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ORIGINAL ARTICLE
Year : 2019  |  Volume : 11  |  Issue : 1  |  Page : 8-13

Role of inheritance and causes of childhood blindness: A multicenter study in Sudan


1 Department of Optometry, Faculty of Optometry and Visual Science, Alneelain University, Khartoum, Sudan; Department of Optometry, College of Applied Medical Sciences, Qassim Medical University, QUSA, CAMS, Buraidha, Saudi Arabia
2 Department of Optometry, Faculty of Optometry and Visual Science, Alneelain University, Khartoum, Sudan
3 Department of Ophthalmology, Qassim Medical University, Al Qassim, Buraidha, Saudi Arabia
4 Department of Ophthalmology, King Fahd Specialist Hospital, Buraidha, Saudi Arabia; Department of Ophthalmology, Services Hospital, Services Institute of Medical Sciences, Lahore, Pakistan

Date of Submission05-May-2019
Date of Decision14-Jul-2019
Date of Acceptance15-Jul-2019
Date of Web Publication10-Oct-2019

Correspondence Address:
Dr. Muhammad Ijaz Ahmad
Department of Ophthalmology, Qassim Medical University, Al Qassim
Saudi Arabia
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DOI: 10.4103/sjopthal.sjopthal_10_19

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  Abstract 


Aim: This study aims to study the causes of childhood blindness (CB), the impact of consanguineous marriage, and the role of inheritance. Methods: This was a cross-sectional observational study conducted in Khartoum State at Sudanese National Association of the Blinds, Alnoor Institute and Umbada Center for the Blinds. Individuals whose visual acuity was 3/60 or less were registered as blind since birth were included in the study.Demographic data and history, Snellen, visual acuity test, both subjective and objective refraction, and a questionnaire were used to assess the family history of blindness and parents' relationship. Results: Infantile blindness was found greater (75.8%) in Sudanese male than females (24.2%) population; (χ2 = 32.03, P = 0.000). Most of the participants' age (62.5%) was <5 years (χ2 = 7.5, P = 0.006) and ranged between 8 and 42 with a mean of 23.1 ± 8.1-year-old. The most frequent causes of infantile blindness were found to be congenital cataract (28.3%), corneal abnormalities (28.3%), optic nerve defects (27.5%) followed by retinal abnormalities (5.83%) and structural abnormalities (3.33%); however, 6.67% of the participants were without obvious ocular anatomical defects (χ2 = 56.5, P = 0.000). Most of the participants (69.2%) showed a positive family history of blindness (χ2 = 17.63, P = 0.000) and in 92.6% of the participants, the parents were related to each other (71.7% had 1st degree cousins; 9.2% 2nd degree cousins; 11.7% far relationship, (χ2 = 139.8, P = 0.000).Inherited factors were found in 65% of participants who were born blind (49.2% autosomal recessive, 5% autosomal dominant, 10.8% Xlinked whereas 35% were isolated cases, (χ2 = 61.67, P = 0.000). Conclusion: Most of the causes of CB are avoidable or preventable. Structured strategies should be developed for screening, referring, and early diagnosis with genetic analysis awareness among communities.Inherited disorders are still counted as significant causes among CB group. Raising health risks of consanguineous marriage might well help in avoidance of such blindness. However, screening, early detection, and rehabilitation programs will reduce the harm of such causes in children.

Keywords: Blindness, childhood, inheritance


How to cite this article:
Elmadina AM, Elrahman NM, Ahmad MI, Qureshi MA, Elawad ME, Bhatti AA. Role of inheritance and causes of childhood blindness: A multicenter study in Sudan. Sudanese J Ophthalmol 2019;11:8-13

How to cite this URL:
Elmadina AM, Elrahman NM, Ahmad MI, Qureshi MA, Elawad ME, Bhatti AA. Role of inheritance and causes of childhood blindness: A multicenter study in Sudan. Sudanese J Ophthalmol [serial online] 2019 [cited 2019 Oct 18];11:8-13. Available from: http://www.sjopthal.net/text.asp?2019/11/1/8/268791




  Introduction Top


A variety of diseases or insults can lead to childhood blindness (CB)/severe visual impairment, and these vary from location to location. Many conditions need early detection and (an appropriate intervention) prevention so that visual impairment from amblyopia can be (avoided) prevented.

The visual loss not only affects the child's psychological, educational, and socioeconomic issues during the childhood years but for most of the times years after too.[1] Visual impairment in children can present solely, or it could be associated with other sensory or motor weakening.

Visual impairment in the children has many other issues different from the adults because 80% of overall causes of blindness are generally avoidable,[2] but in children, even <50% of the causes are avoidable.[3] Due to this reason that CB is one of the five priority areas for special consideration that have been focused up in the Vision 2020: The Right to Sight initiative.[4] That is why the proportion of visually impaired children that needs rehabilitative services is significantly higher as compared to adults.

