Ординатура / Офтальмология / Английские материалы / Ophthalmology A Short Textbook_Lang_2000

12.3 Vascular Disorders 323

Clinical course and prognosis: The prognosis is poor because irreparable damage to the inner layers of the retina occurs within one hour. Blindness usually cannot be prevented in central retinal artery occlusion. The prognosis is better where only a branch of the artery is occluded unless a macular branch is affected.

12.3.4Hypertensive Retinopathy and Sclerotic Changes

Definition

Arterial changes in hypertension are primarily caused by vasospasm; in arteriosclerosis they are the result of thickening of the wall of the arteriole.

Epidemiology: Arterial hypertension in particular figures prominently in clinical settings.

Vascular changes due to arterial hypertension are the most frequent cause of retinal vein occlusion.

Pathogenesis: High blood pressure can cause breakdown of the blood-retina barrier or obliteration of capillaries. This results in intraretinal bleeding, cot- ton-wool spots, retinal edema, or swelling of the optic disk.

Symptoms: Patients with high blood pressure frequently suffer from headache or eye pain. Impaired vision or loss of visual acuity only occurs in stage III or IV hypertensive vascular changes. Arteriosclerosis does not exhibit any ocular symptoms.

Diagnostic considerations: Hypertensive and arteriosclerotic changes in the fundus are diagnosed by ophthalmoscopy, preferably with the pupil dilated (Tables 12.3 and 12.4). Changes in the retinal vasculature are frequent findings; choroidal infarctions are rare in acute hypertension (Elschnig’s spots: circumscribed atrophy and proliferation of pigment epithelium in the infarcted area).

Differential diagnosis: Ophthalmoscopy should be performed to exclude other vascular retinal disorders such as diabetic retinopathy. Diabetic retinopathy is primarily characterized by parenchymal and vascular changes; a differential diagnosis is made by confirming or excluding the systemic underlying disorder.

Treatment: Treating the underlying disorder is crucial where fundus changes due to arterial retinopathy are present. Blood pressure should be reduced to below 140/90 mm Hg. Fundus changes due to arteriosclerosis are untreatable.

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Table 12.3 Stages of hypertensive vascular changes (as described by Keith, Wagener, and Barker)

The WHO distinguishes between hypertensive retinopathy (stages I and II) and malignant hypertensive retinopathy (stages III and IV)

Table 12.4 Stages of arteriosclerotic vascular changes (as described by Scheie)

Hypertensive retinopathy (Stage III).

Fig. 12.20 Typical findings in this stage include hemorrhages (here readily visible) and cottonwool spots.

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Prophylaxis: Regular blood pressure monitoring and ophthalmoscopic examination of the fundus are required to minimize the risk of complications (see below).

Clinical course and complications: Sequelae of arteriosclerotic and hypertensive vascular changes include retinal artery and vein occlusion and the formation of macroaneurysms that can lead to vitreous hemorrhage. In the presence of papilledema, the subsequent atrophy of the optic nerve can produce lasting and occasionally severe loss of visual acuity.

Prognosis: In some cases, the complications described above are unavoidable despite well controlled blood pressure.

12.3.5Coats’ Disease

Definition

Congenital retinal telangiectasia with vascular anomalies that nearly always presents unilaterally and can lead to exudation and eventually to exudative retinal detachment.

Epidemiology: This rare disorder manifests itself in young children and teenagers. Boys are usually affected (in about 90% of all cases).

Coats’ disease usually occurs in young and teenage boys. It is nearly always unilateral.

Pathogenesis: Telangiectasia and aneurysms lead to exudation and eventually to retinal detachment.

Symptoms: The early stages are characterized by loss of visual acuity, the later stages by leukocoria (white pupil; see Fig. 12.36) or unilateral strabismus, although the combination of leukocoria and strabismus is also possible.

Diagnostic considerations and findings: Ophthalmoscopy will reveal telangiectasia, subretinal whitish exudate with exudative retinal detachment and hemorrhages (Fig. 12.21).

Differential diagnosis: In the advanced stages of the disorder, retinoblastoma should be excluded by ophthalmoscopy and retinopathy of prematurity on the basis of the patient’s history. Both disorders may also cause leukocoria.

Treatment: The treatment of choice is laser photocoagulation or cryotherapy to destroy anomalous vasculature.

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Coats’ disease.

Fig. 12.21 Typical vascular changes of telangiectasia (arrow) accompanied by exudative retinal detachment with numerous lipid deposits (arrowheads).

Prognosis: Left untreated, the disease will eventually cause blindness due to total retinal detachment. Treatment is effective in preventing blindness in about 50% of all patients.

12.3.6Retinopathy of Prematurity

Definition

A retinal disorder attributable to disruption of normal development of the retinal vasculature in preterm infants with birth weight less than 2500 g.

Epidemiology: The disorder is rare. Infants with birth weight below 1000 g are at increased risk of developing the disorder. Retinopathy of prematurity is not always preventable despite optimum care and strict monitoring of partial pressure of oxygen.

