What type of prism does regular slab off create in the lower portion of the lens?

Regular slab-off creates a base up prism in the lower portion of the lens, which is specifically designed to address vertical imbalances in vision, such as when one eye is significantly stronger than the other. This technique is commonly used in the creation of "slab-off" lenses to help equalize the image height for patients who have a difference in lens thickness due to anisometropia.

By incorporating a base up prism in the lower part of the lens, the slab-off helps to elevate the line of sight for the eye using the slab-off lens, compensating for the lower position of the image created by the stronger eye. This ensures that both eyes can properly align during vision tasks, promoting better binocular vision and reducing issues like double vision or eye strain.

The design effectively brings the visual centers of the lenses closer together in vertical alignment, improving the overall visual comfort for the patient. Understanding the specific effects of different types of prisms is essential in lens design to provide adequate visual correction tailored to individual needs.