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![Keratoconus
Features on topography [Rabinowitz et al]
-Central corneal power > 47D
-Diff. of 3D or more in corneal power of a point 3mm
superior to corneal vertex to that located 3mm
inferior to it (sup./inf. Ratio).
-Asymmetry in central corneal power between two
eyes > 1.4D.
-These findings have a sensitivity of 98% and a
specificity of 99.5% for the diagnosis of keratoconus.](https://image.slidesharecdn.com/keratoconuspowerpt-160308014245/85/Keratoconus-27-320.jpg)
![Keratoconus
Features on topography [Rabinowitz et al]
-Central corneal power > 47D
-Diff. of 3D or more in corneal power of a point 3mm
superior to corneal vertex to that located 3mm
inferior to it (sup./inf. Ratio).
-Asymmetry in central corneal power between two
eyes > 1.4D.
-These findings have a sensitivity of 98% and a
specificity of 99.5% for the diagnosis of keratoconus.](https://image.slidesharecdn.com/keratoconuspowerpt-160308014245/75/Keratoconus-27-2048.jpg)
Uploaded byTushya Parkash
Keratoconus
Keratoconus is a degenerative condition where the central cornea progressively thins and steepens, causing irregular astigmatism and vision changes. While the exact cause is unknown, risk factors include eye rubbing and genetic factors. Diagnosis is based on signs of corneal thinning, steepening, and irregularity seen on examination. Mild cases are managed with glasses or contact lenses, while more severe cases may require corneal collagen crosslinking or surgery.
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Keratoconus
- 1. KERATOCONUS DR TUSHYA OMPARKASH DR OM PARKASH EYE INSTITUTE
- 2. KERATOCONUS • Keratoconus isa degenerative non inflammatory disease of the cornea were the central or paracentral cornea undergoes progressive thinning and steepening causing myopia and both regular and irregular astigmatism
- 3. ETIOLOGY • Etiology isunknown • The hereditary pattern is neither prominent nor predictable,but positive family histories have been reported • The most common presentation of keratoconus is as a sporadic disorder, in which only a significant minority of patients exhibit a family history with autosomal dominant or recessive transmission • The incidence of keratoconus is often reported to be 1 in 2000 people
- 4. • Risk factorsinvolved are eye rubbing,associated with atopy, sleep apnea, Floppy lid syndrome, contact lens wear • Systemic and ocular associations 1. Systemic disorders: Down’s syndrome, Turner syndrome, Ehlers-Dunlos syndrome, Marfan syndrome,atopy, osteogenesis imperfecta, and mitral valve prolapse. 2. Ocular associations: Vernal disease, retinitis pigmentosa, blue sclera, aniridia, and ectopia lentis • Onset is at puberty and progresses slowly thereafter, it may become stationary
- 5. PATHOPHYSIOLOGY Increased levels ofproteases&catabolic enzymes Decreased levels of proteinase inhibitor Increased expression of IL-1 receptor Decreased collagen & keratin sulphate Increased levels of non proteinaceous substance Decreased stromal mass & apoptosis
- 6. PATHOLOGY • Classical Triad 1.Stromal thinning 2. Iron deposition in epithelium 3. Breaks in Bowman's layer (irregularity of basement membrane - earliest change)and fibrosis filling in the breaks that extend beneath the epithelium • With hydrops,breaks at the layer of Descemets membrane are seen.
- 7. Classification • Based onseverity of curvature mild-less than 48D moderate-48-54D severe->54D • Based on shape Nipple cone-<5 mmround shape; easiest to fit with contact lenses oval cone-5-6mm and steep curvature often displaced inferiorly; more difficult to fit with lenses globus cones-very large>6mm,75% of cornea affected; most difficult to fit with lenses
- 8. Clinical features • Symptomsare highly variable and, in part, depend on the stage of the progression of the disorder. Early in the disease there may be no symptoms, and kera- toconus may be noted by the ophthalmologist simply because the patient cannot be refracted to a clear 20/20 corrected vision. In advanced disease there is significant distortion of vision accompanied by pro- found visual loss. Patients with keratoconus fortunately never become totally blind from their disease. • Frequently changing spectacle Rx and axis of astigmatism • Diplopia • Glare at night • Haloes around lights • Blurred/ distorted vision
- 9. The classical signsof keratoconus External signs • Munsons sign is a V-shaped conformation of the lower lid produced by the ectatic cornea in downgaze.