Etiology: Preterm birth and exposure to oxygen disturbs the normal development of the retinal vasculature. Vessel obliteration occurs, followed by proliferative neovascularization. This results in vitreous hemorrhage, retinal detachment, and, in the late scarring stage, retrolenticular fibroplasia as vessels and connective tissue fuse with the detached retina.

Findings and symptoms: After an initially asymptomatic clinical course, vitreous hemorrhage or retinal detachment will be accompanied by secondary strabismus. Leukocoria can occur in the retrolenticular fibroplasia stage. Table 12.5 shows the classification of the various stages.

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Table 12.5 Classification of retinopathy of prematurity

Stage Characteristics

Stage I: Demarcation (border between vascularized and nonvascularized retina)

Stage II: Formation of a ridge (development of intraretinal proliferative tissue)

Stage III: Ridge with extraretinal proliferation Stage IV: Subtotal retinal detachment

Stage V: Total retinal detachment

As is customary in ophthalmology, the extent of the respective abnormal change is specified by analogy to a clock face. For example a demarcation line may be said to extend from one to six o’clock. A plus stage includes dilated and tortuous vasculature of the posterior pole in addition to the other changes.

Diagnostic considerations: The retina should be examined with the pupil dilated four weeks after birth at the latest. This may be done as part of the routine examination of the newborn. Follow-up examinations will depend on the degree of retinal vascularization.

Differential diagnosis: Other causes of leukocoria such as retinoblastoma or cataract (see Table 11.1) should be considered.

Treatment: Surgery is rarely successful in stages IV and V. In stage III, laser photocoagulation or cryotherapy is performed in the nonvascularized portion of the retina.

Prophylaxis: Partial pressure of oxygen should be kept as low as possible, and ophthalmologic screening examinations should be performed.

Early detection of retinopathy of prematurity is particularly important.

Clinical course and prognosis: Stage I and II retinopathy resolves spontaneously in 85% of all affected children.

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12.4Degenerative Retinal Disorders

12.4.1Retinal Detachment

Definition

Retinal detachment refers to the separation of the neurosensory retina (see Fig. 12.2a) from the underlying retinal pigment epithelium, to which normally it is loosely attached. This can be classified into four types:

Rhegmatogenous retinal detachment results from a tear, i.e., a break in the retina.

Tractional retinal detachment results from traction, i.e., from vitreous strands that exert tensile forces on the retina (see proliferative vitreoretinopathy and complicated retinal detachment).

Exudative retinal detachment is caused by fluid. Blood, lipids, or serous fluid accumulates between the neurosensory retina and the retinal pigment epithelium. Coats’ disease is a typical example.

Tumor-related retinal detachment.

Primary retinal detachment usually results from a tear. In rare cases, secondary retinal detachment may also result from a tear due to other disorders or injuries. Combinations of both are also possible but rare. Proliferative vitreoretinopathy frequently develops from a chronic retinal detachment (see Chapter 11, Vitreous Body).

Epidemiology: Although retinal detachments are relatively rarely encountered in ophthalmologic practice, they are clinically highly significant as they can lead to blindness if not treated immediately.

Rhegmatogenous retinal detachment (most frequent form): Approximately 7% of all adults have retinal breaks. The incidence of this finding increases with advanced age. The peak incidence is between the fifth and seventh decades of life. This indicates the significance of posterior vitreous detachment (separation of the vitreous body from inner surface of the retina; also age-related) as a cause of retinal detachment. The annual incidence of retinal detachment is one per 10 000 persons; the prevalence is about 0.4% in the elderly. There is a known familial disposition, and retinal detachment also occurs in conjunction with myopia. The prevalence of retinal detachment with emmetropia (normal vision) is 0.2 % compared with 7% in the presence of severe myopia exceeding minus 10 diopters.

Exudative, tractional, and tumor-related retinal detachments are encountered far less frequently.

Etiology: Rhegmatogenous retinal detachment. This disorder develops from an existing break in the retina. Usually this break is in the peripheral retina, rarely in the macula (Fig. 12.22). Two types of breaks are distinguished:

Horseshoe tear (arrow) and retinal detachment (whitish retina).

Fig. 12.22 The image shows a typical reddish horseshoe tear in the retina (arrow) with bullous retinal detachment.

Round breaks: A portion of the retina has been completely torn out due to a posterior vitreous detachment.

Horseshoe tears: The retina is only slightly torn.

Not every retinal break leads to retinal detachment. This will occur only where the liquified vitreous body separates, and vitreous humor penetrates beneath the retina through the tear. The retinal detachment occurs when the forces of adhesion can no longer withstand this process. Tractional forces (tensile forces) of the vitreous body (usually vitreous strands) can also cause retinal detachment with or without synchysis. In this and every other type of retinal detachment, there is a dynamic interplay of tractional and adhesive forces. Whether the retina will detach depends on which of these forces is stronger.

Tractional retinal detachment. This develops from the tensile forces exerted on the retina by preretinal fibrovascular strands (see proliferative vitreoretinopathy) especially in proliferative retinal diseases such as diabetic retinopathy.

