Dragged Fovea Diplopia Syndrome

Ms Tsering Lamu Shongmu, Ph.D. Scholar

Assistant Professor, Sushant University, Gurugram, India

 

Introduction:

Dragged Fovea Diplopia Syndrome is a distinct form of central binocular diplopia resulting from the displacement of the fovea in one or both eyes cause by epiretinal membranes or macular diseases. ⁽¹⁾ This leads to a type of diplopia known as central-peripheral rivalry (CPR), where peripheral retinal images merge while central images misalign, causing a conflict between central and peripheral vision. ^(2-5) While its prevalence remains uncertain, a cure isn’t known. However, treatments are available to alleviate symptoms and enhance the quality of life. Advancements in understanding the syndrome’s causes could offer better therapeutic solutions in the future.

Pathophysiology:

The syndrome’s pathophysiology disrupts normal binocular vision and central-peripheral fusion mechanisms. In typical vision, foveal and peripheral images merge harmoniously, but foveal displacement disturbs this alignment. Attempts to fuse the macula result in peripheral misalignment, and vice versa. Peripheral fusion’s dominance leads to persistent central diplopia. The dragged fovea’s loss of correspondence with the other fovea creates conflict between central and peripheral fusion. This occurs because the peripheral drive for fusion surpasses the central drive due to the larger extent of Panum’s fusional area in the periphery compared to the central region. ^(6,7)  Consequently, central diplopia becomes evident, and conventional prism treatment is unable to exclusively affect the central retina, leaving the diplopia unresolved despite prism intervention.

Clinical Presentation:

Foveal displacement causing retinal image changes results in visual distortion, making objects appear altered. This syndrome disrupts normal binocular vision, causing double images (diplopia) and visual disturbances. Retinal receptor compression/stretching induced aniseikonia, altering receptor spacing. ^(5-8) Surgical repair for macula-off retinal detachments might trigger strabismus and diplopia. ^(3,4) Comitant strabismus with a vertical element often occurs. Sometimes, metamorphopsia (distorts straight lines), micropsia (when the photoreceptors become stretched) and macropsia (when photoreceptors become compressed) may occur. Unlike optical aniseikonia, retinally-induced aniseikonia is heterogeneous and varies in amount in different parts of the visual field. ^(6,7,9) Syndrome severity varies due to foveal displacement’s extent and underlying macular/retinal conditions.

Diagnostic test:

Lights on–off test: This test is also known as small-field central fusion test, which was found to be pathognomonic for diagnosing the dragged-fovea diplopia syndrome. Patients focus on a white 20/70 letter on a black screen with both eyes open. With the room lights on, the isolated letter appeared to be double to patients with dragged fovea diplopia syndrome due to peripheral fusion predominated over central fusion, and central foveae were misaligned with each other, leading to central diplopia. With room lights off, the doubled letter becomes single, within 2 to 10 seconds.

Management:

Treating dragged fovea syndrome presents challenges due to its complexity. While a definitive cure remains elusive, effective symptom management options are available. Non-surgical strategies encompass an array of choices, including prisms (Fresnel, incorporated, or loose), a full-lens-covering Bangerter filter, and translucent adhesive tape (like Scotch Satin Tape from 3M Company, facilitating at-home segmental occlusion). Additionally, iseikonic manipulation utilising lenses ranging from 1% to 5%, integrated into eyewear or contact lens, and the application of a MIN lens, are considered. ⁽⁹⁾

Initial positive responses to prism glasses are common, but diplopia recurrence—either immediately or within days—limits its success. ⁽²⁾ Vertical Fresnel prisms may prove beneficial, as they could surpass the patient’s small vertical motor fusion capacity and prevent undesirable fusion responses. ⁽¹¹⁾ Low-density Bangerter filters provide a cost-effective and visually pleasing solution for persistent binocular diplopia due to macular issues, ensuring peripheral fusion is maintained. ⁽¹²⁾ Fogging is believed to relieve binocular diplopia by inducing a central scotoma in the affected eye. ⁽¹¹⁾ Combining prism correction and Bangerter foil might be necessary to align the scotoma and eliminate diplopia. ⁽¹¹⁾ Monocular occlusion using patches and Bangerter filters eradicates diplopia, but patients may find them noticeable. ⁽¹²⁾

Careful consideration is needed for these methods due to their potential tolerance issues and visibility concerns. In CPR caused by Epiretinal Membrane (ERM), ERM peeling surgery has shown diplopia improvement. ⁽¹³⁾

 

References:

1. Burgess, D., Roper-Hall, G., & Burde, R. M. (1980). Binocular diplopia associated with subretinal neovascular membranes. Archives of ophthalmology, 98(2), 311-317
2. Silverberg M, Schuler E, Veronneau-Troutman S, Wald K, et al. Nonsurgical management of binocular diplopia induced by macular pathology. Arch Ophthalmol 1999; 117: 900-903.
3. Bixenman WW, Joffe L. Binocular diplopia associated with retinal wrinkling. J Pediatr Ophthalmol Strabismus 1984; 21: 215-219.
4. Guyton, D. L. (2019). The “lights on-off test” in the diagnosis of the dragged-fovea diplopia syndrome. JAMA ophthalmology, 137(3), 298-299.
5. Benegas NM, Egbert J, Engel WK, Kushner BJ. Diplopia secondary to aniseikonia associated with macular disease. Arch Ophthalmol 1999; 117: 896-899.
6. Burian HM. Fusional movements in permanent strabismus: a study of the role of the central and peripheral retinal regions in the act of binocular vision in squint. Arch Ophthalmol 1941; 26: 626-652.
7. Burian HM. Fusional movements: role of peripheral retinal stimuli. Arch Ophthalmol 1939; 21: 486-491.
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9. Hatt, S. R., Leske, D. A., Klaehn, L. D., Kramer, A. M., Iezzi Jr, R., & Holmes, J. M. (2019). Treatment for central-peripheral rivalry-type diplopia (“dragged-fovea diplopia syndrome”). American journal of ophthalmology, 208, 41-46.
10. Kushner, B. J., Alvares, M. G., Paysse, E. A., Brooks, S. E., & Borchert, M. (1999). Grand rounds# 53: A case of small angle strabismus, torsion, aniseikonia and diplopia associated with epiretinal membranes [clincical conference]. Binocular vision & strabismus quarterly, 14(1), 46-52.
11. Iacobucci, I. L., Furr, B. A., & Archer, S. M. (2009). Management of binocular diplopia due to maculopathy with combined bangerter filter and fresnel prism. American Orthoptic Journal, 59(1), 93-97.
12. Silverberg, M., Schuler, E., Veronneau-Troutman, S., Wald, K., Schlossman, A., & Medow, N. (1999). Nonsurgical management of binocular diplopia induced by macular pathology. Archives of Ophthalmology, 117(7), 900-903.
13. Hatt, S. R., Leske, D. A., Klaehn, L. D., Kramer, A. M., Iezzi Jr, R., & Holmes, J. M. (2019). Treatment for central-peripheral rivalry-type diplopia (“dragged-fovea diplopia syndrome”). American journal of ophthalmology, 208, 41-46.