Vision impairments in young adults with Down syndrome

People with Down syndrome have more visual problems than general population. They experience a premature aging, and it would be expected they will also have an acceleration in worsening visual function. A prospective observational study which includes visual acuity, refractive error, accommodation, binocular and colour vision was performed to young adults with (n=69) and without (n=65) Down syndrome and to a senior group (n=55) without Down syndrome. Results showed significant differences in visual acuity between groups (p<0.001) and it can be improved with a new prescription in 40% of the participants with Down syndrome. Regarding to accommodative state, no significant differences were found between groups of young people. Concerning binocular vision, 64.7% of strabismus was observed in the group with Down syndrome (p<0.001). Visual abnormalities are significant in young adults with Down syndrome and are different from those of older people without Down syndrome, some of which can be improved by providing the optimal prescription as well as regular eye examinations.

Keywords:

Subject: Public Health and Healthcare - Public Health and Health Services

1. Introduction

Down syndrome (DS) is one of the most regular genetic disorders and the most common genetic cause of intellectual disability overall. The estimated incidence of Down syndrome is between 1 in 1000 and 1.4 in 1000 live births in European countries and the United States, respectively [1]. The number of people with DS living in Spain is around 35 000 [2].

DS varies in severity among individuals and it commonly has other medical conditions associated in cardiac, metabolic, gastrointestinal and respiratory systems [3,4]. Life expectancy has dramatically increased in people with DS due to the medical advances in diagnosis and treatment of the pathologies they present. Currently, in developed countries, people with DS can live for more than 70 years [3,5,6,7]. Preventive health care is not as frequent as it should be in adolescents and young adults with DS [8]. There is a widespread interest in providing them with the necessary training to enable them to work and be as independent as possible. The more autonomy they have, the better their integration will be.

Nowadays, people with DS have a very active life so visual demands are greater than they were some years ago. Signs such as redness or watering eyes, squinting, tilting head extremely, placing head too close to the desk while working at near distance and poor attention at near tasks can be directly observable by relatives, heads and teachers. However, there are some symptoms such as blurry, double vision, headaches that people with DS frequently are not able to report because of their communication problems [9,10,11]. All these conditions are known to be related to visual impairments.

Most of the literature reveal more prevalence in visual and ocular anomalies such as refractive errors, binocular disorders, nystagmus and lack of accommodation in children with DS [12,13,14,15,16,17,18,19,20] but there is less information about young adults and seniors [20,21,22,23,24].There are recommendations for the timing of basic medical referrals in new-born babies with DS and these include vision. The first check-up would take place just after birth, and then in the first year every 6 months, to rule out congenital cataracts, glaucoma, nystagmus and retinal pathologies. Later in childhood visual examinations should be at least once per year or every two years [18]. In childhood more frequent ocular anomalies detected are strabismus and refractive errors, that is why is so important to treat them as soon as possible. For adults the recommendation for visual examinations is every five years [25].

People with DS and other conditions with neurological disorders experience more difficulties to receive health care than the general population [26,27] and it includes vision care. Sometimes communication problems and mental capabilities make difficult to apply the same methods used to evaluate vision, as it is performed in general population. So, that is why eye experts must know how to adapt procedures to get reliable responses to obtain a diagnosis and provide an appropriate treatment [9,11].

Eye problems change with age – cataracts, presbyopia – which is why regular eye checkups are so important. It has been reported that adults and seniors with DS wear the same glasses that were prescribed when they were children or the glasses they use are not well adjusted. This fact would explain the lack of compliance in their use [28,29,30]. Therefore, a prospective study of the ocular manifestations in a group of young adults with DS was undertaken and compared to visual impairments in young adults without DS and to seniors without DS.

2. Materials and Methods

A sample of 69 young adults with DS (Group 1) were recruited from Aprocor Foundation. The aim of this Foundation is to improving the quality of life of people with intellectual disabilities and their families while promoting a model of an inclusive society. The possibility to participate in this research was offered to the head of Aprocor Foundation and the families which agreed and complied with the inclusion criteria were accepted in the study. People belonging to Aprocor perform different tasks such as painting, handicrafts, packaging, gardening, working with computers or in a laundry. All the activities are adapted to their capabilities. The typical controls were formed by students from the Optic and Optometry Faculty of the Complutense University in Madrid and were subdivided into two subgroups. Group 2 were 65 young adults (undergraduate students) without DS and Group 3 were 55 seniors without DS too (students enrolled in a special programme for seniors). Inclusion criteria for Group 1 was DS diagnosed and aged between 17 to 35; for Group 2, no DS diagnosed and same age and for Group 3 no DS diagnosed but aged between 55 to 80.

