Prevalence and causes of blindness and visual impairment among children in Morocco

¹Laboratory of Pharmacology, Neurobiology, Anthropobiology and Environment, Faculty of Sciences Semlalia, Cadi Ayyad University, Marrakesh, Morocco, ²Higher Institute of Nursing and Technical Health Occupations, Ministry of Health and Social Protection, Rabat, Morocco

^&Corresponding author
Soukaina Loulidi, Laboratory of Pharmacology, Neurobiology, Anthropobiology and Environment, Faculty of Sciences Semlalia, Cadi Ayyad University, Marrakesh, Morocco

Introduction    

Blindness and visual impairment are burdensome problems that need to be properly managed to avoid medical, social, and economic damage [1]. The onset of this problem has serious repercussions on the quality of daily life, which can last for the rest of a person's life [1]. In children, the situation is even worse. Since visual impairment can occur at a time when the child needs vision to guarantee the proper organization of psychomotor development, it can result in cognitive and language delays, which will become more apparent at school age and may lead to academic failure [1]. This impairment has a major impact on the child's life, the child's family, and the community economy. Globally, visual defects and childhood blindness are major public health issues and have been the focus of several initiatives by the relevant authorities. As part of a partnership founded in 1999 between the World Health Organization (WHO) and the International Agency for the Prevention of Blindness (IAPB), a 2006-2011 action plan was launched with the aim of eliminating avoidable blindness and visual impairment between 1999 and 2020 [2]. This vision - 20220 "the right to sight" - is to set up care services to guarantee adequate, quality care [2]. Achieving this goal will reduce the number of visually deficient and blind persons from 96 to 25 million by 2020 [2]. In 2020, the causes of this eye problem have not been eliminated, and challenges remain, including population size, access to ophthalmic services, and professional competence [3].

Two-point-two (2.2) billion people worldwide are visually impaired, and 12% of them suffer from legal blindness [1]. Again, according to the same WHO statistics, this anomaly could have been prevented in almost half of the affected population. Low- and middle-income countries have a prevalence of visual impairment four times higher than high-income countries [1]. The WHO has established five categories of visual impairment affecting distance vision in the Eleventh International Classification of Diseases (2018) [1]: i) mild visual deficiency - visual acuity: between 6/12 and 6/18; ii) moderate visual deficiency - visual acuity: between 6/18 and 6/60; iii) severe visual deficiency - visual acuity: between 6/60 and 3/60; iv) blindness: visual acuity: less than 3/60.

The main causes of visual deficiency among children worldwide vary depending on the characteristics of each region. These characteristics include socio-economic development and the performance of health care structures, as well as the quality of care provided. Low-income countries are marked by a rising rate of congenital cataract, while retinopathy of prematurity is the leading cause in middle-income countries. According to the WHO in 2017, the first anatomical area most affected is the retina (retinopathy of prematurity, macular retinal dystrophy and retinitis pigmentosa), and in second place, we have damage to the globe (anophthalmia and microphthalmia); then there are anomalies related to the lens (cataract) and cornea [4]. In Morocco, studies on visual impairment and childhood blindness are rare, which means that very little is known about the current situation in relation to this problem due to a lack of recent data. The objective of our study is to assess, for the first time, the prevalence of blindness and visual deficiency in children and to analyze the epidemiological situation related to this ophthalmic anomaly among children in central Morocco.

Methods     

Study design: this is a prospective study aimed at describing and analyzing the epidemiological situation regarding childhood blindness and visual impairment in central Morocco. An exhaustive sampling method was adopted in order to reach the total number of consulting children during one year.

Study setting: according to the regional breakdown, the Marrakesh-Safi region (Figure 1), which represents our study area, covers an area of 41,404 km², equivalent to 6% of the national territory. The region comprises one prefecture and seven provinces: Prefecture of Marrakesh and the provinces of El Haouz, El Kelaa des Sraghna, Essaouira, Chichaoua, Youssoufia, Rhamna, and Safi. The population counts 4774413 in 2020 [5]. The hospital environment and the school for the blind were the two settings concerned by this issue and consequently, where our study was conducted. Thus, data were collected from i) the ophthalmology department of the Errazi Hospital at the Mohammed VI University Hospital Center of Marrakesh (paediatric ophthalmology consultation department at the diagnostic center), and ii) from the Abou El Abbas Sebti institute run by the Alaouite organization for the protection of the blind in Marrakesh, which provides specific educational services. It should be noted that the Mohammed VI University Hospital Center receives all cases of children referred by provincial hospitals in the region who require in-depth diagnosis and treatment of ophthalmological pathologies. The data collection was carried out from 1^st November 2021 to 31^st October 2022.

