A New Hybrid Option for Keratoconus
PATRICK J. CAROLINE, FAAO, & MARK P. ANDRé, FAAO
Keratoconus is a condition of obscure etiology
that occurs in approximately 1 in 2,500 to 1 in 5,000 people. Reference to the condition
appears in the British literature as early as the mid-1700s, and today the condition occurs in almost
every region and every ethnicity worldwide.
Types of Keratoconus
In clinical practice, we've identified three distinct forms of
keratoconus: Puberty onset, late onset and form frust. The puberty onset form of
the condition begins in early adolescence at about ages 14 to 16. It's usually bilateral
with one eye affected worse than the other. Clinical experience has shown that often,
the earlier in life the keratoconus occurs, the more severe the condition becomes.
late onset keratoconus, the earliest signs and symptoms begin in the late 20s or
early 30s. It frequently affects both eyes to a similar degree, and unlike puberty
onset keratoconus, its progression is often significantly less severe and rarely
requires surgical intervention.
Form frust is an extremely mild and non-progressive form of keratoconus
that can occur anytime throughout life. The condition manifests as a central or
paracentral zone of irregular astigmatism of unknown etiology.
Figure 1. SynergEyes for keratoconus
The clinical management of keratoconus often varies with the severity
of the condition and can range from non-surgical options, such as glasses and contact
lenses, to surgical interventions, including corneal cross-linking, intra-stromal
inlays and penetrating keratoplasty. Contact lenses have been the preferred method
to optically manage the condition since 1888, and today a wide range of lens designs
and materials is available for keratoconus.
Hybrid lenses (a GP center and soft peripheral skirt) first appeared
in 1985 as the Saturn lens, with the later generation Softperm (CIBA Vision) design
launching in 1989. In September 2001, a California-based research group began developing
a new high-Dk hybrid lens that today is called SynergEyes (SynergEyes, Inc.). The
lens incorporates an 8.2mm aspheric high-Dk rigid center (Paragon HDS 100, Dk 100)
and a 31-percent water non-ionic soft lens skirt. The overall diameter of the lens
A Hybrid Lens Case
We've successfully fit the SynergEyes KC lens for keratoconic
patients such as FJ, a 34-year-old male who had a history of discomfort and decreased
wearing time with his traditional GPs.
The fitting procedure begins by selecting a diagnostic lens with
a base curve radius equal to the steepest K reading. We placed high-molecular-weight
fluorescein into the bowl of the lens and placed the lens on the eye. The GP portion
of the lens should exhibit slight apical clearance or "feather touch" across the
apex of the cone and midperipheral lens bearing (Figure 1). The soft lens skirt
should exhibit 0.25mm of blink-induced movement.
Today FJ enjoys 20/25 vision OU and all-day lens wear.
Patrick Caroline is an associate
professor of optometry at Pacific University and is an assistant professor of ophthalmology
at the Oregon Health Sciences University. He is also a consultant to Paragon Vision
Sciences and SynergEyes, Inc. Mark André is an associate professor of optometry
at Pacific University. He is also a consultant for Alcon Labs, CooperVision and
Contact Lens Spectrum, Issue: September 2006