Primary Retinal Detachment: A Review of Mechanisms, Management, and Controversies
BY REZA IRANMANESH, MD WILLIAM M. SCHIFF, MD
Retinal detachment occurs when the neurosensory retina separates from the underlying retinal pigment epithelium (RPE). In a rhegmatogenous retinal detachment (RRD), liquefied vitreous gains access to the subretinal space through a full-thickness retinal break. Retinal detachment occurs with an estimated frequency of 1/10000 people per year.1 Roughly 95% of all RRD are ultimately repaired;2 however, it remains a serious disorder that can lead to significant loss of vision or blindness.
Repair of retinal detachment prior to the 20th century was generally unsuccessful because the pathophysiology of the disease was not well understood. In 1918, Gonin was the first to demonstrate the importance of localizing and sealing retinal breaks through transscleral cautery, a procedure termed ignipuncture.3 Scleral buckling techniques, introduced by Custodis4 and later refined by Schepens among others, have revolutionized repair of RRDs, with success rates reported as high as 80%–90%.5-7 More recently, alternative techniques such as pars plana vitrectomy (PPV)and pneumatic retinopexy have been utilized to treat RRD.8,9 Advances in surgical instrumentation, intraoperative visualization, and the use of short-term intraoperative tamponades have facilitated the surgical management of RRD by vitrectomy.
MECHANISM OF RHEGMATOGENOUS RETINAL DETACHMENT
There are 4 major categories of retinal detachment: rhegmatogenous, tractional, combined tractional and rhegmatogenous, and exudative. A RRD develops from a full- thickness retinal break. This type of retinal detachment is the most common, and is the category that will be discussed in this review.
Acute posterior vitreous separation often precedes the development of RRD. Aging causes syneresis of the vitreous gel. Large liquefied pockets of gel, known as lacunae, form.10 With time, the liquefied gel passes into the subhyaloid space creating a true posterior vitreous separation.11
As the posterior vitreous separates from the inner retina, tears can develop, especially in regions in which the cortical gel was or remains firmly adherent. Typical flap-shaped horseshoe tears are the result of excessive and abnormal traction often occurring at posterior insertions of the vitreous base and regions of lattice degeneration. A RRD often develops when persistent vitreous, adherent to the anterior flap of a tear, causes traction allowing liquid vitreous access to the subretinal space. Eye movement, causing internal eddy currents, may facilitate this process.
PREDISPOSING FACTORS TO RETINAL DETACHMENT AND PROPHYLAXIS
Asymptomatic retinal breaks may predispose patients to retinal detachment. The indications for prophylactic retinopexy of these lesions are controversial. Given that the prevalence of retinal breaks was found to be 83 times that of retinal detachment, it is clear that not every break leads to retinal detachment.12 Thus, prophylactic treatment of retinal breaks should be selective and is generally recommended for symptomatic tears13 and horseshoe tears with persistent vitreous traction.14 Thirty percent to 50% of acute, symptomatic horseshoe tears have been found to result in retinal detachment, and prophylactic treatment reduces the frequency to 5%.13,15
Several peripheral retinal lesions are characterized by anomalous vitreoretinal adhesions, and therefore, are predisposed to full-thickness retinal breaks in the setting of PVD. Ora bays, meridional folds and complexes, cystic retinal tufts, and lattice degeneration represent sites of abnormal vitreoretinal adhesions.
Lattice lesions can vary in shape, appearance, and location. Retinal thinning and degeneration with atrophic hole formation, liquefaction of the overlying vitreous, and firm adhesions of the vitreous at the margin of these lesions have been identified in histopathologic studies.14,17-21 The condition is bilateral in 45% of cases,16 and it occurs more frequently in myopic eyes. Approximately 30% of patients with retinal detachment also have lattice degeneration. However, the prevalence of lattice is high in the general population, 7%–8% in clinical series, and 11%–16% in autopsy series. For lattice lesions without retinal breaks, the risk of retinal detachment is <1%, and prophylactic therapy is generally not recommended. In addition, prophylactic therapy for atrophic holes in lattice is usually not indicated, but considerations, such as history of detachment in the fellow eye, may influence the decision. Clinicians generally agree that lattice lesions with tractional breaks should be treated prophylactically, even if the patient is asymptomatic.