The study is a prospective observational study. It was explained to all the patients, parents, or legal guardians. They agreed to participate through a written confirmed consent which were signed before the beginning of the study. No drug was instilled and no invasive technique was performed.

The tests performed on the subjects involved in the study, included: Visual acuity (VA) test in condition High contrast photopic was assessed using the Lea Symbols 15-Line Distance Chart (Good-Lite. Elgin. IL. U.S.A.) at 3 meters and Lea Symbols Near Vision Card (Good-Lite. Elgin. IL. U.S.A.) at 40 cm. These tests were performed in all participants to avoid differences in the interpretation of the results and in order to be more consistent with the statistical analysis. Preliminarily, a trial was made to confirm all the participants understood what they had to answer. When participants could not verbalize the answer, they pointed at the symbol in a hand card as it is recommended in the instructions of the test. This measurement was made with the habitual prescription - with or without glasses - and with the optimal one, after the refractive exam. Measurements were done monocular and binocularly and recorded in logMAR units. For the analysis of the VA, only binocular values were considered.

The current prescription was measured with a lensometer (LM-6 Topcon Co. Tokyo, Japan) and the refractive error was assessed using an autorefractor (TR4000 Tomey. Nürnberg. Germany), a retinoscope (18100 Welch Allyn. Chicago. U.S.A.) and retinoscopy rulers. After having two objective measurements of the refractive error, it was confirmed with a subjective exam using trial frame and loose lenses. The optimal prescription was registered in sphero-cylindrical form and the lenses that provided the best VA were prescribed. The spherical equivalent (SE) was calculated by adding the sum of the sphere power with half of the cylinder power.

Also, monocular accommodative response was assessed using the push-down method with Lea symbols Cards. All the participants wore the optimal prescription for near distance. A card with a single symbol was presented at 4 cm opposite one eye and then moved away until the participant could identify it. The procedure was repeated three times with different cards in each eye. The distance where the symbols were identified was registered in centimeters and the average of the three measurements was calculated and used as the accommodative response.

Binocular vision was assessed by the Cover test method, applied to evaluate the ocular alignment using an occluder, an accommodative Lea symbol Test for long distance (3 m) and a single Lea symbol target for near distance (40 cm). To measure the deviation prism bars were used. It was registered if there were phoria or tropia, the amount, the direction, the constancy and the eye involved. Near point of convergence (NPC) was recorded with the help of a ruler and a card with a single Lea symbol. It was registered the break and recovery point in centimeters. The level of stereoacuity was measured for near distance using the Titmus Estereopsis Test (Stereo Optical Co. Chicago. U.S.A.). All the measurements were performed wearing the optimal prescription.

Finally, colour vision was analysed, wearing the optimal prescription, with the Ishihara’s Tests for Colour Deficiency 38 Plates Edition 2000 (Kanehara &Co., Ltd. Tokio. Japan) and Album Tritan de Ph. Lanthony (Laboratoire de la vision des couleurs. Centre National d’Ophalmologie des Quinze Vingts. Paris. France).

For the statistical analysis all the data were exported to SPSS 22 version for Windows (Inc. Chicago. U.S.A.). The data are presented as the mean + standard deviation (SD). The measured outcome variables were checked for normality with the Kolmogórov-Smirnov test. Wilcoxon test showed there were no statistically difference between right and left eyes in the refractive error. For the no parametric variables Kruskal-Wallis analysis for independent samples were used. The results obtained in the same subjects Green House-Geisser test were applied. Those variables with p-value of less than 0.05 were considered as having a statistically significant association.

3. Results

The total sample was formed by 192 subjects, 69 young adults with DS (Group 1) and a control group without DS. The control group was subdivided into two other groups, 68 young adults (Group 2) and 55 senior adults (Group 3). The characteristics of the participants are in ‘Table 1’.

