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Inherited degenerative disease of the retina
characterized by severely decreased vision manifesting at birth or shortly
thereafter. Other ocular anomalies may include sensory (wandering)
nystagmus, amaurotic pupils, deep-set eyes, and photophobia. Central nervous
system anomalies have been described in some patients. Do not confuse with
Leber hereditary optic neuropathy (see Leber Hereditary Optic Neuropathy).
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First described by the German ophthalmologist Theodor von
Leber in 1869.
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Approximately 3:100,000 neonates
are born with this autosomal recessive transmitted disorder. Nine genetic
loci for LCA have been discovered, of which six genes have identified. LCA
is now no longer considered one disorder but rather multiple disorders,
which can be classified into three different categories: (1) aplasia,
resulting in abnormal embryologic formation of photoreceptors; (2) early
degeneration of photoreceptors with progressive cell death; and (3)
dysfunction of the photoreceptors with normal retinal anatomy.
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Vision is already significantly reduced at birth
or shortly thereafter. Sensory (wandering) nystagmus and lack of visual
responsiveness alert the parents, usually within the first months of life.
Initial examination may reveal a normal retina and a fundus appearance that
either is essentially normal or reveals a progressive pigmentary
retinopathy. The pupils are amaurotic and the eyes deep sunken. However, the
final diagnosis is made by electroretinography, which shows only small (at
high intensities) or no photopic responses. Both cone and rod responses are
affected. Patients are described as frequently poking and rubbing their eyes
(the so-called “Oculodigital Reflex” of Leber and Franceschetti), which is not
specific to LCA because it is observed in other forms of amaurosis (Leber
was the first to describe this phenomenon). Other associated ocular features
may include ptosis, strabismus, keratoconus/keratoglobus, cataracts,
microphthalmos, macular coloboma, pigmentary retinopathy and maculopathy,
optic disc edema, retinal vascular changes, and high-grade hyperopia or
myopia (less common). By early adolescence, the retina of LCA patients may
undergo significant changes. Retinal blood vessels often become narrow and
constricted, and pigmentary changes similar to those found in retinitis
pigmentosa may affect the retinal pigment epithelium. Despite these changes,
vision does not usually deteriorate further. Visual acuity in LCA patients
is most often limited to the level of finger counting or detection of bright
light. Some patients are extremely photophobic. At this time, no treatment
is available; however, current research is focusing on gene therapy. On rare
occasion, LCA is associated with central nervous system symptoms such as
delayed psychomotor development and seizures.
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In patients with isolated LCA (i.e., not
associated with a syndrome or central nervous system findings), no specific
anesthetic concerns should arise from this disorder. In the presence of
seizures, keep in mind that antiseizure medications can alter the metabolism
and elimination of anesthetic drugs. Cooperation of mentally delayed
patients may be limited. Sedative and/or hypnotic premedication and the
presence of the primary caregiver may be helpful during induction of
anesthesia. Dealing with a blind patient who cannot see what is happening
requires more explicit explanations in ...