Establishing the Diagnosis

The differential diagnosis of rhegmatogenous retinal detachment includes secondary (nonrhegmatogenous) retinal detachment and other entities that may simulate a retinal detachment. Nonrhegmatogenous detachments are categorized as exudative (serous) and tractional detachments. Conditions that may be mistaken for retinal detachment include retinoschisis, choroidal detachment or tumors, and vitreous membranes. Sometimes benign findings in the peripheral retina are mistaken for retinal breaks. The most prominent feature of the fundus is the optic nerve head or disc, the only place in the human body that affords a direct view of a tract of the central nervous system. The foveola, the functional center of the fundus, is located in the center of the fovea, which has a diameter of about 5°. The macula is centered on the fovea and has a diameter of about 17°. The multiple branches of the central retinal artery are readily identifi ed by their bright red color and relatively narrow caliber. The multiple tributaries of the central retinal vein are recognized by their dark red color and relatively wider caliber. In a darkly pigmented fundus, the choroidal vessels in the posterior pole can be obscured from view, but in an eye with minimal pigment, they are readily visible. The venous tributaries of the choroid that make up the vortex veins are usually easily seen. The most prominent features of the choroidal venous system are the vortex ampullae, of which there are usually four (but sometimes more). They are located approximately in the 1-, 5-, 7-, and 11-o’clock meridians, just posterior to the equator. The horizontal meridians are usually identifiable by their radially oriented, long posterior ciliary nerves, and infrequently the long posterior ciliary artery can be seen adjacent to the nerve. The nerve is relatively broad and has a yellow color, and the artery is identifiable by its red color. The artery is usually inferior to the nerve temporally, and superior to it nasally (Figure 5–1).

Evaluation and Management

Evaluation of a patient for retinal detachment includes a thorough history and a complete ocular exam, including measurement of visual acuity, external examination, ocular motility testing, testing of pupillary reactions, anterior-segment biomicroscopy, tonometry, and binocular indirect ophthalmoscopy with scleral depression. Posterior-segment biomicroscopy, perimetry, and ultrasonography are also sometimes required. Rhegmatogenous retinal detachment is a diagnosis generally made by clinical examination of the retina alone, but a full history, ocular examination, and sometimes selected ancillary tests are also important parts of the evaluation (Figure 4–1). The symptoms of retinal detachment include fl ashes of light, new floaters, visual Field defect, decreased visual acuity, metamorphopsia, and rarely, defective color vision. The perception of light fl ashes, or photopsia, is due to the production of phosphenes by pathophysiologic stimulation of the retina. The retina is activated by light but is also capable of responding to mechanical disturbances. In fact, the most common cause of light fl ashes is posterior vitreous detachment. As the vitreous separates from the retinal surface, the retina is disturbed mechanically, stimulating a sensation of light. This perception is more marked if there are focal vitreoretinal adhesions. Generally, vitreous separation is benign and may almost be regarded as normal in the senescent eye. In approximately 12% of symptomatic posterior vitreous detachments, however, a careful search of the periphery reveals a tear of the retina. If the fl ashes are associated with floaters, it is wise to assume that a retinal tear exists, until proved otherwise. These symptoms demand a prompt and careful examination of the periphery with binocular indirect ophthalmoscopy and scleral indentation. The patient’s localization of the photopsia is of little value in predicting the location of the vitreoretinal pathology. If no breaks are evident in the first examination after symptomatic vitreous detachment, they rarely appear at a later date. If there is no associated hemorrhage or other pathologic condition, the patient needs counseling only. However, if pigment or blood is detected in the vitreous, a follow-up examination is often required. It is prudent to forewarn patients about the symptoms of retinal detachment. Flashes alone or floaters alone are less significant than if they occur together, in which case they are more likely to be associated with a retinal break.