The results of the binocular visual acuity at far and near distance. ‘Table 2’ shows the current VA with spectacles if subjects wore them and with the new prescription. Significant differences (p<0.001) were found between the three groups. Group 1 got the lowest VA while Group 2 showed the highest results.

With respect to refractive error, in Group 1, participants had glasses in 82.4% of the cases but 33.9% did not wear them. In Group 2, 66.2% had glasses and 4.4% did not wear them. And, in Group 3 almost all the subjects, 98.2%, had and wore glasses. Statistical analysis showed significant differences between all groups (p<0,001). The data presented in this section correspond to the right eyes since there were no significant differences between both eyes in all groups.

Refractive error found in each group is presented in ‘Table 3’. It shows the sphere, cylinder, spherical equivalent (SE) and range in the current prescription and in the one found after the new refraction. Significant differences (p=0.002) were found between Group 2 and Group 3 in the spherical values in the prescription they wore. Regarding the amount of the cylinder, significant differences (p<0.001) between Group 1 and the others were found. In Group 1, 50% of the participants had cylinder higher than -1.00D. The astigmatism was 50% with the rule, 34.2% against the rule and 15.8% oblique. Significant differences were found between Groups 1 and 2 (p=0.025) and between Groups 1 and 3 (p=0.008).

Considering the spherical equivalent (SE) in Group 1, myopia higher than -1.00D was present in more than 50% of the participants. There were significant differences (p=0.003) between Group 2 and Group 3. The spherical values in the new prescription showed no significant differences between all the groups (p=0.247). Significant differences were found in the amount of the cylinder (p< 0.001) between Group 1 and the others. In Group 1, the new prescription revealed astigmatism up to 1.00D in more than 78% of the participants, a significant difference (p< 0.001) compared with the previous refractive error. In Group 1, the astigmatism was with the rule in 36.2% of the participants, 33.3% against the rule and 30.5% oblique. Considering SE, the prevalence of myopia, in the optimal prescription, was higher than 50% in Group 1, 44% in Group 2 and 34% in Group 3. No significant differences were found (p=0.083) between groups as shown in ‘Table 4’. But, in Group 1, differences (p<0.001) were found between the current and the new prescription (SE and astigmatic error). The same happened in Group 3 for the SE (p=0.023) and the astigmatic error (p=0.041). In Group 2, the new prescription showed more positive values with no significant differences. Regarding the addition for near distance, there was a significant difference (p< 0.001) between Groups 1 and 2 with Group 3.

Strabismus was found in 64.7% of the participants in Group 1, in 55% of the cases were esodeviation. Nystagmus was present in 22.7% of the participants. The statistical differences in both variables with the other two groups were significant (p<0.001). There were no significant differences in the Near Point of Convergence (p=0.439). As it was expected, Group 1 obtained very low results in stereopsis. Only 6% of the participants obtained 140 or less arcsec. There were significant differences between Group 1 and the other two (p<0.001).

4. Discussion

The number of publications about ocular anomalies in adults with DS is very low, hence the importance of this work. Fortunately, the increased life expectancy of people with DS means that they require more medical care throughout their lives, including vision care. To our knowledge, this study is the first in which visual acuity, refractive error, accommodation and binocular vision in young adults with DS have been compared to young adults and seniors without DS. The aim was to evaluate some aspects of visual function in adults with DS and to compare them with the results obtained in young adults and seniors without DS.

As it occurs in other systems in people with DS, premature aging may explain a worse visual function. The current analysis shows that the characteristics of visual function in young adults with DS is more similar to young adults without DS than to seniors. Lower VA, higher refractive errors and strabismus are more frequent in young adults with DS, and this seems not to be related to aging, but to the DS condition. It has been widely published that children with DS have more visual impairments than healthy controls without DS [4,13,31]. The same is observed in adults, but there is less information about them [21,24]. What has been published shows discrepancies in results because there are huge differences in samples and evaluation procedures.

