Undermining a common language: smartphone applications for eye emergencies

Figures & data

Figure 1 Identification of relevant smartphone studies.

Figure 2 Selection of Canadian smartphone applications.

Figure 3 Selection of Irish smartphone applications.

Table 1a Results of systematic application review, Canada (n= 24)

App Name	Provider	Cost ($)	Store	Explicitly specifies which HCP	For Whom	Explicitly mention validated	How	Disclaimer present	Disclaimer (up to 44 words)
AmblyoCare	RISC Schware Grmbh	Free	Google Play	Yes	Ophthalmologists, orthoptists, ESIT specialists, pediatrists, neurologists, medical specialists	No	n/a	Yes	“the software may only be used in those European countries where one or both of these [English or German] languages is defined as an official language”
AmblyopiaVA	Manuel Rodriguez Vallejo	21.99 (iTunes) 26.78 (Google Play)	Both	Yes	Optometry and ophthalmology practice	No	n/a	No	n/a
ClinicCSF	Manuel Rodriguez Vallejo	59.99	iTunes	Yes	Optometrists and ophthalmologists	Yes	measured the chromatic characteristics of the devices [computers or portable devices such as Tablets or iPad] with the Spyder4Elite Colorimeter	Yes	For tablets, not for use on smartphones
Eye Chart HD - Screen Vision with Pocket Snellen, Sloan, Near Vision, and Amsler Grid Test	Dok LLC	Free	iTunes	No	“Triage, house visits, patients who have memorized the office chart” selected as implied HCP	No	n/a	Yes	“Should not be used as a primary visual acuity measuring tool, it can provide a handy rough vision screen when a chart is not available, or it can be used to complement static, wall- based Snellen charts.”
Eye Chart Premium	Dok LLC	39.99	iTunes	No	“Triage and hospital bedside, testing patients who have memorized the office chart” selected as implied HCP	No	n/a	Yes	“Should not be used as a primary visual acuity measuring tool, it can provide a handy rough vision screen when a chart is not available, or it can be used to complement static, wall-based Snellen charts.”
Eye Chart Pro Test Vision and Visual Acuity better with Snellen, Sloan, ETDRS, and Near Vision!	Dok LLC	Free	iTunes	No	“Triage, house visits, patients who have memorized the office chart” selected as implied HCP	No	n/a	Yes	“Eye Test Pro should not be used as a primary visual acuity measuring tool, it can provide a handy rough vision screen when a chart is not available, or it can be used to complement static, wall-based Snellen charts.”
Eye Chart Professional	Dok LLC	139.99	iTunes	No	“House visits, hospital bedside testing, or mounted to a wall” Selected as implied HCP	No	n/a	No	n/a
Eye Emergency Manual	Agency for Clinical Innovation	Free (both iTunes and Google Play)	Both	Yes	Medical, nursing, and allied health clinicians in Emergency Departments across New South Wales	No	n/a	Yes	“These guidelines have not undergone a formal process of evidence based clinical practice guideline development however they are the result of consensus opinion determined by the expert clinician working group”
Eye Handbook	Cloud Nine Developer	Free (both iTunes and Google Play)	Both	No	“Anyone involved in eye care” selected as implied HCP	No	n/a	No	n/a
EyeTest Droid	George YX Kong	Free	Google Play	Yes	General practitioners, ophthalmologists, optometrists, opticians, and medical and optometry students	No	n/a	Yes	“Note eyeTests is not a substitute for a full ophthalmic examination by an optometrist of ophthalmologist”
EyeTestsFree	George Kong Software	Free	iTunes	Yes	General practitioners, ophthalmologists, optometrists, opticians, and medical and optometry students	No	n/a	Yes	“Note eyeTests is not a substitute for a full ophthalmic examination by an optometrist of ophthalmologist”
