optic zone diameter

Diameter of the optic zone (front or back) of a contact lens measured to the surrounding junction. It is commonly specified in millimetres. Specifically, there are the back optic zone diameter (BOZD), formerly called back central optic diameter (BCOD), and the front optic zone diameter (FOZD). It is often difficult to measure these dimensions due to the blending of the line separating the zones, especially for the back optic zone diameter. The region surrounding the central optic zone is the peripheral zone. If there is more than one, the zones will be numbered first, second, etc., beginning with the zone immediately surrounding the central optic zone. The diameter of each peripheral zone is referred to as the back (or front) peripheral zone diameter (BPZD). See blending; total diameter; edge lift.

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The BC is also referred to as back optic zone (BOZ), which is influenced by two independent parameters: back optic zone radius (BOZR); and back optic zone diameter (BOZD).

Adding ortho-k to your practice: This article provides a guide to get practitioners started with ortho-k contact lens fitting, covering the equipment needed, optimal fitting characteristics and troubleshooting tips

Often the front optic zone diameter and BOZR are adjusted to reduce or increase the centre thickness (CT) to ensure suitable lens handling, optical performance and oxygen transmission.

Table 1 Summary of lens design parameters with abbreviations, symbols and tolerances from ISO 18369-1:2009, ISO 18369-2:2012 and ISO 18369-3:2006 Parameter Abbreviation Symbol Back optic zone radius BOZR r0 Back or front B/FPR [r.sub.1,2 ...]/ peripheral radius [r.sub.-a1,a2 ...] Back optic zone diameter BOZD 00 Back/front peripheral B/FPZD 01,2../0a1,a2 ...

Verification and identification of contact lenses

* Pupil size in average and low illumination--this influences back optic zone diameter (BOZD).

RGP lens selection

This measurement should be used as a guide to ensure the Back Optic Zone Diameter (BOZD) is greater than the largest pupil diameter.

The soft approach to RGPs: Part 2: RGP fitting made easy

a) Back optic zone radius (BOZR) and lens thickness b) Back optic zone radius (BOZR) and back optic zone diameter (BOZD) c) Back optic zone radius (BOZR) and back vertex power (BVP) d) Back optic zone diameter (BOZD) and lens thickness

Anterior eye & contact lens assessment course code: C-15341 O/D/CL

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