Nonphakic eyes are at an increased risk for retinal detachment in their lifetime when compared with phakic eyes. Approximately 40% of retinal detachments occur in the nonphakic eye.22 The incidence of retinal detachment is 0.01% in the general population, 2%–5% following intracapsular cataract extraction, and 0%–1.4% following extracapsular cataract extraction.22-25 Crystalline lens extraction is associated with an increase in the rate of vitreous liquefaction and it is possible that anterior movement of the vitreous contributes to subsequent PVD and retinal break formation.26,27
TYPES OF SURGICAL INTERVENTION
Scleral buckling is often considered the gold standard for retinal reattachment surgery, and currently reported success rates range between 82%–91% for a single operation.28-30 Results following scleral buckling appear to be somewhat less successful in the pseudophakic/aphakic eye and in those detachments in which a causative break is not identified.31 This may be due to the small slit-like breaks often found in the nonphakic eye. Additionally, capsular opacification and fibrosis in the pseudophakic eye can obscure the view of the peripheral fundus, rendering identification of causative breaks challenging.
Machemer initially introduced PPV in 1970.8 At the time of surgery, the underlying source of vitreoretinal traction can be relieved internally. Once the retina is flattened, either by internal drainage through a posterior retinotomy or through an existing peripheral retinal break, the breaks can then be treated directly with endolaser, avoiding excessive and extensive cryopexy. Initially, primary vitrectomy (with or without scleral buckling) was used in the management of retinal detachments and was thought to be high-risk for failure with traditional scleral buckling techniques. These cases included giant retinal tears, posterior retinal breaks, retinal detachments with significant vitreous hemorrhage, and proliferative vitreoretinopathy (PVR). Recently, there is an increasing trend towards utilizing primary vitrectomy for the repair of routine retinal detachments.32
Advantages of PPV over scleral buckling techniques alone include the enhanced capability of identifying small, previously unrecognized retinal breaks. Using a panoramic viewing system and perfluorocarbon liquids, slit-like breaks are more readily identified, with the Schlieren phenomenon often localizing the site.33 Furthermore, minimal refractive changes following PPV without scleral buckling can be expected.
Pneumatic retinopexy was introduced in the mid 1980s as an outpatient procedure to treat selected retinal detachments.9 Initially, the technique was recommended when the detachment was caused by a single retinal break, no larger than 1 clock hour and located within the superior 8 hours of the fundus, or by a group of small retinal breaks located within 1 clock hour, in the absence of grade C or D PVR and uncontrolled glaucoma.34 Perfuoropropane (C3F8) and sulfur hexafluoride (SF6) are the most commonly used gases and the technique combines intravitreal injection in combination with transconjunctival cryotherapy or laser photocoagulation of retinal tears.
These 3 surgical techniques each have their advantages. When one reviews the literature it is not surprising that there is significant controversy regarding the ideal procedure for primary retinal detachment. In some studies, it appears that scleral buckling and primary vitrectomy are comparable in regards to anatomic and visual success.35 One retrospective study found retinal reattachment rates of 91% for both groups without significant differences in postoperative visual acuity (VA).35 Others have reported higher rates of anatomic success with primary vitrectomy compared to scleral buckling in pseudophakic retinal detachment.
Some surgeons may prefer 1 technique to another due to their own experiences and training preferences. Many choose buckling over vitrectomy in the younger phakic patient to avoid cataract formation. Scleral bucking, in many instances, is an external procedure, avoiding the well-recognized complications of intraocular surgery. However, scleral buckling can induce myopia, diplopia, and can be associated with significant complications, especially when external drainage of subretinal fluid is performed. Performing segmental buckling and nondrainage procedures can minimize many of the complications associated with buckling procedures.