EyeTests Easy	George Kong Software	Free	iTunes	Yes	General practitioners, ophthalmologists, optometrists, opticians, and medical and optometry students	No	n/a	Yes	“Note eyeTests is not a substitute for a full ophthalmic examination by an optometrist of ophthalmologist”
Morphision	Constantin Chifor	Free	iTunes	Yes	Ophthalmic professionals	No	n/a	No	n/a
NEOD Acuity	NEOD Inc.	209.99	iTunes	Yes	Vision care specialists	No	n/a	No	n/a
OKN+	Medical	3.99	iTunes	Yes	Healthcare professionals	No	n/a	No	n/a
OphthDocs Eye App	Sheng Chiong Hong	Free	iTunes	Yes	Healthcare providers, ophthalmologists and optometrists	Yes	by ophthalmologist. For more information visit www.ophthalmicdocs.com	No	Website no longer exists
Pocket Eye Exam	Nomad	2.79 (iTunes) Free (Google Play)	Both	Yes	Neuro-ophthalmologists, neurologists, optometrist, medical school students and residents	Yes	Updated for Android 4.0 devices. Not tested for 5.0+. Tested on HDPI screen (Samsung Captivate) and works. MDPI and LDPI screens do not display Snell and Pupil Chart correctly.	No	n/a
Professional Clinical	Ossibus Software	26.52	Google Play	Yes	Optometrists, ophthalmologists, neurologists, medical doctors, optometric technicians, nurses, EMTs, medical assistants, and other healthcare providers	No	n/a	Yes	“These tools are very useful for screening purposes, but are not necessarily recommended for diagnosis” …”This app is intended for informational purposes only and not for the diagnosis, treatment, or cure of any medical conditions or illness.” “…”
Random Eye Chart Generator	Dok LLC	2.79	iTunes	No	“Triage, house visits, patients who have memorized the office chart” selected as implied HCP	No	n/a	Yes	“Should not be used as a primary visual acuity measuring tool, it can provide a handy rough vision screen when a chart is not available, or it can be used to complement static, wall-based Snellen charts.”
MultiQuity	Sightrisk	Free	iTunes	Yes	Eye care professionals	No	n/a	Yes	“The results and interpreation [sic] of the multiQuity suite are to be entrusted to eyecare professionals only”
Smart Optometry	Smart Optometry	9.99	iTunes	Yes	Eye-care practitioners	No	n/a	No	“Precise: Eye testing and screening oftern [sic] requires eye-care professionals to make calculations - giving the room for error. Eliminate this risk with precise calculations done by our Smart Optometry application. Our test are as precise if not more than the currently use on-the-wall testing equipment”
Smart Optometry Lite	Smart Optometry	Free	iTunes	Yes	Eye-care practitioners	No	n/a	No	“Precise: Eye testing and screening oftern [sic] requires eye-care professionals to make calculations - giving the room for error. Eliminate this risk with precise calculations done by our Smart Optometry application. Our test are as precise if not more than the currently use on-the-wall testing equipment”
Visual Acuity XL	Kybervision Japan LLC	69.99	iTunes	Yes	Vision care specialists	Yes	“Validated by a study from the University of Auckland, “An assessment of the iPad as a testing platform for distance visual acuity in adults” published in BMJ Open, June 2013”	Yes	“This app has not been validated yet on ipad [sic] mini with retina display”
VisualFields easy	George Kong Software	Free	iTunes	Yes	Clinicians in clinic or bed-side	No	n/a	Yes	“This app is not designed to substitute formal visual fields testing by optometrists or opthalmologists [sic]. Not all abnormalities found on visual fields test indicate an actual problem. This App does not provide formal interpretation of visual fields”