CB is a very strong indicator regarding the state of child health and other primary care services available in any country. Different studies conducted have concluded that the prevalence of CB is closely related to the economic status of the country and the under-five mortality rate.[3] That is why using the under-five mortality rates as a proxy measure, now the prevalence of CB in different regions of the world can be estimated.[5]

The World Health Organization (WHO) defines CB and visual impairment as best-corrected visual acuity of <3/60 (blindness) and <6/60–3/60 (visual impairment) in the better eye among those aged 0–15 years.[6] Recent estimates show that there are 19 million children who are visually impaired globally, out of which 1.26 million children are blind.[7] Considering the importance of this issue, the control of CB is one of the priorities of Vision 2020: The Right to Sight, and there are many reasons to do this.[8] In children, the causes of blindness are very different in comparison with adults, so the strategies to combat blindness in adults may not be helpful to control the blindness in children. Also, in the children, delay in treatment can lead to resistant amblyopia, but there is no such situation in adults. The global estimates indicate that in near past the CB is responsible for 3.64% of all blindness.[6] It looks like that this number is very small, but the critical importance of CB cannot be ignored because during the life span of the blind child the number of years a child lives with blindness is far more in comparison to adults, that is why these children need special attention. This situation has led to the new concept of “blind years” and “blind years saved.”[2] A recent study has shown CB results in 11.2 million blind person-years in comparison to 22.5 million blind person-years for age-related cataracts and 5.5 million blind person-years for glaucoma.[9] Considering the critical importance of CB, it is said that restoring the sight of one child blind from cataract is equivalent to restoring the sight of 10 older adults blind from cataract.[2]


  Methods Top


The study was approved by the Institutional Review Board of Alneelain University Research Ethical Committee and University Eye Hospital.

A cross-sectional observational study conducted in Khartoum State at Sudanese National Association of the Blinds, Alnoor Institute and Umbada Center for The Blinds from the period 2009–2015. Permission was taken from the center's manager at which the study was performed, and verbal consent was obtained from each participant. A total of 211 participants were screened for selection, and all the details about family history and birth history were taken. All the examination was carried out by ophthalmologist and senior optometrists. Out of which 120 (56.87%) met criteria of blindness since birth and whose vision was 3/60 or less. Visual acuity was measured by the optometrist using the Snellen chart with full optimum room illumination char and detailed ophthalmic examination was carried out by an ophthalmologist using a slit lamp and Volk lens. A questionnaire was used to assess subject details and family history of vision loss and relationship between the parents. BARDBIS program was used for pedigree analysis. P = 0.05 was chosen to show statistical significance.


  Results Top


A total of 211 participants were registered as blind since birth and were screened for further selection. Among all the participants, 120 participants (56.87%) met the final criteria and were found to be suitable for further examination. By gender-wise distribution, 75.83% were male and 24.17% female. The ages ranged from 8 to 42 years with a mean of 23. 15 years (±8.1) and 52% were <25 years, as shown in [Table 1].
Table 1: Describes the childhood blindness according to gender and age

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The visual acuities ranged from counting finger to no perception of light. Regarding the health of mothers, it was found that 89.17% of the mothers were fit during pregnancy and 10.83% showed systemic diseases, as shown in [Table 2].
Table 2: Describes the mother's health during pregnancy

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Regarding the maturity and mode of delivery, it was found that all the participants were born mature and 97% were delivered normally (90% at home and 10% at the hospital), whereas 3% were delivered by cesarean section as shown in [Figure 1].
Figure 1: (a and b) Describes the frequency of mode of delivery and place of birth

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On systemic examination, it was found that 90% of the participants were found to be healthy and 10% had some systemic problem [Table 3]. Anterior and posterior segment examination revealed the involvement of different ocular structures in various percentages, as shown in [Table 4].
Table 3: Describes the percentage distribution of the general health of participants

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Table 4: Describes the frequency distributions of various ocular anomalies

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Ocular examinations revealed that most of the participants' eyes were having more than one ocular abnormality; the cause of blindness was referred to what was thought to be the main cause. The results of the causes of blindness are presented in [Table 5].
Table 5: Describes the frequency distributions of causes of ocular anomalies

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Regarding the family history of blindness, it was found that 75% of participants had a positive family history of CB whereas 25% were with a negative history shown in [Table 6] and [Figure 2].
Table 6: Describes the family history of affected children

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Figure 2: Describes the distributions of the family history of blindness

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Regarding the nature of relationships among parents, it was found that 93.33% of the participants' parents were related to each other, and 71.66% were 1st degree and 10% 2nd degree cousins. 11.67% were having a far relationship and 6.67% of parents were not related to each other, as shown in [Figure 3].
Figure 3: Explains the nature of the parent's relationship in blind children

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About 75% of the participants' families who had a positive history of blindness their parents were related to each other, as shown in [Table 7]. However, all the participants of a negative family history of blindness, their parents were related.
Table 7: Describes the parent's relationship versus the family history of blindness

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[Figure 4]a, [Figure 4]b, [Figure 4]c shows the pedigree charts displaying the family trees, and it shows the members of the family who are affected with blindness.
Figure 4: (a-c) Explains the pedigree analysis of parents

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[Figure 5] represents the pattern of inheritance which was found to be 75% of CB was inherited (9.17% autosomal dominant, 51.66% autosomal recessive, and 14.17% X-linked) whereas 5% were sporadic cases.
Figure 5: Describes the patterns of an inheritance among the parents

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About 75% of the participant's families who had a positive history of blindness their parents were related to each other. Moreover, all the participants of negative family history of blindness, their parents were related.


