Ординатура / Офтальмология / Английские материалы / Handbook of Pediatric Eye and Systemic Disease_Wright, Spiegel, Thompson_2006

Interpupillary distance is an important observation in this group of patients. Most published values represent the interpupillary distance obtained while the patient is fixating on a distant target, which may be difficult to accomplish in a child. If the measurement can be made only at the near position, this fact should be recorded, and the distance measurement can be estimated by adding approximately 3 mm. If an ocular deviation is present, the left eye is covered so that the right eye fixes and the distance from the midpupil of the right eye to the midpoint over the nasal bridge is recorded. The right eye is then covered, and a similar measurement is made on the left side. The addition of the two values represents the interpupillary distance (usually for near). A more accurate and reproducible method of measuring orbital separation is the radiologic measurement of the bony intraorbital distance. It is appropriate to calculate separately the anatomic distance for each half of the face, not only for interpupillary values but also for intercanthal values, as asymmetry is present in many craniofacial syndrome entities. The difference between the values obtained for each half of the face is an indication of the degree of asymmetry in the orbital region.

To obtain more accurate values for the degree of orbital separation, Pryor190 proposed the use of canthal measurement, believing that the sum of the inner and outer canthal distances divided by two is an accurate estimate of the interpupillary measurement. This may not be true if there are anomalies of the soft tissue structures, such as in individuals with primary telecanthus, which is discussed later in the section on hypertelorism.

PROTOTYPES OF CRANIOFACIAL SYNDROMES

It is beyond the scope of this chapter to list all the craniofacial syndromes and their ocular findings. Detailed information on rare syndromes must be obtained from standard texts of syndromes, from computerized databases, or from the specific literature. Many ocular findings are not syndrome specific but are the result of a particular anatomic derangement that may occur in multiple syndromes. The syndromes described here were selected for further description either because they were char-

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FIGURE 4-2. Facial measurements at different ages: A, outer canthal distance; B, inner canthal distance; C, interpupillary distance. (From Feingold M, Bossert WH. Birth Defects 1974;10:13, with permission.)

acteristic of a common group of craniofacial syndromes or because they had unusual or severe ocular malformations.

CRANIOSYNOSTOSIS

Cohen,38–40 in his comprehensive book on craniosynostosis, described the historical interest and intrigue shown for patients with craniosynostosis, who are characterized by an unusualshaped skull because of cranial and suture abnormalities. Descriptions appeared in mythical writings, religious treatises, and the literature of a broad scope of medical disciplines.

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FIGURE 4-2. (continued).

Virchow243 advanced the principle that closure of one or more cranial sutures resulted in compensatory growth in the other areas of the skull. An illustration of different ways in which compensatory growth could be manifested is shown in

FIGURE 4-3. Effect of premature closure of various sutures on cranial morphology. Note that growth is inhibited perpendicularly to synostotic suture and expansion of skull occurs in area of open suture. Brachycephaly results from premature closure of the coronal suture, causing a short but laterally expanded head. Plagiocephaly (lower) results from asymmetrical closure of one coronal suture, causing anterior posterior elongation of the anterior aspect of the skull. A long narrow skull results from premature closure of the sagittal, causing anterior posterior elongation of the skull.

Figure 4-3. This boat-shaped head deformity is caused by fusion of the sagittal suture, which causes a decrease in the lateral growth and an increased anteroposterior growth, resulting in a skull shape that resembles the keel of a boat. Another cranial synostosis, oxycephaly (tower head deformity), results from early fusion of the coronal sutures plus part of the sagittal suture

producing increased vertical diversion to the skull. The overall incidence for all forms of craniosynostosis is 1 in 2,000 to 1 in 2,500 live births.130,131 Sagittal synostosis is the most common, with an incidence of 1 in 5,250.131 Coronal synostosis is the second most common form, with an overall incidence of 1 in 16,000 in males and 1 in 8,000 in females.130,131

