The Dry Eye Workshop Study (DEWS) in 2017 , defines DED as a multifactorial tear and eye surface disease characterized by the loss of tear film homeostasis and accompanied by ocular symptoms in which tear film instability and hyperosmolarity, inflammation and damage to the ocular surface and neurosensory abnormalities play etiological roles.
Worldwide, the prevalence of DED ranged from 7% to 33%  .
To the best of our knowledge, very few studies related to DED have been conducted in French-speaking sub-Saharan Africa     . Therefore, we feel it is necessary to make our contribution to the study of ocular dryness in French-speaking Sub-Saharan Africa. The objective of this first systematic review is to study the prevalence, risk factors, diagnosis and treatment of dry eye disease in French-speaking Sub-Saharan Africa.
2.1. Strategy of Research
In our study, we used the Boolean operator (OR/AND) to search for all previously selected keywords. The Boorlean operator OR permits the link between keywords of the same thematic sub-group for example: (Prevalence OR Incidence OR Proportion OR Rate OR Frequency OR Epidemiology OR Distribution). The Boorleean operator AND permits to link two keywords flat to the different thematic subgroups for example: (Prevalence OR Incidence OR Proportion OR Rate OR Frequency OR Epidemiology OR Distribution) AND (Risk Factors OR Influences) AND (Symptoms or Questionnaire) AND (Clinical Signs OR Clinical Tests) AND (Dry Eye Disease OR Xerophtalmia OR Keratoconjonctivitis sicca) AND (Pharmacological Treatment OR Non-pharmacological Treatment OR Management) AND (Benin OR Burkina Faso OR Burundi OR Cameroon OR Cap-Green OR Central African OR Congo OR Congo (Democratic Republic of) OR Ivory Coast OR Gabon OR Guinea OR Guinea-Bissau OR Equatorial Guinea OR Mali OR Madagascar OR Mauritius (island) OR Niger OR Rwanda OR Sao Tome and Principe OR Senegal OR Seychelles OR Chad OR Togo) in French and English were searched on 04 search engines: Pubmed, Chocrane database, Google scholar and ICTRP.
We adopted a sensitive search strategy by making use of at least four search engines and with adapted search terms to find publications related to DED in French-speaking Black African populations. For each of the searches performed, dry eye or one of its synonyms such as “dry eye disease” and “keratoconjunctivitis sicca (KCS)” were used. We also included the names of each of the 23 countries of French-speaking Sub-Saharan Africa in each of the search text used; for example: “prevalence of dry eye disease in Central Africa”. The citations, full text articles and abstracts were exported to the bibliographic software Zotero to sort the articles and eliminate duplicates. (See Figure 1, Figure 2)
Figure 1. Search mode: main keywords.
Figure 2. Flowchart of the current systematic review.
2.2. Inclusion and Exclusion Criteria
Studies could be included if they:
1) were published in English or French.
2) were conducted in French-speaking Black Africa.
3) involved only human subjects.
4) had at least some impact on the epidemiology of DED, in terms of etiology, risk factors, diagnosis, treatment, prevalence rates and distribution in French-speaking Black Africa.
5) had a clearly defined study design and/or type of study.
6) contained some information on the objective and subjective clinical evaluation of the DED. (Since there is no reference test for the DED, we considered studies that reported a general clinical assessment of the eye under examination and/or at least one of the following: Test of Break Up Time (TBUT), Schirmer’s test, fluorescein staining of the cornea, lissamine green staining, and/or use of subjective DED assessment tools such as the OSDI (Ocular Surface Disease Index) questionnaire.
7) Reported positive symptoms of DED in study subjects (including, but not limited to, dry eyes, pain, burning, foreign body sensation and photophobia)
Studies were excluded if they:
1) had fully qualitative results.
2) had qualities contrary to those listed in the inclusions above.
2.3. Data Extraction and Analysis
Data for each of the included studies were collected using a pre-designed survey form. Data entry and analysis was done using CDC Atlanta’s Epi info 7.0 software. Microsoft Word 2007 was used for word processing and the creation of graphs and tables with Microsoft Excel 2007.
The variables studied were:
1) the country of study,
2) Type of study,
3) the number of participants per study,
4) the average age and highest age range of study participants,
5) Frequency of dry eye in the study
6) Risk factors associated with DED,
7) the etiology or diseases underlying the DED,
8) DED diagnostic algorithms and the named treatment of the DED.
Epidemiology of DED
1) Prevalence of DED in sub-Saharan Francophone Africa
The recent study conducted in the Democratic Republic of Congo and published in July 2020  found a 90.4% prevalence of DED in glaucoma patients. The study of BONI S et al. in Côte d’Ivoire in 2018  found a prevalence of 64.16% of DED in diabetics. Of the 04 studies selected, the average prevalence of DED in French-speaking Sub-Saharan Africa is 53.54% ± 34.60%.
2) Demographic characteristics of the populations studied in French-speaking Sub-Saharan Africa
The average population size for the selected studies     was 230 ± 95.90. The average population size for the selected studies     was 230 ± 95.90. There was an average of 100 males and 130 females, with a sex ratio M/F of 0.76. The mean age of the series was 57.19 ± 5.94 years.
