8. Irregular Cornea - Advanced Contact Lens Fall 2026

What is irregular cornea caused by?

-Keratoconus

-Pellucid Marginal Degeneration

-Post PK

-Post Refractive Surgery

-Corneal/Ocular Trauma

What is keratoconus?

Progressive, asymmetrical disease of the cornea characterized by steepening and distortion, apical thinning, and central scarring of the cornea

What are the symptoms of keratoconus?

-visual distortion

-high myopia

-unstable astigmatism

What are the signs of keratoconus?

-irregular astigmatism

-Flesicher's ring

-stromal thinning and scarring

-corneal steepening on topography

-Vogt striae

-Munson sign

-Charlaeux sign

Types of Topography (Pic)

Types of Topography (Pic)

Conical Corneal Protrusion (Pic)

Conical Corneal Protrusion (Pic)

Corneal Steepening on Topography (Pic)

Corneal Steepening on Topography (Pic)

What is the location of the steepening that is consistent with keratoconus?

Inf corneal steepening

Corneal Stromal Thinning on SLE with Keratoconus (Pic)

Corneal Stromal Thinning on SLE with Keratoconus (Pic)

Anterior Stromal Scars on Cornea with Keratoconus (Pic)

Anterior Stromal Scars on Cornea with Keratoconus (Pic)

What is a Fleischer ring that is present with keratoconus?

Hemosiderin deposit in the basal epithelium of the cornea at the base of the cone

A Fleischer ring can be enhanced with ____ filter on slit lamp

cobalt blue

What are Vogt Striae that are common with keratoconus?

Stress lines that run parallel with the axis of the cone in posterior stroma

With gentle pressure, what happen to Vogt Striae?

disappear with gentle pressure

What is a Munson sign that is characteristic of keratoconus?

V shaped lower lid conformation in downgaze

What is a Charleaux sign that is common with keratoconus?

Oil droplet appearance with retroillumination

What are corneal hydrops?

Breaks in Descemet membrane causing aqueous into the stroma (stromal edema)

Corneal hydrops occurs in what % of keratoconic eyes?

3%

What is the appearance of corneal hydrops on SLE?

Diffuse stromal opacification, conj injection

What does corneal hydrops result in?

Scarring after deturgescence

Corneal Hydrops (Pic)

Corneal Hydrops (Pic)

What will probably be needed after corneal hydrops?

PK

What is the treatment plan for corneal hydrops?

-Palliative and decrease sequelae

-Topical antibiotics

-Cycloplegics and topical NSAIDs

-Hypertonic solution (Muro 128)

-Steroid topical medication

-Bandage CL

-Pneumatic Descemetopexy

-Penetrating Keratoplasty

What is a Pneumatic Descemetopexy as a treatment for corneal hydrops?

AC air or gas bubble tamponade

Does hydrops d/t keratoconus take a long time to heal?

Yes

There is emerging evidence for what treatment for corneal hydrops?

-Losartan (0.8 mg/mL)

Works to decrease myofibroblast production following injury which help with remodeling and create fibrosis

First optometry, multi center study funded by the NIH. Lasted 8 years

Collaborative Longitudinal Evaluation of Keratoconus (CLEK)

What was the purpose of the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) study?

Does flat fitting a cone lead to apical scarring?

In the CLEK study, what was the most common management of keratoconus?

Corneal GPs

What did the CLEK study look at for keratoconic patients?

VA, refraction, Ks, slit lamp, photography, NaFl patterns

What is FDACL defined by the CLEK study?

First Definite Apical Clearing Lens

What was the avg age of participants in the CLEK study?

39.3

____% of participants in the CLEK study DID NOT have a PK

90

_____% of participants in the CLEK study WORE GPS

74

_____% of patients in the CLEK study had a fam hx of keratoconus

14

____% of patients in the CLEK study reported a hx of eye rubbing

50

88% of GP fits in the CLEK study appearance?

Apical touch

What was the avg baseline fit BC in the CLEK study?

Average BC was 2.86D flatter than FDACL

(Steeper/flatter) corneal curvature increased risk of scarring by 28%. per diopter

Steeper

There is a slow decrease in (high/low) contrast VA wth keratoconus as found in the CLEK study?

both

There was a ____D/year change in FDACL

0.18

____% of participants in the CLEK study had a change of 3D or more

25

As found in the CLEK study, what were the risk factors for corneal scarring in keratoconic patients?

1) Age < 20yo

2) FDACL > 52D

3) CL Wear

4) Corneal Staining

As found in the CLEK study, there was a _____% increased risk of scarring if an eye wears a corneal GP

62

Summary of CLEK Study: When there is an increase in corneal curvature, there is an (increase/decline) in scores for dependency, mental health, and ocular pain

decline

Summary of CLEK Study: Where there is a decrease in VA, there is a decrease in what other factors?

-independency

-driving

-mental health

-near activities

What are the goals of irregular cornea fitting?

-maximize vision

-maximize comfort/wear time

-minimize corneal compromise

How can we maximize vision for irregular corneas?

-Use of gas permeable lens with rigid material

-Provide a regular surface for vision because tears will fill in behind the GP lens

How to minimize corneal complications when fitting lenses for irregular corneas?

-Fit to maintain ocular health

-Avoid lens binding, dimple veiling, epithelial disruption

-Avoid corneal staining which leads to corneal scarring

When would a soft toric be OKAY to fit on a patient with keratoconus?

If specs provide adequate vision by high cyl is difficult to adapt to

Due to the steepness of the cornea with keratoconus, a soft lens edge may be too flat resulting in ____ of the lens edge

fluting

Lens ____ and _____ may not be consistent when fitting a soft toric lens on a keratoconic eye

rotation; stability

Soft Toric Lens Fluting with Keratoconus (Pic)

Soft Toric Lens Fluting with Keratoconus (Pic)

What are a better soft lens options for patients with keratoconus?

