Enophthalmos is defined as the posterior displacement of the globe in an anteroposterior plane within the orbit. This is to be distinguished from hyperglobus, hypoglobus, esoglobus, and exoglobus.[1] The opposite of enophthalmos is proptosis, also termed exophthalmos, where the globe is displaced forward in an anteroposterior direction.
Clinically, the eye may appear sunken and have a deeper superior sulcus with either an upper eyelid retraction, upper eyelid ptosis, or, often, both, eyelid retraction with lagophthalmos as well as ptosis because of the three-dimensional change in the orbital tissues and the eyelid. Dryness may be the initial presenting symptom. Some patients will notice the asymmetry in their eye positions. It should be remembered that the normal position of the globe varies according to age, ethnic background, and sex. African orbits are shallower than caucasian orbits, resulting in the appearance of relatively "proud eyes".
Enophthalmos may be congenital or acquired and may be associated with systemic syndromes and local orbital disease.[2]
Etiology and Pathophysiology
Enophthalmos may be caused by one or more of the following anatomical and physiological factors:
1. Enlargement of the Orbit
Enlargement of the orbit may be because of a defect in the orbital walls or a displacement of one or more of the orbital walls. Causes include:
2. Reduction of Orbital Contents
3. Shrinkage or Contracture of Orbital Contents
Enophthalmos reported in the literature largely affects males more than females, as the most common cause is related to trauma. In a retrospective study of 629 patients with orbital fractures, the male to female ratio was 5.7:1, with a mean of 37.2 years of age.[3]
Symptoms
The underlying etiology of enophthalmos usually determines the presenting symptoms. These symptoms can include:
Clinical Examination
In unilateral cases, the asymmetry of the orbits and globes may be obvious. The deep-set eye may show the associated deep sulcus, relative ptosis, lagophthalmos, and reduced palpebral fissure. Many patients will have associated hyperglobus, hypoglobus, esoglobus, or exoglobus.[1]
The best way to visually examine for relative enophthalmos is the chin-up position, also known as the dog's view or the lover's view (attributed to the French, but this may be apocryphal).
Objective Measurement of Enophthalmos
The orbit is comprised of seven bones. The superior wall involves the lesser wing of the sphenoid and the orbital plate of the frontal bone. Both the zygomatic bone and the greater wing of the sphenoid form the lateral wall. The inferior wall is composed of three bones: the zygomatic, the maxilla, and the palatine bones. Finally, the medial wall is made of the sphenoid, the ethmoid, and the maxilla.[29] These seven bones form a protective housing for the globe which protrudes just beyond the orbital rim. Enophthalmos can be defined as a difference of 2mm or more in the anteroposterior axis between the two globes when measured from the lateral edge of the orbit to the maximum height of the corneal surface.[30] This definition assumes that one of the globes is in a normal position for the particular patient.
Clinical Measurement: Exophthalmometry
The clinical assessment of enophthalmos is measured with respect to the individual's orbital margins and is the degree of the anteroposterior position of the globe. A popular tool for clinical assessment is ex ophthalmometry. This allows the clinician to diagnose and monitor the changes in the globe position. Several different exophthalmometers are available, each with its advantages and disadvantages.
Hertel exophthalmometer: measures from the lateral orbital rim to the apex of the corneal surface. It is relatively easy to use in the clinical setting, but its use is dependent on the integrity of the lateral orbital rim, which is often lost in orbital-zygomatic fractures. It has also been found that inter-observer variation is high.[31]
Naugle exophthalmometer: is a similar, horizontally placed bar between two lateral canthi; it takes this a step further by using a 4-point fixation system, involving the superior and inferior orbital margins. Black markers along the length of the instrument aid in finding the midpoint of the pupils, thereby allowing the user to easily reposition the instrument for a serial of reproducible measurements. A study comparing Hertel and Naugle exophthalmometry found Naugle measurements to be more reliable in those who have suffered orbito-zygomatic fractures, where the lateral border of the orbit is disturbed, and the patient experience is more pleasant.[32]
A Leudde prism exophthalmometer: allows parallax error to be removed when observing both eyes to assess the degree of enophthalmos or exophthalmos. A parallax error occurs when the viewing angle changes between observers who do not view an object from an angle that is perpendicular to the object. The Leudde prism is used as a ruler and placed on the lateral orbital rim as a point of reference.
The Mourits exophthalmometer: combines the use of prisms placed along with a graduated metal frame (much like the Hertel instrument) and is thought to be a reliable tool when compared to Leudde and Hertel tools.[31]
Computed-Tomography (CT) and magnetic resonance imaging (MRI) are the two modalities most commonly used when assessing orbital diseases and trauma. CT imaging is best used when bony detail needs to be assessed. MRI is more useful for the assessment of soft tissue detail.
Computed tomography provides an excellent view of the contents of the orbit and allows for accurate measurements of the degree of enophthalmos without necessarily relying on a single reference point. The lateral orbital rim may still be used.[33] In the case of fractures, the nasal septum with the mirror image of the unaffected eye can be substituted to quantify enophthalmos or the styloid process can also act as a point of reference.[34] The change in volume of orbital contents can be accurately measured using CT and may be compared to the normal side. Axial scans are most useful in assessing the degree of enophthalmos and for serial comparisons.