3) Risk factors
The risk factors found were, in descending order:
Old age = 100% of items.
Female gender = 100%.
Diabetes = 100%.
HTA = 75%.
Antiglaucoma drugs = 75%.
Extended use of computers = 25%.
Rheumatoid arthritis = 25%.
Cataract surgery = 25% and alcohol consumption = 25%.
4) Management of DED in sub-Saharan Francophone Africa
• Diagnosis of DED in sub-Saharan Francophone Africa
The questionnaires for clinical diagnosis of DED varied from one study to another, BONI S et al. in 2018  had used the international classification of DEWS 2007; Ouffoue G Y et al. in May 2019  had used a pre-established questionnaire with 7 items and finally the OSDI questionnaire was used in July 2020 by Muamba N L et al. . Eballé A.O et al. in January 2019  did not use any questionnaire for clinical diagnosis of DED.
TBUT and Schirmer I DED diagnostic tests were used in 75% and 50% of the studies respectively.
The other diagnostic tests for DED were rarely used: MGD (25%), Schirmer II test (25%), Fluorescein (25%) and Lissamine Green (25%).
• The therapeutic strategy for DED in sub-Saharan Francophone Africa
None of the 04 studies included any mention of pharmacological and/or non-pharmacological treatment of DED.
4.1. Limitations of the Study
Localization bias, notably concerning studies on DED in Subsaharan francophone African countries not yet published.
4.2. Synthesis of Results
We carried out a practical synthesis, based on a systematic review of the literature, of the epidemiology and management of DED in French-speaking Sub-Saharan Africa. Our review is based on data extracted from 04 studies conducted by eye health specialists in French-speaking Sub-Saharan Africa (Table 1). These studies are based on the prevalence and diagnostic approach of DED in French-speaking Sub-Saharan Africa.
4.3. Strengths and Limitations of the Review
For a rigorous scientific approach, we used the recommendations of the PRISMA Statement on systematic reviews. Thus, the process of carrying out this review is clear and transparent. The low number of articles included is one of the limitations of this review. All the articles included are taken from electronic databases. The strengths of our work are the exploitation of 04 search engines and the inclusion of articles published in French or in English, which limits the bias of publication or location and increases the sensitivity of this journal.
The average prevalence of our series above 50% is significantly higher than the 19.2% found by the authors in Nigeria in 2014  but lower than the 64%
Table 1. Summary of studies included in the systematic review.
observed in Palestine in 2018 . Conducting our studies only in at-risk individuals justifies our results and attests to the extent of DED that can be considered as a public health problem.
The female predominance of our review (Sex Ratio = 0.76) is in agreement with the Nigerian (Sex Ratio = 0.92)  and Pakistani (Sex Ratio = 0.89) authors . The demographic arguments support our result.
The mean age of our review was 57.19 ± 5.94 is significantly higher than the results found in Nigeria  and Pakistan , which found mean ages of 50.1 ± 19.06 years and 43.61 ± 18.57 years, respectively. DED, the prerogative of the elderly, occurs most often in states of co-morbidity.
As for risk factors, our results are in agreement with the literature on the pathogenesis of DED   . Indeed, advanced age is a risk factor for DED due to the qualitative and/or quantitative alteration of tear film synthesis. This abnormality of tear film production may be either primary or secondary to diseases frequently encountered in the elderly (diabetes, rheumatoid arthritis, etc.). The literature    has also shown the existence of a significant link between DED and the female sex, particularly after menopause, certainly due to the low levels of sex hormones playing a stimulating role in the activity of the lacrimal glands, Meibomius glands and caliciform cell density. Diabetes is thought to act by disrupting the osmolarity of the tear film secondary to chronic hyperglycemia. The toxicity of the preservatives of anti-glaucomatous eye drops (benzalkonium chloride in particular) for the ocular surface would explain the occurrence of DED in case of prolonged use.
And for the clinical diagnosis of DED, our review showed that questionnaires were used in 75% of the articles to study the natural history of the disease and the degree of discomfort caused by the main symptoms of the disease. However, the use of these questionnaires has not been uniform. Several validated questionnaires on DED exist, including: the Ocular Surface Disease Index Questionnaire (OSDI, one of the most widely used diagnostic tools in the world); the McMonnies Questionnaire; the DEQ-5 Questionnaire; the SPEED Questionnaire; and others. It is therefore important for eye health professionals practicing in French-speaking Sub-Saharan Africa to validate a diagnostic questionnaire adapted to the realities of the continent.
Efforts should also be made in the use of other diagnostic tests for DED, which have so far been under-used in Francophone Sub-Saharan Africa.
In addition, the therapeutic strategy for DED in Francophone Sub-Saharan Africa deserves the sustained attention of eye health professionals in order to comply with international standards.
In Francophone Sub-Saharan Africa, DED affects many more women and people in their quinquagenarians. Its average prevalence is estimated at more than 50%. The diagnostic approach and therapeutic strategy for DED in this part of Africa deserve to be rethought in order to comply with international standards.
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