This document discusses ectatic disorders of the cornea, focusing on keratoconus. It defines keratoconus as a non-inflammatory thinning of the cornea that results in a protrusion and irregular astigmatism. The document covers the cascade hypothesis of oxidative damage in keratoconus pathogenesis, classification systems for keratoconus severity, signs and symptoms, and non-surgical management approaches like spectacles, contact lenses, and RGP fitting philosophies. The goal of management is to eliminate irregularities and provide optimal vision correction while minimizing further corneal damage.

1. Ectatic disorder of Cornea
“Keratoconus”
Prepared by:
Santosh Chhetri
Master in Clinical Optometry (II Batch)
Moderator:
Dr. Rachana Singh

2. Introduction Cornea Ectasia
Keratoconus
 Introduction
Cascade Hypothesis
Classification
Management
 Take home message

3. “Ectasia” as defined in most medical dictionaries refers
to a dilation or distention of a tubular structure. *
“Ectasia progression” is defined by a consistent change
in at least 2 of the following parameters :
1. Steepening of the anterior corneal surface
2. Steepening of the posterior corneal surface
3. Thinning and/or an increase in the rate of corneal
thickness change from the periphery to the thinnest
point.”*
Gomes JA, Rapuano CJ, Belin MW, Ambrósio Jr R. Global consensus on keratoconus diagnosis. Cornea. 2015
Dec 1;34(12):e38-9.
Corneal Ectasia

4. As opposed to “thinning disorders” the following are
classified under “ectatic diseases”
Keratoconus
PMD
Keratoglobus
Postrefractive surgery progressive corneal ectasia
Gomes JA, Rapuano CJ, Belin MW, Ambrósio Jr R. Global consensus on keratoconus diagnosis. Cornea. 2015 Dec
1;34(12):e38-9

5. Keratoconus

6. Introduction
Non-inflammatory, progressive thinning of the cornea that results
in apical protrusion (ectasia) resulting in a high degree of irregular
myopic astigmatism with observable structural changes appearing
in later stages.
The prevalence of keratoconus varies widely depending upon the
geographic location and diagnostic criteria used*
The reported incidence of keratoconus is 1 in 2000 individuals.*
The reports of two surveys in the UK indicated a prevalence 4.4
and 7.5 times greater for Asian (Indian, Pakistani, and
Bangladeshi) subjects compared with white subject.*
 Gokhale NS. Epidemiology of keratoconus. Indian journal of ophthalmology. 2013 Aug;61(8):382
 Georgiou T, Funnell CL, Cassels-Brown A, O’Connor R. Influence of ethnic origin on the incidence of keratoconus and associated atopic diseases in Asian and
white patients. Eye (Lond) 2004;18:379–83
 11. Pearson AR, Soneji B, Sarvananthan N, Sandforth-Smith JH. Does ethnic origin influence the incidence or severity of keratoconus? Eye
(Lond) 2000;14:625–8
 Rabinowitz YS. Keratoconus. Surv Ophthalmol 1998;42(4):297–319.
 Edwards M, McGhee CN, Dean S. The genetics of keratoconus. Clin Exp Ophthalmol 2001;29(6):345–51.

7. Keratoconus and ectatic corneal diseases have been
recognized for more than 150 years.*
Posterior corneal elevation abnormalities must be
present to diagnose mild or subclinical keratoconus.*
 Krachmer JH, Feder RS, Belin MW. Keratoconus and related non inflflammatory corneal thinning disorders.
Surv Ophthalmol. 1984;28: 293–322.
 Rabinowitz YS. Keratoconus. Surv Ophthalmol. 1998;42:297–319.
 Gomes JA, Rapuano CJ, Belin MW, Ambrósio Jr R. Global consensus on keratoconus diagnosis. Cornea. 2015
Dec 1;34(12):e38-9.

8. No gender predisposition
More common in hot, dry climates
Zadnik K, Barr JT, Edrington TB, et al. Baseline findings in the Collaborative Longitudinal Evaluation of Keratoconus
(CLEK) Study. Invest Ophthalmol Vis Sci 1998;39(13):2537-46.

