Purpose

To identify the clinical characteristics of the dragged-fovea diplopia syndrome, to introduce a simple diagnostic test that aids in the evaluation of such patients, and to provide a simple treatment option to improve the diplopia in some of these patients.

Design

Retrospective, observational case series.

Participants

Ninety-five affected eyes in 83 consecutive patients seen between January 1, 1993, and August 9, 2004, who were diagnosed with the dragged-fovea diplopia syndrome at one institution.

Methods

We reviewed the records of 222 patients who have been seen in the Krieger Children’s Eye Center at The Wilmer Institute since 1993 with a diagnosis of maculopathy, internal limiting membrane, or dragged fovea. We collected ocular findings and history for those patients who reported binocular diplopia that was not amenable to prism therapy and not secondary to acquired strabismus.

Main Outcome Measures

We recorded the presence of metamorphopsia on Amsler grid testing or other clinical evidence of macular wrinkling, response to prism trial, response to the small-field central fusion test (lights on-off test), and response to partial occlusion with Scotch Satin tape (3M Co., St. Paul, MN).

Results

Ninety-five affected eyes in 83 patients met the criteria for inclusion in the study. All patients who were tested with the lights on-off test (n = 69) responded positively, demonstrating rapid central fusion with room lights off, and recurrence of central diplopia with peripheral fusion with room lights on. Forty-six patients (of 64 tested) were receptive to monocular occlusion with Scotch Satin tape.

Conclusions

The dragged-fovea diplopia syndrome consists of central diplopia in the presence of peripheral fusion, secondary to dragging of the fovea in one or both eyes by retinal disease. The central diplopia cannot be eliminated by prism therapy or eye muscle surgery. The lights on-off test has proved pathognomonic for this syndrome, and many patients have benefited from partial monocular occlusion with Scotch Satin tape.

Article Outline

Patients and Methods

Results

Discussion

References

Epiretinal membranes are a common retinal disorder.¹ The clinical appearance varies from a subtle epiretinal membrane to a severe wrinkling with distortion of macular architecture. They can be asymptomatic or can cause varying degrees of metamorphopsia and visual impairment. Several other macular conditions, such as choroidal neovascular membranes, localized macular detachments, or paramacular scars, can cause macular distortion with similar symptoms.

Crone² first reported binocular diplopia associated with metamorphopsia from retinal lesions in 1973. Patients with the dragged-fovea diplopia syndrome have central binocular diplopia secondary to displacement of one or both foveas by epiretinal membranes or other maculopathies.^{2, 3, 4, 5, 6, 7 and 8} The dragged fovea can lose correspondence with the other fovea, causing a conflict between central and peripheral fusion. This results in diplopia that may be relieved momentarily by prisms as the foveas are realigned, but diplopia recurs as peripheral fusion mechanisms overwhelm central fusion.^{2, 3, 4, 5, 6, 7 and 8}

We report the clinical findings of 83 patients diagnosed with the dragged-fovea diplopia syndrome seen in our clinic between 1993 and 2004. We describe a simple diagnostic test, the lights on-off test, which has proved pathognomonic for this syndrome (Fig 1). We also describe a simple treatment option that has proved useful to many patients, one that relieves the central diplopia while avoiding the objectionable appearance of other forms of occlusion. We previously published a brief description of this syndrome, without data, based on approximately half of the patients described here.⁷

Figure 1. The lights on-off test. Left, Arrangement for the lights on-off test, with a single white letter (20/70–20/100) on a black background. Center, Simulation of a patient’s reported view with the room lights on (central oblique diplopia). Note that fusion has occurred in the peripheral field, enhanced by toys and other fusional detail, but now with central oblique diplopia. Right, Simulation of a patient’s reported view with the room lights off (fusion of the originally diplopic image).

Patients and Methods

We retrospectively reviewed the charts of 222 patients seen primarily by the senior author between January 1, 1993, and August 9, 2004, at the Pediatric Ophthalmology and Adult Strabismus service of the Wilmer Ophthalmological Institute who had a diagnosis of maculopathy, internal limiting membrane, or dragged fovea. We excluded patients who did not report diplopia, patients whose diplopia was secondary to acquired strabismus, or patients whose diplopia could be relieved effectively by prism therapy. Data collected from the records included the patient’s age, sex, affected eye (defined as having metamorphopsia on the Amsler grid test or clinical evidence of macular wrinkling), best-corrected visual acuity, refraction, presence of prism in glasses, presence of monocular or binocular diplopia, or both, orientation of diplopia, Amsler grid test results, and previous ocular surgeries. Information on the clinical appearance of the macula and the cause of the maculopathy was recorded from our clinical evaluation or from the referring physician’s evaluation. The orthoptic examination included ocular motility, the Lancaster red-green test in some cases, stereopsis test results, and response to prism trial. Institutional review board approval was obtained.

