Refraction and muscular imbalance, as simplified through the use of the ski-optometer

by Daniel Woolf

The Use of the Ski-optometer in Skioscopy

In skioscopy, the Ski-optometer offers the refractionist assistance of the most valuable character.

For example, assuming that extreme motion in the opposite direction with plane or concave mirror is obtained with a +1.25D. spherical lens before the patient’s eye; by quickly turning the Ski-optometer’s single reel until the two white zeros again appear, +2.50D is secured, as explained in the previous chapter. If this continues to give too much “against motion,” the lens power should be quickly increased to +3.75 or +5.00D if necessary ([Fig. 4]). Should the latter reveal a shadow in the reversed direction, the refractionist is assured that it is the weakest lens that will cause its neutralization. Practically but few lenses have been used to obtain the final result proving the instrument’s importance and time-saving value in skioscopy, and demonstrating the simplicity with which tedious transference of trial-case lenses is avoided.

Furthermore, it should be noted that where the Ski-optometer is used in skioscopy, it is not necessary to remove the retinoscope from the eye or to constantly locate a new reflex with each lens change. This permits a direct comparison of the final lens and eliminates the usual difficulty in mastering skioscopy. The chief cause of this difficulty is due to the fact that the transferring of the trial-case lenses makes it practically impossible for the student to determine whether the previous lens caused more “with” or “against” motion.

Fig. 9—The Woolf ophthalmic bracket. A convenient and portable accessory in skioscopy and muscle testing; can be used with or without Greek cross.

Where the indirect method is employed in skioscopy, best results are secured through the use of the Woolf ophthalmic bracket and concentrated filament lamp, together with an iris diaphragm chimney. The latter permits the reduction or increase of the amount of light entering the eye, as it is agreed that a large pupil requires less light, a small pupil requiring more light. The bracket referred to permits the operator to swing the light into any desired position ([Fig. 9]), while the iris diaphragm chimney serves as a shutter. This apparatus may also be employed for muscle testing, as described in a subsequent paragraph.