OCULAR DISORDERS IN INDIVIDUALS WITH DOWN SYNDROME

Abstract

Down syndrome (DS) is the most common chromosomal anomaly. Numerous ophthalmic features have been reported including abnormalities of the anterior, medial and posterior ocular segment, as well as refractive errors, strabismus, amblyopia and nystagmus. The aim of our study was to investigate the ocular disorders amaug Macedonian and Croatian population with DS, to compare results between two ethnic groups as well to compare the results with the published data.
The aims of our research were: to estimate the prevalence of ocular disorders of anterior, medial and posterior segment amaug Macedonian and Croatian population with DS and to compare the results with the published studies, to estimate the prevalence of strabismus among Macedonian and Croatian population with  DS.   Other   aims   were  to  compare  the results with the published studies as well to estimate the prevalence of refractive errors amongst Macedonian and Croatian population with DS and to compare the results with the published studies. Finally, aim of our study was also to establish the guidelines for ocular and refractive screening amaug children and young adults with DS in Macedonia and Croatia.
Population-based, cross-sectional, epidemiological data collection was conducted involving Down syndrome patients seen in private polyclinic in Macedonia and Croatia.
A total of 108 children and young adults with DS from Macedonia and 64 children and young adults with DS from Croatia were enrolled in this study, as a control group. The diagnosis of DS was made either based on clinical characteristics or by cytogenetic analysis. Protocols for general health, birth dates, ocular examination as well ocular motility and refractive state, were prepared.
The ocular examination included: visual acuity assessment, slit-lamp bio-microscopy, ocular motility, cycloplegic refraction and ophthalmoscopy.
The mean value of maternal age within the Macedonian population with DS was 28.4 years and within the Croatian population with DS, 30.2 years. The prevalence of upward palpebral slanting in examined group was 58.3%, and in control group 65.6%. The Epicanthus was present in 20.4% from the examinees within the Macedonian population, and 31.2% within the Croatian population. The prevalence of iris stromal hyopoplasia in examined group was 36.1% versus 18.8% in the Croatian population.
The Brushfield spots were present in 23.1% from the examinees amongst the Macedonian population and in 28.1% within the Croatian population.
The prevalence of strabismus in Macedonian population was 33.3% versus 20.3% in Croatian, the presence of nystagmus was12% amongst the Macedonian, versus the 6.3% within the Croatian population. The amblyopia was represented by 82.7% among the Macedonian, versus the 68.9% among the Croatian population.
The high prevalence of refractive errors showed 92 % of the Macedonian population and 87.3% of the Croatian population with DS. The prevalence of astigmatism in the Macedonian population was 46.6% versus 27% in the Croatian population.
The reminder of conclusions is as following:
1.The most common ocular feature within the Macedonian and Croatian population with DS were refractive errors and upward palpebral slanting.
2.The prevalence of strabismus amongst Macedonian and Croatian population with DS was similar to the wider range of prevalence values within the published data. The prevalence of strabismus among DS population is higher, compared to general population.
3.The overall  prevalence of refractive errors in DS population is much higher than general population, which was also proved by our research.
4.The most common refractive error among Macedonian and Croatian population with DS was hypermetropia, which results were represented in the published data initially analyzed.
5.Iris stromal hypoplasia was more often feature in our groups, compared with Brushfiield spots.
6.Oblique astigmatismus was the most common type of astigmatism in our groups. This is of special interest, considering the age structure of our groups.
Although the presence of strabismus in Down syndrome may be predictive of a significant error, a refractive error is not necessarily indicative of a strabismus.
Oblique astigmatism may be caused by the upward slanting of the palpebral fissure, first described in the original publication specific for the Down syndrome by Down Not, but as a general hypothesis, the pressure from eyelids has been pointed out as a major etiological factor of corneal astigmatism.
Further studies should find connection between high incidence of oblique astigmatism in children and adolescents with DS and the quantity of upward slanting.
Because of the high frequency of ocular pathology, all individuals with DS should be enrolled in continuous visual screening program from birth. The screening guidelines should be as follow: first examination at one month of age, than at one year of age, at 2-3 years of age, at 5-6 years of age (school start) an thereafter every five years.