Keratoconus by Dr Tushya Om Parkash

1. KERATOCONUS
DR TUSHYA OM PARKASH
DR OM PARKASH EYE
INSTITUTE

2. KERATOCONUS
• Keratoconus is a degenerative non inflammatory
disease of the cornea were the central or
paracentral cornea undergoes progressive
thinning and steepening causing myopia and
both regular and irregular astigmatism

3. ETIOLOGY
• Etiology is unknown
• The hereditary pattern is neither prominent nor
predictable,but positive family histories have been reported
• The most common presentation of keratoconus is as a
sporadic disorder, in which only a significant minority of
patients exhibit a family history with autosomal dominant or
recessive transmission
• The incidence of keratoconus is often reported to be 1 in
2000 people

4. • Risk factors involved are eye rubbing,associated with atopy,
sleep apnea, Floppy lid syndrome, contact lens wear
• Systemic and ocular associations
1. Systemic disorders:
Down’s syndrome, Turner syndrome, Ehlers-Dunlos syndrome,
Marfan syndrome,atopy, osteogenesis imperfecta, and mitral valve
prolapse.
2. Ocular associations:
Vernal disease, retinitis pigmentosa, blue sclera, aniridia, and
ectopia lentis
• Onset is at puberty and progresses slowly thereafter, it may
become stationary

5. PATHOPHYSIOLOGY
Increased levels of proteases&catabolic enzymes
Decreased levels of proteinase inhibitor
Increased expression of IL-1 receptor
Decreased collagen & keratin sulphate
Increased levels of non proteinaceous substance
Decreased stromal mass & apoptosis

6. PATHOLOGY
• Classical Triad
1. Stromal thinning
2. Iron deposition in epithelium
3. Breaks in Bowman's layer
(irregularity of basement
membrane - earliest
change)and fibrosis filling in the
breaks that extend beneath the
epithelium
• With hydrops,breaks at the layer
of Descemets membrane are
seen.

7. Classification
• Based on severity of curvature
mild-less than 48D
moderate-48-54D
severe->54D
• Based on shape
Nipple cone-<5 mmround shape; easiest to fit with contact lenses
oval cone-5-6mm and steep curvature often displaced inferiorly; more difficult to
fit with lenses
globus cones-very large>6mm,75% of cornea affected; most difficult to fit with
lenses

8. Clinical features
• Symptoms are highly variable and, in part, depend on the stage
of the progression of the disorder. Early in the disease there may
be no symptoms, and kera- toconus may be noted by the
ophthalmologist simply because the patient cannot be refracted
to a clear 20/20 corrected vision. In advanced disease there is
significant distortion of vision accompanied by pro- found visual
loss. Patients with keratoconus fortunately never become totally
blind from their disease.
• Frequently changing spectacle Rx and axis of astigmatism
• Diplopia
• Glare at night
• Haloes around lights
• Blurred/ distorted vision

9. The classical signs of
keratoconus
External signs
• Munsons sign is a V-shaped
conformation of the lower lid
produced by the ectatic cornea
in downgaze.

10. External signs
• Rizzuti sign-It is a sharply
focused beam of light near
the nasal limbus, produced
by lateral illumination of
the cornea in patients with
advanced keratoconus.

11. Slit lamp
findings
• Stromal thinning
• Vogts striae-(Deep stromal stress
lines)
-Small and brushlike lines, generally
vertical but they can be oblique.
-Found in the deep layers of the
stroma and form along the meridian
of greatest curvature.
-Disappear when gentle pressure is
exerted on the globe through the lid.

12. Slit lamp
findings
• Iron ring-(fleischer ring)The Fleischer ring
is a yellow-brown to olive-green ring of
pigment which may or may not completely
surround the base of the cone
-Formed when hemosiderin (iron) pigment
is deposited deep in the epithelium
-Fleischer’s ring often becomes thinner
and more discrete with progression -
Seen approximately 50% of all cases.
-Locating this ring initially may be made
easier by using a cobalt filter and carefully
focusing on the superior half of the
cornea's epithelium.
Once located, the ring should be viewed in
white light to assess its extent.

