Population-Based Rapid Assessment of Avoidable Blindness Survey in Sohag Governorate in Egypt
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BMJ Open: first published as 10.1136/bmjopen-2019-036337 on 12 October 2020. Downloaded from PEER REVIEW HISTORY BMJ Open publishes all reviews undertaken for accepted manuscripts. Reviewers are asked to complete a checklist review form (http://bmjopen.bmj.com/site/about/resources/checklist.pdf) and are provided with free text boxes to elaborate on their assessment. These free text comments are reproduced below. ARTICLE DETAILS TITLE (PROVISIONAL) A population-based Rapid Assessment of Avoidable Blindness survey in Sohag governorate in Egypt. AUTHORS AlSawahli, Heba; McCormick, Ian; Mpyet, Caleb; Ezzelarab, Gamal; Shalaby, Mohammad VERSION 1 – REVIEW REVIEWER Hans Limburg Health Information Services, Netherlands REVIEW RETURNED 01-Jan-2020 GENERAL COMMENTS Review of Manuscript ID bmjopen-2019-036337 Prevalence and causes of blindness and visual impairment and evaluation of cataract surgical services in Sohag governorate in Egypt General comments: This report contains important information of the current eye care situation in Sohag Governorate in Egypt. The report is well written. There are several minor issues that need to be addressed. http://bmjopen.bmj.com/ Detailed comments: Page 2, Abstract, Setting: Please check the terminology used. A survey on ‘eye conditions’ is different from a survey on ‘prevalence and causes of blindness and visual impairment’, as stated in the objectives. The first requires detailed eye examination of each participants, in the on September 27, 2021 by guest. Protected copyright. second, only participants with reduced VA are examined to assess the cause. Page 2, Abstract, Participants: Q1: Why was cluster size 60 used instead of 50? Q2: Why did the investigators define a resident as a person who resided 1 year in the study site, instead of 6 months? Is ‘study site’ in this sentence the same as ‘cluster’? Page 2, Abstract, Results, line 34-35: “Prevalence was higher in women than in men in all categories of visual impairment.” Q1: Such a statement should only be made when the differences are statistically different. This cannot be seen in Table 2. Q2: Prevalence has to be more specific: sample prevalence or adjusted prevalence? Page 2, Abstract, Results, line 37: 1 BMJ Open: first published as 10.1136/bmjopen-2019-036337 on 12 October 2020. Downloaded from “Cataract surgical coverage (CSC) for VA<3/60 was 87.7%.” Q: In persons or in eyes? Page 4, Methods, line 57: “… showed the population 50 years and older was 666,697.” Table 1 shows a different number. Q: Which one is correct? Page 4, Methods, line 58: Q: Can the authors provide a reference for the expected prevalence of 4.25% of diabetic retinopathy in people aged 50+? Page 5, line 6-11: Add abbreviation for early visual impairment. Page 5, Sampling, line 39-44: “Individuals within the clusters were selected through compact segment sampling. Each cluster was divided into equal segments of 60 people aged 50 years and older with guidance of local community workers, and households in a randomly selected segment were included in the survey until 60 people aged 50 years and older were enrolled.” Q1: Assuming that in Sohag 15% of the total population is 50 years or older, then the total population in Sohag Governorate would be 666,697 / 15% = 4,444,646 people of all ages. That means that on average each of the 288 population units in the sampling frame has 4,444,646 / 288 = 15,433 people. Can the authors indicate how they subdivided the selected population unit (not cluster!) of around 15,000 people of all ages into equal segments of around 60 people aged 50+? Q2: please use the word ‘cluster’ correctly. Strictly, a cluster in this survey is a group of 60 eligible residents from the same area. Page 5, line 46-47: “Presenting VA for right and left eyes was measured in ambient http://bmjopen.bmj.com/ illumination, with 6/60, 6/18 and 6/12 tumbling E optotypes at 6m, 3m or 1m.” Q: Did the authors show optotype size 18 and size 12 at 3 and 1 metre distance? Methods, page 5-6: Q: No mention is made about the examination of patients for diabetic retinopathy, the inter-observer variation assessment on on September 27, 2021 by guest. Protected copyright. DR, qualifications of the ophthalmologists, patient selection, compliance, etc. If this is all to be included in another publication, then write this in a single sentence. Now the reader may be looking for more details on DR. Page 6, Results, line 30-34: Q: 4080-13-18-14 = 4035 instead of 4031? Page 6, Table 1: Title Q1: Which district? Or is this Sohag Governorate? Q2: Use thousands separator consistently. Page 7, line 7-10: Prevalence in females may be higher in females than in males, but the important thing to indicate is whether this difference is statistically significant. If not significant, the difference can be caused by chance only. Please indicate where the difference is statistically significant. 