Contact Lens 2 - Midterm

- reshaping, front, correction

- sleep, day

- myopia, low astigmatism

Orthokeratology:

- _____ the _____ of the cornea with GP lenses to achieve vision without any need for _____

- wear lenses to _____ and take off during the _____

- primarily for _____ and _____

1950s

When were the first reports published regarding corneal reshaping with CLs?

1962 by George Jessen

When were the first ortho-k lenses made and by whom?

corneal topography

What data do you absolutely need for ortho-k?

- thinning, thickening

- epithelium, stroma

- power, cellular volume, surface area

- reversible

What we know about how ortho-k works:

- central corneal _____ and midperipheral _____

- _____ is largest contributor with _____ minimally affected

- conservation of corneal _____ with _____ and _____ maintained throughout treatment

- effects are _____

- lid pressure

- tear fluid

- surface tension, tear film

Predominating theories of how ortho-k works:

- _____ in closed-eye environment

- changes involve _____ forces

- _____ of _____ at lens edge

T

T or F: The eyelids distort the corneal shape.

- tear film

- tangentially

- center, mid-periphery

- center, periphery

Shearing forces and ortho-k:

- created by _____ beneath lens

- move _____ across epithelium

- positive pressure in _____, negative pressure in _____

- this redistributes and compresses cells from _____ to _____

F

T or F: Entire epithelial cells are moved from the center to periphery with ortho-k.

with pressure in the center of the cornea intracellular fluid/cell components are shifted from center to periphery due to gap junctions between corneal epithelial cells

How does the shift/redistribution of corneal cells occur with ortho-k?

- tangential to see how the lens is sitting on the eye during sleep

- axial to tell how this correlates to change in power

Which topographical maps are used for ortho-k and why?

tangential

This topographical map is used in ortho-k to tell how the lens is sitting on the eye during sleep.

axial

This topographical map is used in ortho-k to track changes in power.

- compression, deformation

- elongation, transfer, intercellular contents

- mitosis, sloughing, redistribution

- 4, epithelial erosions

Conclusions in 2008 study of ortho-k in cat eyes:

- following 4-8 hours of lens wear, epithelial cell _____ and _____ are dominant factors

- _____ of cells in mid-periphery suggest a _____ of _____ may be taking place

- with increased wear time alterations in cell _____, _____, and _____ may play a role in proliferation of cells

- the myopic eye possessed at least _____ cell layers in central thinned epithelium with no obvious histological evidence of _____

Munnerlyn's formula

What do we use to calculate treatment for refractive surgery/ortho-k?

ablation depth (AD) = ((OZ in mm)^2 x refractive error (in D))/3

What is Munnerlyn's formula?

- high Dk

- moisture

- smaller, thinner

- fluid reservoir

Ortho-k's are safer to sleep in due to:

- _____ material

- GP materials don't absorb _____

- lenses are _____ and _____ than scleral lenses

- no _____ required to fill lenses

-0.50D to -6.00D

What is the range of spherical power that is FDA approved to treat with ortho-k?

-1.50D or -1.75D

What is the maximum cylindrical power that is FDA approved to treat with ortho-k?

sagittal depth

This is how deep a lens/eye is at a given chord diameter measured in microns.

Jessen factor

This is the amount of correction added to ortho-k treatment to last throughout the day.

0.50D to 0.75D

What is the usual Jessen factor?

- treatment

- reverse

- alignment

- peripheral

Ortho-k lens design components:

- _____ curve

- _____ curve

- _____ curve

- _____ curve

treatment curve

This portion of an ortho-k lens contains the base curve and is often measured in mm.

reverse curve

This creates sagittal depth in an ortho-k lens and is measured in microns.

alignment curve

This controls centration of the ortho-k lens and is measured in an angle from horizontal.

peripheral curve

This portion of the ortho-k lens allows for tear exchange.

- mold

- calculation, initial lens selector

- fit

Base curve in ortho-k:

- provides _____ for treatment

- derived by _____ or using _____

- NOT adjusted to change _____ of lens

F

T or F: With ortho-k you adjust the fit by changing base curve.

- sagittal depth

- fluorescein ring

- fit

Return zone depth in ortho-k:

- regulates _____ of lens

- provides _____

- can be adjusted to change _____ of lens

steeper, tightens

A larger alignment angle is _____ and _____ the lens on the eye.

