Metamorphopsia describes a visual phenomenon where straight lines appear wavy, bent, or distorted. Objects may also seem to change in size or shape, appearing larger, smaller, or misshapen. This condition is not an eye disease itself, but a symptom indicating an underlying issue within the eye, often involving the retina and affecting central vision.
Understanding Metamorphopsia
Metamorphopsia distorts central vision, while peripheral vision usually remains unaffected. Individuals might see a doorframe or a grid of tiles as curved, or a flat object like a frisbee might appear rounded. This visual alteration can also cause objects to appear either smaller (micropsia) or larger (macropsia).
These distortions arise from structural changes within the retina, specifically the macula. The macula is responsible for sharp, detailed central vision and color perception. When its shape or position is altered due to wrinkles, holes, or fluid buildup, light signals are mislocated on the retina. This causes the brain to interpret images incorrectly, leading to the warped perception of objects and lines.
Conditions That Cause Metamorphopsia
Several eye conditions can lead to metamorphopsia, primarily those affecting the macula. Age-related Macular Degeneration (AMD) is a common cause, especially in older adults. In wet AMD, abnormal blood vessels grow under the retina and leak fluid or blood into the macula, causing swelling and distortion. Dry AMD involves the thinning of the macula and the formation of yellow deposits called drusen, which can also lead to distorted vision.
Macular edema involves fluid buildup in the macula, often from damaged blood vessels that leak due to conditions like wet AMD or diabetic retinopathy. This fluid causes swelling, which distorts vision. An epiretinal membrane (ERM), also known as a macular pucker, is a thin layer of scar-like tissue that forms on the macula. As this membrane shrinks, it pulls on the macula, causing it to wrinkle and leading to visual distortions.
Central Serous Retinopathy (CSR) can also cause metamorphopsia by leading to fluid accumulation under the retina, which lifts and distorts the macula. Macular holes, which are small breaks in the macula, can result from the macula being pulled or stretched, further contributing to distorted vision. Identifying the specific underlying condition is important for appropriate management.
Addressing Metamorphopsia
The identification of metamorphopsia begins with a comprehensive eye examination. A common tool is the Amsler grid, a pattern of straight lines that can reveal areas of distortion or missing vision. Advanced imaging techniques such as Optical Coherence Tomography (OCT) provide detailed cross-sectional views of the retina, allowing professionals to identify subtle structural changes in the macula. Fluorescein angiography may also be performed, involving injecting a dye into the bloodstream to highlight blood vessels in the retina and detect leaks or abnormal growth.
Treatment for metamorphopsia directly targets the underlying cause. For conditions like wet AMD and some forms of macular edema, injections of anti-VEGF medications into the eye can help reduce fluid leakage and abnormal blood vessel growth. In cases of epiretinal membrane or macular holes, surgical intervention, such as a vitrectomy, may be recommended to remove the membrane or repair the hole. Prompt medical evaluation is important if visual distortions are experienced, as early detection and treatment can improve visual outcomes.