CASE FILES: HOW I FIT THESE IRREGULAR CORNEAS

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Today’s contact lens technology lets us address more challenges than in the past.

A 68-year-old white male with a history of keratoconus and dry eye presented complaining of frequent foreign-body sensation and limited tolerance of his gas permeable contact lenses, particularly on windy and pollen-filled days.

Refraction: OD -1.25 -1.00 x 40 20/30- and OS -2.50 -1.50 x 105 20/30-. A +2.50 add brought visual acuity to 20/25- in each eye.

Examination revealed apical thinning of the cornea without fibrosis, consistent with ectasia. There was diffuse mild epithelial basement membrane dystrophy and grade 1 apical staining. The contact lenses were fit well and showed good centration and movement. A divided support fluorescein pattern showed adequate axial edge lift.
While this patient appears to be doing well with a corneal contact lens, he could be doing better.

Today, we have a wide array of contact lens designs to address challenges that patients present with and, in some instances, delay the need for corneal transplant.

Semi-scleral gas permeable contact lens demonstrates minimal vaulting from limbus to limbus.

CASE 1: KERATOCONUS PATIENT
I refit the patient described above with the Zenlens toric, a gas permeable semi-scleral lens from Alden Optical, choosing the prolate design. At his follow-up visit, each lens was well centered with minimal movement and 75µm of clearance, and the lens rotation was 10 degrees counterclockwise. The slit lamp exam revealed grade 1 diffuse punctate epithelial keratitis in each eye.

We told the patient continue wearing these lenses until he was due for a replacement, at which time we would increase the sagittal depth to minimize any ocular surface compromise.

Discussion. This patient had a relatively modest presentation of keratoconus that appeared to be well managed with corneal contact lens designs. However, patients such as this typically have reported foreign-body sensation, poor lens stability, fluctuating vision, and, in some instances, limited tolerance and wear schedules.

By refitting this patient into a semi-scleral gas permeable design, we were able to address the limitations and improve his quality of life. All semi-scleral designs offer flexibility of altering sagittal depth and peripheral curve design to address comfort, hydration and ease of removal. Many even offer toric designs, as in this instance, to correct residual astigmatism and toric peripheral curves to facilitate comfort and orientation and even quadrant-specific alterations. The importance of the toric periphery relates to common variations in scleral curvature between the horizontal and vertical meridians.

When following these patients, be sure to watch for conjunctival impingement and blanching of conjunctival vessels under the periphery of the lens. This may be a sign of a tight peripheral curve system.

Some patients may find handling these newer lens designs to be cumbersome, yet they often are more comfortable, with greater lens stability, less dryness and increased wearing time. And, because centration is rarely an issue, visual quality is generally better with fewer haloes in low-light conditions.

One additional note: Contact lens care may have significant impact on patient acceptance and success. We generally recommend Boston ADVANCE cleaning and conditioning solutions from Bausch + Lomb and a nonpreserved saline solution such as ScleralFil, also from B+L.

This patient underwenet radial keratotomy in the mid-1990s. Note the long incisions approximating limbus and small, slightly decentered optical zone.

CASE 2: THE POST-RK PATIENT
A 57-year-old white female who underwent radial keratotomy (RK) in both eyes in the mid-1990s presented complaining of blurred vision. She wore a gas permeable reverse-geometry lens design and used readers, but she believed that she needed new lenses.

Her entering acuity was 20/40 in the right eye and 20/25 in the left. A +1.00D overrefraction in the right eye brought her to 20/25 in that eye as well. Her current lenses were well-centered with minimal movement.

Examination revealed 12-incision RK with T cuts in the right eye and eight-incision RK in the left eye. Both eyes had grade 2 punctate epithelial keratitis, mild neovascularization along the radial incisions, and hemosiderin stellate deposits centrally. Intraocular pressure was 20mm Hg in each eye.

Naked-eye refraction was +9.50 -6.00 x 115 for 20/60 in the right eye and +1.50 -1.50 x 50 for 20/30 in the left. A +2.25D brought her near acuity to 20/25+ in the right and 20/20- in the left.

We refit her with the Naturalens Scleral from Advanced Vision Technologies. Her acuity was 20/20 at distance in the right eye and J2 at near in the left. By fitting her with monovision, she would be much less dependent on her readers. The lenses showed 150µm clearance and minimal movement. There was no conjunctival impingement, and the patient reported excellent comfort.

Discussion. This patient had a history of myopic astigmatism before undergoing RK. Years later, she presents with hyperopic astigmatism. This is due to progressive central corneal flattening, which itself is due to the permanent compromise in corneal structural integrity that often occurs with aggressive RK. This patient most likely was highly myopic, which required deep incisions and a small optical zone to achieve the desired effect, but it also left her prone to consecutive hyperopia.

Compromised corneal integrity also can result in fluctuations in refractive error throughout the day. Because the corneal structure has been weakened, its topography can be affected by variations in diurnal IOP.

Without gas permeable contact lenses, this patient might require multiple spectacle prescriptions throughout the day. Due to the oblate surface of the cornea, however, corneal lenses often present centration problems and excessive edge lift. Reverse geometry and/or scleral contact lenses are the ideal and often only solution for these challenging cases.

Long corneal incisions that approximated the limbus can invite neovascularization, particularly in the presence of contact lens-induced hypoxia. The newer design semi-scleral contact lenses such as the Naturalens are designed to incorporate a generous pool of saline residing between the lens and the cornea to facilitate oxygen supply.

Here is a well-fit KeraSoft IC toric silicone hydrogel toric contact lens. Note the toric indicator at 6 o’clock.

CASE 3: SOFT KERATOCONIC DESIGN
A 55-year-old white female with advanced keratoconus presented complaining of discomfort in her current corneal gas permeable contact lenses.

Entering acuity was 20/20 at distance and J3 at near in the right eye and 20/25-2 at distance and J5 at near in the left. Refraction was -7.50 -2.00 x 80 for 20/30 in the right eye and -10.50 -2.25 x 40 for 20/60- in the left.

The slit lamp exam showed apical thinning without fibrosis, Vogt’s striae and Fleisher’s ring in both eyes and basement membrane dystrophy involving the visual axis in the left.

We refit the patient into the toric version of KeraSoft IC, a custom soft silicone hydrogel lens that was created in the U.K. and licensed to Bausch + Lomb. We fit her with a steep peripheral curve in the left eye and a standard peripheral curve in the right. Both lenses were well centered with appropriate movement and 0° of rotation, and the patient reported that the lenses were well tolerated.

Discussion. For years, we believed that soft contact lenses could not satisfy this population. By adhering to the fitting guide with KeraSoft IC, it’s possible to increase the success rate with this design. These lenses tend to move more generously than typical soft lenses and have a greater center thickness to help mask irregular astigmatism. The optic zone is larger, which helps avoid symptoms of flare.

Robert A. Ryan, OD, FAAO, is an associate professor in ophthalmology at Flaum Eye Institute at the University of Rochester Medical Center. He is actively engaged in contact lens specialty practice and clinical research.

WHERE TO FIND IT
Alden Optical, Inc.
800.253.3669 | AldenOptical.com

Advanced Vision Technologies
888.393.5374 | AVTlens.com

Bausch + Lomb
800.828.9030 | Bausch.com

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