KERATOCONUS

Hasan A. Mokbel

Contact Lens Department

Medicals International

PRESENTATION OUTLINE :

What is Keratoconus ? (causes, types, related diseases….)

Management of Keratoconus/ available treatment options

Rose K family Clearkone

WHAT IS KERATOCONUS?

Keratoconus is a degenerative disorder of the eye in which structural changes within the cornea cause it to thin and change to a more conical shape than its normal gradual curve.

WHAT ARE THE CAUSES OF KERATOCONUS? Tiny fibers of protein in the eye called collagen help

hold the cornea in place and keep it from bulging. When these fibers become weak, they cannot hold the shape and the cornea becomes progressively more cone shaped.

WHAT ARE THE TYPES OF KERATOCONUS?

Classification can be according to : Shape :

1. Nipple Shape ( small size 5 mm)

2. Oval cone ( 5 to 6 mm )

3. Globus ( large , may involve 75 % of the cornea )

Severity of curvature :

1. Mild ( 45.00D)

2. Moderate (45.00 – 52.00 D)

3. Severe ( more than 52.00 D)

WHAT ARE THE OCULAR DISEASES RELATED TO KERATOCONUS ? Retinitis pigmentosa

a form of retinal dystrophy

Micro cornea An abnormally thin and flat cornea

Down syndrome  genetic disorder caused by the presence of all or part of a third copy

of chromosome 21

Irregular Astigmatism

TREATMENT & MANAGEMENT

TREATMENT Surgical & non-surgical treatment are available.

1. Surgical treatment includes :

Intacts ( intrastromal corneal ring segments ) Corneal transplant phakic IOL

2. Non surgical treatment : Contact Lenses Collagen Cross linking Spectacles

CL TREATMENT : At the early stages of Keratoconus spectacles and soft

lenses

are used to correct vision.

With the progression of the disease majority of the patients

will use rigid contact lens.

The very latest contact lens for treating Keratoconus is the synergize hybrid contact lens which is rigid at the middle and soft at the edges.

CL TREATMENT : RGP lenses provide good treatment by resurfacing

the irregular cornea and corrects astigmatism and provide good vision quality.

The majority of patients who used RGP witnessed a dramatic improvement.

Patients with contact lenses suffer mainly from uncomfortable long period wear due to dryness of the eye since there's no lubrication to prevent evaporation.

SPECIAL LENSES WITH BETTER FIT WITH THE SHAPE OF THE CORNEA The Rose K lens was invented by Paul Rose, an

optometrist from Hamilton, New Zealand.  Rose k lenses were made with complex geometry to

fit any type of cone shape cornea.

The Rose K family includes :

1. Rose K/K2

2. Rose K2 post graft

3. Rose K2 IC

4. Rose K2 XL

ROSE K LENSES The optical zone is reduced to fit the

cone and the peripheral curve is designed to fit the rest of the irregular cornea.

Lenses can be customized to suit each eye and can correct the myopia and astigmatism associated with the condition. 

ROSE K

The Rose K lens has a number of features that make it ideal for Keratoconus:

1. Its complex geometry can be customized to suit each eye and can correct all of the myopia

2. They are easy to insert, remove and clean.

3. They provide excellent health to the eye, because they allow the cornea to "breathe" oxygen directly through the lens.

4. Practitioners have the Rose K trial set fitting system which achieves a first fit success in over 80% of patients internationally.

5. They correct myopia and astigmatism associated with Keratoconus.

ROSE K2 Rose K2 is a refined Rose K lens which takes into

account the unusual corneal shapes of Keratoconus patients, which require abnormal curves on the back of the lens to fit the cornea optimally.

The Rose K2 lens minimizes these aberrations by applying very small changes to the curves on both the front and back of the lens in an attempt to bring the light passing through the lens within the pupil zone to a single point.

WHAT ARE THE BENEFITS OF ROSE K2 ? Easy fitting

Large parameter range available which makes fitting easier and lowers the chair time.

Advanced aberration control

Increased comfort

Indications :• Pellucid Marginal Degeneration - PMD• Keratoglobus more than 75% of cornea is involved

in the irregular shape• Post Lasik,Post Graft

• Same design as RoseK2 IC , reduced pool and reversed curves to allow proper healing after surgery.

Rose K Post Graft Lens for patients who have undergone penetrating keratoplasty. This lens is designed for postoperative recovery and improvement in vision.

ROSE K2 XL semi-scleral contact lens designed to vault the corneal surface and rest

on the less sensitive surface of the sclera, these lenses often are more comfortable for a person with Keratoconus. Also, scleral lenses are designed to fit with little or no lens movement during blinks, making them more stable.

Indicated for indicated for Keratoconus, PMD, Post Graft, and other irregular cornea conditions that cannot be successfully fitted within the limbus.

much larger than conventional GP lenses and rest near the junction between the cornea and the sclera.

FITTING STEPS1. Determine the corneal shape2. Central fit3. Peripheral fit4. Overall diameter5. Location6. Lens movement 7. Power

Lens selection with a back central optic radius ( BCOR) 0.2 mm steeper than the mean K reading.

Central fit : leather weight touch to the apex of the cone is desirable.

Peripheral fit : the peripheral fit should have a Fluorescein edge width 0.5 – 0.7 mm

Overall diameter : the standard diameter is 8.7 mm but smaller diameter can be used with steep cornea ( higher grade of Keratoconus)

Location of the lens should be maintained centrally ( any dislocation can be corrected by changing diameter , edge lift and back central optic radius (BCOR)

Lens movement with every blink the lens should move freely across the cornea then returns to its position and rests.

Determine the lens power by a carful over refraction +/- 1.00 D and refine by 0.5 and 0.25 D.

Vaults the irregular corneal forms  ClearKone® combines the best of both worlds – the

crisp vision of a high-oxygen rigid RGP contact lens with the all-day comfort and convenience of a soft lens.

The ClearKone® fitting approach called “vaulting” allows doctors to simply increase the depth of the contact lens over the cornea depending on how steep or severe the individual patient’s Keratoconus is.  The ClearKone® vault system comes in 11 different choices and therefore can accommodate even the most severe forms of Keratoconus.

Steps of fitting :

1. Vault selection

2. Skirt selection

3. Determine Lens power

1. Vault selection : Begin with 250µ Vault value in Medium skirt curve Insert the lens filled to the top with saline and a

drop of high molecular weight Fluorescein. Check for central bearing ,central pooling , or for

bubbles.

If central bearing is present then increase the vault by 100µ [ vault is too low ]

If central pooling is present then decrease the vault by 100µ [ vault is too high ]

2. Skirt Selection : Always start with the medium skirt curve

The lens will exhibit movement very similar to a soft lens

The ideal fit will show thinning at the ILZ ( inner landing zone ) and bearing in the OLZ (Outer Landing Zone) 

3. Determine Final Lens Power: If the over-refraction is greater than

4.00D adjust for vertex distance