10. 1. Characterization of the abnormal matrix
The keratoconus corneas had decreased levels of
fibronectin, laminin, entactin, type IV collagen and type
XII collagen associated with the epithelial basement
membranes.
There were also increased levels of fibrosis-associated
extracellular matrices such as type III collagen,
tenascin-C, and fibrillin-1 in the regions of anterior
stromal scars and disrupted Bowman’s layer

11. 2.Enzyme and inhibitor abnormalities
Keratoconus corneas had elevated levels of gelatinase activity.
It is likely that keratoconus corneas have an imbalance
between the corneal MMP-2 and its inhibitors, tissue inhibitors
of metalloproteinases (TIMPs)
Keratoconus corneas have decreased levels of enzyme
inhibitors and increased enzyme activities that can degrade the
various extracellular matrices within the keratoconus corneas.
The inhibitor–enzyme imbalance undoubtedly plays a major
role in the stromal thinning and Bowman’s layer/basement
membrane breaks that are characteristic of keratoconus
corneas.

13. 3. Apoptosis in keratoconus corneas
The keratoconus corneas have increased apoptosis and
this phenomenon of cell death may be important in its
pathogenesis.
 Factors that cause apoptosis include chronic epithelial
cell damage, increased levels of LAR(of leukocyte
common antigen related protein) and decreased levels of
TIMP-1.

14. 4. Abnormal regulation and signal transduction
Keratoconus corneas have increased levels of Sp1, a
transcription factor that can down-regulate proteinase
inhibitor.
Phosphotyrosine phosphatase enzyme (LAR)(function
of the phosphotyrosine phosphatase is removal of the
phosphates from the tyrosine molecules) that was found
in keratoconus but lacking in normal corneas

15. 5. Oxidative damage in keratoconus corneas
Keratoconus corneas have increased oxidative damage
compared to normal .They lack the necessary enzyme
components (ALDH3, superoxide dismutase) to process the
reactive oxygen species that occur.
With an accumulation of the reactive oxygen species, there
is a resultant deposition of cytotoxic by-products
(malondialdehyde and peroxynitrites) that can damage the
corneal tissues.

19. Cascade Hypothesis – Oxidative Damage
OXIDATIVE DAMAGE
UVB
Atopy
Eye rubbing
Mechanical injury
CL wear (before or for
KC?)
Reactive O2 Species
(ROS)
¯ Antioxidant enzymes
ALDH3
Superoxide dismutase
Catalase

20. Enzymes in lipid peroxidation &/or nitric oxide pathways are
abnormal or defective
Oxidative & cytotoxic by-products
Various corneal proteins altered
Cascade of events
triggered:
Apoptosis
• Signaling pathway
altered
• ↑ enzyme activities
• Fibrosis
Cornea exhibits:
• Steepening
• ↑ astigmatism
• ↑ irregularity
• ¯ thickness
• Scarring
• Progressive changes
After Kenney & Brown,
2003
Eventually, may show:
• Vogt’s striae
• Fleischer’s ring
• Ruptures in Descemet’s
• Hydrops
• Munson’s sign
• ↑ nerve visibility
• Scissor retinoscopy reflex

21. Mechanical factors : Floppy eyelid syndrome ,eye
rubbing associated with atopy or vernal keratoconjunctivitis
Connective tissue disorders(Marfan syndrome, Ehlers–
Danlos syndrome).
Positive family history(The prevalence of keratoconus in
first degree relatives is 3.34%, which is 15–67 times higher
than the general population.)
Down syndrome(0.5-15% of patients)
Ethnic factors (eg, Asian and Arabian)

22. • Mild: <45 D
• Moderate: 45 – 52 D
• Advanced: 52 – 62 D
• Severe: > 62 D
Booysen, 2003
KC: Classification by Corneal Curvature

23. • Normal: 543 m
• Early: 506 m
• Moderate: 473 m
• Advanced: 446 m
Classification by Corneal Thickness
Booysen, 2003

24.  Nipple
 Oval
 Globus
Morphological Classification
Nipple
Oval
Globus

25.  KC: Classification by Corneal Shape
After: Bogan et al., 1990, Rabinowitz et al., 1996, Rasheed et al., 1998, Levy et al., 2004

26. Amsler Krumeich classification

27. Symptoms
Asymptomatic
Visual degradation reported
Progresses slowly over first 5 – 10 years of life
Ghosting/monocular diplopia due to irregular
astigmatism
Flare at night
Photophobia
Itching

