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- 3. KERATOCONUS it is mostcommon ectatic corneal disorder characterized by noninflammatory and noninfective, progressive, bilateral thinning of the cornea with ectasia of conical shape and apical protrusion . It manifests by adolescence, resulting in considerable visual impairment owing to the development of high degree irregular myopic astigmatism.
- 4. ETIOLOGY Definite etiology isunknown. ENZYME THEORY Alteration in the levels of following enzymes have been noted: Increased level of epithelial lysosomalenzymes. Decreased level of alpha-1 proteinaseinhibitor in the epithelium. Decreased levels of glucose-6 phosphate dehydrogenasein the epithelium. CONNECTIVE TISSUE ABNORMALITY THEORY There is association of keratoconus withsomeconnective tissue disorders.
- 5. EYE RUBBING GENETIC THEORY Duetotheoccasionalassociation of trisomy-21 with keratoconus, genetic abnormality may be the cause. HORMONAL THEORY It isproposedbecauseofthe manifestations of the disease in adolescence. Habitualeyerubbing in some diseases like vernal catarrh, Down syndrome and poorly sighted patients of Leber’s tapetoretinaldegeneration are associated with keratoconus.
- 6. STAGE 2 Myopia and/orastigmatism > 5D < 8D Corneal radius 53 D No corneal ≤ scar Corneal thickness 400 µm ≥ Keratoconus is classified into four stages by a Amsler Krumeich STAGE1 Eccentric corneal steepness Myopia and/or astigmatism < 5D Corneal radius 48D ≤ Vogt’s striae - no corneal scar
- 7. STAGE 3 Myopia and/orastigmatism > 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
- 8. ASSOCIATIONS SYSTEMIC DISEASES Marfan’s syndrome Ehlers- Danlossyndrome Osteogenesis imperfecta Congenital hip dysplasia Oculodentodigital syndrome Rieger’s syndrome Crouzon’s syndrome Floppy eyelid syndrome Down syndrome Turners syndrome Atopic dermatitis Marfan syndrome Atopic dermatitis Crouzon syndrome Osteogenesis imperfecta Down syndromeEhlers-Danlos syndrome
- 9. Asthm a ASSOCIATED OCULAR DISORDERS Retinitispigmentos a Leberscongenitalamaurosis Blue sclerae Congenital cataract Aniridia Retinopathy of prematurity Fuchs dystrophy Posterior polymorphous dystrophy Granular and lattice dystrophy ALLERGIC CONDITIONS Spring catarrh
- 10. CLINICAL FEATURES -There is conicalprotrusion of the cornea with centralthinningandtheapexoftheconeisusually directed inferonasally. -Gradualdecreaseinvision, photophobia, -monocular diplopiaor monocular polyopia. -Severe photophobia and watering is seen in cases of hydrops. Particularly adolescent females are affected -Munson’s signis a V-shaped conformation of thelowerlidproducedbytheectaticcornea in downgaze.
- 11. -Rizzuti’s signis asharply focused beam of light near the nasal limbus, produced by lateral illumination of the cornea in patients with advanced keratoconus.
- 12. Slit lamp examination Prominentcorneal nerves Fleischer's Ring Slit lamp examination The Fleischerring 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
- 13. through the lid. Linesof Vogt: Small and brushlikelines, generally vertical but they can be oblique. Found in the deep layers of the stromaand form along the meridian of greatest curvature. Disappearwhen gentle pressure is exerted on the globe
- 14. Corneal Thinning: Significant thinning(up to 1/5th cornea thickness) in the advanced stages of the disease and a diagnostic criterion based on comparison of central and peripheral corneal thickness has been proposed. Additionally, as the disease progresses, the cone is often displaced inferiorly. The steepest part of the cornea (apex) is generally the thinnest.
- 15. Corneal Scarring: Sub-epithelialcornealscarring, notgenerally seen early, may occur as keratoconus progresses because of ruptures in Bowman's membrane which is then filled with connective tissue Deep opacity of the cornea are also common in keratoconus.
- 16. Corneal Hydrops: Corneal hydropsoccursin advanced cases, when Descemet'smembrane ruptures, aqueous flows into the cornea and reseals Keratoconuspatients who are having an acute episode of corneal hydropsreport a sudden loss of vision and a visible white spot on the cornea. Corneal hydrops causes edema and opacification. As Descemet'sregenerates, edema and opacification decreases. Occasionally, hydropscan benefit keratoconuspatients who have extremely steep corneas. If the cornea scars, a flatter cornea often results, making it easier to fit with a contact lens. An increased incidence of hydropshas also been reported in keratoconuspatients with Down's syndrome.
