What factor is critical when deciding on the use of slab off for patients?

When determining the appropriateness of slab-off, the critical factor to consider is the prescription difference between the patient's eyes, especially the vertical imbalance that may result from differing lens prescriptions. Slab-off is a technique used in lens crafting to alleviate the discomfort and visual distortion caused by this vertical imbalance, particularly when one lens requires significant prism correction.

A substantial difference in prescription can lead to issues such as "diplopia" (double vision) or an inability to comfortably fuse images from each eye when gazing at different heights. In such cases, slab-off compensates for the prismatic effect and helps to provide clearer and more comfortable vision for the patient.

While other factors such as lens material preferences, budget, and overall visual acuity play roles in overall patient care and satisfaction, they are not critical determinants for the decision of implementing slab-off in specific cases. The primary focus should always be on how much difference exists between the prescriptions and whether slab-off will effectively manage any resulting visual discomfort.