RETINAL ARTERIAL MACROANEURYSMS

Retinal arterial macroaneurysms are round or oval arteriolar dilations, usually seen in the posterior pole. They occur more commonly in women than men, in the sixth or seventh decade of life. Typically, they are solitary and unilateral. An estimated 50% to 75% of patients have a history of systemic hypertension.

Symptoms

Macroaneurysms may be found in asymptomatic patients when there is no foveal involvement. Symptoms associated with macroaneurysms include blurred or distorted vision, a blind spot in the vision, or, less commonly, floaters resulting from vitreous hemorrhage.

Clinical Features

Macroaneurysms occur within the first three orders of retinal arterial bifurcation. They are usually located superotemporally and often occur at an arterial bifurcation or arteriovenous crossing site. They may be obscured or surrounded by hemorrhage or a circinate pattern of proteinaceous and lipid exudates. Also, a serous detachment of the retina may be associated. A distinguishing feature of a ruptured macroaneurysm is the presence of blood in multiple layers (subretinal, intraretinal, and preretinal). Visual loss may occur when fluid, lipid, or hemorrhage involves the fovea. Visual loss may also occur from vitreous hemorrhage.

Ancillary Testing

Fluorescein angiography is helpful in delineating the macroaneurysm. If not obscured by blood, it is evident as a focal area of hyperfluorescence early in the study, with or without associated late leakage of dye. There may be an associated partial or complete obstruction of the affected artery at the site of the macroaneurysm, and, in some cases, microvascular abnormalities are seen surrounding the aneurysm. Indocyanine green angiography has been used to identify macroaneurysms obscured by intraor prereretinal hemorrhage.

Pathology/Pathogenesis

Histopathologically, macroaneurysms represent linear breaks in the arterial wall surrounded by laminar-fibrin platelet clot, hemorrhage, lipid-laden macrophages, hemosiderin, and a fibroglial reaction.

Treatment/Prognosis

Treatment is indicated when visual loss results from accumulation of fluid or exudate in the macula. Since the majority of macroaneurysms heal spontaneously, treatment is usually not indicated in the absence of central visual loss. Recommended treatment is photocoagulation, with either the green or yellow wavelength applied directly to or surrounding the macroaneurysm. A low-intensity, longer-duration burn is recommended.

Complications of treatment may include arterial obstruction and vitreous hemorrhage. Visual prognosis is directly related to the degree and duration of foveal involvement with either hemorrhage or exudate. Controversy exists regarding the efficacy of surgical evacuation of large macular hemorrhages.

Systemic Evaluation

Because of the strong association between arterial macroaneurysms and hypertension, patients with arterial macroaneurysms should be evaluated for hypertension.

A 68-year-old woman had sudden loss of vision in her right eye following rupture of a retinal arterial macroaneurysm. Note the presence of preretinal, intraretinal, and subretinal hemorrhage.

Visual loss from a retinal arterial macroaneurysm may also result from macular edema. This patient had a macular star pattern of lipid exudate originating from an inferotemporal macroaneurysm.

Fluorescein angiogram demonstrates hyperfluorescence of the macroaneurysm. Hypofluorescence is caused by preretinal and subretinal blood.

Fluorescein angiography demonstrates the hyperfluorescent macroaneurysm. This patient suffered a branch retinal arterial occlusion following rupture of the macroaneurysm.

The presence of hemorrhage in multiple layers (preretinal, subretinal, and intraretinal) suggests the possibility of a ruptured macroaneurysm. In general, the visual prognosis is favorable.

However, pigmentary alterations following prolonged subretinal hemorrhage may limit the recovery.

RETINOPATHY OF PREMATURITY

Retinopathy of prematurity (ROP), known in the past as retrolental fibroplasia, is a neovascular disorder of the developing retina that occurs in premature infants. The disease tends to occur bilaterally but may be asymmetric in its severity. In some infants with ROP, especially those of very low birth weight and early gestational age, macular distortion (dragging) or traction retinal detachment may occur, resulting in profound visual loss.

