Key points
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Be aware of a combination of mechanical, neurogenic, and sensory causes of diplopia.
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Check for factors influencing the absence of diplopia, such as trauma-related visual problems, abnormal head posture, or preexistent strabismus.
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The severity of the trauma does not always correlate with the impairment of motility or with the degree of diplopia.
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Always prescribe monocular eye movement therapy.
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Treat patients in the first period after trauma with press-on prisms or different types of occlusion, and plan follow-ups as is deemed necessary according to the diagnosis.
Introduction
Orbital fractures are common in facial trauma and are reported in as many as 40% of craniofacial trauma. There is no real consensus with regard to standardized examination or protocolled treatment to determine either the necessity or type of treatment. Surgical indication, meaning possible orbital repair surgery, is predicated on criteria, such as enophthalmos, restriction of extraocular muscles, type and size of the fracture’s defect, degree of diplopia, and clinicoradiological findings.
Type of diplopia
Disturbances in ocular motility in orbital fractures may have different causes, but, typically, the diplopia is incomitant in pattern. Incomitant strabismus causing the diplopia is complex; the deviation is different in the various gaze positions. This makes the choices in multifaceted treatment complex.
Medial wall and orbital floor fractures are the most common fractures. Medial wall fractures often give rise to horizontal diplopia. Vertical diplopia is reported more frequently and a common symptom in orbital floor fractures (Case 1) ( Fig. 1 ). In a majority of cases, this leads to a limitation of elevation and in a lesser degree to limitation of depression. ,
Mechanisms causing diplopia in orbital fractures
Strabismus resulting in diplopia may occur in 88% of the patients with orbital fractures. The cause of strabismus may be diverse, often involving multiple mechanisms. One of the causes may lie outside of the orbit due to damage to one of the cranial ocular motor nerves or central/peripheral damage due to contrecoup effect of the brain (stem). Acquired neurogenic palsies frequently are seen in head trauma. Because the fourth nerve is one of the longest of cranial nerves, it is the most vulnerable of the 3 cranial nerves involved in eye movements (third, fourth, and sixth).
Another cause of strabismus may be damage to the ocular muscle itself: swelling, hemorrhage, or even incarceration of the muscle, although actual entrapment of the muscle is uncommon and seen only in posterior floor fractures. Strabismus is not necessarily caused by damage to the ocular muscle itself; it may be due partly to the herniation of orbital fat and connective tissue into the surrounding sinus with subsequent traction on the muscle sheaths.
There also might be a combination of paralytic and mechanical damage causing strabismus as well as a sensory cause, meaning that a change in visual acuity disrupts binocular functioning or even decompensation of preexisting strabismus . Be aware of a combination of mechanical, neurogenic, and sensory causes of diplopia.
Role of orthoptic examination
To assess which of the mentioned mechanisms, discussed previously, is causing diplopia, it is essential to incorporate an orthoptic examination in the initial referral patterns. Unfortunately, only a few articles regarding orbital fractures include a quantitative (orthoptic) evaluation of ocular motility. , , , Not all patients present themselves with typical patterns of diplopia and there is no significant relation between the severity of injury and eventual ocular motility outcome (Case 1). , Diplopia not always is the first concern of patients, initially noticed, or observed at all. Preexisting strabismus and suppression can be reasons for atypical presentation (Case 2). Suppression is an alteration in visual perception that prevents one of the images to be consciously seen. This results in the absence of diplopia in the presence of strabismus. Other reasons of absence of diplopia are visual field defects, macular problems, vision loss, and neglect. The severity of the trauma does not always correlate with the impairment of motility or with the degree of diplopia.
Timing and frequency of orthoptic examination
There is overall agreement on the necessity of sequential measurements over the first 4 months to 6 months in the presence of acquired orthoptic abnormalities. In cases of a neurogenic cause, spontaneous improvement may occur over a time period of 6 months to 9 months. Strabismus secondary to ophthalmologic abnormalities might resolve as vision increases; decompensated strabismus also might resolve spontaneously. Residual diplopia in conservatively treated patients is reported globally, with a significant range, from 15% to 82%.
Independent of the type of injury, the strabismus is likely to change in the first weeks to months as edema resolves (Case 3); 7 days to 10 days after trauma, examination is performed more easily because the initial edema often is resolved partially or mostly. Through orthoptic examination, it can be determined if and to what degree diplopia is improved spontaneously and orbital reconstruction may be prevented. One study of Gosse and colleagues found no correlation between the type of incomitance and the likelihood of spontaneous recovery; thus, care must be taken in formulating a prognosis in the early stages after trauma.
Strabismus also may occur secondary to orbital reconstruction; an orthoptic examination is advised prior to orbital surgery in cases of suspicion of orthoptic abnormalities to document possible change. In cases of iatrogenic causes of diplopia after orbital reconstruction, orthoptic evaluation is strongly suggested. The motility post–orbital surgery can change over a period of time up to 9 months, so continued follow-up is recommended.