The current study shows that more participants with DS had glasses, but 33.9% of them did not usually wear them. The noncompliance in this group is lower than what has been reported by Adyanthaya and Van Splunder [28,30]. The reason could be a wrong prescription [32] or the fact that DS patients are not aware of the benefits of wearing glasses [28]. In this study, the VA at far and near distance was assessed with the same test in all samples to make consistent analyses. In young adults with DS, the VA was lower than in controls, even with the new prescription, although there was an improvement in 40% of the participants. This could be associated to the neurological anomalies people with DS present, as mentioned before [13,21,22,23]. Refractive error in children with DS develops differently from typical, especially after two years of age [33,34]. The prevalence of myopia and hyperopia mentioned in the literature varies widely – from 4 to 60% [35,36,37]. The myopia values obtained in young adults with DS, were higher than those published by other authors [24,25,28,38], but similar to the results obtained in this study for young adults without DS. This could be related to the kind of near activities they perform in their daily life. As it occurs in general population, near tasks may be associated to myopic progression. Astigmatism was more common in participants with DS compared to the control group, which agrees with other authors’ results. The prevalence was higher than what was found by Ljubic or Anderson [24,39]. In addition, in more than 78% of the participants, the astigmatism values were higher than -1.00D, and in one-third of them was oblique. The increase in the astigmatism values with age in DS has also been mentioned in the literature [25,33]. In this study, astigmatism values higher than -1.00D were present in more than 78% of the participants with DS. Other authors have found values from 66.8% to as high as 94.1% [40]. The most common orientation was oblique in one-third of the group.

Regarding to accommodative response, no significant differences were found between groups of young people with and without DS. It is acknowledged that children with DS are more likely to have accommodative deficits than children with typical development [14,41,42] and young adults with DS might be expected to have them too [42]. But in this study, lower VA at near distance in young adults with DS seems not be related to a lag of accommodation [43]. Accommodative response is one of the most difficult aspects of visual function to evaluate because great collaboration is needed for the assessment. In objective measurements, when subjects have to maintain the focus on the target during the procedure, it is difficult for the examiner to know if they are performing properly or getting tired. That is why the push-down method has been used.

Strabismus was observed in 64.7% of the participants in the DS group. This result is higher than the results published by Adio, Haugen and Creavin [35,38,44]. Moreover, esodeviation was the most frequent deviation, which agrees with previously studies [13].

Nystagmus was found in 22.7% of participants in group with DS, similar to Kim’s article (37), and higher than Fong and Li’s results [21,27]. Nystagmus is reported to affect between 2 and 33.3% of individuals with DS [40]. No significant differences were found in colour vision among the groups and no anomalies have been found as has been stated [45].

A limitation of the study is that, as previously explained, accommodation response was assessed using the push-down method. Thus, the Nott retinoscopy or the push-up methods should be applied to compare the results with different techniques. Moreover, measurement of refractive error using cycloplegic has been mentioned by other authors and, if it had been used, the results could be dissimilar.

In some regards, people with DS need much more help because they are more vulnerable. Nowadays, they have the possibility to develop different jobs to get certain independence and join in social life. We should point out that people with DS sometimes cannot report visual and ocular symptoms because of their communication problems. It is even possible that they feel no pain, or they do not understand that something is wrong. They should have periodic and complete examinations to ensure proper visual function and to prevent future problems before they occur. Professionals must adapt procedures individually and consider that people with DS may need more time to answer, more breaks during the evaluation or shorter session. This will ensure a correct diagnosis and treatment management. The results obtained in this study show that more than 40% of the DS participants improved their VA with the optimal prescription and that the accommodation is similar to young adults without DS.

People with intellectual disabilities may achieve a better performance if they have a better visual function and they enhance their quality of life. Health systems should provide vision care programmes to this special population.

Author Contributions

Conceptualization, Y. M-P. and C. S-R.; methodology, Y M-P., C. S-R. and G G-M.; formal analysis, Y M-P., C. S-R. and G G-M.; investigation, G. G-M., A. G-H. and Y. M-P.; resources, Y M-P., C. S-R. and G. G-M.; writing—original draft preparation, Y M-P. G G-M. and A G-H.; writing—review and editing, Y M-P., C S-R. and V B-S.; supervision, Y M-P., C. S-R, V B-S. and G G-M.. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

The study was conducted according to the guidelines of the Declaration of Helsinki, and approved by Ethics Committee of Hospital Clínico San Carlos in Madrid (Spain) (protocol code 141/359-E, approved on November 24th, 2011).

Informed Consent Statement

Informed consent was obtained from all subjects involved in the study. If any participant had a tutor o legal guardian, they were who signed the consent.

