Keratoconus

1. KERATOCONUS - RECENT ADVANCES
Dr .M.Dinesh

2. • Corneal ectasia is a group of disorders affecting the corneal shape,
includes
keratoconus,
pellucid marginal corneal degeneration, and
keratoglobus
posterior keratoconus

3. Keratoconus -history
• The first description of keratoconus can be traced back to the works of
Benedict Duddell
• In 1736 Duddell published a treatise, "The Diseases of the Horny-coat
of The Eye", which includes one of the earliest descriptions of what we
know today as keratoconus. In his work, he describes a 14-year-old boy
with "the corneas very prominent, like obtused cones, which were
sufficiently conspicuous

4. • In 1748, German anatomist and surgeon, Burchard Mauchart, provided
a more detailed description of a case similar to keratoconus, which he
called "staphyloma diaphanum".
• Conical cornea was first described in great details in 1854 by British
physician John Nottingham and distinguished it from other form of
ectasias
• Swiss ophthalmologist Johann Horner who gave Keratoconus its current
name in 1869 by titling his thesis "Zur Behandlung des Keratoconus" or
"On the treatment of keratoconus".

5. • Keratoconus is a
progressive,
noninflammatory,
noninfective
thinning disorder of cornea with ectasia of conical shape
causing irregular corneal astigmatism of unknown cause
• The word has its origin from Greek terminology:
kerato-horn, cornea;
konos- cone

6. • Cellular infiltration and vascularization do not occur.
• It is usually b/l
• Although it involves central two-thirds of cornea, apex of cone is
usually centered just below visual axis. This results in mild to marked
impairment of visual function
• prevalence of keratoconus is 54.5 per 1 lakh population
• Asians
have a fourfold higher incidence,
are younger at presentation and
require corneal grafting at an earlier age compared with white
patients.

7. • Why Asians have higher incidence ?
The Asian patients were mostly of Northern Pakistani origin. This
community has a tradition of consanguineous, especially first-cousin
marriages. The higher incidence in this population was highly suggestive
of a genetic factor being significant in the aetiology.
( ref :Eye (Lond) journal 2004 April.
https://www.ncbi.nlm.nih.gov/pubmed/15069434
http://www.nature.com/eye/journal/v18/n4/full/6700652a.html )

8. ETIOLOGY :
• Definite etiology is unknown.
• 95% of patients do not show evidence of specific hereditary pattern. Pattern
of inheritance is variable.
• It is thought to be assoc with genetic and environmental factors.
• Evidence of genetic etiology includes the familial inheritance, discordance
between dizygotic twins, and its association with other known genetic
disorders.
• Environmental factors include contact lens wear, chronic eye rubbing, and
atopy of the eye

9. • Several theories have been put forward to explain the etiology of
keratoconus.
• ENZYME THEORY
Alteration in the levels of following enzymes have been noted:
Increased level of epithelial lysosomal enzymes.
Decreased level of alpha-1 proteinase inhibitor in the epithelium.
glucose-6 phosphate dehydrogenase in the
epithelium.

10. Degradative Enzymes
Collagen/Matrix
Produced
Thin Cornea
Degradative Enzymes
Collagen/Matrix
Produced

11. UVB Mechanical
Lipid Peroxidation
INCREASED
Peroxynitrites
AntioxidantAntioxidant
EnzymesEnzymes
Oxidative
Damage
Nitric Oxide
ROS/RNS
INCREASED
Cytotoxic aldehydes
ACTIVATE
DEGRADATIVE
ENZYMES
Mitochondria
reactive oxygen species (i.e., free radicals).

12. Modified from Yakes & Van Houten (PNAS 1997)
A. Normal Cell
Oxidative
Stress
Antioxidant enzymes
Lipid peroxidation enzymes
Elimination of ROS
ROS Compounds
Minimal mtDNA
damage
Normal cell
function
Atopy
Eye rubbing
Stretching
UVB light

13. B. Keratoconus Cell
ROS Compounds
mtDNA damage
OXPHOS
ROS Production
Abnormal cell
function
Corneal thinning
Abnormal antioxidant enzymes
Lipid peroxidation enzymes
Accumulation of ROS
Atopy
Eye rubbing
Stretching
UVB light
Genetic defects
Oxidative
Stress
Enzymes Activity
Tissue Degradation

14.  CONNECTIVE TISSUE ABNORMALITY THEORY
association of keratoconus with some connective tissue disorders.
GENETIC THEORY
Due to the occasional association of trisomy-21 with keratoconus,
 HORMONAL THEORY
because of the manifestations of the disease in adolescence.
 EYE RUBBING
Habitual eye rubbing in some diseases like
vernal catarrh,
Down syndrome and
poorly sighted patients of Leber’s tapetoretinal degeneration are
associated with keratoconus.

