Population-Based Rapid Assessment of Avoidable Blindness Survey in Sohag Governorate in Egypt

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:

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“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.

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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

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. What was the reason? On table 2, please label the column “projected number of people aged 50 years and older by visual status” rather than just “n”.

Table 3 lists one person blind from onchocerciasis. Oncho is not endemic in Egypt. Please explain. How was glaucoma diagnosed? http://bmjopen.bmj.com/ Was the examination sufficient to reach this diagnosis? Should it be included under posterior segment diseases?

On table 4 the age and sex adjusted prevalence of bilateral cataract blindness is 1.5%. What is included in this definition? If one eye is blind due to cataract but the other due to posterior segment disease, would that person be included as “cataract blind”? If one eye has unoperated cataract and the other eye has on September 27, 2021 by guest. Protected copyright. had cataract surgery but complications mean that the eye is still blind, is the person included? If 1.5% are bilaterally blind due to cataract and 5.9% are bilaterally blind then 25% of bilateral blindness is due to cataract. It is important to know the assumptions that go into the definition of bilateral cataract blindness. Again, please relabel the column currently labelled “n”.

The difference between the cataract surgical coverage and the effective cataract surgical coverage are significant, particularly for women. In males, the difference between the CSC and eCSC (for blindness) is 84.2-50.8 = 33.4 while for females it is 89.2-38.8 = 50.4. This is quite important. Some of this information is in the data set and needs to be presented. The authors note that government hospitals have worse outcomes compared to private facilities. Please present the findings by sex: were women more likely to use the government hospitals? Were women more likely to have poor outcomes? What is meant by “voluntary” sites? Overall, 66% of surgeries were done in private facilitates. Was there a

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difference in outcome (men to women) among those attending the private facilities? More detail is needed to interpret the findings.

If the authors wish to report findings on barriers (which many researchers would not propose as part of the RAAB investigation) then they should also present information on the actual cost of cataract surgery at the private and the government facilities.

In the first line of the discussion the authors state that women were under-sampled. Please explain. The choice of the word “under-sampled” suggest that women were not included in the sample on purpose.

In the second para of the discussion the authors state that, compared to the Menofiya survey findings, the prevalence of blindness has decreased. This is not an accurate statement. The 95% confidence intervals assuredly overlap. Please change the wording.

Later in the discussion the authors stated that the CSC was slightly higher in women than men. A more accurate statement would be that the CSC were similar. That said, there may be much more that needs to be addressed, as noted earlier. The authors state that the government facilities offer ECCE. Is this true at all government facilities? Do all private facilities do phaco? Is small incision practiced? Are IOLs implanted on all ECCE cases? While the reader appreciates that the authors were attempting to survey vision loss in Sohag much more information regarding the current eye care services should be provided (ideally in the introduction) to help the reader interpret the findings.

REVIEWER Anna Rius Universitat Politècnica de Catalunya Spain http://bmjopen.bmj.com/ REVIEW RETURNED 13-Jan-2020

GENERAL COMMENTS Sex desaggregated data

Abstract: the results should be stratified by sex, as you refer to gender differences in the conclusions

Introduction: on September 27, 2021 by guest. Protected copyright.

You should clearly identify the link within the information you provide and the results you are seeking as some of the information I think is not crucial. For example, if you provide the number of hospitals providing eye care, you should explain why this numbers are low or high and how it would influence the prevalence (cost, distance, distribution) if you are going to use it in the discussion.

Objective: If there are gender differences in Egypt, why you do not reflect those in the objectives of the study?

Methods

It would be important to explain if the software apply any correction to better interfere the prevalence regarding the

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population stratification by sex or age group or you just show the crude results.

Clarify the following sentences “The prevalence of diabetic retinopathy was used instead of blindness as it was expected to be the lower of the two values”

“We did not directly include patients in the design of the research, however, policy makers in the Ministry of Health and Population (MOHP) and local community leaders were consulted about the survey design, questions and approaches to facilitate the implementation of the study.”

Results

Table 1. Clarify what District means. It would be interesting to conduct a distribution comparison between sample and population in order to see if it is representative. Show the distribution among sex, as it seems you have a vias there.

Table 3. It would be useful to show the results in a decreasing order, try to aggregate the data if possible and not to show the diseases with no significant number of cases. It would be important to disaggregate the results by sex as there are clear difference among prevalence.

Early VI? Why you disaggregate to that many categories? Does it provide interesting information in order to produce policies or actions? If not, I would aggregate it.