13. Slit lamp
findings
• Scarring- epithelial and sub
epithelial (epithelial nebulae,
anterior stromal scars, enlarged
corneal nerves).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

14. Retroillumination signs
• Scissoring reflex on
retinoscopy
• oil droplet
reflex/Charleaux sign
on distant direct
ophthalmoscopy

15. • Other signs have been described such as pulsation of the mires on AT
• Videokeratography signs-
-Localized increased surface power
-Inferior superior dioptric asymmetry
-Relative skewing of the steepest radial axes above and below the
horizontal meridian
• Photokeratoscopy signs-
-Compression of mires inferotemporally (“egg-shaped” mires)
-Compression of mires inferiorly or centrally below the horizontal meridian

16. Acute hydrops
In some patients who have keratoconus, acute rupture of Descemet’s
mem- brane may occur and result in acute overhydration of the cornea and
ac- cumulation of lakes of fluid within the corneal stroma. The overlying
corneal epithelium may become edematous, and fluid may leak through
the corneal epithelium. The ruptured Descemet’s membrane curls in on
itself, and over time endothelial cells spread over the posterior stromal
defect to lay down new Descemet’s membrane and recompensate the
cornea.

17. Management
• Investigations-
-Pachymetry
-Keratometry
-Keratoscopy
-Videokeratography

18. Corneal Pachymetry
Slit lamp pachymetry shows thinning in the centre of the apex.
Ultrasonic pachymetry shows exact thickness of cornea at different
places.
Thinning in the inferior quadrant can be diagnostic of keratoconus.
Central or paracentral corneal thickness of less than 450 µm is
abnormal.
If the reading decreases by nearly 20 µm towards the inferior
periphery on successive pachymetric readings, it is suspicious of
keratoconus. Increase in the progressive thinning of the cornea is a
true index of keratoconus

19. Keratometer
Keratometer is an invaluable tool for measuring
corneal curvature. Inability to superimpose central
keratometric rings suggests irregular corneal
astigmatism, a hallmark of keratoconus. There is no
keratometric value beyond which diagnosis of
keratoconus is definite. There are patients with steep
corneas and high astigmatic errors who do not have
keratoconus and, conversely, patients with
keratoconus who have central corneas of normal
steepness

20. Keratometer
Inferior corneal steepening is also an early sign of
keratoconus. By performing central keratometry,
followed by keratometry with the patient in upward
gaze, steepening in the inferior cornea can be
identified .
Keratoscopy or videokeratography, based on Placido disk,
can show In early keratoconus, a focal area of
increased corneal curvature as an isolated area of
smaller ring spacing and distortion. ring spacing
decreases overall and becomes increasingly
irregular on progression

21. Keratoscopy
Keratoscopy uses a pattern of concentric rings (mires)
called a Placido disk with nine alternating bright and
dark rings.
The rings are reflected off the anterior cornea surface
via Purkinje image number one and viewed directly
by the clinician.
The Placido disk is nothing more than a simple,
inexpensive hand-held device with a central peep-
hole for the clinician through which to look

22. Photokeratoscopy signs
Compression of mires inferotemporally
(“egg-shaped” mires)
Compression of mires inferiorly or centrally
The photokeratoscope or topographer placido disc can provide an
overview of the cornea and can show the relative steepness of any
corneal area.

23. Computerised
videokeratography
• Commonly used ORBSAN
• Elevation based maps with Placido disc capabilities
• Gives:
• -true elevation maps
• -posterior corneal surface
• -anterior corneal surface
• -pachymetry
• -AC depth
• -features ray tracing,IOL calculation and 3D mapping
software.

24. Forty images, 20 with slit beams
projected from the left and 20 from
the right, are acquired in two
intervals, each 0.7 seconds in
duration.
Simultaneously, a tracking system
measures the involuntary
movement of the eye during the
exam.

25. COLOR CODED MAP
GREEN- Normal
YELLOW & RED- HOT (Steeper
areas).
BLUE- COOL (Flatter areas

26. Keratoconus pattern
Keratoconus cornea-
extreme asymmetrical
and inferior steepening
Non keratoconus
cornea-general
symmetry overall with
no excessive steepening

27. Keratoconus
Features on topography [Rabinowitz et al]
-Central corneal power > 47D
-Diff. of 3D or more in corneal power of a point 3mm
superior to corneal vertex to that located 3mm
inferior to it (sup./inf. Ratio).
-Asymmetry in central corneal power between two
eyes > 1.4D.
-These findings have a sensitivity of 98% and a
specificity of 99.5% for the diagnosis of keratoconus.

28. Normal Cornea

29. keratoconus suspect

30. Keratoconus

31. Treatment
• Conservative
-Spectacles
-Contact lens
-Corneal Collagen cross linking
• Surgical
-Intacs
-Corneal transplant
-Phakic IOLs
-Recent advances

32. Spectacles
• Mild keratoconus can be corrected with spectacles.
• Retinoscopy is difficult; a normal subjective refraction is
required.
• Monocular keratoconus is usually best dealt with using
spectacle correction.
• In this group of patients, motivation for contact lens wear
tends to be poor.