Participants: we recruited all children aged between 4 and 15, with a visual acuity measurement of less than 6/12 in the better eye, from the Marrakesh-Safi region. All children outside the age range studied, those with no visual acuity measurement or visual acuity greater than 6/12, those outside the prefecture/province of the Marrakesh-Safi region, and those who were absent at the time of data collection were excluded from this study.

Study size: we included all children with blindness or visual impairment with a visual acuity of less than 6/12 for one year. In total, we identified 144 children with these inclusion criteria from among 720 consulting children during November 2021-October 2022.

Variables: we collected demographic variables (age, gender, residence area, locality of residence) and clinical data (visual assessment of the eyes, site of abnormality leading to visual loss, disease type, aetiology of visual loss). Age was grouped as follows: 4-7 years, 8-11 years, and 12-15 years; visual assessment of the eyes was categorized as (fewer than 6/12-6/18, fewer than 6/18-6/660, fewer than 6/60-3/660, fewer than 3/60-PL, no luminous perception). Site of abnormality leading to visual loss was classified as follows (lens, normal globe, whole globe, retina, cornea, uvea, other) and aetiology of visual loss was grouped into (hereditary factor, intrauterine factor, perinatal/neonatal factor, postnatal/childhood factor and unknown aetiology). All clinical variables were classified according to WHO-recommended classifications [6].

Data sources/measurement: epidemiological data were collected using a questionnaire (WHO/PBL Eye examination record for children with blindness and low vision) developed in 1988 and submitted to the WHO standard protocol in collaboration with the International Eye Health Centre [6]. The data were collected by interviewing children's parents and ophthalmologists, and by consulting the children's records. The visual acuity was tested by ophthalmologists using the Snellen E scale.

Bias: we worked with a standardized WHO questionnaire and were accompanied by the treating ophthalmologist during clinical data collection. The investigator was a person who mastered the scientific medical jargon and the data collection tool. All these strengths were a benefit for us in reducing bias in this study.

Statistical methods: the visual acuity variable is divided into five WHO categories: visual acuity between 6/12 and 6/18, between 6/18 and 6/60, between 6/60 and 3/60, visual acuity less than 3/60-luminous perception, and no luminous perception. The first three categories represent visual impairment, and the last two represent legal blindness. Variables for the causes of visual impairment and blindness were classified by analyzing the type of disease and the anatomical site responsible for the abnormality leading to vision loss. Quantitative variables were analyzed by calculating frequencies and means. Results were summarized and expressed in percentages and effective numbers using tables and graphs. Epidemiological parameters such as prevalence [(total number with disease)/(population at risk for the disease) during a time period] [7] and sex ratio (number of males/number of females) [7] were calculated. In addition, the data were analyzed using SPSS 16.0 software.

Ethical consideration: this study was complies the tenets set in the Declaration of Helsinki and ethics approval. Administrative approval was obtained from the directors of each investigation site (Mohammed VI University Hospital Center - N°: 7838, Abou El Abbas Sebti Institute - N°: 9364). The survey was conducted in complete confidentiality and anonymity, after obtaining written consent from all parents of participating children.

Results     

Participants: over the one-year period of data collection, among 720 children who consulted for various ophthalmological pathologies, we detected 144 children with visual deficiency or legal blindness.

Descriptive data: this result shows a one-year prevalence rate of 0.2 (95% CI). A detailed epidemiological investigation was conducted for the 144 children in our study sample. 51.39% is the rate for females, compared with 48.61% for males, with a sex ratio of 0.95 (Table 1). The 8-11 age group (56.2%) is the most dominant, followed by 12-15 years (26.4%), with the remainder (17.4%) between 4 and 7 years (Table 1). Looking at the findings of our research, more than half of all children diagnosed as blind or visually impaired live in urban areas (65.3%). Most of these children reside in Marrakesh (59.7%), followed by El Haouz (13.9%), while only a minority of this population reside in Essaouira and Rhamna provinces (1.4% each) (Table 1). The onset of childhood blindness and visual defects is frequent at birth for 60.4% of the study population, while we have only 0.7% in the 12-15 age group. The age group between four and seven also had a high rate (22.2%) (Table 1).