- -0.50D, -6.00D

- -1.75D, <1.00D

- symmetric/regular

- small, medium

- active

- fitting, motivated

- compliance

Good ortho-k candidates:

- myopia from _____ to _____

- corneal astigmatism up to _____ WTR or _____ ATR

- _____ topography

- _____ to _____ pupil size

- _____ lifestyle

- committed to term of _____ process and _____

- understands necessity for _____

ideally will be consistently wearing for 6-8 hours overnight

Why is a patient's sleep schedule an important consideration for ortho-k?

- SCL

- SCL dropouts

- mild/moderate, -4.00, 1.00D WTR

- 42.00-45.00D

Ideally your initial 5-10 ortho-k patients should be:

- current _____ wearers

- spectacle wearers that are _____

- _____ myopia (up to _____) with up to _____ corneal toricity

- flat K _____

- 0.75D

- 38.00D, 41.00D

- cylinder, sphere

- corneal, refractive

Proceed with ortho-k with caution in patients with:

- over _____ of ATR astigmatism

- final treatment takes BC below _____ (flat = ______

- _____ is greater than _____

- _____ cylinder doesn't match _____ cylinder

centration, treatment

In ortho-k, higher myopes require _____ first and _____ second.

- decentration

- damage/abrasions

A patient should wash out of ortho-k if there is:

- significant _____

- corneal _____

ocular health

This should be evaluated at every ortho-k visit.

topography

This testing should be performed at every ortho-k visit.

- K, flat K

- refraction, spherical

- eccentricity

To select an ortho-k lens you will need:

- _____ readings (primarily _____)

- _____ (_____ component)

- corneal _____

BC = flat K - treatment - Jessen factor

How do you calculate BC for an ortho-k lens?

+0.50D

What do we use for the power/Jessen factor in an ortho-k lens?

39.25D (8.60mm)

You are fitting a patient with ortho-k lenses. They have K readings of 43.25 @ 180, 44.00 @ 090 and MR of -3.50-0.50x180. What BC should you use?

HVID

This measurement is becoming more important in fitting for ortho-k.

HVID - 0.8mm

What is the diameter of most ortho-k lenses?

- centration

- treatment, distinct, 3mm

- landing, edge lift

When assessing ortho-k lens fit you should look at:

1. _____

2. _____ zone (want it to be _____ and at least _____)

3. _____ zone and _____

less edge lift with ortho-k

How does the edge lift of an ortho-k lens compare to a regular corneal GP?

bullseye pattern

Ideally you should see this pattern in fluorescein and on topography with a well-fitting ortho-k lens.

decrease reverse curve diameter

How can you fix excessive sagittal depth in an ortho-k lens?

decrease alignment zone angle

How can you fix a tight alignment zone in an ortho-k lens?

- central

- mid-peripheral

- staining

If an ortho-k lens has too shallow sagittal depth you will see:

- obvious _____ bearing

- loss of _____ alignment

- corneal _____

- excessive

- tight

- inappropriate

An ortho-k lens that is too steep can be due to:

- _____ sagittal depth

- _____ alignment zone

- _____ lens diameter

central island

You will see this topography pattern if an ortho-k lens is too steep.

superiorly

How will an ortho-k lens decenter if it is too flat?

smiley face

You will see this topography pattern if an ortho-k lens is too flat.

- inadequate

- loose

An ortho-k lens that is too flat can be caused by:

- _____ sagittal depth

- _____ alignment zone

- increasing

- increasing

- increasing

You can fix an ortho-k lens that is superiorly decentered by:

- _____ return curve diameter

- _____ alignment zone angle

- _____ diameter

excessive

If an ortho-k lens decenters superiorly you should check to see if edge lift is _____.

frowny face

You will see this topography pattern if an ortho-k lens is inferiorly decentered.

- tight

- inappropriate

Causes of inferior ortho-k lens decentration:

- _____ alignment zone

- _____ lens diameter

- decreasing

- changing

You can fix an inferiorly decentered ortho-k lens by:

- _____ alignment zone angle

- _____ lens diameter

minimal, tight

If an ortho-k lens decenters inferiorly you should check to see if edge lift is _____ or _____.

inappropriate lens diameter

What will cause lateral decentration of an ortho-k lens?

uneven landing zone fluorescein pattern

What may indicate the need for a toric ortho-k lens?

F

T or F: The BC on an ortho-k lens can be toric.

reverse curve, landing curve, or both

What portion(s) of an ortho-k lens can have added toricity?