15. It is commonly an isolated ocular condition but sometimes
coexists with other ocular and systemic diseases like
• Connective tissue and mesodermal dysplasia
• Marfan’s syndrome
• Ehlers-Danlos syndrome
• Osteogenesis imperfecta
• Congenital hip dysplasia
• Oculodento digital syndrome
• Rieger’s syndrome Atopic dermatitis Down syndrome Ehlers-Danlos syndrome
• Crouzon’s syndrome
• Floppy eyelid syndrome
• Down syndrome
• Turners syndrome
• Mitral valve prolapse Osteogenesis imperfecta

16.  ASSOCIATED OCULAR DISORDES
• Retinitis pigmentosa
• Lebers congenital amaurosis
• Blue sclerae
• Congenital cataract
• Aniridia
• Retinopathy of prematurity
• Fuchs dystrophy
• Posterior polymorphous
dystrophy
• Granular and lattice
dystrophy
 ALLERGIC CONDITIONS
• Spring catarrh
• Asthma

17. PATHOLOGY :
• Every layer and tissue of the cornea can potentially be involved in the
pathologic process of keratoconus.
• Central epithelial thinning has been found with variable frequency.
• Specular microscopy of the corneal epithelium has revealed
-enlargement of the superficial cells and
-prominence of elongated cells, (not seen in long-term hard contact
lens wearers)
• Early degeneration of the basal epithelial cells can be followed by
disruption of the epithelial basement membrane.

18. • Breaks in the epithelial layer can be associated with
epithelium growing posteriorly into Bowman's layer and
collagen growing anteriorly into the epithelium,
forming Z-shaped interruptions at the level of Bowman's layer.
These Z-shaped areas are typical of keratoconus
• Fragmentation of the Bowman's layer seen with scanning electron
microscopy has been described as specific to keratoconus and possibly
an early change leading to the disease.

19. • A hallmark of keratoconus is the Fleischer ring found at the base of the
cone .
• The brown iron ring can be seen histopathologically (B).
• Light and electron microscopy reveal that ferritin particles accumulate
within and between the epithelial cells, particularly in the basal
epithelium.
The ring results from hemosiderin pigment deposited
in the basal epithelium. (Prussian blue stain )

20. SYMPTOMS
• Typically, patient in teens or twenties
• progressive visual blurring and/or distortion.
• Photophobia and watering
in cases of hydrops
• glare,
• monocular diplopia
or ghost images
• Halos around lights and
• ocular irritation
• Having multiple unsatisfactory spectacles

21. SIGNS :
• Loss of contrast sensitivity even before visual acuity loss(Krachmer 3rded)
• The cornea thins near the centre and progressively bulges forwards, with
the apex of the cone always being slightly below the centre of the cornea
• The cornea is at first transparent and the vision is impaired
due to myopic astigmatism
• The patient becomes myopic, but the error of refraction cannot be
satisfactorily corrected with ordinary glasses owing to the parabolic nature
of the curvature which leads to irregular astigmatism in the later stages

22. External signs:
• Munson sign :a protrusion of the lower eyelid upon
downgaze
• Rizzutti sign : a conical reflection on the nasal cornea when a penlight is shone
from the temporal side, is another early finding

23. RETROILLUMINATION SIGNS:
• Scissoring reflex - found on
retinoscopy
Charleux’ oil droplet sign-a dark reflex
in the area of the cone on observation
of the cornea with dilated pupil
using distant direct ophthalmoscopy

24. SLIT LAMP SIGNS :
1. Thinning of the cornea to half of one-fifth the normal thickness at the
apex of the cone.
2. Increased endothelial shining reflex at the central portion of the cornea
at the peak of the cone due to increased concavity of the posterior
surface.

25. 3.Prominent corneal nerve fibers forming a network of gray line with
gray dots.

