Page 22 - BOAF Journal 1 2012:2707

Behavioral Optometry
BOAF
Volume1 Number1 2012
tending are contributors to re- peatability in plotting.
The chart should be placed on the instrument table by first placing the two holes in the chart over the two tubes or fixa- tion peep sights on the charting table and then smoothed gently towards the right and left edges and secured with the clips at each end of the charting table.
Chart #1 / Chart #CG
The doctor may use either the #1 Caecanometer chart which is dull black and is printed with a white ledger and faint grey expected nerve-head outline or the #CG Caecanome- ter chart which is dull black and has the white ledger with only a tiny grey dot in the center of the expected nerve-head but no nerve-head outline. there is a clear plastic guide sheet printed with the physiological nerve- head as a guide to the doctor for use with the #CG chart and also for demonstrating to the patient how their blind-spot compares to normal. Pads of white charts printed in black are for use in making referral copies only.
The printing on the chart ledger will be right side up to the doctor as he faces the Cae- canometer. If it is not placed on the instrument in this manner, the plotted nerve-head will ap- pear to be displaced as the fo- vea and blind-spot are not aligned with one another.
Careful adjustment of the instrument to the patient is a must. the Caecanometer must be adjusted so that the patient can view the fixation target light with no strain and hold the posi- tion until the necessary points have been plotted. An efficient procedure of adjusting the in- strument to the patient is as follows:
1. Set the height of the table on which the Caecanometer is placed so that the patient can place their arms on the table and steady themselves.
2. Set the height of the Cae- canometer by using the ad- justable raising and lowering knob so that the patient has their forehead resting gently against the forehead rest of the instrument and is aligned with the lenses.
3. Adjust the chin rest on those Caecanometers which em- ploy this feature.
4. Turn off all room lights and the illumination lights of the Caecanometer leaving only the fixation lights of the in- strument turned on.
5. Point out with a pencil the fixation tube, the hole in its end and the yellow light which can be seen by looking into the hole.
6. Have the patient move their head from side to side and up and down never losing contact with the forehead rest until the light fills the fixation tube and is the brightest obtainable. the pa- tient is then instructed to maintain this position. It must be remembered that the out- standing factor in the suc- cessful use of the Cae- canometer is the ability of the doctor to insist upon and obtain precise and constant foveal fixation by the patient during the time the nerve- head is being charted.
7. Quickly check to see that the patient is sitting easily and with maximum comfort and not stretching or slumping in order to view the fixation light.
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Jointed excursion arm
8. Place the test object on the charting table of the Cae- canometer on the nasal side of the nerve-head location. The movement of the test object is controlled by a spring-loaded magnet on a jointed excursion arm from beneath the chart table.