Pathogenesis, Epidemiology, and Natural Course of Retinal Detachment

Retinal detachment does not result from a single, specific disease; rather, numerous disease processes can result in the presence of subretinal fluid. The three general categories of retinal detachments are termed rhegmatogenous, exudative, and tractional. Rhegmatogenous detachments are sometimes referred to as primary detachments, while both exudative and tractional detachments are called secondary or nonrhegmatogenous detachments. The three types of retinal detachments are not mutually exclusive. For example, detachments associated with proliferative vitreoretinopathy or proliferative diabetic retinopathy may exhibit both rhegmatogenous and tractional features. However, excluding the section on differential diagnosis in Chapter 5, the scope of this book is limited to rhegmatogenous retinal detachments. Accordingly, throughout the book, the term retinal detachment refers to the rhegmatogenous type, unless another type is specifically mentioned. Rhegmatogenous detachments (from the Greek rhegma, meaning rent, rupture, or fissure) are the most common form of retinal detachment. They are caused by a break in the retina through which fluid passes from the vitreous cavity into the subretinal space. The responsible break(s) can be identified preoperatively in more than 90% of cases, but occasionally the presence of a minute, unseen break must be assumed. Exudative detachments, also called serous detachments, are due to an associated problem that produces subretinal fluid without a retinal break. This underlying problem usually involves the choroid as a tumor or an inflammatory disorder. Tractional detachments occur when pathologic vitreoretinal adhesions or membranes mechanically pull the retina away from the pigment epithelium without a retinal break. The most common causes include proliferative diabetic retinopathy, cicatricial retinopathy of prematurity, proliferative sickle retinopathy, and penetrating trauma. Retinal breaks may subsequently develop, resulting in a combined tractional and rhegmatogenous detachment. The essential requirements for a rhegmatogenous retinal detachment include a retinal break and low-viscosity vitreous liquids capable of passing through the break into the subretinal space. Vitreous changes usually precede development of important defects in the retina. The usual pathologic sequence causing retinal detachment is vitreous liquefaction followed by a posterior vitreous detachment (PVD) that causes traction at the site of significant vitreoretinal adhesion with a subsequent retinal tear. Fluids from the vitreous cavity then pass through the tear into the subretinal space (Figure 2–1), augmented by currents within the vitreous cavity caused by rotary eye movements. Although a total PVD is usually seen, many detachments occur with partial vitreous detachment, and evidence of posterior vitreous detachment may not be seen.

Selection of Surgery for “Routine” Retinal Detachment

Most rhegmatogenous retinal detachments are blinding disorders unless they are successfully repaired. They were regarded as incurable until the seminal work of Jules Gonin in the 1920s, when an anatomical success rate approaching 50% was first described (see Chapter 1). Anatomical results for routine retinal detachments slowly improved through several decades, reaching the current 85%–90% single-operation success figure for scleral buckling by the 1980s. Unfortunately, a similar improvement in visual results has not occurred because of the profound influence of preoperative macular detachment. Scleral buckling, once the sole standard of care for uncomplicated cases, has become much less popular worldwide with the development of alternative options starting in the mid 1980s. The most enduring of these are pneumatic retinopexy (PR) (described in Chapter 8) and vitrectomy (described in Chapter 9). Vitrectomy was originally reserved for complicated detachments but became popular for more routine cases as experience and equipment improved. Today, particularly in the United States, scleral buckling, PR, and vitrectomy are standards of care that are widely employed in the management of “routine” or “uncomplicated” retinal detachment, but how frequently each is used varies among different demographic groups. For instance, the popularity of PR varies by geographical location and scleral buckling appears less popular in the hands of relatively young vitreoretinal specialists. It can be useful to discuss objective clinical criteria that may favor one technique over another. Demarcation, scleral buckling, PR, vitrectomy, and vitrectomy plus scleral buckling have relative indications and contraindications (Table 10–1), as well as limitations and complications. In this brief chapter, clinical factors that may influence the choice of one technique over another, for the types of cases in which scleral buckling, PR, and/or vitrectomy are neither mandatory nor contraindicated, are discussed. However, it appears clear that we will never universally agree on the “best” operation for a given case, just as a single ice cream flavor will never be favored by all. There are several relatively common types of uncomplicated retinal detachments (Table 10–2), as well as numerous variables associated with all of them (Table 10–3). Management of retinal detachments with each specific technique is described in Chapters 7, 8, and 9.