33. Contact lenses
Contact lenses are considered when vision is not correctible to
6/9 by spectacles and patients become symptomatic.
Rigid gas permeable (RGP) contact lenses are the lenses of first
choice.
The aim is to provide the best vision possible with the maximum
comfort so that the lenses can be worn for a long period of
time.

34. Contact lenses
• RGP contact lens
-It resurfaces the irregular cornea & the intervening fluid and corrects
the irregular astigmatism to provide good quality of vision
-However the disadvantage with these lenses is that they have standard
lens design with fixed optical zones and do not give an ideal fit in
patients with keratoconus
-Many patients find them uncomfortable and can tolerate only for short
time,the reason is that cornea steepens and rubs against the lens
causing n abrasion and light sensitivity
-Dry eye is another problem with them

35. Contact lenses
Based on shape of cone
Nipple cone : small diameter (5 mm.); round shape; easiest to fit
with contact lenses
Oval large diameter(>5 mm.); often displaced inferiorly; more
difficult to fit with lenses
Globus largest diameter (>6 mm.); 75% of cornea affected; most
difficult to fit with lens

36. Contact lenses
• Fitting methods
-Three point touch technique
-Apical clearance
-Flat fitting
• Three-point-touch design-It actually refers to the area of apical central contact
and two other areas of bearing or contact at the mid-periphery in the horizontal
direction.
The three-point-touch design is the most popular and the most widely fitted design
The aim is to distribute the weight of the contact lens as evenly as possible between
the cone and the peripheral cornea.
The ideal fit should show an apical contact area of 2-3mm with mid-peripheral contact.
Adequate edge clearance is required to ensure tear exchange.

38. Contact lenses
Apical clearance
In this type of fitting technique, the lens vaults the cone and clears
the central cornea, resting on the paracentral cornea.
These lenses tend to be small in diameter and have small optic
zones
The potential advantages of reducing central corneal scarring are
outweighed by the disadvantages like poor tear film, corneal
oedema, and poor visual acuity as a result of bubbles becoming
trapped under the lens.

40. Contact lenses
Flat fitting
The flat fitting method places almost the entire weight of the lens
on the cone.
The lens tends to be held in position by the top lid.
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.
This type of fitting is useful where the apex of the cone is displaced

42. Contact lenses
Piggy back lenses - RGP-CL fitted on top of a SOFT CL
Can be used in pts who are uncomfortable with RGP wear, more
so in pts prone to epithelial erosion at apex of cone
ROSE-K lenses -are specially designed for keratoconic eyes to fit
any type of cone.The optical zone is reduced to snugly fit the
cone & the peripheral curve is computer designed to fit the rest
of the irregular cornea

43. Contact lenses
Scleral lenses
They are made of special polymer called itaflurocon.
Scleral lenses play a very significant role in cases of advanced
keratoconus where corneal lenses do not work and corneal
surgery is contra-indicated.
Scleral lenses completely neutralise any corneal irregularity and
can help patients maintain a normal quality of life
Disadvantage is that they are difficult to use as they are large
senses and cumbersome to the patients

45. Contact lenses
• Soper lenses
Custom made lens
Two zones in the peripheral posterior curvature
Central zone : to vault steep central cornea .It is of varying
steepness depending of the patients cornea.
Peripheral zone is with a 45D curvature designed to vault the mid
periphery and limbal cornea

46. Contact lenses
• Boston scleral lens prosthetic device (BSLPD)
The lenses are made of flurosilicone acrylate polymers with Dk
values of 87 and 130.
-Fluid ventilated scleral lens
-Designed to enclose a bubble free reservoir of fluid over the
corneal surface
-Series of breaches are created between haptic bearing surface of
the lens and underlying sclera
-This will facilitate the aspiration of surface tears into the reservoir
so that intrusion of air bubble during a blink is prevented.
-Shape of haptic confirms exactly to that of underlying sclera to
maintain functionality and prevents intrusion of air bubbles.
-Very expensive

47. Medical therapy
• For acute corneal hydrops involves
-A cycloplegic agent
-Sodium chloride 5% ointment or eye drop
-Lubricating eye drop
-Steroid drops can be used if the eye is congested
-A pressure patch
-After the pressure patch is removed patients may still need to continue
sodium chloride drops or ointment for several weeks to months.
-Patients are advised to avoid vigorous eye rubbing

48. Collagen cross linking
• A newer and less invasive technique that shows promise in
keratoconus management is combined riboflavin-ultraviolet type
A rays( UVA ) collagen cross-linking.
• This procedure consists of photopolymerization of corneal
stroma by combining vitamin B2 (photosensitizing substance)
with UVA.
• This process increases rigidity of corneal collagen and thus
reduces the likelihood of further ectasia.

