3. OrthoK - Advanced Contact Lenses Fall 2026

20 year old student

OD: -3.00-0.50x180

VA: 20/15

Ks: 44.00/44.50@090

How do we use orthoK to correct this refractive error?

You will overcorrect the patient by +0.50D so they are plano at the end of the day. Purposely fit a flat BC on the eye

20 year old student

OD: -3.00-0.50x180

VA: 20/15

Ks: 44.00/44.50@090

What are the Ks following treatment?

-40.50

-Want to fit BC -3.00 + -0.50 = -3.50

When did orthoK originate?

In the 1950s

Who was OrthoK proposed by?

Jessen

What are orthoK lenses approved for in the US?

for correction of myopia

How large of RE can orthoK lenses correct?

-6.00DS; -1.75DC

Higher amount of RE = (higher/lower) likelihood for OrthoK success

lower

Are orthoK lenses FDA approved for myopia control?

No -- they are sometimes used off label in this way

What are the function of corneal reshaping contact lenses?

Correction of myopia and corneal astigmatism (similar concept to refractive sx)

How do orthoK lenses work?

-Flatten the cornea and diverge light onto the retina

-Removes astigmatism caused by corneal toricity

How much do we need to flatten the BC of orthoK lenses in order to get an effective treatment?

RE + 0.50 Jessen factor

When do patients wear orthoK lenses?

overnight

OrthoK Goal in Topography (Pic)

OrthoK Goal in Topography (Pic)

What is the relative shape of the topography reading that we are hoping to get with orthoK?

Flat in the center; mid-peripheral steep ring; flatter in the periphery

What is the avg treatment zone size for orthoK lenses?

4mm

New patients to orthoK can report ______ at first d/t spherical aberration

halos

Describe an ideal candidate for orthoK lenses

-Up to -4.50D myopia

-Up to -3.00DC

-Pupils around 6mm

-Soft lens intolerance

Even though some lens brands market that they can correct up to 3.00DC, what SHOULD BE your upper limit for astig correction according to Dr. Zimmerman?

-1.75 to -2.00

Who are the easiest patients to fit in an orthoK lens?

-Current soft lens or GP wearers

-Moderate myopia less than 4D

-Low astig up to 0.75 WTR

-< 0.75D residual astigmatism

What are important considerations to ask patient about when talking about orthoK lenses?

-When do they want to wear CLs?

-Do they swim regularly?

-Do they work around toxic substances?

-Do they have CLs related dry eye?

-What is their pupil size?

Normal Geometry (prolate) vs Reverse Geometry (oblate) (Pic)

Normal Geometry vs Reverse Geometry (Pic)

Describe reverse geometry in an orthoK lens

BC flat in the center, steeper in the midperiphery, flatter in the periphery

How many zones does an orthoK lens usually have?

4-5 zones

What are the usual curves on an orthoK lens?

-BC

-Reverse curve

-One or two alignment curves

-Peripheral curve

Which curve on an orthoK lens has the greatest influence on centering the lens?

One or two alignment curves

The BC is fit ______ than the flattest meridian

flatter

Overcorrection of orthoK that is done on purpose

Jessen factor

A patient is a -4.00. Ks: 41.00. What orthoK lens power are we likely to fit them in?

36.50D

OrthoK Lens Design (Pic)

OrthoK Lens Design (Pic)

What does the BC of an orthoK lens create?

Treatment zone

What does the return zone depth of an orthoK lens create?

Reverse curve

What does the landing zone angle of an orthoK lens create?

alignment curve

OrthoK Lens Design (Pic)

**central touch (flat); uniform ring of steepened area; alignment in mid periphery

OrthoK Lens Design (Pic)

The Base Curve of the orthoK lens provides the _______

refractive correction

What else does the BC provide an orthoK lens?

"mold" for treatment

What is the function of the BC of an orthoK lens?

flattens cornea to correct myopia

Is the BC of an orthoK lens adjusted to change the fit of the lens?

No

You have to make ____mm steps when changing the BC of an orthoK lens

0.1

A patient's RE is -3.00-0.50x180. Refractive sphere is -3.00. Ks are 43.00/43.50 @ 090. What BC should be selected for this patient if fit into orthoK lenses?

-Goal is to correct the myopic refractive error of -3.00

-Then over correct by 0.50 for the Jessen factor

-Selected BC = 39.50D

Should we use the SE of an RX when deciding what BC to select for orthoK lens fitting?

No

Should we use the vertexed RX when deciding what BC to select for orthoK lens fitting?

Yes

A patient's RE is -3.00-1.00x180. Refractive sphere is -3.50. Flat K is at 44.00D. What BC should be selected for this patient if fit into orthoK lenses?

40.00D

Over 0.75DC of ATR toricity in a Rx will be a (easier/more difficult) orthoK fit

more difficult

Will it be more difficult to fit an orthoK lens that takes the BC below 38.00D?

Yes

A patient's RE is -4.00 Refractive sphere is -4.00. Flat K is at 41.00. What BC should be selected for this patient if fit into orthoK lenses?

36.50D

**this is a very flat cornea

When fitting orthoK lenses it will be easier to fit lenses with more (sphere/cylinder) power

sphere > cylinder

Would it be easy to fit this patient in orthoK lenses? -0.75-1.50x180

No

When should we adjust BC in an orthoK lens?