Pneumatic retinopexy is advantageous because it is technically less difficult and can be performed in the office setting. In 1989, a randomized controlled trial compared pneumatic retinopexy to scleral buckling and found a single-operation success rate of 73% and 82%, respectively.34 Hilton and colleagues described a comprehensive literature review and reported a single-operation anatomic success rate of 80%.36 Although the use of pneumatic retinopexy in phakic eyes is fairly well accepted, its use in the pseudophakic or aphakic eye is more controversial. Primary retinal reattachment was achieved in 67% of pseudophakic retinal detachments treated with pneumatic retinopexy.31,34 However, because most eyes that initially failed pneumatic retinopexy ultimately reattached with fairly good vision, the Retinal Detachment Study Group recommended the use of pneumatic retinopexy independent of lens status.31,34 Others have also found that initial failure of pneumatic retinopexy does not adversely affect the visual outcome.37,38 Despite these results, there are those who are skeptical regarding the use of pneumatic retinopexy in nonideal cases.39
Ultimately, without a randomized clinical trial comparing the 3 modalities, and in numerous clinical scenarios, there will never be a definitive answer as to which procedure is superior. For most surgeons, the decision as to what procedure to use for primary retinal detachment will depend on the individual clinical situation combined with each surgeon's biases, experience, and comfort level. With vitrectomy and pneumatic retinopexy as accepted options for repair of the routine retinal detachment, there is less exposure to scleral buckling for vitreoretinal surgeons in training. Younger surgeons may ultimately prefer these techniques to conventional scleral buckling. In fact, 1 study showed that the popularity of pneumatic retinopexy was inversely proportional to the number of years that the specialist had been in practice.40
Although there is no proven algorithm for repair of primary RRD, it is our preference to perform primary scleral buckling in the phakic patient with well-recognized pathology. We prefer segmental, nondrainage procedures. We perform encircling buckles in eyes with global pathology, and the nonphakic eye with larger detachments with limited peripheral visualization.
1. An image of a posterior retinal break where a primary vitrectomy is generally
IMAGES COURTESY OF KEVIN LANGTON, CRA, COLUMBIA OPHTHALMOLOGY PHOTOGRAPHY DEPARTMENT
|Figure 2. An image of a giant retinal tear where a primary vitrectomy is generally utilized.|
Primary vitrectomy (with or without an encircling scleral buckle) is generally utilized in those eyes with vitreous hemorrhage, posterior retinal breaks (Figure 1), giant retinal tears (Figure 2), cataract or pseudophakic status, and established PVR. In eyes with diffuse pathology, often requiring extensive retinopexy in multiple quadrants, we feel vitrectomy may be a more ideal approach. By applying localized and focused retinopexy, and avoiding external drainage in the setting of a congested choroid, vitrectomy is extremely effective and safe. We often use a 3.5-mm solid, silicone-encircling element to support the posterior vitreous base in pseudophakic eyes, those with PVR, or those eyes with significant global peripheral pathology. However, if primary vitrectomy is being performed in a phakic eye with more limited pathology, such as a patient with a posterior retinal break, then scleral buckling is generally not required. In addition, we shave the vitreous base 360° under panoramic viewing in most patients. The retina is flattened internally utilizing perfluorocarbon liquids. Postoperative positioning is generally recommended for 1–2 weeks.
In our practice, we utilize pneumatic retinopexy, most often in only the ideal cases. These include phakic patients with isolated pathology and tears in the superior quadrants. Cryopexy of the retinal break with subsequent injection of 0.3 cc of pure C2F6 gas, or injection followed by indirect laser retinopexy followed by a flattening of the retina should be performed. In eyes that have failed pneumatic retinopexy, repair with subsequent buckling can often be more challenging for several reasons. Visualization may be impaired due to residual gas or fish eggs and often new breaks, as a result of the gas injection, can convert a routine detachment into a more complex case. Ultimately, vitrectomy with scleral buckling may be preferable for repair.
In spite of improvements in surgical techniques and outcomes in the repair of primary retinal detachment over the past decades, the development of PVR remains a major obstacle to successful repair. Proliferative vitreoretinopathy is characterized by the formation of fibrous membranes along the periretinal surface, often causing redetachment of the retina. This process occurs in approximately 5%–10% of all rhegmatogenous retinal detachments and is responsible for the majority of surgical failures.
