<xref ref-type="bibr" rid="scirp.135394-"></xref>4.1. Prevalence
Of 340 school children aged 5 to 15 examined at CHU-IOTA during the period from October 30 to November 18, 111 had at least one ametropia, representing an overall prevalence of 32.65%.
Similarly, Andre et al.
[8]
and Seydou at IOTA
[1]
found a respective prevalence of 43.1% and 46.8%.
Our frequency was much higher than that of Rakotoarisoa et al.
[9]
, Auzemery et al.
[10]
, Sounouvou et al.
[11]
, and Nepal et al.
[12]
who found respectively 13.5%, 2% - 10%, 10.6% and 8.1%.
On the other hand, prevalences higher than ours were reported by: Ezinne et al.
[13]
in Nigeria (86.6%), Domngang Noche et al.
[14]
in Cameroon (86.3%), He et al.
[15]
in Guangzhou in China (50.8%), Ayed et al.
[16]
in Tunisia (57.2%) and by Maul et al.
[17]
in Chile (56.3%).
This difference between our results and those of others can be explained by the difference in methodology on the one hand and by the variability depending on the type of study (hospital, school and population).
4.2. Sociodemographic Characteristics
Age:
The average age was 11.42 ± 2.75 years and the most common was the age of 15 years or 18.02% followed by 12 years with a frequency of 17.12%.
Leon
[18]
and Domngang Noche et al.
[14]
carried out their survey on the same age group as ours (5 to 15 years).
Andre et al.
[8]
studied the age group of 6 to 15 years.
The survey carried out by Barroso Schimiti et al.
[19]
focused on the age group of 6 to 12 years.
Ayed et al.
[16]
in Tunisia did a study on the age group from 6 to 20 years in 2000.
It is in this age group that refractive errors must be detected to avoid their repercussions on children’s studies as much as possible.
According to the literature review, it should be noted that it is at the age of 6, more or less 3, that the child begins schooling, so he acquires many new things. This will affect his brain as well as the organ of sight. At the age of 15, the child’s emmetropization process ends and, moreover, at this age, students have intense school activity
[20]
.
Sex:
We received 70 girls (63.06%) and 41 boys (36.94%) for a sex ratio of 0.59.
Our values are comparable to those found by Andre et al.
[8]
who found 60.7% of female ametropes compared to 39.3% of males.
On the other hand, Raharinantenaina
[20]
found 51.77% male versus 48.21% female and stipulated that there was no link between ametropia and sex.
4.3. Clinical Characteristics
The average visual acuity was 4/10 (range 1/10 and 10/10).
Intraocular pressure was normal in all patients.
These values are comparable to those of Seydou
[1]
whose average visual acuity was 5/10 (extreme of 1/10 and 10/10) as well as normal intraocular pressure in all patients.
The refractive errors found were:
Astigmatism 73.87%, hyperopia 23.87% of cases and myopia 2.25%.
In the present study, BAV was the most recurrent complaint in ametropes, i.e. 76.58%, followed by eye pain and visual fatigue, i.e. 64.86% and 59.46% respectively.
Frequencies lower than ours were reported by Seydou
[1]
and Paluku et al.
[5]
, respectively 42.2% and 42.1% reduction in visual acuity and headaches represented 25% for the latter.
On the other hand, Diallo et al.
[7]
found 54.1% of patients without complaints compared to 7.1% of the drop in visual acuity and 1.9% of pruritus and affirms that the latter could be linked to the season of allergic conjunctivitis which was noticed during their studies.
These results show that reduced visual acuity is one of the main complaints that lead most patients to come for consultation.
Associated pathologies were found in 137 ametropic eyes or 61.7%.
Allergic conjunctivitis was the most common ocular pathology in hyperopia and astigmatism, respectively 9.01% and 26.13% followed by pathological papillary excavation in 7.2% and 6.31% respectively, on the other hand, the vitreous disorder was the most represented pathology of myopes among the 61.7%.
This result is close to that of Diallo et al.
[7]
who found 68.3% of associated pathology and affirmed that LCET was associated with different types of ametropia with 74.25% in myopes; 68.75% in hyperopia; 71.74% in astigmatism.
These results could be explained by the conjunctivitis season, which was prevalent during our studies.
Refraction:
Refractive errors were represented by astigmatism 73.87%, hyperopia 23.87% of cases and myopia 2.25%.
Astigmatism:
In our study, astigmatism was the most common ametropia with 73.87% (n = 164).
This prevalence is roughly similar to that of NWOSU. Nwosu et al.
[21]
who found 75.5% astigmatism in their series.
Other authors have reported prevalences lower than ours: Garcia et al.
[22]
, and Kawuma et al.
[23]
who found 34% and 52% respectively.
On the other hand, a study carried out in Benin by Sounouvou et al.
[11]
found that 91.9% of ametropes were astigmatic.
We did not find a statistically significant difference between age, gender and astigmatism. 60.37% of astigmatics were female with a sex ratio of 0.66, among whom 20.12% were aged 15 years.
In the present study, 78.66% of astigmatisms were direct; 10.37% reverse and 10.98% oblique.
On the other hand, in the investigation carried out by Diallo et al.
[7]
astigmatism represented 46.5% among which 92.4% were direct astigmatisms; 4.6% were inverse and 3% were oblique.
Among our cases of astigmatism, 43.90% were compound hyperopic.
This high prevalence of astigmatism, especially among those aged 15, could be explained by the end of emmetropization at this age.
Hyperopia:
In our study, hyperopia was found in 23.87% (n = 53) of ametropes.
This frequency is similar to that of Andre et al.
[8]
who found 23.7%.
In Benin, Sounouvou et al.
[11]
found that 19.7% of ametropes were hyperopic.
In a study carried out in Iran, Hashemi et al.
[24]
reported 21.70% hyperopia.
Frequencies higher than ours were found by: Faderin et al.
[25]
which was 52.2%.
Low hyperopia represented 96.23% of hyperopia in our study.
Myopia:
Myopia was mild in 60% and severe in 40% of cases.
In our study, we found a prevalence of 2.25% (n = 5) for all female myopia, i.e. 100%. Ages 6 and 10 each represented 40% of myopes.
This prevalence of myopia is similar to that reported by Leon
[18]
which was 2.5%.
Proportions higher than ours were reported by Faderin et al.
[25]
and Diallo et al.
[7]
who found 9% and 38.7% of myopia, respectively.
Low myopia represented 60% of all myopes.
This diversity in prevalence between our results and the literature data can be explained on the one hand by environmental factors, which are accentuated in urban areas and attenuated in rural areas. On the other hand, the genetic factor is recognized in both small and high myopias. This heredity can be dominant or recessive in both cases. The relationship between age, gender and myopia is poorly understood
[20]
.
One of the physiopathological hypotheses for the significant increase in myopia in industrialized countries is based on the excessive use of computer display screens
[20]
.