Table 1b Results of systematic application review, Ireland (n= 24)

App Name	Provider	Cost ($)	Store	Explicitly specifies which HCP	For Whom	Explicitly mention validated	How	Disclaimer present	Disclaimer
AmblyoCare	RISC Software GmbH	Free	Google Play	Yes	ophthalmologists, orthoptists, ESIT specialists, pediatrists, neurologists, medical specialists, and affected people under medical guidance	No	n/a	No	n/a
AmblyopiaVA	Manuel Rodriguez Vallejo	21.99 (iTunes) 23.27 (Google Play)	Both	Yes	Optometrist and Ophthalmologists	No	n/a	No	n/a
AMD Pro, A Metamorphopsia Det.	app4eyes	69	Google Play	Yes	Ophthalmologists, optometrists, opticians	No	n/a	No	n/a
AMD, A Metamorphopsia Detector	app4eyes	Free	Google Play	Yes	Ophthalmologists, optometrists, opticians	No	n/a	No	n/a
Central Vision Test	healthcare- 4mobile	Free	Google Play	Yes	implied mobile HCP	No	n/a	yes	“this application is not intended to replace optician’s regular full examination. We recommend you get a full eye test after using it”.
Eye Chart HD Screen Vision with Pocket Snellen, Sloan, Near Vision, and Amsler Grid Test	Dok LLC	Free	iTunes	Yes	Eye Care Professionals	No	n/a	Yes	“Though this unique, pocket-sized randomizable eye chart should not be used as primary visual acuity measuring tool, it can provide a handy rough vision screen when a chart is not available, or it can be used to complement static, wall based Snellen charts”.
Eye Chart Premium	Dok LLC	29.99	iTunes	Yes	Doctor or Nurse	No	n/a	Yes	“Though this unique, notebook-sized randomizable eye chart should not be used as primary visual acuity measuring tool, it can provide a handy rough vision screen when a chart is not available, or it can be used to complement static, wall-based Snellen charts”.
Eye Emergency Manual	Agency for Clinical Innovation	Free (iTunes and Google Play)	Both	Yes	All medical, nursing, and allied health clinicians in emergency departments across New South Wales	No	n/a	No	n/a
Eye Handbook	Cloud Nine Development LLC	Free (iTunes and Google Play)	Both	Yes	iTunes: Eye Care Professionals Google Play: For anyone involved in eye care. Note: top of description states the following “Complete overhaul of previous design. Extensive reconstruction of form and function. Now available on Android Tablet!”	No	n/a	No	n/a
eyeTests Easy	George Kong Softwares	Free	iTunes	Yes	Eye care clinicians including general practitioners, ophthalmologies [sic], optometrists, opticians, medical and optometry students	No	n/a	Yes	Note: EyeTests is not a substitute for full ophthalmic examination by an optometrist pr [sic] ophthalmologist
eyeTestsDroid	George YX Kong	Free	Google Play	Yes	general practitioners, ophthalmologists, optometrists, opticians, medical and optometry students	No	n/a	Yes	Note eyeTests is not a substitute for a full ophthalmic examination by an optometrist or ophthalmologist.
LogMar Snellen	Hilmi Software	15.65	Google Play	Yes	Doctor or Nurse	No	n/a	No	n/a
Medmont AT20P	Medmont Australia PT	Free	Google Play	No	“people with patients” Implied HCP	No	n/a	No	n/a
Optical Tool	Brent McCardle	2.99	iTunes	Yes	Optometric office, optometrist, and opticians	No	n/a	No	n/a
Optician	familion.ru	Free	Google Play	Yes	students, nurses, and doctors	No	n/a	Yes	please note that these tools provided in this app are used at your own risk and we do not make any claim as to their effectiveness as a testing tool. You should always seek the advice of a trained professional where possible.
Pocket Eye Exam	Nomad	1.99 (iTunes) 1.40 (Google Play)	Both	Yes	Neuro-ophthalmologist, neurologists, optometrists, medical school students and residents	No	n/a	Yes	No disclaimer for iTunes. Google Play (after overhaul) : Tested on HDPI screen (Samsung Captivate) and works, MDPI and LDPI screens do not display Snellen and pupil chart correctly. Updated Android 4.0 devices, not tested for 5.0+
Pocket Ophthalmology	centricweb.co.uk	Free	Google Play	No	“This app aims to discuss treatment protocols, tests, and induction guides followed by a tertiary ophalmology [sic] clinic in the UK” Implied HCP	No	n/a	No	n/a
Professional Clinic	Ossibus Software	27.99	Google Play	Yes	optometrists, ophthalmologists, neurologists, medical doctors, optometric technicians, nurses, EMTs, medical assistants, and other healthcare providers	No	n/a	Yes	This app is intended for informational purposts [sic] only and not for the diagnosis, treatment, or cure of any medical condition or illness. The app should not be used as a substitute for professional medical care or interpretation. Ossibus Software and its writers are not responsible or liable for the use or misuse of the information contained in this app.
Random Eye Chart Generator	Dok LLC	1.99	iTunes	Yes	Eye Care Professionals	No	n/a	Yes	This unique, pocket-sized randomizable eye chart should not be used as primary visual acuity measuring tool, it can provide a handy rough vision screen when a chart is not available, or it can be used to complement static, wall based Snellen charts.
Smart Optometry	Smart Optometry	4.99	iTunes	Yes	Eye Care Professionals	No	n/a	No	n/a
StereoTAB	Manuel Rodriguez Vallejo	19.99	iTunes	Yes	Optometric and Ophthalmology practice	No	n/a	No	n/a
Vision Tests (Complete Package)	Manuel Rodriguez Vallejo	94.99	iTunes	Yes	Optometrist and Ophthalmologists	Yes	“gold standards or current vision tests”. Indicates that further information is available on developer website. However, link from iTunes website not available.test-eye.com which is developers website includes self-referencing in peer reviewed journals which were published after literature search was performed.	No	n/a
Visual Acuity XL	Kybervision Japan LLC	49.99	iTunes	Yes	Vision Care Specialists	Yes	Peer Reviewed Journal (BMJ Open, June 2013)	No	n/a
visualFields easy	George Kong Softwares	Free	iTunes	Yes	Clinicians	No	n/a	Yes	This app is not designed to substitute formal visual fields testing by optometrists of ophthalmologists. Not all abnormalities found on VisualFields test indicate an actual problem. This app does not provide formal interpretation of visual fields. Fixation losses are not tracked in this version of the app.

