Ophthalmic Optics Final exam - [McCleary] Multifocal lenses -> Absorptive lenses (Handouts 11-15)

Flat-top bifocal

Also known as a "Straight Top" bifocal:

One-piece

All non-glass modern bifocals are ________________, in which you can physically "feel" the small ledge at the top of the segment.

Opposite

For a modern bifocal, cylinder is ground on the side ______________ the add.

Front

Since minus cylinder is standard today the add is on the ___________ of the lens.

Total inset

The horizontal distance between the seg OC and the frame GC; it corresponds with NPD:

Flat-top bifocal

Also known as a "D segs" bifocal:

FT-28

The most common flat-top bifocal is the ________________.

28mm

The most common width of a flat-top bifocal is ______________________.

5mm

The OC for FT-25 and FT-28 is _____________ below ledge.

4.5mm

The OC for FT-35 is ____________ below ledge.

Ledge

The OC for FT-40 and FT-45 is at the ________________.

+2.00

Above the BF line of Dwight's FT-28 specs, you measure -0.50-3.00x075 OD; below the line you measure +1.50-3.00x075 OD. What power add was Rx'd?

Image jump

The apparent displacement of an object as the eye crosses the top edge of the segment due to prismatic effect:

Round segs

A ________________________ bifocal has a high image jump.

Round segs

For a ___________________ bifocal, the optical center is in the middle of the segment.

4.5mm

The OC of a curved top is _____________ below top.

Image jump

Crossing into the bifocal will shift the image due to the prism present in the bifocal which is known as:

Image jump

The amount of _____________ is independent of the distance power.

d

Which variable is equal to the distance from the top of the segment to the OC of the segment?

2.2 BD

How much image jump does a bifocal with a round 22 seg have, as you enter the top of the bifocal, if the add is a +2.00?

5mm

In a FT-25, the optical center is _____________ below the top of the segment.

0.75 BD

Calculate the image jump for a FT-25 with an ADD power of +1.50D.

Executive bifocal

For an ________________, the optical center of the seg is at the top of the seg.

0

Calculate the image jump for a FT-40 with an ADD power of +1.50D.

0.9 BD

Calculate the image jump for a FT-35 with an ADD power of +2.00D.

Ribbon seg

A _________________ bifocal has the same rules as a flat-top bifocal for finding OC height.

FT-45

A FT-40 and ______________ flat-top bifocal will have their OC at the top of the seg.

Ultex

The OC for a ______________ bifocal is the radius of the seg (often 19mm).

+5.25 DS

OD +3.25sph OS +3.25sph Add +2.00 --> What is the total power/near prescription through this add?

Plano

OD -2.25sph OS -2.25sph Add +2.25 --> What is the total power/near prescription through this add?

One-piece

For a modern _______________ bifocal, increased plus is obtained by grinding a different curve on the front or back of the lens.

PALs

"Invisible" or "no-line" bifocal:

PALs

Power increases gradually from distance to the near portion of the lens along a central region called the “corridor” or “channel:"

Near zone

Consists of the distance power plus the addition power in a PAL:

Progressive/Intermediate zone

Transition between distance and near zones where clear vision is possible in a PAL:

Variable

The additional power in a PAL is achieved via ______________ curvature.

PALs

Essentially, the lens is a merging of continually shrinking spheres for ____________.

PALs

The base curve of _____________ varies gradually from a minimum value in upper distance portion to a maximum value in the lower near portion.

Astigmatism

The trouble with a variable curve in PALs is unwanted _______________ which causes distortion in the lower periphery.

Astigmatism

These areas of unwanted ______________ in PALs cause: blur and “swimming” sensation.

Increase

A higher PAL ADD power will _____________ distortion.

Isocylinder

The amount of unwanted cylinder in a PAL is represented as an _____________________ (or astigmatism) plot.

Hard design

The _______________ of PALs concentrates the distortion into smaller areas but creates higher levels of blur and distortion w/ shorter, narrower corridors.

Soft design

The _______________ of PALs spreads distortion across larger areas and reduces overall magnitude of blur and creates longer, wider progressive corridors.

Soft design

Which design of PALs will narrow the distance and near zones of clear vision requiring more head movement?

Hard design

Which design of PALs will increase the areas of clear vision (wider distance & near zones) requiring less head and eye movement?

Nasally

Later PALs were asymmetrically designed with separate/unique right and left lenses that displaced the near zone ___________________.

Symmetrically

Early progressive lenses were designed _______________.

Horizontal

For PALs, _____________ symmetry minimizes differences in induced cylinder between corresponding points on the nasal and temporal sides of the corridor.

False

T/F: PALs have image jump.

PALs

Continuous uninterrupted range of clear vision, no line cosmesis, and no image jump are advantages of _____________.

False

T/F: You should prescribe an ABI patient a PAL.

Head movement

A disadvantage of PALs is increased __________________: consider not rx'ing for those with neck problems or ABI patients.

Peripheral

A disadvantage of PALs is ______________________ distortion: which can be minimized depending on the design.

Adaptation

A disadvantage of PALs is ______________________ difficulty, which is true for all MF styles and new presbyope.