26. 4. Brown ring of iron pigment deep in the epithelium (Fleisher’s ring) at
the base of the cone, seen in red-free light in 50 percent of cases.

27. 5.Vogt’s striae : vertical stress lines in deep stroma and Descemet’s
membrane, at the apex of the cone,often earliest slit lamp finding

28. 6.Ruptures in the Bowman’s membrane produce reticular, subepithelial,
and anterior stromal scars
extensive stromal apical scarring and linear
breaks in Bowman’s layer

29. • 7.Rupture in Descemet’s
membrane causes
development of sudden onset
redness and pain(Acute
hydrops ) to imbibition of
aqueous into corneal stroma
causing it to swell

30. 8.Double cones, i.e. one small acute protrusion with a large peripheral
protrusion in the area of the cone.
9. Scarring in the center of the cone leads to opacity.
10. Inferior corneal steepening is an early sign of keratoconus
11. Endothelial cell pleomorphism and polymegathism occur in
keratoconus

31. KERATOSCOPE :
• Placido disc
• Photokeratoscopy
• Video Keratoscopy
(Computer assisted topographic
analysis.)
hand held Klein
keratoscope

32. Placido disc :
Principle
• Use of the first Purkinje image.
• Consists of equally spaced
alternating black & white lines.

33. • A luminous object (target of rings) is placed in front of patient’s cornea.
• Image size produced in the corneal reflection is measured
• With (handheld keratoscopes) Klein keratoscope,
early keratoconus is characterized
by a downward deviation of the
horizontal axis of the
Placido disk reflection

35. PHOTOKERATOSCOPY :
• The photokeratoscope or topographer placido disc can provide an
overview of the cornea and can show the relative steepness of any
corneal area.
• There is even separation of the rings in the spherical cornea .

36. • In astigmatic cornea uneven spacing of the rings,
especially inferiorly-in the keratoconic cornea should be noted
• The central rings may show a tear-drop configuration termed
"keratokyphosis".

37. KERATOMETRY:
• The keratometry mires commonly are
steep,
highly astigmatic,
irregular, and
often appear egg-shaped rather than circular or oval, in
keratoconus patients.
• It also shows increased keratometry values typically between
45 to 52D or more, which are also used to grade the
severity of keratoconus

38. CLASSIFICATION :
Based on severity of curvature
 Mild <45 D in both meridians
 Moderate 45-54 D in both meridians
 severe >54 D in both meridians

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

40. 2.Oval cone
• diameter(>5 mm.); often displaced inferiorly
• most common type of cone found,
especially in advanced keratoconus
• more difficult to fit with lenses

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

43. • Keratoconus is classified into four stages by amsler Krumeich et al.
STAGE 1
• Eccentric corneal steepness
• Myopia and/or astigmatism < 5D
• Corneal radius ≤ 48D
• Vogt’s striae - no corneal scar
STAGE 2
• Myopia and/or astigmatism > 5D < 8D
• Corneal radius ≤ 53 D
• No corneal scar
• Corneal thickness ≥ 400 µm

44. STAGE 3
• Myopia and/or astigmatism > 8D < 10D
• Corneal radius > 53D
• No corneal scar
• Corneal thickness 200-400 µm
STAGE 4
• Refractive error not measurable
• Corneal radius > 55D
• Corneal scar/perforation
• Corneal thickness 200 µm

45. • Corneal topography (formerly
k/a videokeratography )is a method
By which
corneal shape,
curvature,
power, and
irregularities are measured

46. COMPUTERISED CORNEAL TOPOGRAPHY
• Provides a color coded map of the corneal surface.
• The power in diopters of the steepest and flattest meridians
and their axes are calculated and displayed
• Steep curvatures are marked orange or red
• Flat curvature in blue or violet
• Normal curvatures in green or yellow

48. Keratocunus cornea
extreme asymmetrical
and inferior steepening
non-Keratoconus cornea
general symmetry overall
with no exsessive steepening

49. Topographic patterns of keratoconus :
• Inferior steepening without bowtie pattern specially more prominent
temporally
• Asymmetrical bow tie (AB) & inferior/superior steepening(IS-SS)
• Central steepening +/- superimposed with asymmetrical bowtie
pattern
• symmetric bow tie (AB) & skewed radial axes (SRAX)

51. Keratoconus pattern
Inferior steepening without bowtie pattern
specially more prominent temporally

52. Keratoconus pattern
asymmetrical bow tie (AB)& inferior steepening(IS)

53. Keratoconus pattern
asymmetrical bow tie (AB)& superior steepening(SS)

54. Keratoconus pattern
Central keratoconus central unusual steepening without bow tie

55. Keratoconus pattern
Central steepening, superimposed with asymmetrical bowtie- slightly
irregular astigmatism asymmetrical central hourglass

56. KERATOGLOBUS

57. Keratoconus pattern
asymmetrical bow tie & skewed radial axes (AB/SRAX)

58. Keratoconus pattern
symmetrical bow tie & skewed radial axes (AB/SRAX)

59. 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.