Scleral Buckling

Inflammatory detachments are usually treated medically. Some serous detachments, such as choroidal hemangioma, respond to photocoagulation or photodynamic therapy (PDT). Selected traction detachments, such as diabetic or post-traumatic detachments, may be cured with intraocular microsurgery (vitrectomy). Radiation therapy is often used for detachments secondary to metastatic tumors. This chapter is confined to the surgical management of rhegmatogenous detachments with scleral buckling. Alternative methods of repair are discussed in Chapters 8 and 9, and the three techniques are compared in Chapter 10. Controversy exists regarding the details of the surgical technique, but surgeons generally agree on the three basic steps in closing retinal breaks and reattaching the retina:… 1. Conducting thorough preoperative and intraoperative 1. examinations with the goal of locating all retinal breaks and assessing any vitreous traction on the retina. 2. Creating a controlled injury to the retinal pigment epithelium and retina to produce a chorioretinal adhesion surrounding all retinal breaks so that intravitreal fluid can no longer reach the subretinal space. 3. Employing an appropriate technique, such as scleral buckling and/or intravitreal gas, to approximate the retinal breaks to the underlying treated retinal pigment epithelium…. If the surgeon follows these basics and applies modern surgical techniques, retinal reattachment may be expected following a single operation in more than 85% of uncomplicated primary detachments, and in more than 95% following additional procedures. The traditional scleral buckle has served very well since the 1950’s. However, more recent developments have produced a more comprehensive menu for retinal reattachment surgery from which the surgeon may select the appropriate procedure for each case. By the turn of the millennium, surveys had demonstrated that scleral buckling alone was no longer the most popular means of repairing uncomplicated primary retinal detachments. Still, it is a valuable technique that is indicated in many situations. Temporary scleral buckling can be performed with scleral infolding, gelatin, or orbital balloon. The term scleral buckling without a qualifying adjective is generally recognized as referring to a “permanent” scleral buckle with the implantation of a foreign material usually made of silicone.

Vitrectomy for Retinal Detachment

Following the introduction of closed vitrectomy techniques by Robert Machemer in the early 1970s, complicated retinal detachments became one of the important indications for vitreous surgery. Most of these were due to proliferative diabetic retinopathy (PDR) or to proliferative vitreoretinopathy (PVR), frequently following failure of routine scleral buckling procedures. As experience in vitreoretinal surgery expanded, the advantages of these techniques in the management of more routine types of retinal detachment became apparent. The popularity of vitrectomy for primary retinal detachments continues to grow, particularly with regard to pseudophakic cases. Indications for performing a vitrectomy rather than a scleral buckle or a pneumatic retinopexy are summarized in Chapter 10. Virtually all authorities note that a vitrectomy is required (along with a broad scleral buckle) in eyes with severe PVR, and the technique is also clearly indicated for cases due to PDR, detachments associated with major vitreous hemorrhage or scarring from penetrating trauma, and those with giant retinal tears. On the other hand, few would suggest a vitrectomy to repair a very shallow and small retinal detachment due to a single break that could be easily closed with a scleral buckle or pneumatic procedure. Between these two extremes, indications remain a matter of personal choice of the surgeon, and they are influenced by his or her training and experiences with a variety of techniques. Most surveys demonstrate a growing popularity of vitrectomy for an increasing percentage of cases. The goals of vitrectomy for retinal detachment are to… 1. Remove axial opacities such a 1. s vitreous hemorrhage or debris. 2. Eliminate vitreoretinal, epiretinal, or subretinal traction. 3. Identify and treat all retinal breaks. 4. Internally reattach the retina. 5. Facilitate placement of a large intraocular tamponade. 6. Avoid complications associated with scleral buckling surgery…. The usual sequence of events includes removal of vitreous gel and epiretinal membranes, identification of retinal breaks, internal removal of subretinal fluid, laser therapy to all responsible breaks and areas of significant vitreoretinal degeneration, and placement of an internal tamponade with gas or silicone oil. Vitrectomy is frequently combined with placement of a scleral buckle.

