Page 20 - Characterization of genetic neurodevelopmental disorders at adult age, with a focus on 22q11.2 deletion syndrome - Emma Boersma

Chapter 1
A review on hearing loss in 22q11.2DS of all ages reported hearing loss in
6-60% of individuals with 22q11.2DS.67 Conductive hearing loss was found
to be most prevalent (6-53%), especially in children, probably related to a
high prevalence of chronic otitis media and cleft palate.67 Sensorineural
hearing loss was reported in 0-19% and mixed hearing loss in 0-28% of
individuals.67 Studies that only included adults reported hearing loss in 28 -
41% of inidividuals.35, 63 Balance problems have been reported as well, mostly
(42%) related to vestibular dysfunction, but some (16%) were suggestive of
visual problems.68
Vision and ocular findings
The eye consists of several structures including the cornea, lens and
retina.50 The lens, which can accommodate, together with the cornea cause
refraction of light, focusing the light onto the retina to form an image. In
case of refractive errors (such as nearsightedness, farsightedness and
astigmatism), the light is not projected accurately on the retina which results
in blurred vision. The retina consists of several cellular layers, including
ganglion cells, that process the light and generate action potentials to
the optical nerve that are transmitted to the central nervous system for
interpretation.50
Visual acuity is the ability of the eye to distinguish two points near each
other.50 Vision can be influenced by refractive errors as described before,
but may also result from, for example, cataract (clouded lens) or glaucoma
(damaged optic nerve, may result from increased eye pressure). In addition,
amblyopia (lazy eye) or strabismus (crossed eye) may cause poor vision.
Most of these ocular problems can be treated, but need intervention as
early as possible. In a study of more than 500 adults with an intellectual
disability in the Netherlands, it was found that visual acuity was related
to the severity of the intellectual disability, but refractive errors were not.69
Astigmatism was the most common refractive error in adults with an
intellectual disability, followed by hyperopia (farsightedness) and myopia
(nearsightedness),69 similar to what has been reported for adults in the
general population.70
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