This document provides an overview of keratoconus, including its etiology, signs and symptoms, classification, and management. Keratoconus is a non-inflammatory thinning of the cornea that results in a cone-shaped protrusion and irregular astigmatism. It typically onset in teenagers and progresses over time. Management includes rigid gas permeable contact lenses, collagen cross-linking to halt progression, and keratoplasty for advanced cases.

1. KERATOCONUS
Manoj Aryal
IOM. MMC

2. PRESENTATION LAYOUT
• Introduction
• Aetiology
• Onset
• Clinical signs and symptoms
• Histopathology
• Classification
• Management

3. INTRODUCTION
• Greek word
• Kerato : cornea Konos : cone
• First described by British ophthalmologist John
Nottingham in 1854
• Most common corneal ectasia
• Incidence 1 in 2000

4. 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.

5. AETIOLOGY
• Collagen abnormality
• Familial tendency
• Eye rubbing due to allergy
Aggravating factors
• UV exposure
• Poorly fitting contact lenses.
• Inflammation.

6. ASSOCIATED CONDITIONS:
OCULAR
• Retinitis pigmetosa
• Retinopathy of
prematurity
• Ankyloblepharon
• Floppy eyelid syndrome
• Gyrate atrophy
• Leber’s congenital
amaurosis
• Vernal conjunctivitis
• Atopic dermatitis
• Micro cornea
• Blue Sclera
• Aniridia
• Congenital cataract
• Persistent pupillary
membrane
• Posterior lenticonus

7. ASSOCIATED CONDITIONS:
MULTI-SYSTEM
• Down’s Syndrome
• Marfan Syndrome
• Cruzan's Syndrome
• Ehlers-Danlos Syndrome
• Xeroderma pigmentosa
• Neurofibromatosis
• Osteogenesis
imperfect
• Turner’s Syndrome

8. ONSET
• Mean age of onset is age 16 years
• Shows no gender predilection and is
bilateral in over 90% of cases.
• Develops asymmetrically

9.  Frequently changing
spectacle Rx and
axis of astigmatism
 Ghosting/ monocular
diplopia
 Glare at night
 Haloes around lights
Blurred/ distorted
vision
 Scissors reflex
(swirling
retinoscopy reflex)
 Distorted/ irregular
Keratometer mires
with steep readings
 Prominent corneal
nerves
Signs Symptoms

10. Corneal nerves
• more prominent than in normal eye
Vogt’s striae
Fine vertical lines in the stroma and Descemet’s
membrane,
Form along the meridian of greatest curvature.
• Disappear temporarily on digital pressure.
Fleischer’s ring
Iron pigment ring forms the base of the
cone. May be partial or complete.

11. • Corneal thinning
•Visible in the central-inferior region in
moderate and advanced Keratoconus.
•Represents an actual reduction in the
number of stromal lamellae
• Munson’s sign
•Ectasic protrusion of the cornea on down
gaze produces a V-shaped conformation of
the lower lid.
• Rizzuit sign
•Lateral illumination of the cornea produces
a steeply focused beam of light near the
limbus. Moderate: beam central to limbus.
Advanced: beam displaced peripherally

12. •Corneal scarring
• Sub-epithelial corneal scarring,
not generally seen early, may
occur as keratoconus progresses
because of ruptures in Bowman's
membrane which is then filled
with connective tissue
•Corneal hydrops
• Occurs, generally in
advanced cases, when
Descemet's membrane
ruptures, aqueous flows into
the cornea and reseals

13. ACUTE KERATOCONUS/CORNEAL
HYDROPS
• Sudden loss of vision usually
associated with pain
• Acute, marked corneal edema,
often with fluid clefts in the
stroma

14. ACUTE KERATOCONUS/CORNEAL
HYDROPS
Resolves over a period of weeks to
months
Results in corneal scarring and
flattening, with or without corneal
neovascularization.
Rarely, complicated by corneal
perforation.

15. ACUTE KERATOCONUS/CORNEAL
HYDROPS
• Managed with
• Patching or bandage contact lens
• Cycloplegia
• Hypertonic sodium chloride ointment and
/or drops

16. HISTOPATHOLOGY:
• Fragmentation of Bowman layer
• Thinning of the stroma and overlying epithelium
• Folds or breaks in Descemet's membrane
• Fleischer ring: Ferritin particles accumulate within
and between the epithelial cells, particularly in the
basal epithelium

17. CLASSIFICATION
Based on severity of curvature
 Mild <45 D in both meridians
 Moderate 45-52 D in both meridians
 Advanced >52 D in both meridians
 Severe >62 D in both meridians

18. CLASSIFICATION
Based on type of cones
• Round or nipple
• Cone-lies in centre
towards inferior nasal
quadrant
• Most common,
• less than 5 mm in
diameter
• Easiest to fit with
contact lenses