We discovered a useful test for demonstrating the effects of peripheral versus central fusion, which we call the small-field central fusion test, or more simply the lights on-off test. The patient’s attention is directed to a single white 20/70 letter on a black monitor screen (Fig 1, left). With the room lights on, the single white letter is seen double in patients with this syndrome (Fig 1, center). When the room lights are suddenly extinguished, the doubled letter becomes single, usually in 2 to 10 seconds (Fig 1, right). We call this a positive lights on-off test. We found this test to be universally positive in patients with demonstrable central versus peripheral fusion conflict as evidenced by failure of prism to maintain initial central fusion. This test is easy to perform and more clearly and convincingly demonstrates the nature of the problem to the patient than a prism trial.

The patients were not required to return for examination to be included in this study. When they were diagnosed with the dragged-fovea diplopia syndrome, patients were informed that there is only symptomatic treatment available at this time, and that follow-up would not be necessary. In the cases of the few patients (9 of 83) who returned since their diagnosis, data were recorded from the date of the visit when they were first diagnosed with the dragged-fovea diplopia syndrome, although more recent visits were reviewed for concordance with the conclusions of this analysis.

Results

Eighty-three patients with internal limiting membrane, dragged fovea, epiretinal membrane, or other maculopathy were referred to our clinic over an 11-year period because of acquired binocular diplopia. The mean age of these patients was 67 years (standard deviation [SD], 11 years), with a range from 30 to 86 years of age. There were 28 women and 55 men. Because the incidence of epiretinal membranes has been reported not to differ between men and women,¹ we cannot explain the gender difference in our patient population. We did not record demographic data other than age and gender, although we assumed that the incidence of the dragged-fovea diplopia syndrome likely follows the same demographic trends as the incidence of epiretinal membranes.

There were a total of 95 affected eyes, which were defined as eyes having an abnormal Amsler grid test result, other clinical evidence of foveal distortion, or both. Seven patients (8%) reported monocular diplopia in one eye each. Monocular diplopia disappeared with proper refraction, but binocular diplopia persisted. Best-corrected visual acuity using the logarithm of the minimum angle of resolution system was 20/20 (SD, 1.1 logarithm of the minimum angle of resolution lines) in the unaffected eyes and 20/26 (SD, 1.7 logarithm of the minimum angle of resolution lines) in affected eyes.^{9 and 10} Eighty-four (88%) of the affected eyes had 20/40 visual acuity or better. All affected eyes had visual acuity of 20/80 or better. Mean spherical equivalent refraction was −1.78 diopters (D; SD, 4.25 D). Forty-two patients (51%) had prism in their glasses at the initial evaluation. Twenty-seven (33%) had vertical prism, 4 (5%) had horizontal prism, and 11 (13%) had combined horizontal and vertical prism.

Sixty-three patients (76%) reported vertical diplopia, 9 (11%) reported horizontal diplopia, 9 (11%) reported combined horizontal and vertical diplopia, and 2 patients (2%) reported torsional diplopia. Eighteen patients (22%) reported some degree of aniseikonia, with the image in the affected eye being either larger or smaller.

On ocular motility evaluation, no visible shift was seen on cover-uncover testing, or on alternate cover testing, in 16 patients (19%) at distance and in 16 patients (19%) at near. Twenty-six patients (31%) had an exodeviation (ranging from flick exotropia to an exotropia of 12 prism diopters [PD]), 19 patients (23%) showed an esodeviation (from flick esotropia to an esotropia of 6 PD), and there was a vertical component in 54 patients (61%) ranging from flick hypertropia to a hypertropia of 10 PD; the mean total vector deviation was 2.7 PD (SD, 2.7).

A Lancaster red-green test was performed in 45 of the 83 patients (54%). In 23 of these patients (28%), a nonspecific, small, comitant vertical misalignment was documented. Five patients (6%) showed vertical misalignments that were mildly incomitant, but not specific for a single-muscle type of cyclovertical muscle dysfunction. Eight patients (10%) showed a small comitant combined vertical and horizontal misalignment, 2 patients (2%) showed a purely horizontal misalignment, and 2 patients (2%) had horizontal, vertical, and torsional incomitance because of limited eye movements. Two patients (2%) showed a nonspecific torsional component of the misalignment. Three patients (4%) showed no misalignment on the Lancaster red-green test.