In many craniosynostosis syndromes, the particular suture showing premature closure is not necessarily characteristic of that syndrome, and patients with the same syndrome may manifest different combinations of suture closure. However, in some cases there does seem to be a characteristic cranial shape and facial appearance. Facial sutures are also involved, resulting in the midface hypoplasia and orbital dystopia. The ophthalmologist is more frequently consulted in cases of patients with monogenic syndromes, such as Crouzon and Apert syndromes, but the principles outlined and the types of problems and malformations may be applied to other causes of craniosynostosis. Craniosynostosis, whether isolated or part of a syndrome, is a major concern because of the potentially serious secondary, and in some cases primary, disturbances to ocular structures. The diagnosis of craniosynostosis and determination of the suture(s) involved are usually initiated by clinical findings, which include assessment of craniofacial shape, movement or lack of movement of the calvarial bones during infancy, and the presence or absence of sutural ridging, and can be confirmed by an X-ray of the skull or head CT examination.89 In some instances, particularly with sagittal or coronal involvement, plain X-rays may suffice. If radiographic interpretation is equivocal, CT imaging is mandatory.

OCULAR FINDINGS

The ocular findings associated with craniosynostosis are potentially a serious threat to vision. Fortunately, the most serious ocular complications are often preventable if recognized early and treated promptly.64 Other findings, such as strabismus and rarer anomalies, can be treated with appropriate surgery or other therapeutic modalities in a prioritized manner determined by the ophthalmologist and the craniofacial team.

Routine ocular examination, with special attention to positional relationships of the ocular adnexa, reveals most abnormalities. In addition to the standard history, more detailed questions about symptoms that suggest corneal exposure or

changes in vision should be included. Because incomitant motility problems are common, a detailed evaluation of limitation of movement in all fields of gaze is indicated. Intraocular pressure, visual fields, and corneal sensitivity should be determined, and exophthalmometry should be performed when appropriate and possible. Special precaution should be exercised if a sedated examination is planned because of the frequent associated respiratory problems. Special imaging procedures, such as MRI and CT, are often routinely done in these patients. Small cuts (1.5– 3 mm) through the orbit should be taken to provide more detailed information on the position and size of the ocular muscles. This information will be particularly useful if strabismus surgery is contemplated.

Visual loss is the most serious ophthalmologic complication seen in patients with craniosynostosis. It may be present at birth and can progress; it may also be a complication of reconstructive surgery. Therefore, many patients require ophthalmologic surveillance from infancy through adulthood or until their condition is stable. Visual loss may result from acquired ocular pathology, such as papilledema, optic atrophy, corneal exposure, or amblyopia secondary to strabismus or anisometropia. Several low-frequency ocular malformations may cause poor visual acuity and are generally noted during infancy in the course of a standard examination.

Optic nerve findings may reflect elevated intracranial pressure or possibly be secondary to local anatomic changes in the optic canal. Because the presence of craniosynostosis is currently recognized earlier than in years past, there seems to be a decreased incidence of papilledema and optic atrophy; however, these findings are still possible, and any routine ophthalmologic evaluation must include the status of the optic nerve.124,125 Ophthalmologic evidence of increased intracranial pressure frequently necessitates earlier neurosurgical intervention. Some authors have recommended the use of visual evoked potential (VEP) and fluorescein angiography in some cases to aid in evaluation of optic nerve status.91

Increased tortuosity and a blurred optic disc border suggest the presence of increased intracranial pressure but also can exist without evidence of abnormal intracranial pressure. The causes of the pseudopapilledema and vessel changes are not always clear. Optic atrophy may also be noted without documented papilledema, thus raising the question whether some cases are caused by local compression of the optic nerve.

Proptosis (sometimes called exorbitism) seen in many craniosynostosis syndromes is caused by the shallow orbits and midface hyperplasia. This finding is quantitatively different from exophthalmos secondary to tumors and pseudotumors in patients with normal orbits and may show a different rate of progression. However, the ophthalmic symptoms and problems are similar. The degree of proptosis may vary greatly in patients with the same syndrome, ranging from minimal changes to severe corneal exposure mandating surgical intervention to prevent cornea ulceration and blindness. Figures 4-4 and 4-5 show the variations present in two patients with Crouzon syndrome. The patient shown in Figure 4-4 required immediate intervention and ultimately had fairly good visual function without long-term effects of the severe proptosis noted in infancy. The patient shown in Figure 4-5 had no corneal complications and required no special therapy for the proptosis.