Table 4. It would be useful to show the total visually impaired by http://bmjopen.bmj.com/ sex. As female are older than males it age has a high correlation with age, any comparison should be adjusted.

Table 5. I don’t think that stratifying the VA outcome is important in the results.

on September 27, 2021 by guest. Protected copyright.

VERSION 1 – AUTHOR RESPONSE Reviewer 1

General comments:

This report contains important information of the current eye care situation in Sohag Governorate in Egypt. The report is well written.

Thank you for your positive feedback and time taken in reviewing this paper.

There are several minor issues that need to be addressed.

Page 2, Abstract, Participants: Q1: Why was cluster size 60 used instead of 50?

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Guided by the RAAB manual where pilot studies showed that it was not feasible for the survey teams to conduct the diabetic retinopathy assessment in addition to the RAAB survey for a cluster of 50 persons. We went for the option of having a cluster of 60 persons assigned to two teams working together to complete one cluster in one day. Accordingly, we used the modified sample calculator in the RAAB program upon selecting the RAAB+DR option.

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’?

One year was reported in error, this has been updated to six months as per the study protocol. Yes, “study site” refers to the cluster.

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?

Text updated: it should read 627,510 in 2016.

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+?

Edited accordingly to include reference.

Page 5, Sampling, line 39-44:

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+? http://bmjopen.bmj.com/

Google Maps map of the area. Local community leaders contributed to ensure all segments on September 27, 2021 by guest. Protected copyright. represented inhabited areas only and one segment was randomly selected for the survey. There was little variation in the arrangement of households between areas defined as urban or rural and most housing was single story. Households in a randomly selected segment were included in the survey until 60 people aged 50 years and older were enrolled.

Q2: please use the word ‘cluster’ correctly. Strictly, a cluster in this survey is a group of 60 eligible residents from the same area.

Edited accordingly.

Page 5, line 46-47: “Q: Did the authors show optotype size 18 and size 12 at 3 and 1 metre distance?

No. Edited accordingly. Presenting VA for right and left eyes was measured in ambient illumination, with 6/60, E optotypes at 6m, 3m or 1m, and 6/18 and 6/12 E optotypes at 6m”

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Methods, page 5-6: Q: No mention is made about the examination of patients for diabetic retinopathy, the inter-observer variation assessment on 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.

Added a sentence: Details of the diabetic retinopathy examination protocol undertaken will be reported in detail elsewhere.

Page 6, Results, line 30-34: Q: 4080-13-18-14 = 4035 instead of 4031?

There were 4078 people enrolled, not 4080 (which was the sample size calculated). Please see our explanation of some changes included as a result of reviewing the RAAB6 data entry, cleaning and report generation process.

Page 6, Table 1: Title Q1: Which district? Or is this Sohag Governorate?

Updated district to governorate in line with table title.

Q2: Use thousands separator consistently.

Edited accordingly.

chance only. Please indicate where the difference is statistically significant. http://bmjopen.bmj.com/

Updated text: The prevalence of blindness, SVI and MVI were all higher in females. There was only weak evidence of a statistically significant difference between females than males for blindness (p=0.046), but strong evidence for the differences between females and males for SVI and MVI (p<0.001 for both).

P values from a two-sample test of proportions using the adjusted prevalence estimates for male and female sub-groups have been included in Table 2. on September 27, 2021 by guest. Protected copyright.

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?

Text updated: 17.1% of the sample had refractive error

The standardised RAAB cause ‘non-trachomatous corneal opacity’ isn’t broken down into further causes, therefore we are unable to report any more detail. We have searched the limited available literature about visual impairment in Egypt and, although we found a paper discussing the high prevalence of keratoconus in a specific clinical sample in this governorate (Saro AS, Radwan GA,

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Mohammed UA, Abozaid MA. Screening for keratoconus in a refractive surgery population of Upper Egypt. Delta J Ophthalmol 2018;19:19-23), we cannot speculate on a likely explanation.

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?”

Updated to include ‘in persons’.

Text updated: The higher prevalence of SVI and MVI among females compared to males was found to be statistically significant. There was only borderline statistical significance for the difference between the higher female blindness estimate compared to the male blindness estimate.

Reviewer 2

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.

Thank you for this acknowledgement and detailed review.

Generally, the manuscript is well-written. The abstract, in particular, would benefit from review by a native English speaker. http://bmjopen.bmj.com/ The abstract has been reviewed and amended.

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?

