Portable Vision Testing and Optometry Technology

We developed an innovative method using the focal length change in the zoom lens to enable subjects with refractive errors to see the E chart image. For myopes, the distant E chart image is in front of the retina. By using the focal length change in the zoom lens, the E chart is located inside the first focal point of the zoom, diverging light. The E chart image is formed on the retina, and the myopes can clearly see the E chart. For hyperopia, the distant E chart image is behind the retina. Similarly, by using the focal length change in the zoom lens, the E chart is located outside the first focal point of the zoom lens and converges light, and the E chart image is formed on the retina. Hyperopia patients can clearly see the converged E chart. The test for myopia was repeated 30 times. The average of the two test values was −0.7, and the rest were −0.8. The error in the two test datasets can be minimized by optimizing the zoom lens, reducing the optical image value, and expanding the field of view (FOV).