Acknowledgments

the authors want to thank all the participants for their collaboration, as well as their families. Special thanks to Aprocor and all the staff for the facilities to develop this study. Authors also want to thank the Statistical Department of Complutense University of Madrid.

Conflicts of Interest

the authors declare no conflict of interest.

References

Dierssen, M. Down syndrome: the brain in trisomic mode. Nat. Rev. Neurosci. 2012, 13, 844–858. [Google Scholar] [CrossRef]
Borrel Martínez JM, Flórez Beledo J, Serés Santamaría. A, Fernández Delgado R, Albert Álvarez J, Prieto Santos C, et al. Programa español de salud para personas con Síndrome de Down.
Capone, G.; Stephens, M.; Santoro, S.; Chicoine, B.; Bulova, P.; Peterson, M.; et al. Co-occurring medical conditions in adults with Down syndrome: A systematic review toward the development of health care guidelines. Part II. Am J Med Genet A. 2020, 182, 1832–1845. [Google Scholar] [CrossRef]
Stirn Kranjc, B. Ocular abnormalities and systemic disease in Down syndrome. - Strabismus.2012 Jun;20(2):74-7. JUN(1744-5132 (Electronic); 0927-3972 (Linking)). [CrossRef]
Carfã¬, A.; Antocicco, M.; Brandi, V.; Cipriani, C.; Fiore, F.; Mascia, D.; Settanni, S.; Vetrano, D.L.; Bernabei, R.; Onder, G. Characteristics of Adults with Down Syndrome: Prevalence of Age-Related Conditions. Front. Med. 2014, 1, 51. [Google Scholar] [CrossRef]
Määttä, T.; Määttä, J.; Tervo-Määttä, T.; Taanila, A.; Kaski, M.; Iivanainen, M. Healthcare and guidelines: A population-based survey of recorded medical problems and health surveillance for people with Down syndrome. J. Intellect. Dev. Disabil. 2011, 36, 118–126. [Google Scholar] [CrossRef]
Bittles, A.H.; Glasson, E.J. Clinical, social, and ethical implications of changing life expectancy in Down syndrome. Dev Med Child Neurol. 2004, 46, 282–286. [Google Scholar] [CrossRef]
Jensen, K.M.; Davis, M.M. Health care in adults with Down syndrome: a longitudinal cohort study. J. Intellect. Disabil. Res. 2012, 57, 947–958. [Google Scholar] [CrossRef]
Ailey, S.H.; Brown, P.J.; Ridge, C.M. Improving hospital care of patients with intellectual and developmental disabilities. Disabil. Heal. J. 2017, 10, 169–172. [Google Scholar] [CrossRef]
Caron, RM. Systems of health care delivery: community setting. In: Health care for people with intellectual and developmental disabilities across the lifespan. Springer; 2016. p. 185-94.
Lewis, M.A.; E Lewis, C.; Leake, B.; King, B.H.; Lindemann, R. The quality of health care for adults with developmental disabilities. Public Heal. Rep. 2002, 117, 174–184. [Google Scholar] [CrossRef]
Tomita, K.; Tsurui, H.; Otsuka, S.; Kato, K.; Kimura, A.; Shiraishi, Y.; Shinbo, Y.; Takada, K.; Tomita, A.; Nomi, Y. [Ocular findings in 304 children with Down syndrome]. Nippon Ganka Gakkai zasshi 2013, 117, 749–760. [Google Scholar]
Watt, T.; Robertson, K.; Jacobs, R.J. Refractive error, binocular vision and accommodation of children with Down syndrome. Clin. Exp. Optom. 2015, 98, 3–11. [Google Scholar] [CrossRef]
Mohd-Ali, B.; Mohammed, Z.; Norlaila; Mohd-Fadzil, N.; Rohani, C.C.; Mohidin, N. Visual and binocular status of Down syndrome children in Malaysia. Clin. Exp. Optom. 2006, 89, 150–154. [Google Scholar] [CrossRef] [PubMed]
