Page 23 - BOAF Journal 1 2012:2707

Behavioral Optometry
BOAF
Volume1 Number1 2012
9. It is recommended that the illumination lights of the Cae- canometer be turned to MED for most chartings if visual acuity is somewhat near normal. For draining focal infection chartings on sub- normal vision cases, the illu- mination lights can be turned to HI if necessary and the fixation peep sight tubes can be removed by unscrew- ing by hand so that the pa- tient has the entire neon glow lamp as the fixation light. For pathology chartings, always use LO illumination when possible. At this point, turn the illumination lights of the Caecanometer to the correct setting.
Charting procedure
The patient should be in- formed that you are running an extremely sensitive test and that the results and the time neces- sary to obtain those results are dependent upon their ability to maintain constant, unchanging fixation on the yellow light. Davidsen has pointed out that concentration on the task is so important that the patient should be instructed to keep their eye and mind fixed on yel- low light trying to think of noth- ing else and that if their eye or mind should wander, that you can tell it. This reassurance to the patient relieves him/her of worrying about making an error.
Continue in your instruction to the patient by saying, „Keep- ing your eye on the yellow light, are you aware of this little silver
ball out of the corner of your eye?“ This step is facilitated by pointing to the test object with your pencil or moving it a bit with the magnet. By using the phrase „out of the corner of your eye“, the patient recog- nizes that he/she is not to look directly at the test object and this further removes him from the conflict of looking at the yellow light and the test object at the same time.
Some will even express the de- sire to look around the face shield of the Caecanometer di- rectly at the test object. This acquaints them with the test object, satisfies their curiosity, and removes what might be a hindrance to concentration. It is sometimes helpful in securing a child‘s cooperation to let them move the test object a bit them- selves.
When the patient has con- firmed that he is aware of the test object and is maintaining fixation on the yellow light, con- tinue by saying, „I‘m going to make the silver ball disappear. Just as soon as it does, you say ,now‘.“ When this last instruc- tion is given the patient, vocal emphasis must be placed on the words ,soon‘ and ,now‘.
The test object is now moved at the approximate rate of one-fourth inch or eight mil- limeters per three seconds to- ward the location of the nerve- head. Speed of movement does not seem to be as critical as might be supposed. However, the important points about rate of movement are -- slowly, but not so slow that the patient has difficulty maintaining fixation as fatigue can set in. Fixation and concentration are sometimes quite tiring especially for the patient with focal infection. Keep the rate of movement constant. A very important point to be remembered in cae- canometry charting is that the test object is moved in a straight line from seeing to non -seeing with a smooth even
Changing illumination
Target & tube of fixation
If the patient expresses curiosity about the test object, have him/her look directly at it before beginning the charting.
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