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Keratoconus

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Keratoconus

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Keratoconus

  1. 1. KERATOCONUS Manoj Aryal IOM. MMC
  2. 2. PRESENTATION LAYOUT • Introduction • Aetiology • Onset • Clinical signs and symptoms • Histopathology • Classification • Management
  3. 3. INTRODUCTION • Greek word • Kerato : cornea Konos : cone • First described by British ophthalmologist John Nottingham in 1854 • Most common corneal ectasia • Incidence 1 in 2000
  4. 4. INTRODUCTION • Non-inflammatory, progressive thinning of the cornea that results in apical protrusion (ectasia) resulting in a high degree of irregular myopic astigmatism with observable structural changes appearing in later stages.
  5. 5. AETIOLOGY • Collagen abnormality • Familial tendency • Eye rubbing due to allergy Aggravating factors • UV exposure • Poorly fitting contact lenses. • Inflammation.
  6. 6. ASSOCIATED CONDITIONS: OCULAR • Retinitis pigmetosa • Retinopathy of prematurity • Ankyloblepharon • Floppy eyelid syndrome • Gyrate atrophy • Leber’s congenital amaurosis • Vernal conjunctivitis • Atopic dermatitis • Micro cornea • Blue Sclera • Aniridia • Congenital cataract • Persistent pupillary membrane • Posterior lenticonus
  7. 7. ASSOCIATED CONDITIONS: MULTI-SYSTEM • Down’s Syndrome • Marfan Syndrome • Cruzan's Syndrome • Ehlers-Danlos Syndrome • Xeroderma pigmentosa • Neurofibromatosis • Osteogenesis imperfect • Turner’s Syndrome
  8. 8. ONSET • Mean age of onset is age 16 years • Shows no gender predilection and is bilateral in over 90% of cases. • Develops asymmetrically
  9. 9.  Frequently changing spectacle Rx and axis of astigmatism  Ghosting/ monocular diplopia  Glare at night  Haloes around lights Blurred/ distorted vision  Scissors reflex (swirling retinoscopy reflex)  Distorted/ irregular Keratometer mires with steep readings  Prominent corneal nerves Signs Symptoms
  10. 10. Corneal nerves • more prominent than in normal eye Vogt’s striae Fine vertical lines in the stroma and Descemet’s membrane, Form along the meridian of greatest curvature. • Disappear temporarily on digital pressure. Fleischer’s ring Iron pigment ring forms the base of the cone. May be partial or complete.
  11. 11. • Corneal thinning •Visible in the central-inferior region in moderate and advanced Keratoconus. •Represents an actual reduction in the number of stromal lamellae • Munson’s sign •Ectasic protrusion of the cornea on down gaze produces a V-shaped conformation of the lower lid. • Rizzuit sign •Lateral illumination of the cornea produces a steeply focused beam of light near the limbus. Moderate: beam central to limbus. Advanced: beam displaced peripherally
  12. 12. •Corneal scarring • Sub-epithelial corneal scarring, not generally seen early, may occur as keratoconus progresses because of ruptures in Bowman's membrane which is then filled with connective tissue •Corneal hydrops • Occurs, generally in advanced cases, when Descemet's membrane ruptures, aqueous flows into the cornea and reseals
  13. 13. ACUTE KERATOCONUS/CORNEAL HYDROPS • Sudden loss of vision usually associated with pain • Acute, marked corneal edema, often with fluid clefts in the stroma
  14. 14. ACUTE KERATOCONUS/CORNEAL HYDROPS Resolves over a period of weeks to months Results in corneal scarring and flattening, with or without corneal neovascularization. Rarely, complicated by corneal perforation.
  15. 15. ACUTE KERATOCONUS/CORNEAL HYDROPS • Managed with • Patching or bandage contact lens • Cycloplegia • Hypertonic sodium chloride ointment and /or drops
  16. 16. HISTOPATHOLOGY: • Fragmentation of Bowman layer • Thinning of the stroma and overlying epithelium • Folds or breaks in Descemet's membrane • Fleischer ring: Ferritin particles accumulate within and between the epithelial cells, particularly in the basal epithelium
  17. 17. CLASSIFICATION Based on severity of curvature  Mild <45 D in both meridians  Moderate 45-52 D in both meridians  Advanced >52 D in both meridians  Severe >62 D in both meridians
  18. 18. CLASSIFICATION Based on type of cones • Round or nipple • Cone-lies in centre towards inferior nasal quadrant • Most common, • less than 5 mm in diameter • Easiest to fit with contact lenses
  19. 19. • Oval cone • diameter(>5 mm.); often displaced inferiorly • more difficult to fit with lenses
  20. 20. • Globus cone • overall steepening • diameter more than 6 mm diameter. • 75% of cornea affected; most difficult to fit with lenses
