9. Keratoconus - Advanced Contact Lenses Fall 2026

What is keratoconus?

primary, bilateral, typically asymmetrical corneal ectatic disease characterized by progressive steepening of the cornea and a cone-apex centered thinning

What are the major diagnostic criteria for clinical keratoconus?

-Abnormal steepening of the anterior/posterior corneal surface

-Abnormal corneal thickness profile

-Classic slit lamp biomicroscopic signs

-Decline in corrected DVA

What is the definition of subclinical keratoconus?

Topography or tomography changes but no slit lamp signs, considered progressive

What is the definition of Forme Fruste keratoconus?

No topography or tomography signs, normal cornea, keratoconus in contralateral eye; not progressive

What is the clinical significance of keratoconus?

-Decreased quality of life

-Psychological impact

-Decreased Productivity

What is the incidence of keratoconus?

289/100,000

What age is keratoconus most prevalent?

20-29

Can keratoconus be diagnosed in pediatric patients?

Yes

Worldwide Incidence and Prevalence Map (Pic)

Worldwide Incidence and Prevalence Map (Pic)

Why is the incidence % of keratoconus increasing?

Enhanced diagnostics and cross linking; more immigrant population

What are the major risk factors for keratoconus?

-Allergy

-Atophy

-Eye Rubbing

-Asthma

-Down Syndrome

-Hashimoto thyroiditis, Inflammatory skin conditions, sleep apnea

What is the #1 risk factor for keratoconus?

eye rubbing

What is the evidence that supports genetic predisposition to keratoconus?

1) High incidence with monozygotic twins vs dizygotic twins

2) Positive fam hx as high as 25%

3) Consanguineous couples 4x more likely to have children with keratoconus

If you have a relative with keratoconus, you are at a _____x increased risk of developing keratoconus

15-67

Are the genes for keratoconus only on one chromosome?

No -- associations with keratoconus have been seen on loci of 16 chromosomes

Keratoconus is a _____ disease

multifactorial

Are there multiple genetic factors that play a role in keratoconus?

Yes, but may also require mechanical factors (eye rubbing or eye compression)

Keratoconus may be a ____ of diseases

spectrum

What is the benefit of genetic testing for keratoconus patients?

-Can try to estimate the risk of keratoconus

-Do NOT recommend this test if NOT considering refractive sx

In the 2025 Census of Keratoconus, what was found in keratoconic eyes?

Ocular surface immune cells; PMNs; NKs higher in keratoconics

What are the valuable tools for diagnosing keratoconus?

-Clinical hx

-Slit lamp

-VA

-Corneal Imaging

What are the changes of keratoconus that can contribute to lower VA?

-Refractive error changes

-Cylinder

-Reduced BCVA

What are the corneal imaging that are done for patients with keratoconus in order to dx the disease?

-Topography

-Tomography

-Epithelial Thickness

-Hysteresis

-Aberrometry

Histopathology - Normal Epithelium vs Keratoconus and Scleral Lens (Pic)

Histopathology - Normal Epithelium vs Keratoconus and Scleral Lens (Pic)

What happens to the epithelium of the cornea with keratoconus?

-Decrease in basal cell density

-Irregular cellular arrangement

-Iron deposits in the basal layer of the epithelium

The epithelium of the cornea may ____ over the apex of the cone, and ____ at the base of the cone

thin; thicken

Epithelial Thickness Maps (Pic)

Epithelial Thickness Maps (Pic)

What can happen to Bowman's layer in keratoconus?

-Breaks in Bowman's

-Allows stromal collagen to move anteriorly

-Some epithelial tissue moves posteriorly

What happens to the stromal layer of the cornea in keratoconus?

-Fewer lamellae

-Rearranged lamellae

-Thinning of the stroma

-Lamellae split into bundles, loss of anterior lamellae, lateral shifting

-Vogt Striae in the posterior stroma/Descemet

What happens to Descemet membrane in keratoconus?

-Breaks occur under tension

-Hydrops

What is hydrops?

Breaks in Descemet's membrane causing aqueous to flow into the stroma and cause stromal edema

What % of patients with KCN will get hydrops?

1-3%

What is the appearance of corneal hydrops with KCN?

-Slit lamp diffuse stromal opacification

-Conj injection

-Patients present with acute pain and loss of vision

What happens in KCN eyes that get hydrops?

Results in scarring after deturgescence

Hydrops usually resolves in ______

2-4m

What is the proper management for corneal hydrops?