The findings of our research reveal that the proportion of visually impaired children (77.1%) is higher than that of blind children (22.9%). Children with an acuity of less than 6/12-6/18 were in the majority (45.8%), followed by those with an acuity of less than 6/18-6/60 (30.6%) and 20.1% with no perception of light at all (Table 2). The anatomical site most affected was the lens with a rate of 34%, followed by the normal globe (29.2%) and the whole globe (23.6%). The Uvea was the anatomical site least affected in our population (0.7%). The most frequent pathology was cataract (34%), refractive error (26.4%) and glaucoma (23.6%), compared with uveitis and keratoconus (0.7% and 1.4%, respectively) (Table 3). Depending on the WHO classification of vision deficiency, the main aetiologies of visual defect and blindness were respectively classed as hereditary factor (63.2%), unknown aetiology (26.4%), postnatal/childhood factor (6.4%), intrauterine factor (2.8%) and perinatal/neonatal factor (0.7%) (Figure 2).

Discussion     

In the interest of developing appropriate strategies for combating visual impairment and blindness within children, it is essential to conduct a meticulous study of the epidemiological situation in the region under study. The present research will contribute positively to the construction of a global vision about health statistics on childhood blindness and visual impairment, especially as statistics of this health problem are scarce in Morocco. During one year of the study, we detected 144 visually impaired or blind children, among 720 children consulting for different ophthalmic problems. Given that statistics on childhood visual defects and blindness are not available for the region of Marrakesh-Safi, for the first time we opted to analyse the epidemiological situation by calculating prevalence over one year. For the present study, the one-year prevalence was 0.2%.

The rates for both sexes are relatively equal (girls 51.39%, boys 48.61%). The same results were found in the Republic of Suriname (girls 50.50%, boys 49.50%) [8], Brazil (girls 51%, boys 49%) [9], Kenya (girls 50.60%, boys 49.40%) [10]. Burkina Faso [11], Ethiopia [12], Bangladesh [13], Mongolia [14], Czech Republic [15], Turkey [16], Pakistan [17], South India [18], and Philippine [19], on the other hand, reported a male/female dominance rate of between 61.4% and 70%. What's more, six of these countries are Asian. In other countries, however, such as Mali 64.5% [20], Togo 58.2% [21], Iran 59% [22], and Mexico 58% [23], the female sex dominates.

The children in our study are all under 15 and over 4 years of age, in order to avoid finding a child under 4 years of age with a visual acuity measurement, due to the difficulties encountered in doing this in young children. The most common age group is between 8 and 11 (56.2%). Therefore, this is the age of schooling when the child may encounter learning difficulties that can help teachers and parents orient themselves towards the exact problem that is pathological and ophthalmic in nature, and then begin the process of diagnosis and treatment. According to our study, cases in urban zones (65.3%) are higher than those in rural zones (34.7%), which can be justified by the accessibility of care, particularly advanced surgical care, which is only available in the ophthalmology departments of university hospitals. This is even clearer if we refer to the statistics for children who are visually impaired by city for the Marrakesh-Safi region, of which Marrakesh predominates with a rate of 59.7%.

The occurrence of childhood blindness and visual deficiency from birth (60.4%) is more widespread than in other age groups. These findings are similar to those of a study conducted in the United Kingdom, where the incidence of this visual problem is highest in the first year of life [24]. Moreover, ten times higher than in the 1 to 4 age group, as reported in another study in the same country [25]. In addition, 52.3% of Nepalese children are visually impaired or blind from birth [26].

The rate of visual impairment (77.1%) among children in the Marrakesh-Safi region is higher than blindness (22.9%), with a large margin of difference. The above findings are similar to those of studies carried out in other countries. For example, Guatemala (94%) [27], Brazil (89.4%) [28], Cameroon (60.5%) [29] and Tunisia (52.3%) [30] also have a significantly higher rate of visual deficits than blindness. By contrast, nations such as Ghana (99%) [31], Myanmar (95.7%) [32], North India (89.3%) [33], Mali (78.1%) [26] and the Czech Republic (69.5%) [15] have a high rate of blindness compared with visual impairment. This is due to the choice of data collection setting, which is the school for the blind for all these studies, and in which the rate of blindness is higher. The intervals (less than 6/12-6/18), (less than 6/18-6/60), (no light perception) are the most dominant, with rates of 45.8%, 30.6%, and 20.1%, respectively.

