Retinopathy 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.

12.3 Vascular Disorders 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.

U 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.

328 12 Retina 12.4 Degenerative Retinal Disorders 12.4.1 Retinal Detachment Definition

Retinal detachment refers to the separation of the neurosensory retina (see Fig. 12.2 a) 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 vitreoreti-nopathy 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 vitreore-tinopathy 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).

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

Retinopathy Prematurity
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 vitreoreti-nopathy) 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.

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 rheg-matogenous 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.

H 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.

— Retinal break immediately after argon laser photocoagulation.

Laser Photocoagulation Break
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

332 12 Retina Reattaching a detached retina with a silicone sponge tamponade.

Radial Sponge RetinaPrematurity Detached Retina Adulthood Silicone Oil Tamponade

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.

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.

b a c macular involvement (i.e., the initial detachment included the macula), a loss of visual acuity will remain. The prognosis for the other forms of retinal detachment is usually poor, and they are often associated with significant loss of visual acuity.

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    What is synchysis pelvic?
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