contact lens case reports
Single-Cut GPs for High Hyperopia
BY PATRICK J. CAROLINE, FAAO, & MARK P. ANDRÉ, FAAO
JS is a 32-year-old female who has an ocular history of congenital nanophthalmus, which is a rare, autosomal recessive form of microphthalmos. However, in contrast to microphthalmos, which is usually unilateral, the nanophthalmic patient presents with bilateral small globes and small, steep corneas.
Because the nanophthalmic's eyes have a short axial length of 14mm to 22mm, they are extremely hyperopic and have refractive errors ranging from +10.00D to +20.00D.
A Condition Full of Problems
Because nanophthalmic eyes fail to grow to the proper dimensions, the small globe volume and the crystalline lens, which is normal in size, result in an abnormally large lens/eye volume ratio (LEV ratio) of up to 30 percent. Normally the LEV ratio is about 4 percent.
As a consequence, the large LEV ratio causes the iris to displace forward, narrowing the anterior chamber. Peripheral anterior synechiae develop, resulting in angle-closure glaucoma. The condition is further complicated by peripheral choroidal detachment.
Checking on JS
In March, 2002 JS presented with a manifest refraction of +13.00D 20/50 OD and +12.50D 20/60 OS. Keratometry readings were 51.12 @ 90/51.37 @ 18 OD, 50.62 @ 8/51.50 @ 98 OS, axial lengths of 16.0mm OU and HVIDs of 10.8mm OU (Figure 1).
To compare, the left images in Figure 2 illustrate a normal eye with a normal HVID of 11.8mm; the right images illustrate JS's nanophthalmic left eye (note the small HVID and the shallow anterior chamber by Scheinpflug photography).
|Figure 1. JS's prefit corneal mapping.||Figure 2. Left images illustrate a normal cornea. The right images are JS's nanophthalmic eye.|
Succeeding in the End
We ultimately fit JS with the following small diameter, single-cut (non-lenticulated) GP lenses: BC 52.00 diopters, +14.50D, 8.0mm diameter OD and BC 51.50 diopters, +14.00D, 8.0mm diameter OS (Figure 3). Her visual acuities with the lenses were 20/40 OD and 20/50 OS. Today, the patient maintains a comfortable wearing schedule.
Figure 3. Patient's single-cut GP lens designs.
This particular case history provides a great illustration of the use of an often overlooked contact lens design that has always performed extremely well, especially on corneas that have a steeper radii of curvature (greater than 45.00 diopters).
Patrick Caroline is an associate professor of optometry at Pacific University and is 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 and serves as an adjunct assistant professor of optometry at Pacific University.