Abbreviations: ESIT, early support for infants and toddlers; HCP, health care professional; EMTs, emergency medical technicians; HDPI, high dots per inch; MDPI, medium DPI; LDPI, low DPI; NA, not applicable.

Figure 4 Cost of Canadian smartphone applications by platform.

Figure 5 Cost of Irish smartphone applications by platform.

Table 2 Quality assessment of selected apps

	Country	Provider	Vendor	Quality assessment
AmblyoCare	Both	RISC Software	Google Play	***
AmblyopiaVA	Canada only	Manuel Rodriguez Vallejo	Both	*
Eye Handbook	Both	Cloud Nine Developer	Both	***
Pocket Eye Exam	Both	Nomad	Both	**
Visual Acuity XL	Both	KyberVision Japan	iTunes	***

Note:

* No measures of validation internal or external noted;

** some discussion of internal validation or research noted;

*** partial peer or government validation.

Table 3 Demographic data of articles identified in a systematic search of the health literature (n=12)

Reference	Study Design	Subjects (n)	Results	Applications Reviewed, (n)	Methods of assessment (Validity/Reliability/Responsiveness to change)	Primary outcome	Conclusions	Limitations of paper
Aslam et al^Citation33	Threshold testing - 4 phases (initial threshold, threshold, attention check, and final threshold) EDTRS (Landolt C) vs MAVERIC system: specialised software on a tablet computer, housed in a bespoke viewing booth	78	High contrast visual acuity measurements (normal): • mean of 0.003 and SD +/−0.09. • +/−2SD = 0.17 (95 % CI) Low contrast acuity measurements: • mean difference of 0.02 and a SD +/−0.12. • +/− 2SD 0.23 (95 % CI)	2	Reliability Assessment Fixed distance of 40 cm	High and low contract visual acuity measures Versus EDTRS Landolt C	Reliable self-test VA with a high degree of reliability and agreement when compared vs gold standard chart based measurements.	The major limitation at present is screen resolution and this will inevitably improve with time. The ease of availability and mobility of components means that such devices could in future be used for home testing or testing in general practice settings and further studies are needed to confirm this.
Bastawrous et al^Citation29	Validation Study	300 older-aged Kenyan adults	• Test retest variability smart phone VA ±0.029logMAR (95% CI). • The mean differences: • smartphone vs ETDRS 0.07 (95% CI, 0.05-0.09) • smartphone-based test and Snellen acuity data 0.08(95% CI, 0.06-0.10) logMAR. • 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). • minimal training and took no longer than the Snellen test (77seconds vs 82 seconds; 95% CI, 71-84 seconds vs 73-91 seconds, respectively; P= 0.13).	3	Variability test	Monocular logMAR visual acuity scores for each test: ETDRS chart logMAR, Snellen acuity, and Peek Acuity.	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 retro illuminated logMAR charts.	may not be generalizable to other populations.
Black et al^Citation22	Blinded, diagnostic test study	85	• iPad tablet with its glossy screen significantly poorer (approximately 2 LogMAR lines) vs ETDRS chart and a standard computerised testing system (n=56) due to glare. • iPad with an antiglare screen + positioning away from sources creating reflected (veiling) glare = equivalent VA to gold standard (n=29).	2	Comparison	Visual acuity measured under a number of conditions.	Tablets are only suitable for use measuring VA in situations where sources of glare can be eliminated.	• Technological advancement: higher resolution screens. • Distance acuity measurements at 6 m were not limited by the resolution of the screen, as they were indistinguishable from the printed ETDRS chart measurements.
Brady et al^Citation34	Validation Study in participants’ homes and temporary clinic settings in rural Kenya	300	• test-retest variability of smartphone acuity data were ±0.029 logMAR. • mean differences smartphone- based test and the ETDRS chart = 0.07 (95%CI, 0.05–0.09) • smartphone-based test and Snellen = 0.08 (95%CI, 0.06–0.10) logMAR • Agreement of Peek Acuity and the ETDRS chart was greater than the Snellen vs. ETDRS chart (95%CI, 0.05–0.10; P = .08). • 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).	3	Comparison	• monocular logMAR visual acuity scores for: ETDRS chart logMAR, Snellen acuity, and Peek Acuity. • test-retest variability of peak acuity and measurement time	test-retest variability of peek smart phone visual acuity using 5-letter-per-line retro illuminated logMAR charts is consistent with published data.	Generalizability to western population