60. • DIAGNOSIS :
• The diagnosis of keratoconus is based on a
careful refraction,
slit lamp biomicroscopy,
keratometry and
corneal topography
• The clinical diagnosis requires the presence of localized corneal
thinning and protrusion, typically inferiorly or centrally

61. FORME FRUSTE KERATOCONUS/ KERATOCONUS-SUSPECT /
SUB CLINICAL KERATOCONUS/ TOPOGRAPHIC KERATOCONUS :
• No slit lamp signs of keratoconus,
• No scissoring on retinoscopy
• abnormal corneal topography (asymmetric bow tie with a skewed radial
axis)
• is it that imp to diagnose it ? These
patients are at increased risk of (post LASIK) corneal ectasia.
EARLY KERATOCONUS:
• No slit-lamp findings
• scissoring of the retinoscopic reflex with a fully dilated pupil examination
• abnormal corneal topography

62. Topographic pseudokeratoconus :
• The most common culprit is contact lens wear (both hard and soft),
which induces patterns of inferior steepening that may be very difficult
to distinguish from keratoconus.
• These patterns disappear with time after contact lens wear is
discontinued.
• may also result from technical errors during topographic procedure,
such as inferior eyeball compression while trying to retract the eye lids,
misalignment of the eye with inferior or superior rotation of the eye
ball and incomplete digitization of mires, causing formation of dry
spots, which simulates inferior steepening.

63. Pseudokeratoconus: (a) Shows axial topography of a normal subject of with the rule astigmatism.
(b) The same subject with the misalignment showing skewed radial axis mimicking keratoconus.
(c) An overlay of the eye image and (d) mires overlay show apparent misalignment

64. RABINOWITZ CRITERIA (1995) FOR DIAGNOSIS OF KERATOCONUS :
• central corneal power > 47.2 D
• inferior minus superior (I-S value) asymmetry >1.2 D
• Sim K astigmatism > 1.5 D, and (steep stimulated k )
• SRAX > 210 (skewed radial axes (SRAX) of astigmatism )

65. Rabinowitz/Rasheed's KISA% :
• KISA percent incorporates the K and I-S values with a measure,
quantifying the regular and irregular astigmatism into one index.
• KISA % = K × I-S asymmetry × AST (degree of regular corneal
astigmatism) × SRAX × 100
• This index is highly sensitive and specific in differentiating the normal
from keratoconic corneas.
• value of >100 % is highly s/o keratoconus
range from 60 to 100 % - keratoconus suspects.

66. DIFFERENTIAL DIAGNOSIS
• PELLUCID MARGINAL DEGENERATION
• KERATOGLOBUS
• POSTERIOR KERATOCONUS
• TERRIEN MARGINAL CORNEAL DEGENERATION:
-inflammatory disease that affects the superior limbus
-induces irregular against-the-rule astigmatism and
-corneal thinning (often with vascularization and lipid deposits)

67. Noninflammatory ectatic disorders – clinical presentation and appearance
compared
Clinical parameter keratoconus pellucid marginal
corneal degeneration
keratoglobus posterior keratoconus
Frequency MC LC Rare LC
Laterality Usually B/L B/L B/L Usually U/L
Age at onset PUBERTY Age 20- 40 yrs Usually At birth At birth
Location of thinning inferior paracentral Inferior band 1-2 mm
wide
greatest in periphery Paracentral posterior
excavation
Location of protrusion Apex of thinning Superior /inferior to
band of thinning
Generalised Usually none
Iron line Fleischer ring Sometimes None Sometimes
Scarring +MC Only after hydrops - +common
striae +MC Sometimes Sometimes rare