Specialty Soft Keratoconus Lenses

What are the custom changes that can be made to a soft CLs to better fit keratoconic patients?

-Increase center thickness for rigidity

-HEMA lens materials

-Increased thickness will induce a tear lens and correct some irregularity

What are the custom soft lenses that are for keratoconic patients?

-FlexLens Tri-Curve Keratoconus Lens

-NovaCone by Alden

-Kerasoft IC

Are spherical GPs an option for patients with keratoconus?

Yes -- fit from the spherical fitting set and parameters can be custom modified

What Spherical GP lenses will best fit a keratoconic cornea based on the CLEK lens set?

-Steep base curves

-Small optic zone

-Large peripheral widths (can add a 4th curve)

-Parameters are custom modified

CLEK Study Lens Set for Fitting Keratoconic Patients (Pic)

CLEK Study Lens Set for Fitting Keratoconic Patients (Pic)

What is the benefit of fitting keratoconic patients in a proprietary KCN lens design?

-Can change BC, OAD, Power and set Peripheral Curves

-Can have multiple base and peripheral curves

-Often use aspheric back curves for fitting

What is a hybrid lens?

GP optic zone with a soft HEMA skirt

When would you fit a keratoconic patient in a hybrid lens design?

Intolerant to GPs, but need GP optics

How to fit a keratoconic patient in a hybrid CL?

-Select GP base curve to fit the cornea

-Select a soft skirt BC for lens movement

-Evaluate with high molecular weight NaFl

What is the option of "piggybacking" lenses for patients with keratoconus?

GP lens on top of a soft contact lens

What is the benefit of piggybacking soft and hard GP lenses?

Soft lens will help with comfort, lens saturation, and GP edge problems

How to fit the soft lens when piggybacking with RGP for keratoconic patients?

Preferably high Dk SiHy material with a low modulus

You can use a ___ or ____ lens for better GP centration on inferiorly steep cornea

plus; minus

Does the soft lens power contribute significantly to the overall system?

No

When looking at the overall fit of a piggyback (soft and RGP), what should you look for on the soft CL?

Look for soft CL lens rotation, movement, and avoid edge fluting

SCL w/ RGP (Pic)

SCL w/ RGP (Pic)

Soft Lens Power on Surface Curvature Map (Pic)

**-6 power will relatively flatten the cornea compared to a +6.00 lens

Soft Lens Power on Surface Curvature Map (Pic)

BC Radius and Power of a Piggyback System (Pic)

**flatter lens = lower the power

BC Radius and Power of a Piggyback System (Pic)

What measurement should you take over a soft lens to determine the BC of the GP to use in a piggyback system?

Keratometry

True or False:

In a piggyback system, a high plus or minus soft lens can change the front curve

true

What is the avg size of a intralimbal GP lens?

10.8-11.2mm OAD with large optic zones

A (larger/smaller) diameter lens will center better in a patient with keratoconus?

larger

With pellucid marginal degeneration, why would we want to use a larger lens diameter?

vault over the inferior steepening of the cornea

With Post PK patients, what will happen if you use a larger lens diameter?

Large optic zone to vault over the graft junction

What is the avg diameter of a scleral lens?

18-22mm

Where does a scleral lens rest?

on the conjunctiva

What is the benefit of a scleral lens?

The GP optics will vault over the entire cornea

What is a scleral lens filled with?

Non-preserved saline

What are the features of a KERATOCONIC corneal lens (switching off of scleral lenses)?

-Small diameter (8-9.8mm)

-Steep base curve

-High minus power

The steeper a corneal lens, the (smaller/larger) the diameter of the lens

smaller

Can the base curve of a corneal lens for keratoconus be aspheric or spherical?

Yes

What is "3 Point Touch" referring to when fitting corneal GP lenses for keratoconus?

an optimal Rigid Gas Permeable (RGP) contact lens fitting technique for keratoconus where the lens makes light contact at three specific zones to distribute weight and maintain corneal health

How do you initially select a BC when fitting a corneal GP for a keratoconic patient?

-Depends on the brand

-May be slightly steeper than avg flat K and steep K

-May be closer to the steep K

If you select an inital BC of a lens that has pooling, what would be the best next step in this fitting process?

Fit 0.50-1D flatter

What are we trying to find when fitting corneal GP lenses?

First definite apical clearing lens (FDACL)

How is the base curve fit on corneal GP lenses for keratoconus?

-Differs with each lens design

-Most often fit slightly steeper than the avg of the flat and steep K

The back curve of a corneal GP has to fit the curvature of the ____ portion of the cornea

steep

The back curve of a corneal GP has to fit the curvature of the steep portion of the cornea, but also needs to be fit ______ in the mid periphery of the cornea

flatter

The change in curvature between the apex and flatter periphery is ____ than that of a normal cornea

greater

Describe an aspheric base curve of a corneal GP

Steep central that flattens very quickly

Most corneal GP lenses come in ____mm steps of BC change

0.1

What is apical clearance?

Lens fit steep with definite apical clearance and pooling over the steepest part of the cornea

Why do we want to fit under the philosophy FDACL?

Weight of the lens will be on the mid-peripheral cornea and possibly seal off at the optic zone

Often, how many curves are necessary for the fast rate of relative corneal flattening in keratoconic patients?

3-4

In keratoconic patients, we should make the peripheral curves a little (wider/narrower) than normal for slightly increased edge clearance and to prevent seal off of the lens to the cornea

wider

What lens material should we use for GP lenses when fitting keratoconic patients?

-OK to use any GP material

-Consider something between 30-60Dk