On the occasion of World Down Syndrome Day, celebrated every year on 21 March, let's take a look at the eye diseases that most frequently affect people with Down syndrome.
Down syndrome is defined "trisomy 21'as in most cases it is determined by a chromosomal abnormality, due to the presence of a third copy (trisomy) of chromosome 21, the smallest human chromosome.
Trisomies of any chromosome could occur in the embryo, however, the presence of another copy of a larger chromosome is more likely to result in miscarriage or death in utero. Trisomy 21 is responsible for approximately 95% of Down syndrome cases, in which case affected persons therefore have 47 chromosomes. The remaining 5% has 46 chromosomes, but the extra chromosome 21 is welded to another chromosome (translocation), which results in an abnormal, but not extra, chromosome.
The eyes of people, and particularly children, with Down syndrome require particularly careful monitoring, as this chromosomal anomaly can have important effects on eye development in general and, in particular, on the morphology of the cornea.
The diseases and functional disorders that can affect these patients include:
– Ocular motility disorders
– strabismus, an ocular disorder due to deviation of the visual axes, caused by malfunctioning of the neuromuscular mechanisms that control eye movements.
– nystagmus, visual disorder due to oscillatory, rhythmic and involuntary movements of the eyeballs.
– Cataracts
Cataracts are caused by the loss of transparency (opacification) of the crystalline lens (the natural lens of the eye) and usually occur after the age of 50, as a result of the ageing process. In Down persons, cataracts can, on the other hand, occur early or even be congenital. The particular conformation of the eye can also make surgery more complex, but it is necessary in order not to compromise the health and functionality of the retina.
- Refractive disorders
About 6 out of 10 children with Down syndrome have refractive problems such as hypermetropia, myopia, astigmatism.
Correction is preferably carried out with prescription glasses, while refractive surgery is very rarely used.
As for the corneathe greatest danger is the onset of the keratoconus, a degenerative disease, progressive in character, characterised by the thinning of the corneal tissue, which thins and everted at the apex, assuming the typical cone shape.
This risk was described in a study sponsored by Prof. Aliò, which emphasised the need for thorough and frequent corneal checks on Down syndrome patients in order to intervene with the necessary therapeutic measures as soon as possible.
It must also be considered that accurate and timely treatment of eye diseases in Down syndrome patients can have positive effects not only on the health and visual wellbeing, but also on the general condition of the patient, with an improvement in his or her autonomy and consequently also in his or her possibility of social interaction.
Source
Alio JL, Vega Estrada A, Sanz P, et al. Corneal Morphologic Characteristics in Patients With Down Syndrome. JAMA Ophthalmol. 2018 Sep 1;136(9):971-978.
Dr. Carmelo Chines
Direttore responsabile
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