Eyeworld

EW INTERNATIONAL 92 February 2015 Institute 7th International Ophthal- mology Congress in Singapore. "Other studies have suggested that B- and T-cell imbalance in the immunity of these healthy individ- uals impacts the type and severity of the disease, ranging from ARN to progressive outer retinal necrosis," he said. In the United States, ARN ac- counts for 5.5% of uveitis cases over a 10-year period, and in Switzerland, it accounts for 1.7% of uveitic cases. Adding to the puzzle of ARN, there are other syndromes that might present like it: CMV (cy- tomegalovirus), toxoplasmosis, Behcet's disease, acute multifocal hemorrhagic retinal vasculitis, sar- coidosis, and intraocular lymphoma. As a result, these possibilities should be considered before making the diagnosis of ARN. How to diagnose and treat Drug resistance is uncommon in ARN treatment. Antiviral drugs may have few side effects, but special at- tention needs to be paid to patients who have underlying renal disease, are pregnant, or are immunocom- promised. Imaging studies (i.e., fluoresce- in angiography, ocular ultrasound) have resulted in a significant improvement in the visual progno- sis for affected patients. However, according to Dr. Teoh, identifying the infective root cause of ARN determines the appropriate course of treatment. "Diagnosis in this day and age is largely [based] on polymerase chain reaction (PCR) that gives very rapid results [within 48 to 72 hours], and can be done on very small samples and typically taken from aqueous or vitreous fluid," Dr. Teoh said. "PCR can be done both qualitatively and quantitatively, which can be used to monitor the viral activity in response to therapeutics. Other investigation methods are more complicated and time consuming, so PCR probably remains the most common and fastest method." While confirming the diagnosis by performing an anterior chamber paracentesis and immunofluores- cence studies to assess local VZV and HSV antibody production might be a newer alternative, these are experi- mental methods. The specificity and sensitivity of the procedure remains to be defined. The rarity of ARN cases is a ma- jor factor in the lack of prospective clinical studies. While a few studies have defined the viral causes and therapeutic principles, most observations are derived from small case series, and homogenous international guidelines for therapy remain lacking. According to Dr. Teoh, while the recommended 3–4 month duration of therapy has shown good out- comes, either using traditional acy- clovir or newer antiviral treatment such as valacyclovir, it is unclear what duration of antiviral treatment is necessary to prevent involvement of the fellow eye. In ARN, which generally begins as a unilateral disease, the second eye becomes involved in one-third of the cases. The interval reported between the initial episode and involvement of the second eye averages 1–6 weeks but has been reported to be as long as 34 years. Evaluating the antiviral selec- tion in the management of ARN, Patrick MK Tam and colleagues stated in Clinical Ophthalmology that there is no consensus on the optimal antiviral regimen in the manage- ment of ARN, and the current gold standard is based on retrospective case series. While some antiviral agents have been proven to achieve therapeutic concentrations in the vitreous at conventional doses, the choice would still be based on experience and safety profile. The exact duration of treatment remains unknown. "The traditional treatment of acyclovir [oral and intravenous] and other new treatments as well have had very good outcomes, although there are no published prospective randomized trials conducted to possibly determine which one is the best method," Dr. Teoh said. EW References Cochrane TF, Silvestri G, McDowell C, et al. Acute retinal necrosis in the United Kingdom: results of a prospective surveillance study. Eye (Lond). 2012;26(3):370–378. Ganatra JB, Chandler D, Santos C, et al. Viral causes of the acute retinal necrosis syndrome. Am J Ophthalmol. 2000;129(2):166–72. Tam PM, Hooper CY, Lightman S. Antiviral selection in the management of acute retinal necrosis. Clin Ophthalmol. 2010;4:11–20. Editors' note: Dr. Teoh has no financial interests related to his comments. Contact information Teoh: stephenteoh@eagleeyecentre.com.sg Challenges continued from page 91

• Cover