Orthoptic follow-up may lead to different conclusions than primary orbital surgical outcome or may even lead to decisions of further surgery, such as strabismus surgery.
Additionally, it is important to state that after a proper diagnosis, only those with complaints have to be followed-up on.
Orthoptic assessment is important and may play a crucial role in decision making. Each patient must be evaluated individually, however, and the leading practitioner must decide the necessity of orthoptic evaluation based on presentation, severity of trauma, and complaints during the treatment process to avoid excessive examination.
Children
In cases of an orbital trauma under the age of 8 years, there is a substantial risk for amblyopia. Especially in long-standing strabismus, suppression can arise, which eliminates diplopia but may lead to amblyopia (impaired/delayed visual development, which is permanent if not treated on time). If an orthoptic examination in adults is elective and based on the judgment of the leading physician, an orthoptic examination in a child with orbital fracture(s) is mandatory, at least at some point during the treatment period.
Choice of orthoptic examination
Taking history, general impression, and ophthalmologic examination
Patients with orbital trauma often present with periorbital ecchymosis, periocular edema, hemorrhage, enophthalmos, and/or proptosis. When assessing a patient with orbital trauma and possible ocular injury, it is important to determine which ocular structure(s) may be involved. It is imperative to determine whether the injury involves only the orbit or whether the injury may involve the bulb, optic nerve, retina, or other ophthalmic structures. Ocular injury may be indicated by a patient report of monocular diplopia; thus, it is important to distinguish this from binocular diplopia ( Box 1 ). When double vision persists on closing 1 eye, there also is at least monocular diplopia requiring further ophthalmologic examination.
| Monocular Diplopia | Binocular Diplopia |
|---|---|
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Ocular injury, orbital and retrobulbar hemorrhage, optic nerve damage, retinal injuries, and penetrating eye trauma all constitute ophthalmic emergencies that may threaten vision and require an immediate consult with an ophthalmologist. Previous studies have found rates of ocular injury in the context of orbital fractures in the range of 26% to 40%. Ocular trauma is further discussed in detail in Gijsbert J. Hötte and Ronald O.B. de Keizer, article “ Ocular injury and emergencies around the globe ,” in this issue.
It is important to be aware of an abnormal head posture (AHP). The advice is to exclude possible preexisting strabismus, which may be the cause of the AHP. An adopted AHP may mask strabismus and may downplay the extent of complaints. A head posture abnormality may be subtle and easily missed. Be aware of factors influencing the absence of diplopia such as trauma related visual problems, AHP, or preexisting strabismus.
Binocular single vision
Binocular single vision (BSV) is a unique quality, a combination of 2 images of the same size, color, brightness, and focus to be projected on identical places in both retinae. It is preferable to test the quality of BSV in a natural testing environment, on near or distance fixation. In cases of absent diplopia but present strabismus, regular examinations often are used to determine further treatment cannot be interpreted as normally would be cone. It thus is imperative to determine the extent of binocular function in patients.
Superimposition
In patients with diplopia, the first impression of the capacity of BSV is to adjust horizontal and/or vertical prisms held in front of the patient’s eyes ( Fig. 2 ) in that specific amount in which the patients achieves a single image. This aspect of BSV is called superimposition. Be aware of any possible disruption of superimposition or fusion, such as macular off detachment or cyclotorsion (tilted image).
Fusion
When superimposition is reached, fusion measurement gives the investigator information about the quality of BSV. Increasing amounts of prisms (see Fig. 2 ) are held in front of a patient’s eye. The patient’s binocular system corrects double vision until a threshold is reached in which the maximum amount of fusion is determined and the patient perceives a double image. The total amount of prisms is called the fusion range. With knowledge about the horizontal and vertical fusional amplitude (range), (Fresnel) prisms can be prescribed to create single vision and to minimize the use of the total fusion ability and thus minimize complaints. A good capacity of fusion is a positive prognostic factor in patients prior to strabismus surgery.
Field of binocular single vision
With the field of BSV, the presence or absence of diplopia in all directions of gaze is quantified. For quantifying the field of BSV, different devices are available. In literature, the Goldmann perimeter routinely is used ( Fig. 3 ). This device does not reflect, however, a patient’s general viewing condition, because fusion is limited. Measuring the field of BSV ( Fig. 4 ) with the Harmswand or the Maddox screen is performed in more natural viewing conditions.
While measuring the field of BSV, either the patient is asked to follow a light in different directions until double vision is reported or the head is moved while the eyes fixate on a light. Although a field of BSV gives us a way of quantifying double vision, the test outcome may differ significantly from the patient’s subjective experience in normal life.
Scoring of the field of BSV can be done with help of the Sullivan core. With this score, the field of BSV is quantified from 0 (no BSV) to 100 (maximum BSV) ( Fig. 5 ). Quantifying the field of BSV is helpful for research purposes but also helps informing the patients about the progress of the disease.