Occupational progressive lenses (OPLs)

Class of PAL designs that emphasize wide intermediate and near zones w/ low levels of peripheral astigmatism (used for computer):

Driving

Education to patient is paramount with PALs, especially blurry distance vision -> therefore, they shouldn’t be worn for _______________.

PALs

The seg height is measured from the center of pupil to deepest part of frame for _________________.

Center of pupil

The seg height for a PAL is measured from the __________________ to deepest part of frame.

Personalized

A ________________ PAL will have biometric, lifestyle, wavefront, and behavioral data in addition to the actual vertex, tilt, and wrap measurements.

Customized

A ________________ PAL will have actual vertex, tilt, and wrap measurements are used to redesign the lens.

Optimized

A ________________ PAL is one in which the manufacturer uses default vertex, tilt, and wrap measurements to redesign the lens.

Vertical imbalance

A differential vertical prismatic effect between the two eyes:

Anisometropia

Vertical Imbalance is most likely a problem when the visual axes are lowered for reading, namely when a patient with corrected _______________ lowers their eyes to read through an add.

1.50D

The wearer may experience symptoms of diplopia, line skipping, nausea/discomfort with reading, if the difference between the right and left lenses is greater than or equal to ____________ and each eye is correctable to 20/60 or better.

1.50D

Consider vertical imbalance symptomatic (especially recent onset) w/ pts that have ≥____________ power difference in vertical meridian of each lens.

Recent onset

Vertical imbalance is especially a problem if _____________ and unilateral.

Vertical imbalance

Unilateral and recent onset of cataract surgery, trauma, or retinal disease can lead to ___________________.

Eyes

To determine if vertical imbalance will be a problem: If patient drops ______________ to read then they are accustomed to imbalance and probably won’t need compensation.

Head

To determine if vertical imbalance will be a problem: If patient drops ______________ to read then they are reading through the OC to prevent vertical imbalance and this patient will probably experience difficulty in multifocal lenses.

Total prismatic effect

The sum of the prism induced by the distance lens and segment lens:

Two separate

The easiest method for prescribing prism at near is to have ___________________ pairs of glasses.

Fresnel prism

Which method for prescribing prism at near will reduce optics?

Split lens/Cement segment

Adhering 2 separate lenses together to prescribe prism at near:

Lower lid margin

For a flat-top bifocal, the seg height is measured from the ___________________ to the deepest part of the lens.

True

T/F: FT bifocals can be Rx'd to ABI patients.

Ultex

What bifocal has a round segment with very big diameter (can be 38 mm)?

Executive bifocal

Which bifocal type is used for myopia control in kids and has no image jump?

Executive bifocal

Which bifocal type has the add segment covering the entire bottom half of the lens?

Ribbon seg

Which bifocal type is basically the FT with the bottom cut off?

Trifocal

Three distinct areas of viewing and three focal lengths:

50%

The intermediate add on the trifocal is ____________ of the near add power.

Trifocal

For fitting a _____________, the seg height should be measured from the lower pupil margin to the deepest part of the frame.

Lower pupil margin

For fitting a trifocal, the seg height should be measured from the _______________ to the deepest part of the frame.

Flat-top bifocal

For fitting a _______________, the seg height should be measured from the lower lid margin to the deepest part of the frame.

Anisometropia

Unequal refractive state between the two eyes, occurring in one or both principal meridians:

1.00D

Anisometropia is clinically significant if they have more than _____________ of anisometropia.

Anisometropia

Uncorrected ____________________ can lead to suppression or amblyopia if patient is <6-8 years old.

Anisometropia

A patient with corrected __________________ may be happy with crooked glasses because this accounts for the prismatic differences the patient experiences.

4 BO

OD: +3.00 DS, OS +1.00 DS. What is the prismatic effect during distance fixation when the patient looks 20mm to the left of optical centers?

Horizontal

Compensating for ________________ prismatic effects seldom causes problems/symptoms for the anisometrope.

Horizontal

ABI patients may have poor NFV/PFV ranges which can result in ________________ prismatic effects being more impactful than with a normal anisometrope.

True

T/F: Vertical imbalance is usually more problematic than horizontal.

Vertical imbalance

Our eyes have limited capability of vertical fusional movements which can lead to ___________________ when reading, especially for a corrected anisometrope.

2 BU OS

Uma reads 10mm below the distance OCs of her OD +1.50-1.00x180, OS +2.50 DS lenses. What is the total (across both lenses) differential vertical prismatic effect?

Unilateral

Vertical imbalance is especially a problem if recent onset and _____________________.

Vertical

Poor ____________ fusional ranges compared to PFV and NFV ranges contribute to vertical imbalance.

20/60

The wearer may experience symptoms of diplopia, line skipping, nausea/discomfort with reading, if the difference between the right and left lenses is ≥1.50D and each eye is correctable to ____________ or better.

Near

In summary, your red-flags for vertical imbalance are symptomatic aniso- presbyopes with glasses. Symptoms like eyestrain, double vision, headache, & poor adaptation to MF lenses will show up during ____________ work.

Head

If patient drops their ____________ to read, this patient will probably experience difficulty in multifocal lenses.