Anomalous Retinal Correspondence
Anomalous retinal correspondence (ARC) is a condition wherein the fovea of the fixating eye has acquired an anomalous common visual direction with a peripheral retinal element in the deviating eye. ARC is an adaptation that restores some degree of binocular cooperation despite manifest strabismus. Anomalous binocular vision is a functional state that is superior to total suppression. In the development of ARC, normal sensory development is replaced only gradually and not completely. The more long-standing the deviation, the more deeply rooted the ARC may become. The period during which ARC may develop probably extends through the first decade of life.
Paradoxical diplopia can occur when ARC persists after strabismus surgery. For example, when esotropic patients with proper or nearly proper ocular alignment after surgery report symptoms of a crossed diplopic localization of foveal or parafoveal stimuli, they are experiencing paradoxical diplopia (Fig 5-6). Paradoxical diplopia is typically a fleeting postoperative phenomenon, seldom lasting longer than a few days or weeks, but in rare cases it can persist much longer.
Testing for anomalous retinal correspondence
Testing for ARC is performed to determine how affected patients use their eyes in everyday life and to seek any vestiges of normal correspondence. As discussed earlier, ARC is a sensory adaptation to abnormal ocular alignment. Because the depth of the sensory rearrangement can vary widely, an individual can test positive for both NRC and ARC. Tests that closely simulate everyday use of the eyes are more likely to give evidence of ARC. The more dissociative the test, the more likely it is to produce an NRC response, unless the ARC is deeply rooted. Some of the more common tests (discussed at length in Chapter 7), in order of most to least dissociative, are the afterimage test, the Worth 4-dot test, the red-glass test (dissociation increases with the density of the red filter), amblyoscope testing, and testing with Bagolini striated lenses. If an anomalous localization response occurs in the more dissociative tests, the depth of ARC is greater.
Figure 5-6 Paradoxical diplopia. Diagram of esotropia and ARC, wherein the deviation is being neutralized with a base-out prism. A red glass and base-out prism are placed over the right eye. The prism neutralizes the deviation by moving the retinal image of the penlight temporally, off the pseudofovea (P) to the true fovea (F). Because the pseudofovea is the center of orientation, the image is perceived to fall on the temporal retina and is projected to the opposite field, thus resulting in crossed diplopia.
(Modified with permission from Wright KW, Spiegel PH. Pediatric Ophthalmology and Strabismus. St Louis: Mosby; 1999:219.)
Note that ARC is a binocular phenomenon, tested for and documented in both eyes simultaneously. It is not necessarily related to eccentric fixation (see Chapter 6), which is a monocular phenomenon found in testing 1 eye alone. Because some tests for ARC depend on separate stimulation of each fovea, the presence of eccentric fixation can significantly affect the test results (see also Chapter 7).
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.