contact lens case reports
Using a Large Diameter RGP Lens
BY PATRICK J. CAROLINE, FCLSA, FAAO, & MARK P. ANDRÉ, FCLSA, FAAO
Patient JK is a 40-year-old male with a longstanding history of keratoconus OU. The patient had been wearing RGP lenses for 18 years and was interested in an alternative corrective option due to increasing lens awareness. In 2000, he underwent bilateral implantation of the intra-stromal Intacs rings (Figures 1a and 1b). The two PMMA arched segments are designed to flatten the central cornea by altering the peripheral corneal angle (Figure 2).
Figures 1a and 1b. The Intacs
intra-stromal implants OU for keratoconus.
On initial examination, the patient had an uncorrected visual acuity of OD 20/200 and OS 20/400. K readings were OD 44.12 @ 64/46.25 @ 154 with 2+ distortion and OS 48.75 @ 88/52.87 @ 178 with 4+ distortion (Figure 3). His best-corrected vision with spectacles was OD 20/50 and OS 20/80.
Figure 2. Intacs work by changing the peripheral corneal angle.
The patient was fitted with a new, large diameter RGP design, the Dyna-Intralimbal Lens from Lens Dynamics. This lens incorporates an 11.2mm overall diameter with a large 9.4mm optical zone (Figure 4). The design is extremely useful in corneas with high degrees of irregular astigmatism, such as keratoconus, post keratoplasty, post refractive surgery and pellucid marginal degeneration.
Figure 3. Post Intacs corneal mapping OU.
Fitting is always best performed through the use of diagnostic lenses; however, the initial base curve selection is always best estimated with the aid of corneal mapping. Clinical experience has shown that the radius of the initial diagnostic lens should be equal to the radius of the cornea 4.0mm from center on the temporal side. The appropriate diagnostic lens is placed on the eye and the lens/cornea relationship is evaluated with fluorescein.
The patient's final visual acuities with the lenses were stable at OD 20/25 OS 20/30 with an all day wearing time.
Figure 4. The 11.2mm Dyna-Intralimbal Lens Design in situ.
Patrick Caroline is an associate professor of optometry at Pacific University and an assistant professor of ophthalmology at the Oregon Health Sciences University.
Mark André is director of contact lens services at the Oregon Health Sciences University.