What's it all about?
Phoneoscopy - the use of smart phone cameras in ophthalmoloscopy
T Knott Rowe Referrals & The Equine Eye Clinic, Gloucestershire
While the usefulness of fundus photography for documenting the course of disease, record keeping, client education and telemedicine is well known, simple, accessible and economic methods of recording fundus images have been lacking. Commercially available fundus cameras are outside the reach of many practitioners and while several ingenious individuals have reported methods of converting film retinal cameras (Lowe, 2011) digital camera’s (Pizzirani, 2012) (Victor Hernandez, 2012) or the use of digital cameras to record monocular indirect images (Wills, 2010) a universally accessible technique has been lacking. The author has used a video indirect ophthalmoscopy technique using a commercially available digital video recorder for teaching veterinary students for several years however the technique while useful produced very low resolution images. The production of an adaptor allowing some smart phones (iPhone, Apple) to be attached to the Welch Allyn panoptic indirect ophthalmoscope (IMT, 2011) allows multiple images to be taken using the Panoptic’s own illumination system.
Using the built in camera on a smart phone without modification the author would like to demonstrate that it is possible to record high resolution fundic images, high resolution video and high resolution slow motion video images of the fundus without the use of additional lenses or ophthalmoscopes.
This technique relies on the small size of the smart phone camera lens and the close proximity of the LED light to the optical axis. The use of a camera application (e.g. The Iphone App Camera +, Tap Tap) which allows continuous illumination of the field of view is key to allowing fundic illumination, fundic photography or videography.
The Iphone 4 (Apple, 5 Megapixel) or 4s (Apple, 8 Megapixel) can both be used to produce excellent fundic images. This technique can be applied to any smart phone camera where the LED camera light can be used continuously and is close enough to the camera lens.
Where it is possible to set, the camera’s focal distance should be set to infinity (this is not possible with the iphone 4 or 4s at present however the camera’s autofocus rapidly focuses to infinity when a retinal view is obtained), and in the same manner as a direct ophthalmoscope the camera lens is positioned as close to the patients cornea as possible. The patients corneal and lens optics form a clear retinal image which can be recorded as video or still images. Video images taken with slow motion software (e.g. SloPro, Iphone) allow multiple images to be taken in moving patients from which still images can be later extracted.
While the technique mirrors close direct ophthalmoscopy, where the observers eye is focussed at optical infinity and a small image formed on the retina directly observing the fundus, the iphone lens is considerably “wider angle” than the human eye (equivalent to a 33mm lens, 4.28mm actual focal length) resulting in a field of view in excess of that gained with a 20 dioptre indirect lens. This combination of close proximity to the cornea and a wide angle view also allows easier visualisation of the peripheral fundus as the camera can be readily directed at oblique angles through the pupil. This is especially useful when locating and documenting small peripheral lesions.
The LED light is positioned laterally to the camera lens thus when holding the phone vertically this gives best retinal illumination in patients with horizontallty oblate pupils (equidae, camelids, bovine, ovine etc) while holding the phone horizontally is helpful in patients with vertical pupils (e.g. cats.)
A method to reduce the intensity of the LED light is important in the non-dilated, visual eye. Methods include multiple layers of surgical tape, white plastic, pin hole in black tape, Duck tape and the yellow filter from inside a Compact Disc drive or ophthalmoscope can all be used to reduce light intensity. It is hoped that a software method of reducing LED intensity will become available.
The technique is easy to demonstrate and learn and has proven an invaluable aid in both the teaching of distant direct ophthalmoscopy and the illustration of fundic lesions to both Veterinary Students and in post graduate teaching sessions.
Multiple high resolution fundic images can be stitched together either on a computer or on the phone using intelligent image stitching programmes (e.g. Autostitch, http://www.cs.bath.ac.uk) to produce large full resolution fundic panoramas.
A similar technique can be used to take gonioscopic and posterior chamber images.
Distant direct ophthalmascopic images can be mimicked using the smart phone’s camera with the LED light. The technique has a very shallow learning curve and can be used by clients as an invaluable tool for telemedicine monitoring of patients.
Modification of the smart phone camera with additional lenses both commercial or home-made (Goudie, 2012) can overcome the macro limitations of some phones (the iphone in particular). The use of additional prisms may allow redirection of the LED still close to the optical axis allowing for easier use of this technique in the small pupil. (Lowe, 2012).
