|
|
School Health-Product Education- PhotoScreener Protocol
| |
 |
| PhotoScreener™
Protocol (as suggested by MTI) |
What
is the PhotoScreener™ and what does it test?
The MTI PhotoScreener™
is an instant film camera designed to document the light reflexes that are
emitted from the eye. The camera was developed as a screening tool for the
detection of amblyogenic factors such as an eye misalignment, media opacities,
and the presence of refractive errors such as nearsightedness, farsightedness,
anisometropia (a difference in focusing power between the two eyes) and
astigmatism.
The MTI places
a flash source adjacent to the camera's lens. This type of system is referred
to as off axis or eccentric photorefraction. The MTI uses high-speed black
and white instant film (Polaroid 667), is portable and non-invasive.
|
|
Suggested Items Needed to Do the Test:
| 1. |
MTI PhotoScreener™
|
| 2. |
MTI PhotoScreener™
power cord.
|
| 3. |
Film (Polaroid
667).
|
| 4. |
Measurement tool.
|
| 5. |
Labels with the
child's name and ID number to attach to the back of the photograph.
|
| 6. |
A 3 prong extension
cord (if the PhotoScreener™ power cord is not long enough to
reach the electrical outlet).
|
| 7. |
A stapler for
attaching photograph to data form.
|
| 8. |
A dimly lit room.
|
| 9. |
Tripp Trapp chair
for the child; stool for the photographer positioned 3 feet from each
other.
|
| 10. |
Black cloth to
hang on wall behind child's head during testing.
|
| 11. |
Small desk or
table for photo processing (readability evaluation and photo attachment).
|
| 12. |
Small lap table
to support PhotoScreener™.
|
| 13. |
Pen light for
photo processing.
|
| 14. |
30-second timer.
|
Setup for PhotoScreening:
| 1. |
Check the PhotoScreener™
battery charge prior to each screening session by turning the camera
on and making sure the low battery light does not come on. Do not
charge the battery unless the low battery light is on. If the low
battery light does appear, follow these steps to recharge the battery:
a. Plug the AC/DC adapter cable
into the camera's left side jack and to an electrical outlet.
b. The camera can now be left
to charge for 14-16 hours or can be operated in the normal manner
off the AC power. If the camera is operated during the charge, this
time period is part of the 14-16 hour total charge.
c. Leaving the battery to continuously
charge, or re-charging the battery when the low battery light is not
on, will decrease the life of the battery.
|
| 2. |
Place two chairs
approximately three feet across from each other. The child will sit
in the Tripp Trapp chair and the photographer will sit in the other
chair. The child should be photographed against a black background.
(Do not place the child's chair directly up against a light colored
wall because the bright flash bouncing off of the wall may affect
the quality of the image. Similarly, do not take a picture over a
table, which could also affect the quality of the image.)
|
| 3. |
Load the film
into the PhotoScreener™ by turning the camera over with the
left side down. Open the film-back by pulling out on the bottom
of the door latch. The film door will swing down out of the top
part of the film-back. Remove the empty film case by pulling out
and down on the white, foam backed tab. Place new film into the
top part of the film-back with the black, protective cover tab facing
out. The black tab of the film safety cover should extend through
the door latch. Check to be sure that the smaller white tabs are
not tucked under the pack. Close the film door and press the door
latch into the locked position. Pull the black tab of the safety
cover all the way out of the film-back and discard it.
|
| 4. |
Do not plug the
PhotoScreener™ in unless the low battery light is on. Place the
PhotoScreener™ on the countertop or table next to the photographer's
chair. Put the marker and stapler next to the recording station.
|
How to Do the Test:
| 1. |
Turn the camera
on by pressing the on/aim (left side) button for one second. |
| 2. |
Have the child
sit in the Tripp Trapp chair away from distractions.
|
| 3. |
Position the
black cloth behind the child's head.
|
| 4. |
Sit approximately
1 m (39 in) from the child, place the camera on your lap table, and
aim the camera toward the child, with the camera lens at the child's
eye level. There is no through-the-lens focusing.
|
| 5. |
Turn on the white
aiming lights by pressing the on/aim button again.
|
| 6. |
Line up the focus
lights >< in the middle of the child's forehead, just above
but not touching the child's eyebrows.
|
| 7. |
Tell the child
to look for the blinking red and green lights on the front of the
camera.
|
| 8. |
Press the fixation
button (upper left side). Do not talk to the child once the button
is pressed. The fixation lights are the stimulus that the child must
look at. If the child hears the photographer's voice, the child will
look at the photographer. The screening will not be valid if the child
looks anywhere but at the fixation lights.
|
| 9. |
If the photographer
has a difficult time getting the child's attention, the music button
can be pressed.