Zhang et al demonstrated a statistically significant relationship using CT to measure orbital volume and the volume of herniated contents in orbital fractures to the degree of enophthalmos measured.[33] The sagittal and coronal reconstructions of the orbit can be very useful in the assessment of the orbital floor in maxillofacial trauma and essential for surgical planning.[35] CT imaging does expose the patient to radiation. Once a diagnosis is established and where specific soft tissue change does not need to be assessed (carcinoma, etc), exophthalmometry is the best tool for clinical follow-up. A systematic review of exophthalmometry by Nightengale et al. (they used the Mourtis exophthalmometer) suggested that exophthalmometry may be successfully used for long-term follow-up of patients and helps reduce repeated radiation exposure with CT scans.[36]
The treatment of enophthalmos starts with a good clinical workup of the patient, including a full medical and ocular history with the progression of symptoms (old photographs may prove useful). A full eye examination is performed with an assessment of visual fields, ocular movements, and any changes in visual acuity. In the case of trauma, this may be quite straightforward as a patient may experience proptosis, followed by increasing diplopia and enophthalmos over weeks after the initial insult.
Conservative management of traumatic injuries may be a choice in some patients who do not wish to undergo orbital surgery or in those where surgery is not indicated due to the size of the fracture (small), or the absence of significant clinical symptoms e.g. diplopia caused by post-traumatic enophthalmos.[37] An oculocardiac reflex is often an indication to operate in the acute phase. This reflex presents with persistent vomiting, bradycardia, and syncope in a pediatric population. It occurs due to trapped soft tissue (commonly the inferior rectus). It is recommended that surgery in the delayed setting occur within a 2-week window, as this is sufficient time for edema to resolve and for an accurate assessment of enophthalmos or diplopia to be made. The risk of developing the orbital compartment syndrome which is a sight-threatening complication is also reduced.[35]
Another indication is the cosmetic correction of enophthalmos, especially when it is apparent to visual assessment. The degree to which enophthalmos may be apparent varies by race, age, and underlying facial and orbital anatomy. Surgical management can be guided by CT scans using an 'enophthalmos estimate line': this virtual line is drawn between the most distal part of the fractured segment to the original position of the fracture segment.[38] This provides a prediction of enophthalmos a patient may experience over time. The surgical aim is near normal ocular motility and resolution of diplopia.[39]
Techniques include metal plates for fracture reduction or the placement of orbital floor implants to support its contents. More rarely, fat injections for globe support may be used. These techniques are also used to help those with the Silent Sinus Syndrome where endoscopic maxillary antrostomy and uncinectomy (clearing of the osteomeatal complex) are performed. This aims to increase the size of the opening to the maxillary sinus and promotes drainage of any accumulated fluids, thereby decompressing the sinus system. By establishing aeration of the sinus, the procedure may reduce enophthalmos by up to 2 mm.[40]
True enophthalmos should be distinguished from the appearance of enophthalmos where there is no true anteroposterior change in the globe positions. This is often termed pseudoenophthalmos.[28][41] The differential diagnosis includes the following:
The prognosis for patients with enophthalmos varies with etiology. The surgical treatment of the silent sinus syndrome or orbital fractures is generally performed in the younger age groups with a generally excellent outcome.[5] Following traumatic orbital repair, the cosmetic and functional outcomes are satisfactory. However, residual enophthalmos and limitation of ocular motility can remain, depending upon the extent of bony and soft tissue injury.[42][43] With orbital metastatic disease, the treatment of enophthalmos is rarely undertaken as the nature of the underlying primary tumor with the possibility of other tumors systemically will determine the prognosis. The 5-year survival rate in those who required orbital exenteration due to metastasis is 41.2% in a case series of 39 patients.[44]
Complications of surgical management of enophthalmos include:
Essential patient eduction in the presence of new enophthalmos includes advice on how vision may affect their day-to-day activities (driving, work, etc.) depending upon the effect of the enophthalmos on vision and on any double vision. In the presence of orbital fractures, the patient is advised not to blow the nose to avoid orbital emphysema.
Understanding the various causes of enophthalmos is invaluable in ensuring patients receive the correct care by the relevant specialist teams. Enophthalmos is detectable to casual examination by a physician if there is more than 2 mm of difference in the globe position. In social life, cosmetic concern usually arises only if there is a larger degree of enophthalmos. Because of the large number of underlying conditions that can cause enophthalmos, appropriate referral, examination, and assessment are vital.[45]
The care of patients with enophthalmos will require ophthalmologists (often to first clinically diagnose non-traumatic enophthalmos), oculoplastic surgeons, and maxillofacial surgeons to reconstruct orbital fractures and to improve the aesthetic and functional outcomes. Close interaction with radiologists is vital to assess the appropriate imaging and to allow for any surgical planning to be undertaken.[46] [Level 5]
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