Chacon et al^Citation35	Validation vs gold standard netbook display for color vision assessment in normal verus colour deficient subjects testing.	32 16 Normal 16 Colour vision deficient.	Both displays showed 100% specificity for confirming CVN and 100% sensitivity for detecting CVD. In CVNs there was no difference between scores on netbook vs. tablet displays. G cone CVDs showed slightly lower G cone contrast test scores on the tablet.	None noted specifically	Validity: ability to discriminate on tablet known normal and deficient colour vision subjects.	• Sensitivity 100% • Specificity 100% of tablet screen to identify subjects normal colour vision and pathologic colour vision	Construct validity shows that tablet can be used to discriminate colour vision normal versus colour vision deficient individuals	Not used as diagnostic test. Didn’t assess discrimination threshold. Did not address glare and distance.
Cheng et al^Citation23	Systematic review of the The Apple iTunes store was searched for iPhone eye care–themed apps	None	In total, 182 apps were identified. The majority of apps lacked community user ratings and had 3,000 or fewer downloads (84% and 69%, respectively). Consistent with other medical specialties, only 37% of apps had documented qualified professional involvement in their development. When stratified by intended audience, 52% and 44% of apps designed for ophthalmologists and optometrists, respectively, had professional input, compared with 31% for non–eye care clinicians and 21% for the general public.	182	None	Description of applications available	• rapid emergence of eye care apps. But a low level of qualified professional involvement in app development and a lack of peer review after publishing remain. • Need for evidence- based principles and standards of app development to be adopted in this emerging area.	Single store, no accompanying literature analysis.
Kollbaum et al^Citation36	Validation of an iPad-based letter contrast sensitivity test versus 2 tests including gold standard for clinical contrast sensitivity paper based measure (Pilli- Robson test) and computer based Freiburg (variable contrast Landolt C presented at eight possible orientations and used a 30-trial Best PEST procedure)	• N=40 • 20 normal • 20 low- vision • tested monocularly at 1 m using each test wearing their habitual correction.	Test retest 95% LoA: iPad =T0.19, Pelli-Robson = T0.19 Freiburg =T0.15. The iPad test showed good agreement with the Freiburg test with similar mean (STD) logCS (iPad = 1.98-0.11, Freiburg = 1.96T0.06); 95% LoA (T0.24), iPad vs. Pelli-Robson had lower values (1.65T0.04). Low-vision subjects (iPad =T0.24, Pelli-Robson = T0.23, Freiburg =T0.21). Agreement between the iPad and Freiburg tests was good (iPad = 1.45T0.40, Freiburg = 1.54T0.37), but the Pelli-Robsontest gave significantly lower values (1.30T0.30).	1	• Ipad good precision (test retest) and good agreement with two test • Low-vision subjects slightly poorer repeatability (iPad = T 0.24, Pelli-Robson = T 0.23, Freiburg = T 0.21). • Poor agreement with the Pelli- Robson test (1.30 T 0.30).	• Precision • Limits of agreement	• iPad test showed good precision • poor limits of agreement with the Pelli-Robson test.	The newly developed application. Did not test visual acuity.
Perera et al^Citation37	• Review of Snellen equivalent for optotype size. • Prospective cohort study visual acuity using the ‘Snellen’ application on an Apple iPhone4.	88	• logMAR of mean difference in visual acuity iphont versus paper was 0.02 logMAR (95% limit of agreement −0.332, 0.372 logMAR). • The subgroup of patients with 6SVA worse than 6/18(n=5) had the largest mean difference. This difference is equivalent to two Snellen visual acuity lines between the charts (0.276 logMAR).	11	Validity	LogMAR/Snellen equivalent VA	• Eye phone apps could not validly discriminate Snellen visual acuity within one line. • There was considerable variability in the optotype accuracy of apps. Further validation is required for assessment of acuity in patients with severe vision impairment.	• Possible selection bias, as the right eye is more frequently the dominant eye and chosen tested eye. If ocular dominance was an important factor in the reading of the chart results may be influenced. • Chart testing order was not randomized. All Snellen visual acuity testing was 1st, followed by the iPhone Snellen acuity chart introducing a possibility of learning effect.
