Smartphones are now used as Opthalmoscopes to record the image of the eye at ease. An Ophthalmoscope is used by a health professional to see inside the fundus of the eye and other structures. But they are not easy to use.
Dr. Andrea Russo, an ophthalmologist, devised the D-EYE, a smartphone lens attachment that turns a variety of smartphones into digital ophthalmoscopes. Light comes from the smartphone's LED, off-axis from the camera lens. A path of light from this LED delivers the light exactly coaxial to the camera using a combination of levers and beam splitters.
It gives a better visual of the pupil and eye. Once you see the red reflex from the eye, the D-EYE is correctly focused. You can increase the field of view by moving the phone/D-EYE closer to the eye, without changing the focus.
Using the smartphone's auto focusing capabilities, refractive errors can be corrected to compensate between -10D myopia to +10D hyperopia. Even with undilated pupils, it's possible to scan the retina with a field of view of 5-8 degrees.
Optic disc with pupils as small as 2mm, can be viewed so the D-EYE can offer a rapid screening for glaucoma or hypertensive retinopathy for undilated pupils.