-hypertonic solution

-corticosteroids

-cycloplegic

-antibiotic PRN

-Intracameral perfluoropropane

What is the effect of Intracameral perfluoropropane on corneal hydrops?

Faster resolution but no difference in visual outcome

What should you look for on topography when suspicious for KCN?

Look for symmetry by making horizontal and vertical line through the topography image

What are the types of topography that can be taken?

-Axial and Tangential Maps

-Elevation Maps

Most topographers use _____ rings

Placido

Topography measurements (are/are not) tear film dependent

are

In order to get accurate readings for a topographer, what must you do?

serial topography

What are the methods for tomography readings?

-Pentacam

-OCT tomography

Topography vs Tomography (Pic)

Topography vs Tomography (Pic)

Belin/Ambrosio Enhanced Ectasia Display (Pic)

Belin/Ambrosio Enhanced Ectasia Display (Pic)

Tomography Finding an Early Cone (Pic)

Tomography Finding an Early Cone (Pic)

Aberrometry (Pic)

Aberrometry (Pic)

Aberrometry (Pic)

Aberrometry (Pic)

How is keratoconus related to corneal hysteresis?

Focal reduction in elastic modulus of the cornea

Is there a SINGLE classification system for keratoconus?

No -- could not agree on a single classification system

Global Consensus on Keratoconus is that dx requires a change in ____ of the factors in attached pic

2

What are the factors that constitute a dx of keratoconus (need 2)?

-Steepening of anterior corneal surface

-Steepening of posterior corneal surface

-Thinning and/or an increased rate of corneal thickness change

-Worsening of VA

True or False:

We are better at monitoring keratoconus when we factor in multiple measurements and tests

true

What are the possible management options for keratoconus?

-Specs

-CLs (soft, hybrid, corneal GP, scleral, piggy back)

-Sx

What types of sx are possible management options for keratoconus?

-Corneal implants (ICRS, CTAK)

-Corneal ablation

-Conductive keratoplasty

-CXL

-Transplants

-IOL

When are spectacles a good management option for keratoconus?

-mild keratoconus

-CL intolerant patient

Scleral Lens Vault (Pic)

Scleral Lens Vault (Pic)

Higher Order Aberrations with Sclerals (Pic)

**Reverses the direction of HOAs but aberration correction is possible in scleral lenses

Higher Order Aberrations with Sclerals (Pic)

Visual Performance After HOA Correction (Pic)

Visual Performance After HOA Correction (Pic)

VA will improve with _____ contrast in KCN patients

reverse

What are the possible surgical management options for patients with KCN discussed in this module?

-Conductive keratoplasty

-CXL

-TPRK

-ICRS

-CAIRS/CTAK

-PK/DALK

Conductive Keratoplasty (Pic)

**You have to do crosslinking with this procedure or it will immediately progress post op

Conductive Keratoplasty (Pic)

What is corneal crosslinking?

-Debride the epithelium

-Saturate the stroma with riboflavin; 1 drop q5min for 30min

-Expose cornea to 3mW/cm^2 irradiance for 30min

Compare Maximum K w/ and without Corneal Crosslinking (Pic)

**12 months post CXL, Max K is much lower than control group

Compare Maximum K w/ and without Corneal Crosslinking (Pic)

Stability of CXL over 7 Years (Pic)

Stability of CXL over 7 Years (Pic)

Describe how Epi On CXL is now performed

Remove dextran, May use iontophoresis to encourage riboflavin into the stroma; chemically weaken he epithelial tight junctions

What is the benefit to Epi-On CXL?

Less Adverse events (corneal scarring, haze, infiltrates, HSV)

Do Epi on and Epi off CXL halt the progression of the disease?

Yes

Can CXL be done in kids?

Yes -- no adverse events were reported during the trial in 10-16 year olds

Can OH ODs perform Epi ON CXL?

Legally yes but the manufacturer is not making it available to ODs at this time

What are corneal Intacs?

Polymer intrastromal corneal ring segment

What is CAIRS?

Corneal allogenic intracorneal ring segments that are preserved pre-shaped corneal ring segments from dehydrated donor corneas

What is CTAK?

Corneal tissue addition keratoplasty, Preserved tissue, Capable of being shaped with a femtosecond laser

CAIRS with prompt ___ had more flattening effect and improved aberrations

CXL -- a stiffer cornea will resist flattening

Corneal Tissue Addition for Keratoconus (CTAK) (Pic)

Corneal Tissue Addition for Keratoconus (CTAK) (Pic)

Rates of PK are (increasing/decreasing). why?

Decreasing -- crosslinking is preventing progression and sclerals are allowing for more complicated lens fits