-Refractive error is not at plano

-Over refraction is not plano

0.1mm change in BC will create _____D change in power in an orthoK lens

0.50

On a standard design orthoK lens, what is the typical size of the optic zone?

6mm

Do some practitioners advocate for a less than 5mm optic (treatment) zone?

Yes -- seems to improve myopia control

What is the TARGET TREATMENT zone in an orthoK lens?

4mm

Return Zone (Pic)

Return Zone (Pic)

Return Zone Depth (Pic)

Return Zone Depth (Pic)

What is the return zone depth responsible for?

centration and applanation of the treatment zone

Return zone depth is another term for _____ of the lens

sagittal depth

You can make changes to the return zone depth in ____um steps

25

What is the most important part of determining the FIT of an orthoK lens?

return zone depth

What does the landing zone provide an orthoK lens?

amount of clearance

What is the landing zone of an orthoK lens measured in?

degrees, adjusted in 1º increments

The landing zone of an orthoK lens will contribute to ____um of sagittal depth

15

If an orthoK lens has MINIMAL EDGE CLEARANCE, what is the proper change that can be made to this lens?

Decrease the landing zone angle

If an orthoK lens has EXCESSIVE EDGE CLEARANCE, what is the proper change that can be made to this lens?

Increase the landing zone angle

Landing Zone Angle Measurements (Pic)

Landing Zone Angle Measurements (Pic)

NaFl Pattern when Landing Zone Angle is Too High (Pic)

**Minimal edge clearance; will want to decrease the landing zone angle

NaFl Pattern when Landing Zone Angle is Too High (Pic)

NaFl Pattern when Landing Zone Angle is Too Low (Pic)

**Excessive edge clearance alone is caused by Landing zone angle being too small (32); will want to increase the landing zone angle; tx zone clearance is affected by return zone depth and that needs changing too

NaFl Pattern when Landing Zone Angle is Too Low (Pic)

Landing Zone Just Right (Pic)

Landing Zone Just Right (Pic)

_____ of orthoK lenses is key for treatment success

sagittal depth

How to achieve centration with an OrthoK lens

change sag depth

What values should change in order to change sagittal depth of an orthoK lens?

RZD and LZA

Sagittal Depth Changes (Pic)

**original lens is well centered but has a huge bubble in the return zone and also has minimal edge clearance

Sagittal Depth Changes (Pic)

True or False:

A larger diameter will help an orthoK lens center better over the cornea

true

True or False:

There may be a laser marked ID on an orthoK lens

true

What does the laser marked ID indicate on an orthoK lens?

BC, RZD, LZA

OrthoK lenses are FDA approved for what powers?

-1.00 to -5.00

What is the required clinical data for fitting an orthoK lens?

-ocular surface examination

-refraction

-topography

-tomography

-WTW/HVID

You will also need to measure the patients ______ if using orthoK lenses for myopia control

axial length

Describe the astigmatism that is best corrected by an orthoK lens?

spec cyl = corneal cyl; r/o irregular cornea

How to select lens parameters in a CRT orthoK lens?

-flat K reading

-manifest sphere (pick from dispensing set)

-visible iris diameter

Can you use an online calculator to select lens parameters for a CRT orthoK lens?

Yes

Abiliti Online Calculator (Pic)

Abiliti Online Calculator (Pic)

If using serial topography to get K readings for orthoK lenses, what is the best approach?

Need at least 3 to make sure they are high quality and repeatable

Are the Pentacam measurements tear film dependent?

no

If you have a fitting set, can you empirically or diagnostically fit orthoK lenses?

Yes -- w/ a nomogram

We ALWAYS want to use a lens material for orthoK lenses with a Dk value over what #?

100

There is anecdotal evidence of there being a greater treatment effect with _____ Dk material such an Menicon Z

higher

How to initially assess the fit of an OrthoK lens?

-Instill proparacaine

-Apply lenses

-Check VA with the lenses on

-Check OR with the lenses on

-Assess the NaFl pattern

What should the OR be with the lenses on?

Plano

How to assess the fit of an orthoK lens?

-Centration

-Good edge lift

-3-4mm treatment zone

-Moderate tear film touch in the mid periphery

____ is the key to success with CRT orthoK lenses

Centration

True or False:

Lighting and pupil size will have an effect on vision in an orthoK lens

true

NaFl pattern and Thickness of OrthoK Lenses (Pic)

NaFl pattern and Thickness of OrthoK Lenses (Pic)

VA with each eye with orthoK lenses in should be ____

20/20

If we chose a +1.00 Jessen factor then the lenses we used will have a +____ power

+1.00

Despite looking like touch there is usually _____um apical clearance

< 10um

Fluorescein needs ____um to fluoresce

>20

True or False:

The slit lamp view is always how the lens fits with closed lids

False -- we need to see the topo/tomo after sleeping

How to know if lenses are OK to dispense?

-Fit is good

-Vision is good

-Comfort is acceptable

-Have patient perform A&R

-Go over care instructions

Can you also dispense soft lenses as needed if rx if higher?

Yes -- will not get full correction for higher REs overnight. For a -4.00D patient, consider sending -2.50, -1.50, -0.50 soft lenses home for the patient to try

What is the typical F/U schedule for orthoK lenses?

-Dispense visit

-1 Day

-1 week

-1 Month

-3 Month

-6 Month

-Annual