Plaquenil, the brand name for hydroxychloroquine, is a medication prescribed for autoimmune conditions like lupus and rheumatoid arthritis. While beneficial, long-term use can lead to hydroxychloroquine retinopathy, a condition involving damage to the retina, the light-sensitive tissue at the back of the eye. This potential for retinal damage means individuals taking the medication require regular monitoring to protect their vision.
Understanding Plaquenil-Induced Retinopathy
Plaquenil-induced retinopathy is a toxic effect on the cells of the retina. The medication can accumulate in the retinal pigment epithelium (RPE) and photoreceptor cells, which detect light and color. This accumulation disrupts cell metabolism and can lead to degeneration of these retinal structures. The damage is often irreversible and can progress even after the medication is stopped, making early detection a priority.
Several factors increase the risk of developing this condition. The most significant are the daily dose and the duration of use. The risk increases for those taking a daily dose higher than 5 milligrams per kilogram of their actual body weight. The risk of toxicity is under 1% within the first five years of use but rises to nearly 20% after 20 years of treatment.
Other risk factors include kidney disease, which can impair the body’s ability to clear the drug, and the concurrent use of tamoxifen. Individuals with pre-existing retinal or macular disease also face a higher risk. The initial stages of retinopathy are asymptomatic, so patients may not notice vision changes until significant damage has occurred. This underscores the importance of proactive screening.
The Role of OCT in Screening
Optical Coherence Tomography (OCT) is a non-invasive imaging test and a primary tool for screening for Plaquenil-induced retinopathy. The technology acts like an “optical ultrasound,” using light waves to create detailed, cross-sectional images of the retina’s layers. This allows an ophthalmologist to see the microscopic structure of the retina with high resolution, revealing changes not visible with other examination methods.
The primary advantage of OCT is its ability to detect subtle structural changes in the retina before a person experiences vision loss. These early signs of toxicity can appear on an OCT scan long before they are visible during a standard clinical exam. The test is quick, painless, and does not involve radiation, making it a safe method for routine monitoring.
Screening involves a baseline eye exam within the first year of starting Plaquenil to identify pre-existing conditions. Annual screening with OCT is recommended to begin after five years of use, or sooner for individuals with major risk factors.
Interpreting OCT Findings for Toxicity
When reviewing an OCT scan for Plaquenil toxicity, an ophthalmologist looks for specific structural changes. The earliest sign is the thinning or disruption of a layer known as the ellipsoid zone (EZ), also called the inner segment/outer segment (IS/OS) junction. The EZ is a component of the photoreceptor cells, and damage to this layer is a direct indicator of early toxic effects.
A more developed sign of toxicity on an OCT scan is the “flying saucer” sign. This term describes a pattern where the ellipsoid zone is lost in the parafoveal region, the area surrounding the fovea. In the earlier stages, the photoreceptor layers directly beneath the fovea are often spared. This pattern creates a shape on the OCT image resembling a flying saucer, with the preserved central fovea as the dome.
The parafoveal “flying saucer” pattern is common, but not the only presentation of Plaquenil toxicity. In some individuals, particularly those of Asian descent, the damage may first appear in a pericentral pattern, located further from the fovea. This requires a wider field of view during OCT imaging to ensure these more peripheral changes are not missed.
If the condition is not detected early, the damage can progress to advanced stages. Late-stage findings include atrophy, or wasting away, of the retinal pigment epithelium (RPE). This advanced damage leads to “bull’s-eye maculopathy,” a pattern of pigment changes signifying severe and irreversible vision loss. The goal of OCT screening is to prevent the disease from reaching this stage.
Management Following Detection
The detection of definite Plaquenil toxicity on an OCT scan prompts immediate action. The first step is for the ophthalmologist to communicate the findings to the prescribing physician, such as a rheumatologist. This collaboration is necessary to confirm the diagnosis and recommend stopping the drug.
There is currently no treatment to restore the lost retinal tissue or function. The primary goal of stopping the medication is to prevent further damage. Halting exposure to the drug can slow or stop the progression of the retinopathy.
The toxic effects can continue to progress for some time even after Plaquenil is discontinued. This is because the drug has a long half-life and can remain in the retinal tissues for an extended period. Continued monitoring by an ophthalmologist is necessary to track the condition’s stability and manage any further vision changes.