Herpetic uveitis is a significant cause of sight-threatening ocular disease in the posterior segment of the eye.
Herpes viruses remain latent in the patient who has been previously infected and can reactivate depending on various factors, including patient’s immune system, age and other diseases.
Some viral manifestations, such as acute retinal necrosis, may result in serious complications and profound vision loss.
Since these infections can respond well to the treatment, early diagnosis and prompt management are essential to try and prevent a bad visual outcome.
Acute retinal necrosis (ARN) is a severe, sight-threatening ocular emergency.
The disease is rare, with an incidence of 1 in 2 million people per year in the UK.
There are two peaks of age distribution, at around 20 and 50 years of age, with both genders equally affected.
ARN is usually diagnosed in immunocompetent individuals, people whose immune system is working properly and who are able to produce a normal immune response following exposure to pathogens.
ARN usually starts in one eye, with potential subsequent involvement of the second eye.
The infection affects the retina causing a retinitis . Clinical features include intense intraocular inflammation, involving both the anterior segment and the posterior part of the eye in form of vitritis, focal yellowish patches of necrotizing retinitis and also vascular occlusion of the retinal arteries.
The patches of retinitis are classically located circumferentially in the periphery of the retina and tend to rapidly progress circumferentially and also to move towards the central part of the eye (figure 1 – to be added).
Symptoms include a sudden, painless, decrease in vision, manifesting as photopsias (flashing lights) and scotoma (area of alteration in the field of vision consisting of partially diminished or totally degenerated visual acuity).
Symptoms are usually bilateral but can occur several days apart.
The diagnosis is usually clinical and is made on the basis of the appearance of the retinal lesions on eye examination.
Very frequently , a diagnostic sampling of intraocular fluid can be taken and analysed for the detection of the virus to confirm the diagnosis and rule out other forms of uveitis.
The intention of therapy is to control the active viral infection in the eye, reducing its progression and also reducing inflammation, preventing severe damage to ocular tissues and consequently visual loss.
Treatment should start immediately after a clinical diagnosis is made. Therapy involves the immediate injection of an antiviral agent (Foscarnet) into the vitreous and the use of high doses oral antiviral medications (acyclovir or valacyclovir
Besides antivirals, systemic corticosteroids can be added to the treatment regimen in case of significant inflammation, to mitigate the ocular damage from the inflammatory response.
However, steroids should only be started 24 hours after initiation of antiviral therapy, as they can promote viral replication.
Following acute phase of therapy described above, the patients will continue to use oral anti-viral drugs for at least 3 months to reduce the risk of involvement of the fellow eye. In some cases, the use of the antiviral has to be continued for life.
If not well controlled, the disease is usually characterized by extensive loss of retinal tissue with risk of retinal detachment and severe damage to the optic nerve. All these complications result in bad visual prognosis.
Early diagnosis and proper treatment are critical to reduce the impact of these complications.
Contact
Ilaria Testi
The London Clinic Eye Centre
119 Harley Street
London W1G 6AU
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