CYSTOID MACULAR EDEMA

Cystoid macular edema (CME) is most commonly encountered after cataract surgery but may arise in association with a number of conditions including retinal vascular disease, retinitis pigmentosa, uveitis, and secondary to the use of several drugs such as epinephrine, latanoprost, and nicotinic acid. Postcataract CME is most commonly observed 1 to 3 months postoperatively. Risk factors include vitreous loss/incarceration, intracapsular extraction technique, and use of iris clip intraocular lenses.

Symptoms

Most patients present with decreased vision. Some patients may note metamorphopsia or micropsia due to macular edema.

Clinical Features

Refraction may demonstrate a hyperopic shift. Cystoid macular edema is difficult to detect without the use of a fundus contact lens. The condition is characterized by a stellate or honeycomb pattern of retinal thickening in the fovea and parafoveal region. Macular biomicroscopy shows thickening of the retina with loss of the normal foveal reflex. This feature may manifest as a yellow spot in the fovea.

Ancillary Testing

Fluorescein angiography is the gold standard test for the evaluation of CME. Accumulation of edema fluid in the outer plexiform layer leads to the characteristic petaloid pattern of cystoid spaces observed around the fovea.

While angiography is more sensitive than clinical examination for the determination of CME, it correlates poorly with visual acuity. Characteristic features are leakage from perifoveal capillaries leading to the late accumulation of dye within the cystoid spaces. Late staining of the optic disc may also occur. Clinical CME complicating nicotinic acid therapy shows no leakage on fluorescein angiography.

Pathology/Pathogenesis

Cystoid macular edema arises from accumulation of edema fluid within the retina due to disruption of the normal blood-retinal barrier. Inflammatory mediators are hypothesized to trigger the breakdown of the bloodretinal barrier. Vitreous traction may impair the normal pumping action of Müller cells and further contribute to the development of edema.

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Pathological examination of the retina demonstrates Müller cell edema and accumulation of edema fluid within the outer plexiform layer. In chronic cases, cysts may coalesce into larger cysts or lamellar/full-thickness macular holes.

Treatment/Prognosis

Preoperative topical nonsteroidal anti-inflammatory drugs (NSAIDs) reduce the incidence of angiographic CME. The clinical benefit of CME prophylaxis is less clear. Many cases of postoperative CME will resolve spontaneously over several weeks to months. Topical NSAIDs and steroids have been demonstrated to be effective in the resolution of postoperative CME; in fact, corticosteroids may have some synergy with NSAIDs in the treatment of this disorder. Patients whose conditions fail topical therapy are considered for periocular steroid therapy. The role of carbonic anhydrase inhibitors and hyperbaric oxygen are controversial. Nd:YAG laser therapy may be used to perform vitreolysis in cases of CME associated with vitreous incarceration in the surgical wound after cataract surgery. In cases of chronic CME, pars plana vitrectomy has been shown to improve the visual outcome in aphakic and pseudophakic patients.

The therapy of CME associated with chronic uveitis is primarily directed at treatment of the underlying inflammation.

Systemic Evaluation

Postoperative CME is not associated with systemic disease. Patients with uveitis and associated CME may have underlying systemic inflammatory diseases that require evaluation.

Cystoid macular edema (CME) is difficult to detect without the use of a fundus contact lens. Findings that suggest the presence of CME include loss of the normal foveal reflex and a yellow spot in the center of the fovea.

Fluorescein angiography is an invaluable tool in the diagnosis of cystoid macular edema. The early findings include leakage from the perifoveal capillaries.

Fluorescein leaks throughout the study, often resulting in a characteristic “petaloid” pattern of dye pooling in the late views.

Cystoid macular edema (CME) is observed most commonly following intraocular surgery. Other causes of CME include retinal vascular occlusions, posterior uveitis, retinal degeneration, and drug toxicities.

This 68-year-old woman had idiopathic vitritis with bilateral CME.

Fluorescein angiogram of the same patient reveals the classic petaloid pattern of late hyperfluorescence.

EPIRETINAL MEMBRANE

Epiretinal membranes are proliferations of glial tissue that produce mechanical distortion of the macula that may or may not be associated with visual symptoms. Numerous terms are used to describe epiretinal membranes, including macular pucker and cellophane maculopathy. While epiretinal membranes may occur secondary to numerous ocular processes, the most common form is idiopathic.

Symptoms

Patients with epiretinal membranes present with a variable reduction in visual acuity. Alterations in the normal anatomy of the macula may lead to significant distortion, binocular diplopia, or even macropsia. Visual loss tends to be stable from the time of diagnosis.

Clinical Features

Macular examination demonstrates the presence of a glistening, crinkled sheen to the retinal surface corresponding to the location of the epiretinal tissue.

Contracture of the epiretinal membrane may lead to distortion of the retinal vasculature and retinal folds. Severe cases may be associated with the presence of foveal ectopia. Retinal examination may demonstrate retinal whitening, retinal edema, or occasional retinal or preretinal hemorrhage. Irregularities of the retinal vasculature are common.

Epiretinal membranes may have gaps resulting in the appearance of a macular pseudohole. Differentiating a pseudohole from a full-thickness macular hole is performed clinically using the slit beam or laser aiming beam test.

