Ординатура / Офтальмология / Английские материалы / Retinal and Vitreoretinal Diseases and Surgery_Boyd, Cortez, Sabates_2010

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Introduction

Traction can be defined as a synonym for force. On the macula, this force can manifest in two vectors: anteroposterior (i.e., originating in the vitreous body) or tangential (i.e., forming on the retinal surface; Figures 1A, 1B). (Author's Note: Traction force can also be created by subretinal scarring; this entity is not discussed here.) The resulting anatomical changes (retinal distortion, fold formation, vascular leakage etc.) can quickly lead to functional consequences in most cases; how early the patient seeks ophthalmologic consultation, though, shows great variability, due to the normal fellow eye’s dominance as well as to the individual’s personality and visual needs.

Vascular incompetence due to traction can occur as reflected in the abnormal fluorescein angiogram. Due to chronic traction-related

vascular incompetence, the macular tissue may become diffusely edematous. The fovea can develop cystic changes over time, which are usually reversible after traction release if the intervention is timely. In extreme cases, however,theuntreatedfovealcystscandevelop into partialor full-thickness holes. Longstanding traction can also produce separation (i.e., true detachment) of the neuroretina in an area involving the fovea or macula.

The cause of traction development is usually unknown (idiopathic); occasionally, the etiology is identifiable: trauma, inflammation, proliferative vitreoretinopathy, etc.

Classification

The term (coined by Robert Morris, MD) “traction maculopathy”1 encompasses four distinct conditions and its common pathogenesis (see Table 1).

Diagnostics

History. Although the condition may be a serendipitous finding, in most cases it is the patient who discovers the functional disturbance. A long history is important because it typically interferes with good visual recovery.

Visual function. A deterioration of visual acuity is the most common finding (and complaint given by the patient), but upon careful testing (and questioning), a distortion of vision is just as often found (hence the recommendation, in addition to the standard visual acuity testing, to utilize the Amsler grid, which shows deformation centrally). (Author's Note: The Amsler grid is a very effective initial diagnostic tool, but it is ineffective to detect further deterioration. The

human brain remembers the previously seen image and does not appreciate the subsequently shown image as new (false-negative test result). The reading speed is another valuable test: A significant drop in the speed of reading a standardized text (MNREAD) may be demonstrated. (Author's Note: This is a crucial advantage over the standard visual acuity testing: the latter measures the reading of single letters, as opposed to the closer-to-life situation of measuring reading ability with the MNREAD test).

Slit lamp biomicroscopy with a 90 D or, preferably, a contact lens. This is the most useful easily available diagnostic tool, allowing the ophthalmologist to view not only the macula in great detail (Figure 2) but also the certain vitreous pathologies (e.g., the presence anteroposterior traction if significant).

Binocular ophthalmoscopy. Although giving fewer fine details than obtainable at the slit lamp, the binocular ophthalmoscope is of great value to show the entire vitreous cavity and widespread vitreoretinal pathologies. (Author's Note: i.e., seeing the “forest, not only the trees”). Foveal ectopia, which can cause diplopia, is easier to detect when one sees the entire posterior pole, not just a smaller central area of the retina, and compares this image with the fundus of the fellow eye.

Optical coherence tomography (OCT). This relatively new but rapidly evolving diagnostic modality is becoming the major weapon in the ophthalmologist’s armamentarium to not only diagnose lesions that may be invisible otherwise (Figure 3A), but also to follow the macula over time as a noninvasive procedure (Figure 3B). The test is thus ever more commonly utilized for diagnosis as well as for following anatomical changes occurring spontaneously (natural history) or after surgery.

Fluorescein angiography. Although it is an invasive diagnostic tool, it is still the only method to show vascular leakage (Figures 4A and B).

Electrophysiology. The multifocal electroretinogram shows marked central depression in eyes with foveal dysfunction (Figure 5); the test is uncommonly utilized in clinical practice but is a good method to follow macular function changes following surgery.

