Progressive outer retinal necrosis (PORN) is a variation of herpetic necrotizing retinopathy seen largely in patients with acquired immune deficiency syndrome (AIDS). It is caused by varicella-zoster virus (VZV), the virus that causes chickenpox and, when reactivated from dormancy in the dorsal root ganglia, herpes zoster (shingles). It initially attacks the periphery of the retina and then spreads to involve the entire retina. Unlike typical herpetic necrotizing retinopathy, inflammation of the anterior chamber and vitreous is minimal or absent. It is manifest by variable severity of vision loss at the outset, with a variable but largely discouraging visual outcome. (Engstrom et al. 1488).
Causes
PORN is caused by infection with VZV. This is usually not a primary VZV infection (chickenpox), but rather a reactivation of the virus that has been lying dormant in the dorsal root ganglia since the primary infection (shingles, also known as cutaneous zoster). As opposed to herpetic necrotizing retinopathy, which may also be caused by VZV, it is not associated with herpes virus type I or II (Engstrom et al 1488). While the vast majority of affected patients have severe AIDS, cases have been reported in individuals without AIDS who were immunocompromised for other reasons, such as the use of immunosuppressant drugs to treat rheumatoid arthritis and to prepare the patient for bone marrow transplantation (Bryan and Myers 1249).
History
The most common presenting symptom is unilateral vision loss of varying degree, ranging from a decrease to 20/30 to no light perception. Average visual acuity at diagnosis is 20/80. Occasionally, onset is bilateral, but more often PORN begins unilaterally with rapid progression to the other eye. Vision loss begins in the periphery but can spread rapidly to involve the entire retina (Engstrom et al. 1488).
Physical Findings
Fundoscopic examination shows multifocal, whitish, deep opacities at the periphery of the retina, although one-third of patients will show involvement of the macula (the portion of the retina subserving central vision). As the disease progresses, the lesions become confluent and evolve into full thickness necrosis, spreading to the entire retina if unchecked. Retinal detachment may occur and may involve the macula as well as the periphery (Engstrom et al. 1488).
Diagnosis
The diagnosis of PORN is based largely upon ophthalmoscopic findings in the setting of AIDS or, less commonly, other conditions causing immunocompromise. VZV titers may be helpful. Fluorescein angiography is non-specific, showing decreased uptake at the opacities (Engstrom et al. 1488).
Treatment
Treatment is aimed at the varicella-zoster virus and at preventing or treating retinal detachment. Therapy with single intravenous antiviral agents, such as acyclovir, ganciclovir or foscarnet has not resulted in satisfactory preservation of vision. The use of multiple intravenous antiviral agents has achieved better results, but the use of intravenous antivirals combined with intravitreal injection of agents such as ganciclovir and foscarnet has achieved better recovery of vision, although outcome is still guarded. Reduction of vision to no light perception in the affected eye is still not uncommon (Scott, Luu, and Davis 1219). Steroids are contraindicated. In fact, cases have been reported in which what initially appeared to be optic neuropathy but was actually unrecognized PORN was treated with systemic steroids with disastrous visual results (Benz, Glaser, and Davis 551; Nakamoto et al. 2423).
Retinal detachment occurs in a significant number of cases of PORN. Treatment with laser photocoagulation to demarcate (limit) the extent of the opacities in an attempt to prevent detachment has been employed. If detachment occurs, standard therapies such as scleral buckling, cryotherapy and air-fluid exchange are used (Scott, Luu, and Davis 1219).
Works Cited
Benz, M. S., J.S. Glaser, and J.L. Davis. “Progressive Outer Retinal Necrosis in
Immunocompetent Patients Treated Initially for Optic Neuropathy with Systemic Corticosteroids.” American Journal of Ophthalmology 135.4 (2003): 551-553. Print.
Bryan, Richard G., and Frank L. Myers. “Progressive Outer Retinal Necrosis in a Patient
with Rheumatoid Arthritis.” Archives of Ophthalmology 116.9 (1998): 1249. Print.
Engstrom, R.E., et al. “The Progressive Outer Retinal Necrosis Syndrome. A Variant of
Necrotizing Herpetic Retinopathy in Patients with AIDS.” Ophthalmology 101.9 (1994): 1488-502. Print.
Nakamoto, B.K., E.U. Dorotheo, V. Biousse, R.A. Tang, J.S. Schiffman, and N.J.
Newman. “Progressive Outer Retinal Necrosis Presenting with Isolated Optic Neuropathy.” Neurology 63.12 (2004): 2423-25. Print.
Scott, Ingrid U., Khoa M. Luu, and Janet L. Davis. “Intravitreal Antivirals in the
Management of Patients with Acquired Immune Deficiency Syndrome with Progressive Outer Retinal Necrosis.” Archives of Ophthalmology 120.9 (2002): 1219-22. Print.