Phung et al^Citation38	• Retrospective chart review reliability and validity • visual acuity measured during the same routine clinic visit with Snellen chart, Rosenbaum near vision card, and SightBook mobile app	126	• SightBook, Snellen, and near card acuities had excellent test– retest reproducibility • SightBook acuities were significantly different from the other measures • Agreement was also poor between the near card and the Snellen acuities (mean absolute difference of 6.4 and 7.6 letters in the right and left eyes)	1	Validity and Reliability	• Acuities were converted to approximate ETDRS letters for statistical purposes	• The discrepancy between SightBook mobile app and the clinic charts acuities are large; however, the results are highly reproducible.	• Small sample size – • N = 123 right eyes and 115 left eyes. • the visual acuities were not always the best-corrected visual acuities. Finally, • only one mobile app was evaluated as a representative application.
Tofigh et al^Citation26	Cross sectional comparison of near visual acuity. • Near vision card • Eye Hand Book app for iPhone 5 from.	100	• Eye Hand Book application overestimates the near VA vs. conventional near vision card by an average of 0.11 LogMAR (P-value of 0.0001)	1	Validity and Reliability	Near LogMAR Visual acuity	• Potential disparity in VA measurement between different platforms. • Contrast and brightness levels of the smartphone’s high-definition screen when compared with the near vision card can effect results.	• Currently out-dated technology • Did not account for glare
Toner et al^Citation39	• Prospective cohort: Validity and Reliability study in children age 6-18 years • Excluded if visual acuity in the worse-seeing eye was less than 20/200 (for validity testing, but not reliability testing).	73	• strong linear correlation (r50.92) • mean difference in acuity 0.005logMAR (less than one letter 95% CI,0.03 to 0.02) • The 95% CI was 2 lines. • Test–retest reliability 81% of retest scores within 0.1 logMAR (5 letters) and 100% within 0.2 logMAR (10 letters). • intra-class correlation coefficient of 0.93, and a standard error of measurement of 0.08	• 2 • Handy Eye Check App • Handy Eye Chart	• Test-retest reliability and validity	• Monocular visual acuity testing using the subject’s poorer-seeing eye	The mobile application is a valid and reliable test of VA in children aged 6–18 years compared with its paper counterpart	Not randomized test order Not for poor vision children
Zhang et al^Citation40	Prospective Cohort: Validation study	120 (consecutive eyes)	• mean difference (bias) of 0.02 logMAR units between the VA results from the iPad chart and the light-box chart • 95% limits of agreement of 20.14 to 0.19. • Better vision: 182 eyes with VA better than 0.1 according to the light-box VA test. The median logMAR VA by the iPad was 0.54 and by the light-box chart it was 0.52; there was no significant difference between them (P¼0.69). • In Group 2, Low vision, there were 58 eyes with VA equal to or worse than 0.1 according to the light-box VA test. The median logMAR VA by the iPad was 1.26 and was 1.10 by the light box; the result from the iPad was significantly lower(P<0.001).	2	Validity	Snellen VA	• Good agreement in patients with better VA (i.e. Snellen VA better than 20/200) • In patients with poor vision (i.e. Snellen VA equal to or worse than 20/200), the results from the iPad chart were worse than from the lightbox chart.	• Visual charts with Snellen notations were compared. Snellen visual charts are not in logMAR steps. • No strict standardization in the examination process and examination conditions. • The brightness of the iPad screen could not be adjusted to be precisely the same as the light-box chart because a light meter was not available. • The height of the light box could not be adjusted to suit each patient’s eye height. • The reading scales of the two kinds of charts were not identical.

Abbreviations: EDTRS, Early Treatment Diabetic Retinopathy Study; VA, visual acuity; MAR, minimum angle of resolution; LoA, limit of agreement; STD, standard deviation.

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