- 10. External signs • Rizzutisign-It is a sharply focused beam of light near the nasal limbus, produced by lateral illumination of the cornea in patients with advanced keratoconus.
- 11. Slit lamp findings • Stromalthinning • Vogts striae-(Deep stromal stress lines) -Small and brushlike lines, generally vertical but they can be oblique. -Found in the deep layers of the stroma and form along the meridian of greatest curvature. -Disappear when gentle pressure is exerted on the globe through the lid.
- 12. Slit lamp findings • Ironring-(fleischer ring)The Fleischer ring is a yellow-brown to olive-green ring of pigment which may or may not completely surround the base of the cone -Formed when hemosiderin (iron) pigment is deposited deep in the epithelium -Fleischer’s ring often becomes thinner and more discrete with progression - Seen approximately 50% of all cases. -Locating this ring initially may be made easier by using a cobalt filter and carefully focusing on the superior half of the cornea's epithelium. Once located, the ring should be viewed in white light to assess its extent.
- 13. Slit lamp findings • Scarring-epithelial and sub epithelial (epithelial nebulae, anterior stromal scars, enlarged corneal nerves).Sub-epithelial corneal scarring, not generally seen early, may occur as keratoconus progresses because of ruptures in Bowman's membrane which is then filled with connective tissue
- 14. Retroillumination signs • Scissoringreflex on retinoscopy • oil droplet reflex/Charleaux sign on distant direct ophthalmoscopy
- 15. • Other signshave been described such as pulsation of the mires on AT • Videokeratography signs- -Localized increased surface power -Inferior superior dioptric asymmetry -Relative skewing of the steepest radial axes above and below the horizontal meridian • Photokeratoscopy signs- -Compression of mires inferotemporally (“egg-shaped” mires) -Compression of mires inferiorly or centrally below the horizontal meridian
- 16. Acute hydrops In somepatients who have keratoconus, acute rupture of Descemet’s mem- brane may occur and result in acute overhydration of the cornea and ac- cumulation of lakes of fluid within the corneal stroma. The overlying corneal epithelium may become edematous, and fluid may leak through the corneal epithelium. The ruptured Descemet’s membrane curls in on itself, and over time endothelial cells spread over the posterior stromal defect to lay down new Descemet’s membrane and recompensate the cornea.
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- 18. Corneal Pachymetry Slit lamppachymetry shows thinning in the centre of the apex. Ultrasonic pachymetry shows exact thickness of cornea at different places. Thinning in the inferior quadrant can be diagnostic of keratoconus. Central or paracentral corneal thickness of less than 450 µm is abnormal. If the reading decreases by nearly 20 µm towards the inferior periphery on successive pachymetric readings, it is suspicious of keratoconus. Increase in the progressive thinning of the cornea is a true index of keratoconus
- 19. Keratometer Keratometer is aninvaluable tool for measuring corneal curvature. Inability to superimpose central keratometric rings suggests irregular corneal astigmatism, a hallmark of keratoconus. There is no keratometric value beyond which diagnosis of keratoconus is definite. There are patients with steep corneas and high astigmatic errors who do not have keratoconus and, conversely, patients with keratoconus who have central corneas of normal steepness
- 20. Keratometer Inferior corneal steepeningis also an early sign of keratoconus. By performing central keratometry, followed by keratometry with the patient in upward gaze, steepening in the inferior cornea can be identified . Keratoscopy or videokeratography, based on Placido disk, can show In early keratoconus, a focal area of increased corneal curvature as an isolated area of smaller ring spacing and distortion. ring spacing decreases overall and becomes increasingly irregular on progression
- 21. Keratoscopy Keratoscopy uses apattern of concentric rings (mires) called a Placido disk with nine alternating bright and dark rings. The rings are reflected off the anterior cornea surface via Purkinje image number one and viewed directly by the clinician. The Placido disk is nothing more than a simple, inexpensive hand-held device with a central peep- hole for the clinician through which to look
- 22. Photokeratoscopy signs Compression ofmires inferotemporally (“egg-shaped” mires) Compression of mires inferiorly or centrally The photokeratoscope or topographer placido disc can provide an overview of the cornea and can show the relative steepness of any corneal area.