Counseling

Once the diagnosis has been established, it is the ophthalmologist’s responsibility to explain the condition to the patient. The ophthalmologist must describe the natural history – typically one of continual dete-

rioration, although of variable speed -, and the benefits as well as risks of surgery, giving specific numbers (percentages) if these are available. In an ideal situation, it is the patient who chooses to undergo treatment, not the ophthalmologist. (Author's Note: It is unacceptable for the ophthalmologist to set an arbitrary limit below which he would refuse to undertake surgery. It is often said by these ophthalmologists that “I will not operate on a macular hole unless vision is 20/40 or worse”; such – scientifically unjustified – statements do not take into consideration that one individual’s needs and desires can greatly differ from another person’s. Surgery is not done on a macular hole but on an individual who has a macular hole).

The patient must understand that even if the visual symptoms are minimal, certain

complications of traction maculopathy, such as cystoid edema, may cause damage that can prove irreversible if the intervention is delayed indefinitely.

Treatment

The only predictable and effective method to treat patients with traction maculopathy is pars plana vitrectomy. Until a few years ago, all operations would have been performed using 20 g systems, but today many surgeons elect to use smaller g instrumentation (23 or 25 g). (Author's Note: Technical details related to gauge are not discussed in this chapter). In addition, when using the term “complete vitrectomy” here, it rarely means that a radical peripheral vitrectomy with scleral indentation is done; rather, the vitreous base is left intact in most eyes.

For further details, see the individual conditions described below.

Vitreomacular Traction Syndrome

Figure 6: Vitreomacular Traction Syndrome. The top view shows how the vitreous (V) may exert anterior posterior traction (arrow) on the macula (M) as a consequence of forward movement of the vitreous coupled with persistent attachment of cortical vitreous at the macula. Below shows the focally intensified forces (arrows) of the vitreous traction on the macula (M) as exerted by the mass of the entire body of the free moving vitreous.

Dependingontheseverity of the condition, the patient may notice a distinct drop in visual acuity or a severe drop as well as mild to significant distortion(metamorphopsia). An incomplete detachment of the posterior hyaloid face (PHF) is the cause (Figures 6 and 7), but the vitreous may also be completely attached with firm connection to the

internal limiting membrane (ILM), pulling on it as the degenerating vitreous moves. Epimacular proliferation may also be present.

Figure 7: OCT imaging of vitreomacular traction syndrome. The partially detached posterior vitreous face shows strong adhesion to the retina centrally (arrows), causing a dramatic change in the macular contour.

(Image courtesy of Viktoria Mester, MD.)

The OCT may show the actual PHF as well as its attachment to the retina.

Treatment: Removal of the entire vitreous, especially posteriorly (see below in more detail). This is greatly aided by the use of triamcinolone acetonide (TA) as a marker to show the vitreous that otherwise would remain invisible. It is highly recommended to remove the ILM as well, both to make sure that no vitreous is left behind and also because the ILM may also be pathological.

It is helpful to stain the ILM before removal; this makes the procedure less traumatic to the retina, less stressful to the surgeon, and not only reduces the time needed for removal but also allows it to be more complete (see below for details).

The surgeon should consider indirect oph- thalmoscope-delivered encircling laser prophylaxis (Figure 8) to almost eliminate the major risk of vitrectomy for traction maculopathy: retinal detachment from a peripheral break.

Prognosis: If surgery has been timely, excellent outcome is expected; if, however, the condition has been present for an extended period of time and the vision is severely affected, the functional result will not match the anatomical one. The patient must be made aware of this during counseling (see above).

Cellophane Maculopathy

Figure 8: Indirect Ophthalmoscope (IDO) Laser Cerclage Prophylaxis.

is a mild variation of an epimacular proliferation but still interpreted as a distinct entity since no membrane is visible on the retinal surface. With the retinal traction involving only the superficial retina (Figures 9 and 10, this condition can be interpreted as a mild form of an epimacular proliferation. There is no visible membrane present (it is also possible that it is just too thin for detection with current technology), but cells seeding the surface do cause anatomically visible changes. Careful examination is necessary to detect the fine “wave formation” of the retinal surface; often this is best seen intraoperatively, once the retina has been stained. Of the four conditions mentioned herein, this is the least urgently in need of treatment.

(Authoŕs Note: “Preretinal gliosis” is another term occasionally, but incorrectly, used. As described above, cellophane maculopathy

Treatment: If the patient is sufficiently bothered by the metamorphopsia caused by contracted ILM (resembling wrinkled