3_SCL+Fitting-Acc-Handout

What is included in the baseline examination for a new daily-wear soft contact lens wearer?

• Assess patient needs

• Perform comprehensive examination and fitting

• Dispense appropriate soft contact lenses or place order

• Provide insertion/removal (I&R) training

What happens at the dispensing visit for a new daily-wear contact lens wearer, and when is it scheduled?

• Scheduled as needed, typically 1–2 weeks after baseline

• Assess fit and vision of lenses

• Reinforce insertion/removal training

• If adjustments are needed: re-order lenses and schedule a new dispense

What is the purpose of the 1–2 week follow-up after successful dispense for a new contact lens wearer?

• Evaluate fit, vision, and comfort

• Ask about insertion and removal success

• If problems remain: adjust, re-order, and schedule another dispense visit

What is the longer-term follow-up schedule for a neophyte daily-wear contact lens patient?

• 6-month follow-up: only as needed (rare)

• Yearly exam:

  • Reassess needs

  • Perform comprehensive exam

  • Evaluate habitual lenses

  • Re-order or refit if needed

What is included in the baseline examination for a new extended/continuous wear contact lens patient?

• Assess patient needs

• Perform comprehensive examination and fitting

• Dispense appropriate FDA-approved extended wear soft contact lenses or place order

What occurs at the dispensing visit for a new extended/continuous wear lens wearer, and when is it scheduled?

• Scheduled as needed, 1–2 weeks after baseline

• Assess fit and vision of lenses

• If adjustments are needed: re-order and schedule a new dispense

What is the purpose of the 1-day follow-up in a new extended/continuous wear contact lens patient?

• Occurs after first overnight wear

• Scheduled the first morning after overnight wear

• Evaluate fit, vision, comfort, and corneal edema

• Ask about insertion and removal

• If needed: adjust, re-order, and schedule new dispense visit

What is the purpose of the 6-month follow-up for extended/continuous wear lenses?

• Long-term follow-up

• Done to assess long-term hypoxic changes to the cornea from overnight wear

• Reassess fit, vision, and comfort

What is included in the yearly examination for an extended/continuous wear contact lens wearer?

• Reassess needs

• Perform comprehensive examination

• Evaluate habitual lenses

• Re-order or refit as needed

What follow-up feature is especially important for extended/continuous wear compared with daily wear?

• Next-morning (1-day) follow-up after first overnight wear

• 6-month follow-up to monitor for corneal hypoxic changes/corneal edema

What is done at the yearly examination for a veteran daily-wear contact lens patient?

• Assess patient needs

• Perform comprehensive examination

• Evaluate habitual lenses

• Re-order or refit as needed

What is the follow-up plan for a veteran daily-wear patient if no modifications are needed at the yearly exam?

• No interim follow-up required

• Patient returns at the next yearly examination

What happens if modifications are needed for a veteran daily-wear contact lens patient?

• Dispensing visit scheduled 1–2 weeks after baseline/yearly exam

• Assess fit and vision of lenses

• If further changes are needed: re-order lenses and schedule new dispense

What is assessed at the 1–2 week follow-up after successful dispense in a veteran daily-wear patient?

• Evaluate fit, vision, and comfort

• Ask about insertion and removal

• If adjustments are needed: re-order and schedule new dispense visit

When are the 1-3 month and 6-month follow-ups used in veteran daily-wear contact lens care?

• 1-3 month follow-up: rarely needed

  • Used to assess lens adaptation, especially if concerns arose at dispense

• 6-month follow-up: rarely needed

What are the components of a prefitting/comprehensive exam before contact lens fitting?

• Typical routine exam procedures

• Contact lens (CL) history

• Measure corneal shape

• Perform manifest refraction (vertex if needed)

• Slit lamp exam, including eyelid eversion and tear film evaluation

• Binocular vision (BV) evaluation is important

What corneal shape measurements are important in a contact lens prefitting exam?

• Corneal curvature (Ks)

• Corneal asphericity

• Horizontal visible iris diameter (HVID)

• Corneal sagittal depth

What special exam steps may be needed during contact lens prefitting beyond a standard refraction/slit lamp exam?

• Vertex the manifest refraction if necessary

• Perform eyelid eversion at the slit lamp

• Evaluate the tear film

• Assess binocular vision, since BV issues can affect lens success

Why are tear film, eyelid eversion, and BV evaluation important in contact lens prefitting?

• Tear film affects lens comfort, stability, and vision

• Eyelid eversion helps detect lid/conjunctival findings that may affect wear

• BV evaluation identifies visual function issues that can impact contact lens success

At what types of visits can contact lens selection/fitting occur?

