Vision test and image test validation

Development and Validation of a Smartphone-Based Visual Acuity Test (Peek Acuity)

JAMA Ophthalmology

Validation study conducted from December 11, 2013, to March 4, 2014, comparing results from smartphone-based Peek Acuity to Snellen acuity (clinical normal) charts and the Early Treatment Diabetic Retinopathy Study (ETDRS) logMAR chart (reference standard)

This study was nested within the 6-year follow-up of the Nakuru Eye Disease Cohort in central Kenya and included 300 adults aged 55 years and older recruited consecutively.

Outcome measures were monocular logMAR visual acuity scores for each test: ETDRS chart logMAR, Snellen acuity, and Peek Acuity. Peek Acuity was compared, in terms of test-retest variability and measurement time, with the Snellen acuity and ETDRS logMAR charts in participants’ homes and temporary clinic settings in rural Kenya

The 95% CI limits for test-retest variability of smartphone acuity data were ±0.033 logMAR. The mean differences between the smartphone-based test and the ETDRS chart and the smartphone-based test and Snellen acuity data were 0.07 (95% CI, 0.05-0.09) and 0.08 (95% CI, 0.06-0.10) logMAR, respectively, indicating that smartphone-based test acuities agreed well with those of the ETDRS and Snellen charts. The agreement of Peek Acuity and the ETDRS chart was greater than the Snellen chart with the ETDRS chart (95% CI, 0.05-0.10; P = .08). The local Kenyan community health care workers readily accepted the Peek Acuity smartphone test; it required minimal training and took no longer than the Snellen test (77 seconds vs 82 seconds; 95% CI, 71-84 seconds vs 73-91 seconds, respectively; P = .13).

Conclusions and relevance: The study demonstrated that the Peek Acuity smartphone test is capable of accurate and repeatable acuity measurements consistent with published data on the test-retest variability of acuities measured using 5-letter-per-line retroilluminated logMAR charts.

The study conducted in Kenya compared Peek Acuity to clinical and reference standard acuity tests and was found to be accurate, repeatable and time efficient to deliver in the hands of health and non health workers

JAMA Ophthalmology 2015 Aug;133(8):930-7


Development and Validation of a Smartphone-based Contrast Sensitivity Test

Translational Vision Science & Technology

Contrast sensitivity (CS) testing is an important measure of visual function reflecting variations in everyday visual experience in different conditions and helps to identify more subtle vision loss. However, it is only infrequently used. To make this more accessible, Peek developed and validated a smartphone-based CS test

This was field tested and refined through several iterations in Ethiopia. Reference standard was a tumbling-E Pelli-Robson CS test (PRCS). The validation study was conducted in community clinics in Ethiopia. Test-retest variability was measured for both PRCS and PeekCS. PRCS and PeekCS were then compared. Correlation coefficients and 95% confidence intervals (CIs) were calculated; 95% limits of agreement were calculated and displayed on Bland-Altman plots.

PeekCS showed strong repeatability (correlation coefficient: 0.93; 95% CI: 0.91-0.95), which was comparable with PRCS (correlation coefficient: 0.96; 95% CI: 0.95-0.97). The 95% limit of agreement for test-retest variability of PRCS and PeekCS were -0.20 to 0.21 and -0.31 to 0.29, respectively. PRCS and PeekCS were highly correlated: 0.94 (95% CI: 0.93-0.95); 95% limits of agreement -0.27 to 0.29; and mean difference 0.010 (95% CI: -0.001 to 0.022). PeekCS had a faster testing time (44.6 seconds) than PRCS (48.6 seconds): mean difference -3.98 (95% CI: -5.38 to -2.58); P < 0.001.

The smartphone-based PeekCS is a repeatable and rapid test, providing results that are highly comparable with the commonly used PRCS test.

Translational relevance: PeekCS provides an accessible and easy to perform alternative for CS testing, particularly in the community setting.

Trans Vis Sci Tech. 2019; 8(5):13, tvst.8.5.13


Clinical Validation of a Smartphone-Based Adapter for Optic Disc Imaging in Kenya

JAMA Ophthalmology

“This validation study compared the grading of optic nerves from smartphone images with those of a digital retinal camera. Both image sets were independently graded at Moorfields Eye Hospital Reading Centre…”

JAMA Ophthalmology 2016;134(2):151-158


Red reflex examination in reproductive and child health clinics for early detection of paediatric cataract and ocular media disorders: cross-sectional diagnostic accuracy and feasibility studies from Kilimanjaro, Tanzania.

Mndeme FG, Mmbaga BT, Kim MJ, Sinke L, Allen L, Mgaya E, Bastawrous A, MacLeod D, Burton MJ, Gilbert C, Bowman R.

Eye (Lond). 2020 Jun 16. doi: 10.1038/s41433-020-1019-5. Online ahead of print.

PMID: 32546747

FINDINGS: Diagnostic accuracy study: estimated sensitivities were 97.6% for Catcam, 92.7% for Arclight, 90.2% for PEEK retina and 7.3% for torchlight. Estimated specificities were above 90% for Catcam, Arclight and torchlight and 87% for PEEK retina. …


Smartphone Fundoscopy


“More ophthalmologists than ever carry a smartphone with them on a daily basis. There are many ophthalmic applications (apps) and reference texts available on a variety of platforms…”

Ophthalmology , Volume 119 , Issue 2 , 432 – 433.e2


Acceptability, Usability, and Views on Deployment of Peek, a Mobile Phone mHealth Intervention 

JMIR Mhealth Uhealth

“Shortages in ophthalmic personnel, the high cost, and the difficulty in transporting equipment have made it challenging to offer services, particularly in rural areas. Peek offers a solution for overcoming barriers of limited access to traditional ophthalmic testing methods and has been pilot tested on adults in Nakuru, Kenya, and compared with traditional eye examination tools…”

JMIR Mhealth Uhealth 2016;4(2):e30


Smartphone-Guided Algorithms for Use by Community Volunteers to Screen and Refer People With Eye Problems in Trans Nzoia County, Kenya: Development and Validation Study

Rono H, Bastawrous A, Macleod D, Bunywera C, Mamboleo R, Wanjala E, Burton M.

JMIR Mhealth Uhealth. 2020 Jun 19;8(6):e16345. doi: 10.2196/16345.

PMID: 32558656 Free PMC article.

BACKGROUND: The provision of eye care services is currently insufficient to meet the requirements of eye care. …In particular, we developed the Peek Community Screening app and assessed its validity in making referral decisions for patients with eye


Antarctica eye study: a prospective study of the effects of overwintering on ocular parameters and visual function

Stahl MH, Kumar A, Lambert R, Stroud M, Macleod D, Bastawrous A, Peto T, Burton MJ.

BMC Ophthalmol. 2018 Jun 25;18(1):149. doi: 10.1186/s12886-018-0816-0.

PMID: 29940901 Free PMC article.

This is the first study of its kind to investigate the effect of overwintering in Antarctica on the human eye. METHODS: Pre and post-expedition clinical observations were made including visual acuity, contrast sensitivity, colour vision, auto-refraction, subjective refract …


Photometric Compliance of Tablet Screens and Retro-Illuminated Acuity Charts 

PLoS One

“This study photometrically characterised seven tablet computers (iPad, Apple inc.) and three ETDRS (Early Treatment Diabetic Retinopathy Study) visual acuity charts with room lights on and off, and compared findings with visual acuity measurement standards…”

PLoS ONE 11(3): e0150676