18VAC80-30-120. Lenses and frames standards.
A. Power Tolerance (diopters).
| Sphere: Plano to ±.6.50 | ±.13 diopter |
| Above ±.6.50 | ±2% |
| Cylinder: Plano - 2.00 | ±.13 diopter |
| -2.12 to -4.50 | ±.15 diopter |
| above -4.50 | ±4% |
B. Cylinder Axis.
| Cyl. Power Diopters | Degrees ± |
| 0.12 - 0.37 | 7° |
| 0.50 - 0.75 | 5° |
| 0.87 - 1.50 | 3° |
| 1.62 and above | 2° |
C. Distance Optical Center. Contribution to net horizontal prism from processing should not exceed 2/3 prism diopter. A maximum of ±2.5mm variation from the specified distance optical center is permissible in higher power lens combinations.
D. Prism Tolerances (Vertical). Contribution to imbalance from processing should not exceed 1/3 prism diopters. A maximum of 1.0mm difference in vertical level is permissible in higher power lens combinations.
E. Segment Location.
| Vertical | ±.1.0 mm |
| Horizontal | ±.2.5 mm |
Tilt or twist in the case of a flat-top segment, the tilt of its horizontal axis should be less than 1/2 mm in differential elevation between the segment edges.
F. Multifocal Additions.
| Plano + 8.00 | ±.13 diopter |
| Above + 8.00 | ±.18 diopter |
G. Base Curve. When specified, the base curve should be supplied within ±0.75 diopter.
H. Warpage. The cylindrical surface power induced in the base curve of a lens should not exceed 1 diopter. This recommendation need not apply within 6mm of the mounting eyewire.
I. Localized errors (aberration). Areas outside a 20mm radius from the specified major reference point or optical center need not be tested for aberration. Progressive lenses are exempt from this requirement.
Statutory Authority
§ 54.1-201 of the Code of Virginia.
Historical Notes
Former 18VAC100-20-85 derived from Virginia Register Volume 17, Issue 9, eff. March 1, 2001; amended and renumbered as 18VAC80-30-120, Virginia Register Volume 28, Issue 23, eff. August 15, 2012.