This online calculator provides a simple method to adjust a lens power when changes are made to the vertex distance of an optical lens. This adjustment is commonly carried out by an optician when calculating the power of a contact lens, given the spectacle lens prescription.

The Eyeline Back Vertex Distance (BVD) Gauge is an accurate low-cost device for measuring the distance between the back of a lens to the cornea in mm. The set comes with a pouch and calculator. The instructions for plus and minus powers …

2023年12月17日 · In the realm of eye care, precision is key. A back vertex calculator is designed to adjust lens prescriptions based on the distance between the eye and the back surface of a lens. This distance, known as the back vertex distance (BVD), can significantly impact the effectiveness of eyeglasses or contact lenses.

When wearing glasses, the distance from the front of the cornea to the back surface of a lens is called the Vertex Distance. Why is this measurement important? Prescription lenses in eyeglass frames have different effective powers at different distances, tilts and wrap angles from the eye.

Back Vertex Distance (BVD) Place a PD ruler edge along the frame temple with zero ‘0’ at the lens plane and measure the “back vertex distance” in millimeters from the back of the lens to the front of the eyes. *Default Value = 12.5 mm 3 1 2 *Default Values will be used if no measurements are provided. 35 30 25 20 1 5 1 0 5 0 Typical ...

2021年3月29日 · Thus, BVD’s should be measured for: all ‘position of wear’ PPL designs; on all highpowered lenses especially greater than ± 8.00 D (British standards recommend ≥ ± 5.00 D); when matching previous spectacles; and when the test vertex distance is written on the prescription as this is an instruction from the prescriber to create the ...

• Quick left and right BVD measurement • Easily read figures and markings • Top pocket size • Sloping/wedge edges Each Billings PD Ruler is supplied with an informative user guide available to view here

When dispensing, it is possible to measure the BVD with a ruler. However, this is a difficult measurement to take due to the curved nature of lenses and, especially with highly wrapped frames, the difficulty in ascertaining the position where the …

2019年3月5日 · A back vertex distance (BVD) measurement is required to be recorded on the prescription for refractions with a power of >±5.00 dioptres along either axis. 2 However, it should be noted that dependent on BVD, adjustments may need to be made on powers of >±4.00 DS.

One method of making this computation is to convert the power into focal length in millimeters (f = 1000/ D). To this, add the change in vertex distance if vertex distance is increased, or subtract the change if vertex distance is decreased. Then convert …