Replacing the Slit Lamp with a Mobile Multi-Output Projector Device for Anterior Segment Imaging

June 1, 2015

Shantanu Sinha, Nickolaos Savidis, Everett Lawson, Ramesh Raskar; Replacing the Slit Lamp with a Mobile Multi-Output Projector Device for Anterior Segment Imaging. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3162.


Purpose: The gold standard for examining the anterior segment of the eye is the ophthalmic slit lamp. Slit lamps are bulky, contain many moving parts, require trained physicians to operate and cause discomfort due to light sensitivity. We demonstrate an experimental solid-state computational platform employing light steering techniques to project a synthetically generated slit of light onto the eye that provides functionality similar to that of a slit lamp. This low-cost, portable device reduces the examination time from the order of a few minutes to about five seconds.

Methods: The compact system consists of three modules: a pico projector, a standard RGB camera and simplified optics. The pico projector outputs a computationally generated slit of light - a vertical line in the frame of the projector. A pair of lenses collimate and focus this slit onto the subject’s eye. Thus, as this line is translated in the frame of the projector, an arc is observed on the surface of the eye, with the virtual axis of rotation passing through the subject’s eye, as is the case in a conventional slit lamp. Employing a beam splitter, the 60 fps RGB camera is placed on the optical axis to image the anterior chamber in high definition. The captured data is transferred to a computer, where it is analyzed by an ophthalmologist after the actual exam.

Results: The device is compact and portable - fits in a 120 mm long and 60 mm wide area. Our prototype exhibits a similar functionality to that of an ophthalmic slit lamp with an 80 degree field of view. The nature of the device allows to project any computationally generated pattern onto the eye and is not limited to a vertical slit pattern. The high frame rate of the capture sequence allows for the entire examination to be performed in under 5 seconds, as compared to a conventional slit lamp exam which takes a few minutes.

Conclusions: We have proposed a prototype device for imaging the anterior segment of the eye that has no moving parts, can be operated by less skilled technicians and has a form-factor that enables the device to be molded into a handheld/wearable device. Ease of use and low hardware complexity facilitates use of the device in low-income societies and in parts of the world with poor access to highly skilled ophthalmologists. The low examination time would greatly reduce eye pain associated with light sensitivity, as compared to a conventional slit lamp exam.

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