Presbyopia and Multifocals Flashcards
The ability of the eye to variably focus is known as what?
Accommodation
Which structure of the eye provides it with variable focusing capability?
Crystalline lens
How much accommodative ability does the average person have at birth?
15.00 D
What is the definition of presbyopia?
The inability to see near objects clearly and comfortably
As a person ages, their near point does what?
Recedes
What percentage of the US population was estimated to become presbyopic by the year 2020?
42%
According to US Census data projected to 2050, which is the only age group that will show an increase in number?
55+
What percentage of the current US population over 55 needs eyewear?
84%
As a practicing optician, your role with presbyopic patients will be to determine their lifestyle needs and wants in order to do what?
Match product features and benefits to them
What was the earliest form of presbyopic lens correction?
Single vision lenses - readers
Who is attributed with the concept of correcting presbyopia with bifocals?
Benjamin Franklin
What was the design of the first bifocal lens?
Two differently powered halves secured in the same eyewire
What was a problem that was not associated with August Morck’s cemented bifocal lenses?
The different indices between the distance lens and the wafer lens caused color aberration for the wearer
What was the name of the glass bifocal lens design that was the first to use a fusing process?
The Kryptok
Which bifocal lens exhibited color aberration for the wearer through the segment?
Kryptok
When was the first trifocal lens developed?
1936
What is the furthest and closest a person will be able to see if he is looking through a plano distance, +2.50 add multifocal and has 4.00D of accommodative amplitude?
40cm to 15.4cm
For a specified distance rx power, what happens to the ranges of clear vision through a segmented multifocal as add powers get high?
The zones shrink
What is a significant indication of the “Ranges of Clear Vision Through Multifocals” chart?
Fixed power zone segmented lenses may not be the best way to correct presbyopia
Why did progressives take so long to enter the marketplace from the time they were first theorized?
The technology needed to produce them was not available
The blended region between the distance and near zones of a progressive addition is known as the _____ zone.
Intermediate
When a lens has its surface astigmatism concentrated into smaller areas of the lens, it is classified as _____ design
hard
Which progressive lens design classification do most manufacturers use?
A combination of hard and soft
Who designed the first progressive addition lens?
Bernard Maitenaz
How did the original Varilux lens use aspheric power?
It used all its progressive power in 12mm
How did the Varilux II lens use aspheric power?
The lens was completely progressive from top to bottom
Which progressive addition lens was the first to employ true right and left blanks?
Varilux
What is the advantage of using multi-design for progressive addition lenses?
The lens design changes as add power increases based on the intended needs of the wearer as they age
Define asymmetrical design in progressive lenses
There is more surface astigmatism in one side of the lens than then other and/or the areas of surface astigmatism are not equal
What is the advantage of a short corridor progressive lens design?
It allows the use of a shallow B measurement frame
What is the best method for assessing the potential success of a progressive addition lens?
Wearer trials
All early progressive addition lenses were designed for what?
General use
What is the name of the software files used by direct-to-surface (free-form) generators?
Point files
Why should you have the lens markings on a progressive lens at the time of delivery adjustment?
So you can accurately align the fitting cross with the pupil center