Alternate-letter vectographic and stereopsis testing at distance was performed in 70 of the 83 patients (84%). Eleven of these patients (16%) showed fusion with some degree of stereopsis, and the remaining 59 patients (84%) had no fusion or stereopsis. Stereopsis close up was measured in 80 of the 83 patients (96%) using the Randot Stereo test (Stereo Optical, Chicago, IL). Sixty-nine of these patients (83%) showed at least some degree of stereopsis at near, with a mean of 272 arc seconds (SD, 787 arc seconds) for these 69 patients.

All patients had central binocular diplopia (a required symptom to be included in the study). The lights on-off test was performed for 69 of the 83 patients (83%). In each patient, central fusion was demonstrated within a few seconds when the room lights were extinguished (rarely up to 30 seconds). Each patient reported diplopia within seconds after the room lights were turned back on. Five patients (6%) required partial prism correction to achieve central fusion when the lights were turned off (there was still central diplopia with the room lights on). Two patients (2%) required a letter larger than 20/70 to fuse centrally with room lights off. In several cases, even a small green pilot light at the right lower corner of the monitor was noted to be sufficient to stimulate peripheral fusion with the room lights off, leading us to occlude the pilot light for subsequent tests. The single white letter would still be double when the pilot light was showing, and the letter would become single only when the pilot light was covered.

The response to prism trial was recorded in 80 of the 83 patients (96%). In 73 of the 80 patients (91%), the prism trial was carried out in the office. Diplopia was relieved by prism momentarily, but recurred in most patients within 5 to 30 seconds. In 3 of these patients (4%), it recurred after 1 to 2 minutes of prism addition. In the other 7 of the 80 patients (9%), the prism trial was not carried out in the office, but these patients had prisms in their glasses and were still diplopic despite multiple prism changes elsewhere. In the remaining 3 patients (4%) in whom a prism trial was not noted in the record, the diagnosis of dragged-fovea diplopia syndrome was based on the presence of an epiretinal membrane and a positive lights on-off test.

Surface wrinkling retinopathy affecting the macula, or another macular or paramacular lesion, was present visibly by history or examination in 93 of the 95 eyes (98%). The macula had an unremarkable appearance in 2 eyes (2%); however, both patients displayed metamorphopsia on Amsler grid testing. Amsler grid test results showed metamorphopsia in 85 eyes (89%), a scotoma in 2 eyes (2%), and both metamorphopsia and a scotoma in 2 eyes (2%). The Amsler grid test was not performed in the remaining 6 eyes (6%). In these 6 eyes, the diagnosis of dragged-fovea diplopia syndrome was based on other clinical evidence of macular disease in the presence of the typical prism trial failure, a positive lights on-off test, or both. Fluorescein angiography had been performed in 9 eyes (9%) and showed evidence of surface wrinkling retinopathy in 6 of these (67%).

Fifty-three of the 83 patients (64%) had a history of ocular surgery before our examination, as listed in Table 1. Importantly, in 9 of the 27 patients (33%) who had undergone an epiretinal membrane procedure, the diplopia was noted only after surgery. In at least 11 of the 18 patients (61%) who reported diplopia before the membrane peeling procedure, it was documented that the diplopia did not improve after surgery.

Table 1.

Past Ocular Surgeries in Patients before Identification of Epiretinal Membrane, Diagnosis of the Dragged-Fovea Diplopia Syndrome, or Both

Surgery	No. of Patients	% of Total
CE/IOL	40	48
PPV/MP	27	33
Retinal laser procedure	10	12
SB	7	7
PPV	5	6
SB/PPV	2	2
Trabeculotomy	2	2
Transcleral cryopexy	2	2
CE (no IOL)	1	1
SB/PPV/MP	1	1
Total	53	64

CE/IOL = cataract extraction with intraocular lens placement; MP = membrane peeling; PPV = pars plana vitrectomy; SB = scleral buckle.
 Several patients had more than one surgery.

The cause of the maculopathy was unknown in 49 of the 95 eyes (52%) with no history of ocular trauma or ocular surgery at the time the maculopathy was first reported. In 29 of the 95 eyes (31%), symptoms developed that were attributable to the development of an epiretinal membrane after ocular surgery. The maculopathy occurred after trauma or was attributable to retinal disease other than epiretinal membranes in 17 of the 95 eyes (18%). Table 2 details the known or unknown cause of the maculopathy for all 83 patients.