Several studies have identified clinical risk factors that are associated with the development of PVR. Proliferative vitreoretinopathy is more often seen in patients with large or giant retinal tears, vitreous hemorrhage, choroidal detachment, failed retinal reattachment procedures, extensive cryopexy, and retinal detachments involving 2 or more quadrants.41,42 Due to the complexity of PVR surgery and ultimately the disappointing visual outcomes, adequate prophylaxis of PVR remains an important goal. Currently, there is great interest in developing viable pharmacologic therapies in the hope of preventing this intraocular response.
Some papers describing therapies composed of a combination of steroids, antineoplastic agents, and/or other antiproliferative agents have shown encouraging results for PVR prophylaxis. A randomized clinical trial combining low-molecular weight heparin (LMWH) with 5-fluorouracil (5-FU) as adjuvant therapy for PVR reported a statistically significant lower incidence of postoperative PVR in the LMWH/5-FU group (12.6%) vs. the placebo group (26.4%). The final VA, however, was not significantly different between the 2 groups.43 Additionally, others have evaluated treatment for established PVR. Williams and colleagues randomized 62 eyes with severe (class C3 or D) PVR to infusion fluid composed of either balanced salt solution or of balanced salt solution with added heparin and dexamethasone.44 The authors found that there was a trend towards fewer cases of recurrent PVR in the heparin/dexamethasone group although this did not approach statistical significance.
Despite the initial enthusiasm regarding these reports, an agent that truly prevents the development of PVR and improves visual outcomes is not yet on the horizon. Improvements in current management of PVR have been primarily surgical in nature. Controlling postoperative inflammation, performing focused retinopexy without extensive cryopexy, and successful reattachment of the retina is the best prophylaxis for PVR.
TIMING OF INTERVENTION
Many authors have looked at duration of macular detachment and its effects on visual prognosis. Yang and colleagues reviewed 93 patients retrospectively and found that a final vision of 20/50 or better was noted in 53.6% of patients with macular detachment <7 days duration, compared with 29.7% of patients with a macular detachment of >7 days.45 Other investigators have had similar findings confirming that surgery after 1–2 weeks of macula-off retinal detachment yields poorer visual results.46, 47 Ross and Kozy evaluated patients with early macula-off detachments and subdivided them into 3 groups based on duration of macular detachment (1–2 days, 3–4 days, and 5–7 days). They found that there was no statistical difference in the visual recovery between the 3 groups.48 This study suggests that surgery in macula-off detachments may be delayed for a relatively short period without compromising visual outcomes.
Patients with macula-on retinal detachments risk the progression to macular involvement if surgery is delayed. In general, these cases are more urgent. Most vitreoretinal surgeons prefer to operate prior to progression. If delay is anticipated due to factors such as operating room or surgeon availability and/or medical issues, strict bedrest with double patching often prevents and delays progression of the detachment into the macula. In 1992, Hartz and colleagues showed that delaying surgery for a short time did not lead to worse visual outcomes regardless of the status of the macula.49
As more technical advances occur in the field of vitreoretinal surgery, there will also be more controversies regarding the best approaches in the management of primary retinal detachment. Fortunately, current success rates for retinal reattachment are high regardless of the technique utilized. Frontiers that need exploring are numerous. Mechanisms and therapies that reduce the postoperative risk of PVR, enhance visual outcomes, and improve postoperative positioning and quality of life issues in the retinal detachment patient are paramount.
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Reza Iranmanesh, MD is a retina fellow at the Department of Ophthalmology, Columbia University College of Physicians and Surgeons, Edward S. Harkness Eye Institute in New York, NY. William M. Schiff, MD, is assistant clinical professor of ophthalmology at the Department of Ophthalmology, Columbia University College of Physicians and Surgeons, Edward S. Harkness Eye Institute in New York, NY. Neither author has any financial interest in the information reported in this article. Dr. Iranmanesh can be reached at firstname.lastname@example.org and Dr. Schiff can be reached at email@example.com.