28. External Sign
 Rizzuti Phenomena
 Munson’s Sign

29. Normal
Mild
Moderate
Advanced
Temporal
Nasal

30. Signs
↓ unaided vision
Scissoring Reflex
Progression of myopia & Irregular astigmatism
Distorted keratometry mires
↑ visibility of corneal nerve fibres
Vogt’s striae
Rupture of Descemet’s membrane (corneal hydrops)
Fleischer’s iron ring
Corneal topography/Tomography

31. Early sign :
Distorted retinoscopy reflex
Irregular astigmatism
↓ unaided vision
Marked changes in Rx sphere, cylinder, & axis
Distorted keratometry mires
Distorted photokeratoscope Placido rings
Steepening in Topography/tomography
Apical corneal thinning (stromal)

32. Later sign :
Advanced cone formation seen in profile
Apical scar formation
Munson’s sign on lower lid
Fleischer’s iron ring
↑ visibility of corneal nerve fibres
Vogt’s striae
Non-uniform red reflex with ophthalmoscopy
Rupture of Descemet’s membrane (corneal hydrops)
↓ IOP

33. Additional Sign in Advanced KCN
Thinning
Stromal edema
Splits/tears in the endothelium/
Descemet’s membrane
Endothelial cells may be elongated
Corneal scarring

34. KISA%: Rabinowitz Criteria
Corneal power (K) [>47.2 D]
Inferior-Superior dioptric asymmetry (I-S) [>1.2 D]
Sim K Astigmatism (Ast) >1.5 D
Skewed Radial Axis (SRAX) [>21°]
If KISA% > 60%, case is a KC suspect
KISA = (Central K) × (I−S) × (AST) × (SRAX) × 100/300

35. Management

36. Non surgical Management
Verbal guidance to the patient regarding the importance
of not rubbing eyes and use of topical lubricants (in case
of ocular irritation) to decrease the impulse to rub eyes.
Use of topical antiallergic medication(ie, antihistamines,
mast cell stabilizer, antiinflammatory) in patients with
allergy.
“Use of eye drops without preservatives is preferable in
keratoconus patients.”

37. Does spectacle works in Keratoconus?
Mild keratoconus in early stage can be corrected with
spectacles.
As the cornea steepens and becomes more irregular,
glasses not capable of providing adequate visual
improvement.

38. Soft contact lens
Suited to early stage progression only as it does have any tear lens
formation doesn't correct the irregularities.
In cases of GP CL intolerance
Usually, astigmatic component corrected with over-spectacles
Contact Lens

39. RGP contact lens
 Eliminate corneal irregularities with pre-corneal tear lens
formed by these lenses thus provides better visual
correction

40. RGP fitting philosophies
Apical clearance
Apical bearing
3 point or divided
support

41. APICAL CLEARANCE
 The central pooling or no apical
touch and the bearing is towards the
periphery
 Reduces the risk of scarring
 Tightening at the periphery may
result in sealing the tear exchange

42. APICAL BEARING
The central bearing or apical touch and the
pooling is towards the periphery resulting in
good visual acuity
Results in the corneal scarring and
intolerance

43. 3 POINT or DIVIDED SUPPORT
 Divided support or three point touch • An apical contact area of two
to three millimetres, a intermediate clearance zone and mid
peripheral contact annulus with conventional edge clearance at the
periphery.
 CL weight distributed over larger area.
Woodward EG. Contact lenses in abnormal ocular conditions—keratoconus. In: Phillips AJ, Speedwell L, eds.

44. So, what if patient cannot tolerate
RGP lenses??
 Piggy back system
 Hybrid lens system

45. Piggyback CLs
 Rigid lens fitted over a hydrogel lens increases comfort resulting
in adequate wearing time with good vision
SCL acts as a ‘carrier’ for the overlying GP CL
Used to ↑ comfort & ↓ risk of epithelial abrasion by a GP CL
Ultra-thin SCL (usually disposable)

46. Potential problems Piggyback CLs????
Handling and care of two different types of lenses.
Difficulty in obtaining centration of the rigid lens.

47. Better options than Piggy back !
One way to overcome the problems with piggy-
back lenses, yet have the optics of a rigid lens with
the comfort of a hydrogel, is to fuse a soft rim onto
a hard central portion
Hybrid Lens system

48. Combine the benefits of rigid lens optics, including
better lens centration and decreased aberrations, along
with the comfort of a soft lens Potential
Complications…
Flexure of the GP centre lens (leading to astigmatism
and decreasing visual results),
 Difficulties with insertion and removal of the lenses,
and
Tearing at the GP lens and hydrogel skirt junction.