Table 2.

Causes of the Dragged-Fovea Diplopia Syndrome

Cause	No. of Patients	% of Total
Idiopathic epiretinal membrane	49	52
Ocular surgery	29	31
CE/IOL	20	21
Retinal laser surgery	11	12
SB	9	9
Transscleral cryoplexy	2	2
Trauma	8	8
Other retinal disease	9	9
AMD	4	4
Central serous choroidopathy	3	3
Choroidal melanoma	1	1
CNVM secondary to histoplasmosis	1	1

AMD = age-related macular degeneration; CE/IOL = cataract extraction with intraocular lens placement; CNVM = choroidal neovascular membrane; SB = scleral buckle.
 Several patients had more than one surgery before diagnosis.

Table 3 summarizes typical history and clinical signs suggestive of the dragged-fovea diplopia syndrome.

Table 3.

Typical History and Clinical Signs Suggestive of the Dragged-Fovea Diplopia Syndrome

Clues in the patient’s history suggesting the dragged-fovea diplopia syndrome

Small-angle binocular diplopia accompanied by

1. Metamorphopsia

2. History of epiretinal membrane(s)

3. Any history of ocular surgery, especially with retinal involvement

4. Trouble identifying the best prismatic correction

5. A history of constant dissatisfaction with prism correction, leading to gradually increasing prism power

Signs in the examination suggesting or supporting the diagnosis of the dragged-fovea diplopia syndrome

1. Small-angle comitant strabismus, usually with a vertical component

2. Metamorphopsia in one or both eyes on Amsler grid testing

3. Resolution of diplopia from added prism, but recurrence within seconds to minutes

4. Fusion of a small luminous target in a totally dark room, with central diplopia within seconds when the lights are turned on (the “lights on-off test”)

Eye muscle surgery was performed on 3 of the 83 patients (4%) because of comitant large-angle strabismus with diplopia. The diagnosis of dragged-fovea diplopia syndrome was made before strabismus surgery in 2 of these patients. These patients noted an improvement in the angle of diplopia after strabismus surgery because the images were closer together, but the diplopia was not eliminated completely.

The response to monocular occlusion with a piece of Scotch Satin tape (3M Co., St. Paul, MN) was documented in 58 of the 83 patients (70%). In 46 of these patients (87%), diplopia was relieved effectively using this method and the patients felt comfortable. Twelve patients (13%) did not tolerate the monocular occlusion because they were bothered by the resulting blurred vision in the affected eye, even though the diplopia was eliminated. In 6 patients, a Bangerter foil was used to occlude the affected eye, and in 19 patients (23%), no treatment was given or was believed to be necessary.

In the cases of the few patients (9/83; 11%) who returned since their diagnosis, subsequent examinations recorded the continued presence of central diplopia, except when the vision decreased in the affected eye because of the development of cataract or progression of the epiretinal membrane.

Discussion

Patients with foveal dragging secondary to retinal disease can experience central binocular diplopia from competition between central and peripheral fusion.^{2, 3, 4, 5, 6, 7, 8 and 11} The average age of our patient population was 67 years, consistent with the fact that epiretinal membranes and other similar retinal diseases associated with foveal distortion are more common in the older age range.¹

It seems that for central diplopia to be symptomatic, visual acuity in the affected eye must be reasonably good. In fact, best-corrected visual acuity was 20/40 or better in 88% of the affected eyes in our study. Previous reports of what we are calling the dragged-fovea diplopia syndrome have described this problem only in patients with visual acuities better than 20/50.^{2, 3, 4, 5 and 8} Patients with severe macular disease, with moderate to severe visual impairment, seem less likely to note central diplopia. Interestingly, in a study of patients with diabetic retinopathy, Bresnick et al¹² reported no diplopia in patients with retinal wrinkling and visual acuity between 20/15 and 20/40, although all of these patients reported metamorphopsia. Presumably, there was not enough foveal dragging in these cases of retinal wrinkling to produce diplopia. Patients with retinopathy of prematurity with macular dragging also have dragging of larger portions of the retina, but generally do not have diplopia because of long-standing suppression.

Even though diplopia has been described in several studies as one of the symptoms of epiretinal membranes or maculopathy, it is not recognized as a common finding in this problem. Neither the incidence nor the prevalence has been reported. Dragged-fovea-induced diplopia was present in 83 of our initial 222 patients who had a diagnosis of epiretinal membrane, dragged fovea, or internal limiting membrane. However, we cannot estimate the incidence of diplopia in patients with maculopathy because our patient population is biased toward diplopia problems. Patients referred to our practice usually have diplopia or strabismus in addition to the retinal disease, and therefore patients with binocular diplopia secondary to macular disease are undoubtedly overrepresented in our sample. It is also possible, however, that these patients have been underdiagnosed in the past and now are being identified and referred more frequently.

