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) 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.
Topography Review 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.
Topography Review 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.
Topography Review 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.
Topography Review With-the-rule astigmatism
Topography Review Against-the-rule astigmatism
Topography Review Normal Cornea
Topography Review Pellucid Marginal Degeneration
Topography Review Keratoconus
Topography Tip BEFORE AFTER If you are having trouble capturing a topo image, use thin disp SCL, NPATs, & have pt blink just before capture.
Case #1 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
Case #1 20/60+ 15.0mm Digiform-N Corneal-Scleral Lens
Truform Tru-Scleral and Digiform CScleral 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.
Truform Tru-Scleral and Digiform 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.
Case #2: Stevens Johnson Syndrome 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.
Case #2 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).
Case #3 PKP patient who discontinued wearing her RGP six months ago due to discomfort and was 20/70 in that eye in her spectacles.
Case #3 Digiform corneal-scleral 15.0, BC 7.4 Actually too flat. Nasal edge lift. Bearing. See next slide.
Case #3 Digiform K1 15.0, BC 7.1 Edge lift eliminated. Nice NaFl pattern. Minimal bearing in flat meridian.
Fitting set recommended. We have a fitting set here at TTU. Works with most mild to moderate keratocones and some more advanced cones. If you cannot find a good fit with the Trukone, move on to the Quadrakone. TruformTrukone
Peripheral curve system can be altered in different quadrants, in order to provide a customized fit for each patient. They dot the steepest quadrant. 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
A soft contact lens developed by Metro Optics that is FDA approved for post laser refractive surgery patients. Is not recommended for PKP patients. Made of Hioxifilcon B RevitalEyes
Hybrid Lens with a rigid center and soft skirt. 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 trauma Synergeyes
Wavefront Technology 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.
Pediatric Contact Lenses • Silsoft • Made of Elastofilcon A • Can be worn overnight. • Parameters • Kontur • Cannot be slept in. • Occluder Lenses (can also use Adventures in Color) • Parameters • SpecialEyes • Made of Hioxifilcon • Any curve, any power, any axis
Mutifocal and Bifocal Contact Lenses 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.
R&D Here at TTU Dr. Ted Reid is doing research on a selenium coating that would give protection against microbial infection.
Selenium Treated Contact Lenses Pseudomonas Treated CL Pseudomonas Untreated CL