The most dominant range for low vision was less than 6/12 - 6/18 visual acuity, and the most dominant for blindness was for children suffering from a lack of light perception (10.1%) (total blindness). As in the case of Brazil, moderate visual defects (visual acuity less than 6/12 - 6/18) were dominant (35.5%), but blindness represents only 1.6% [28]. Pakistan also has relatively similar results, with moderate visual impairment dominating (43%) and legal blindness at a high rate (33%) [17]. Low vision was therefore represented by a majority rate (77.1%) in our study. Blindness, on the other hand, accounts for only 22.9%. Similarly, in Cameroon, the percentage of low vision (60.5%) was higher than blindness (39.5%) [29]. Mexico City (Guatemala) also had a high rate of visually impaired people (94%) compared with blind people (6%) [27]. The case was different in other countries, as in Malaysia 92.7% of children were blind or severely visually impaired [34], 95.7% were blind in Myanmar [32], and 61% were blind in Mexico (Guadalajara) [23]. The causes of visual impairment, whether blindness or low vision, differ from nation to nation, depending on socio-economic characteristics, lifestyle, as well as the quality of the health care system. The causes of this anomaly are numerous, and several anatomical sites may be affected.

The anatomical site most affected in the children in our study was the crystalline lens (34%), followed by the normal globe (29.2%) and the whole globe (23.6%). The lens was also the most affected in Indonesia, with a rate of 31% [35], Mongolia (34%) [14], Cambodia (27.4%) [36], and Malaysia (22.3%) [34]. Contrary to what has already been mentioned, the whole globe was the anatomical site most affected in North India (27.4%) [33] and Ghana (26%) [31]. Thus, retinal diseases were found to be the cause of blindness and visual deficiency in Iran in two studies (44.3%) [22] and (51.3%) [37], in South Africa (42%) [38], and in the Philippines (69.8%) [19].

According to the WHO, the main cause in nations with middle incomes is retinopathy of prematurity, while cataract is the most prevalent pathology in populations of low-income countries [1,2]. Our case was different; the outcome of our investigation revealed that cataract (34%) is the common cause in the Marrakesh-Safi area, given that Morocco is a middle-income country under the new World Bank categorization for 2023 [39], and only one case (0.7%) was detected with ROP. In the same vein, the WHO has also shown that refractive error, which ranks second in our study with a rate of 26.4%, is a frequent cause in all countries [2]. Likewise, China (Beijing) (75%) [40], Iran (81.8%) [41] and Brazil (76.8) [42] detected a dominance of refractive error in blind or partially-sighted children.

Children in the Marrakesh-Safi region had the hereditary factor (63.2%) as the culminating factor compared to other aetiologies causing visual deficiency and blindness. Overall, the hereditary factor is the most widespread worldwide, according to WHO 2007 [2]. Mongolia [14], UK [25], Cambodia [34], Tunisia [30], Iran [22], Turkey [16] and Fiji [43]. In most other countries, however, the aetiology is undetermined. All the results obtained through this study are considered very useful to create updated databases about childhood visual deficiency. It was essential to have a global overview of the epidemiological situation of visual defects in children in central Morocco, and to detect cataract as the main pathology and hereditary risk factor that has been known to dominate in this area.

Limitations: the private sector was not involved in this study. Given that the public sector dominates the study area, the absence of this data should not affect our results too much.

Conclusion     

Our study has brought to light important data on the epidemiological situation of this visual disorder in children in the Marrakesh-Safi region, and the picture of this situation has become clear. Admittedly, the prevalence of this anomaly is still low, as in countries all over the world, but the psychological, cognitive, pathological, economic, and developmental repercussions on children's daily lives make this situation very disturbing and difficult to manage. This study underlined the benefits of early diagnosis of these eye abnormalities, particularly by parents and teachers in schools.

Competing interests     

The authors declare no competing interests.

Authors' contributions     

Soukaina Loulidi performed the review, analysed, interpreted the data and wrote the manuscript. Samia Boussaa conceived, designed the research, analysed, interpreted the data and revised the manuscript. Mohamed Loukid revised the manuscript. All the authors have read and approved the final version of this manuscript.

Acknowledgments     

We thank all the children, their families, and the health staff at the Mohammed VI University Hospital Center and the School for the Blind Abou El Abbas Sebti in Marrakesh for their kind assistance.

Tables and figures     

Table 1: demographic data of the children participating in the study (N=144)

Table 2: visual assessment of the eyes in children (N=144)

Table 3: anatomical sites and disease type of visual loss of the study population (N=144)

Figure 1: presentation of Marrakesh-Safi region

Figure 2: aetiology of visual loss according to World Health Organization classification

References