Bixenman and Joffe⁴ described 4 patients with retinal wrinkling and diplopia. They postulated that spontaneous or surgical separation of the epiretinal or preretinal membrane may lessen retinal distortion enough to allow reestablishment of the normal relationship between central and peripheral fusion. It is interesting to note that in 11 of our patients who had reported diplopia before a membrane peeling procedure, the diplopia did not improve after the procedure. Persistent or permanent retinal distortion, despite relief of retinal surface traction, could explain this observation. In 9 of our patients who had an epiretinal membrane peeling procedure, diplopia was noted only after the surgery. This was likely because visual acuity improved in the operated eye and the second image became more obvious.

Retinal distortion also can occur when the retina settles after retinal detachment. Apparently subtle changes in retinal architecture can cause minute foveal displacement that results in central versus peripheral misalignment, with symptomatic central diplopia, despite a grossly normal macular appearance.

In most of our patients, the macular condition associated with diplopia was an epiretinal membrane of varying severity. Previous studies have reported the occurrence of central diplopia secondary to parafoveal lesions,² subretinal neovascular membranes,³ epiretinal membranes (or cellophane maculopathies),^{4 and 8} macular dystrophy,¹¹ or central serous chorioretinopathy.¹³ Intraretinal or subretinal fibrosis also can distort and pull the fovea away from its natural position. Patients who undergo limited macular translocation surgery also can report diplopia.¹⁴ In this setting, the diplopia often is more peripheral than central. In these patients, the presence of central suppression, or of a foveal scotoma or blur in one or both eyes, usually precludes perception of central diplopia. Prisms can eliminate the peripheral diplopia in some of these patients.¹⁴

The symptomatic diplopia in the dragged-fovea diplopia syndrome more commonly is vertical or oblique, although we have seen a small number of patients with pure horizontal diplopia, or torsional diplopia. We presume that this is because Panum’s fusional areas are wider horizontally than vertically, and small horizontal displacements of one fovea therefore would not be expected to cause significant conflict between central and peripheral fusion. Only occasionally did we go through the exercise of correlating the anatomic direction of foveal dragging with the subjective localization of the second image, but when we did, the direction seemed to be appropriate.

We usually did not measure aniseikonia formally, but 18 patients in our study reported that the image in the affected eye was either smaller or larger. On occasion, size lenses were held before one eye or the other until, on cross cover testing, the central images appeared equal. When the patient commented on image size difference accompanying macular pucker, the measured amounts of image size difference usually were in the range of 8% to 15%. It has been suggested that aniseikonia can contribute to central fusion instability in patients with macular distortion and thus can contribute to the development of central binocular diplopia. Benegas et al¹⁵ reported 7 patients with macular disease, aniseikonia, and diplopia. Aniseikonia was attributed to macular disease in these patients in the absence of significant anisometropia. The authors hypothesized that, rather than a cause-and-effect relationship between aniseikonia and diplopia, there is probably an additive contribution of the aniseikonia and the metamorphopsia that leads to fusion instability.

Ocular motility examination may disclose a small-angle misalignment in patients with the dragged-fovea diplopia syndrome, but prism trials in the office are unstable and futile. The diplopia initially disappears immediately when the prism is introduced, only to recur a few seconds or minutes later in the vast majority of cases. Forty-two of our patients had prism in their glasses at presentation. In most cases, the prescribed prism would have been appropriately oriented for treatment of the patient’s diplopia had the diplopia been the result of a true deviation. In our experience, however, prescribing prism in these patients has not been successful, and in several patients, true deviations had developed secondary to peripheral fusion mechanisms as the patients adapted to the prescription of increasing prism. Several patients were referred to our practice after 3 or more prism increases in the previous year. The referring practitioners noted that each time the adjustment would seem to relieve the diplopia enough to warrant changing the prescription, but inevitably within days to weeks the patient would return with the same symptoms.

As soon as the diagnosis of the dragged-fovea diplopia syndrome has been confirmed, patients often can be weaned off of their current prism prescription slowly, if they desire. Eye muscle surgery also can be considered if true strabismus has been caused by adaptation to increasing prism, but the patients must understand that the surgery will not correct the central diplopia; it will only rid them of the need for prism.

