Asdfg Flashcards
- What was the primary motivation for developing silicone-based contact lens (CL) materials?
- Reduced manufacturing costs
- 02 permeability
- Increased comfort
- Enhanced visual acuity
02 permeability
- What characteristic of silicone hydrogel (SiHy) CLs makes them easier to handle than hydrogel CLs?
• Smaller size
• Higher water content
• Softer material
• Relative rigidity
• Relative rigidity
- Why should an over-refraction be performed over a well-settled SiHy trial lens before ordering the final back vertex power (BVP)?
• To account for small prescription changes due to induced corneal alterations
• To test lens durability
• To ensure correct lens color
• To check for allergic reactions
• To account for small prescription changes due to induced corneal alterations
- Which mode of wear is SiHy CLs suited for?
- Daily wear (DW)
- All of the above
- Continuous wear (CW)
- Extended wear (EW)
- All of the above
- What type of surface charge do most
SiHy CLs have?
• Alternating positive and negative
• Highly negative
• Highly positive
• Little or no surface charge
• Little or no surface charge
- Which SiHy CL material is known for having a charged surface due to plasma oxidation?
- Lotrafilcon A
- Senofilcon A
- Balafilcon A
- Comfilcon A
- Balafilcon A
- According to the FDA materials grouping system, what group do most SiHy CLs belong to?
- Group 2: High water, Non-ionic
- Group 1 Low water, Non-ionic
- Group 4 High water, Ionic
- Group 3 Low water, Ionic
- Group 1 Low water, Non-ionic
- What is the range of water content found in SiHy CLs?
- 24-75%
- 30-80%
- 24-50%
- 50-75%
- 24-75%
- What is the range of oxygen permeability (Dk) for SiHy CLs?
• 60-120 barrer
• 70-130 barrer
• 55-100 barrer
• 55-140 barrer
• 55-140 barrer
- What is the typical wetting angle range for SiHy CLs when measured with a sessile drop?
• 55-95
• 60-101
• 70-110
• 50-80
• 60-101
- What is the typical wetting angle range for SiHy CLs when measured with a captive bubble?
• 40-55
• 20-35
• 27-45
• 27-45
- What is the refractive index range for SiHy CLs?
•1.373 - 1.426
•1.360 - 1.410
• 1.350 - 1.400
• 1.380 - 1.430
•1.373 - 1.426
- Which of the following is an indication for using scleral lenses?
• Greatly decentred pupils
• Mild astigmatism
• Low myopia
• Mild dry eye
• Greatly decentred pupils
- What is a disadvantage of scleral lenses?
• Easy availability
• Low cost
• Long fitting time
• Quick fitting process
• Long fitting time
- What type of scleral lens allows patients to experience the lens prior to fitting?
• Impression
• Preformed
• Custom toric lenses
• Disposable lenses
• Preformed
- What is an advantage of preformed scleral lenses?
• They are more expensive
• They require more fitting time
• Precise lens specifications are known
• They have limited specifications
• Precise lens specifications are known
- What should be present in the limbal zone of a properly fitted scleral lens?
• No air bubble
• Fenestration
• A tight seal
• Excessive clearance
• Fenestration
- Which parameter affects both the static and dynamic fitting characteristics of a rigid lens?
• Lens age
• Refractive index
• Material color
• Lens diameter
• Lens diameter
- Increasing the back optic zone diameter
(BOZD) of a rigid lens has what effect on apical clearance?
• Randomly changes apical clearance
• Increases apical clearance
• Decreases apical deeranee
• No effect on apical clearance
• Increases apical clearance
- What happens to lens fit if the total diameter of a rigid lens is reduced?
• Tear exchange is reduced
• Lens movement increases
• The lit tightens
• The lens becomes easier to remove
• Lens movement increases
- What must be compensated by -0.25 D for every 0.05 mm increase (flattening) in BOZR?
• Cons diameral
• Corneal curvature
• Lens thickness
• Tear lens power
• Tear lens power
- What effect does a front surface design that increases upper lid interaction have on lens comfort?
• Randomly affects comfort
• No effect on comfort
• Increases comfort
• Decreases comfort
• Decreases comfort
- For a patient with corneal astigmatism greater than 1.50 D, how should the BOZR be adjusted for each 0.50 D increase in astigmatism?
• Increases BOZR by 0.10mm
• Decreases BOZR by 0.05mm
• Increase BOZR by 0.10 mm
• Decrease BOZR by 0.05 mm : erase BOR by 0.50 mm
• Decreases BOZR by 0.05mm
- What is the role of the back mid-periphery in a rigid lens design?
• Aligns with the flattening cornea
• Increases lens flexibility
• Decreases lens durability
• Improves aesthetic appearance
• Aligns with the flattening cornea
- What is Orthokeratology primarily used for?
• Temporarily reduction of myopic correction by contact lenses
• Permanent correction of refractive errors
• Treatment of keratoconus
• Permanent reshaping of the cornea
• Temporarily reduction of myopic correction by contact lenses
- Which type of contact lenses does
Orthokeratology employ?
• Soft contact lenses
• Daily disposable lenses
• Colored contact lenses
• Gas permeable (GP) reverse geometry lenses
• Gas permeable (GP) reverse geometry lenses
- Which EOR is orthok mainly used to treat
• HYPEROPIA
• MYOPIA
• ASTIGMATISM
• PRESBYOPIA
• MYOPIA
- What is one of the key benefits of Orthokeratology?
• Permanent elimination of refractive errors
• Instant vision improvement without adaptation
• Freedom from glasses during the day
• Suitable for everyone regardless of age
• Freedom from glasses during the day
- What age is typically suitable for Orthokeratology?
• Older than 6 years
• Only seniors over 60 years
• Any age, including infants
• Only adults over 18 years
• Older than 6 years
- Which of the following is NOT true about Orthokeratology?
• It uses specially designed contact lenses.
• It permanently reshapes the cornea.
• It requires commitment to ongoing treatment costs.
• It is a non-surgical technique.
• It permanently reshapes the cornea.