Paudel, N.; Leat, S.J.; Adhikari, P.; Woodhouse, J.M.; Shrestha, J.B. Visual defects in Nepalese children with Down syndrome. Clin. Exp. Optom. 2010, 93, 83–90. [Google Scholar] [CrossRef] [PubMed]
Ugurlu, A.; Altinkurt, E. Ophthalmologic Manifestations and Retinal Findings in Children with Down Syndrome. J. Ophthalmol. 2020, 2020, 9726261–6. [Google Scholar] [CrossRef]
Terai, T.; Eda, S.; Sugasawa, J.; Tonari, M.; Matsuo, J.; Oku, H.; Ikeda, T. Ocular findings in Japanese children with Down syndrome: the course of visual acuity and refraction, and systemic and ocular anomalies. Clin. Ophthalmol. 2018, ume 12, 1637–1643. [Google Scholar] [CrossRef]
Postolache, L.; Monier, A.; Lhoir, S. Neuro-Ophthalmological Manifestations in Children with Down Syndrome: Current Perspectives. Eye Brain 2021, ume 13, 193–203. [Google Scholar] [CrossRef]
Haseeb, A.; Huynh, E.; ElSheikh, R.H.; ElHawary, A.S.; Scelfo, C.; Ledoux, D.M.; Maidana, D.E.; Elhusseiny, A.M. Down syndrome: a review of ocular manifestations. Ther. Adv. Ophthalmol. 2022, 14. [Google Scholar] [CrossRef] [PubMed]
Bermudez, B.E.B.V.; Amaral, M.E.d.S.D.; Gomes, C.d.S.; Novadzki, I.M.; Oliveira, C.M.; Serpe, C.C. Ophthalmological abnormalities in Down syndrome among Brazilian patients. Am. J. Med Genet. Part A 2020, 182, 2641–2645. [Google Scholar] [CrossRef]
Fong, A.H.C.; Shum, J.; Ng, A.L.K.; Li, K.K.W.; McGhee, S.; Wong, D. Prevalence of ocular abnormalities in adults with Down syndrome in Hong Kong. Br. J. Ophthalmol. 2013, 97, 423–428. [Google Scholar] [CrossRef]
Ikeda, K.; Kasugai, H.; Yamaguchi, A.; Uchino, Y.; Katase, H.; Kanno, A. Visual perceptual strengths and weaknesses in adults with intellectual disabilities compared with a birth year-matched norm. J. Intellect. Disabil. Res. 2012, 57, 67–79. [Google Scholar] [CrossRef]
Krinsky-McHale, S.J.; Silverman, W.; Gordon, J.; Devenny, D.A.; Oley, N.; Abramov, I. Vision Deficits in Adults with Down Syndrome. J. Appl. Res. Intellect. Disabil. 2013, 27, 247–263. [Google Scholar] [CrossRef]
Ljubic, A.; Trajkovski, V. Refractive errors in children and young adults with Down’s syndrome. Acta Ophthalmol. 2009, 89, 324–327. [Google Scholar] [CrossRef] [PubMed]
Muñoz-Ortiz, J.; Charry-Sánchez, J.D.; Bechara-Arango, I.; Blanco-Becerra, M.; Talero-Gutiérrez, C.; Gomez-Suarez, M.; De-La-Torre, A. Prevalence of ophthalmological manifestations in pediatric and adolescent populations with Down syndrome: a systematic review of the literature. Syst. Rev. 2022, 11, 1–13. [Google Scholar] [CrossRef] [PubMed]
Haveman, M.; Perry, J.; Salvador-Carulla, L.; Walsh, P.N.; Kerr, M.; Valk, H.V.S.L.-D.; Van Hove, G.; Berger, D.M.; Azema, B.; Buono, S.; et al. Ageing and health status in adults with intellectual disabilities: Results of the European POMONA II study. J. Intellect. Dev. Disabil. 2011, 36, 49–60. [Google Scholar] [CrossRef]
Li, J.C.; Wong, K.; Park, A.S.; Fricke, T.R.; Jackson, A.J. The challenges of providing eye care for adults with intellectual disabilities. Clin. Exp. Optom. 2015, 98, 420–429. [Google Scholar] [CrossRef]
Adyanthaya, R.; Isenor, S.; Muthusamy, B.; Irsch, K.; Guyton, D.L. Children with Down syndrome benefit from bifocals as evidenced by increased compliance with spectacle wear. J. Am. Assoc. Pediatr. Ophthalmol. Strabismus 2014, 18, 481–484. [Google Scholar] [CrossRef] [PubMed]