19. • Oval cone
• diameter(>5 mm.);
often displaced
inferiorly
• more difficult to fit
with lenses

20. • Globus cone
• overall steepening
• diameter more than 6
mm diameter.
• 75% of cornea affected;
most difficult to fit
with lenses

21. Keratometer (Ophthalmometer )
Keratoscope :
• Placido disc
• Photokeratoscopy
• Video Keratoscopy (Computer assisted
topographic analysis.)
METHODS OF
MEASUREMENT(DIAGNOSIS)

22.  Principle
 Use of the first
Purkinje image.
• Consists of equally
spaced alternating
black & white lines.
PLACIDO DISC

23. • A luminous object
(target of rings) is
placed in front of
patient’s cornea.
• Image size produced in
the corneal reflection
is measured

24.  Circular Rings -Spherical cornea
 Oval Rings –Regular astigmatism .
 WTR astigmatism
 ATR astigmatism
CLINICAL INTERPRETATION
With long vertical axis –
Against the Rule Astigmatism.

25. • Photokeratoscope
• The even separation of the rings in the spherical
cornea.
• In astigmatic cornea uneven spacing of the rings--
especially inferiorly
• The central rings may show a tear-drop
configuration termed "keratokyphosis".

26. Cool colors (black, blue, azure)
Flatter surfaces
Warm colors (orange, red, white)
Steeper surfaces
Normal (green, yellow)
Normal surfaces
CORNEAL TOPOGRAPHY

27.  Bow- tie patterns indicate astigmatism
CLINICAL EXAMPLES

28. Small, near central ectasia, less
than 5.0 mm in cord diameter
NIPPLE-SHAPED TOPOGRAPHY
May manifest as moderate to
high with-the-rule corneal
astigmatism

29. In advanced keratoconus.
Corneal apex is displaced
well below the midline
resulting in varying degrees
of inferior mid-peripheral
steepening.
Kissing pigeon pattern
(diagnostic of PMD)
OVAL SHAPED TOPOGRAPHY

30. GLOBUS-SHAPED TOPOGRAPHY

31. Spectacles
• 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.
MANAGEMENT

32. FITTING PHILOSOPHIES
FOR KERATOCONUS
WITH CONTACT LENS

33. 1. FLAT FITTING
• The flat fitting method places almost
the entire weight of the lens on the
cone
• Good visual acuity is obtained as a
result of apical touch.
• Alignment can be obtained in early
keratoconus; however, flat fitting
lenses can lead to progression/
acceleration of apical changes and
corneal abrasions

34. 2. APICAL CLEARANCE
• The lens vaults the cone and clears
the central cornea, resting on the
paracentral cornea
• Apical clearance would minimize
trauma to the central cornea
• The potential advantages of reducing
central corneal scarring are
outweighed by the disadvantages of
poor tear film, corneal edema, and
poor visual acuity as a result of
bubbles becoming trapped under the
lens

35. 3. THREE-POINT TOUCH
• The aim is to distribute the
weight of the contact lens as
evenly as possible between the
cone and the peripheral cornea.
• lens lightly touches the peak of
the cone then a very low vault
over the edges of the cone, and
lastly a thin band of touching
near the edge of the lens

36. Contact lenses
• Soft contact lenses
• Rigid gas permeable lenses
• Combined lens system
• Piggy back system
• Hybrid lens system
• Fully keratonic designed lenses
• Rose k family of lens
• Scleral and mini scleral lens

37. SOFT CONTACT LENSES
• It is not better than spectacle lens but it works in piggy
back system
• At very early stage, this way work as equal to spectacle
does.
• But patient may not be satisfied with the level of vision he
has even though it is 6/6
• Shadow effect of texts
• Ghosting of image
• Poor night vision
• Eye fatigue on prolong reading

38. RIGID GAS PERMEABLE LENSES
• Cost effective, easily available,
suitable for mild to moderate
keratoconus
• Fitting: three point conventional
fitting philosophy

39. COMBINED LENS SYSTEM
Piggy back system
 Hybrid lens system

40. Piggy back system
• Rigid lens fitted over a hydrogel lens increases
comfort resulting in adequate wearing time
with good vision

41. Hybrid lens system
• 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

42. FULLY KERATONIC DESIGNED LENS
Rose k family of lens

43. SCLERAL AND MINI-SCLERAL LENS
Design to fit all irregular corneas which don’t
tolerate any other RGP or hybrid/Soft lens

44. COLLAGEN CROSS-LINKING (CXL
OR C3-R)
• It may slow or halt the progression of
keratoconus by using a photo-oxidative
treatment to increase the rigidity of the
corneal stroma.

45. KERATOPLASTY
• For patients Intolerant to contact lens and
cases with scarring
• Penetrating keratoplasty and Deep anterior
lamellar keratoplasty can be done
• Patient may have to continue contact lens ,but
will have better tolerance