To overcome the inconvenience and imprecision of conventional software performing micro-perimetry with the Scanning Laser Ophthalmoscope (SLO) in clinical settings. In addition, it was the goal to make micro-perimetry independent of the examiner’s skill in placing a stimulus on a moving image.
SMP takes advantage of modern computer technology, especially processing speed and high rate of data transfer. It allows continuous on-line processing of the image of the retina and instantaneous correction of stimulus placement according to involuntary eye movements with a minimal delay. Stimuli are here placed on a static image of the retina, and the software then searches where that location is in the moving image to place the stimuus there. Thus, the program provides gaze-contingent display of the stimulus and senses the conditions for image tracking, so that stimulation during large eye movements, blinks and temporarily flawed image quality are prevented.
Special features and results:
• Using SMP in contrast to an old “scotometry” program makes the measurements faster by almost 40%.
• Since SMP using a pre-designed grid does not require the examiner’s interference, we tested its benefits for overall test duration. SMP in the fixed grid mode takes only half the time compared with “scotometry”.
• Every collected set of coordinates and the elapsed time (in milliseconds) during stimulation were written into an array. Microsecond accuracy was guaranteed by reading a 64-bit counter that is independent of the CPU. Later inspection shows that no frame was missed and a set of consistent coordinates was produced.
• SMP can produce different targets, which allows the inclusion of psychophysically different modes of perception like recognition or discrimination. This increases the demand on the patient’s performance and, thus, is a more sensitive test for the functional state of the patient’s visual system.
• SMP has a mode called “automatic re-trial” that allows placing a target even while tracking the image of the retina is not possible. It works like the “auto-redial” mode in a fax machine. This feature automatically retries the selected location when image tracking is found to be good again.
• Fixed grids can be accommodated through the automatic placement of stimuli (see above). Standard test grids can be chosen from a menu, so that testing can begin after a single mouse click and without further involvement of the examiner.
• Much information can be gained from monitoring how special tasks like pursuing a smoothly moving target or reading a line of text are solved. These “movies” can be stored and played back later for analysis or teaching purposes.
• SMP software allows digital sound recording to secure the accuracy of patient responses where it counts. , e.g. if a discrimination task is used, the patient’s voice during the test can be recorded digitally in parallel to any test session.
To buy the Smart Micro-Perimetry (SMP) system, you need to know this:
Note that you need to have a Rodenstock Model 101 Scanning Laser Ophthalmoscope (SLO).
The SMP system consists of a hardware and a software component.
The hardware includes a PC with Matrox frame-grabber card, a scan converter and a gain adjustment box. The exact composition will vary according to your needs.
Added to this is our proprietary SMP software.
Depending on the software package you choose, the overall price varies (up to now only for NTSC video standard):
1. The basic clinical package (micro-perimetry only)
Price: Depending on market conditions re. the purchase of specific hardware, the price currently ends up at about $8,000.00 (US Dollars)
2. The advanced package (SMP, plus several extensions for recording live “movies” of eye movement episodes plus special software for eye movement analysis)
Price: Depending on market conditions re. the purchase of specific hardware, the price currently ends up at about $9,000.00 (US Dollars)
Payment: By bank check, money order, or by direct transfer to the MMTest bank account.
The SMP hardware will be delivered by mail with all software installed.
MacKeben M. & Gofen A. (2007) Gaze-contingent display for retinal function testing by scanning laser ophthalmoscope. J Opt Soc America A, vol. 24/5, pp. 1402-1410 (feature issue on “Retinal Imaging”) [PDF]