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Refractive errors in albino children in Brazzaville

Nganga Ngabou Charles Géraud Fredy

University Marien Ngouabi, Brazzaville, Republic of Congo

Department of Ophthalmology, University Hospital of Brazzaville, Brazzaville, Republic of Congo

Makita Chantal

University Marien Ngouabi, Brazzaville, Republic of Congo

Department of Ophthalmology, University Hospital of Brazzaville, Brazzaville, Republic of Congo

Adiba Fene Samuel

Clinic of Ophthalmology, Brazzaville, Republic of Congo

Kambourou Judicaël

University Marien Ngouabi, Brazzaville, Republic of Congo

Department of Paediatrics, University Hospital of Brazzaville

Onka Vissimy

Department of Ophthalmology, University Hospital of Brazzaville, Brazzaville, Republic of Congo

Clinic of Ophthalmology, Brazzaville, Republic of Congo

DOI: 10.15761/NFO.1000229

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Abstract

We evaluated refractive disorders in Albino children of Brazzaville and assessed their impact on the visual acuity of these children.

Patients and method

Our study was conducted at the University Hospital of Brazzaville in October 2018 as part of a special program of the Congolese Association of Albinos aimed at providing glasses free of charge to albino children. This was a cross-sectional study of 32 children with oculocutaneous albinism.

All children received a complete ophthalmological examination. Ametropia was measured by cycloplegic autorefraction performed approximately 45-60 minutes after topical instillation of 3 drops of 1% cyclopentolate administered 5 minutes apart.

Results

All children had nystagmus, including 2 cases with strabismus (6.25%). All children had astigmatism, 56.25% of whom were hypermetropic. The mean corrected visual acuity in the better eye was 0.18+/-0.14. The Mean uncorrected visual acuity in the better eye was 0.33+/-0.15. The improvement in visual acuity after correction was statistically significant P=0.002.

Conclusion

Albinism is associated with a variety of ocular anomalies including ametropia. Hypermetropic astigmatism was the most common refractive error identified in our series. Correction of this ametropia results in a statistically significant improvement in visual acuity.

Key words

albinism, refraction errors, children

Introduction

Albinism is a group of inherited disorders that are characterized by a reduction or absence of melanin pigment in tissues, in conjunction with ocular and visual pathway developmental abnormalities. The most characteristic manifestation of albinism is related to hypopigmentation in the visual system and/or the skin and teguments. This lack of production of melanin is associated with specific changes in the eye such as foveal hypoplasia and misrouting of optic fibres from the retina to the visual cortex [1].

These changes explain the low visual acuity that presents from birth. In addition, albinism is also associated with refractive disorders and reduced visual acuity [2].

The purpose of this study is to determine the refractive disorders in children of Albino Brazzaville and to appreciate their impact on the visual acuity of these children.

Patients and methods

Patients

Our study was conducted at the University Hospital of Brazzaville in October 2018 as part of a special program of the Congolese Association of Albinos aimed at providing glasses free of charge to albino children.

Method

This was a cross-sectional study of 32 children with oculocutaneous albinism.

All the selected children benefited from a complete ophthalmological examination. We used the best subjective corrected visual acuity and performed a detailed anatomical examination. Ametropia was measured by cycloplegic autorefraction performed approximately 45-60 minutes after topical instillation of 3 drops of 1% cyclopentolate administered 5 minutes apart [3].

A second assessment of visual acuity was performed the next day with optical correction.

We used the WHO classification of visual impairment [4-6] taking the best corrected vision in the better eye into account:

- Mild Visual Impairment: Visual acuity between 6/12 and 6/18 (between 0.5 and 0.3)

- Moderate Visual Impairment: Visual acuity between 6/18 and 6/60 (between 0.3 and 0.1)

- Severe visual impairment: Visual acuity between 6/60 and 3/60 (between 0.1 and 0.05)

- Blindness: Visual acuity worse than 3/60 (less than 0.05)

Since visual impairment and blindness are defined by considering the visual acuity of the better eye, our work was done separately on both eyes [5].

Statistical analyses

We used EPI INFO 7 for statistical analysis. Comparisons were carried out using Excel software by performing equality tests on paired predictions in one eye and on unpaired predictions in both eyes after comparing variances. The confidence interval was 95%.

Results

Our study included 12 boys and 20 girls, a sex ratio of 0.6. The average age was 12+/-3.06 (5 to 15 years old). All children had nystagmus, including 2 cases with strabismus (6.25%) (Table 1).