68. Clinical
parameter
keratoconus pellucid marginal
corneal degeneration
keratoglobus posterior keratoconus
Clinical
presentation
blurring of vision
Frequent Change of
eye glass prescription
Uncorrectable vision
to 6/6 with glasses
Decreased
vision d/t high irregular
astigmatism , Acute
hydrops rare
cornea is more
prone to rupture on
relatively mild
trauma
Can occur after trauma
Signs Conical ectasia,VS,MS,
FR,scissoring,oil drop
reflex
“Beer belly “band
thinning on cross
section
Globus ectasia dome-shaped posterior
excavation in the cornea which
may be small and
circumscribed (keratoconus
posticus circumscriptus)
or may be diffuse (keratoconus
posticus totalis)
Topography AB ,SRAX Bell shape ,crab claw Generalised
steepening
central steepened "cone"
coincident with the area of
circumscribed posterior
keratoconus as well as
paracentral flattening.

69. (A) Keratoconus; (B) pellucid marginal degeneration; (C) keratoglobus; and (D) posterior keratoconus.

70. Axial curvature map showing typical "crab claw"/"butterfly wing“
pattern of pellucid marginal degeneration

71. POSTERIOR KERATOCONUS

72. MANAGEMENT :
1. Glasses
2. Contact lenses
3. Refractive surgery
4. Collagen cross linking
5. Intracorneal rings
6. Deep anterior lamellar Keratoplasty
7. Penetrating Keratoplasty

73. 1.SPECTACLES :
• The management of keratoconus begins with spectacle correction.
• 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.
• Once glasses fail to provide adequate visual function, contact lens
fitting is required

74. CONTACT LENSES :
• In 1888, a French ophthalmologist, Eugene Kalt, began work on a crude
glass shell designed to “compress the steep conical apex thereby
correcting the condition.” This was the first known use of a
contact lens for keratoconus patients.
• 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.

75. • Contact lenses improve vision by means of
tear fluid filling the gap between the irregular corneal surface
and the smooth regular inner surface of the lens, thereby
creating the effect of a smoother cornea
• Fitting methods :
1. Three-point-touch design
2. Apical clearance
3. Flat fitting

76. 1. Three-point-touch design :
• Three-point-touch 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 ie., slight touch midperipherally at 3 and
9o’clock along the horizontal meridian
• 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.

77. • 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.
4 zones created
1.Central apical touch
2.Mid peripheral touch
at 3 &9’O clock
3.Paracentral clearance
4.Peripheral clearance
12 2
3
3
4

78. 2. Apical clearance
• 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
• advantages – reduction of central corneal scarring
• advantages 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.

79. Apical Clearance

80. 3. 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.

81. • Specially designed contact lenses for difficult to fit
keratoconus cases.
Soper lenses are one of the best known lenses.
This is a bicurve design with a steep central curve to accommodate
the cone and a flatter peripheral curve to align with peripheral cornea.
They are fitted by varying the sagittal depth of lenses.
Hybrid lenses
lenses with rigid gas permeable optic zone surrounded by a soft
zone to ensure a comfortable fit.
Soft or hybrid lenses do not however prove effective for every
patient.

82. Piggy-back lenses
• A hybrid lens
• they are known as piggy back because a RGP Lens is fitted on top of a
soft contact lens.
• provide excellent comfort and
good vision

83. Rose K lenses
• unique keratoconus lens design
• optical zone is reduced to snuggly fit the cornea
• complex computer-generated peripheral curves to fit the rest of the
irregular cornea.
• The system (26 lens set) incorporates a
triple peripheral curve system—standard, flat, steep
—in order to achieve the ideal edge lift of 0.8 mm

84. SCLERAL LENS :
• BSLP lenses are made of
Flurosilicone Acrylate Polmers
(Boston Scleral Lens Prosthesis)
(Fluid ventilated scleral lens)
• Its diameter range -15.5mm to 20mm
• They characteristically vault over the cornea and limbus and are
supported entirely by the sclera.
• the space created over the cornea is filled with non-preserved, buffered
sterile saline.
• The fluid lens smoothens the irregular cornea and provides good vision.

