Certified Ophthalmic Medical Technologist (COMT) Practice Exam

Slab off is recommended when Anisometropia is equal to or greater than what diopter?

1. 1 to 1.5 D

2. 2 to 2.5 D

3. 3 to 3.5 D

4. 0.5 to 1 D

The correct answer is: 2 to 2.5 D

Slab off is a technique used in the fabrication of glasses, particularly for patients with anisometropia, which is a condition where the two eyes have significantly different refractive power. The purpose of slab off is to help alleviate issues such as aniseikonia—a condition where the images perceived by the two eyes are dissimilar in size—by compensating for the vertical imbalance in the lens powers. The recommended diopter range for slab off typically begins at around 2 diopters of anisometropia. This is due to the fact that a difference of 2 diopters or more can significantly impact visual comfort and function, leading to symptoms like double vision or discomfort when the eyes are trying to focus together. Using slab off helps to create a more balanced vision by adjusting the prism effect of the stronger lens, helping to align the images seen by each eye. Thus, the recommendation for a slab off procedure when the anisometropia is equal to or greater than 2 to 2.5 diopters is based on the threshold at which discrepancies in the image size become prominent enough to warrant intervention for patient comfort and effective binocular vision.