Contact Lens Update. A discussion of new (and old) lenses for keratoconus, post surgery, and severe dry eye. Cathy Wittman, OD Texas Tech University. Topography Review. The numbers (indices)
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A discussion of new (and old) lenses for keratoconus, post surgery, and severe dry eye.
Cathy Wittman, OD
Texas Tech University
The numbers (indices)
SimK: Simulated Keratometry: Instead of using two data points in each of two orthogonal meridians as in traditional keratometry, the topographer samples multiple points along the steepest and flattest meridians.
CEI: Corneal Eccentricity Index (aka E-VALUE): A measure of corneal eccentricity, a global shape factor.
Negative e-value: A negative e-value indicates a flat central zone with a steep mid-periphery (oblate surface).
Zero e-value: A perfectly spherical cornea.
Positive e-value: A cornea that is steep centrally and flattens peripherally (prolate surface). This is the most common.
The average e-value of the normal cornea is about 0.43.
Greater than 0.7 suspect keratoconus.
SAI: Surface Asymmetry Index (similar to the I-S Value- the Inferior-Superior Value):
Measures the difference in corneal powers at every ring (180 degrees apart) over the entire corneal surface). The I-S Value typically compares five points of the superior half of the cornea with five points of the inferior half.
Corneas with a difference of 1.4-1.9D within one meridian, suspect keratoconus. Over 1.9D highly suspect keratoconus.
Color Scale: Normalized and Absolute
Normalized: The color scale is normalized around the median dioptric value for that specific map.
Absolute: The color scale is fixed from map to map, so a certain color represents a certain dioptric value for every patient.
Pellucid Marginal Degeneration
If you are having trouble capturing a topo image, use thin disp SCL, NPATs, & have pt blink just before capture.
Penetrating injury caused corneal scarring nasally (blue) and distorted the pupil nasally. Because of the position of the “cone” superior temporally, all standard sized RGPs decentered temporally and caused the patient to see through the peripheral curves nasally.
BVA with specs 20/150
15.0mm Digiform-N Corneal-Scleral Lens
The Tru-Scleral lens by Truform has a diameter range of 16-20mm, with a standard size of 18mm that is vented by radial channels that are cut into the periphery. The Digiform corneal-scleral lens has a diameter range of 13.5 to 16mm. We have two fitting sets of 15.0mm lenses at TTU; the N (normal) and the K (keratoconic).
To avoid bubbles, have patients fill the lens with solution and look down when inserting the lens.
Remove using a DMV positioned close to the bottom edge of the lens or remove without a DMV using one finger at top edge and another finder at lower edge.
Biggest Caution: Do not fit this lens tightly!
Even though the lens is fenestrated, you can cause harm by fitting too tightly.
Let the lens sit in patient’s eye for 15 to 30 minutes and re-assess.
You cannot assess fit by looking at movement. Scleral lenses have minimal if any movement.
Observe for blanching vessels, NaFl indentions at lens edge, and difficulty removing the lens because of lens suction. These things mean the lens is too tight.
You should have tear exchange underneath the lens.
The Digiform also available in a post surgical fitting set.
Pt required a PKP OD because of a perforated cornea. Pt also required a partial tarsorrhaphy OD.
First presented to our clinic after being discharged from the burn unit after treatment of Stevens Johnson Syndrome.
Subconj Avastin injection given during follow up care after PKP for neovascularization.
Pt is using Vitamin A ointment in each eye.
Fit into Digifrom N1 15.0mm scleral lens by Truform.
Good apical clearance. The goal is no corneal contact to maintain thick tear layer between cornea and lens. (Pt is on Vitamin A ointment which is which is causing disruption of tear film on surface of the lens).
PKP patient who discontinued wearing her RGP six months ago due to discomfort and was 20/70 in that eye in her spectacles.
Digiform corneal-scleral 15.0, BC 7.4
Actually too flat. Nasal edge lift. Bearing. See next slide.
