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