- 23. Computerised videokeratography • Commonly usedORBSAN • Elevation based maps with Placido disc capabilities • Gives: • -true elevation maps • -posterior corneal surface • -anterior corneal surface • -pachymetry • -AC depth • -features ray tracing,IOL calculation and 3D mapping software.
- 24. Forty images, 20with slit beams projected from the left and 20 from the right, are acquired in two intervals, each 0.7 seconds in duration. Simultaneously, a tracking system measures the involuntary movement of the eye during the exam.
- 25. COLOR CODED MAP GREEN-Normal YELLOW & RED- HOT (Steeper areas). BLUE- COOL (Flatter areas
- 26. Keratoconus pattern Keratoconus cornea- extremeasymmetrical and inferior steepening Non keratoconus cornea-general symmetry overall with no excessive steepening
- 27. Keratoconus Features on topography[Rabinowitz et al] -Central corneal power > 47D -Diff. of 3D or more in corneal power of a point 3mm superior to corneal vertex to that located 3mm inferior to it (sup./inf. Ratio). -Asymmetry in central corneal power between two eyes > 1.4D. -These findings have a sensitivity of 98% and a specificity of 99.5% for the diagnosis of keratoconus.
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- 31. Treatment • Conservative -Spectacles -Contact lens -CornealCollagen cross linking • Surgical -Intacs -Corneal transplant -Phakic IOLs -Recent advances
- 32. Spectacles • Mild keratoconuscan be corrected with spectacles. • Retinoscopy is difficult; a normal subjective refraction is required. • Monocular keratoconus is usually best dealt with using spectacle correction. • In this group of patients, motivation for contact lens wear tends to be poor.
- 33. Contact lenses Contact lensesare considered when vision is not correctible to 6/9 by spectacles and patients become symptomatic. Rigid gas permeable (RGP) contact lenses are the lenses of first choice. The aim is to provide the best vision possible with the maximum comfort so that the lenses can be worn for a long period of time.
- 34. Contact lenses • RGPcontact lens -It resurfaces the irregular cornea & the intervening fluid and corrects the irregular astigmatism to provide good quality of vision -However the disadvantage with these lenses is that they have standard lens design with fixed optical zones and do not give an ideal fit in patients with keratoconus -Many patients find them uncomfortable and can tolerate only for short time,the reason is that cornea steepens and rubs against the lens causing n abrasion and light sensitivity -Dry eye is another problem with them
- 35. Contact lenses Based onshape of cone Nipple cone : small diameter (5 mm.); round shape; easiest to fit with contact lenses Oval large diameter(>5 mm.); often displaced inferiorly; more difficult to fit with lenses Globus largest diameter (>6 mm.); 75% of cornea affected; most difficult to fit with lens
- 36. Contact lenses • Fittingmethods -Three point touch technique -Apical clearance -Flat fitting • Three-point-touch design-It actually refers to the area of apical central contact and two other areas of bearing or contact at the mid-periphery in the horizontal direction. The three-point-touch design is the most popular and the most widely fitted design The aim is to distribute the weight of the contact lens as evenly as possible between the cone and the peripheral cornea. The ideal fit should show an apical contact area of 2-3mm with mid-peripheral contact. Adequate edge clearance is required to ensure tear exchange.
