducted a large multicentre randomised controlled trial in the United States between 1 September 1985 and 31 October 1990 in 11 centres. The main objective of the study was to compare silicone oil with intraocular gas in the treatment of retinal detachment in eyes with severe proliferative vitreoretinopathy. The primary outcome measures were macular reattachment and postoperative visual acuity. The secondary outcome measures were to assess the potential complications of the two forms of intraocular tamponade.20 A total of 404 patients were recruited and 101 were in the initial randomisation for silicone oil or SF6 as the intraocular tamponade. The superiority of silicone oil over SF6 in retinal detachment associated with severe PVR, in terms of visual

outcome and incidence of complications, was apparent within two years of the study.21 However, at this point C3F8 was shown to have longer and more effective intraocular tamponade than SF6. It was therefore introduced to begin a second phase in the study22 in which 265 eyes were recruited. The most important conclusion was that C3F8 and silicone oil showed no difference in posterior pole reattachment rate or visual acuity at the last follow up examination.23 No differences were found between patients who had previous vitrectomy at randomisation and those who had not. However, if multiple surgeries were necessary to reattach the macula, the final visual acuity was likely to be worse.24

After these main outcome measures of anatomic and functional success had been analysed, various secondary outcome measures, mainly the occurrence of complications, were assessed. Chronically raised intraocular pressure was found to be more in eyes with silicone oil. This could be reduced by the presence of an inferior peripheral iridectomy and oil removal. A relatively high incidence of hypotony was an unexpected finding. This was more likely to occur in C3F8 eyes and eyes in which the retina was still detached. Risk factors for hypotony are preoperative hypotony, anterior diffuse contraction of the retina, rubeosis and large retinal breaks. Hypotony was also correlated with poor postoperative vision.25

Almost a third of the study patients had a relaxing retinotomy at the time of surgery. Most of these patients were found to have had a worse PVR grading before surgery with more diffuse anterior traction and subretinal fibrosis. For patients who had had a previous vitrectomy, the retinotomy did not affect their outcome. However, patients who had not had a prior vitrectomy did less well after retinotomy, especially if C3F8 was used for the tamponade.26

Anterior proliferative vitreoretinopathy was redefined during the Silicone Study, as anterior vitreous traction seemed to have an important prognostic value for surgical outcome. Patients with posterior traction only had better postoperative visual acuity and better reattachment rates. For anterior PVR (>D1) there was a poorer visual prognosis and more hypotony, especially in the C3F8 eyes.27

The removal of the silicone oil from eyes during the study was at the surgeon’s discretion, which introduced selection bias, as eyes having oil removed were more likely to have an attached retina. A matched pair analysis was performed to control for this bias, which showed that oil-removed eyes tended to have a greater improvement in visual acuity compared to oil-retained eyes. Oil-removed eyes also had a lower incidence of keratopathy.28 Risk factors for keratopathy after vitrectomy were aphakia or pseudophakia and rubeosis preoperatively. Postoperatively high aqueous flare, number of reoperations and silicone oil-corneal touch were risk factors.29 The preoperative risk factors for

postoperative macular pucker in an attached retina were pseudophakia or aphakia, large (inferior) retinal breaks and iris new vessels.30

In the final Silicone Study Report with long-term follow up, the main findings were that success at the first surgery was most important for attaining a good visual result and if the macula was still attached at three years it was likely to stay attached.31

Comment

Although there was little benefit in retinal reattachment rate with silicone oil over C3F8 gas, silicone oil does offer an indefinitely longer tamponade, which can be useful. Whilst both techniques will work if all the breaks are adequately sealed, silicone oil does have the advantage of offering a period of stability as a result of its indefinite tamponade. The longer term complications need to be considered.

Question

What is the best intraocular tamponade for treating giant retinal tears?

The evidence

Whilst giant retinal tears have been shown to be successfully repaired using vitrectomy and silicone oil, a prospective trial by Batman and Cekic32 involving 47 patients with giant tears associated with PVR equally randomised between the two groups, demonstrated that C3F8 and silicone oil have similar outcomes (attachment rates, visual acuity 5/200 or better and complication rates) at five years follow up.

Question

Does removing the corneal epithelium peroperatively in order to improve visibility of the retina have any long-term effects?

The evidence

Removing oedematous corneal epithelium provides a straightforward solution to poor preoperative retinal visibility but it has been questioned whether this has any effect on the corneal epithelium postoperatively. Hung33 measured corneal sensation using an esthesiometer preoperatively and at several time internals postoperatively in a group of 26 patients randomised to have the epithelium

either removed or left intact peroperatively. In the non-removal group, five of 14 patients had slightly reduced sensation and this had returned to normal in all patients by one week postoperatively. This was compared with 10 of 12 patients having reduced sensation postoperatively in the removal group, and this took one month to recover in seven patients and three months to recover in the remaining three patients. This should be borne in mind when allowing patients to return to contact lens wear postoperatively.

Comment

Usually the corneal epithelium is left intact unless the surgeon is forced to remove it due to the poor operative visibility.

Question

Do postoperative steroids affect clinical outcome?

The evidence

Postoperatively, many surgeons advocate the use of sub-conjunctival steroids with or without antibiotics, a course of topical antibiotics and steroids, and a period of posturing in an appropriate position to tamponade the breaks if necessary. The use of antibiotic and steroid makes good clinical sense, but the evidence for their benefit has never been subjected to a clinical trial. In the early 1970s, choroidal detachment was a common postoperative problem, and Burton et al. conducted a prospective trial to evaluate the effect of sub-conjunctival depot steroid on its incidence.34 They reported no significant difference in the incidence of choroidal detachment between the groups treated (44%) and untreated (38%) with depot steroid and also found no difference in the incidence of postoperative infection.