|
| 10. |
Immediately as
the child looks at the fixation light, press the flash button (lightening
bolt - upper right side) to take the picture.
|
| 11. |
Once the camera
lens rotates 90°, the camera will be ready to take the second
picture of the child.
|
| 12. |
Repeat steps
5-9 above for the second picture.
|
| 13. |
Remove the photo
from the camera by pulling the two tabs from the right side of the
camera. Begin by pulling the numbered tab and follow-up by pulling
the larger unnumbered tab. The second unnumbered tab will need to
be pulled parallel to the camera at a moderately slow and even pace.
|
| 14. |
Once the photo
has been pulled from the camera, start the 30-second timer. [At 75°,
picture will develop within 30 seconds from the time the photo is
pulled from the camera.
|
| 15. |
Place the child's
identifying label on the back of the photograph while you're waiting
for it to develop.
|
| 16. |
When the buzzer
sounds after 30 seconds, remove the protective casing from the photograph.
Separate the photo by peeling the large tab away from the front of
the photo.
|
| 17. |
Using a penlight
(if necessary to maintain a dimly lighted environment) and the pupil
calibrator, evaluate the photo from readability by checking for "the
4 F's": Four pupils, Four - Eight mm pupils, Focus, and Fixation.
If the photo is not readable, retake the two pictures for another
photograph. There must be a readable top picture (first picture taken)
and a readable bottom picture (second picture taken). You can achieve
this by obtaining a readable top and a readable bottom in different
photos.
a.
Four pupils: Each set of eyes must have two pupils showing.
The photo is still readable if 1/3 of a pupil is not showing. If
it is impossible to differentiate between the pupil and the iris,
the picture needs to be retaken.
b. Four-Eight mm pupils: Use
the pupil measurement tool to judge whether or not the pupil is
too small (less than 4 mm) or too large (more than 8 mm).
c. Focus: Similar to any photo
taken, if the picture is out of focus, it is not readable. Looking
at the eyelashes helps determine if the picture is in focus.
d. Fixation: Fixation is evident
by a small white dot appearing centered and slightly nasal in the
pupils. Fixation must be achieved in at least one eye in the top
picture and in at least one eye in the bottom picture. If fixation
is not achieved, the child was not looking at the fixation light
on the front of the camera.
|
| 18. |
If after three
pictures of the same child a readable top and a readable bottom are
not achieved, record the child as unable. |
| 19. |
Staple all photographs
for a child to that child's data form. |
What
You Tell the Child:
| 1. |
Tell the child
to sit in the Tripp Trapp chair.
|
| 2. |
Tell the child
that you are going to take two pictures of him/her with your special
camera.
|
| 3. |
Tell the child
to look at the red and green light on the camera and to open his/her
eyes and "look to see if a mouse/Barney is going to pop out
of the camera."
|
What
You Write Down:
| 1. |
Write down whether
you were able or unable to complete MTI Photoscreening.
|
| 2. |
Check the box
indicating how many photos were taken.
|
Remember:
| 1. |
Put the child's
identifying label on the photograph.
|
| 2. |
Line up the aiming
lights in the center of the child's forehead, slightly above the eyebrows.
Make sure the tips of the lights touch but don't cross over.
|
| 3. |
Be sure the child
is looking at the fixation light when you take the picture.
|
| 4. |
Retake unreadable
pictures.
|
| 5. |
AVOID SAYING
THE WORDS 'GOOD PHOTO' AND 'BAD PHOTO'! Well-meaning Head Start teachers
and/or parents may overhear the "diagnosis" from the photographer
and think the child has a vision problem. This information is sometimes
communicated very quickly to the parents.
|
References:
| i. |
Reinecke R:
Current concepts on ophthalmology: strabismus. N Engl J Med 1979;300:1139-1141.
|
| ii. |
Ehrlich MI, Reinecke
RD, Simons K: Preschool vision screening for amblyopia and strabismus:
programs, methods, guidelines. surv Ophthalmol 1983;28:145-163.
|
| iii. |
Atkinson J, Braddick
OJ, Durden K, et al: Screening for refractive errors in 6-9 month
old infants by photorefraction. Br J Ophthalmol 1984;68:105-112.
|
| iv. |
Day SH, Norcia
AM: Photographic detection of amblyogenic factors. Ophthalmology 1986;93:25-28.
|
| v. |
Kaakinen K, Kaseva
H, Krause ER: Mass screening of children for strabismus or ametropia
with two-flash photoskiascopy. Acta Ophthalmol 1986;64:105-110.
|
| vi. |
Freedman HL,
Preston KL: Polaroid photoscreening for amblyogenic factors. Ophthalmology
1992;99:1785-1795.
|
| vii. |
Preslan MW, Zimmerman
E: Photorefraction screening in premature infants. Ophthalmology 1993;100:762-768.
|
|
|
