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Image relocation with prisms in patients with age-related macular degeneration
Rani Al-Karmi1, Samuel N Markowitz
1Low Vision Service, University Health Network, Department of Ophthalmology and Vision Sciences, University of Toronto, Toronto, ON, Canada.
Background:
To determine the benefits of image relocation (IR) with prisms in patients with age-related macular degeneration (AMD).
Methods:
This was a retrospective comparative interventional case series of 100 patients with AMD and 5 years of available follow-up records. Participants underwent complete low vision (LV) assessments, including identification of preferred retinal locus (PRL). Prisms were added to prescription glasses to produce IR to the presumed PRL. Main outcome measures were best-corrected visual acuity (BCVA), location of the PRL preferred by the patient for rehabilitation, use of glasses prescribed, and number of prism diopters prescribed.
Results:
Patients wearing prescribed glasses for distance with prisms for IR showed improved BCVA (t(63) = 9.5, p = 0.001) as did those patients wearing prescribed glasses for distance without prisms for IR (t(14) = 2.25, p = 0.04). Patients wearing prescribed glasses for distance with prisms for IR achieved better BCVA than those patients wearing prescribed glasses for distance without prisms for IR (t(77) = 2.0, p = 0.05). Patients reported using distance glasses with prisms for 3 to 48 months (mean [SD], 8.4 [11.7] mo). Number of prism diopters used (mean [SD], 5.8 [1.9] D) was well tolerated by all patients. PRL preferred by patients was on the upper retina in 98.5% of cases.
Interpretation:
IR with prisms to PRL in patients with AMD results in a significant and sizable improvement in BCVA. This effect is probably created by facilitation of oculomotor functions resulting from direct reduction of fixation instability.