2 BMJ Open: first published as 10.1136/bmjopen-2019-036337 on 12 October 2020. Downloaded from Page 7, line 60 – page 8, line 3: “17.1% had refractive error, the majority of which was uncorrected (73.1%).” Q1: 17.1% of what? Page 8, Table 3, line 28-31: Q: Can the authors explain what disorders cause this high proportion of non-trachomatous corneal opacity? Corneal opacities are usually unilateral, but Table 3 shows the causes of bilateral blindness, SVI, MVI and EVI. Page 9, line 37 “The cataract surgical coverage for operable cataract causing VA <3/60 was 86.7%.” Q: Is this in persons or in eyes?” Page 11, line 42: “The prevalence of blindness, SVI and MVI were all higher in females than males…” Differences in prevalence should only be listed if significant. If not significant, these differences can be explained by chance only. REVIEWER Paul Courtright Kilimanjaro Centre for Community Ophthalmology Division of Ophthalmology University of Cape Town South Africa REVIEW RETURNED 13-Jan-2020 GENERAL COMMENTS The authors are to be congratulated for undertaking this survey— the Sohag survey will start to fill in the paucity of good quality epidemiologic data on eye diseases in Egypt. Generally, the manuscript is well-written. The abstract, in http://bmjopen.bmj.com/ particular, would benefit from review by a native English speaker. In the methods section (lines 23-26) there is a definition of refractive error. How was “reported using distance spectacles” determined? Did participants have to show the team their spectacles? The assumption that all people age 50 years and older without near vision correction have uncorrected presbyopia has been shown to be a very crude measure. A study in Tanzania demonstrated that many of these people are actually not on September 27, 2021 by guest. Protected copyright. presbyopic. The authors may want to reference that work. In the sampling section, it states that there were 288 urban and rural units for a population of about 5 million which means that each sampling unit is about 17,361 people—which is very large. Each sampling unit would then have to be divided into about 38 segments (according to your calculations). This sounds quite challenging—in most settings where RAABs are carried out, the sampling unit is quite a bit smaller than 17,000 people. Many issues can arise: how were satellite communities managed? How much influence did local leaders have in ensuring that all parts of the unit were included? How were the urban units managed? How were multi-story (with multiple families) managed? How did they manage creating a map and dividing it into around 38 units? Much more information is needed about the field work in order for the reader to interpret the findings. The authors state that within the randomly selected segments, the survey was carried out on everyone age 50 years and older until 60 people were enrolled. In some cases where compact segment sampling is used, everyone 3 BMJ Open: first published as 10.1136/bmjopen-2019-036337 on 12 October 2020. Downloaded from age 50 years and above in the sampled segment is enrolled. What was the reason for the decision to stop at 60 people and what are the implications for the findings? In the examination protocol it states that pupil dilation was done “as required”. Under what conditions would it not be required? Please tell us more about the ophthalmologists on the six survey teams. Were they from Sohag? Were they from the government hospitals? Were they from the Magrabi Foundation? Any residents? Also please provide information on when the survey was done, and how many field days were required per team. This reviewer is assuming that two teams did one cluster in one day. Please include these details. It’s unfortunate that the authors did not try to estimate the target cataract surgical rate from their data. (Lewallen S, Schmidt E, Williams T, Oye J, Etyaale D, Clark A, Mathenge W, Courtright P. Cataract Incidence in Sub-Saharan Africa: What Does Mathematical Modeling Tell Us About Geographic Variations and Surgical Needs? Ophthalmic Epidemiology 2013;20:260-266). It would be helpful for the government (both at the national and the governorate level) to know what their target cataract surgical rate should be (at different levels of visual acuity). In the results (Table 1) the district population of women in these age groups is less than the district population of men but at the national level, the opposite is true (more women age 50+ than men age 50+). Do you have an explanation for this? According to table 1 the sample of men (n=2388) of the total men was 0.00730 while the sample of women (n=1643) of the total women is 0.00547.