Slab off is primarily used to address which issue?

Slab off is a specialized technique used in lens manufacturing to create a vertical prism in one lens, which effectively compensates for vertical imbalance in vision. This condition often arises when there is a significant difference in the spherical prescription between the two eyes, leading to misalignment that causes issues such as double vision or discomfort. By incorporating a slab-off prism, the optician helps to equalize the visual experience for the patient, providing clearer and more comfortable vision by preventing the unequal eye alignment that may otherwise result in eyestrain or other visual disturbances.

In contrast, astigmatism correction primarily involves using cylindrical lenses to address refractive errors due to the uneven curvature of the cornea or lens. Near vision enhancement typically focuses on using different lens designs or add powers (such as bifocals or progressives) to improve vision for tasks like reading. Color contrast improvement relates to enhancing visual perception in low-contrast conditions and is not directly linked to the alignment issues that slab off addresses. Therefore, slab off is specifically aligned with resolving vertical prism imbalance, making that the accurate choice in this context.