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NTU RDS stands for National Taiwan University Random Dot Stereograms. A good tool for both
clinical use and preschool screening purpose.
Random-dot stereogram was invented by Dr. Bela Julesz in 1960. Although the random dot
pattern doesn¡¦t mimic what we see in daily life, 40-year experience told us that random
dot stereopsis is well correlated with strabismus and amblyopia.
This is TNO stereotests. From Netherland. There are 3 33-minute-are pages for screening,
equivalent to about 2000 second-arc. There are also quantitative measures, from 480 to
15 sec-arc of stereopsis. TNO uses red/green goggles, anaglyphical binocular dissociation.
Randot E by Dr. Reinecke. Using polaroid goggles for binocular dissociation. Mainly for screening
use.
Lang stereotest. Applying multiple prism bars to separate the two half-stereograms for right
and left eyes. What¡¦s good here is that it doesn¡¦t need goggles and therefore more
suitable for young kids. Monocular cue is nevertheless its drawback.
Frisby stereotest. A real 3D stereotest. No need goggles. Have to keep steady to avoid
monocular cues.
Random-dot stereograms developed by Dr. Shao-Ming Yan of Navy General Hospital of Beijing. Very
popular in mainland China.
New version of Dr. Shao-Ming Yan¡¦s stereograms.
De Ka stereotest, made of prism bars.
Random-dot stereo butterfly.
Randot stereotests.
Here comes our NTU RDS. It is made of 10 6-inch by 4-inch photographs, laminated into 5 cards.
4 simple geographic shapes are hidden inside the random-dot stereograms. The answers are
right on the back of each stereogram. The other card has all 4 shapes, is designed for
very young kids to point out what he or she sees on the stereogram.
The photographs were of digital printing by Kodak store. The colors were adjusted to best
fit the requirement of red/blue separation of anaglyph presentation..
Through red blue goggles, a geographic shape looks jumping out of the plane. At 35cm test
distance, it presents 300 sec-arc stereopsis. The testable age, from our experience, is
about 3 year-old.
One of the stereograms.
The answer on the back of the stereogram.
It could be used in th preschool screening.
Dr. *** did screening at the kindergarten.
Dr. Lin did screening at rural kindergarten.
It requires 5 consecutive correct answers to pass the test. We shuffled before each
test to ensure tow things, (1) double blind test for bith the examiners and the examinees
and (2) There is only 1/4 chance of answering correctly by guessing.
This is the personal computer version of NTU random-dot stereograms.
In our pediatric ophthalmology clinic, a computer is set beside the kid for stereopsis test.
Dr. *** was explaining how a vague shape was floating out of the screen.
In clinical use, we repeated the test as many times as to be sure he could or could not
see the 3d stereo image.
The PC version can also be used for screening work at kindergarten.
Finally we had set up the web version of NTU random-dot stereograms. This might even wider
spread the screening work. Interested parents may test their kids at home, at an age as
young as 2 and half to three year-old.
From 1990 to 1994, a pilot study of visual screening among preschool children in Taiwan
was performed by National Taiwan University Hospital.
Briefly, the results of the study were Random-dot stereogram was good in screening
small angle esotropia. Random-dot stereogram was better than visual
acuity test in screening intermittent esotropia and hypertropia.
Visual acuity test was better in screening refractive amblyopia.
Random-dot stereogram was better than contour stereogram for screening purpose.
Both visual acuity and random-dot stereogram were not effective in screening intermittent
exotropia. NTU was as effective as TNO.
Combined distance visual acuity and NTU random-dot stereopsis test was adequate for preschool
screening. The testable age of NTU stereograms was about 3 year-old, even earlier than the
testable age of visual acuity.
According to the pilot study, the visual acuity criteria were set at 0.6 for 4 year-old; 0.7
for 5 year-old and 0.8 for 6 year-old.
Preschool visual screening at rural kindergarten. Screening distance visual acuity.
Screening 300 sec-arc NTU random-dot stereopsis.
As compared with TNO stereotest, NTU stereotest is as effective for screening purpose; its
cost is much lower; the random sequence after shuffling makes it impossible the memorize
the answer and it¡¦s a double-blind test.
Moreover, it¡¦s more attractive to the people being tested and the test procedure is easy
to learn for the examiner.
We all know that the random-dot stereopsis screening is not effective for ametropic amblyopia
and intermittent exotropia.
Since year 2000 we launched whole population mass screening for 5 year-old, totally more
than 300,000 kids. The work was mostly done by mid-level personnel, such as school teachers
and school nurses.
Hope you have enjoyed the journey with NTU random-dot stereopsis test. You may choose
among the card version, the PC version or the web version of this test, for both your
clinical work and mass screening mission.