The overall goal of this method is to acquire retinal images using a smartphone camera. This method facilitates the recording of ocular fundus images using a smartphone camera and a conventional handheld high-plus power ophthalmoscopy lens. Really, the main advantage of this technique is the widespread nature of smartphones allowing us to capture optic nerve and macula pathology outside of the clinic.
With increasing availability of smartphones and the expansion of telemedicine, this method can be adapted by ophthalmologists and optometrists to document retinal pathologies in emergency room setting and telemedicine consultation for retinal diseases. In addition, healthcare providers may find this method handy in developing countries and in medical aid camps during a disaster rescue operation. Before beginning the imaging, explain the procedure to the patient.
After obtaining permission, deliver two different mydriatic drops two to three minutes apart to the eye that will be examined. Wait 15 to 20 minutes for the pupil to dilate. Then, ask the patient to look at a far target with the other eye and set the smartphone camera to video mode.
Turn on the smartphone flashlight, then cover the light with a semitransparent tape and darken the room. Sit 30 to 60 centimeters in front of the patient on a comfortable chair at about the same level as the patient and press the camera record button to record a continuous video. Using the thumb and index finger, hold an indirect ophthalmoscopy lens in front of the patient's eye and use the middle and ring fingers to stabilize the hand and the lens and to keep the eyelids open.
Move the camera 30 to 35 centimeter from the lens and direct the camera along the patient's pupillary axis aiming the light to the pupil to find the retina glow. Directing the light through the lens onto the retina, move the camera and the lens to find a good focus and an image free of light reflections. The most critical step for acquiring a clear, high-resolution retina image is the proper alignment of patient's pupil, the handheld lens and the camera.
Mastering this step may take time, but it can be achieved with practice. With the lens about three to five centimeters away from the eye, and with the retina image filling the entire lens area, continue to record the video until a good view of the area of interest is captured without significant light reflections or apparitions. Make sure to fill the entire lens with the retina image or you may miss the area of interest.
Now, stop the recording and ask the patient to sit back and be comfortable. Replay the recorded movie. When there is a good retina view within the handheld lens area, stop the movie and capture a screenshot of the image.
Then, magnify the image and capture a screenshot of the larger retina image. The optics of fundus imaging using a smartphone camera is similar in principle to a retina examination with an indirect ophthalmoscope. In smartphone retinal imaging, the smartphone camera's coaxial flashlight and a handheld high-plus power lens create an indirect ophthalmoscopy-like system that is able to record high-resolution digital retinal images.
The portability of smartphones makes smartphone retinal imaging a promising technique for emergency rooms, telemedicine consulting and retinal disease screening programs. For example, these flame-shaped and dot-and-blot retinal hemorrhages were photographed in a patient with nonproliferative diabetic retinopathy in a hospital emergency room. In this image recorded in a hospital floor consultation setting, blurring of the optic disk margins in a patient with non-arteritic anterior ischemic optic neuropathy can be observed.
Smartphone fundus photography may appear a challenging technique in the beginning, however, like any other examination technique, mastering the technique needs practice and the process of smartphone imaging of the retina becomes routine with time. Once mastered and if performed properly, retina images can be acquired in three to five minutes. Of course, this doesn't include the time for pupil dilation.
Before attempting this procedure, it's important to remember to allow the patient's pupil to dilate completely and to remove all smudges and blemishes from the handheld lens. Following this procedure, other imaging modalities like fluorescein angiography or OCT scans can performed to answer additional questions about retinal and optic neuropath. After watching this video, you should have a better understanding of how to use a smartphone camera and a handheld ophthalmoscopy lens to obtain retinal images in different settings.
Encourage patients to maintain a steady view of a target. This helps in the acquisition of a clear retinal image.