This web site was set up to display ophthalmic images captured with the smart phone and all encouraged to contribute to. A selection of images already captured can be seen at facebook.com\equineeyeclinic.co.uk.
While the usefulness of fundus photography for documenting the course of disease, record keeping, client education and telemedicine is well known, simple, accessible and economic methods of recording fundus images have been lacking. Commercially available fundus cameras are outside the reach of many practitioners and while several ingenious individuals have reported methods of converting film retinal cameras (Lowe, 2011) digital camera’s (Pizzirani, 2012) (Victor Hernandez, 2012) or the use of digital cameras to record monocular indirect images (Wills, 2010) a universally accessible technique has been lacking. The author has used a video indirect ophthalmoscopy technique using a commercially available digital video recorder for teaching veterinary students for several years however the technique while useful produced very low resolution images. The production of an adaptor allowing some smart phones (iPhone, Apple) to be attached to the Welch Allyn panoptic indirect ophthalmoscope (IMT, 2011) allows multiple images to be taken using the Panoptic’s own illumination system.
Using the built in camera on a smart phone without modification the author would like to demonstrate that it is possible to record high resolution fundic images, high resolution video and high resolution slow motion video images of the fundus without the use of additional lenses or ophthalmoscopes.
This technique relies on the small size of the smart phone camera lens and the close proximity of the LED light to the optical axis. The use of a camera application (e.g. The Iphone App Camera +, Tap Tap) which allows continuous illumination of the field of view is key to allowing fundic illumination, fundic photography or videography.
The Iphone 4 (Apple, 5 Megapixel) or 4s (Apple, 8 Megapixel) can both be used to produce excellent fundic images. This technique can be applied to any smart phone camera where the LED camera light can be used continuously and is close enough to the camera lens.
Where it is possible to set, the camera’s focal distance should be set to infinity (this is not possible with the iphone 4 or 4s at present however the camera’s autofocus rapidly focuses to infinity when a retinal view is obtained), and in the same manner as a direct ophthalmoscope the camera lens is positioned as close to the patients cornea as possible. The patients corneal and lens optics form a clear retinal image which can be recorded as video or still images. Video images taken with slow motion software (e.g. SloPro, Iphone) allow multiple images to be taken in moving patients from which still images can be later extracted.
While the technique mirrors close direct ophthalmoscopy, where the observers eye is focussed at optical infinity and a small image formed on the retina directly observing the fundus, the iphone lens is considerably “wider angle” than the human eye (equivalent to a 33mm lens, 4.28mm actual focal length) resulting in a field of view in excess of that gained with a 20 dioptre indirect lens. This combination of close proximity to the cornea and a wide angle view also allows easier visualisation of the peripheral fundus as the camera can be readily directed at oblique angles through the pupil. This is especially useful when locating and documenting small peripheral lesions.
The LED light is positioned laterally to the camera lens thus when holding the phone vertically this gives best retinal illumination in patients with horizontallty oblate pupils (equidae, camelids, bovine, ovine etc) while holding the phone horizontally is helpful in patients with vertical pupils (e.g. cats.)
A method to reduce the intensity of the LED light is important in the non-dilated, visual eye. Methods include multiple layers of surgical tape, white plastic, pin hole in black tape, Duck tape and the yellow filter from inside a Compact Disc drive or ophthalmoscope can all be used to reduce light intensity. It is hoped that a software method of reducing LED intensity will become available.
The technique is easy to demonstrate and learn and has proven an invaluable aid in both the teaching of distant direct ophthalmoscopy and the illustration of fundic lesions to both Veterinary Students and in post graduate teaching sessions.
Multiple high resolution fundic images can be stitched together either on a computer or on the phone using intelligent image stitching programmes (e.g. Autostitch, http://www.cs.bath.ac.uk) to produce large full resolution fundic panoramas.
A similar technique can be used to take gonioscopic and posterior chamber images.
Distant direct ophthalmascopic images can be mimicked using the smart phone’s camera with the LED light. The technique has a very shallow learning curve and can be used by clients as an invaluable tool for telemedicine monitoring of patients.
Modification of the smart phone camera with additional lenses both commercial or home-made (Goudie, 2012) can overcome the macro limitations of some phones (the iphone in particular). The use of additional prisms may allow redirection of the LED still close to the optical axis allowing for easier use of this technique in the small pupil. (Lowe, 2012).
This web site was set up to display ophthalmic images captured with the smart phone and all encouraged to contribute to. A selection of images already captured can be seen at facebook.com\equineeyeclinic.co.uk.