bozr_bvp_cl_info_flashcards

Question 1

How would you check the BOZR (Back Optic Zone Radius) of a contact lens?

Answer 1

Using a radiuscope, keratometer with conversion charts, wet cell projection system/electronic system, templates (for soft lenses), or focimeter technique.

Question 2

How would you measure the BVP (Back Vertex Power) of a soft lens?

Answer 2

With a focimeter, measuring the front and back OZR, then calculating the powers and deducting for BVP.

Question 3

How can you measure the TD (Total Diameter) of a contact lens?

Answer 3

Using a V gauge, projection system, traveling microscope, or hand loop with an engraved scale.

Question 4

How would you measure the BOZD (Back Optic Zone Diameter) of a contact lens?

Answer 4

Using a projection system or hand loop with an engraved scale.

Question 5

What is a full specification for a soft contact lens?

Answer 5

Manufacturer, design, BOZR, total diameter, back vertex power, and fixed material/handling tint by the manufacturer.

Question 6

What is the Dk value of a contact lens?

Answer 6

The Dk value is the physical property of a contact lens material describing its intrinsic ability to transport oxygen. It is defined as the rate of oxygen flow through the material under specific conditions of thickness and pressure, and it increases with temperature.

Question 7

What are the disadvantages of high Dk RGP (Rigid Gas Permeable) contact lens materials?

Answer 7

Higher hydrophobicity (resistance to water), causing poor wetting, greater susceptibility to deposits, and more brittle and fragile compared to low Dk materials.

Question 8

What is the difference between oxygen permeability (Dk) and oxygen transmissibility (Dk/t)?

Answer 8

Oxygen permeability (Dk) refers to the material’s permeability at a given thickness and temperature, while transmissibility (Dk/t) accounts for the actual thickness of the lens, giving the oxygen transmission through the entire lens.

Question 9

How is the wetting angle of a contact lens measured?

Answer 9

By the Sessile Drop Method or Captive Bubble Method, which measure the contact angle of liquid or air on the surface.

Question 10

What is the six-part classification for contact lens materials?

Answer 10

1. Prefix, 2. Stem, 3. Series Suffix, 4. Group Suffix, 5. Dk Range, 6. Surface Modification Code.

Question 11

Who is authorized to fit contact lenses in the UK?

Answer 11

Registered medical practitioners, dispensing opticians with a contact lens qualification, optometrists registered after December 31, 1960, optometrists with additional qualifications (e.g., DCLP), and supervised students.

Question 12

What changes were caused by the GOC’s Section 60 order regarding contact lens practice?

Answer 12

Non-medical professionals can now supply contact lenses, create lists of practitioners for specialist optical services, and regulate plano (non-prescription) lens sales.

Question 13

What is the difference between hypoxia and hypercapnia in contact lens wear?

Answer 13

Hypoxia is reduced oxygen availability, while hypercapnia is the accumulation of carbon dioxide under the contact lens.

Question 14

What is ‘3 & 9 o’clock staining’ in rigid lens wearers? What causes it and how is it managed?

Answer 14

Caused by poor blinking, reduced tear flow, excessive edge lift, or tight lenses, drying the cornea at the 3 & 9 o’clock positions. Managed with blinking exercises, adjusting lens design, and using more wettable materials.

Question 15

What is dimple veil staining, its cause, and management?

Answer 15

Air bubbles trapped under steep-fitting lenses causing indentations in the cornea. Managed by refitting with a flatter lens or different peripheral fitting lens.

Question 16

What is deep stromal opacification and how should it be managed?

Answer 16

Caused by long-term central corneal hypoxia, managed by stopping lens wear, monitoring long-term, and avoiding lens wear in the future.

Question 17

What are microcysts in contact lens wear and how are they managed?

Answer 17

Caused by hypoxia or solution toxicity, appearing as small fluid-filled vesicles. Managed by reducing lens wear time and switching to a higher Dk/L material.

Question 18

What are corneal infiltrates, their causes, and treatment?

Answer 18

Caused by prolonged hypoxia, immune response, or chemical toxicity. Managed by discontinuing lens wear until resolved, using antibiotics, and switching to disposable lenses.

Question 19

What is the mechanism behind CLAPC (Contact Lens Associated Papillary Conjunctivitis)?

Answer 19

Allergic response to lens proteins, preservatives, mechanical abrasion, and corneal hypoxia.

Question 20

How is CLAPC graded and managed at each level?

Answer 20

Grades 0-1 require cleaning and solution adjustments. Grades 2-3 require lens refit and use of mast cell stabilizers. Grade 4 requires lens removal until resolved.

Question 21

What is vCJD (Variant Creutzfeldt-Jakob Disease) and its relevance to contact lens practitioners?

Answer 21

vCJD is a prion disease that may potentially be transmitted through re-use of contaminated contact lenses.

Question 22

What does the General Optical Council’s policy state about the reuse of diagnostic contact lenses?

Answer 22

Contact lenses should not generally be reused, but special diagnostic lenses can be reused if properly cleaned and disinfected.

Question 23

What are the consequences for practitioners who do not follow the GOC’s policy on contact lens reuse?

Answer 23

Practitioners who do not follow the GOC policy may be charged with serious professional misconduct.