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Luis Haddock, David Kim, Francois Delori, Shizuo Mukai; Novel and safe technique for smartphone fundus photography: Application in human and animal eyes. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5869.
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© ARVO (1962-2015); The Authors (2016-present)
We describe a novel technique of smartphone fundus photography in human and rabbit eyes. We measured the retinal irradiance of the system to confirm the photobiological safety of this technique in human eyes
Smartphone fundus images were captured with an iPhone 4 (Apple Inc, Cupertino, CA) and a 20D lens using the coaxial light source of the phone as an indirect ophthalmoscope.The application Filmic Pro (Cinegenix LLC, Seattle, WA) was used to control focus and exposure while a Koeppe lens was used to maintain a clear view. Video capture was used with subsequent still-image extraction.Light levels were measured with a radiometer (United Detector Technology, San Diego, CA) by placing the light source 30 cm in front of the 20D lens and measuring radiant power at 5 cm behind the lens. The radiant power was measured for a 50° field of retinal irradiance. The spectral distribution was measured with a spectroradiometer (USB4000 Ocean Optics, Dunedin, FL). Similar measurements were made on a standard indirect ophthalmoscope, Keeler Vantage Plus LED (Keeler Instruments, Broomall, PA) for comparison.
The described technique of smartphone fundoscopy captured excellent images in awake adults and children under anesthesia (Figure 1). Photodocumentation of rabbit fundus was achieved in control and experimental eyes (FIgure 2). Light level measurements revealed that the light source radiant power was 8 mW. The weighted retinal irradiance was 4.6 mW/cm2,150 times below the thermal hazard limit (706 mW/cm2) set by the International Organization for Standardization (ISO 15004-2.2). The weighted retinal radiant exposure was 41 mJ/cm2 (duration of 1 minute), 240 times below the photochemical hazard limit (10 J/cm2). The spectral distribution was limited to the 400-700 nm wavelength with 70% of light in the blue/green part of the spectrum. Light levels produced by Keeler Vantage Plus LED ophthalmoscope were 10 times those of the smartphone. Both devices had similar spectral distribution.
High quality fundus images can be captured using the camera and light source of the iPhone 4 in combination with the application Filmic Pro and a Koeppe lens. The iPhone 4 light source when used with a condensing lens for smartphone fundoscopy with the described technique was well within the safety standards for human eyes.
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