Here is our young patient with her head posture under normal viewing conditions.
And here is the head posture she adopts as we ask her to read the Snellen Eye Chart.
It has nothing to do with non-comitant strabismus or double vision. She has good binocular vision with her head straight. Nor is she experiencing ptosis or droopy eye lids, which might otherwise necessitate her to lift her chin to get a clearer view if she’s unable to elevate her eye lids.
Our young patient underwent vision therapy with us last year and her myopic progression stabilized. I wrote her an Rx last year with a bifocal component which she wore for several months until her frame broke and she went elsewhere for her “insurance covered eye exam”. They increased her nearsighted distance lens power by a small amount, and omitted the bifocal. In the ensuing couple of months her myopia had begun to accelerate again.
Patients with myopia learn that they can either tilt their frames forward to bring the edge of the lens closer to the center of their eye, thereby increasing the effective minus power they’re looking through, or tilt their chin upward to achieve the same effect. In addition, looking through the lower edge of a pair of minus lenses induces a yoked prism effect.
Interestingly, although the effect of a bifocal or progressive addition lens is often viewed through it’s relative plus lens properties, it also has the effect of counteracting what our patient above can do with her single vision lenses in inducing more minus lens effect. If she tilts her chin up through a multifocal, distance vision becomes blurrier instead of sharper. Probably another reason why clinicians observe that multifocals can help stabilize myopia.