- 38. Contact lenses Apical clearance Inthis type of fitting technique, the lens vaults the cone and clears the central cornea, resting on the paracentral cornea. These lenses tend to be small in diameter and have small optic zones The potential advantages of reducing central corneal scarring are outweighed by the disadvantages like poor tear film, corneal oedema, and poor visual acuity as a result of bubbles becoming trapped under the lens.
- 40. Contact lenses Flat fitting Theflat fitting method places almost the entire weight of the lens on the cone. The lens tends to be held in position by the top lid. Good visual acuity is obtained as a result of apical touch. Alignment can be obtained in early keratoconus; however, flat fitting lenses can lead to progression/ acceleration of apical changes and corneal abrasions. This type of fitting is useful where the apex of the cone is displaced
- 42. Contact lenses Piggy backlenses - RGP-CL fitted on top of a SOFT CL Can be used in pts who are uncomfortable with RGP wear, more so in pts prone to epithelial erosion at apex of cone ROSE-K lenses -are specially designed for keratoconic eyes to fit any type of cone.The optical zone is reduced to snugly fit the cone & the peripheral curve is computer designed to fit the rest of the irregular cornea
- 43. Contact lenses Scleral lenses Theyare made of special polymer called itaflurocon. Scleral lenses play a very significant role in cases of advanced keratoconus where corneal lenses do not work and corneal surgery is contra-indicated. Scleral lenses completely neutralise any corneal irregularity and can help patients maintain a normal quality of life Disadvantage is that they are difficult to use as they are large senses and cumbersome to the patients
- 45. Contact lenses • Soperlenses Custom made lens Two zones in the peripheral posterior curvature Central zone : to vault steep central cornea .It is of varying steepness depending of the patients cornea. Peripheral zone is with a 45D curvature designed to vault the mid periphery and limbal cornea
- 46. Contact lenses • Bostonscleral lens prosthetic device (BSLPD) The lenses are made of flurosilicone acrylate polymers with Dk values of 87 and 130. -Fluid ventilated scleral lens -Designed to enclose a bubble free reservoir of fluid over the corneal surface -Series of breaches are created between haptic bearing surface of the lens and underlying sclera -This will facilitate the aspiration of surface tears into the reservoir so that intrusion of air bubble during a blink is prevented. -Shape of haptic confirms exactly to that of underlying sclera to maintain functionality and prevents intrusion of air bubbles. -Very expensive
- 47. Medical therapy • Foracute corneal hydrops involves -A cycloplegic agent -Sodium chloride 5% ointment or eye drop -Lubricating eye drop -Steroid drops can be used if the eye is congested -A pressure patch -After the pressure patch is removed patients may still need to continue sodium chloride drops or ointment for several weeks to months. -Patients are advised to avoid vigorous eye rubbing
- 48. Collagen cross linking •A newer and less invasive technique that shows promise in keratoconus management is combined riboflavin-ultraviolet type A rays( UVA ) collagen cross-linking. • This procedure consists of photopolymerization of corneal stroma by combining vitamin B2 (photosensitizing substance) with UVA. • This process increases rigidity of corneal collagen and thus reduces the likelihood of further ectasia.
- 49. Corneal collagen crosslinking • Technique -Usingtopical anaesthesia, 7mm circle is marked on the cornea using a marker. -Epithelium of the marked area is scraped off using a blunt spatula. -A corneal abrasion is created to facilitate riboflavin diffusion into the cornea. -One drop of riboflavin 0.1% and 20% dextran ophthalmic solution is instilled topically in the eye every 2 minutes for 30 minutes. -At the end of the 30-minute pretreatment period, the eye is examined with blue light for the presence of a yellow flare in the anterior chamber, indicating adequate riboflavin saturation of the corneal tissue.
