Epidemiology & Technology

Blog Archive

MEDRES Custom fork of ODK Collect

green and red metal trash bins
GitHub Repository: drguptavivek/collectLast Updated: January 28, 2026Version: v2025.3.3-MEDRES-RC4Backend (ODK Central): Custom fork designed to work in tandem with MEDRES Collect Why MEDRES Exists Field medical research in resource-constrained environments faces unique challenges that standard data collection tools don't address. Researchers work in remote areas with unreliable connectivity, share devices across

Height of Tumbling E for Visual Acuity Assessments at various distances

person holding eyeglasses
When developing mobile apps / charts for assessing visual acuities using Snellen's / LogMAR notation, there is a need to estimate the size of letters for a given working distance for assessing a specific cutoff. Under normal vision, for a visual acuity of 6/6, the whole letter subtends an angle

Evolution of Definitions of Visual Impairments

In recent months one thought has been occurring to be regarding classification of Visual Impairment and blindness. ddd ddd I find it is strange that the most widely understood classification of blindness and visual impairment in surveys do not have complete grounding in ICD-10/ ICD-11. As you will see below,

Estimating Indian zonal populations in 2024 using two data sources

The MOHFW projections The UN Population projections : My age groups of intertest were: 0-1516-3031-4546-6061-75>75Age groups of Interest In order to arrive at Administrative zone wise estimate populations for 2024, for my age grousp of interest, I recently used the following methodology: The Estimated population in each zone in each

Understanding Cataract Prevalence and Operated variables in RAAB

black flat screen computer monitor
There are various ways that cataract can be defined when analysing data from RAAB surveys. Here, I review the RAAB Analysis R scripts to understand how it is being done in the autogenerated tables. Understanding the case_when syntax This syntax is used very commonly for creating new variables based on

Using RAAB6/RAAB7 Analysis R scripts on Desktop

The RAAB team has provided the analytic scripts on the GitHub repo. Once you download the scripts, you need some configuration on your desktopn to be able to use them. First is obviously you need to install R package. You also need to install pandoc [from here] Then you need

Global Estimates of Blindness and Visual Impairments

Data from various global estiamates are summarized here for easy reference: Link to my personal google sheet: https://docs.google.com/spreadsheets/d/1iTgBmRA4VwWE1fzRKA1YD1fzzMvn90Vu/edit?usp=sharing&ouid=113111648583609130450&rtpof=true&sd=true Pascolini, 2010 NUMBERS (millions)WorldIndiaPopulation6737.901181.40Visual Impairment ( PVA < 6\18)285.3962.62Blindness (PVA < 3\60)39.378.08Low Vision (< 6\18-3\60)246.0254.54PREVALENCE (1000 per million population)WorldIndiaVisual Impairment ( PVA < 6\18)42.3653.00Blindness (PVA < 3\60)5.846.84Low Vision (< 6\18-3\60)36.5146.17 20102010GLOBALGLOBALBlindness PVA

Visual Acuity Conversion Chart

In order to simplify my life when dealing with variations in Visual Acuity Charts when dealing with data from different surveys, I have created the following table for VA conversions What about PL+ / PL-, FCCF etc LogMAR for 1/60 vision is 1.78, rounded off to 1.8 as used in

ICD 11 Vision Categories

When analyzing data from blindness surveys, one needs to map out visual acuity against the Visual impairment categorized in ICD. There are some nuances, especially w.r.t Moderate visual impairment (MVI) based on the charts used as some VA charts yield 6/18 vision while others yield 6/19. ICD11 Categories Based on

Stata Code for generating corneal opacity outcomes from RAAB 6 surveys

grayscale photography of person's eye
Corneal Opacity Related Outcomes There are four sets of variables Stata Code The above Stata code can be used by anyone under a CC-BY-SA license.