85. 3.REFRACTIVE SURGERY :
• LASIK or PRK is contraindicated because greater risk for
scarring and excessive thinning leading to post-LASIK corneal
ectasia.
• Thorough topographic evaluation should be done to rule out forme
fruste keratoconus or suspect before considering these refractive
procedures.
• Phototherapeutic keratectomy (PTK) has been described to be helpful
for some selected keratoconus patients to reduce steepness of the cone
in patients who have become contact lens intolerant.The resultant
flattening of the cone makes contact lens fitting easier

86. CORNEAL COLLAGEN CROSS-LINKING (C3R/CXL) :
• Cross-linking of collagen refers to the ability of collagen fibrils to form strong
chemical bonds with adjacent fibrils.
• In the cornea, collagen cross-linking occurs naturally with aging due to an
oxidative deamination reaction that takes place within the end chains of
collagen.
• Collagen cross-linking in the cornea is also observed in patients with diabetes
due to glycation

87. • The original method of therapeutic corneal cross-linking was
developed in Germany in 1998,the Dresden protocol, involves the use
of UVA light and riboflavin to form bonds between collagen fibrils.
• Although the exact mechanism is unknown, it is believed that
riboflavin causes the release of oxygen radicals that in turn induces an
oxidation reaction to create new cross-linking bonds between collagen
molecules

88. INDICATIONS
• Progressive keratoconus,
• post refractive ectasia,
• PMD
• pseudophakic bullous keratopathy
• infectious corneal melts because of the collagen-stabilizing effect of
CXL and the anti-infective effect of UVA light.

89. CONTRAINDICATIONS
• A minimum stromal thickness of 400 μm after epithelial removal is
required for safe CXL.
• In patients with corneas thinner than 400 μm, conventional CXL cannot
be performed. For such patients, either contact lens–assisted CXL
(CACXL) or hypotonic CXL is performed.
• 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.
• In such patients, it is indicated only if progression is documented

90. CONTRAINDICATIONS (contd)
• Corneal Scarring - central
• Vogt striae
• Dark micro striae in reticular pattern on confocal microscopy
• Steep K > 58 D
• Poor BCVA with hard contact lenses
• High BCVA – 6/9
• Active ocular disease - allergy
• Herpes keratitis
• Severe dry eye
• Children < 18 years
• Pregnancy and lactation
• Diabetes Mellitus

91. PROCEDURE :
• Removal of 8-9mm of epithelium under topical anaesthesia.
• Application of 0.1% riboflavin drops for 20 minutes for every 2 minutes
• Exposure to UV-A light with a wave length of 370 nm and irradiance of
3mw/cm2 for 30 minutes.

92. M.O.A

93. Technique of application

94. Dresden protocol developed by Prof. Theo Seiler & Prof. Eberhard Spoerl

97. EPI-OFF CXL: The standard protocol for CXL involves epithelial
debridement (epi-off)—an easy, relatively safe, and effective procedure
temporarily followed by pain decreased visual acuity .
• vision-threatening complications such as corneal infection, melting, and
even perforations have been reported in rare cases.
EPI-ON (TRANSEPITHELIAL) CXL: CXL without removing the epithelium.
• Epi-on is non invasive useful in cases where epithelial debridement is
ideally avoided, such as
uncooperative patients or
with additional ocular surface pathology, dry eyes, or very thin
corneas.
• The evidence so far is that epi-off CXL remains the most effective but
transepithelial methods are gaining ground

98. POST OP
• Healing of epithelial defect – 3-5 days
• Bandage contact lens / patching Cycloplegics,
• antibiotic ,
• NSAID & artificial tears eye drops
• Mild steroid eye drops for 3 – 6 weeks (FML 0.1%)
• Review at 1 week, 4 weeks, 12 weeks, 24 weeks and 1 year
• Topography, keratometry after 12 weeks
• Patient can start using old RGP Lenses after 2 weeks
• Temporary blurring of vision, FB sensation, pain
• Prednisolone eye drops for persisting haze

99. ADVANTAGES :
• Retards the progression of keratoconus.
• Decrease in astigmatism and corneal curvature and improvement in
vision.
• Topographical homogenitization of the cornea .
• Further improvement in vision can be achieved by combining cross-
linking with Intacs.

100. • Evidence of effectivity after CXL

101. Complications of C3R
• Corneal haze
• Diffuse lamellar keratitis
• Reactivation of viral keratitis and iritis
• Infective keratitis
• Corneal scarring
• Persistent corneal edema
• Corneal melt

102. CONTACT LENS–ASSISTED COLLAGEN CROSS-LINKING :
• Indicated in Pt with stromal thickness <400 µm
• use of hypo-osmolar Riboflavin 0.1% in 20% dextran solution
• The method of instillation is similar to standard CXL protocol .
• 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 .

