Measurement of visual acuity

Measurement of intraocular pressure

Evaluation of the anterior/posterior segment structures by fluorescein angiography

Orbit

Conjunctiva

Iris

Uvea

Papillary and retinal changes

The conjunctival sign

Iris atrophy

Hyphema

Nonproliferative

Proliferative

Angioid streaks occur in association with sickle cell anemia, with an overall incidence of less than 6 %.

The changes are age dependent, occurring in 2 % of sickle cell anemia patients less than 40 years of age versus 22 % in those who are more than 40 years of age.

Epiretinal membranes may produce visual loss in patients with sickle cell anemia.

Macular epiretinal membranes are seen more frequently in those with retinal neovascularization, retinal tears, and vitreous hemorrhage, as well as those that have had laser treatment or surgery of the retina or vitreous.

Progressive visual loss from macular distortion is well known seen in up to 30 % of these patients.

Peripheral neovascularization may stimulate formation of epiretinal membranes by transudation of plasma and RBCs into the vitreous, disrupting the vitreous cortex and inducing posterior vitreous detachment.

Successful treatment of the neovascular tissue reduces the risk of epiretinal membrane development by approximately 30 %.

Although spontaneous separation of epiretinal membranes following treatment of peripheral neovascularization has been observed, surgical removal may be considered when patients exhibit moderate to severe visual loss.

Traction across the macula from peripheral neovascularization is thought to contribute to the formation of macular holes in sickle cell retinopathy.

Abnormalities of the bulbar conjunctival blood vessels are believed to be the result of flow obstruction by sickled cells.

These abnormalities include:

Occlusions of the iris vessels can result in atrophy, and patients may present with asymptomatic white patches of the iris.

Iris neovascularization may develop in eyes with chronic retinal detachment or major arteriole occlusions and can in rare cases cause a secondary neovascular glaucoma.

Sickle cell patients are susceptible to develop central retinal artery occlusions and optic atrophy secondary to elevated intraocular pressure.

Occlusions of the central retinal artery and major arteriolar branches are seen most frequent in young patients with sickle cell anemia.

They may cause permanent or transient visual loss and can occur simultaneously in both eyes.

Arterial occlusion has also been reported to occur as a complication of retrobulbar anesthesia and following compression of the eye during photocoagulation.

Retinal venous occlusions are surprisingly uncommon in patients with sickle cell anemia.

The reason for this is not known but anemia and low blood pressure present in sickle cell patients may be protective against venous occlusions.

Occlusions of the fine vasculature of the macular and perimacular area have been reported in 10–40 % of patients with sickle cell anemia.

In the acute phase, the occluded vessel will have a dark red appearance and may appear as a dark line on fluorescein angiography.

Nerve fiber layer infarcts (cotton-wool spots) are also seen.

Other macular and perimacular changes include:

Careful examination by fluorescein angiograph, is often necessary to identify these macular changes.

These changes may be transient, and the macula may appear normal on subsequent fluorescein angiograms.

A loss of the inner retinal layers results in an ophthalmoscopic focal concavity with an abnormal reflex (retinal depression sign). These changes are usually permanent.

The retinal depression sign is not pathognomonic of sickle cell anemia and may be seen with other arteriolar occlusive diseases, such as embolic retinopathy, vasculitis, and hypertension.

The visual acuity in patients with sickle cell anemia is often normal, despite the presence of an enlarged foveal avascular zone or other evidence of sickle cell maculopathy.

In addition, patients with sickle cell maculopathy have a remarkable absence of visual complaints.

Automated visual field analysis has demonstrated significantly larger scotomas in patients with abnormally enlarged foveal avascular zone.

Color vision testing has revealed a greater incidence of blue-yellow defects in patients with sickle cell retinopathy; however, no significant correlation has been demonstrated between color vision defects and the presence of sickle cell maculopathy.

Choroidal vascular occlusions may occur focally at the level of the choroidal precapillary arteriole or capillary bed (Elschnig’s spots) or from posterior ciliary artery occlusion.

Although focal precapillary arteriole occlusions have not been specifically identified in patients with sickle cell anemia, clinical and histopathologic evidence of spontaneous posterior ciliary artery occlusions have been reported in sickle cell anemia.

The findings are similar to those described following compression of the eye during general anesthesia and after peripheral photocoagulation.

In the acute phase, the occlusions appear as white, circumscribed, triangular patches at the level of the retinal pigment epithelium and outer retina.

Subsequently, the white lesions fade and retinal pigment epithelial mottling develops.

Patients with acute ciliary artery occlusions may be asymptomatic and the diagnosis is often based solely on the appearance of peripheral pigment mottling.

In sickle cell anemia, it has been suggested that choroidal ischemia plays a role in the development of angioid streaks.

When an arteriole of intermediate size is occluded by sickled erythrocytes, hemorrhage may occur.

The hemorrhages typically appear adjacent or distal to an intraluminal obstruction. It is likely that ischemic necrosis causes a weakening of the vessel wall and that reperfusion of the vessel causes a rupture of the damaged vessel wall, resulting in a hemorrhage.

This type of hemorrhage is round or oval shaped and bright red and measures 1/4–1 disk diameter.

Retinal hemorrhages (“salmon patches”), found most commonly in the equatorial periphery.

These hemorrhages are bright red, but after several days, the partially degenerated blood acquires a characteristic orange-red color (hence the name salmon patch).

In most cases, these hemorrhages are asymptomatic.

The majority of these hemorrhages remain confined to the sensory retina; however, blood may leak through the internal limiting membrane into the vitreous or dissect deeper into the subretinal space.

Resolution occurs over days to weeks and may result in a focal area of atrophic split retina (a “schisis” cavity), a pigmented retinal scar, or a grayish-white vitreous deposit, depending on the location of the hemorrhage. The blood is slowly cleared by macrophages.

Over time, hemoglobin degradation occurs. The hemorrhagic defect then appears as bright yellow dots at several levels of the sensory retina; these are known as iridescent bodies.

If the hemorrhage occurs in the outer retinal layers, it appear as dark, oval or round, 1/4–2 disk-diameter chorioretinal lesions. These lesions, which are similar in appearance to chorioretinitis scars, are known as black sunbursts.

The hemorrhages are temporary, and those that occur in the posterior part of the eye are difficult to diagnose. Their late signs, such as iridescent bodies and black sunbursts, can be observed in approximately 25–40 % of cases and are seen more frequent in SCA.