Chadwick Hemiaopsia Lens
The Chadwick Hemianopsia Lens is a visual field expander based on the InWave lens which was originally developed by Michael Onufryk, a former Kodak optical engineer in Rochester, New York. Onufryk developed it as a bilateral system which created an image shift, but not a true visual field expansion.The Chadwick Hemianopsia Lens is fit as a monocular system on the side of the visual field loss.
However, when prescribed as a monocular system only on the side of the visual field loss, it becomes an effective true visual field expander for hemianopsia patients.
A version of it was available as the INWave lens in the 1990s, but the InWave was only available as a 12 prism diopter system where the Chadwick hemianopsia lens is available in a wide range of prism powers.
It functions similar to the Gottlieb VFAS lens, but it is fabricated as a full lens visual field expander fused to the base prescription lens on the side of the visual field loss. It provides a true expansion of visual field. Mounted on the side, it requires a scanning movement by the patient into the system but creates a resultant image jump.
Patients do not spend time directly looking through the system, but rather perform quick glances that graze the area of the Chadwick Lens. This allows the patient to appreciate the visual field expansion without the disruption of continuous double vision.
By limiting the size of the patient’s frame, the thickness and weight of the prismatic portion of the prescription can be carefully controlled and a good cosmetic appearance can be achieved. Our experience tells us that a maximum length of 18 mm or less from edge of the prismatic portion to the temporal edge of the frame should be the goal. The wider the segment, the thicker the system becomes.
The patient below, demonstrates a Chadwick Hemianopsia Lens designed in a small frame that allows the thickness to be controlled and a good cosmetic appearance achieved.
If a larger frame must be used to accommodate certain types of multi-focals or in cases of a larger face, a Gottlieb or EP lens may be a better choice.
With the Chadwick Hemianopsia lens, scanning training and extensive driver's training, our doctors were recently able to help an Israeli soldier with a TBI to become the first hemianopsia patient to receive a driver's license in Israel.