GENERAL FIBROSIS SYNDROME
This syndrome is characterized by replacement of normal muscle tissue by fibrous tissue in varying degrees. The various clinical presentations depend on the number of muscles affected, the degree of fibrosis, and whether the involvement is unilateral or bilateral. Although the condition has been known since the 19th century, it was Brown who coined the term "general fibrosis syndrome" in 1950, after evaluation and treatment of three sporadic cases. The condition is congenital, with males and females equally affected. Several large pedigrees have indicated autosomal dominant inheritance, although Waardenburg suggested that the autosomal recessive mode occurs, but less commonly.
Clinical Manifestations Laughlin characterized the syndrome as encompassing the following: (1)fibrosis of the extraocular muscles; (2) fibrosis of Tenon's capsule; (3) adhesions between muscles, Tenon's capsule, and globe; (4) inelasticity and fragility of the conjunctiva; (5) absence of elevation or depression of the eyes; (6) little or no horizontal movement; (7) eyes fixed 20 to 30 degrees below the horizontal; (8) blepharoptosis; (9) chin elevation; and (10) the condition being present at birth.
Letson added the following findings: (1) the disease is often
autosomal dominant, but may be sporadic; (2) there is often associated
exotropia or esotropia; (3) amblyopia is common, which may be
partly due to the difficulty of wearing an optical correction
when there are associated significant refractive errors.
Congenital fibrosis of the inferior rectus is probably a variant of the general fibrosis syndrome. The inferior rectus alone or together with a levator may be involved, with little or no involvement of the other extraocular muscles. The condition may be unilateral or bilateral and is commonly asymmetric. Because patients cannot typically elevate their eyes even to the midline, they adapt a compensating chin-up position to maintain binocular vision. Patients with isolated inferior rectus involvement may the same as those patients who present with a double elevator palsy and a restricted inferior rectus on forced duction testing.
Another variant of the general fibrosis syndrome is strabismus fixus, in which the eyes are in a markedly fixed position of esotropia or exotropia. The eyes are so firmly fixed that they cannot be actively or passively moved in a horizontal direction, although vertical movement is usually possible.
Another possible variation of the general fibrosis syndrome is the vertical retraction syndrome, well described in two siblings by Khododoust and von Noorden. In this condition, horizontal movements are normal, but elevation and depression are reduced, while the eye is abducted. In addition to the vertical limitation in two siblings, there was a retraction of each eye during attempted depression, with the eye in the abducted position. One patient exhibited pronounced exotropia in upgaze; the other had exotropia in downgaze.
Pathogenesis Many researchers have attempted to explain the general fibrosis syndrome on the basis of a nuclear, supranuclear, or myogenic defect. However, the histologic findings have often been interpreted on the basis of striated skeletal muscle tissue in normal and diseased conditions. Findings ordinarily classified as degenerative in skeletal muscle can be normal in extrinsic ocular muscle. Also, any theory of secondary degeneration does not explain why the muscles may have an anomalous insertion.
Treatment The
goal of surgical management in the general fibrosis syndrome is
to center the eyes and improve the compensatory head posture.
In patients with significant hypotropia, maximal recession or
disinsertion of the inferior rectus muscles is indicated. However,
elevation of the hypotropic eye accentuates the ptosis. Bilateral
frontalis suspension is required soon after the strabismus surgery.
Because these patients often do not have a Bell phenomenon, corneal
drying may occur after ptosis surgery. Therefore, the lid should
be elevated only to the upper pupillary border.