103. • 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

104. PROCEDURE
• Preoperatively, lidocaine 2% & pilocarpine 2.0% are instilled twice to aid
in epithelialremoval and to promote miosis and reduce UVA exposure to
the lens and retina.
• The central 9 mm of corneal epithelium is abraded.
• a Soft lens Daily Disposable soft contact lens is immersed in isotonic
riboflavin for 30 minutes.
• use of hypo-osmolar Riboflavin 0.1% in 20% dextran solution

105. • At the end of 30 minutes, adequate corneal saturation with riboflavin is
confirmed by visualization of a green flare in the anterior chamber
using a slit lamp.
• The riboflavin-soaked contact lens is then applied on the corneal
surface & thickness is remeasured.
• Once confirmed to be more than 400 μm, treatment is continued.
central 9 mm of cornea is exposed to UVA light of 370 nm with an
irradiance of 3 mW/cm2 for 30 minutes.

106. TECHNIQUE

108. Conclusion :
• despite a reduction in irradiance from the corneal surface toward the
deeper layers of the corneal stroma, irradiation levels still exceed the
endothelial toxic threshold.
• It extends the benefit of safely undergoing cross-linking to a larger
number of patients with thin corneas .

109. ACCELERATED CXL :
• Based on reciprocity law of Bunsen Roscoe & has advantages of
decreasing treatment time while increasing intensity, keeping total
energy constant .
• The Bunsen-Roscoe law (BRL) of reciprocity states that a certain
biological effect is directly proportional to the total energy dose
irrespective of the administered regime.
• significantly reduces treatment time from one hour to a few minutes,
while maintaining same treatment dose as in conventional CXL.

111. • As an alternative to riboflavin formulations containing dextran, it 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).

112. LASIK Xtra
• Kanellopoulos in 2009 introduced concept of simultaneous CXL with
conventional LASIK. This has now been termed as LASIK Xtra.
• The procedure is indicated for individuals who are at higher risk of post
LASIK ectasia ,includes
• High myopes ,
• Borderline corneal pachymetry ,
• Asymmetry topography,
• Hyperopes ,
• Family history of keratoconus ,
• History of chronic ocular allergy .

113. Procedure for LASIK Xtra
• A variation of Riboflavin formulation is used which comes by the name
Vibex Xtra. This is 0.1%Riboflavin diluted in saline instead of Dextran.
• After lifting the LASIK flap, the flap is folded over itself in order to
prevent absorption of Riboflavin by the flap.
• A single drop of Vibex Xtra is placed over the exposed stromal bed and
carefully spread.

114. • Soaking of Riboflavin is continued for one minute and then the flap is
repositioned.
• Remaining Riboflavin is thoroughly washed from the stromal bed.
• Next high fluence cross linking is carried out at irradiation of 30 Mw/cm2
for 80 seconds.
• Just like LASIK procedure, the LASIK Xtra technique is also successfully
employed to re-treat previous interventions that were partly or
incompletely satisfactory.
• Generally, the procedure is bilateral, i.e. the sight defect is corrected in
both eyes in a single operating session

115. Advantages
• pain-free, both during and after the procedure.
• In addition to standard LASIK results, the LASIK Xtra technique restores
the strength of corneas weakened by LASIK.
• It enables normal activity to be resumed immediately: e.g. work and
sport.
• Furthermore, bilateral correction also notably facilitates postoperative
adjustment.

116. WHO CAN USE LASIK XTRA?
• The ideal candidate for LASIK Xtra has
a stable refraction,
healthy corneas and
certain physiological characteristics (essentially, an adequate corneal
thickness);
candidate must be highly motivated to reduce or eliminate any
dependence on glasses and lenses.
• There must be no other eye diseases present.
• For women at an advanced stage of pregnancy, it is preferable that they do
not undergo laser sight correction until their eyesight stabilises, after the
birth.
• Previous surgery is not a contraindication. Indeed, LASIK Xtra often perfects
unsatisfactory results of previous surgery.

