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Digital Video Recorders and Eye Movements

How I do it.

Timothy C. Hain, MD Page last modified: June 27, 2019

Computers and multimedia have made a huge impact in the world at large, and also in the oculomotor laboratory. It is possible to use readily available equipment to record video eye movements and public domain "free" programs to create movies out of your recordings. Herein I have outlined the how to do this.

Hardware

You should expect to spend about $4000 on your entire setup, almost all of it on the Micromedical goggle.  See comments below about the lack of availability of the Micromedical device, and the attempts by others to develop a replacement. You should expect to spend several hours ordering these parts, and another hour to hook them all up.

Device

Cost (roughly)

Real-eyes goggle (Micromedical Tech) 2500 -- but now unavailable !
PIP processor (see below) -- these are needed but fortunately cheap. 150
Room CCTV camera, and mounting mechanism. Panasonic wv-bp144 and mount. Brand doesn't matter much -- but it is best to get one that adapts to light automatically. Don't forget to get cable (BNC), lens, and 12 volt power supply too. 200
Large monitor with Composite input (30" LCD) $400 (big is good).
EasyCAP USB capture device. $20
CE-labs audio and video amplifier, model 400 $40.

 

Micromedical Technology NTSC monocular eye movement recording apparatus . This device is no longer being made. Location of secondary camera -- a Panasonic security type camera. This is in the days that we were using a CRT. Now we use a flat screen.

Cameras

Video Input 1: I use a Micromedical Technology "Real-Eyes" system. This is a single camera set in a Scuba goggle. It is monocular, with a normal, "NTC" video output. It is best to have several "spare" cameras, goggles, and powersupplies, as these things all break from time to time. Sadly, and recently, this device has become unobtainable as the maker (Micromedical) has discontinued composite (NTSC) cameras. We haven't figured out how to deal with this. Stay tuned to this page, as eventually we will find some way to get similar results from competing hardware. We are aware of several groups developing similar technology, and eventually they will take over sales for this very useful device that Micromedical has "left on the table". The price for the lower quality devices in development is generally about $1000. These are not quite the same, and be careful. One, for example, is being developed by "vestibular first". We have encountered other devices from France, Argentina, and Japan. Generally speaking, from what we have been able to determine, these devices do not work as well as the Micromedical system (that is no longer sold !). A common flaw for these competing devices is the lack of a focusing mechanism. Another common flaw is the lack of an ability to allow one eye to see while the other is being recorded.

Getting back to the Micromedical camera, the other eye can be allowed to view or not, as the examiner desires. This is a good situation. See this page for more comments.

Video input 2: The current video camera for the room that we use is a LX-620SHW High Resolution Sony CCD CCTV Security Camera - 1/3 540 Lines. (see above). These are pretty cheap, and they put out NTSC (which you need for the PIP). The idea is that you can identify your patient as well as see what you are doing with a room camera. These cameras run 24/7, and burn out every few years. Good idea to have a spare one.

The camera must be mounted and angled properly -- Amazon as well as many camera stores sell appropriate devices for between $20 and $30.  We like the system of putting the camera on an IV pole so it goes up and down, and using a universal mount that allows it to be positioned. These are basically cheap. Sometimes the IV pole is used to hold other parts (like the PIP device and the distribution amplifier). The electronic music industry has pole shelves that work here.

Monitor with PIP

Electrically,  the way this works is that the two cameras go to the PIP. The PIP goes to the distribution amplifier, and one output of the amplifier goes to the EasyCap, while the other goes to the local Eye display. The EasyCap saves the mpeg file to the computer. Typically each patient consumes about 5 minutes of the video.

PIP

PIP (picture in picture) processor

We currently use the AMBERY 4 channel PIP processor (costs about $150) . The PIP box combines video from another camera that views the room, so that there is an inset on the eye, showing both the examiner and examinee. This makes the entire editing process much easier. Generally about all you can tell from the PIP is the gender of the patient, their hair color, and what is being done. This is a good situation. These inexpensive Chinese boxes fall apart every year or two, and it is crucial to have another one. Usually the BNC plugs in the back fall off.

The PIP device also puts up a date/time stamp, which can help keeping track of what the video is all about.

Amplifier

Amplifier

The output of the PIP processor goes into a distribution amplifier (especially helpful if the cable run is long), and one of the outputs goes to the display, while the other goes to your computer (the EasyCap). These cost about $40. I think it is best to always use these, as it isolates your monitor from your EasyCap. These amplifiers never break.

EasyCap

EasyCap

The EasyCap is an amazing Chinese device that converts a composite input with sound into an mpeg4 file. The best setting is the "DVD" one, with 8K bandwidth. This produces a file of about 1gig/5 min. As these can build up, it is best to "sweep" them to a bigger storage device. These gadgets cost only about $15 on Amazon. These inexpensive Chinese gadgets fall apart roughly every year (literally), and it is a good idea to have a spare or two. What happens here is that the plastic case falls apart - -maybe the glue degrades.

The EasyCap software nearly always works, even on the ever changing Windows-10, but we were unable to get it to work on a "Dual Xeon" PC. It works on a single Xeon PC however.

Optional stuff

If you have the extra parts and cables, you can also set it up so that you also send the eye camera to the monitor 2nd input, so when you record you just see the eye, but when you play back, you see eye and what you were doing in the inset. However, we think it is generally a good idea to see the PIP, as sometimes it gets repositioned and then you have no idea that you are recording empty space.

 

Editing; the method of preparing teaching videos of nystagmus using mpeg files.

So now we have an MPEG file, typically about 500K long. There are two editing programs that I use next, should I want to use this video for a presentation. The main goals are to chop out useless stuff, and secondary, to make the video show the eye only, without any identifying information about the subject.

mpeg_stream

This program is very good at trimming off stuff from the beginning or end -- a good first step is to just select out what you want. This program does not reduce quality -- it just snips stuff out. It is open source, so it is free.

Cyberlink

This commercial video program (which costs about $150), is good enough to do some more subtle things, like adding titles, cropping videos, and putting "masks" over sensitive places. Usually I end up putting on a title and sometimes cropping off the date stamp at the top, and possibly the PIP portion of the picture. This program is not so easy -- while pretty capable, there is no book (probably because it is constantly changing), and also some of the tasks are very hard (such as masking off the PIP portion). Perhaps more expensive programs work better, but this one is a pretty good compromise between cost and function.

Cyberlink also defaults to output settings that are "fast and loose" -- usually unusable quality for eye videos. One has to make a custom very high quality output, to avoid the program smushing together frames or making the whole thing into a big blur.

 

 

 

 


Copyright June 27, 2019 , Timothy C. Hain, M.D. All rights reserved. Last saved on June 27, 2019