Practically all patients who had an Amsler grid test showed evidence of foveal distortion or macular involvement. Only rarely has this syndrome been described without symptomatic metamorphopsia or Amsler grid abnormalities. Two of the 5 patients reported by Bixenman and Joffe⁴ did not have metamorphopsia in the affected eye. Metamorphopsia in patients with milder degrees of retinal wrinkling may be difficult to identify, but all but one of our patients tested reported varying degrees of metamorphopsia. This suggests that symptomatic diplopia is more common when the degree of retinal distortion is enough to be notable on Amsler grid testing.

Intractable diplopia from acquired central disruption of fusion can occur after head trauma, midbrain lesions, or prolonged visual deprivation.^{16, 17, 18 and 19} In this scenario, the patient experiences constant diplopia in all positions of gaze, usually somewhat incomitant, that cannot be relieved except fleetingly in any direction of gaze with prisms. In contrast to the dragged-fovea diplopia syndrome, these patients do not have symptoms or clinical evidence of macular disease, and there is no sign of conflict between central and peripheral fusion mechanisms secondary to anatomic displacement of one or both of the foveas.

The relationship between central and peripheral fusion has been analyzed in the past. The synoptophore has been used previously to confirm the conflict between central and peripheral fusion produced by the displaced fovea.^{3 and 4} We instead have used our lights on-off test most commonly in our patients. When the room lights are turned off, these patients see the white 20/70 letter singly, as central fusion is the acting feedback mechanism for motor alignment under these conditions, and fusional vergence will align the corresponding foveal areas. With the room lights on, binocular vision is dominated by the stronger peripheral fusion mechanisms, which then supply the primary feedback for motor alignment. Experiments in the past have shown that peripheral retinal stimuli are strong enough to break central fusion mechanisms and thus central alignment,^{20 and 21} and this seems to be the mechanism involved here.

If there are already more than several PD of prism present in the glasses, the patient usually must wear these glasses, to which he or she has adapted, for the lights on-off test to demonstrate central fusion in the dark. If these glasses are removed, then peripheral fusion is stressed somewhat, and central fusion is stressed all the more. We also noted that in 5 patients, additional prism correction was required to initiate central fusion with the room lights off. The added prism invariably would not maintain central fusion when the room was illuminated again. Interestingly, there was not a correlation between the angle of central diplopia and the necessity of prism to achieve central fusion. The lights on-off test is a simple method that can be used to examine patients with clinical characteristics suggestive of the dragged-fovea diplopia syndrome. If the patient fuses centrally with the room lights totally off, and the central diplopia returns when the room lights are turned on again, the diagnosis of dragged-fovea diplopia is confirmed. To our knowledge, the only other condition that may produce a positive lights on-off test result is a central versus peripheral disparity in rare cases of deep-seated anomalous retinal correspondence.^{22 and 23}

Treatment of the dragged-fovea diplopia syndrome can be frustrating for the patient and the physician because there is no complete cure available. Some patients adapt and learn to ignore the second image. Monocular occlusion in the form of eye patches and Bangerter filters applied to the eyeglasses eliminates the diplopia.¹³ An occluder contact lens on the affected eye is another alternative.²⁴However, these methods are not inconspicuous and often are not tolerated by the patients. We have used a vertical strip of Scotch Satin tape on the rear surface of the spectacle lens of the nonpreferred eye as a form of monocular occlusion (Fig 2B). We have experimented with different placements of the tape, depending on the patient’s reported symptoms. For patients who are most bothered by the diplopia when reading, the tape can be fashioned to occlude only the reading add or progressive power portion of the lens in the nonpreferred eye (Fig 3A). Alternatively, when reading road signs or working at a distance presents the most difficulty, the tape can be fit to the top of the distance portion of the lens so that the patient can learn to drop his or her chin and to look through the top of the glasses when looking in the distance, effectively eliminating the diplopia (Fig 3B). Finally, we have demonstrated to several patients the usefulness of occluding both the lower and upper portions of the lens, while leaving the middle unobstructed (Fig 3C). This combination allows the patient to occlude 1 eye when necessary at either distance or near, yet also to take advantage of any stereopsis he or she may have remaining in straight-ahead gaze. This tape is barely noticeable once applied, and therefore provides a less objectionable alternative for monocular occlusion than more opaque tape such as Scotch Magic tape (Fig 2A), a frosted lens, or an eye patch. Use of the tape avoids the cost of a Bangerter foil and is easily removable. Some patients still do not tolerate the partial occlusion. They are bothered by the blur induced by the tape in the affected eye.

