Correcting High Astigmatism
pediatric and teen cl care
Correcting High Astigmatism
BY MARJORIE J. RAH, OD, PHD, & JEFFREY J. WALLINE, OD, PHD
A 9-year-old female international patient presented with a history of poor success with contact lenses. She had tried to wear both soft and GP lenses and stated that the lenses either felt as though they were going to fall out or they made her eyes itchy and uncomfortable. Optimal vision was never achieved with previous lenses. She stated that she often wore no correction because her vision was adequate, although she frequently got headaches when she didn't wear her glasses.
A comprehensive examination revealed a spectacle prescription of +4.50 –6.50 × 175 OD with 20/20-2 vision and +5.00 –7.00 × 010 OS with 20/20-2 visual acuity. Keratometry readings were 40.50/47.00 @ 085 OD and 39.75/48.00 @ 100 OS with clear oval mires in each eye. Slit lamp examination was clear in each eye with no signs of Fleischer's ring or striae. The findings were consistent with high astigmatism with no suspicion of keratoconus.
Designing the Lenses
Although GP lenses were recommended, the patient also wanted to try soft lenses (Table 1). Due to the high degree of astigmatism, we ordered the GP lenses empirically with the steep meridian 0.75D flatter than the K reading.
At dispensing, the soft toric lenses resulted in visual acuity of 20/30 in each eye with unstable lens rotation. The GP lenses resulted in visual acuity of 20/20-2 OD and 20/25-1 OS. Light apical clearance with good edge clearance, movement, and centration was noted in each eye.
The patient returned after two weeks for follow up and reported improved lens comfort. She noted that the vision with the right lens was stable but that she needed to push the left lens occasionally to get it to stay in place. An over-refraction on the left lens of +0.50 –1.00 × 010 resulted in 20/20 visual acuity. When incorporated into the lens, the resultant design was a spherical power effect lens with better stability of vision.
Don't Be Daunted
For this case, a spherical power effect design was preferable due to the improved stability of vision. Cases such as this can appear daunting at first; however, with currently available contact lens technologies and fitting tools available through Web sites such as www.gpli.info and through lab consultants, we can design toric GP lenses with greater ease and success.
Fitting the child in this case with contact lenses will provide consistent optimal vision while decreasing the potential for meridional amblyopia. She wears her contact lenses all day, she now appreciates clear vision, and she no longer suffers from headaches. CLS
Dr. Rah is a staff optometrist at the Massachusetts Eye and Ear Infirmary Contact Lens Service where she specializes in medically necessary and other advanced contact lens designs. Dr. Walline is an assistant professor at The Ohio State University College of Optometry, where he conducts studies of pediatric contact lens wear. He is also a consultant or advisor and has received research funds from Paragon, and Vistakon.
Contact Lens Spectrum, Issue: October 2009