• Stand-alone visit

• Comprehensive exam

• Dispensing visit

What lens care counseling is required during contact lens selection?

All lenses except daily disposables require a care/cleaning plan

What is a key difference in patient education between daily disposable lenses and other contact lenses?

• Select modality: daily wear, extended wear, or continuous wear

• Select replacement/disposal schedule

• Select soft lens brand / base curve radius (BCR) based on sagittal depth

• Determine lens power

What are the main contact lens modalities a clinician may choose from?

• Daily wear

• Extended wear

• Continuous wear

What replacement/disposal schedules are available for soft contact lenses?

• Daily

• Weekly

• Every 2 weeks

• Monthly

• Quarterly = every 3 months

• Annually

How is a soft lens brand / BCR selected during contact lens fitting?

Chosen based on sagittal depth to help achieve an appropriate fit

What is important to remember about power determination/selection in contact lens fitting?

The needed lens power may not always be available in inventory

What is the difference between modality and replacement schedule in contact lens selection?

• Modality = how the lens is worn (daily, extended, continuous wear)

• Replacement schedule = how often the lens is replaced/disposed (daily, biweekly, monthly, quarterly/3 months, etc.)

What are the main steps in assessing contact lens fit after selecting a lens?

• Determine if the lens must be ordered or is available

• Apply lenses to the eye

• Allow appropriate settling time

• Assess fitting relationship

• Check visual acuity

• Perform over-refraction

• Do surface evaluation at comprehensive and progress checks

What is evaluated in the fitting relationship assessment of a contact lens?

• Centration

• Coverage

• Movement

• Push-up test

Why is settling time important before assessing contact lens fit?

• Allows the lens to stabilize on the eye

• Prevents judging fit too early before the lens reaches a more representative position/movement pattern

What is the purpose of checking visual acuity and doing an over-refraction during contact lens fitting?

• Visual acuity: assesses how well the patient sees in the trial lens

• Over-refraction: refines residual refractive error to determine whether a power change is needed

When should surface evaluation be performed in contact lens fitting?

• At comprehensive exams

• At progress checks/follow-up visits

What are the steps in a contact lens dispensing exam?

• Check entrance visual acuity with habitual correction

• Take a brief interval history (ask about any changes)

• Assess lens fit

• Decide whether to dispense/educate or reorder and repeat dispensing exam

What should be reviewed at the start of a dispensing exam?

• Entrance VA with habitual correction

• Brief history to identify any changes since the previous visit

• Fitment assessment

What are the two possible outcomes of a contact lens dispensing exam?

• Educate patient and send home to try lenses

  • May require insertion and removal (I&R) training

• Reorder lens and repeat dispensing exam

When can you proceed with dispensing soft contact lenses to the patient?

Proceed if:

• Acuity is acceptable

• Fit is acceptable

• Over-refraction is minimal

What should be done if the dispensing exam shows good fit/vision but a slight power change is needed?

• You may send the patient home with the lenses

• Reorder a slight power update if needed

What should be done if lens acuity, fit, or over-refraction is not acceptable at the dispensing visit?

Start re-fitting rather than dispensing the current lenses

How long should a soft contact lens dispensing visit usually take?

20 minutes or less

What questions should be asked about a patient’s contact lens type and wearing history?

• What lens(es) are worn?

• How many years has the patient worn them?

• What is the wear schedule?

• What is the disposal/replacement schedule?

What compliance-related questions are especially important when taking a contact lens history?

• How often do you sleep in your contact lenses?

• What solutions do you use?

• Do you wash your hands before handling lenses?

What are the main domains to cover in additional contact lens history questions?

• Lens type and duration of wear

• Wear and replacement schedule

• Sleeping in lenses

• Lens care solutions

• Hand hygiene

• Lens case hygiene

How is central corneal curvature measured during contact lens fitting?

• Keratometry (“Auto Ks”)

• Corneal topography (Ks and Asphericity)

What is HVID, and how is it measured?

• HVID = Horizontal Visible Iris Diameter

• Can be measured with a PD ruler or corneal topography

• WTW (white-to-white) is generally greater than HVID

What are the typical average corneal curvature and astigmatism values used in contact lens fitting?

• Mean corneal power/curvature: 43.50 ± 1.7 D

• Mean corneal astigmatism: 0.9 ± 1.1 D

What is the typical HVID in contact lens fitting?

• Average HVID = 11.50 mm

• Typical range: 10 to 13.5 mm

Why is corneal asphericity important in contact lens fitting?

• Corneal asphericity affects corneal sagittal depth (sag)

• A cornea that is unusually spherical / less aspheric has deeper sag than a more aspheric cornea

• These eyes are often more difficult to fit, especially with soft contact lenses

What fitting problem can occur if the cornea is not very aspheric (more spherical / barely flattens toward the periphery)?

