Page 7 - BOAF Journal 1 2012:2707

Behavioral Optometry
BOAF
Volume1 Number1 2012
quent, and for the first time in his life he could walk down the road without bumping into things. Three years later, this prescription was still stable and successful.
Let us now consider what was happening.
If prism base right were supplied, the effect on the eyes when “looking” directly ahead would be as follows:
This individual’s perception of his primary position is offset to his left. Therefore without this optical prism correction, this individual will believe they are positioned correctly ahead only when their “visual” system is slightly twisted to the right.
In compensating for this, the body may twist the whole spinal alignment including the shoulders and hips.
The effect of this is to cause scolliosis of the spine, mis- alignment of the hips and a twisted walk causing strain and “wear” in the leg and hip joints. He may misjudge his position in relation to other visually ob- served objects causing him to appear clumsy and bumping into things – no wonder he en- dured regular visits to his Chi- ropractor.
Several years later I met Florida Optometrist Dr Wayne
Pharr OD2, who described this
condition as “Visual Mid line shift syndrome”
Assessment of this condi- tion as demonstrated by Dr Padula3 is as follows:
1) Ask the patient to stand with his head in its normal “straight ahead” position. The optometrist should stand in front and to the side of the patient. Holding an eye track- ing target such as a Wolff wand or Budgie stick, the optometrist should bring the target in slowly from the side asking the patient to advise when he feels that the target
is directly in front of his eyes. Note actual position in rela- tion to centre of face. Repeat from the other side, from above and from below. It should be easily apparent to the Optometrist if a miscon- ceived perception of direc- tional space is present. Ap- propriate yoked prisms can be introduced to obtain cor- rect alignment.
2) Large yoked prisms in the order of 16 PD can be worn with prism bases both
base right and observe the patient’s attempt to walk a straight line. (Patients suffer- ing form balance problems following mild closed head brain trauma may need to be assessed very small yoked prism from 1⁄2 PD upwards.) Repeat with both base left and repeat. The prism direc- tion that provides the least difficulty in walking is the di- rection in which prisms should be supplied. I would normally prescribe an initial 1PD in addition to their nor- mal refractive result. Increase prism if resultant change in- sufficient. Fresnel prism could be useful in a trial situation before the end re- sult lens supplied. This tech- nique only looks at lateral prism corrections as these are most likely to lead to sco- liosis problems. In some pa- tients with head trauma, trial with very small yoked prism (or base in prism) to identify best correction (large prism may make them totally lose their balance)
2) The effect of a small vertical ocular muscle imbal- ance on the physical structure of the body
Let us consider a situation where an individual has a small right hyperphoria. In this exam- ple, we will consider that there are no apparent ocular symp- toms of visual strain or diplopia. However, for the body to be 100% comfortable, this vertical imbalance needs to be ad- dressed.
-7-