Prevention of Retinal Detachment

Retinal detachment is an uncommon disease, affecting approximately 1 in 10,000 people in the general population per year. However, the incidence of retinal breaks is relatively high, affecting 5% to 7% of the population. Obviously, many retinal breaks have minimal, if any, risk for the possible development of a retinal detachment. This includes macular holes that occur as a degenerative process, and asymptomatic, small, round atrophic holes near the ora serrata. However, equatorial horseshoe tears with relevant symptoms progress to retinal detachment in most cases. Probably all surgeons would agree that a large horseshoe tear near the equator in the superior temporal quadrant, with new-onset symptoms of fl ashes and fl oaters and associated vitreous hemorrhage, should be treated prophylactically to avoid retinal detachment. In contrast, most would not advise treatment of a small, round atrophic hole near the inferior ora serrata in an asymptomatic patient with no history of prior detachment. Between these two obvious examples lies a broad spectrum of retinal breaks for which the surgeon must exercise judgment about instituting prophylactic treatment. Most of the breaks reported in surveys of asymptomatic patients or in autopsy series are of the atrophic type, and only a small proportion are horseshoe tears. Although there are no specific rules for the selection of patients for treatment, and each case has to be judged on its own characteristics, the application of evidencebased medicine to this topic has modified the opinions of many regarding the genuine value of prophylactic therapy for most retinal breaks. The American Academy of Ophthalmology has used this approach in developing a Preferred Practice Pattern (PPP) entitled “Posterior Vitreous Detachment, Retinal Breaks, and Lattice Degeneration,” the latest version of which was published in 2008. The evidence base described in this PPP will be employed in the following discussion. Characteristics associated with a relatively high risk of retinal detachment in an eye with visible retinal breaks are listed in Table 6–1. Symptoms and signs of PVD place an eye at particularly high risk. Additional factors include a variety of hereditary, congenital, acquired, and iatrogenic problems.

Ophthalmoscopy

Indirect viewing systems, including the binocular indirect ophthalmoscope and slit lamp biomicroscopy through an indirect lens, have become the standard of care for management of retinal detachments. Comparison with direct ophthalmoscopy illustrates the capabilities of indirect systems. The technique of indirect ophthalmoscopy with scleral depression is presente The characteristics of direct and indirect ophthalmoscopy are compared in Table 3–1. Figure 3–1A shows the optical principles of direct ophthalmoscopy, and Figure 3–1B illustrates the optics of the indirect method. Substantial clinical differences between the two methods are due to the differences in optical characteristics. The direct ophthalmoscope offers 14X magnification compared with 3X with the indirect using the usual +20 diopter lens. However, this does not mean the direct device has an equal advantage in resolution. Resolution is a function of how close together two points can be and remain distinguished as separate when viewed through an optical system. The visualization of detail that an optical system permits is a function of its resolving power and not its magnifi cation. Resolution is a function of the light available at the points to be resolved and of the quality of the optical components of the system. Magnification plays a role only if the resolution of the optical system exceeds the resolution of the observing human eye at a given level of magnification. Too much magnification of a poorly resolved image results in a loss of detail, such as if one were to examine a halftone newspaper photograph under a microscope. With the direct method, the greater the degree of myopia, the higher the magnification of the fundus image and the smaller the field of view. In very high myopes, the field of view with the direct instrument becomes very limited. High cylindric errors strongly and adversely affect the image of direct ophthalmoscopy because the high magnification of the system also magnifies the effects of refractive errors on the image. With the indirect method, the lower magnification minimizes this effect. Furthermore, the condensing lens can be tilted slightly to overcome astigmatic aberrations. Examination of the retinal periphery entails the travel of light obliquely through the cornea and lens, introducing cylindrical aberrations that are likewise problematic with the direct ophthalmoscope and easily overcome with the indirect.