• The cornea has a deeper sagittal depth

• This can make soft contact lens fitting more difficult

Why is corneal asphericity not always routinely available in clinic?

• It usually requires corneal topography

• It is not commonly measured directly in routine clinic without topography

What is the difference between axial maps and tangential maps on corneal topography?

• Axial maps: best represent the optical characteristics of the cornea; commonly preferred in refractive surgery

• Tangential maps: represent true/local curvature better and provide better peripheral shape information; preferred in contact lens practice

Which corneal topography map is generally preferred in contact lens practice, and why?

Tangential map: Better reflects true curvature data and peripheral corneal shape, which is important for contact lens fitting

What is corneal sagittal depth?

• The height/depth of the cornea over a specified chord diameter

• It helps describe overall corneal shape in a way that is useful for contact lens fitting

What is the average corneal sagittal depth?

Mean sagittal depth ≈ 2.74 mm

Why is corneal curvature alone not enough for contact lens fitting?

• Corneal curvature alone does not fully explain how deep or shallow a contact lens must be to fit well

• Sagittal depth gives a better overall description of fit requirements

What clinical outcomes are associated with sagittal depth in contact lens fitting?

• Adverse events

• Discomfort

• Contact lens dropout

What factors determine corneal/contact lens sagittal depth?

• Corneal curvature

• HVID

• Asphericity

Why is sagittal depth clinically important in soft contact lens fitting?

• Helps estimate how deep/shallow the lens fit should be

• Better predicts fit than K readings alone

• Relevant to comfort, safety, and long-term lens success

What is the sagittal depth formula for a spherical surface in contact lens fitting?

s = r − (r² − h²)^(1/2)

Where:

• s = sagittal depth

• r = radius of curvature

• 2h = chord diameter

Why are contact lenses described as “thick lenses” in the context of sagittal depth?

Because the sagittal depth is short relative to the chord diameter

What important limitation does the basic sagittal depth formula have?

It is simplified and does not account for asphericity

If a soft contact lens does not match the cornea, what two lens parameters can be changed to alter sagittal depth?

• 2h = lens diameter / OAD

• r = lens curvature / BCR

Why does changing soft lens sagittal depth often require choosing a different brand?

• Because soft lens manufacturers often offer only one fit within a given brand/lens design

• If more sagittal depth modification is needed, clinicians often switch to a different brand

What is the clinical goal of sagittal depth in contact lens fitting?

• To align the contact lens to the cornea

• Matching lens sagittal depth to corneal sagittal depth helps achieve an appropriate fit

What is an important limitation of AS-OCT when measuring sagittal depth with a contact lens on the eye?

• The AS-OCT does not know a contact lens is on the eye

• The image is not adjusted for the lens refractive index

• This can affect interpretation of the upper image / lens-related measurement

How should sagittal depth measurements be oriented on AS-OCT if you are not measuring along the first surface?

Keep measurements parallel to the scanning beam

What are the two technical notes for measuring corneal sagittal depth on AS-OCT?

• AS-OCT images are not corrected for the contact lens refractive index

• If not measuring from the first surface, keep the measurement parallel to the scanning beam

What was a common finding for patients who did not have a good fit with the contact lens?

Shallower-than-average corneal sagittal depth

How is corneal sagittal depth related to contact lens dropout?

• Discontinued wearers were more often found at the extremes of corneal sagittal depth

• Dropout was associated with both shallower and deeper corneal sagittal depths

• Current wearers were more often found in the middle of the population distribution

Why can Ks and HVID alone fail to explain contact lens dropout?

• A patient may have typical K readings and typical HVID, yet still have abnormal overall corneal shape

• Asphericity/sphericity can change sagittal depth even when Ks and HVID look normal

What symptom were common in discontinued contact lens wearers?

Discomfort symptoms, especially feeling like they had dry eye while wearing contact lenses

Why might some doctors intentionally avoid prescribing small amounts of cylinder in glasses for a spherical contact lens wearer?

• For low cylinder amounts (about 0.25 to 0.50 D)

• Some doctors leave it out so the patient can switch more easily between glasses and spherical contact lenses

What are the main options for measuring vertex distance?

• Phoroptor/phoropter vertex gauge

• Gauge on trial frame

• Distometer

What are the drawbacks of the phoroptor/phoropter vertex gauge?

• Difficult to read

• Difficult to monitor patient during refraction to make sure the distance stays consistent

Where is the gauge on a trial frame located, and what is its limitation?