  21. 21. Keratometer (Ophthalmometer ) Keratoscope : • Placido disc • Photokeratoscopy • Video Keratoscopy (Computer assisted topographic analysis.) METHODS OF MEASUREMENT(DIAGNOSIS)
  22. 22.  Principle  Use of the first Purkinje image. • Consists of equally spaced alternating black & white lines. PLACIDO DISC
  23. 23. • A luminous object (target of rings) is placed in front of patient’s cornea. • Image size produced in the corneal reflection is measured
  24. 24.  Circular Rings -Spherical cornea  Oval Rings –Regular astigmatism .  WTR astigmatism  ATR astigmatism CLINICAL INTERPRETATION With long vertical axis – Against the Rule Astigmatism.
  25. 25. • Photokeratoscope • The even separation of the rings in the spherical cornea. • In astigmatic cornea uneven spacing of the rings-- especially inferiorly • The central rings may show a tear-drop configuration termed "keratokyphosis".
  26. 26. Cool colors (black, blue, azure) Flatter surfaces Warm colors (orange, red, white) Steeper surfaces Normal (green, yellow) Normal surfaces CORNEAL TOPOGRAPHY
  27. 27.  Bow- tie patterns indicate astigmatism CLINICAL EXAMPLES
  28. 28. Small, near central ectasia, less than 5.0 mm in cord diameter NIPPLE-SHAPED TOPOGRAPHY May manifest as moderate to high with-the-rule corneal astigmatism
  29. 29. In advanced keratoconus. Corneal apex is displaced well below the midline resulting in varying degrees of inferior mid-peripheral steepening. Kissing pigeon pattern (diagnostic of PMD) OVAL SHAPED TOPOGRAPHY
  30. 30. GLOBUS-SHAPED TOPOGRAPHY
  31. 31. Spectacles • Mild keratoconus in early stage can be corrected with spectacles. • As the cornea steepens and becomes more irregular, glasses not capable of providing adequate visual improvement. MANAGEMENT
  32. 32. FITTING PHILOSOPHIES FOR KERATOCONUS WITH CONTACT LENS
  33. 33. 1. FLAT FITTING • The flat fitting method places almost the entire weight of the lens on the cone • Good visual acuity is obtained as a result of apical touch. • Alignment can be obtained in early keratoconus; however, flat fitting lenses can lead to progression/ acceleration of apical changes and corneal abrasions
  34. 34. 2. APICAL CLEARANCE • The lens vaults the cone and clears the central cornea, resting on the paracentral cornea • Apical clearance would minimize trauma to the central cornea • The potential advantages of reducing central corneal scarring are outweighed by the disadvantages of poor tear film, corneal edema, and poor visual acuity as a result of bubbles becoming trapped under the lens
  35. 35. 3. THREE-POINT TOUCH • The aim is to distribute the weight of the contact lens as evenly as possible between the cone and the peripheral cornea. • lens lightly touches the peak of the cone then a very low vault over the edges of the cone, and lastly a thin band of touching near the edge of the lens
  36. 36. Contact lenses • Soft contact lenses • Rigid gas permeable lenses • Combined lens system • Piggy back system • Hybrid lens system • Fully keratonic designed lenses • Rose k family of lens • Scleral and mini scleral lens
  37. 37. SOFT CONTACT LENSES • It is not better than spectacle lens but it works in piggy back system • At very early stage, this way work as equal to spectacle does. • But patient may not be satisfied with the level of vision he has even though it is 6/6 • Shadow effect of texts • Ghosting of image • Poor night vision • Eye fatigue on prolong reading
  38. 38. RIGID GAS PERMEABLE LENSES • Cost effective, easily available, suitable for mild to moderate keratoconus • Fitting: three point conventional fitting philosophy
  39. 39. COMBINED LENS SYSTEM Piggy back system  Hybrid lens system
  40. 40. Piggy back system • Rigid lens fitted over a hydrogel lens increases comfort resulting in adequate wearing time with good vision
  41. 41. Hybrid lens system • One way to overcome the problems with piggy-back lenses, yet have the optics of a rigid lens with the comfort of a hydrogel, is to fuse a soft rim onto a hard central portion
  42. 42. FULLY KERATONIC DESIGNED LENS Rose k family of lens
  43. 43. SCLERAL AND MINI-SCLERAL LENS Design to fit all irregular corneas which don’t tolerate any other RGP or hybrid/Soft lens
  44. 44. COLLAGEN CROSS-LINKING (CXL OR C3-R) • It may slow or halt the progression of keratoconus by using a photo-oxidative treatment to increase the rigidity of the corneal stroma.
  45. 45. KERATOPLASTY • For patients Intolerant to contact lens and cases with scarring • Penetrating keratoplasty and Deep anterior lamellar keratoplasty can be done • Patient may have to continue contact lens ,but will have better tolerance

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