Normal Multifocal ERG and 10-2 Visual Fields in Patient Taking Hydroxychloroquine
This 79 year woman with rheumatoid arthritis was taking hydroxychloroquine for an unknown period of time at an unknown dosage and recently moved to a new city and underwent her first examination with her new ophthalmologist. She had no visual complaints. Her mf ERG is normal. Her initial 10-2 VF is probably normal although there are some scotomas of the left eye. Followup visual fields will help determine if these are truly scotomas or not. Note the difference in display of multifocal electroretinograms and 10-2 visual fields. The multifocal electroretinograms are displayed in the "retina view" as though one were examining fundus photographs. The left panel shows the tracings from the right eye and the right panel shows tracings from the left eye. On the other hand, the 10-2 visual fields are shown as the patient looks into the perimeter bowl. The field for the left eye is shown on the left panel and vice versa for the right eye. Her ophthalmologist made the common mistakes of not determining daily dosage, height, weight, and not determining the date when hydroxychloroquine usage began. The first is important because overdosage is present in 12-20% of patients taking hydroxychloroquine in the United States. Without checking the height and weight, the ophthalmologist cannot know if the dosing is toxic. Knowing duration of therapy is important because the prevalence of retinopathy rises when cumulative dosing rises above 700 grams total.