117. RISKS AND COMPLICATIONS
• no major or serious events have ever been reported, involving loss of
the eye or of eyesight.
• Infection is extremely rare, but can be resolved with antibiotic
treatment.
• On rare occasions it may be the case that when vision has settled, the
results obtained do not fully meet expectations. This depends on the
natural reactivity of the eye which, if the treatments are equal, differs
from person to person.
• In these rare cases, termed “under-corrections” or “over-corrections”,
the extreme flexibility of the LASIK Xtra technique allows for a
subsequent intervention to perfect the results obtained, with no risk
for the patient

118. INTRASTROMAL CORNEAL RINGS :
Intrastromal corneal rings (Intacs) have been implanted for patients who
have become intolerant to contact lenses, but these have been found to
be more successful in modest than advanced disease

119. • Intrastromal corneal ring segments (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 ranging from 0.25 to 0.45 mm .
• Intacs segments act as passive spacing elements, act by
-shortening the arc length of the anterior corneal surface,
-flattening the central cornea
• provide biomechanical support to the thin ectatic cornea.
• The thickness of the inserts determines the amount of correction
achieved.

120. How INTACS Work…
•Inserts placed at 75% corneal depth
•Inserts separate corneal lamellae
•Separation shortens corneal arc length
•Central cornea flattens
•Increased flattening achieved with thicker segments

123. Surgical treatment Indications :
• When contact lenses no longer provide adequate acuity. Those whose
vision is not correctable to better than 6/9
• Also if thinning progresses toward the limbus such that keratoplasty
becomes more difficult and riskier.
• The various options available are
Penetrating keratoplasty(full thickness )
lamellar keratoplasty(partial thickness)
Deep anterior lamellar keratoplasty,

124. DALK
• In DALK the surgeon removes the corneal stroma to Descemet’s
membrane but preserves the healthy endothelium
• patient’s corneal endothelium is retained, giving additional structural
integrity to the post-graft cornea.
• As a graft rejection usually begins in the endothelium, the chance
of a rejection episode is greatly reduced.
• requires less recovery time.

125. • Best visual outcomes are achieved when the stroma is completely
dissected off Descemet’s membrane.
• DALK is probably the future of keratoplasty for many cases, but it has a
fairly steep learning curve and has risks of stromal rejection or corneal
perforation

126. Indications For DALK
• Corneal opacification with healthy
endothelium
• Keratoconus
• Stromal dystrophies
• Corneal scarring
• ocular surface diseases with limbal stem cell deficiency,
-Stevens-Johnson syndrome,
-ocular cicatricial pemphigoid and
-chemical/thermal burns.

127. Advantages Of DALK Vs PK :
• Less rejection
• Host endothelium is retained
• Avoid endothelial rejection
• Avoids intraocular penetration /positive pressure
• Expands donor pool/Donor tissue with low
endothelial cell count can be used for surgery
• Better refractive outcome
• Indicated in any corneal condition with healthy endothelium

128. • Earlier suture removal / visual
rehabilitation
• Less endothelial cell loss
• Less cataract formation
• Less corneal weakening

129. Disadvantages Of DALK Vs PK :
• Technically difficult technique
• Easy to convert to PK
• Longer duration of surgery
• Reduced quality of vision / best
corrected visual acuity
• Interface can serve as a plane for
vascularization / inflammation

130. • Phakic intraocular lens implantation has been recently
considered for keratoconus patients.
• Anterior chamber phakic intraocular lens have been combined with
INTACS with good results.
• Phakic lens corrects the major part of refractive error especially, high
myopia, and INTACS is used to correct the residual error.

131. REFERENCES :
Parson 22 nd edition
Yanoff 4th edition
Jacokbiec s priciples 3rd edition
Krachmer cornea 3rd edition
AAO 2016-17
Zia chaudhari 1st edition
Dutta 3rd edition
Ijo-issn-0301-4738 year-2013 volume-61issue-8page-394

132. THANK YOU

136. • Management of Acute Hydrops
• medically with hyperosmotics, oral and topical acetazolamide
and antiglaucoma medications.
• Intracameral air injection is a safe and useful therapy to shorten the
period of corneal edema in acute hydrops secondary to keratoconus.
The use of intracameral air, iso-expansile fluoropropane or sulfur
hexafluoride injections in management of acute hydrops in
keratoconus had been described.

137. Ref epi on & epioff
• https://www.aao.org/eyenet/article/cxl-corneal-ectasia-reshaping-
future-of-treatment-2