49. Corneal collagen
crosslinking
• Technique
-Using topical anaesthesia, 7mm circle is marked on the cornea using a marker.
-Epithelium of the marked area is scraped off using a blunt spatula.
-A corneal abrasion is created to facilitate riboflavin diffusion into the cornea.
-One drop of riboflavin 0.1% and 20% dextran ophthalmic solution is instilled
topically in the eye every 2 minutes for 30 minutes.
-At the end of the 30-minute pretreatment period, the eye is examined with blue
light for the presence of a yellow flare in the anterior chamber, indicating
adequate riboflavin saturation of the corneal tissue.

50. Corneal collagen cross
linking
-When the yellow flare in the anterior chamber is confirmed, the eye
is aligned under the UV-A light
-The correct aperture setting is selected for the size of the eye; the
eye is irradiated at 3Mw/cm2 for 30 minutes at wavelength of
370nm, during which time instillation of riboflavin is continued (one
drop every 5 minutes).

51. -After completion of the procedure,eye is washed with BSS , an
antibiotic drop is instilled and a bandage contact lens is applied.
-The contact lens is removed once the abrasion has healed.
-Postoperative medications include an antibiotic and a
steroid(controversial) for 2 weeks postoperatively.
-Complications of C3R
Corneal haze
Diffuse lamellar keratitis
Reactivation of viral keratitis and iritis
Infective keratitis
Corneal scarring
Persistent corneal edema
Corneal melt

52. -mild to moderate keratoconus
-post refractive ectasia
-PMD
Contraindications
-A minimum stromal thickness of 400 μm after epithelial removal is
required for safe CXL.
-In patients with corneas thinner than this, conventional CXL cannot
be performed. For such patients, either contact lens–assisted CXL
(CACXL) or hypotonic CXL is performed.
-CXL is also not performed in patients with stable, nonprogressive
keratoconus. Keratoconus is generally likely to be nonprogressive in
patients older than 35 years because of naturally occurring cross-
linking occurring with age.
Indications

53. Contact lens-Assisted
collagen cross-linking
It is possible that some corneas do not swell enough
to make hypo-osmolar CXL possible.
CACXL has advantage of not being dependent on
swelling properties of the cornea . In CACXL,
thickness of cornea is artificially increased by
increasing amount of riboflavin-containing substance
anterior to the stroma, increasing functional corneal
thickness. using precorneal riboflavin film, a riboflavin-
soaked soft contact lens , and a pre–contact lens riboflavin
film

54. Contact lens assisted C3R

55. Contact lens associated
C3R

56. Accelerated C3R
As an alternative to riboflavin formulations containing dextran,
the KXL uses riboflavin 0.1% in hydroxypropyl methylcellulose
(Vibex Rapid™, Avedro, Inc.). initial procedure is similar to
conventional CXL of epithelial debridement. Vibex is then
administered topically for 10 minutes. The cornea is then
exposed to 365 nm UVA light with the CXL system for three
minutes at an irradiance level of 30 mW/cm2 (accelerated
CXL).

57. Intracorneal ring segments
in keratoconus
• A method for flattening the cornea that is too steep and
making a patient more contact lens tolerant is the
insertion of INTACS into the cornea
• This procedure is good for patients who are contact
lens intolerant and who want to avoid a corneal
transplant and whose k reading are not in excess of 58
diopters
• INTACS have been approved for the treatment of mild
to moderate keratinous in patients who are contact
lens intolerant

58. Intracorneal ring segments
• In these cases, patients must have a clear central cornea
and a corneal thickness of >450 microns where the
segments are inserted,approximately at 7mm optical zone
• INTACS have crescent shaped two 150-degree PMMA
segments that are surgically placed in the peripheral
cornea at two-thirds corneal depth
• INTACS comes in thickness from 0.25 to 0.45 mm in
0.05mm increments
• INTACS correct the myopia and irregular astigmatism by
producing a mechanical flattening of the central cone

59. Intracorneal ring segments
• The advantage INTACS is that they require no
removal of corneal tissue.no intraocular
incision,and leave the central cornea untouched
• Most patients will need spectacles/contact lens
postoperatively for best vision,but will have flatter
corneas and easier use of lenses
• If a patient does not gain the expected results, the
INTACS can be removed and then other surgical
options can be considered