Participants who used distance glasses were either wearing them or showed them to the survey teams. The use of near vision glasses was self-reported through the question in the survey, however

participants were not obliged to show them to the teams. We have updated the manuscript so that the on September 27, 2021 by guest. Protected copyright. reader can understand that the presbyopia maybe over/ underestimated.

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 presbyopic. The authors may want to reference that work.

We acknowledge that the RAAB methodology makes an assumption in this regard. The paper from Tanzania finds that people with mild uncorrected myopia usually do not complain from near vision. Accordingly, RAAB may overestimate presbyopia. However, in our study, we did not test near vision, we asked about the ownership of a near vision glasses. It is now mentioned in the limitations of the study.

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

BMJ Open: first published as 10.1136/bmjopen-2019-036337 on 12 October 2020. Downloaded from 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.

Text updated: The sampling frame consisted of 288 urban and rural population units, corresponding to 12 Marakez (districts), based on 2016 census enumeration areas. From this, 68 clusters were selected with probability proportionate to population size. Cluster selection was carried out using the RAAB6 software. Individuals within a population unit were selected through compact segment sampling. Each population unit was divided into equal segments estimated to contain at least 60 people 50 years and older. For large population units, this was done with a grid square overlaid on a Google Maps map of the area. Local community leaders contributed to ensure all segments represented inhabited areas only and one segment was randomly selected for the survey. There was little variation in the arrangement of households between areas defined as urban or rural and most housing was single story. Households in a randomly selected segment were included in the survey until 60 people aged 50 years and older were enrolled.

In some cases where compact segment sampling is used, everyone aged 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?

We stopped enrolling participants at 60 as per the standardised RAAB survey sampling methodology. Taking a fixed number of participants at the second stage of this probability proportionate to size cluster random sampling approach ensures the sample is self-weighting. For a rapid survey methodology is it important to be able to plan fieldwork efficiently, i.e., according to the set number of people it has been determined can be examined by a team in one day. Randomly selecting a http://bmjopen.bmj.com/ segment per cluster should limit any potential selection bias within clusters compared with other approaches such as random walk.

During the field work, survey teams did occasionally examine more people than 60 people to satisfy the needs of families and neighbours who were not enrolled but asked for help. Survey teams responded positively with extra resources, after clarifying why they did not record their data. on September 27, 2021 by guest. Protected copyright. In the examination protocol it states that pupil dilation was done “as required”. Under what conditions would it not be required?

Text updated: Dilated fundus examination, using two drops of tropicamide 0.5%, was carried out in line with the RAAB diabetic retinopathy module protocol, or where the cause of visual impairment was not uncorrected refractive error, or an obvious corneal or lens opacity. Details of the diabetic retinopathy examination protocol undertaken will be reported in detail elsewhere.

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?

Text updated: The six ophthalmologists were Masters degree qualified government employees from Cairo (four), Hurghada and Sohag (one each); all were part of the Magrabi Foundation outreach team.

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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.

Text updated: Field work was completed over 23 days in February 2019. Two teams attended one cluster per day, examining 30 participants each.

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).

We appreciate this suggestion and direction towards a very useful resource. We will explore the possibility of completing this exercise now the survey is completed.

Table 1 does not reference national level data as this was a district level survey. It compares the survey sample to the governorate. The sample was 59.2% male while the population in the governorate was 52.1% male. Females were under-represented, as acknowledged in the discussion, but the reason for this is unclear.

On table 2, please label the column “projected number of people aged 50 years and older by visual status” rather than just “n”. http://bmjopen.bmj.com/ Table has been updated.

Table 3 lists one person blind from onchocerciasis. Oncho is not endemic in Egypt. Please explain.

The patient was an eligible resident of the survey area, however, he gave a history working in Sudan 8 years ago, and got the disease at that time. Sentence added to text to explain this finding.

How was glaucoma diagnosed? Was the examination sufficient to reach this diagnosis? Should it be on September 27, 2021 by guest. Protected copyright. included under posterior segment diseases?

Text updated: Glaucoma was diagnosed based on only obvious pathological signs (digital palpation, an afferent pupil defect, corneal oedema, a vertical cup-disc ratio of 0.8 or greater) in the absence of intraocular pressure or visual field examination, or where an existing diagnosis of glaucoma was known.