Table 1. Types of Ametropia

Types of Ametropia

Number of cases

%

Hypermetropia

0

0

Myopia

0

0

Simple Hypermetropic Astigmatism

8

25

Compound Hypermetropic Astigmatism

10

31.25

Mixed Astigmatism

2

6.25

Simple Myopic Astigmatism

0

0

Composed Myopic Astigmatism

12

37.5

Total

32

100

The mean uncorrected visual acuity in the better eye was 0.18+/-0.14. The mean corrected visual acuity in the better eye was 0.33+/-0.15. The improvement in corrected visual acuity was statistically significant P=0.002. The mean corrected visual acuity of the contralateral eye 0.25+/-0.15. The difference in the mean visual acuity of the two eyes was not statistically significant (Table 2).

 Table 2. Classification of patients based on visual acuity

 

Uncorrected in the better eye

Corrected in the better eye

Corrected in the contralateral eye

No Visual Impairment

0 (0%)

0 (0%)

0 (0%)

Minimal Visual Impairment

8 (25%)

17 (53.13%)

10 (31.25%)

Moderate Visual Impairment

8 (25%)

9 (28.1/3%)

12 (37.5%)

Severe Visual Impairment

9 (28.13%)

4 (12.5%)

10 (31.25%)

Blindness

7 (21.88%)

2 (6.25%)

0 (0%)

Total

32 (100%)

32 (100%)

32 (100%)

Discussion

Our study included 12 boys and 20 girls, a sex ratio of 0.6. Two Cameroonian studies Eballe and Aboubacar respectively found a sex ratio of 1.33 for men and 0.5 for women [7,8]. There is no gender predominance in albinism. these sex ratio variations, are probably random cases.

The average age in our study was 12+/-3.06 years old, which is consistent with the fact that we only worked with on patients with 15 years of age or less. In the literature, however, the average age is generally low, 18 for Gargouri in Tunisia, 24 and 13 for Aboubacar and Ebana in Cameroon [8-10]. The latter had evoked a low life expectancy among African albinos, which had already been demonstrated by Madelain [11]. Nystagmus was present in 100% of patients according to the literature [7-10,12].

Two children had a strabismus or 6.25%, this rate is a little lower than that findings in the literature. Khanal and Gargouri respectively found 16% and 13%. Strabismus affected 2 children out of 32, or 6.25% of cases. Khanal noted 16% of strabismus, and Gargouri 13.88% [9,12].

Astigmatism was present in all patients. No patient had isolated spherical ametropia. Spherical ametropia associated with astigmatism were dominated by farsightedness which accounted for 56.25% of cases, against myopia with 37.5% of cases. Gargouri also found 100% astigmatism, associated with 59% hyperopia and 41% myopia [9]. Ebana found 86.7% astigmatism, 9.53% myopia and 2.38% Hypermetropia [10].

The mean uncorrected visual acuity in the better eye was 0.18+/-0.14 and corrected visual acuity in the better eye was 0.33+/-0.15 considering the best corrected vision. All patients had a visual acuity of 5/10 or less. These results are better than Cameroonian studies with mean corrected visual acuity of 0.15+/-0.08 for Eballe and 0.27+/-0.13 for Aboubacar. This is explained by the fact that they included only albinos who presented themselves in consultation. In contrast, in our series we selected patients amongst an albino association.

The visual acuity improvement provided by the optical correction was clinically significant. This improvement was also found by authors in the literature [7,13,14]

Although the average corrected visual acuity was greater than the better eye compared to the contralateral eye, the difference was not clinically significant. This makes it possible to evoke a symmetric disorder a priori.

These results allow us to classify patients according to their level of vision:

- All patients had visual impairment,

- Without correction only 25% reached 0.3 of visual acuity,

- With correction 53% had a visual acuity between 0.3 and 0.5,

- Despite the correction, 18.75% of children still had severe visual impairment or remained blind.

Gargouri reports 36% of patients with visual acuity greater than 3/10. Aboubacar also noted a maximum visual acuity at 0.5 [8.9].

Conclusion

Albinism is associated with a variety of ocular anomalies including ametropia. Hypermetropic astigmatism was the most common refractive error identified in our series. Correction of this ametropia results in a statistically significant improvement in visual acuity. Despite this improvement, patients remain visually impaired. The patients must be optically corrected and be informed of realistic expectations.

