Specialty lens advances expand options for patients with corneal ectasia

September 15, 2014

Specialty lenses are filling the gap for patients with corneal ectasia who previously were considered intolerant of contact lenses.

 

Take-Home

Specialty lenses are filling the gap for patients with corneal ectasia who previously were considered intolerant of contact lenses.

 

 

By Lynda Charters; Reviewed by Deborah S. Jacobs, MD

Boston-Advances in specialty lenses are enhancing treatment options for corneal ectasia in patients who previously may have been intolerant of contact lenses.

“New designs and materials are more comfortable and physiologic,” said Deborah S. Jacobs, MD, medical director, Boston Foundation for Sight, Needham, and assistant clinical professor of ophthalmology, Harvard Medical School, Boston.

The initial treatments for corneal ectasia-which include keratoconus, pellucid marginal degeneration, keratoglobus, Terrien’s marginal degeneration, and post-LASIK ectasia-are correction of the refractive error using spectacles, soft spherical and toric lenses, and conventional rigid gas-permeable (RGP) lenses.

These options are best when myopia predominates over astigmatism and when the dominant eye is less affected. In addition, only RGP corneal lenses can correct irregular astigmatism, Dr. Jacobs noted.

With corneal ectasias it is less likely that the preferred RGP fit-lid attachment-can be achieved, because the corneal RGP lens moves to the steepest part of the cornea, which in the ectasias is typically inferiorily. The result is an intrapalpebral fit, which is inherently less stable. The only choice then is to fit “tight.” And therein lies the rub-the patient may end up as being intolerant to the contact lens because of instability with lenses “popping out” or because of scarring or discomfort because of apical bearing and hypoxia.

 

U.S. ophthalmologists lost interest in contact lenses 25 years ago because of the indisputable superiority of posterior chamber IOLs over contact lenses for cataract patients, and because of the advent of laser refractive surgery. Optometrists, opticians, and contact lens technicians in the United States abandoned RGP lenses in favor of soft contact lenses for correction of refractive error because of greater patient acceptance and ease of fitting.

As a result, Dr. Jacobs explained, “a small minority of contact lens fitters are interested, proficient, and up-to-date regarding innovations in contact lenses.”

The new specialty lenses comprise a new field in optometry and an area of growth in the global contact lens industry. She explained that now optometry graduates can do a residency-i.e., an additional year of clinical training after they earn the OD degree-to study cornea and contact lens, ocular diseases.

“Cornea- and contact lens-trained ODs are familiar and facile with the newest contact lens options and often train and work collaboratively with ophthalmologists,” she said. “The specialty lens is a growth area in the global contact lens industry.”

Specialty lenses

Among specialty lens options include RGP corneal lenses (keratoconus designs), piggyback systems, silicone hydrogel lenses (keratoconus designs), hybrid lenses, mini-scleral and scleral lenses, and prosthetic replacement of the ocular surface ecosystem (PROSE).

• RGP corneal lenses. These lenses provide innovative base curves to accommodate cone and innovative optics to neutralize the characteristic decentration and coma.

• Piggyback systems. These systems-involving placement of any hard contact lens over any soft contact lens-require creativity, according to Dr. Jacobs. Oxygen transmission decreases with thickness and the central and peripheral thicknesses vary with power.

Newer high-Dk materials-rigid and soft-are helpful. A soft lens with an anterior cutout to serve as a carrier, such as Flexlens (X.Cel) or plus power to stabilize corneal the RGP lens, can be used. These systems may fail with some patients because of acute hypoxia/overwear syndrome, chronic hypoxia/neovascularization, or handling issues.

 

Innovations in soft lenses, such as the Kerasoft IC (Bausch + Lomb) and NovaKone (Alden), offer a rigid modulus and large diameter, among other features, that result in mechanical stability and an optical neutralizing tear lens.

• Silicone hydrogel lenses and hybrid lenses. Specialty hybrid lenses for keratoconus were introduced in the 1980s, with SynergEyes lens arriving on the market (Quarter-Lambda Technologies and later SynergEyes) in 2001. The RGP optic has a Dk of 100, but the soft skirt has a Dk of only 9.3. These lenses were prone to failure because of junction fragility with handling. The design is prone to adherence with difficult removal and to chronic overwear syndrome, leading to reduced tolerance and wearing time.

Patients can also develop neovascularization from a combination of the low-Dk skirt, apical hypoxia, and apical bearing. The SynergEyes Duette hyper-Dk design introduced in 2010 has a RGP lens with a Dk of 130 and a silicone hydrogel soft skirt Dk of 83, which may address many of these issues, she noted.

• Mini-scleral and scleral lenses. The mini-scleral, semi-scleral, and corneoscleral lenses, e.g., the SoClear Lens (Art Optical) and the Mini-Scleral Design and One Fit Lens (both from Blanchard Contact Lens Inc.) are evolving with diameters ranging from 13 to 16 mm and high-Dk materials. These contact lenses may come into contact with the cornea at the apex and/or peripherally. The principles of fit are similar to those of RGP corneal lens. Alternatively, fitters seek to achieve a “scleral” fit with no corneal touch. With these lenses, the narrow bearing zone may lead to complications, according to Dr. Jacobs.

Scleral lenses, Jupiter Scleral (Medlens Innovations/Essilor), Tru-Scleral Lens (TruForm Optics), Macrolens (C&H Contact Lens Inc.), and Maxxim (Acculens) and others have a minimal diameter of 17.5 mm. “Scleral” fit is also typically understood not to contact the cornea. Historically scleral lenses were molded and were over 20 mm in diameter. These contemporary designs are typically dispensed in diameters of 17.5 to 19 mm, they are now cut on a lathe, and are made of the newer high-Dk materials.

• PROSE treatment of ectasia. The PROSE treatment-developed by the Boston Foundation for Sight-uses FDA-approved, custom prosthetic devices to replace or support the impaired ocular surface functions, Dr. Jacobs explained.

“A PROSE device does not touch the cornea,” she said. “The design vaults the cornea and the vault is independent of the base curve.”

 

The design includes a back-surface-bearing haptic that is not specified by superposition of spheres; there may be asymmetrical profiles; and typically, there is no movement on the eye.

In a study of a 2008 cohort of patients with ectasia (89 eyes of 59 patients), all eyes could be fitted with the device. Ninety-three percent of eyes achieved best-corrected visual acuity of 20/40 or better, and there was mean of 27.6-point improvement on the National Eye Institute Visual Function Questionnaire-25 (p > 0.001). Documented continued wear at 6 months was reported for 88% eyes.

“Satisfactory fit of a PROSE device was attained in all cases,” Dr. Jacobs said. “No cone was too steep. No eyes were excluded because of disease severity.”

 

Deborah S. Jacobs, MD

E: djacobs@bostonsight.org

Dr. Jacobs has no proprietary or financial interest in any contact lens or prosthetic device.