INTRODUCTION
With the proliferation of smartphones in every sphere of life, ophthalmologists are not left behind. In addition to the general apps used for communication, group discussions, reminders, reading eBooks, etc., there are now several hundred apps specifically targeted at ophthalmologists, most of them released in the year 2015 and later. However, many of them are made without professional ophthalmologist involvement in development and finding a good app is difficult.[1]
The advantages of using smartphones are many. It is a matter of convenience as most ophthalmologists already carry a smartphone. Apps can be easily installed and uninstalled, and most of these apps are free. They have internal data storage and cloud storage capabilities built in. In fact, smartphones drive the majority of recent innovations in ophthalmology.[2] High-resolution smartphone screens can help in assessing visual acuity with great accuracy. EyeNetra and Netra-G are smartphone-based autorefractors which use the high-resolution screens of modern smartphones to calculate refractive error using a headset.[3] Gyroscopic sensors have helped in the development of toric intraocular lenses (IOL) marking apps. Better cameras have helped in smartphone slit-lamp and fundus photography. Several complex ophthalmic calculations, including IOL power calculations, are now possible on apps. Virtual reality (VR) perimetry uses smartphones inside a VR headset.
There are several apps for ophthalmologists including patient testing apps, ophthalmic calculators, patient education apps, ophthalmologist education apps, ophthalmologist reference apps, eBook apps, electronic medical record apps, toric marker app, and capsulorhexis training. There are some apps, such as the Eye Handbook[4] [Figure 1], which do a variety of things such as comprehensive patient vision assessment, ophthalmic calculations, international classification of diseases, Vision Atlas, and more. Many other apps are specialized in one or a few tasks only.
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Figure 1: Eye Handbook app menu (image courtesy: Eye Handbook)
VISION TESTING
Several apps help in assessing visual acuity (near[5] and distance),[6] and a recent study concluded that in an emergency setting, visual acuity by a smartphone app is quite reliable[7] though the brightness and contrast of the smartphone screens and the optotype sizes have to be standardized. Unique in visual acuity apps is the Peek Acuity app[8] made for rapid mass vision screening which uses a tumbling E chart and unique gesture-based feedback. Here, the examiner swipes the smartphone screen in the direction the patient points and shakes the phone if the optotype is too small to be visible. This goes on until the app alerts that the visual acuity has been measured[9] [Figure 2]. Another unique visual acuity app is the Eye Chart Pro[10] which pairs an iPhone to act as remote control for an iPad which acts as the display for the visual acuity chart [Figure 3].
Figure 2: Peek vision app (image courtesy: peekvision.org)
Figure 3: Eye Chart Pro with iPhone app paired to iPad app (image courtesy: Eye Chart Pro)
There are several apps for color vision testing using Ishihara's chart which is quite useful; however, we need to be aware of their limitations[11] in sensitivity.[12] Moreover, Ishihara's chart is only for the red-green color deficiency.[13] The more accurate but lesser known Farnsworth–Munsell test is available in a few apps such as Color Blind Test[14] [Figure 4].
Figure 4: Farnsworth-Munsell 15 hue test (image courtesy: Color Blind Test)
Some apps assess contrast sensitivity and color contrast also. ClinicCSF[15] is unique in that it measures contrast sensitivity using sinusoidal gratings. [Figure 5] Another contrast sensitivity testing app with option for both positive polarity and negative polarity testing was found to do better than the conventional printed chart.[16]
Figure 5: Sinusoidal grating contrast sensitivity (image courtesy: ClinicCSF)
What is really unique is that there are some innovative apps such as Stereo Acuity Cardboard[17] which can assess stereo acuity, and depth perception using a smartphone-based VR headset such as Google Cardboard [Figure 6].
Figure 6: Stereo acuity test using virtual reality headset (image courtesy: Stereo Acuity test– Cardboard)
Dysphotopsia can also be measured with the Aston Halometer app, and a study showed comparable results as the C-Quant straylight meter.[18]
OPTOKINETIC NYSTAGMUS DRUM
Some apps, such as Eye Handbook, OptoDrum, Adjustable Optokinetic Nystagmus (OKN) Strips, and OptoDroid, replicate the Optokinetic drum and can be used to test patients' OKN response [Figure 7].
Figure 7: Optokinetic nystagmus drum (image courtesy: Eye Handbook)
OPHTHALMIC CALCULATIONS
Various calculations such as IOL power including toric IOL, surgically induced astigmatism, Visual acuity conversion from meters to feet, corrected IOP, and various optometric calculations such as transpositions can be calculated in the Eye Handbook app [Figure 8].
