40 Questions
What is the primary reason for using a trial set in complex fitting?
To fit specialist keratoconus designs
What is the typical size of the Total Diameter (Td) in RGP lenses?
9-10mm
What is the purpose of measuring the Horizontal Visible Iris Diameter (HVID)?
To set the total diameter of the lens
What is the advantage of using a large lens diameter?
It allows for a larger BOZD without sharp transitions
What is the rule of thumb for calculating the corneal astigmatism from K readings?
0.05mm K approximates 0.25D Cyl power
What is the primary reason for using a smaller Total Diameter (Td) in RGP lenses?
To reduce lid interaction and improve centration
What is the purpose of converting the Spectacle Rx into Ocular Rx?
To calculate the total ocular astigmatism present
What is the primary advantage of using Hybrid FS and Hybrid FS Plus lenses?
Harder material with increased resistance to protein and lipid deposits
What is the primary disadvantage of using small diameter lenses?
The edge of the lens interacts with the sensitive edge of the lids and may be uncomfortable
What is the purpose of calculating the corneal astigmatism from K readings?
To ensure alignment with the flattest meridian and tear lens correction
What is an advantage of RGP lenses in terms of vision?
Sharper vision
What is a disadvantage of RGP lenses in terms of cost?
Higher initial cost
What is a benefit of RGP lenses for presbyopes?
Translating bifocals with less contrast loss
What is a common replacement interval for RGP lenses?
6 months
What is an important factor to consider when selecting an RGP material?
All of the above
What is a disadvantage of RGP lenses in terms of patient comfort?
Modern soft CL cause limited neo
What is a benefit of RGP lenses for patients with irregular corneas?
Better fit and vision
What is a potential issue with RGP lenses in terms of corneal molding?
RGP lenses may be used beyond their best for corneal molding
What is a potential complication of prolonged RGP lens use?
Induced ptosis
What is a factor to consider when deciding what to order for a patient?
Patient's occupation
What is the primary reason for ensuring alignment fit in RGP lenses?
To achieve an even spread of weight across the cornea
What is a characteristic of Fluorosilicone Acrylates (FSAs) compared to Silicone Acrylates (SAs)?
FSAs are harder and relatively resistant to protein deposits
What is the typical range of total astigmatism present in the BVD-corrected ocular Rx that can be corrected with a spherical RGP lens?
Up to 2.50DC
What is the purpose of measuring the Vertical Palpebral Aperture (VPA)?
To assess the ease of insertion and removal
Which type of RGP material is more prone to deposits and has a higher scratching surface?
Silicone Acrylates (SAs)
What is the primary reason for using a large Total Diameter (Td) in RGP lenses?
To improve tear exchange and reduce edge stand-off
What is the primary advantage of RGP lenses in terms of contrast reduction for presbyopes?
Translating bifocals reduce contrast less
What is the purpose of converting the Spectacle Rx into Ocular Rx for EACH meridian?
To compare the total ocular astigmatism with corneal astigmatism
What is a benefit of using a hybrid lens, such as Hybrid FS or Hybrid FS Plus?
Increased wettability and reduced flexure
What is the main reason why modern soft contact lenses cause limited neovascularisation?
They are more permeable to oxygen
What is the purpose of measuring the Horizontal Visible Iris Diameter (HVID)?
To determine the ideal lens diameter
What is the primary factor to consider when deciding the replacement interval for RGP lenses?
The lenses' ability to maintain optimal performance
What is a potential issue with using small diameter lenses?
Increased lid interaction and discomfort
What is the primary advantage of using RGP lenses for patients with irregular corneas?
They provide better vision and fit
What is the primary reason why RGP lenses are not suitable for extended wear?
They do not allow for sufficient oxygen transmission
What is the primary benefit of using RGP lenses in terms of cost?
They are more cost-effective in the long run
What is the primary factor to consider when selecting an RGP material?
Oxygen transmission and edge lift
What is the primary disadvantage of RGP lenses in terms of care?
They require more in-depth care
What is the primary benefit of using RGP lenses for patients who want to wear their lenses daily?
They provide better vision and fit
What is the primary reason why RGP lenses may not be suitable for patients with certain occupations?
They may not be compatible with certain environmental conditions
Compare the benefits and drawbacks of Rigid Gas Permeable (RGP) lenses and soft contact lenses, including vision quality, cost, and comfort. Learn which type is suitable for presbyopes, irregular corneas, and Ortho-K.
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