IOLs Flashcards
What are the three uses for IOLS?
- surgical solution for vision loss due to cataract formation
- continuous vision solution for presbyopia
- accommodating vision similar to the lens
What size apertures do spherical lenses work well for?
Smalllllllll
What do spherical lenses generate with large apertures?
Spherical aberrations
Which rays focus first on spherical lenses?
Parasail rays (center)
Aspherical lenses provide what?
Higher image quality with minimal spherical aberrations
With increasing refractive power, what happens to the MTF of a perfect eye?
It increases at a certain spatial frequencies
What happens to the resolution for lenses with aberration as you increase the power above a certain limit?
The modulation (resolution) decreases
Symmetrical IOLs with a refractive index of 1.46 and a 3.0mm show perfect modulation at what power?
+15D
For powers between 15 and 25D in IOLs, what happens to the modulation? What happens when they are more than 25?
- remain constant
- significant loss of modulation
What are monofocal IOLs good for?
- distance vision correction
- verse high image quality
What does the refractive index of monofocal IOLs need to be?
-above 1.406
What is the equation you would use to determine the power of the IOL needed?
A-(2.5)(axial length)-(0.9)(keratometry reading)
What does A stand for in the equation to figure out the power for an IOL?
It is a constant that reflects what the manufacturers have set for the IOL position
For every 1mm difference in the measurement for axial length of the patient, there is a difference of how much in the power needed for the IOL?
2.5D
HELLA SIGNIFICANT
Do monofocal lenses provide “spectacle independence”?
Nope. They do not help near vision, just distance
The base power of the IOL is found in what part of the lens?
The nucleus! The fresnel gives you add
For bifocal lenses, the central zone has what kind of design? The peripheral zone has what kind?
Central: diffractive design
Peripheral: refractive design
Why do bifocal IOLs act as monofocal IOLs in mesopic and scotopic conditions? (At night)
-the pupil gets larger and there is not sufficient energy for diffractive zones
Will bifocal lenses ever give you 20/20 vision at near?
Hell no
Trifocals IOLs provide what kind of correction?
-distance, intermediate, and near vision
If you want a freaking good image quality, what kind of IOL should you have?
Monofocal only
Multifocal IOLs claim to provide __________________, but at what cost?
- claim to provide decent continuous vision
- low quality image, unwanted phenomenon like glare and halos
- they have minimal success!
The extended range of vision IOL is also called what?
Extended depth of focus IOL
What do extended range of vision IOLs claim?
To provide continuous vision AND minimize unwanted phenomena like glare and halo and star burst
How do EDF IOLs do what they do?
- extend your depth of focus by adding and subtracting power to find your max vision and extending it a longer distance
- it gives you a U curve to find your true focus
What is the holy grail of IOL?
Accommodative IOL
What does the accommodative IOL do?
- mimics the natural lens behavior
- provides additional 1D of vision compared to monofocal lens
Are is the accommodative IOL actually accommodative?
No, sucks
-it provides the change in location, but it does not change shape or power, so it cannot be considered accommodative
What is the challenge with wanting to have a smaller incision for IOLs?
Under 2mm is goals, but you would need a lens that would be able to fold
What is PCO?
Posterior capsule opacification
-there is lens epithelial growth
What are the components that lead to lens epithelial growth?
- lens material
- lens edge
What are the problems associated with PCO and what is the treatment?
- decreased VA
- impaired contrast sensitivity
- glare disability
-YAG laser capsulotomy