Occasionally, during the examination of patients with marked exorbitism, slight retraction of the lid may cause luxation of the globe. Luxation may occur spontaneously or with manipulation of the lids. This dramatic finding may be frightening to the examining ophthalmologist, especially if it occurs when the exophthalmos is measured with an instrument placed on the lateral orbit. Fortunately, the patients or their families usually know how to gently push the eye back by pulling the lid over it. If luxation is not reduced promptly, secondary conjunctival edema may ensue, making it more difficult to reduce the luxated globe. If the globe remains unprotected, severe corneal exposure will follow, necessitating aggressive therapeutic intervention to prevent serious complications.

Severe proptosis from the reduced orbital volume may necessitate a different surgical treatment different from other causes of proptosis. If conservative management is insufficient to prevent corneal damage, a tarsorrhaphy (usually lateral) may be indicated as a temporary or permanent measure, depending on the long-term management plan for the facial deformity in the patient. Eyelid surgery should be deferred if extensive reconstructive surgery is anticipated in the near future, unless the corneal integrity is severely threatened. Tarsorrhaphy may protect the cornea and diminish the proptotic appearance by narrowing the abnormally wide palpebral fissure, but the improvement may be short lived and recurrence may result from constant mechanical force on the sutured lids. The definitive

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FIGURE 4-4A–C. Crouzon syndrome. (A) Frontal view before and after cranial reconstructive surgery. Note marked exorbitism (proptosis) with severe corneal exposure. (B) Side view. Severe midface hypoplasia and increased vertical dimensions to skull are present preoperatively, with improvement postoperatively. (C) At age 5 years, the patient had no signs of serious corneal exposure, but large exotropia exists that will require future ocular muscle surgery.

FIGURE 4-5. Crouzon syndrome: patient has less severe involvement and has never had evidence of corneal exposure.

solution is reconstructive surgery that creates a larger orbit. Standard decompression techniques that are useful for tumors or hyperthyroidism are not suitable.

Other causes of visual impairment include unusual refractive error and amblyopia due to anisometropia or strabismus. The treatment of refractive error and amblyopia is standard but may be hindered by difficulty in fitting glasses that are comfortable for patients with nose, eye, ear, and orbital malformations.

In the early literature, authors attributed all cases of strabismus to poor visual acuity, but this was proved to be incor-

rect. Although decreased visual acuity may be an important factor in some patients, strabismus is often the result of related anatomic and mechanical factors. The ocular deviation in the primary position is most frequently exotropia (Fig. 4-4) but also can be esotropia or straight eyes. A more consistent finding is the presence of an exotropia in the upgaze position with straight eyes or esotropia in downgaze, producing the V configuration.126,158,160 Many patients also have associated overaction of the inferior oblique muscles. A subgroup of patients shows limitations in various fields of gaze. Although some of these findings may be attributed to mechanical effects of abnormally shaped and positioned orbits, there is good evidence that a number of patients have an abnormal insertion, structure, or orientation of the extraocular muscles.52,59,146,252 It is unclear whether this represents a pleiotropic effect of the gene or secondary changes in the position of the muscles of the globe caused by local mechanical factors that occur during embryogenesis.

Most information about strabismus relates to patients with Crouzon and Apert syndromes, and there is some disagreement as to the ideal timing of surgical intervention for strabismus. Some physicians recommend early surgery, but many prefer to defer surgery until after the facial reconstructive surgery.27,160 Reconstructive surgery of the midface in craniosynostosis may not affect the degree or pattern of ocular motility, but in some cases a substantial effect does occur (in contrast to patients with hypertelorism and median facial cleft in whom reconstructive surgery has been observed to significantly affect the ocular motility).31 Attainable goals of therapy in most patients are good vision in both eyes and a cosmetically acceptable position of the eyes in the primary position of gaze. Because of the potential anatomic abnormalities of ocular muscle and the orbits, it is often impossible to align the eyes in all fields of gaze, and so the surgery is more directed to a straight primary

position.27,147,160

Intrinsic ocular pathology is less frequent than secondary pathology, but it may include a few rare anomalies, such as iris colobomas, cataract, vitreous opacity, and medullated nerve fibers, along with the ocular muscle abnormalities. Keratoconus has occasionally been observed, as have changes in iris illumination and fundus pigmentary changes.21,145 There is frequently a disturbance in the lacrimal outflow system with recurrent dacryocystitis.