The Image Warping Test: A Novel Method to Quantify and Qualify Metamorphopsia.

Purpose: To determine the validity, accuracy and acceptability of the Image Warping Test (IWT), a novel test for the measurement of visual distortion in the central visual field.

Methods: 25 volunteers with metamorphopsia secondary to vitreoretinal pathology were recruited at a tertiary referral center. All subjects underwent ophthalmological examination and measurement of metamorphopsia via Amsler grid, Morphision, M-CHARTS and the IWT. Construct validity was determined through assessment of the association between symptoms, pathology, visual acuity, established metamorphopsia test results and IWT results.

Results: There was close association between subjective estimation of metamorphopsia severity and IWT score (p=0.005), between Morphision result and IWT score (p=0.015), and between the nature of vitreoretinal pathology and IWT score (p=0.007). There was no statistically significant correlation between best corrected distance visual acuity and IWT score, and between M-CHARTS score and IWT score.

Conclusion: The IWT allows the creation of a digital map of subjective metamorphopsia which effectively measures its severity and nature, and opens the possibility to its non-invasive correction in future through inverse mapping of the distortion map onto live images.