|Year : 2007 | Volume
| Issue : 2 | Page : 79-80
Intractable diplopia following monocular patching
Arif O Khan
Pediatric Ophthalmology and Strabismus Division, King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia
|Date of Web Publication||11-Nov-2009|
Arif O Khan
King Khaled Eye Specialist Hospital, PO Box 7191, Riyadh 11462
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Although acquired strabismus in a visually mature adult typically causes double vision, this diplopia usually resolves if the eyes are realigned because of the patient's previous ability to fuse. In some adults, however, acquired strabismus and diplopia are secondary to a loss of fusional ability. Such patients can suffer from intractable diplopia, which is often more symptomatic if vision is improved and/or if the eyes are realigned. An illustrative case is presented and discussed.
Keywords: intractable diplopia, fusion loss, acquired strabismus
|How to cite this article:|
Khan AO. Intractable diplopia following monocular patching. Middle East Afr J Ophthalmol 2007;14:79-80
Although acquired strabismus in a visually mature adult typically causes double vision, this diplopia usually resolves if the eyes are realigned because of the patient's ability to fuse. In some adults, however, acquired strabismus and diplopia are secondary to a loss of fusional ability , ; such patients can suffer from intractable diplopia, which is often more symptomatic if vision is improved and/or if the eyes are realigned. An illustrative case is presented and discussed.
| Case Report|| |
A 24-year-old male without prior ocular or medical history suffered multiple deep left periorbital skin lacerations following a motor vehicle accident. There was no ocular injury. Surgical repair was performed, with some wounds left open for healing by secondary intention. The patient noted that his vision with both eyes open during his hospitalization was normal. At the time of hospital discharge, a dressing was placed over the left periorbital skin (and thus over the left eye). The patient kept the eye continuously covered, except for a brief period when he changed the dressing every 3 to 4 days. One month after hospital discharge, he noted diplopia while he was changing his dressing. Three months after hospital discharge, the dressing was discontinued, and the patient complained of exotropia, diplopia, and left-eye photophobia. An ophthalmologist diagnosed herpetic keratitis in the left eye and prescribed a course of acyclovir ophthalmic ointment. After this treatment, the photophobia resolved, but the patient still complained of constant diplopia.
Eighteen months after his hospital discharge, he was evaluated for his constant diplopia, which remained unchanged. Uncorrected visual acuity was 20/20 in the right eye and 20/50 in the left eye. Scarring of the skin around the left eye was evident; ophthalmic examination was significant for a 35 prism diopter comitant exotropia and a faint central disciform subepithelial scar in the left cornea [Figure 1]. There was no duction limitation, and the anterior segment examination was otherwise unremarkable. Examination of intraocular pressure, pupils, convergence amplitudes, accommodative amplitudes, and posterior pole of the fundus was unremarkable. Manifest refraction was plano in the right eye and +1.50 -4.75x095 in the left eye. The patient tolerated contact lens correction in his left eye, with his vision improving to 20/30; however, he did not prefer to correct his left eye optically because it made his diplopia more obvious. Despite using prisms in free space to compensate for his exotropia, the patient could not fuse the 2 images-he described the 2 images as superimposed over one another, with the second image bobbing around the first one. The patient described the same phenomenon when a major amblyoscope (Synoptophore, Clement Clarke International Ltd., Essex, United Kingdom) was used to compensate for his strabismus. After a long discussion regarding the likelihood that his diplopia would persist and probably become more bothersome with the 2 images being closer together after strabismus surgical correction, the patient decided not to undergo strabismus surgery.
| Discussion|| |
Acquired loss of fusional ability, a rare phenomenon without known neuroanatomical correlate, has been associated with central and peripheral causes.  When the cause is central, the usual association is an antecedent closed head trauma , ; however, when diplopia occurs after a closed head trauma, one must first consider more common acquired etiologies, such as cranial nerve palsy, convergence insufficiency, and accommodative insufficiency. ,, When the cause for loss of fusional ability is peripheral, the etiology is typically acquired unilateral sensory deprivation from patching, cataract, or uncorrected aphakia. ,,, Most patients who undergo unilateral patching do not experience loss of fusional ability; those who do likely had a significant preexisting phoria ,, or monofixation syndrome.  Similarly, most patients with unilateral acquired cataract or uncorrected aphakia do not lose their ability to fuse; those who do tend to have had unilateral visual deprivation for at least 2 1/2 years (and also likely had preexisting phoria ,, or monofixation syndrome  ).
Patients with acquired loss of fusional ability and intractable diplopia characteristically can appreciate only momentary superimposition of images when their strabismic deviation is neutralized by prisms in free space or by a major amblyoscope. Despite optical neutralization of their strabismus, such patients typically remain diplopic and describe the second image as bobbing around the first.  Surgical correction of strabismus often makes them more symptomatic than they were before strabismus surgery, as the second image is brought closer to the first and becomes more difficult to ignore.  Aggressive orthoptic treatment (over years) with optimal optical correction that minimizes anisokonia may restore fusion in some patients.  However, the overall prognosis for restoration of single binocular vision is guarded. ,,, Ophthalmologists should have a careful discussion with patients at risk for having intractable diplopia before proceeding with eye or eye muscle surgery.
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