On table 4 the age and sex adjusted prevalence of bilateral cataract blindness is 1.5%. What is included in this definition? If one eye is blind due to cataract but the other due to posterior segment disease, would that person be included as “cataract blind”? If one eye has unoperated cataract and the other eye has had cataract surgery but complications mean that the eye is still blind, is the person included? If 1.5% are bilaterally blind due to cataract and 5.9% are bilaterally blind then 25% of bilateral blindness is due to cataract. It is important to know the assumptions that go into the definition of bilateral cataract blindness. Again, please relabel the column currently labelled “n”.

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Text updated to better define condition: The age and sex adjusted prevalence of bilateral blindness with correction due to cataract (defined as pinhole VA less than 3/60 in both eyes with obvious lens opacity in both eyes) was…

Column relabeled.

We are not clear what further data can be presented to display the CSC and eCSC by sex. We are unable to say whether the differences are significant.

The authors note that government hospitals have worse outcomes compared to private facilities. Please present the findings by sex: were women more likely to use the government hospitals? Were women more likely to have poor outcomes?

The proportion of eyes operated at government hospitals was similar in males and females (26.0% and 22.3% respectively). The sample proportion of poor post-operative visual outcomes in eyes was 28.3%. Poor outcomes occurred in 25.1% of eyes in males and 31.8% of eyes in females. These findings have been included in the text.

What is meant by “voluntary” sites?

Charitable/ faith-based organizations. This terminology has been updated.

Overall, 66% of surgeries were done in private facilitates. Was there a difference in outcome (men to women) among those attending the private facilities? More detail is needed to interpret the findings.

These data by facility are not further disaggregated by sex in standard RAAB analyses as the sub- groups are considered too small for comparison. http://bmjopen.bmj.com/

A ‘barriers to surgery’ question is included in all RAAB surveys as standard and is a frequent output of analysis. The cost of out of pocket payment at the private facilities ranged from 250 USD to 500 USD. on September 27, 2021 by guest. Protected copyright. The government usually provides surgery at no cost or low cost (around 50 USD). This information has been added to the text.

Text amended to read “under-represented”.

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The comparable point estimate for blindness from Menofiya of 7.9% was not accompanied by 95% confidence intervals in the journal paper (extracted from Table 2) we read. (Fouad D, Mousa A, Courtright P. Sociodemographic characteristics associated with blindness in a Nile Delta governorate of Egypt. British Journal of Ophthalmology. 2004;88:614-8.) We were unable to find more information than this. If a reference with 95% confidence intervals can be shared for citation we will be able to update the manuscript. In the meantime, we have updated the text as follows: Compared to this finding, the point prevalence estimate of blindness in Egypt has decreased.

Later in the discussion the authors stated that the CSC was slightly higher in women than men. A more accurate statement would be that the CSC were similar.

Text updated to reflect this.

The authors state that the government facilities offer ECCE. Is this true at all government facilities? Do all private facilities do phaco? Is small incision practiced? Are IOLs implanted on all ECCE cases? While the reader appreciates that the authors were attempting to survey vision loss in Sohag much more information regarding the current eye care services should be provided (ideally in the introduction) to help the reader interpret the findings.

Introduction edited accordingly.

Reviewer 3

Abstract: the results should be stratified by sex, as you refer to gender differences in the conclusions

We have removed the gender difference statement in abstract. Although reporting sex disaggregated estimates were not an objective of this study, we believe the differences in sex are worth mentioning in the paper given the historic trend observed in Egypt.

Introduction: http://bmjopen.bmj.com/

The number of hospitals is included as a basic description of the setting, how this number might

influence the prevalence of blindness is not a straightforward relationship to speculate on. We stated on September 27, 2021 by guest. Protected copyright. the CSR in Sohag relative to the national average to provide some further context for the setting.

Objective: If there are gender differences in Egypt, why you do not reflect those in the objectives of the study?

RAAB survey objectives are relatively standardised. The RAAB sample size calculator does not take into consideration prevalence estimates disaggregated by sex but we feel the differences found by sex are interesting nonetheless given the previously stated historic trend in surveys. A reference to a gender gap was removed from the introduction to avoid overemphasising what was not a stated objective.

Methods

It would be important to explain if the software apply any correction to better interfere the prevalence regarding the population stratification by sex or age group or you just show the crude results.

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The RAAB sampling approach is not stratified by sex or age group. The age and sex adjusted prevalences are weighted to the age and sex disaggregated census data post-survey. A sentence explaining this has been added to the methods.