History of Surgery for Retinal Detachment

The evolution of the retinal reattachment operation is one of the most remarkable chapters in the history of ophthalmology. Gonin’s operation for repair of the detached retina ranks with Daviel’s cataract extraction, von Graefe’s peripheral iridectomy, and Machemer’s vitrectomy as one of history’s most important surgical treatments for blinding eye diseases. The entity of retinal detachment was recognized early in the eighteenth century by de Saint-Yves, who reported the gross pathologic examination of an eye with a detached retina. The first clinical description did not appear until almost a century later, in 1817, when Beer detected a retinal detachment without the benefit of an ophthalmoscope. Von Helmholtz’s invention of the direct ophthalmoscope in 1851 was a giant step forward in diagnostic technique, and a rapid succession of ophthalmoscopic observations of retinal detachments soon followed. In the same year, Coccius reported the ophthalmoscopic detection of breaks in the detached retina. Von Graefe theorized in 1858 that retinal detachment was caused by a serous effusion from the choroid into the subretinal space. When he observed a retinal break, he assumed that it was secondary to the detachment and represented the eye’s attempt to cure itself. Supposing that the development of a break would allow the subretinal fluid to pass from the subretinal space into the vitreous cavity, he attempted unsuccessfully to treat detachments with deliberate incision of the retina. Girard-Teulon invented the reflecting binocular indirect ophthalmoscope in 1861. This potentially important contribution was generally overlooked by the profession, and more than 80 years transpired before Schepens developed the selfilluminating binocular indirect ophthalmoscope. In 1869 Iwanoff described the entity of posterior vitreous detachment, which is now recognized as a prerequisite to the development of most retinal detachments. The following year de Wecker suggested that retinal breaks cause detachment due to the resultant passage of vitreous fluid through the break into the subretinal space. Unfortunately, his accurate interpretation was not generally accepted. In 1882 Leber reported his observation of retinal breaks in 14 of 27 retinal detachments, and he correctly inferred the role of vitreous traction in the pathogenesis of breaks. Unfortunately, he later altered this opinion.

Pneumatic Retinopexy

Pneumatic retinopexy (PR) is an office-based, sutureless, no-incision alternative to scleral buckling or vitrectomy for the surgical repair of selected retinal detachments. Cryotherapy is applied around the retinal break(s) to form a permanent seal. A gas bubble is injected into the vitreous cavity, and the patient is positioned so that the bubble closes the retinal break(s), allowing resorption of the subretinal fluid (Figure 8–1A–F). As an alternative to cryotherapy, laser photocoagulation can be applied after the intraocular gas has caused the retina to reattach. Sulfur hexafluoride (SF6) is the gas most frequently used with pneumatic retinopexy. Perfluorocarbon gases such as perfluoropropane (C3F8) are sometimes used, and success has also been reported with sterile room air. In selecting a gas, it is important to understand the longevity and expansion characteristics of the gases. SF6 doubles in volume within the eye, reaching its maximum size at about 36 hours. It will generally disappear within about 10–14 days, depending on the amount injected. Perfluoropropane nearly quadruples in volume, reaching maximum size in about three days. The bubble will last 30–45 days in the eye. Room air does not expand, but immediately starts to reabsorb. The air bubble will be gone within just a few days (Table 8–1). The initial expansion of SF6 and C3F8 is due to the law of partial pressures and the solubility coefficients of the gases involved. A 100% SF6 bubble injected into the eye contains no nitrogen or oxygen, but these gases are dissolved in the fluid around the bubble. Due to the law of partial pressures, nitrogen and oxygen will diffuse into the gas bubble. SF6 also starts to diffuse out of the gas bubble into the surrounding fluid which contains no SF6. However, nitrogen and oxygen diffuse across the gas–fluid interface much more quickly than SF6 because of the relative insolubility of SF6. The net result is an initial influx of gas molecules into the bubble, expanding its size until partial pressures equilibrate, net influx equals net egress, and maximum expansion is reached. Then the bubble gradually reabsorbs as the SF6 is slowly dissolved in the surrounding fluid.