Nandakumar, K.; Leat, S.J. Bifocals in children with Down syndrome (BiDS) - visual acuity, accommodation and early literacy skills. Acta Ophthalmol. 2010, 88, e196–e204. [Google Scholar] [CrossRef]
van Splunder, J.; Stilma, J.S.; Bernsen, R.M.D.; Evenhuis, H.M. Prevalence of visual impairment in adults with intellectual disabilities in the Netherlands: cross-sectional study. Eye 2005, 20, 1004–1010. [Google Scholar] [CrossRef]
Tomita, K. Visual characteristics of children with Down syndrome. Jpn. J. Ophthalmol. 2017, 61, 271–279. [Google Scholar] [CrossRef]
Stewart, R.E.; Margaret Woodhouse, J.; Trojanowska, L.D. In focus: the use of bifocal spectacles with children with Down’s syndrome. Ophthalmic Physiol Opt. 2005, 25, 514–522. [Google Scholar] [CrossRef]
Woodhouse, J.M.; Pakeman, V.H.; Cregg, M.; Saunders, K.J.; Parker, M.; Fraser, W.I.; Sastry, P.; Lobo, S. Refractive Errors in Young Children with Down Syndrome. Optom. Vis. Sci. 1997, 74, 844–851. [Google Scholar] [CrossRef]
Al-Bagdady, M.; Murphy, P.J.; Woodhouse, J.M. Development and distribution of refractive error in children with Down’s syndrome. Br J Ophthalmol. 2011, 95, 1091–1097. [Google Scholar] [CrossRef] [PubMed]
Adio, A.O.; Wajuihian, S.O. Ophthalmic manifestations of children with Down syndrome in Port Harcourt, Nigeria. Clin Ophthalmol. 2012, 6, 1859–1864. [Google Scholar] [CrossRef] [PubMed]
Felius, J.; Beauchamp, C.L.; Stager, D.R.S. Visual acuity deficits in children with nystagmus and Down syndrome. Am J Ophthalmol. 2014, 157, 458–463. [Google Scholar] [CrossRef] [PubMed]
Kim, J.H.; Hwang, J.-M.; Kim, H.J.; Yu, Y.S. Characteristic ocular findings in Asian children with Down syndrome. Eye 2002, 16, 710–714. [Google Scholar] [CrossRef]
Creavin, A.L.; Brown, R.D. Ophthalmic assessment of children with down syndrome: is England doing its bit? Strabismus. 2010, 18, 142–145. [Google Scholar] [CrossRef]
Anderson, H.A.; Manny, R.E.; Glasser, A.; Stuebing, K.K. Static and Dynamic Measurements of Accommodation in Individuals with Down Syndrome. Investig. Opthalmology Vis. Sci. 2011, 52, 310–317. [Google Scholar] [CrossRef]
Mathan, J.J.; Simkin, S.K.; Gokul, A.; McGhee, C.N.J. Down syndrome and the eye: Ocular characteristics and ocular assessment. Surv. Ophthalmol. 2022, 67, 1631–1646. [Google Scholar] [CrossRef]
Cregg, M.; Woodhouse, J.M.; Pakeman, V.H.; Saunders, K.; Gunter, H.L.; Parker, M.; I Fraser, W.; Sastry, P. Accommodation and refractive error in children with Down syndrome: cross-sectional and longitudinal studies. Investig. Ophthalmol. Vis. Sci. 2001, 42, 55–63. [Google Scholar]
Doyle, L.; Saunders, K.J.; Little, J.-A. Determining the relative contribution of retinal disparity and blur cues to ocular accommodation in Down syndrome. Sci. Rep. 2017, 7, 39860. [Google Scholar] [CrossRef]
Satgunam, P.; Datta, S.; Sumalini, R. Near vision in individuals with Down syndrome: a vision screening study. Eye 2019, 33, 1254–1260. [Google Scholar] [CrossRef]
Haugen, O.H.; Høvding, G.; Eide, G.E. Biometric measurements of the eyes in teenagers and young adults with Down syndrome. Acta Ophthalmol. Scand. 2001, 79, 616–625. [Google Scholar] [CrossRef] [PubMed]
Suttle, C.M.; Lloyd, R. Chromatic and achromatic transient VEPs in adults with Down syndrome. Ophthalmic Physiol. Opt. 2005, 25, 501–513. [Google Scholar] [CrossRef] [PubMed]

