Down’s syndrome is a trisomy caused by an extra copy of chromosome 211. The extrachromosomal material is transmitted either by non-disjunction, unbalanced translocation, or mosaicism.
It is the most common chromosomal anomaly seen in live births2. As an ophthalmologist, it is important to screen for ocular abnormalities since the incidence of ophthalmic disorders is between 46-100%3. One study found 97 % of children with Down’s syndrome with at least one ocular abnormality4. This proves the necessity to carefully screen these children for any disorders and their prompt treatment. It is recommended that all children diagnosed with Down’s syndrome must undergo evaluation by a Pediatric ophthalmologist before the age of 6 months and then annually thereafter if no abnormalities are found at the first visit5
Although there are many ophthalmological anomalies seen in Down’s syndrome, we will be discussing only the ten most clinically significant ones below.
1. Refractive Error and Visual acuity:
The most common refractive error found in patients with Down’s syndrome is hypermetropia, followed by myopia and astigmatism5. Hypermetropia is seen in 55-80%, myopia in around 18-59% of patients5. Astigmatism has been noted to be present in around 20-30%5. It is interesting to note that refractive errors may not always be present at infancy but may develop later on in life6. The reason for a greater prevalence of hypermetropia is supposedly failure of emmetropization, which generally occurs with growing age in normal children6,7. Various theories have been proposed for this such as poor accommodation which is typically seen in patients with Down’s syndrome. Other theories for poorer development of visual acuity that have been proposed are structurally different visual cortex of patients with Down’s syndrome8.
The most common type of strabismus is Esotropia as reported by most studies in literature9,10. The prevalence of exotropia is far less common, being only 8-20%9-10. Vertical deviations, though seen are uncommon10. Studies have shown no association between the presence of hypermetropia and the occurrence of strabismus in patients with Down’s syndrome9.
Nystagmus is usually congenital. It is seen in approximately 5-30 % of all patients with Down’s syndrome11. The nature of this nystagmus is either horizontal jerky or pendular12. Nystagmus is often associated with refractive errors10-12. This is one of the reasons why the threshold for prescribing glasses in children with Down’s syndrome is much lower than for regular cases.
4. Nasolacrimal outflow obstruction :
It is extremely essential to look for nasolacrimal duct obstruction in a child with Down’s syndrome since the incidence of nasolacrimal outflow obstruction is as much as 17-36%13. The various nasolacrimal anomalies seen are punctal agenesis, canalicular atresia and stenosis, and anteriorly placed turbinates, dacrocutaneous fistula. It is considered more challenging to treat the nasolacrimal outflow obstruction in Down’s syndrome than in the general population primarily because it is a consequence of complex developmental anomalies rather than just failure of the opening of the Hasner’s valve13.
As compared to the normal population, syringing and probing may not suffice and may call for aggressive procedures such as stent placements and balloon dacryoplasties as the primary procedure of choice14.
5. Squamous blepharitis:
A very severe form of squamous blepharitis is seen in patients with Down’s syndrome. A deficient immune response has been held responsible by some as reason for causing severe blepharitis whereas some attribute it to abnormal skin structure in patients with Down’s syndrome15. It requires aggressive treatment as it can lead to refractive errors and keratoconus16.
Keratoconus is most commonly seen around the onset of puberty in patients with Down’s syndrome. Contributing factors include steeper posterior corneal curvature at birth, higher-order aberrations, and eye rubbing consequential to squamous blepharitis17,18. A genetic theory pointed out by Wang et al states that the corneal collagen fibres are affected in Down's syndrome due to the variations seen in Chromosome 21 and this, in turn, makes the cornea unstable19.
7. Lenticular opacities:
Congenital or early neonatal cataracts are found to be around 8% in incidence, which also includes visually insignificant opacities20. The incidence of visually significant opacities was found to be only 1% in the neonatal age group by Haargaard B et al21. Since this rate is still higher than what is seen in the normal populations, it is imperative to screen for early cataracts in these cases22. A visually significant cataract is more commonly seen in the adolescent and presenile age groups.
The common morphologies of cataracts seen are cerulean, nuclear, zonular and cortical amongst others21. IOL implantation is preferable in these cases as it is difficult to manage the patient post-operatively with a contact lens22.
It must be ensured that a multidisciplinary approach is chosen before planning for cataract surgery if need arises. It is important to involve the anesthetist, cardiologist for an uneventful surgery and recovery.
8. Retinal anomalies:
Scott et al23 found the central macular thickness in Down’s syndrome to be higher than the normal population, suggesting abnormal macular development. However, they did not find any correlation between the thickness of macula and vision in these patients. Studies have also shown the persistence of inner retinal layers at fovea in patients of Down’s syndrome24. All these studies suggest that the retina is structurally abnormal in Down’s syndrome, although more detailed studies are needed for the same.
9. Optic nerve head abnormalities:
The optic nerve head tends to be smaller in patients with Down’s syndrome although the size does not correlate with vision25. It has been found however that smaller disc size makes them susceptible to optic nerve drusen formation26. It has also been noted that the neurosensory abnormalities often seen on VEP in these patients probably do not occur at the level of the ONH but are due to an abnormality in the visual pathway25. Many other insignificant anomalies are seen such as an increased number of vessels crossing the disc, but this is not clinically insignificant.