Digiform K1 15.0, BC 7.1
Edge lift eliminated. Nice NaFl pattern. Minimal bearing in flat meridian.
When the keratoconus has progressed to a point where you cannot eliminate the inferior edge lift caused by the cone, you can steepen the base curve in the inferior quadrant to “lip” the lens in and minimize edge lift.
I have found that if you decrease the overall diameter as much as possible without getting the peripheral curves into the pupil, you can minimize edge lift.TruformQuadrakone
Is not recommended for PKP patients.
Made of Hioxifilcon BRevitalEyes
Biggest complaint has been the Dk of the skirt. Low oxygen permeability has been attributed to neo and corneal edema.
Some practitioners feel the skirt can tighten over time contributing to less oxygen permeability and prefer piggyback (RGP with silicone hydrogel).
SynergEyes A: For patients with astigmatism
SynergEyes Mutifocal: For presbyopes
SynergEyes KC: For keratocones
SynergEyes PS: For post-surgical patients: PKP, refractive surgery, corneal traumaSynergeyes
Myopia, Hyperopia, and Astigmatism are Low Order Aberrations.
Aberrometers measure High Order Aberrations; Coma, Trefoil, Spherical Aberration, and Irregular Astigmatism.
Readings from the aberrometer are then used to design a lens. This is similar to the iZone spectacle lenses that are available.
Most dramatic results with patients who did not have a good outcome with refractive surgery.
Frequency and Proclear Multifocal contact lenses still working well. Proclear has a toric multifocal that we’ve had some success with.
Bausch and Lomb’s Purevision Multifocal is still working well.
Vistakon is coming out with a new multifocal.
Best clarity still with RGPs.
Dr. Ted Reid is doing research on a selenium coating that would give protection against microbial infection.
Pseudomonas Treated CL
Pseudomonas Untreated CL
Staph Aureus Treated CL
Staph Aureus Untreated CL
Collagen Crosslinking and Riboflavin (C3-R)
Over the course of a lifetime the cornea becomes progressively stiffer due to natural cross-linking between the collagen fibres.
Epi is abraded from the cornea and the riboflavin drops are applied. UV light is then focused onto the cornea for 30 minutes then a bandage contact lens is worn for 3-4 days.
This causes the cornea to become more rigid because riboflavin strongly absorbs UV light which increases the cross-linking of the collagen fibers.
Intacs Corneal Implant
Flattens the steep part of the cornea or cone to reduce vision distortions.
A demonstration and discussion of electronic low vision devices.
Cathy Wittman, OD
distance or near
Up to 16.5x on a 28” tv.
Made by Eschenbach.Videolupe Plus
Keratoconus: What Do We Know?: Eef van der Worp, BSc, FAAO, FIACLE http://www.clspectrum.com/article.aspx?article=100943
"Eccentricity" is in Against Thin: DIANNE ANDERSON, O.D., F.A.A.O. AND RANDY KOJIMA, F.O.A.A. http://www.optometric.com/article.aspx?article=102288
Contact Lenses and Wavefront Aberrometry: Kenneth A. Lebow, OD, FAAO http://www.clspectrum.com/article.aspx?article=102254
Post-Penetrating Keratoplasty: Association of Optometric Contact Lens Educators http://www.aocle.org/livlib/post_surgB.htm
Corneal Topography Tips: Paul M. Karpecki, OD http://www.optometric.com/article.aspx?article=5077
Validating Corneal Topography Maps: Randy Kojima, FOAA http://www.clspectrum.com/article.aspx?article=100638
Corneal Topography and Imaging: Michael W Fung, MDhttp://emedicine.medscape.com/article/1196836-overview
Advanced Keratoconus (hydrops): Bruce W. Anderson, OD http://gpli.info/education/book/case-39.htm
Contact Lens Case Report (VLK): Mark Andre, FAAO, Patrick Caroline, COT, FAAOhttp://www.clspectrum.com/article.aspx?article=12982
Dr. Cathy Wittman
Direct Office Line: 806-743-9500 ext 270