References

  1. Aquaron R (2000) L’albinisme humain: aspects cliniques, génétiques, cellulaires, biochimiques et moléculaires. Med Trop 60: 331-341.
  2. Wildsoet CF, Oswald PJ, Clark S (2000) Albinism: its implications for refractive development. Invest Ophthalmol Vis Sci 41: 1-7.
  3. Sellami L, Le Lez ML, Santallier M, Thuault S, Madern F, et al. (2002) Étude de la réfraction sous cycloplégie: 2 gouttes de cyclopentolate versus 3 gouttes. J F Ophtalmol 25: 142.
  4. Blindness and vision impairment, World Health Organization 2018. www.who.int/news-room/fact-sheets/detail/ blindness-and-visual-impairment.
  5. Bourne RRA, Flaxman SR, Braithwaite T, Cicinelli MV, Das A (2017) Magnitude, temporal trends, and projections of the global prevalence of blindness and distance and near vision impairment: a systematic review and meta-analysis. Lancet Glob Health 5: 888-897. [Crossref]
  6. Stevens G, White R, Flaxman SR (2013) Global prevalence of visual impairment and blindness: magnitude and temporal trends, 1990-2010. Ophthalmology 120: 2377-2384. [Crossref]
  7. Eballe AO, Mvogo CE, Noche C, Zoua MEA, Viola-Dohvoma A (2013) Refractive errors in Cameroonians diagnosed with complete oculocutaneous albinism. Clin Ophthalmol 7: 1491-1495. [Crossref]
  8. Aboubakar H, Dohvoma V, Ebana Mvogo S, Malla G, Ndongo JA (2017) Les Caractéristiques du Nystagmus chez le Sujet Albinos Camerounais. Health Sci Dis 18: 25-28.
  9. Gargouri S, Kaibi L, Sakka M, Abib L, Sallami D, et al. (2017) La prise en charge optique des albinos en Tunisie. J I M Sfax 25: 40-44.
  10. Mvogo CE, Bella-Hiag AL, Ellong A, Mbarga BM (1999) Les troubles visuels de l’albinos, étude hospitalière réalisée à l’Hôpital général de Douala. Cahiers santé 9: 89-91.
  11. Madelain J, Turut P (1989) Albinisme: signes, diagnostic et traitement. L’ophtalmologie en question 1: 3-20.
  12. Khanal S, Pokharel A, Kandel H (2016) Visual deficits in Nepalese patients with oculocutaneous albinism. J Optom 9: 102-109. [Crossref]
  13. Rymer J, Choh V, Bharadwaj S, Padmanabhan V, Modilevsky L, et al. (2007) The albino chick as à model for studying ocular developmental anomalies, including refractive errors, associated with albinism. Exp Eye Res 85: 431-442. [Crossref]
  1. Yahalom C, Tzur V, Blumenfeld A (2012) Refractive profile in oculo-cutaneous albinism and its correlation with final visual outcome. Br J Ophthalmol 96: 537-539. [Crossref]

Editorial Information

Editor-in-Chief

James B. Aguayo-Martel
California Northstate University College of Medicine USA

Article Type

Review Article

Publication history

Received date: February 25, 2019
Accepted date: March 08, 2019
Published date: March 11, 2019

Copyright

©2019 Fredy NNCG. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Citation

Fredy NNCG, Chantal M, Samuel AF, Judicaël K, Vissimy O (2019) Refractive errors in albino children in Brazzaville. New Front Ophthalmol 5: DOI: 10.15761/NFO.1000229

Corresponding author

NNCG Fredy

Department of Ophthalmology, University Hospital of Brazzaville, Brazzaville, Republic of Congo

E-mail : bhuvaneswari.bibleraaj@uhsm.nhs.uk

Table 1. Types of Ametropia

Types of Ametropia

Number of cases

%

Hypermetropia

0

0

Myopia

0

0

Simple Hypermetropic Astigmatism

8

25

Compound Hypermetropic Astigmatism

10

31.25

Mixed Astigmatism

2

6.25

Simple Myopic Astigmatism

0

0

Composed Myopic Astigmatism

12

37.5

Total

32

100

 Table 2. Classification of patients based on visual acuity

 

Uncorrected in the better eye

Corrected in the better eye

Corrected in the contralateral eye

No Visual Impairment

0 (0%)

0 (0%)

0 (0%)

Minimal Visual Impairment

8 (25%)

17 (53.13%)

10 (31.25%)

Moderate Visual Impairment

8 (25%)

9 (28.1/3%)

12 (37.5%)

Severe Visual Impairment

9 (28.13%)

4 (12.5%)

10 (31.25%)

Blindness

7 (21.88%)

2 (6.25%)

0 (0%)

Total

32 (100%)

32 (100%)

32 (100%)