Clarify the following sentences

“The prevalence of diabetic retinopathy was used instead of blindness as it was expected to be the lower of the two values”

Text updated: The sample size, calculated using RAAB6 software, was 4,080 individuals, based on an expected prevalence of diabetic retinopathy of 4.25% (25% of the prevalence of diabetes in adults in Egypt), with a precision of 20% of the expected prevalence, at 95% confidence level, non- compliance rate of 15% and a design effect of 1.6 to compensate for clustering. The prevalence of diabetic retinopathy was used instead of blindness as it was expected to be the lower of the two values.

Text updated: We did not directly include participants in the design of the research, however, policy makers in the Ministry of Health and Population (MOHP) and local community leaders were consulted about the survey design, questionnaire and approaches to facilitate the implementation of the study. In partnership with the MOHP, we will disseminate a plain language summary of the findings to the public.

The project team met with the head of the eye health section in the MOHP to orient and give details about the study, its objectives and the nature of the governorate and how to address the needs of the participants following their diagnosis. Referrals were based on this meeting, and the data were planned to be shared with the eye health section. The heads of the health administration in the

governorate and the main government eye hospital were also informed about the study. They were http://bmjopen.bmj.com/ positive about the need for evidence-based planning for the districts. Community leaders were the key in the field, in gaining the trust of the participants and giving detailed information about the maps, composition of the district and tips for dealing with the households in a culturally sensitive way. They gave a plain language description of the study to the public to facilitate the informed consent process.

Results

Table 1. Clarify what District means. It would be interesting to conduct a distribution comparison on September 27, 2021 by guest. Protected copyright. between sample and population in order to see if it is representative. Show the distribution among sex, as it seems you have a vias there.

District has been renamed ‘Governorate’ to relate directly to the Table title and previously used terminology regarding the setting. The table permits a distribution comparison between the sample and the population by age group and sex.

The order of the causes of VI are listed in a standardised format in RAAB - this follows the WHO ordering of most to least treatable/preventable conditions. We were concerned readers familiar with RAAB output may misinterpret causes dropped from the table to have been omitted in error.

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Early VI? Why you disaggregate to that many categories? Does it provide interesting information in order to produce policies or actions? If not, I would aggregate it.

The RAAB survey analysis provides VI categories disaggregated to this level as standard so we included the full detail available.

Table 4. It would be useful to show the total visually impaired by sex. As female are older than males it age has a high correlation with age, any comparison should be adjusted.

Table 4 prevalence estimates are age and sex adjusted. They have been presented as discrete categories for continuity with Table 2.

Table 5. I don’t think that stratifying the VA outcome is important in the results.

The VA strata here do not represent outcome data. They are the level of cataract visual impairment at which coverage is considered.

VERSION 2 – REVIEW

REVIEWER Hans Limburg Health Information Services, Netherlands REVIEW RETURNED 10-Mar-2020

GENERAL COMMENTS All my comments have been addressed adequately in this first revision.

REVIEWER Janos Nemeth Dept. of Ophthalmology, Semmelweis University, Budapest, Hungary

REVIEW RETURNED 06-Apr-2020 http://bmjopen.bmj.com/

GENERAL COMMENTS This is an excellent and important manuscript. I would suggest only minor changes and corrections.

ABSTRACT: I would suggest to mention the method used (RAAB) also in the abstract (in Design or Settings).

Please, mention also the other 2-3 most important causes of VI in on September 27, 2021 by guest. Protected copyright. the Results section of the Abstract.

Limitations: I suggest to correct this sentence: “The prevalence of glaucoma may be underestimated due to rapid assessment protocol focusing on visual impairment as the primary outcome.“ The RAAB study is not intended to investigate the prevalence of any disease, nor glaucoma, but only the prevalence of blindness, SVI, MVI and EVI due to different diseases. So, the author has no data on the “prevalence of glaucoma”. Please, do not mention in this way the results.

METHODS: Examination protocol, 2nd part of the 1st Paragraph: Please, clarify: Are you speaking about the diagnosis of glaucoma, or only those glaucomas which caused VI (according to the RAAB study protocol)? (Were you looking for glaucoma diagnosis in case eg uncorrected refractive errors, corneal opacities or cataract as a cause of blindness and VI, or not?)

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RESULTS: Age and gender distribution: The authors mentioned in the Discussion that women were underrepresented in the sample. However, these data are not written among Results. Please, definitely explain there if the 0.73% of the participation in the study of men is statistically significant from the 0.55% of women. I suggest to explain in one extra sentence in the text that the younger generation (50-59) was underrepresented while to older age groups were overrepresented in the sample.

DISCUSSION: 1st Par: Please, mention also that the younger age group was underrepresented and the older groups were overrepresented in the sample.

