What is metamorphopsia?

Understanding Metamorphopsia

Metamorphopsia is a visual distortion where objects appear deformed, distorted, or altered in shape, size, or inclination, commonly occurring in various macular disorders. 1

Definition and Characteristics

• Metamorphopsia is a visual illusion that distorts the perception of objects without affecting their actual physical properties 2
• It's a common symptom in patients with epiretinal membrane (ERM) and vitreomacular traction (VMT), causing significant impact on quality of life 1
• Patients often report difficulties with reading, driving, and using both eyes together due to these visual distortions 1

Pathophysiology

• Metamorphopsia develops when there is misalignment or displacement of photoreceptors in the retina, particularly in the macular region 3
• Two general mechanisms can cause binocular metamorphopsia:
  • Distortion manifesting as metamorphopsia, micropsia, or macropsia making foveal images too dissimilar to fuse 1
  • Dragging of the fovea (usually by an epiretinal membrane) creating conflict between central and peripheral alignment, known as "dragged-fovea diplopia syndrome" 1
• Both retinal and cortical mechanisms are involved in the development of metamorphopsia 2

Common Causes

• Epiretinal membrane (ERM): A thin, translucent membrane on the retinal surface that can contract, leading to folds in the retina and distortion 1
• Vitreomacular traction (VMT): Occurs when the posterior vitreous partially detaches but remains adherent to the macula, creating traction 1
• Age-related macular degeneration (AMD): Particularly with choroidal neovascularization 3
• Central serous chorioretinopathy 3
• Neurological causes: Rare forms like reversal of vision metamorphopsia can occur with parieto-occipital brain lesions, brainstem or cerebellar infarcts 4, 5, 6

Clinical Presentation

• Patients commonly report that straight lines appear wavy or distorted 1
• Many close one eye while reading to eliminate distortion from the affected eye 1
• Metamorphopsia can cause diplopia (double vision) when it affects binocular vision 1
• Visual acuity may remain relatively stable despite significant metamorphopsia 1

Diagnosis and Assessment

• Amsler grid: A standard screening tool where patients fixate on a central dot and report any distortions in the surrounding grid pattern 1, 3
• Optical Coherence Tomography (OCT): Highly sensitive method to diagnose and characterize associated retinal changes 1
• M-CHARTS: A quantitative test specifically designed to measure metamorphopsia 3
• Preferential Hyperacuity Perimetry: An emerging method for metamorphopsia assessment 3
• Lights on/off test: Pathognomonic for dragged-fovea diplopia syndrome 1

Management Considerations

• Treatment depends on the underlying cause and severity of symptoms 1
• For ERM or VMT with significant visual impairment, vitrectomy surgery is often indicated 1
• Approximately 80% of patients with ERM or VMT improve by at least 2 lines of visual acuity following vitrectomy 1
• For metamorphopsia causing binocular diplopia, options include:
  • Prism correction (though often provides only transient relief) 1
  • Fogging techniques using Bangerter foils or occlusive contact lenses 1
  • Regular monitoring if symptoms are mild or occasional 1

Clinical Significance

• Metamorphopsia significantly impacts quality of life and is a key patient outcome criterion in macular disorders 1
• Regular monitoring with home Amsler grid testing is important to detect progression 1, 3
• Early detection and treatment of underlying causes can help minimize permanent visual distortion 1