Figure 2. Appearance of Scotch Satin tape versus Scotch Magic tape (3M Co., St. Paul, MN) on rear surface of glasses. A, Patient with Scotch Magic tape, which blocks vision but obscures patient’s eye. B, Patient with Scotch Satin tape, which blocks vision yet allows view of patient’s eye.

Figure 3. Various zone application patterns of tape. For demonstration purposes, Scotch Magic (3M Co., St. Paul, MN) tape was used for these figures. Note that, as in Figure 2, Scotch Satin tape is much less noticeable. A, For patients whose diplopia is only bothersome at near (in down gaze because most patients are in bifocals or progressive power lenses). B, For patients whose diplopia is bothersome only in the distance. C, For patients needing straight-ahead gaze unoccluded to take advantage of remaining depth perception, but occlusion possible at both near (down gaze) and distance (using chin-down head posture for reading distant road signs, for example).

Prescribing monovision glasses also can be considered as a means of eliminating the diplopia in some patients. Adding the necessary reading add to the distance refraction in one eye (usually the nondominant eye is preferable) optically occludes the vision in that eye when the patient is focused at a distance. Similarly, in the presbyopic patient with a monovision prescription, vision in the dominant eye is blurred when reading at near because of a lack of accommodation. In either case, the brain occasionally can learn to ignore the blurred image, although the optical difference between the two eyes often is not enough for the central diplopia to disappear completely. We prescribed monovision glasses in one patient by adding a +2.50 sphere to his distance refraction in his nondominant eye, with acceptable results. It is advisable to demonstrate the effects of monovision in trial frames before prescribing, given the difficulty that some patients have adjusting to switching eyes.

Epiretinal membrane surgery to improve the diplopia by releasing the tractional forces that displace the fovea has been contemplated,¹⁴ but predictable success of such surgery in relieving the dragged-fovea diplopia syndrome has not yet been demonstrated. Twenty-three of our 83 patients had a prior history of membrane peeling surgery. Our patient population would have been biased toward those whose diplopia was not relieved with membrane peeling surgery. However, of the 14 patients who had undergone membrane peeling surgery after reporting diplopia associated with an epiretinal membrane, 11 reported little or no improvement in their diplopia after the procedure. For the other 9 patients, epiretinal membrane peeling surgery unmasked or precipitated the development of the dragged-fovea diplopia syndrome. Retinal surgeons should not assume, therefore, that epiretinal membrane peeling surgery will eliminate the diplopia and ought to be aware of unresolvable central diplopia as a potential outcome.

The dragged-fovea diplopia syndrome can frustrate both patients and clinicians when undiagnosed. However, once suspected, it can be easily diagnosed using the lights on-off test, and several options for symptomatic treatment exist, although none at this time can relieve the patient completely of the diplopia. Early diagnosis is important to prevent needless prism glasses prescription and the development of true strabismus secondary to the unnecessary prism. The lights on-off test provides the patient and clinician with a convincing demonstration of the cause of the problem, resolves the diagnostic dilemma, and leads to an informed discussion of treatment options.

References

1 R. Klein, B.E. Klein, Q. Wang and S.E. Moss, The epidemiology of epiretinal membranes, Trans Am Ophthalmol Soc 92 (1994), pp. 403–425 discussion 425–30.

2 R.A. Crone, Diplopia. Amsterdam Excerpta Medica (1973), pp. 410–411.

3 D. Burgess, G. Roper-Hall and R.M. Burde, Binocular diplopia associated with subretinal neovascular membranes, Arch Ophthalmol 98 (1980), pp. 311–317. View Record in Scopus | Cited By in Scopus (10)

4 W.W. Bixenman and L. Joffe, Binocular diplopia associated with retinal wrinkling, J Pediatr Ophthalmol Strabismus 21 (1984), pp. 215–219. View Record in Scopus | Cited By in Scopus (9)

5 B.J. Kushner, M.G. Alvares and E.A. Paysse et al., Grand rounds #53 a case of small angle strabismus, torsion, aniseikonia, and diplopia associated with epiretinal membranes, Binocul Vis Strabismus Q 14 (1999), pp. 46–51 discussion 51–2.