Please, justify this unsupported statement: „The rapid survey methodology may have underestimated the prevalence of posterior segment conditions such as glaucoma in the governorate.„ Why the authors think so? In general, glaucoma blindness is around 8-10% worldwide for many centuries and the found 8.2% contribution of glaucoma to blindness is well fits to earlier worldwide data. Would need to compare to the results of other RAABs of similar GDP countries. The authors might write a short paragraph also on the other causes of VI.

prevalence data on myopia if this is available for Egypt. http://bmjopen.bmj.com/

VERSION 2 – AUTHOR RESPONSE

This is an excellent and important manuscript. I would suggest only minor changes and corrections.

Thank you for taking the time to review this manuscript and your positive feedback. on September 27, 2021 by guest. Protected copyright.

ABSTRACT:

I would suggest to mention the method used (RAAB) also in the abstract (in Design or Settings).

Please, mention also the other 2-3 most important causes of VI in the Results section of the Abstract.

Both sentences now included.

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So, the author has no data on the “prevalence of glaucoma”. Please, do not mention in this way the results.

Thank you for highlighting this. Limitations and discussion updated to: The rapid survey methodology may have underestimated the contribution of posterior segment conditions to the burden of vision impairment in the governorate.

We have added a new reference to support this statement.

METHODS:

Examination protocol, 2nd part of the 1st Paragraph:

Please, clarify: Are you speaking about the diagnosis of glaucoma, or only those glaucomas which caused VI (according to the RAAB study protocol)? (Were you looking for glaucoma diagnosis in case eg uncorrected refractive errors, corneal opacities or cataract as a cause of blindness and VI, or not?)

Glaucoma was only assigned as a cause of vision impairment in line with the standard RAAB protocol. Text updated to: Glaucoma was considered the cause of vision impairment or blindness based on only obvious pathological signs

RESULTS:

Age and gender distribution:

The authors mentioned in the Discussion that women were underrepresented in the sample. However, these data are not written among Results. Please, definitely explain there if the 0.73% of the participation in the study of men is statistically significant from the 0.55% of women. http://bmjopen.bmj.com/

The over-representation of males in now explained in the new Results sentence below. In the discussion we have acknowledged that all prevalence estimates were presented adjusted rather than crude given the differences between the sample and the population data.

I suggest to explain in one extra sentence in the text that the younger generation (50-59) was on September 27, 2021 by guest. Protected copyright. underrepresented while to older age groups were overrepresented in the sample.

New sentence added: The proportion of males in the sample was higher than the population (59.2% and 52.1% respectively); there was a statistically significant difference in the proportions of the male and female population included in the sample (0.73% vs 0.55% (p<0.001; two-sample test of proportions)). The youngest age group (50-59) was under-represented in the sample in contrast to the three older age groups.

DISCUSSION:

1st Par:

Please, mention also that the younger age group was underrepresented and the older groups were overrepresented in the sample.

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This has been included.

While we acknowledge the contribution of glaucoma to vision impairment in this survey is in line with global estimates, we believe a limitation of the rapid survey examination protocol is that anterior segment causes, particularly cataract and uncorrected refractive error, can be prioritised as the main cause of vision impairment over posterior segment conditions. We had used glaucoma here as an example of a posterior segment condition that may be underestimated on account of this but will make a more general point. We have added a recent reference to support this statement.

Zhang XJ, Leung CKS, Li EY, et al. Diagnostic Accuracy of Rapid Assessment of Avoidable Blindness: A Population-based Assessment. Am J Ophthalmol. 2020;213:235-243. doi:10.1016/j.ajo.2019.12.009

The authors might write a short paragraph also on the other causes of VI.

We have added the following sentences: Non-trachomatous corneal opacity was the second most common cause of blindness. Further information on its causes are not available from this survey but merit further investigation as public health interventions for avoidable causes may be feasible. We found no other relevant literature on the causes of non-trachomatous corneal opacity in the population in Egypt.

Separate publications will be produced focusing on 1) diabetic retinopathy and 2) uncorrected http://bmjopen.bmj.com/ refractive error.

Concerning the possible overestimation of uncorrected refractive errors you might take into account that some myopic subjects have good near visual acuity at older ages and need no glasses for reading. You might make some assumption based on the national prevalence data on myopia if this is on September 27, 2021 by guest. Protected copyright. available for Egypt.

Thank you for this suggestion. We intend to review refractive error results in greater depth in a separate publication (including qualitative data from a follow up study) and will seek to address it there.