Page 20 - Demo

Chapter 118A 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.68Vision and ocular findingsThe 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.50Visual 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.69Astigmatism 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