Ancillary Testing

In general, the diagnosis of epiretinal membrane is established clinically. Ancillary testing is rarely required. Fluorescein angiography may be obtained to examine the extent of macular distortion and to what degree—if any—the epiretinal membrane is associated with vascular leakage. Optical coherence tomography may allow better visualization of the relationship of the epiretinal membrane to the retinal surface and may be helpful in excluding vitreomacular traction and distinguishing pseudoholes from full-thickness macular holes.

Pathology/Pathogenesis

The most common form of epiretinal membrane is the idiopathic variety, which usually forms after posterior vitreous detachment (PVD). In the absence of a PVD, other ocular conditions should be considered. Epiretinal

membranes may arise in association with retinal vascular disease including retinal venous occlusions and diabetic retinopathy, uveitis, hereditary retinopathies, trauma, or following retinal detachment.

The precise pathogenesis of epiretinal membranes remains unclear. They appear to arise as glial proliferations on the retinal surface. In some cases, inflammatory mediators may play a role in the stimulation of glial proliferation.

Treatment/Prognosis

Asymptomatic epiretinal membranes are common and require no therapy. Patients with significant visual symptoms secondary to epiretinal membrane proliferation may elect to undergo pars plana vitrectomy with removal of the epiretinal tissue. Approximately 70% to 80% of patients will gain at least two lines of visual acuity with successful removal of the epiretinal tissue. Vitrectomy for epiretinal membrane removal is associated with a significant risk of cataract progression.

Systemic Evaluation

Epiretinal membranes are generally not associated with systemic diseases.

An epiretinal membrane is visualized as a glistening, crinkled sheen on the surface of the retina. A pseudohole is present in this patient.

This fundus photograph demonstrates a severe epiretinal membrane with vascular distortion, preretinal hemorrhage, and retinal whitening due to axoplasmic stasis.

More severe cases of epiretinal membrane are associated with retinal and vascular distortion.

Fluorescein angiography of another patient highlights the retinal vascular distortion caused by contraction of the epiretinal membrane. Leakage of fluorescein may be seen in severe cases.

Preoperative fundus photograph of a patient with a prominent epiretinal membrane associated with significant macular distortion and vision loss.

The postoperative photograph of the same patient demonstrates resolution of macular distortion. The patient’s vision improved from 20/300 to 20/25.

HYPOTONY MACULOPATHY

Hypotony is low intraocular pressure (usually 5 mm Hg) leading to functional and structural changes in the eye. Hypotony occurs in a number of clinical settings and may result from reversible or irreversible causes.

The most common setting for hypotony maculopathy is in association with glaucoma filtration surgery, in which 1.3% to 3% of patients may develop maculopathy.

Central visual loss may result from irregular folding of the retina and choroid in the macula.

Symptoms

Patients present with central visual loss and metamorphopsia in the setting of hypotony.

Clinical Features

Visual acuity may be significantly impaired with hypotony. Retinal examination demonstrates irregular retinal and choroidal folds radiating temporally from the optic nerve. The peripapillary choroid is frequently engorged and may mimic papilledema. In severe cases, the insertion of the inferior oblique muscle may visibly produce an internal compression of the macula.

Prolonged hypotony leads to the formation of permanent pigment lines in the macular region. Severe chronic cases of hypotony may result in atrophia bulbi.

Ancillary Testing

Diagnostic testing is primarily directed toward the identification of the cause of hypotony. Anterior segment imaging with gonioscopy or ultrasound biomicroscopy may be useful in the diagnosis of cyclodialysis clefts.

Pathology/Pathogenesis

There are a wide variety of causes of hypotony. In general, hypotony can be classified according to mechanisms including external fistula, internal fistula, ciliary body insufficiency, inflammation, and others. External fistulas are the result of accidental or surgical trauma and link the internal ocular compartments with the ocular surface. Internal fistulas connect the suprachoroidal space with the aqueous or vitreous and include problems such as cyclodialysis and retinal detachment. Ciliary body inflammation may result from medications or surgical interventions. Inflammation produces a reduction in aqueous production as well as an increase in uveoscleral outflow. Rare causes of hypotony include ocular ischemia, giant cell arteritis, uremia, and myotonic dystrophy.

Treatment/Prognosis

Hypotony maculopathy requires identification and correction of the etiology of hypotony. A variety of techniques are described for the management of overfiltering blebs. The visual prognosis is variable. While several case series have described good visual recovery with reversal of hypotony, other series have poorer visual outcomes despite normalization of intraocular pressure.

In cases of prolonged hypotony, the chorioretinal folds persist even after the intraocular pressure is normalized.

Systemic Evaluation

Hypotony maculopathy usually does not have systemic manifestations. Rare systemic causes of hypotony include myotonic dystrophy and ocular ischemia related to carotid occlusive disease or giant cell arteritis.

This fundus photograph demonstrates optic disc swelling and macular distortion in a patient with prolonged hypotony after trabeculectomy.

Hypotony maculopathy resulting from a traumatic cyclodialysis cleft. The patient had numerous chorioretinal folds throughout the macula.

Fluorescein angiography of the same patient reveals prominent, irregular chorioretinal folds.

The macular changes in the same patient resolved after laser therapy to close the cyclodialysis cleft and restore normal intraocular pressure. Macular folds may become permanent in long-standing cases.