Research Projects in Vision and Ophthalmology
Click here for the List
of Patents and Publications
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Portfolio of the medical devices
Automatic eyedroplet dispenser
Patients
having dry eyes experience much pain and may eventually go blind. It is
estimated that between 9 to 15 million Americans
suffer from this disease. Currently, therapy is tedious and costly. We have
developed a new instrument, mounted on a patient's eyeglass frame, which
automatically ejects droplets at an adjustable pace into the patient's eyes.
The functions of the device are monitored by a built-in microcontroller which
is battery powered. The efficiency of this device and the study of new
therapeutic methods are in progress.
Automatic eyedroplet
dispenser designed by Professor Vo Van Toi and commercialized
by the Technological Ophthalmic Instruments Inc.
Inside view of the
Automatic eyedroplet dispenser. The microcomputer monitors the device functions in
programmable, automatic or manual mode.
Noninvasive method to
evaluate visual fatigue
Workers who use video display units (VDU)
often experience visual fatigue. How to quantify visual fatigue is still a
controversial topic. It is known that the technique of measuring the
sensitivity of the eyes using sinusoidal waveform flickering light is a
powerful tool for evaluating human visual function. Currently, we are designing
a new and practical visual stimulator, to be made commercially available, using
the delta modulation method and single chip microcomputer. Experiments are
planned using this instrument to establish the visual functions of VDU users to
test for visual fatigue.
It was reported that blinking is associated
with the state of the eye as well as the state of the mind. We have developed a
portable device which automatically records the blink rate in a non-invasive
way and without coming in contact with the subject eyes, obstructing the
subject’s view, or interfering with the subject’s activities. The
device is self-contained and battery powered and consists of an infrared sensor
mounted on an eyeglass frame. Data are recorded for up to 24 hours and then
down loaded into a personal computer, and processed for further analysis or
plotting. This device is an important tool for our research on the relationship
between blinking and visual fatigue, dry eye, and the mechanism of blinking.
This is a prototype of the Blink Rate
Recorder. It records the blink rate in a non-invasive way and without coming in
contact with the subject eyes, obstructing the subject’s view, or
interfering with the subject’s activities.
A chart generated by our Blink Rate
Recorder which indicates the blink rate fluctuation of a subject while he was not
using the computer (from 0 to 60 minutes) and while he was using it (from 60 to
120 minutes). The average blink rate when using a computer was considerably
reduced.
Relieving visual fatigue of visual-display-terminal operators
Studies have shown that VDT operators blink
three times less frequently than non-VDT operators, therefore they may
experience dry eyes which results in visual fatigue. We hypothesize that: (1)
the reduction of visual fatigue will improve the VDT operators’ comfort,
(2) visual fatigue conditions can be monitored and measured, and (3) visual
fatigue is produced by eye dryness which may be relieved by administering eye
drops or by increasing the blinking rate. The proposed techniques consist of
stimulating, in a non-invasive way, the blinking rate of VDT users and of
supplying additional tears to their eyes automatically. This work could have a
significant impact on people who are engaged in various professions involving
repetitive eye strain, for instance, air traffic controllers. It should benefit
the search for an adequate working environment and provide methods for a better
understanding of the visual fatigue mechanism.
Using a computer for long hours may cause
visual fatigue. To test our new way to relieve this visual impairment, Biology
student Xuan Mai Vo, wears
our Blink Rate Recorder to monitor the blinking and used the Automatic Eyedrop Dispenser to constantly keep her eyes moist.
Psychophysical method
for measuring retinal blood flow
Looking at a bright, homogeneous blue field
one can perceive the white blood cells (leukocytes) moving in one's own retinal
vessels. This is known as the blue-field entoptic
phenomenon. Knowing the density and speed of these leukocytes, one can
investigate, in vivo, the subject's retinal blood flow and therefore may be
able to develop a diagnostic method for glaucoma, ocular hypertension and
diabetes. We have successfully developed a method to measure these
characteristics in a reliable way. We also have developed a portable and
efficient entoptoscope using a single chip
microcomputer and electro-optic materials such as LCD and PLZT. A laptop
computer can be used to monitor this instrument and process the obtained
experimental data. This device also allows measuring the size of the fovea avascular zone, the area on the retina which contains no
blood vessels.
We have developed the blue-field entoptoscope which allows for in vivo and non-invasive
measurements of the retinal blood flow in the human eye. It can also be used to
measure the size of the fovea avascular zone. A
laptop computer can be used to monitor this device and the experimental
protocols and to process the obtained data. This device is used to investigate
eye diseases such as glaucoma and diabetic retinopathy.
Laser Doppler technique for measuring eye fundus
blood flow
A direct and objective method of measuring
the retinal blood flow is based on the Doppler technique which consists of
passing a laser beam into the subject's eye, targeting it on moving red blood
cells inside a retinal blood vessel and recording the scattered light emitted
from the eye. Measurements on animals have been successful. We are developing a
device using an eye-tracker to compensate eye motions. This device will be
useful for the study of human fundus blood flow.
Perception of
raggedness of dot-matrix characters
The raggedness of characters or patterns
formed by dot matrix printing techniques is unaesthetic and sometimes
disturbing to the reader. Optimization of the number of dots is still a subject
of discussion due to a fundamental lack of comprehension on the part of the
designer concerning human visual perception of this kind of stimulus. Using the
concept of Fourier analysis, we are simulating the scalloped edge of the
characters as a patterned stimulus modulated sinusoidally
in an attempt to relate this problem to the human eye's sinusoidal vernier acuity. This investigation is important to the
designers of characters that are generated by ink jet, laser, and needle
printers.
High rate pattern visual stimulator
The pattern visual stimulation technique is a
common tool used by physiologists, biologists, psychologists and
ophthalmologists in the investigation of the human visual system. A great
number of investigations that are devoted to stimulation at a low rate have
been reported. We designed an electro-mechanical visual stimulator to generate
pattern stimuli which was modulated up to 220 reversals/sec.
and found that human pattern reversal VEPs are not,
as previously thought, limited to low frequencies. These results open the door
to other physiological and clinical investigations.
Miniature eyedrop monitor
Success in the development of new drugs for
the treatment of glaucoma, ocular hypertension and eye infections requires
investigators to know how patients use them. We are developing a prototype
which records the time and date when a patient inserts the prescribed eyedrops. The data can be later read by a computer.
Artificial increase of intraocular pressure
Glaucoma and ocular hypertension are the two
most severe eye diseases. Glaucoma is the leading cause of blindness in the
Effect of LSD on
flicker-fusion sensitivities
LSD and similar agents may alter visual perceptions
continuously and permanently in certain users resulting in a condition called
hallucinogen persisting perceptual disorder (HPPD). We have found that the
flicker sensitivities at lower frequencies vary markedly. At 5 Hz the
sensitivities of a control group were more than 3 times those of LSD subjects
without HPPD, and 5 times those of LSD subjects with HPPD. Decreased
sensitivity to flicker is consistent with the hypothesis that HPPD is
associated with disinhibition of visual information
processing.
Professor Vo Van
Toi helps monitor the use of his visual stimulator "Papillometer"
as graduate student Barbara Dumery tests her visual
flicker-fusion sensitivity.
Mathematical modeling of the human visual system responses to flicker
stimulation
The
main purpose of this project is to establish a mathematical model which relates
experimental data that we obtained in psychophysics, electrophysiology, and
laser fundus reflectometry
to physiological facts. This model would describe the mechanism of the human
color vision system.