Figure 8: List of calculations available (image courtesy: Eye Handbook)
APPS FOR GRADING
There are apps for manually grading LOCS III grade of cataract[19] and diabetic retinopathy. [Figure 9] There is even an app for Park's three-step test.[20] A recently published study shows innovation in artificial intelligence[21]-based grading of diabetic retinopathy from smartphone app.[22]
Figure 9: Cataract grading (image courtesy: LOCS III app)
SLIT-LAMP, GONIOSCOPY, SPECULAR, AND FUNDUS PHOTOGRAPHY
Slit-lamp photography is helped by affordable smartphone slit-lamp adapters. It can be also be used to take gonioscopy videos and even specular photographs of corneal endothelium[23] [Figure 10].
Figure 10: Specular reflection photograph of endothelium (image courtesy: Dr. John Davis)
The technique of smartphone fundus photography has been described in detail by several authors with even open-source documentation for building your own smartphone fundus camera.[24] However, one of the difficulties is that the inbuilt camera app is not ideal for the technique. Ullman Indirect[25] for iPhone and several apps, including HopeScope[26] and Ullman Indirect on Android,[27] have features such as inverted video, focus lock, and flash brightness control [Figure 11].
Figure 11: Camera app with settings for fundus photography (image courtesy: Ullman Indirect)
SMARTPHONE PERIMETRY
Tablet-based perimeters such as visualFields easy[28] and VR-based perimeters such as Periscreener[29] are in development and testing. Studies have been done on both tablet[30]-based[31] and VR-based perimeters[32] and found promising results especially when conventional perimeters are inaccessible [Figure 12].
Figure 12: (a) Humphrey field analyzer (HFA) reports (b) Patient doing virtual reality perimetry on periscreener (c) Reports from periscreener (image courtesy: Periscreener.com)
FOR TEACHING OPHTHALMOLOGY
In addition to various eBooks and journals available as apps, there are some unique apps which help in learning ophthalmology. There is an app called cataract surgery,[33] which is a simulator of capsulorhexis and phacoemulsification surgery. [Figure 13] Although it is a very basic app, it would be useful to explain to a fresh student of ophthalmology the intricacies of surgery in an interactive manner. A decision support app called OphthalDSS helped in clinical decision-making and was evaluated in a study.[34] For clinical ophthalmology slit-lamp teaching, a smartphone connected SmartTV-based system was found to be better than the conventional slit-lamp teaching telescope which is restricted to one person at a time.[35] For teaching ophthalmoscopy, another study evaluated a smartphone-based VR headset that had tasks incusing performing eye examinations and diagnosing disease and tests.[36]
Figure 13: Phacoemulsification simulation (image courtesy: CataractMobile app)
SCREENING
Smartphone photographs can be used for screening for leukocoria; however, we need to be aware that false positives may also happen due to off-axis photographs.[37] Screening of children for other risk factors for amblyopia can be done with the GoCheck Kids app with the smartphone attachment.[38] Dry eye disease screening can also be done by apps which can give questionnaire and do a functional visual acuity test.[39]
PATIENT MEDICATION REMINDER
There are now several apps on which we can set a medication schedule to ring an alarm and remind the patient to follow the correct dosing of medications. Some of these apps are EyeDrop Reminder,[40] MyEyeDrops, eyeDROPS, and RxmindMe. [Figure 14] These are especially useful in chronic diseases such as glaucoma.
Figure 14: MyEyeDrops app (image courtesy: Singapore National Eye Center)
OTHER INNOVATIVE APPS
Optical coherence tomography (OCT) browser app[41] made by the University of Pittsburgh can be used to browse all the slices of a spectral-domain OCT in an iPad instead of being restricted to the OCT machine [Figure 15].
Figure 15: Optical coherence tomography being viewed on iPad (image courtesy: Optical coherence tomography browser app)
One study used the smartphone to measure anomalous and compensatory head positions.[42] The availability of the gyroscopic sensor in newer smartphones made this easier and more accurate.
Based on the same principle, there are apps to help mark the position for toric IOL insertion.[43]
There are vision simulator apps to show patients the type of vision to be expected in different types of IOLs and other apps to simulate vision due to glaucoma and diabetic retinopathy. There are VR versions of these simulators too.[44] They can be accessed on mobile or desktop and show a 360° view of what is seen by a person with glaucoma, cataract, presbyopia, diabetic retinopathy, macular degeneration, and glare of varying degrees which we can select.[45] [Figure 16].
Figure 16: Vision of a person with glaucoma (image courtesy: Sight Loss Simulator)
Another study used a smartphone-based VR glaucoma visual function test to objectively assess activity limitation in glaucoma.[46]
There are also several amblyopia treatment apps which help to exercise the eye, however, a study noted that many of these apps are made without any professional input and so need to be assessed and validated.[47]
Language translator apps for ophthalmologists to communicate specific ophthalmology-related questions and phrases are also available in Tamil[48] and Bangla.[49]
CONCLUSION
Smartphone apps are rapidly evolving, and new innovative apps are being released often. However, many of the apps are made without ophthalmologists' guidance and are often not calibrated or validated for use. With currently available technology, we have the resources to make reliable and reasonably accurate apps for many components of ophthalmological evaluation at a much lower cost compared to conventional techniques.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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