Exudative retinal detachment. The primary cause of this type is the breakdown of the inner or outer blood – retina barrier, usually as a result of a vascular disorder such as Coats’ disease. Subretinal fluid with or without hard exudate accumulates between the neurosensory retina and the retinal pigment epithelium.

Tumor-related retinal detachment. Either the transudate from the tumor vasculature or the mass of the tumor separates the retina from its underlying tissue.

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Symptoms: Retinal detachment can remain asymptomatic for a long time. In the stage of acute posterior vitreous detachment, the patient will notice flashes of light (photopsia) and floaters, black points that move with the patient’s gaze. A posterior vitreous detachment that causes a retinal tear may also cause avulsion of a retinal vessel. Blood from this vessel will then enter the vitreous body. The patient will perceive this as “black rain,” numerous slowly falling small black dots. Another symptom is a dark shadow in the visual field. This occurs when the retina detaches. The patient will perceive a falling curtain or a rising wall, depending on whether the detachment is superior or inferior. A break in the center of the retina will result in a sudden and significant loss of visual acuity, which will include metamorphopsia (image distortion) if the macula is involved.

Diagnostic considerations: The lesion is diagnosed by stereoscopic examination of the fundus with the pupil dilated. The detached retina will be white and edematous and will lose its transparency. Ophthalmoscopy will reveal a bullous retinal detachment; in rhegmatogenous retinal detachment, a bright red retinal break will also be visible (see Fig. 12.22). The tears in rhegmatogenous retinal detachment usually occur in the superior half of the retina in a region of equatorial degeneration. In tractional retinal detachment, the bullous detachment will be accompanied by preretinal gray strands. In exudative retinal detachment, one will observe the typical picture of serous detachment; the exudative retinal detachment will generally be accompanied by massive fatty deposits and often by intraretinal bleeding.

The tumor-related retinal detachment (as can occur with a malignant melanoma) either leads to secondary retinal detachment over the tumor or at some distance from the tumor in the inferior peripheral retina. Ultrasound studies can help confirm the diagnosis where retinal findings are equivocal or a tumor is suspected.

An inferior retinal detachment at some distance from the tumor is a sign that the tumor is malignant.

Differential diagnosis: Degenerative retinoschisis is the primary disorder that should be excluded as it can also involve rhegmatogenous retinal detachments in rare cases. A retinal detachment may also be confused with a choroidal detachment. Fluid accumulation in the choroid, due to inflammatory choroidal disorders such as Vogt-Koyanagi-Harada syndrome, causes the retinal pigment epithelium and neurosensory retina to bulge outward. These forms of retinal detachment have a greenish dark brown color in contrast to the other forms of retinal detachment discussed here.

Treatment: Retinal breaks with minimal circular retinal detachment can be treated with argon laser coagulation (Fig. 12.23). The retina surrounding the break is fused to the underlying tissue whereas the break itself is left open. The scars resulting from argon laser therapy are sufficient to prevent any

Retinal break immediately after argon laser photocoagulation.

Fig. 12.23 Circular white laser burns are visible around the break.

further retinal detachment. More extensive retinal detachments are usually treated with a retinal tamponade with an elastic silicone sponge that is sutured to the outer surface of the sclera, a so-called budding procedure (Fig. 12.24a – c). It can be sutured either in a radial position (perpendicular to the limbus) or parallel to the limbus. This indents the wall of the globe at the retinal break and brings the portion of the retina in which the break is located back into contact with the retinal pigment epithelium. The indentation also reduces the traction of the vitreous body on the retina. An artifical scar is created to stabilize the restored contact between the neurosensory retina and retinal pigment epithelium. This is achieved with a cryoprobe. After a successful operation, this scar prevents recurring retinal detachment. Where there are several retinal breaks or the break cannot be located, a silicone cerclage is applied to the globe as a circumferential buckling procedure. The procedures described up until now apply to uncomplicated retinal detachments, i.e., without proliferative vitreoretinopathy. Suturing a retinal tamponade with silicone sponge may also be attempted initially in a complicated retinal detachment with proliferative vitreoretinopathy. If this treatment is unsuccessful, the vitreoretinal proliferations are excised, and a vitrectomy is performed in which the vitreous body is replaced with Ringer’s solution, gas, or silicone oil. These fluids tamponade the eye from within.

Prophylaxis: High-risk patients above the age of 40 with a positive family history and severe myopia should be regularly examined by an ophthalmologist, preferably once a year.

Clinical course and prognosis: About 95% of rhegmatogenous retinal detachments can be treated successfully with surgery Where there has been

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Reattaching a detached retina with a silicone sponge tamponade.

c

Fig. 12.24 a The ocular muscles are retracted and the eye is brought into the proper position for the operation. The tamponade is sutured to the outer surface of the sclera. b Cross section of the eye with the tamponade in place: The globe is indented at the site of the tamponade. c Wedged beneath the horseshoe tear (arrow) is a radial tamponade (arrowhead). The retina is again in contact with the underlying tissue.