- topography

- corneal evaluation

- unaided VA

- VA, NaFl

Exam elements for ortho-k:

- _____ at every visit

- _____ at every visit

- _____

- _____ and _____ with lenses on eyes

1 day, 1 week, 1 month, 3 months, 6 months

What is the follow up schedule for ortho-k after the initial fitting visit?

you want them to come in with the lenses on

Why is the 1 day visit after ortho-k usually first thing in the morning?

axial

What type of myopia is most common?

-0.25 to -3.00D

What is typically classified as mild myopia?

-3.25 to -6.00D

What is typically classified as moderate myopia?

more than -6.00D

What is typically classified as severe/high myopia?

pathologic/degenerative myopia

This condition related to increased axial length is one of the leading causes of visual impairment.

- thinning/atrophy

- foveoschisis

- neovascularization

- RD

- glaucoma

- cataracts

Axial length elongation leads to:

- chorioretinal _____

- _____

- choroidal _____

- increased risk for _____

- increased risk for _____

- increased risk for _____

23ish mm

What is the average axial length of an emmetrope?

2.50D-3.00D

1mm of axial length equals how much change in spectacle Rx?

myopia, risks, myopic progression

In 2021 the World Council of Optometry stated that all parents should be educated on _____ and potential _____ and that managing _____ should become the standard of care.

- genetics

- outdoors

- education

- lifestyle changes

There is sufficient evidence to support the following positions:

- _____ play a limited role in myopia development

- spending more time _____ is protective against myopia onset

- more _____ is associated with more myopia

- the COVID-19 pandemic has most probably increased the incidence of myopia through _____

67%

Every 1D increase in myopia increases the risk of myopic maculopathy by _____.

40%

Every 1D decrease in myopia decreases the risk of myopic maculopathy by _____.

- under-correction

- over-correction

- outdoor play

- PALs/bifocals

- spherical GP lenses

Historical attempts to slow myopia included:

- _____

- _____

- _____

- _____

- _____

onset

Time outdoors appears to be related with the _____ of myopia.

dopamine

Light exposure is related to the release of retinal _____ which could be critical in regulating ocular growth.

- orthokeratology

- soft CLs

- pharmaceuticals

- spectacles

- red light

Current methods to slow myopia:

- _____

- _____

- _____

- _____

- _____?

- negative

- on the fovea

- in front of the retina

Ortho-K optical correction:

- the post OK cornea generates a _____ curvature of field

- central rays of light are focused _____

- peripheral rays of light are focused _____

- on the fovea

- behind the retina

- increase

Single vision spectacles in myopes:

- central rays of light are focused _____

- peripheral rays of light are focused _____

- leads to _____ in axial length

center distance and periphery near

A soft multifocal lens needs to have this design in order to be effective in myopia management.

- not fully understood

- muscarinic antagonist

- dopamine

- atropine, 0.01%, 0.025, 0.05%

Pharmaceuticals for myopia management:

- mechanism of action _____

- topical _____

- stimulates _____ release

- use _____ with concentration _____, _____, or _____

rebound

What is the main concern with the use of atropine for myopia management?

F

T or F: Spectacle designs for myopia control are currently available in the US.

red light therapy

This method of myopia management has shown more significant improvement than other methods but its long term safety is still unknown.

- toric

- keratoconus

- trauma

- refractive surgery

- aphakia

- high

- glaucoma

- macro/micro

Indications for custom soft lenses:

- custom _____ designs

- _____

- post _____

- post _____

- _____

- _____ refractive error

- _____

- _____ cornea

- base curve

- power

- diameter

- thickness

- optical zone diameter

- material

Soft lens parameters that can be customized:

- _____

- _____

- _____

- _____

- _____

- _____

- central corneal curvature

- eccentricity

- corneal diameter

- scleral sag

- corneal angle

Anatomical features that contribute to the sagittal height of the anterior eye:

1. _____

2. _____

3. _____

4. _____

5. _____

250 microns

You need to make a sagittal depth change of at least _____ to observe a difference in the on-eye fit.

patient is struggling with comfort

When may you consider using a custom SCL when you are already satisfied with a fit?

0.1mm

Both base curve and diameter can be ordered in _____ steps in custom soft lenses.

HVID + 2mm (1mm overhang on either side)

How do you determine lens diameter when ordering a soft contact lens?

- HVID

- mean K

- effective K

- BC radius

Steps to designing a custom soft lens:

1. measure _____

2. measure _____

3. calculate _____

4. determine _____