Keratoconus f dinesh
- 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
- 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
- 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