60. Intracorneal ring segments

61. Intracorneal ring segments
• Types
1.Ferrara ring
2.Keraring
3.INTACS

62. Intracorneal ring segments
Implantation of intracorneal ring segments with support from
• Femtosecond laser technology allows realization with very high
• During surgery stress on the cornea is minimal, because only m
• The risk of infection is significantly reduced

63. Intracorneal ring segments
Complications
Undercorrection
Overcorrection
Migration of rings
Extrusion or progressive thinning
New vessel formation
glare /halos

64. Lamellar keratoplasty
-LKP has been shown to result in less endothelial cell
loss, less IOP problems than PKP , a reduction in
rejection episodes, &, in some cases, a reduction of
induced astigmatism.
-This technique requires less recovery time, and poses
less chance for corneal graft rejection or failure.
-However, while some series have achieved
comparable visual outcomes, others have
demonstrated that penetrating techniques
slightly outperform deep lamellar procedure.

65. LK
• Indications of DALK regarding KC:
Anterior corneal scars
Advanced disease with stress lines and clear cornea
K-max > 65 dpt
Thinnest location < 350 m
Very high refractive error (sphere > −6 and/or cylinder
> −6)

66. Penetrating keratoplasty
Between 10% & 25% of cases of KC progress to point
where visual rehabilitation is no longer possible,
especially in those who present at a young age
(younger than 20) and with keratometry
measurements > 60 dpt & corneal thickness < 400 m
at the thinnest location. In the past, such patients
have had only one option: a full thickness corneal
transplant . KC is one of the most common
indications for penetrating keratoplasty accounting for
15–25% of such surgeries

67. Penetrating keratoplasty
As the cornea is avascular, the donor and host do not
have to be tissue matched and eye banks – after
checking for communicable diseases and tissue
quality – can provide
suitable tissue within a few days or weeks.
Following surgery, visual recovery takes several
weeks/ months, with full stabilization often taking up to
a year after which time the sutures can be removed.

68. PKP
Corneal transplantation in KC is considered relatively
low risk, in terms of graft rejection and other
postoperative complications, as these eyes do not
typically exhibit corneal neovascularization.
Despite these facts, there are reported
complications such as allograft rejection, iatrogenic
astigmatism, significant endothelial cell loss .

69. PKP
When the life expectancy is long, side effects caused
by long-term use of topical steroids (e.g., secondary
glaucoma and cataract), and recurrence of KC on the
graft itself. Clear grafts are obtained in 95% of cases
but optical outcomes may be unsatisfactory
because of the iatrogenic astigmatism and
anisometropia. Between 30% and 50% of grafted
eyes still require contact lens correction for best acuity
or further keratorefractive surgical procedures

70. Phakic IOLS
Used to correct high myopia and associated
astigmatism of selected keratoconus patients.
Anterior chamber phakic intraocular lens have also
been combined with intacs with good results.
The Intacs implantation is followed by toric phakic
intraocular lens implantation to correct the residual
myopic and astigmatic refractive error

71. Recent Advances
• Keraflex KXL
-It is the newest procedure under investigation for the treatment of
keratinous
-It is non incisional and reshapes the cornea without removing any tissue
-It is currently under clinical investigation in Europe for treating myopia
and keratoconus
-It involves the delivery of a single low energy microwave pulse lasting
less than one second to the cornea
-Energy is applied to the cornea using a dielectrically shielded microwave
emitter which contacts the epithelial surface
-Through capacitive coupling, the single pulse raises the temperature of
the selected region of corneal stroma to approximately 65 degree celsius,
forming a doughnut shaped area of collagen shrinkage in the upper 150
microns of the stroma

72. • The lesion created during keraflex is intended to
flatten the central cornea both to decrease the cone
in keratoconus and to achieve myopic correction
• In order to improve the stability of the cornea with
keraflex, Keraflex KXL includes focal corneal
collagen cross linking
• After the actual Keraflex procedure, riboflavin drops
are administered over the treatment area, a mask is
applied to protect the central and peripheral areas of
the cornea, and uv light is administered to crosslink
the collagen.

73. Final Summary
-Anyone with progressive ectasia should
undergo CXL no matter what age or level of
vision (assuming the eye was an
appropriate candidate).
not to proceed with surgery (other than CXL)
-If patients were satisfied with their vision
with glasses or contact lenses. ICRS may be
considered. phakic IOLs should be used
less often

74. Final summary
-A strong preference for DALK when a
corneal transplant was needed, unless eye
had previous compromise of Descemet
membrane (most commonly from acute
hydrops), at which point the preference is
for a PK.
- pdDALK may be considered even in the
presence of previous hydrops.