- 50. Corneal collagen cross linking -Whenthe yellow flare in the anterior chamber is confirmed, the eye is aligned under the UV-A light -The correct aperture setting is selected for the size of the eye; the eye is irradiated at 3Mw/cm2 for 30 minutes at wavelength of 370nm, during which time instillation of riboflavin is continued (one drop every 5 minutes).
- 51. -After completion ofthe procedure,eye is washed with BSS , an antibiotic drop is instilled and a bandage contact lens is applied. -The contact lens is removed once the abrasion has healed. -Postoperative medications include an antibiotic and a steroid(controversial) for 2 weeks postoperatively. -Complications of C3R Corneal haze Diffuse lamellar keratitis Reactivation of viral keratitis and iritis Infective keratitis Corneal scarring Persistent corneal edema Corneal melt
- 52. -mild to moderatekeratoconus -post refractive ectasia -PMD Contraindications -A minimum stromal thickness of 400 μm after epithelial removal is required for safe CXL. -In patients with corneas thinner than this, conventional CXL cannot be performed. For such patients, either contact lens–assisted CXL (CACXL) or hypotonic CXL is performed. -CXL is also not performed in patients with stable, nonprogressive keratoconus. Keratoconus is generally likely to be nonprogressive in patients older than 35 years because of naturally occurring cross- linking occurring with age. Indications
- 53. Contact lens-Assisted collagen cross-linking Itis possible that some corneas do not swell enough to make hypo-osmolar CXL possible. CACXL has advantage of not being dependent on swelling properties of the cornea . In CACXL, thickness of cornea is artificially increased by increasing amount of riboflavin-containing substance anterior to the stroma, increasing functional corneal thickness. using precorneal riboflavin film, a riboflavin- soaked soft contact lens , and a pre–contact lens riboflavin film
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- 56. Accelerated C3R As analternative to riboflavin formulations containing dextran, the KXL uses riboflavin 0.1% in hydroxypropyl methylcellulose (Vibex Rapid™, Avedro, Inc.). initial procedure is similar to conventional CXL of epithelial debridement. Vibex is then administered topically for 10 minutes. The cornea is then exposed to 365 nm UVA light with the CXL system for three minutes at an irradiance level of 30 mW/cm2 (accelerated CXL).
- 57. Intracorneal ring segments inkeratoconus • A method for flattening the cornea that is too steep and making a patient more contact lens tolerant is the insertion of INTACS into the cornea • This procedure is good for patients who are contact lens intolerant and who want to avoid a corneal transplant and whose k reading are not in excess of 58 diopters • INTACS have been approved for the treatment of mild to moderate keratinous in patients who are contact lens intolerant
- 58. Intracorneal ring segments •In these cases, patients must have a clear central cornea and a corneal thickness of >450 microns where the segments are inserted,approximately at 7mm optical zone • INTACS have crescent shaped two 150-degree PMMA segments that are surgically placed in the peripheral cornea at two-thirds corneal depth • INTACS comes in thickness from 0.25 to 0.45 mm in 0.05mm increments • INTACS correct the myopia and irregular astigmatism by producing a mechanical flattening of the central cone
- 59. Intracorneal ring segments •The advantage INTACS is that they require no removal of corneal tissue.no intraocular incision,and leave the central cornea untouched • Most patients will need spectacles/contact lens postoperatively for best vision,but will have flatter corneas and easier use of lenses • If a patient does not gain the expected results, the INTACS can be removed and then other surgical options can be considered
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- 61. Intracorneal ring segments •Types 1.Ferrara ring 2.Keraring 3.INTACS
- 62. Intracorneal ring segments Implantationof intracorneal ring segments with support from • Femtosecond laser technology allows realization with very high • During surgery stress on the cornea is minimal, because only m • The risk of infection is significantly reduced
- 63. Intracorneal ring segments Complications Undercorrection Overcorrection Migrationof rings Extrusion or progressive thinning New vessel formation glare /halos
- 64. Lamellar keratoplasty -LKP hasbeen shown to result in less endothelial cell loss, less IOP problems than PKP , a reduction in rejection episodes, &, in some cases, a reduction of induced astigmatism. -This technique requires less recovery time, and poses less chance for corneal graft rejection or failure. -However, while some series have achieved comparable visual outcomes, others have demonstrated that penetrating techniques slightly outperform deep lamellar procedure.