• Located on the side of the trial frame

• Less precise than a distometer

Which method is generally more precise for measuring vertex distance: trial frame gauge or distometer?

• Distometer is more precise

• Trial frame gauge is less precise

What is the general procedure for measuring vertex distance with a distometer?

• Place refraction in trial frame

• Perform a binocular sphere check

• Have the patient close their eyes

• Measure vertex distance with the distometer

• Add 1 mm unless that correction is already built in by the manufacturer (to account for eyelid thickness)

What major decisions must be made when selecting a contact lens disposal schedule and modality?

• Choose modality: Daily Wear (DW) vs Extended Wear (EW)

• Consider oxygen needs

• Choose replacement schedule: daily disposable vs planned replacement

• Consider tints and handling

What factors should guide the choice between daily wear vs extended wear and different replacement schedules?

• Oxygen needs

• Desired wear modality (DW vs EW)

• Replacement frequency (daily, 1–2 week, monthly, quarterly)

• Patient factors like handling and preference for tints

What is the general relationship between replacement frequency and contact lens outcomes?

• More frequent replacement = better vision, comfort, and ocular health/ the more frequently a lens is replaced, the fewer complications occur

What are the advantages of daily disposable contact lenses?

• Lowest overall complication rate

• Lowest level of deposition

• Often associated with good vision and sometimes improved comfort

• Fewest unscheduled visits (less chair time)

What is the main drawback of daily disposable lenses?

Cost may be difficult for some patients

Why are daily disposables often preferred clinically?

• Fewest unscheduled visits

• Great vision

• Sometimes improved comfort

• Fewer overall complications

• Less deposition

What is the main risk with extended or continuous wear CL?

They have the highest overall complication rate.

How do complication rates of disposable EW lenses compare with conventional (non-disposable) EW lenses?

• The complication rates are approximately the same

• Simply making the lens disposable does not eliminate the higher risk of EW

Why do many patients want extended wear, and why is this clinically important?

• Many patients want EW because they are bad at insertion and removal

• This is important because convenience may drive demand despite increased risk

Why do many clinics require a consent form/policy for extended wear contact lenses?

• Because fitting a patient in EW involves extra risk

• Most practices use a consent form to document risk discussion and patient understanding

How is sagittal depth used when selecting a soft contact lens (SCL) brand or base curve radius (BCR)?

• For soft contact lenses, clinicians often estimate the patient’s sagittal depth

• This helps predict which lens design/brand will fit best

How should you use K readings + HVID when choosing an initial soft contact lens?

Use central corneal curvature (K) and HVID to estimate whether the patient likely needs a shallower or deeper lens

What corneal features suggest a shallower soft lens vs a deeper soft lens?

• Shallower lens: flatter K + smaller HVID

• Deeper lens: steeper K + larger HVID

How is soft contact lens power determined?

• Based on the vertexed manifest refraction

• Use spherical or spherical equivalent for low cylinder amounts

• Use a toric lens when cylinder is significant

When is a toric soft contact lens usually needed?

• Typically when cylinder is ≥ 1.00 DC

• Often considered starting at ≥ 0.75 DC

How should the trial lens power be chosen after calculating the predicted CL power?

• Choose the trial lens closest to the predicted power

• Remember that higher powers may only be available in 0.50 D steps

What are the characteristics of an ideal soft contact lens fit?

• Produces good, stable vision

• Is comfortable

• Is wearable for practical periods of time

• Causes minimal physiological response

What does an excessively tight soft contact lens fit risk causing?

• Increased physiologic response

• Can lead to irritation and inflammation

Why is tear exchange important in a soft contact lens fit?

• Tear exchange helps remove debris/inflammatory material from under the lens

• However, tear exchange is difficult to achieve with soft lenses

How much tear exchange occurs with blink in even a “good” soft contact lens fit?

• Very little / almost none

• Roughly ~2% with blink

• High-yield implication: debris and inflammatory products can remain under the lens

What is the minimum settling time before assessing a newly applied soft contact lens?

• Allow at least 10 minutes of settling time

• During this time, check whether the lens is grossly too small or too tight

• Record the fit assessment after the lens settles

Why may a soft contact lens fit need reassessment after 3 to 4 hours or 1 to 2 weeks?

• Soft lenses dehydrate on the eye over time

• Because of this, the fit may change/tighten after longer wear

• Especially important if the patient has poor tear volume

How does poor tear volume affect soft contact lens fit over time?

• Soft lenses can dehydrate on the eye

• With poor tear volume, the lens fit may tighten over time

What are the 3 main things assessed when evaluating a soft contact lens fit?

• Coverage of the cornea/limbus

• Centration over the cornea

• Movement with blink / eye movements