Keratoconus
-
Upload
manoj-aryal -
Category
Health & Medicine
-
view
92 -
download
4
Transcript of Keratoconus
KERATOCONUS
Manoj Aryal IOM. MMC
PRESENTATION LAYOUT
• Introduction
• Aetiology
• Onset
• Clinical signs and symptoms
• Histopathology
• Classification
• Management
INTRODUCTION
• Greek word • Kerato : cornea Konos : cone
• First described by British ophthalmologist John Nottingham in 1854
• Most common corneal ectasia
• Incidence 1 in 2000
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.
AETIOLOGY
• Collagen abnormality
• Familial tendency
• Eye rubbing due to allergy
Aggravating factors
• UV exposure
• Poorly fitting contact lenses.
• Inflammation.
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
ASSOCIATED CONDITIONS: MULTI-SYSTEM
• Down’s Syndrome
• Marfan Syndrome
• Cruzan's Syndrome
• Ehlers-Danlos Syndrome
• Xeroderma pigmentosa
• Neurofibromatosis
• Osteogenesis imperfect• Turner’s Syndrome
ONSET
• Mean age of onset is age 16 years
• Shows no gender predilection and is bilateral in over 90% of cases.
• Develops asymmetrically
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
Corneal nerves• more prominent than in normal
eye
Vogt’s striaeFine vertical lines in the stroma and
Descemet’s membrane, Form along the meridian of greatest
curvature.• Disappear temporarily on digital pressure.
Fleischer’s ringIron pigment ring forms the base of
the cone. May be partial or complete.
• 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
• 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
ACUTE KERATOCONUS/CORNEAL HYDROPS
• Sudden loss of vision usually
associated with pain
• Acute, marked corneal edema,
often with fluid clefts in the stroma
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.
ACUTE KERATOCONUS/CORNEAL HYDROPS
• Managed with
• Patching or bandage contact lens
• Cycloplegia
• Hypertonic sodium chloride ointment and /or drops
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
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
CLASSIFICATIONBased 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
•Oval cone
• diameter(>5 mm.); often displaced inferiorly
• more difficult to fit with lenses
•Globus cone
• overall steepening
• diameter more than 6 mm diameter.
• 75% of cornea affected; most difficult to fit with lenses
Keratometer (Ophthalmometer )
Keratoscope :
• Placido disc• Photokeratoscopy • Video Keratoscopy (Computer
assisted topographic analysis.)
METHODS OF MEASUREMENT(DIAGNOSIS)
PrincipleUse of the first
Purkinje image.
• Consists of equally spaced alternating black & white lines.
PLACIDO DISC
• A luminous object (target of rings) is placed in front of patient’s cornea.
• Image size produced in the corneal reflection is measured
Circular Rings -Spherical cornea
Oval Rings –Regular astigmatism .
WTR astigmatism
ATR astigmatism
CLINICAL INTERPRETATION
With long vertical axis – Against the Rule Astigmatism.
• 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".
Cool colors (black, blue, azure) Flatter surfaces
Warm colors (orange, red, white) Steeper surfaces
Normal (green, yellow) Normal surfaces
CORNEAL TOPOGRAPHY
Bow- tie patterns indicate astigmatism
CLINICAL EXAMPLES
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
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
GLOBUS-SHAPED TOPOGRAPHY
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
FITTING PHILOSOPHIES FOR KERATOCONUS
WITH CONTACT LENS
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
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
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
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
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
RIGID GAS PERMEABLE LENSES
• Cost effective, easily available, suitable for mild to moderate keratoconus
• Fitting: three point conventional fitting philosophy
COMBINED LENS SYSTEM
Piggy back system
Hybrid lens system
Piggy back system
• Rigid lens fitted over a hydrogel lens increases comfort resulting in adequate wearing time with good vision
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
FULLY KERATONIC DESIGNED LENS
Rose k family of lens
SCLERAL AND MINI-SCLERAL LENS
Design to fit all irregular corneas which don’t tolerate any other RGP or hybrid/Soft lens
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.
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
THANK YOU