- 17. Diagnosi s -As the corneabulges outward, the amount of astigmatism increases due to progressive distortion of corneal surface -Early keratoconususually manifests as a small island of irregular astigmatism in the inferior paracentral cornea. These changes can easily be seen as irregular mires on keratometry readings and on corneal topography.
- 18. Many objective signsare present in keratoconus. Retinoscopyshows a scissoring reflex. On direct ophthalmoscopythere is a dark round shadow in the corneal midperipherydue to total internal reflection of the light surrounding the central bright red fundusreflex and separating it from the normal red peripheral reflex. It is called a Charleuxoil droplet reflex.
- 19. In astigmaticcornea uneven spacing of the rings,especiallyinferiorly-in the keratoconiccornea should be noted The central rings may show a tear- drop configuration termed "keratokyphosis".
- 20. PACHYMETRY Thinning inthe inferior quadrant can be diagnostic of keratoconus. Centralorparacentralcornealthicknessof less than 450 µm is abnormal. Slit lamp pachymetryshows thinning in the centre of the apex. Ultrasonic pachymetry shows exact thickness of cornea at different places.
- 21. Corneal topography Provides a colorcoded map of the corneal surface. The power in dioptersof 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
- 22. Manageme nt 1. 2. 3. 4. 5. 6. 7. Glasses Contact lenses Collagen crosslinking Intracorneal rings LASIK Xtra Penetrating Keratoplasty Deep anterior lamellar Keratoplasty
- 23. Spectacle s Mild keratoconuscanbe corrected with spectacles. Retinoscopyis difficult; a normal subjective Monocular keratoconusis usually best dealt with using spectacle correction. In this group of patients, motivation for contact lens wear tends to be poor. refraction is required.
- 24. Contact lenses first choice. Contact lenses areconsidered when vision is not correctible to6/9 by spectacles andpatientsbecome symptomatic. Rigid gas permeable (RGP) contact lenses are the lenses of 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.
- 25. Collagen cross linking Anewer 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.
- 26. Complications of C3R -Corneal haze Corneal melt -Diffuselamellar keratitis -Reactivationof viral keratitis -Infective keratitis -Corneal scarring - Persistentcorneal edema
- 27. LASIK Xtra LASIKXtrabasically means LASIK combined with C3R to treat Keratoconus and also for ectasia following LASIK surgery. LASIK Xtraembodies a proper evolution of LASIK technique, the refractive surgery technique which has received the most enthusiastic acclaim worldwide. This technique uses the excimer laser to remodel the curve of the cornea and surgically correct myopia, hypermetropia, astigmatism and presbyopiain a rapid and safe manner. Just like LASIK procedure, the LASIK Xtratechnique 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.
- 28. Advantages It is 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.
- 29. Intracorneal stromal rings Variouscorneal ring-kerarings, intacs. Act as passive spacing agents which flatten the cornea Made of PMMA thicker the ring more correction. On insertion they shorten the arc of ant corneal surface, iron out gross irregularities and in effect create a second limbus. Amount of correction depends on the ring thickness, more
- 30. to be thebest candidates. An important potential benefit of treating keratoconuswith INTACS inserts is to delay or eliminate the need for a corneal graft. Patientswithmildtomoderate keratoconusappear
- 31. Complications Undercorrection Overcorrectio n Migration of rings Extrusion orprogressive thinning New vessel formation glare /halos
- 32. Penetrating Keratoplasty place . The gold standard surgery Usuallytrephines between 8.0-8.5 mm are used. Success rate is more than 90%. In this procedure, the keratoconiccornea is prepared by removing the central area of the cornea, and a full-thickness corneal button is sutured in its Fleischer’s ring can be used as the limit of the conical cornea. Contact lenses are often required after this procedureforbest visualrehabilitation.
- 33. Deep Anterior Lamellar Keratoplasty Partialcorneal transplant. The cornea is removed to the depth of posterior stroma, and the donor button is sutured in place. This technique is technically difficult, and visual acuity is inferior to that obtained after penetrating keratoplasty. As a result, use of lamellar keratoplastyis largely confined to the treatment of large cones or keratoglobuswhen tectonic support is needed.
- 34. Thermokeratoplast y o transitory corneal haze odevelopmentof corneal scarring It allows a flatter contact lens to be fitted.. Rare procedure It involves placing a hot ring (Holmium yaglaser, 2100nm) along the base of the cone to heat and traumatize the cornea, resulting in a corneal scar which reduces the corneal curvature. The disadvantages of the procedure
- 35. Phakic iols Used tocorrect high myopia and associated astigmatism of selected keratoconus patients. Anterior chamber phakicintraocular lens have also beencombined with intacswith good results. The Intacs implantation is followed by toric phakic intraocular lens implantation o correct the residual myopic and astigmatic refractive error.
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