- 65. LK • Indications ofDALK regarding KC: Anterior corneal scars Advanced disease with stress lines and clear cornea K-max > 65 dpt Thinnest location < 350 m Very high refractive error (sphere > −6 and/or cylinder > −6)
- 66. Penetrating keratoplasty Between 10%& 25% of cases of KC progress to point where visual rehabilitation is no longer possible, especially in those who present at a young age (younger than 20) and with keratometry measurements > 60 dpt & corneal thickness < 400 m at the thinnest location. In the past, such patients have had only one option: a full thickness corneal transplant . KC is one of the most common indications for penetrating keratoplasty accounting for 15–25% of such surgeries
- 67. Penetrating keratoplasty As thecornea is avascular, the donor and host do not have to be tissue matched and eye banks – after checking for communicable diseases and tissue quality – can provide suitable tissue within a few days or weeks. Following surgery, visual recovery takes several weeks/ months, with full stabilization often taking up to a year after which time the sutures can be removed.
- 68. PKP Corneal transplantation inKC is considered relatively low risk, in terms of graft rejection and other postoperative complications, as these eyes do not typically exhibit corneal neovascularization. Despite these facts, there are reported complications such as allograft rejection, iatrogenic astigmatism, significant endothelial cell loss .
- 69. PKP When the lifeexpectancy is long, side effects caused by long-term use of topical steroids (e.g., secondary glaucoma and cataract), and recurrence of KC on the graft itself. Clear grafts are obtained in 95% of cases but optical outcomes may be unsatisfactory because of the iatrogenic astigmatism and anisometropia. Between 30% and 50% of grafted eyes still require contact lens correction for best acuity or further keratorefractive surgical procedures
- 70. Phakic IOLS Used tocorrect high myopia and associated astigmatism of selected keratoconus patients. Anterior chamber phakic intraocular lens have also been combined with intacs with good results. The Intacs implantation is followed by toric phakic intraocular lens implantation to correct the residual myopic and astigmatic refractive error
- 71. Recent Advances • KeraflexKXL -It is the newest procedure under investigation for the treatment of keratinous -It is non incisional and reshapes the cornea without removing any tissue -It is currently under clinical investigation in Europe for treating myopia and keratoconus -It involves the delivery of a single low energy microwave pulse lasting less than one second to the cornea -Energy is applied to the cornea using a dielectrically shielded microwave emitter which contacts the epithelial surface -Through capacitive coupling, the single pulse raises the temperature of the selected region of corneal stroma to approximately 65 degree celsius, forming a doughnut shaped area of collagen shrinkage in the upper 150 microns of the stroma
- 72. • The lesioncreated during keraflex is intended to flatten the central cornea both to decrease the cone in keratoconus and to achieve myopic correction • In order to improve the stability of the cornea with keraflex, Keraflex KXL includes focal corneal collagen cross linking • After the actual Keraflex procedure, riboflavin drops are administered over the treatment area, a mask is applied to protect the central and peripheral areas of the cornea, and uv light is administered to crosslink the collagen.
- 73. Final Summary -Anyone withprogressive ectasia should undergo CXL no matter what age or level of vision (assuming the eye was an appropriate candidate). not to proceed with surgery (other than CXL) -If patients were satisfied with their vision with glasses or contact lenses. ICRS may be considered. phakic IOLs should be used less often
- 74. Final summary -A strongpreference for DALK when a corneal transplant was needed, unless eye had previous compromise of Descemet membrane (most commonly from acute hydrops), at which point the preference is for a PK. - pdDALK may be considered even in the presence of previous hydrops.