6 B. Schroeder, T. Krzikok, H. Kaufmann and P. Kroll, Disturbances of binocular vision in macular heterotopia, Klin Monatsbl Augenheilkd 215 (1999), pp. 135–139 [in German]. View Record in Scopus | Cited By in Scopus (3)

7 D.L. Guyton, The dragged-fovea diplopia syndrome. In: R.J. Balkan, G.S. Ellis Jr and H.S. Eustis, Editors, At the Crossings Pediatric Ophthalmology and Strabismus. Proceedings of the 52nd Annual Symposium of the New Orleans Academy of Ophthalmology, Kugler Publishers, The Hague (2004), pp. 167–172 New Orleans, LA, February 14–16, 2003.

8 J.J. Barton, “Retinal diplopia” associated with macular wrinkling, Neurology 63 (2004), pp. 925–927. View Record in Scopus | Cited By in Scopus (3)

9 J.T. Holladay and T.C. Prager, Mean visual acuity, Am J Ophthalmol 111 (1991), pp. 372–374 [letter]. View Record in Scopus | Cited By in Scopus (114)

10 J.T. Holladay, Proper method for calculating average visual acuity, J Refract Surg 13 (1997), pp. 388–391. View Record in Scopus | Cited By in Scopus (125)

11 H. Steffen, F.G. Holz and G.H. Kolling, Macular dystrophy as a retinal model of fixation disparity, Strabismus 4 (1996), pp. 179–184. View Record in Scopus | Cited By in Scopus (1)

12 G.H. Bresnick, B. Haight and G. de Venecia, Retinal wrinkling and macular heterotopia in diabetic retinopathy, Arch Ophthalmol 97 (1979), pp. 1890–1895. View Record in Scopus | Cited By in Scopus (5)

13 M. Silverberg, E. Schuler and S. Veronneau-Troutman et al., Nonsurgical management of binocular diplopia induced by macular pathology, Arch Ophthalmol 117 (1999), pp. 900–903. View Record in Scopus | Cited By in Scopus (4)

14 A.N. Buffenn, E. de Juan, G. Fujii and D.G. Hunter, Diplopia after limited macular translocation surgery, J AAPOS 5 (2001), pp. 388–394. Abstract | View Record in Scopus | Cited By in Scopus (8)

15 N.M. Benegas, J. Egbert, W.K. Engel and B.J. Kushner, Diplopia secondary to aniseikonia associated with macular disease, Arch Ophthalmol 117 (1999), pp. 896–899. View Record in Scopus | Cited By in Scopus (16)

16 J.A. Sharkey and P.W. Sellar, Acquired central fusion disruption following cataract extraction, J Pediatr Ophthalmol Strabismus 31 (1994), pp. 391–393. View Record in Scopus | Cited By in Scopus (22)

17 M.C. Lee, Acquired central fusional disruption with spontaneous recovery, Strabismus 6 (1998), pp. 175–179.

18 J.A. Pratt-Johnson and G. Tillson, The loss of fusion in adults with intractable diplopia (central fusion disruption), Aust N Z J Ophththalmol 16 (1988), pp. 81–85. View Record in Scopus | Cited By in Scopus (7)

19 J.A. Pratt-Johnson and G. Tillson, Acquired central disruption of fusional amplitude, Ophthalmology 86 (1979), pp. 2140–2142. View Record in Scopus | Cited By in Scopus (4)

20 H.M. Burian, Fusional movements role of peripheral retinal stimuli, Arch Ophthlamol 21 (1939), pp. 486–491.

21 H.M. Burian, Fusional movements in permanent strabismus, Arch Ophthalmol 26 (1941), pp. 626–652.

22 H.G. Bredemeyer and K. Bullock, A case of coexisting normal and abnormal retinal correspondence, Br Orthopt J 25 (1968), pp. 94–96.

23 R.A. Crone, L. van de Gaer and E.L. Bonants, Spontaneous foveal diplopia with peripheral fusion The coexistence of two angles of anomaly. Consequences for the theory of abnormal retinal correspondence, Arch Ophthalmol 84 (1970), pp. 143–147. View Record in Scopus | Cited By in Scopus (3)

24 D.S. Burger and R. London, Soft opaque contact lenses in binocular vision problems, J Am Optom Assoc 64 (1993), pp. 176–180. View Record in Scopus | Cited By in Scopus (10)

Manuscript no. 2004-228.Supported in part by the Judith and Paul Romano Fellowship Fund and the Stewart M. Wolff Fellowship Fund, both established by the respective donors within the Krieger Children’s Eye Center for support of research by fellows.The authors have no financial conflict of interest in the article’s publication.
Correspondence to David L. Guyton, MD, The Wilmer Institute, 233, The Johns Hopkins Hospital, 600 North Wolfe Street, Baltimore, MD 21287-9028