Microphthalmos with cyst
Microphthalmos with cyst arises from incomplete closure of the fissure in the optic vesicle, with formation of a cyst below a microphthalmic globe. The cysts can vary greatly in size and may slowly enlarge.
Small cysts can be left and may be in communication with the vitreous cavity. Large cysts are cosmetically unacceptable, cause excessive orbital bony expansion, and generally need to be removed together with the microphthalmic globe; a ball implant can be placed at the same operation and, in all cases, a suitable fornix conformer must be placed (Chapter 9).
Excision of small or moderately sized orbital cysts may retard orbital growth and lead to problems with prosthetics fitting later in life. Ball implantation can, on occasion, be difficult due to abnormal extraocular musculature.
Congenital clefts of the skull, with herniation of intracranial contents, leads to cephalocoeles: the herniating contents can be meninges (meningocoeles), brain tissues (encephalocoeles), or both tissues (meningo-encephalocoeles). When involving the orbit, they often present in childhood as fullness above the medial canthus, this swelling increasing with straining or bending. Some patients with orbital encephalocoeles will have neurofibromatosis and the association of colobomatous optic disc with basal encephalocoele is known as "morning glory syndrome''.
Direct coronal CT scanning is best for identifying the skull base deformity that always accompanies orbital meningocoeles and encephalocoeles.
Orbital cephalocoeles are removed as part of the major reconstruction in affected children, who often have multiple cranio-facial anomalies, and defects within the sphenoid bone are hard to correct compared to those of the frontal bone.
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