49. Fully keratoconic designed lenses??
Scleral lens
Rose k family of lens

50. Scleral Lens
 Cornea is completely vaulted
Creating an equal and opposite keratoconic surface
ultimately restoring uniform optical lens and elimination
of astigmatism.
This result in less ghosting and much crisper vision
 Mini-Scleral – 12.5mm to 14.5mm
 Medium Range Scleral– 15.0mm to
18.0mm
 Full Scleral – 18.5mm to 28.0mm

51. Advantages
Better comfort,
Less mechanical trauma to the cornea
 better vision.

52. Rose K lens
Unlike traditional contact lenses, the complex geometry built into
every ROSE K contact lens closely mimics the cone-like shape of
the cornea for every stage of the condition.
The result is a more comfortable fitting lens for patients and
better sight (visual acuity).
Standard lens designs with fixed optical zones (OZ) do not ideally
fit the cone shape of keratoconus patients

53. Keratoconus show high flattening between the very
steep apex of the cone and the flat periphery.
Need to have very steep lenses in the center that get
flatter quickly at periphery.

54.  Fig shows a standard lens that will yield unwanted
pooling at the base of the cone and peripheral
bearing that can seal off and cause corneal
problems

55.  Fig demonstrates the benefits of a smaller optical zone to
fit the cone contour. The design results in little tear
pooling at the base of the cone and shows an even
distribution of tears under the lens.

57. Key points:
Use UV protection in the contact lenses and glasses
Improve patient comfort in order to minimize eye
rubbing
Non-steroidal anti-inflammatory medications (NSAIDs)
Preservative-free artificial tears
Allergy medications
Use properly fit contact lenses
Contact and scleral lenses are extremely important for
visual rehab. in patients with keratoconus.

58. Surgical Management
Corneal cross-linking
Deep anterior lamellar keratoplasty(DALK)
Penetrating keratoplasy(PK)

59. Corneal collagen cross-linking (CXL)
First described in 1998 by Spoerl et al. as a
modality for increasing the corneal biomechanical
strength to halt disease progression
First data presented in 2003 by Wollensak et al.
 In April 2016, the U.S. FDA gave approval to
corneal collagen cross-linking to treat progressive
keratoconus and post-LASIK ectasia.
Spoerl E, Huhle M, Seiler T. Induction of cross-links in corneal tissue. Exp Eye Res. 1998;66:97–103
G.Wollensak, E. Spoerl, and T. Seiler, “Riboflavin/ultraviolet-ainduced ollagen crosslinking for the treatment of
keratoconus,” The American Journal of Ophthalmology, vol. 135, no. 5, pp. 620– 627,

60. Corneal collagen cross-linking (CXL)
In CXL, riboflavin (vitamin B2) is administered in
conjunction with ultraviolet A (UVA, 365 nm).
–The interaction of riboflavin and UVA leads to the
formation of reactive oxygen species, which leads to
the formation of additional covalent bonds between
collagen molecules, with consequent biomechanical
stiffening of the cornea

61. Surgical Management
Young (eg, 15-year-old) patient with progressive KCN with
satisfactory vision with glasses
Perform CXL and prescribe glasses or contact lenses
Older (eg, 55-year-old) patient with stable KCN with satisfactory
vision with glasses
Prescribe glasses only or with contact lenses

62. Patient with stable severe KCN with unsatisfactory vision with
glasses and contact and scleral lenses? This patient has moderate
anterior corneal scarring but no evidence of previous corneal
hydrops
Perform DALK
Patient with stable severe KCN with unsatisfactory vision with
glasses and contact and scleral lenses? This patient has moderate
anterior and deep corneal scarring with evidence of previous
corneal hydrops
PK alone

63. As for PK, the most important factor in considering
keratoplasty in keratoconus is when
Significant corneal scarring (eg, posthydrops) is present.
Contact lens intolerant or is not keen on wearing contact
lenses; other surgical strategies fail, or are
contraindicated; the cornea is very thin (200 um); and
K eratoconus is deemed to be severe and at a potential
risk of acute hydrops.

64. TAKE HOME MESSAGE
A proper assessment of corneal topography is required
Careful Skilled fluorescein-pattern interpretation is the
cornerstone of successful CL fitting

65. Thank you
Avoid eye rubbing to avoid KCN progression……..