Background
Diplopia is the subjective complaint of seeing two images instead of one and is often referred to as double-vision in lay parlance. [1] The term diplopia is derived from two Greek words: diplous, meaning double, and ops, meaning eye. Diplopia often is the first manifestation of many systemic disorders, especially muscular or neurologic processes. [1, 2] An accurate, clear description of the symptoms (eg, constant or intermittent; variable or unchanging; at near or at far; with one eye [monocular] or with both eyes [binocular]; horizontal, vertical, or oblique) is critical to appropriate diagnosis and management. [1, 3, 4]
Binocular diplopia occurs only when both eyes are open and can be corrected by covering either eye. Monocular diplopia persists in one eye despite covering the other eye and usually can be corrected by using a pinhole. Monocular diplopia can be unilateral or bilateral. [1] Physiologic diplopia is a normal phenomenon depending on the alignment of the ocular axes with the objects of regard (eg, focusing on a finger held close results in distant objects being blurry but double).
Further classification schemes for binocular diplopia include constant versus intermittent and vertical versus horizontal (or oblique) diplopia. Vertical diplopia indicates vertical alignment of the images, which usually suggests pathology in the vertical muscles, including superior oblique, inferior oblique, superior rectus, and inferior rectus. Horizontal diplopia suggests pathology of the medial or lateral rectus.
Animal models
Unless the visual fields of the eyes overlap, binocular diplopia cannot occur. Among vertebrates, the potential for diplopia (and for stereoscopic depth perception) depends on where the eyes are located in the head. Eyes located on either side of the head provide a wide visual field but with a less overlapped visual field. These animals have less field for binocular vision and less risk for diplopia when one eye becomes misaligned. However, when both eyes are located in the front of the head, a greater visual field overlap exists and, thus, a better binocular depth perception, as frequently seen in predators. Misalignment of such eyes may result in diplopia.
The eyes of birds demonstrate many unique anatomic features, one of which is the presence of multiple foveae and, in some cases, a streak fovea linking two foveae. Thus, they may be able to have two separate areas of regard without disabling diplopia. How the visual perception occurs in these cases remains debatable.
Pathophysiology
Binocular diplopia (or true diplopia) is a breakdown in the fusional capacity of the binocular system. The normal neuromuscular coordination cannot maintain correspondence of the visual objects on the foveae of the two eyes. Rarely, fusion cannot occur because of dissimilar image size, which can occur after changes in the optical function of the eye after refractive surgery (eg, LASIK) or after a cataract is replaced by an intraocular lens or because of aniseikonia, which represents a discrepancy in image size perceived by the two eyes.
The distortion of one image may be interpreted as diplopia by the patient; however, the same object does not appear to be in two places but rather appears differently with each eye.
Monocular diplopia may result from abnormal light transmission to the retina (eg, corneal distortion or scarring, multiple openings in the iris, cataract or subluxation of the natural lens or pseudophakic lens implant, vitreous abnormalities, retinal conditions). Monocular diplopia must be distinguished from metamorphopsia, in which objects appear misshapen. [1]
Epidemiology
Frequency
United States
From 2003 through 2012, there were 804,647 ambulatory and 49,790 emergency department visits annually for diplopia. Most ambulatory visits occurred with ophthalmologists (70.4%), and diplopia was frequently the primary reason for ambulatory setting (48.6%) or emergency department (36.5%) visits. [5]
International
International incidence rates of diplopia are unknown. The incidence of diplopia as a chief complaint in emergency departments is low. One study of a specialist eye hospital in London, United Kingdom, reported the incidence of diplopia as the chief complaint in only 1.4% of the presenting cases. [6]
Mortality/Morbidity
Divergent pathologic processes, each with its own morbidity and mortality, can cause diplopia. However, irrespective of cause, diplopia has significant morbidity in terms of difficulty with depth perception and confusion with orientation of objects, especially when performing visually demanding tasks, such as driving a vehicle or operating tools. Therefore, in assessing visual disability after injuries, loss of binocularity accounts for a major percentage of loss of function.
Race
Diplopia has no reported racial predilection.
Sex
Diplopia has no reported sexual predilection.
Age
Diplopia is encountered almost exclusively in adults or in those with mature visual systems because of their inability to ignore the second image.
Young children may not be able to express this symptom. More importantly, the immature visual system deals with diplopia by suppressing the poorer image, possibly resulting in irreversible amblyopia. Children with obvious and marked ocular malalignment due to strabismus are comfortable and content because the visual image from the deviating eye is suppressed and not noticed.
Prognosis
The causes of diplopia can vary from a mild inconvenience to a condition with major health consequences. [1]
As a rule, patients with diabetic mononeuritis multiplex recover spontaneously in approximately 6 weeks.
Optical causes (eg, lens dislocation, corneal disorders) are amenable to repair.
Blow-out fractures have a variable prognosis depending on the amount of tissue damage.
Central (neurologic) causes of diplopia can have serious consequences and, in the case of primary or secondary tumors, have a dire prognosis.
Patient Education
Patients must be educated on the importance of determining the exact cause of diplopia, since some conditions responsible for diplopia may be very serious. Otherwise, a clear explanation of the condition, its natural history, alternative options, and general prognosis will alleviate patient concerns and motivate perseverance. [7]
For excellent patient education resources, visit eMedicineHealth's Eye and Vision Center. Also, see eMedicineHealth's patient education article Black Eye.
Tables
Medication |
Risk for diplopia |
Lacosamide |
Very common (≥1/10) |
Zonisamide |
Very common (≥1/10) |
Eslicarbazepine |
Common (≥1/100 to < 1/10) |
Botulinum toxin |
Common (≥1/100 to < 1/10) |
Rufinamide |
Common (≥1/100 to < 1/10) |
Pregabalin |
Common (≥1/100 to < 1/10) |
Perampanel |
Common (≥1/100 to < 1/10) |
Temozolomide |
Common (≥1/100 to < 1/10) |
Zicotinamide |
Common (≥1/100 to < 1/10) |
Sildenafil |
Common (≥1/100 to < 1/10) |
Gabapentin |
Common (≥1/100 to < 1/10) |
Topiramate |
Common (≥1/100 to < 1/10) |
Zaleplon |
Uncommon (≥1/1000 to < 1/100) |
Levetiracetam |
Uncommon (≥1/1000 to < 1/100) |
Bortezomib |
Uncommon (≥1/1000 to < 1/100) |
Amlodipine |
Uncommon (≥1/1000 to < 1/100) |
Adalimumab |
Uncommon (≥1/1000 to < 1/100) |
Pravastatin |
Uncommon (≥1/1000 to < 1/100) |
Lamotrigine |
Uncommon (≥1/1000 to < 1/100) |
Capecitabine |
Uncommon (≥1/1000 to < 1/100) |
Telithromycin |
Rare (≥1/10000 to < 1/1000) |
Voriconazole |
Rare (≥1/10000 to < 1/1000) |
Dextromethorphan/Quinidine |
Rare (≥1/10,000 to < 1/1000) |
Sertraline |
Rare (≥1/10,000 to < 1/1000) |
Ciprofloxacin |
Rare (≥1/10,000 to < 1/1000) |
Table. Drugs Associated with Diplopia |
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