The Technology Inside the World’s First Smartphone Based Non Mydriatic Retinal Imaging Device

Annular Illumination Based Optical Design : US Patent 9398851

Remidio's optical design uses Gullstrand principle to separate the illumination and the imaging paths of light to achieve high quality reflex free images of the retina.

Annular Illumination Based Optical Design : US Patent 9398851

Remidio's optical design uses Gullstrand principle to separate the illumination and the imaging paths of light to achieve high quality reflex free images of the retina.
The simple cross polarization based spot illumination, which is often used in compact, portable retinal imaging devices, results in corneal artefacts, and non-uniform illumination distribution, resulting in areas around the macula often being darker than the well-exposed optic disc and nerve fiber layer, as explained by Tran et al, in the journal IOVS

Non Uniform Illumination leading to poor vasculature view around the macula

Non Uniform Illumination leading to poor vasculature view around the macula

The simple cross polarization based spot illumination, which is often used in compact, portable retinal imaging devices, results in corneal artefacts, and non-uniform illumination distribution, resulting in areas around the macula often being darker than the well-exposed optic disc and nerve fiber layer, as explained by Tran et al, in the journal IOVS

Uniform Illumination with no corneal reflexes, clearly visible and sharp vasculature.

Remidio uses annular illumination based optical design to eliminate corneal reflex artifacts, purkinje reflex artefacts as well as specular reflections from the internal limiting membrane to create high quality image of retina, similar to that seen in high quality desktop imaging systems

Uniform Illumination with no corneal reflexes, clearly visible and sharp vasculature.

Remidio uses annular illumination based optical design to eliminate corneal reflex artifacts, purkinje reflex artefacts as well as specular reflections from the internal limiting membrane to create high quality image of retina, similar to that seen in high quality desktop imaging systems
All other smartphone based retinal imaging optical designs involve the use of a simple 20D/28D lens and the use of the flash LED light source inbuilt in the smartphone. Such designs invariably need a pupil size of at least 5 mm to image, result in smaller fields of view, have poor illumination distribution, have purkinje reflex artefacts and are very difficult to use, resulting in poor repeatability of imaging across patients.
All other smartphone based retinal imaging optical designs involve the use of a simple 20D/28D lens and the use of the flash LED light source inbuilt in the smartphone. Such designs invariably need a pupil size of at least 5 mm to image, result in smaller fields of view, have poor illumination distribution, have purkinje reflex artefacts and are very difficult to use, resulting in poor repeatability of imaging across patients.

Enabling Infra-red sensitivity of Smartphone Cameras

Traditional CMOS sensors on smartphones, have an infra red cut filter in their design, that reduces the sensitivity of the camera to infra red light. Remidio’s patented optical design, overcomes this limitation, making nonmydriatic imaging possible down to a 3 mm pupil size, using infra red light for live view !

Enabling Infra-red sensitivity of Smartphone Cameras

Traditional CMOS sensors on smartphones, have an infra red cut filter in their design, that reduces the sensitivity of the camera to infra red light. Remidio’s patented optical design, overcomes this limitation, making nonmydriatic imaging possible down to a 3 mm pupil size, using infra red light for live view !

Use of ISO15004 safety certified medical-grade light sources

There are many smartphone based retinal imaging products that use the LED flash available on the smartphone to take images. These light sources have a spectral distribution different from that required for high quality retinal imaging and are consumer grade light sources. Remidio uses a medical-grade ISO 15004-1,2 approved LED light sources with a color temperature and spectral distribution similar to that seen on high quality desktop fundus cameras.

Use of ISO15004 safety certified medical-grade light sources

There are many smartphone based retinal imaging products that use the LED flash available on the smartphone to take images. These light sources have a spectral distribution different from that required for high quality retinal imaging and are consumer grade light sources. Remidio uses a medical-grade ISO 15004-1,2 approved LED light sources with a color temperature and spectral distribution similar to that seen on high quality desktop fundus cameras.

Wireless Synchronization of external light source with camera shutter

The use of medical grade, external light sources, for infra red live view and white flash for image capture, rather than the in-built smartphone camera flash, necessitated the design of a wireless circuit that ensures that the camera shutter synchronizes at all times with the external light source, with minimal delay not exceeding few tens of microseconds.

Wireless Synchronization of external light source with camera shutter

The use of medical grade, external light sources, for infra red live view and white flash for image capture, rather than the in-built smartphone camera flash, necessitated the design of a wireless circuit that ensures that the camera shutter synchronizes at all times with the external light source, with minimal delay not exceeding few tens of microseconds.

Controlling the voice coil motor on smartphone camera to eliminate effect of chromatic aberrations on image focus

It is well known in optical design that there is a small, but noticeable difference in image foci of the infra red image and the visible light exposed image. The Remidio NM FOP smartphone app pre-programs the voice coil to accommodate for this difference, enabling sharp images using the touch-slider on the app.

Controlling the voice coil motor on smartphone camera to eliminate effect of chromatic aberrations on image focus

It is well known in optical design that there is a small, but noticeable difference in image foci of the infra red image and the visible light exposed image. The Remidio NM FOP smartphone app pre-programs the voice coil to accommodate for this difference, enabling sharp images using the touch-slider on the app.

High Pixel Density, Vibrancy of Colors = Clearer Pictures for Grading

Traditionally fundus cameras have used computer screens to view images. Remidio NM FOP uses a high pixel density (326 PPI) smartphone screen for viewing images. Robert J. Noecker et al, have presented evidence to prove that grading retinal images on an iphone screen is statistically more accurate than grading images on a computer screen, in their publication available here

High Pixel Density, Vibrancy of Colors = Clearer Pictures for Grading

Traditionally fundus cameras have used computer screens to view images. Remidio NM FOP uses a high pixel density (326 PPI) smartphone screen for viewing images. Robert J. Noecker et al, have presented evidence to prove that grading retinal images on an iphone screen is statistically more accurate than grading images on a computer screen, in their publication available here

Blink-free Imaging of the Eye

The use of a fast shutter speed ensures that the images are “blink-proof”, i.e. the image is captured independent of any blink frames. The use of fast shutter speed, however, did pose a significant challenge in the design of the external light source-camera shutter synchronization circuit !

Blink-free Imaging of the Eye

The use of a fast shutter speed ensures that the images are “blink-proof”, i.e. the image is captured independent of any blink frames. The use of fast shutter speed, however, did pose a significant challenge in the design of the external light source-camera shutter synchronization circuit !