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Symptoms ⬇

Blurred vision, floaters, ocular pain, and photophobia. Affected patients are usually immunocompetent.

Signs ⬆ ⬇

(See Figure 12.8.1.)

Critical

The American Uveitis Society criteria include one or more foci of retinal necrosis with discrete borders in the peripheral retina, rapid progression of disease in the absence of antiviral therapy, circumferential spread, evidence of occlusive vasculopathy with arterial involvement, and prominent inflammatory reaction in the anterior chamber and vitreous. If untreated, the circumferential progression of necrosis may become confluent and spread posteriorly. The macula is typically spared early in the disease course.

Other

Anterior chamber reaction; KP; conjunctival injection; episcleritis or scleritis; increased IOP; sheathed retinal arterioles and sometimes venules, especially in the periphery; retinal hemorrhages (minor finding); optic disc edema; delayed RRD occurs in approximately 70% of patients secondary to large irregular posterior breaks. Usually begins unilaterally but may involve the second eye in one-third of cases within weeks to months. An optic neuropathy with disc edema or pallor sometimes develops.

12-8.1 Acute retinal necrosis.

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Differential Diagnosis ⬆ ⬇

See 12.3, POSTERIOR UVEITIS.

  • CMV retinitis (Table 12.8.1).
  • PORN: Rapidly progressive retinitis characterized by clear vitreous and sheet-like opacification deep to normal-looking retinal vessels, and occasional spontaneous vitreous hemorrhage. PORN is usually found in immunocompromised individuals and frequently leads to rapid bilateral blindness due either to the infection itself or to secondary retinal detachment, making prompt diagnosis and treatment essential. Unlike ARN, pain and vitritis are minimal and macular involvement occurs early.
  • Syphilis.
  • Toxoplasma chorioretinitis.
  • Behçet disease.
  • Sarcoidosis.
  • Fungal or bacterial endophthalmitis.
  • Large cell lymphoma. Consider in patients >50 years of age with refractory unilateral vitritis, yellow-white subretinal infiltrates, and absence of pain.

Etiology ⬆ ⬇

ARN is a clinical syndrome caused by the herpes virus family: VZV (older patients), HSV (younger patients), or rarely, CMV or Epstein-Barr virus (EBV).

Work Up ⬆ ⬇

Workup

See 12.3, POSTERIOR UVEITIS, for a nonspecific uveitis workup.

  1. History: Risk factors for AIDS or other immunocompromised states (iatrogenic, autoimmune, malignancy, or genetic)? If yes, the differential diagnosis includes CMV retinitis and PORN. Ask about history of shingles (especially zoster ophthalmicus) or herpes simplex infections. Head trauma (including neurosurgery) and ocular surgery may precipitate ARN. Rarely, ARN can follow periocular or intravitreal corticosteroid injections. Most patients have no identifiable precipitating factors.
  2. Complete ocular examination: Evaluate the anterior chamber and vitreous for cells, measure IOP, and perform a dilated retinal examination using indirect ophthalmoscopy; gentle scleral depression as necrotic retina has an increased risk of retinal detachment.
  3. Consider a CBC with differential, RPR or VDRL, FTA-ABS or treponemal-specific assay, ESR, Toxoplasma titers, PPD or IGRA, and chest radiograph or CT to rule out other etiologies.
  4. Consider HIV testing.
  5. Anterior chamber paracentesis for herpes virus and Toxoplasma PCR to confirm the causative virus is highly specific but sensitivity may vary. See Appendix 13, ANTERIOR CHAMBER PARACENTESIS.
  6. Consider IVFA to identify retinal vasculitis and areas of ischemia.
  7. MRI of the brain and orbits in cases of suspected optic nerve dysfunction.
  8. CT or MRI of the brain and lumbar puncture if large cell lymphoma, tertiary syphilis, or encephalitis is suspected.

Treatment ⬆ ⬇

NOTE:

All patients with ARN should be referred to a specialist.

  1. Prompt inpatient or outpatient treatment. The goal is to decrease the incidence of disease in the fellow eye. Treatment does not reduce the rate of retinal detachment in the first eye.
  2. Oral antivirals (valacyclovir 1 to 2 g t.i.d. or famciclovir 500 mg t.i.d. preferred; acyclovir 800 mg five times per day second-line option as it achieves lower intravitreal levels) with supplemental intravitreal injections with foscarnet (2.4 mg/0.1 mL) or ganciclovir (2 mg/0.1 mL) given one to two times per week. Alternative therapy includes intravenous acyclovir 10 mg/kg t.i.d. for 5 to 14 days (requires dose adjustment for renal insufficiency) with supplemental intravitreal injections as noted above, followed by oral valacyclovir 1 g t.i.d. or acyclovir 400 to 800 mg five times per day. Either of these regimens is maintained for up to 14 weeks from the onset of infection. Involvement of the second eye typically starts within 6 weeks of initial infection. Published literature suggests that primary treatment with oral antivirals in conjunction with the above intravitreal injections has similar efficacy as intravenous therapy. Stabilization and early regression of retinitis are usually seen within 4 days. The lesions may progress during the first 48 hours of treatment. The ideal duration of oral antiviral therapy remains unproven, but since replicating virus in the anterior chamber can be found up to 2 months after the onset of disease, a minimum of 2 months of therapy is recommended, and some experts recommend lifetime therapy to reduce the risk of second-eye involvement (especially if the first eye becomes nonfunctional).
  3. Topical cycloplegic (e.g., atropine 1% t.i.d.) and topical steroid (e.g., prednisolone acetate 1% q2–6h) in the presence of anterior segment inflammation.
  4. The benefits of antiplatelet therapy (e.g., aspirin 81 to 650 mg daily) to minimize vascular thrombosis and help prevent further retinal ischemia remain unproven.
  5. Systemic steroids may be considered, particularly when the optic nerve is thought to be involved. Steroids are usually delayed at least 24 hours after the initiation of antiviral therapy, or when regression of retinal necrosis is evident. A typical oral corticosteroid regimen is prednisone 60 to 80 mg/d for 1 to 2 weeks followed by a taper over 2 to 6 weeks. Subtenon injection of triamcinolone (40 mg/1 mL) can be considered after adequate loading of antiviral therapy but may interfere with the clearance of virus by the eye.
  6. See 9.7, INFLAMMATORY OPEN ANGLE GLAUCOMA, for increased IOP.
  7. Consider prophylactic barrier laser photocoagulation posterior to active retinitis to wall off or prevent subsequent RRD (efficacy unclear).
  8. Pars plana vitrectomy, with long-acting gas or silicone oil, is the best way to repair the associated complex RRD. Proliferative vitreoretinopathy is common.

Follow Up ⬆

  1. Patients are seen daily initially and are examined every few weeks to months for the following year; examination of both eyes is essential.
  2. A careful fundus evaluation is performed at each visit to rule out retinal holes that may lead to a detachment. If barrier laser demarcation has been done and the retinitis subsequently crosses the posterior margin, consider applying additional laser therapy.
  3. Pupillary evaluation should be performed, and optic neuropathy should be considered if the retinopathy does not explain the amount of visual loss.