Symptoms

Premature infants with early-stage ROP exhibit no observable symptoms. The diagnosis of ROP must be made by careful screening examinations. If macular distortion or detachment occurs, the infant will fail to exhibit normal visual behavior (such as fixing on faces or objects).

Clinical Findings

Detection of ROP requires indirect ophthalmoscopic examination with scleral depression. The funduscopic findings are classified into five stages, and the fundus is divided into three zones.

A normal premature infant’s fundus has retinal vessels extending from the optic disc outward into the retina with peripheral featureless, avascular retina. In stage 1 ROP, a flat white “demarcation line” develops between the vascular and avascular retina. In stage 2 ROP, this line has visible height and is called a ridge. Stage 3 ROP denotes the development of pink to red fibrovascular proliferations emanating from the surface of the ridge into the overlying vitreous. Stages 4 and 5 ROP denote retinal detachment, with stage 4 being subtotal and stage 5 being total retinal detachment. Stage 4 ROP is further subdivided into 4A (macula on) and 4B (macula off).

The zone designation indicates the anterior to posterior location of disease in the fundus. All zones are centered on the optic disc, not the fovea, because the retinal vessels grow out from the disc. Zone 1 is a circle with a radius of twice the distance between the optic disc and the center of the macula. Zone 2 has a radius equal to the distance between the optic disc and the nasal ora serrata. Zone 3 is the remaining temporal crescent of retina.

The designation “plus disease” indicates that the retinal vessels appear dilated and tortuous (thought to be due to high blood flow through peripheral neovascular tissue and arteriovenous shunts). Other features include iris vascular engorgement, pupillary rigidity, and vitreous haze.

Ancillary Testing

Aside from careful ophthalmoscopic examination, no other testing is necessary. However, visual evoked potentials may be of use in evaluating infants with total retinal detachment before attempted surgical repair.

Treatment/Prognosis

The treatment of stage 3 ROP consists of ablation of the peripheral avascular retina by either cryotherapy or indirect laser photocoagulation. In general, treatment is not instituted until the degree of stage 3 reaches threshold and until plus disease develops. Threshold is defined

as more than 5 contiguous clock hours of stage 3 disease or as less than 8 noncontiguous clock hours of stage 3 disease.

The beneficial effects of cryotherapy were well documented in the CRYO-ROP study. Since the study, which was performed in the mid-1980s, diode (infrared) indirect laser photocoagulation has become available and is the generally accepted mode of treatment. Infants with retinal detachment may be treated with either scleral buckling or vitrectomy.

Systemic Evaluation

The CRYO-ROP study demonstrated that infants with birth weights less than 1250 g have a higher risk of developing stage 3 ROP than do those infants with higher birth weights. The risk of neovascular ROP rises with lower birth weight, such that infants with birth weights less than 750 g have at least a 15% risk of developing threshold ROP.

Stage 1 retinopathy of prematurity demonstrates a demarcation line that develops between the vascularized and avascular retina. (Photograph reproduced with permission from the CRYO-ROP Study Group.)

Stage 3 retinopathy of prematurity (ROP) shows fibrovascular proliferations that extend from the ridge to the vitreous. Threshold ROP is defined. (Photograph

reproduced with permission from the CRYO-ROP Study Group.)

Treatment for retinopathy of prematurity involves applying cyrotherapy or laser photocoagulation to the peripheral avascular retina. This schematic from

the CRYO-ROP study demonstrates the near confluent application of cyrotherapy. (Photograph reproduced

Stage 2 retinopathy of prematurity exhibits the demarcation line after it develops thickness and height, forming a ridge. (Photograph reproduced with permission from the CRYO-ROP Study Group.)

Plus disease indicates that the retinal vessels are dilated and tortuous. Other features include iris vascular engorgement, pupillary rigidity, and vitreous haze.

(Photograph reproduced with permission from the CRYO-ROP Study Group.)

RetCam image immediately following laser photocoagulation for threshold retinopathy of prematurity. Laser treatment is applied to the peripheral avascular retina.