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Addressing patients with low myopia, low cylinder
Over the years, one of the most frustrating soft contact lens patients I’ve had to deal with is the low myope with low astigmatism. I would classify these patients as “not quite” patients. Everything you seem to do optically is good, but not quite good enough.
A spherical soft lens ends up fitting perfectly, but the vision is not quite good enough. An aspheric lens sometimes offers better vision, but often there is not quite enough improvement. Toric lenses are tricky for these patients. Because the total amount of prescription is low, a rotating toric can wreak havoc on the vision. A rotated 0.75 cylinder on a 5-D myopic eye has a much smaller impact on vision than on a 0.50-D myopic eye.
Where do we go with these patients? Here is an interesting case example of one of these “not quite” patients.
Case report: “not quite” patient
A 23-year-old woman desired soft lenses. She had no history of medications. Her spectacle prescription in the right eye was –0.75 –0.75 x 105 20/20. In the left eye, her prescription was –0.50 –0.75 x 080 20/20. She was fitted in the past with a plethora of soft lenses including Focus Toric (CIBA Vision, Duluth, Ga.), Extreme H2O (Benz Research, Sarasota, Fla.) and SofLens 66 toric (Bausch & Lomb, Rochester, N.Y.).
As you may notice, she has been fitted with either spherical lenses or torics with low cylinders. The classic problem was comfort and vision. The spherical lenses were comfortable, but offered not quite good enough vision. Toric lenses offered good vision, but were not comfortable. She complained of night driving and glare problems with sphericals. She also felt the edges and discomfort with torics.
Another reason for failure was contact lens-related dryness. She had no dryness symptoms without lenses. She had bulbar conjunctival staining in both eyes. Her tear break-up time was measured with the Dry Eye Test (DET) by Akorn (Buffalo Grove, Ill.): it was 16 seconds in the right eye and 8 seconds in the left eye.
Building tear film stability
We decided to attack this patient’s conditions from the ground up. First, we will build up her tear film stability to give her a strong foundation for the lenses to sit on. Afterwards, we will address her lens problems.
Usually, the first step I prefer for an unstable tear film is an anti-allergy drop. For this patient, Alcon’s Patanol (olopatadine HCl ophthalmic solution 0.1%) was prescribed twice daily for the first week. When the patient returned in 1 week, the tear break-up time in the right eye was 4.6 seconds. In the left eye, it was 12.6 seconds. One may note that the tear break-up time increased in one eye and was reduced in the other eye compared to the prior week. These results demonstrate the inherent variability of tear break-up time.
For the second week, we added another anti-allergy medication, Allergan’s Alocril (nedocromil sodium ophthalmic solution 2%), twice daily. At the 2-week visit, her tear break-up time in both eyes was more than 25 seconds. Slit-lamp evaluation revealed a reduction of staining, right eye trace bulbar stain and left eye light bulbar stain.
Because of the increased tear film stability, we decided to proceed with fitting her with contact lenses. The medication regimen was modified to one drop of Patanol per eye in the morning prior to application of lenses, one drop of Alocril per eye with the lenses 4 hours after insertion and one drop per eye with lenses 8 hours after insertion. One drop of Patanol was instilled per eye in the evening after the lenses were removed.
Instilling Alocril while the contact lenses are in the eye is an off-label use. Studies have shown that there is minimal adsorption of the active ingredient cromolyn into soft lens matrices. The active ingredient in Alocril, nedocromil sodium, is a derivative of cromolyn.
Choosing a lens
For a soft lens choice, the rationale was to choose a soft toric lens. The patient’s history indicated that spherical lenses were not successful. We decided to use a newer toric design, the Biomedics Toric from Ocular Sciences (San Francisco). The Biomedics Toric underwent extensive design studies to result in the most comfortable edges. We felt that a fortified tear film with an optimized edge design would give us the best chance of success with this patient. We also recommended that the patient use AMO’s Complete contact lens solution to increase comfort.
We tapered the use of the anti-allergy drops to Alocril twice daily. The patient was ecstatic and had excellent vision and comfort with her new lenses.
The author would like to thank Steve Brynes for his valuable help.
For Your Information:
- Milton M. Hom, OD, FAAO, practices in Azusa, Calif., and is a member of the Primary Care Optometry News Editorial Board. He can be reached at 1131 E. Alosta, Azusa, CA 91702; (626) 963-7100; fax: (626) 335-1402; e-mail: eyemage@mminternet.com. Dr. Hom has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.