Table 1. Demographics of the participants.

	Groups	n	Age (years) Range	Mean age (SD)	Gender
Male n (%)	Female n (%)
Subjects with Down syndrome	Group 1	69	17-35	27.6 + 3.9	24 (34.8)	45 (65.2)
Subjects without Down syndrome (control)	Group 2	68	19-34	22.4 + 2.6	17 (25)	51 (75)
Group 3	55	55-79	63.4 + 5.7	26 (47.2)	29 (52.8)

Group 1: young adults with Down syndrome; Group 2: young adults without Down syndrome; Group 3: seniors without Down syndrome. SD: standard deviation.

Table 2. Presenting visual acuity and with the new prescription at far and near distance.

Presenting visual acuity and with the new prescription
FAR DISTANCE
	Presenting VA (logMAR)	Range	New VA (logMAR)	Range
	0.24 ± 0.18***	0.8 to -0.1	0.15 ± 0.10***	0.8 to -0.1
Group 2	-0.16 ± 0.0***	0.2 to -0.12	-0.18 ± 0.00***	0.2 to -0.2
Group 3	0.0 ± 0.10***	0.2 to -0.1	-0.02 ± 0.00***	0.2 to -0.1
NEAR DISTANCE
	Presenting VA (logMAR)	Range	New VA (logMAR)	Range
Group 1	0.23 ± 0.10***	0.6 to 0.0	0.16 ± 0.10***	0.6 to -0.05
Group 2	-0.06 ± 0.10***	0.2 to -0.1	-0.06 ± 0.10***	0.2 to -0.1
Group 3	0.01 ± 0.00***	0.2 to -0.1	0.00 ± 0.00***	0.15 to -0.1

VA: Visual Acuity. Group 1: young people with Down syndrome; Group 2: young people without Down syndrome; Group 3: seniors without Down syndrome. (***p<0.001).

Table 3. Presenting and optimal prescription.

Groups	Presenting Prescription
Groups	Mean Sphere (D) ± SD	Range (D)	Mean Cylinder (D) ± SD	Range (D)	SE
Group 1	-1.00 ± 4.23	+7.00; -14.00	-1.16 ± 1.02***	0.00; -3.25	-1.33 ± 3.95
Group 2	-1.19 ± 2.59**	+6.00; -11.25	-0.38 ± 0.67***	0.00; -3.50	-1.38 ± 2.66**
Group 3	0.11 ± 1.36**	+3.50; -4.50	-0.57 ± 0.68***	0.00; -3.00	-0.17 ± 1.35**
	Optimal Prescription
	Mean Sphere (D)±SD	Range (D)	Mean Cylinder (D)±SD	Range (D)	SE
Group 1	-1.05 ± 4.20	+7.00; -15.00	-1.73 ± 1.00***	0.00; -4.00	-1.92 ± 4.20
Group 2	-0.82 ± 2.60	+6.00; -10.50	-0.45 ± 0.60***	0.00; -3.50	-1.05 ± 2.70
Group 3	0.00 ± 1.40	+3.50; -4.50	-0.55 ± 0.60***	0.00; -2.50	-0.27 ± 1.40

Group 1: young adults with Down syndrome; Group 2: young adults without Down syndrome; Group 3: seniors without Down syndrome. D: Diopter; SD: Standard Deviation; SE: Spherical Equivalent. (**p<0.01) (***p<0.001).

Table 4. Refractive error in the presenting and optimal prescription.

	Presenting prescription			Optimal prescription
	Hyperopia ≥ +1.00D	Emmetropia	Myopia ≤ -1.00D	Hyperopia ≥ +1.00D	Emmetropia	Myopia ≤ -1.00D
	n (%)	n (%)	n (%)	n (%)	n (%)	n (%)
Group 1	13 (18.8)	35 (50.7)	21 (30.4)	17 (24.5)	17 (24.6)	35 (50.9)
Group 2	4 (5.9)	32 (47.1)	32 (47.0)	17 (25)	21 (30.9)	30 (44.1)
Group 3	12 (21.8)	17 (30.9)	26 (47.3)	15 (27.3)	21 (38.2)	19 (34.5)

D: Diopter. Group 1: young adults with Down syndrome; Group 2: young adults without Down syndrome; Group 3: seniors without Down syndrome.

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