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10 Sep 2017

Using the GoPro on the Slit Lamp

The slit lamp enables a well-illuminated and magnified view of the eye.  There have been previous imaging devices used for recording, however the quality of the stills and video is limited by cost.  We present a relatively lower cost solution for the Haag-Streit slit lamp (Haag Streit AG, Switzerland) using a high definition camera, Hero5 Black (GoPro Inc., USA).  The disadvantage of the standard Hero5 Black, is the inability to fit or change lenses as it does not come with a lens mounting thread.  A third-party company, Back-Bone Inc. (Ottawa, Canada) modifies the Hero5 Black so that the front of the camera is removed and replaced with their own-designed camera face.  The original GoPro lens is removed, creating a camera body (no internal focusing mechanism) that can fit other camera lenses and mounts (Figure Thumbnail A)

The Hero5 Black is a high definition camera used popularly for recording of action (Table 1).  It has major advantages with resolution up to 4K (3840 x 2160) video (MP4), 12MP photo (JPG or RAW), a frame rate of up to 120 fps in 1080K resolution, stereo audio, CMOS chip (1/2.3”), wireless connection vis locally created wi-fi network enabling it to be displayed on an iPhone or iPad device (Apple Inc., USA).  Another useful feature is voice activation, with commands to start and stop video recording, taking a photo and turning the camera off.  This is important as often both hands are occupied holding the patient’s eyelids and focusing the slit lamp.  The GoPro application on the iPhone also enables wireless control and review of the captured images and video.  The camera can run on rechargeable batteries or an AC adapter.  In order to mount to a Haag-Streit slit lamp, a beam splitter 70/30 (HS art. no. 1001395) is placed in the stereo microscope eyepiece pathway and a video adapter with lens tube f75 (C-mount) (HS art. No. 1400319) (Figure Thumbnail 1B) attached to the beam splitter (Figure Thumbnail 1C) to enable the modified Hero5 GoPro body to be connected directly onto the C-mount.  The images can be reviewed on the 2” touch LED display but unfortunately the screen is not at an easily viewed angle when mounted to the slit lamp (Figure Thumbnail 1D) and is too small to demonstrate to patients.  It is a major advantage as the camera is compact without any hindrance from wires that could interfere with slit lamp function.  The setup to take a photo is quick and discreet, so does not detract from the routine clinical slit lamp examination.  The Haag-Streit slit lamp can be fitted with an LED illumination with background illumination and cobalt blue filter, otherwise an additional external light source for diffuse illumination is required, provided by a cold fibre optic or mounted LED.