Comment

There is no evidence of either benefit or harm from depot steroid injections. In current practice, their use is not widespread.

Question

Should physical activity be restricted following detachment surgery?

The evidence

The lack of need for restriction in physical activity was demonstrated by a randomised controlled trial by Bovino and Marcus in 1984.35 Following scleral buckling surgery, 108 patients were divided into two groups, one advised to avoid bending, lifting, straining at stool, driving, sexual activity, lawn-mowing, gardening, athletics and returning to work for six weeks postoperatively, and the other allowed to resume normal activity immediately. No difference in the redetachment, reoperation and final reattachment rates was found at six months or in final visual acuity at one year.

Comment

This study confirms that physical activity need not be avoided postoperatively. This seems logical since in rapid eye movement sleep, unavoidable forces are applied to the eye.

Question

Are there proven methods to control postoperative pain?

The evidence

The use of analgesics postoperatively is both essential and commonplace. Non-steroidal anti-inflammatory drugs (NSAIDs) are likely to be beneficial in scleral buckling surgery due to their already proven effect on scleritis. A randomised placebo controlled trial of the use of oral indometacin by Sadiq et al.36 studied 28 patients undergoing scleral buckling surgery. Patients receiving indometacin 100 mg by suppository and 50 mg orally twice daily for 10 days had significantly lower pain scores measured at both three and 10 days postoperatively.

For postoperative analgesia the use of a regional block in addition to general anaesthesia has been shown to be beneficial and is gaining popularity. Duker et al.37 studied the effect of retrobulbar bupivacaine injection in a prospective, randomised, double-masked trial of 50 patients. Only 12% of the group who received bupivacaine required parenteral analgesic in the first 24 hours following surgery, compared with 72% of those who received placebo. This effect was significant up to 48 hours postoperatively in a similar study by Gottfredsdottir et al.38 Bourke et al.39 found a similar benefit with bupivacaine administered in a peribulbar/subtenon injection in scleral buckling surgery. Chung et al.40 reported 28 patients undergoing general anaesthesia for retinal detachment, who were randomly assigned to receive a retrobulbar block or nothing. The operative procedure was

not reported but was presumably a cryotherapy and scleral explant procedure. Postoperative pain score and speed of recovery of anaesthesia were both significantly better in those who received a retrobulbar block.

Comment

Indometacin is not much used in current practice, having been replaced by more modern NSAIDS. Use of subtenon bupivacaine 0·5% administered at the start of all vitrectomy and scleral buckling procedures is common practice.

Question

Can entry-site breaks be prevented in vitrectomy surgery?

The evidence

Entry-site breaks in the retina are reported to occur in 5–10% of vitrectomy operations. Territo et al.41 showed that use of a cannulated sclerostomy system can reduce this from 7·7% in the non-cannulated group to 1% in the cannulated group.

Question

Can the incidence of postoperative cystoid macular oedema be reduced?

The evidence

Cystoid macular oedema has been reported to occur in 30–43% of patients following retinal detachment surgery. It may result from a number of factors theoretically, including vitreomacular traction, inflammation and hypotony, although no one factor has been proven. However, the randomised trial of Miyake et al.42 involving 124 patients randomised to receive topical indometacin or placebo following retinal detachment surgery suggests inflammation is causative. Topical indometacin, which reduces inflammation, reduced the incidence and severity of cystoid macular oedema in patients treated in the early (four to six weeks) but not the late (12 weeks) postoperative period. The presence of cystoid macular oedema was associated with reduced visual acuity.

Comment

Cystoid macular degeneration is perhaps an underreported complication, but this trial does show that there is

further benefit to the use of NSAIDs in addition to their analgesic properties.

Question

Can ocular motility problems be avoided after retinal detachment surgery?

The evidence

After scleral buckling surgery, diplopia is a common complaint. It was thought to be caused either by the presence of an explant or the manipulation of the rectus muscles during the procedure. A trial by Mester et al.43 compared 60 patients undergoing scleral buckling surgery, randomised to receive either a permanent silicone sponge explant or a temporary, removable balloon buckle. Orthoptic evaluation revealed no difference between the ocular motility findings between the groups at one week postoperatively (i.e. immediately after the balloon was removed), but significantly better ocular motility in the balloon-treated group at four weeks and 26 weeks postoperatively.

Comment

This study supports the view that permanent explants cause ocular motility problems, and this is further borne out by the common experience that the ocular motility symptoms improve when an explant is removed.

Implications for research

Over the past 80 years, rhegmatogenous retinal detachment has evolved from being an untreatable condition to being one with an excellent prognosis for surgical outcome. Randomised clinical trials have been crucial in evaluation of the various components of possible treatment and has helped to refine techniques. The major questions remaining to be answered are those of how to preserve visual function following macular retinal detachment and how to improve the outcome of retinal detachments complicated by PVR.

Implications for practice

The large proportion of rhegmatogenous retinal detachments require surgical repair. However, a conservative approach may be indicated if the detachment is inferior and long standing (implied by a pigmented tide-mark

at the demarcation of detached and attached retina), or conversely if a successful surgical outcome is considered unlikely due to advanced PVR. However, this rationale is based on common practice and experience rather than any scientific evidence.

An external approach with cryotherapy or laser retinopexy and scleral explant is indicated when the retinal breaks are anteriorly placed, can be clearly visualised, and/or there is no posterior vitreous detachment. The subretinal fluid may be drained transclerally. Other surgical approaches are pars plana vitrectomy or pneumatic retinopexy.

Drainage of subretinal fluid is indicated if there is excessive subretinal fluid to allow retinopexy, to create intraocular space if a large explant or encirclement is required, and tends to be associated with increased success in the treatment of inferior breaks.

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