  Discussion Top


Visual impairment is estimated to affect about 19 million children in the world and out of which 14 million are blind. These children are more likely to live in bad socioeconomic conditions and more likely to fall sick and hospitalized much more chances to die in childhood than any other child not facing such circumstances.[6] The most frequent causes of CB in this study were found to be a cataract, corneal abnormalities, and optic nerve disorders followed by retinal abnormalities, structural abnormalities. Similar findings were detected by Sabates et al. and Gogate et al. who reported that congenital cataract and corneal problems were the most common causes of CB.[10],[11]

In our study, it was shown that retinal and optic nerve problems contributed to more than 33% cases of CB and our findings are very close to observations noted by Patel et al. who studied the congenital blindness (CB) and severe visual impairment in Malaysia and found that the major posterior segment causes of visual loss were retinal disorders in 33% and optic nerve disorders in 7.6%.[12]

In all of the above-mentioned studies, it is clear that cataract and corneal problems are the main causes of CB. Other studies also show that congenital cataract is found in a good number of cases. A study conducted in Philippine showed that about 20% of CB is due to rubella infection.[13] Hence, it is very important to develop effective strategies for early diagnosis and better management approach. With the support of the V2020 program in China “The Chinese Childhood Cataract Program,” has resulted in an increase in childhood cataract prevalence due to earlier diagnosis of congenital/infantile cataract, in remote regions.[14]

Corneal opacities due to different reasons are one of the highest causes of CB in some areas of the world mostly in Africa and other areas of extreme deprivation in spite of educational and vaccination programs by the WHO, and the postoperative outcome has many challenges as compared to adults.[15],[16] A recent study conducted in the tribal areas of India showed that ocular morbidity due to Vitamin A deficiency was the highest.[17] These findings are very close to the results of our study, where corneal opacities are one of the most common causes of CB.

In our study, about 27% of the participants were visually impaired because of optic nerve problems. In higher income countries and more industrialized nations visual impairment due to optic nerve problems is more common but now due to rapid industrialization worldwide it is becoming more common even in low-income countries as well, and in most of the cases, the cause is malnutrition.[18],[19],[20],[21],[22]

Advanced visual disability/blindness is mostly due to inherited problems of photoreceptors leading to severe visual impairment and a study conducted in the United Kingdom showed that 24% CB was due to retinal problems because early diagnosis of inherited retinal or optic nerve disorders is often delayed due to nonspecific clinical signs, variable clinical presentations, and genetic heterogeneity of the molecular defects[23],[24],[25],[26] and in our study retinal problems were found in about 6%. Although in one small study conducted in India showed that retinal blindness was found in about 44% of children.[27]

CB was found to run in families in 75% of the participants which is greater than that found by Patel et al. who found that the affected family members were seen in 21% of the children.[12] All patterns of inheritance and the effects of consanguineous marriage were obvious. Similar results were found by Gogate et al.[11] A study conducted in Saudi Arabia showed that the incidence of consanguinity among parents of children with acquired causes was only 3% as compared to 38% of among genetically determined causes.[28] Inherited retinal blindness is a very common cause of blindness in the pediatric population, although more common in the western world. Proper diagnosis in the pediatric population is very complicated because of the difficulty in using different diagnostic modalities. Hence, based on these observations, it is advocated to use the pedigree, electroretinography, and genetic testing as major diagnostic tools for proper diagnosis.[29]

Blindness in the affected children must be detected as early as possible for a better outcome. Many of the causes are treatable or avoidable, and by providing the proper eye care services can reduce the prevalence of these conditions.

For children in higher income countries, cerebral visual impairment, and optic nerve anomalies remain the most common causes of visual impairment, while retinopathy of prematurity and cataract are now the most common avoidable causes. The pattern of CB in lower income settings is shifting from infective and nutritional corneal opacities and congenital anomalies to more complicated patterns seen in higher income settings. Improvements in maternal and neonatal health-care systems are the key to reducing the burden of avoidable blindness.

Population-based epidemiological research, focused on cerebral visual impairment and optic nerve problems, is needed to be aware of risk factors and the development of novel therapies for those disorders which are considered untreatable until now.[30]


  Conclusion Top


Blindness in the affected children must be detected as early as possible for a better outcome. Many of the causes are treatable or avoidable, and by providing the proper eye care services can reduce the prevalence of these conditions. Structured strategies should be developed for screening, referring, detection, and early diagnosis with facilities of genetic analysis should increase the level of awareness among the general public about the risks of such causes.

Inherited disorders are still very common causes of CB, so genetic counseling, early screening of children and public education may play a substantial role in the prevention of vision problems in children.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]



 

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