Accommodation deficits in children with Down’s syndrome are not associated with poor visual acuity27. Hence, it is extremely essential to incorporate dynamic retinoscopy in the examination of children with Down’s syndrome. If accommodation is found defective, prompt treatment with bifocals is a must28.
In conclusion, Down’s syndrome presents with many ophthalmological abnormalities in addition to systemic anomalies, which require early detection and treatment by a Pediatric ophthalmologist. This is essential to achieve better outcomes visually and also promote the overall psychological well-being of a child with Down’s syndrome.
- Jacobs PA, Baikie AG, Court-Brown WM, Strong JA. The somatic chromosomes in mongolism. Lancet 1959;1:710-3.
- Jones KL. Smith's recognizable patterns of human malformation, 4th ed. Philadelphia: WB Saunders, 1988:10-2.
- Creavin AL, Brown RD. Ophthalmic abnormalities in children with Down syndrome. J Pediatr Ophthalmol Strabismus. 2009;46:76–82.
- Akinci A, Oner O, Bozkurt OH, Guven A, Deqerliyurt A, Munir K. Refractive errors and strabismus in children with Down syndrome: a controlled study. J Pediatr Ophthalmol Strabismus. 2009;45:83–6.
- Roizen NJ, Mets MB, Blondis TA. Ophthalmic disorders in children with Down syndrome. Dev Med Child Neurol. 1994; 36:594–600
- Cregg M, Woodhouse JM, Stewart RE, et al. Development of refractive error and strabismus in children with Down syndrome. Invest Ophthalmol Vis Sci. 2003; 44:1023–1030
- Wesson MD, Maino DM. Oculovisual findings in children with Down’s syndrome, cerebral palsy, and mental retardation without specific etiology. In: Maino DM, ed. Diagnosis and management of special populations. St Louis: Mosby, 1995:17–54
- Imai M,Watanabe H, YasuiK,KimuraY, Shitara Y, Tsuchida S, et al. Functional connectivity of the cortex of term and preterm infants and infants with Down’s syndrome. Neuroimage. 2014;85:272–8
- Ljubic A, Traikovski V, Stankovic B. Strabismus, refractive errors and nystagmus in children and young adults with Down syndrome. Ophthalmic Genet. 2011;32:204–11
- Hiles DA, Hoyme SH, Mc Farlan F. Down’s syndrome and strabismus. Am Orthopt J 1974;24:63–68
- Wagner RS, Caputo AR, Reynolds RD. Nystagmus in Down’s syndrome. Ophthalmology 1990;97:1439–1444
- Shapiro MB, France TD. The ocular features of Down syndrome. Am J Ophthalmol 1985;99:659-63
- Lueder GT. Treatment of nasolacrimal duct obstruction in children with trisomy 21. J AAPOS 2000;4:230 –2
- Coats DK, McCreery KM, Plager DA, Bohra L, Kim DS, Paysse EA. Nasolacrimal outflow drainage anomalies in Down’s syndrome. Ophthalmology. 2003;110(7):1437-1441
- Catalano RA. Down syndrome. Surv Ophthalmol 1990;34:385-98.
- Millis EA. Ocular findings in children. In: Lane D, Stratford B, editors. Current approaches to Down's syndrome. London: Holt, Rinehart and Winston, 1985:103-18
- Alio JL, Vega-Estrada A, Sanz P, Osman AA, Kamal AM, Mamoon A, et al. Corneal morphologic characteristics in patients with Down syndrome. JAMA Ophthalmol. 2018;136(9):971–8.
- Yeniad B, Alparslan N, Akarcay K. Eye rubbing as an apparent cause of recurrent keratoconus. Cornea. 2009;28(4):477-479
- Wang Y, Rabinowitz YS, Rotter JI, Yang H. Genetic epidemiological study of keratoconus: evidence for major gene determination. Am J Med Genet. 2000;93(5):403-409.
- Sorsby A. Modern ophthalmology—topical aspects, Vol 1. 4th ed. London: Butterworths, 1964:632.
- Haargaard B, Fledelius HC. Down’s syndrome and early cataract. Br J Ophthalmol 2006;90:1024–7.
- Gardiner C, Lanigan B, O’Keefe M. Postcataract surgery outcome in a series of infants and children with Down syndrome. Br J Ophthalmol 2008;92:1112‑1116
- O’Brien, S., Wang, J., Smith, H. A., Donaldson, D. L., Haider, K. M., Roberts, G. J., et al. (2015). Macular structural characteristics in children with Down syndrome. Graefes Arch. Clin. Exp. Ophthalmol. 253, 2317–2323
- S. Mangalesh, A. Vinekar, C. Jayadev et al., “Spectral domain optical coherence tomography in detecting sub-clinical retinal findings in asian Indian children with down syndrome,” Current Eye Research, vol. 44, no. 8, pp. 901–907, 2019
- Postolache L. Abnormalities of the optic nerve in down syndrome and associations with visual acuity. Front Neurol 2019; 10:633
- MullieMA, SandersMD. Scleral canal size and optic nerve head drusen. Am J Ophthalmol. (1985) 99:356–9
- Satgunam P, Datta S, Sumalini R. Near vision in individuals with Down syndrome: a vision screening study. Eye (Lond). 2019: 33:1254–1260
- Nandakumar K, Leat SJ. Bifocals in children with Down syndrome (BiDS) - visual acuity, accommodation and early literacy skills. Acta Ophthalmol. 2010;88:e196–e204