Welcome to the premier issue of OD News, an electronic newsletter from your friends at Pacific Cataract and Laser Institute. Our goal is to share clinical updates and pearls that can directly enhance your patient care. I encourage your feedback on format, topics, information and future ideas to keep this quarterly publication interesting, timely and valuable for your practice.

Enjoy!

Ben Stoebner, OD
Editor

Keratoconus and LASIK do not mix. But keratoconus presents a challenge because early diagnosis is difficult, progression is variable, and prognosis is unpredictable. PCLI has developed a tool we routinely use to assess referred patients.

As you know, keratoconus is a non-inflammatory, self-limiting ectasia of the axial portion of the cornea. It is characterized by progressive thinning and steepening of the central cornea. Vision in most cases can be corrected with glasses and contact lenses, and patients do fairly well.

To some degree, stability of the cornea and globe is related to corneal thickness. For this reason we do not want to thin the cornea too aggressively with LASIK. This is especially important in patients with suspected keratoconus.

Following is Pacific Cataract and Laser Institute’s method for identifying early keratoconics. We have coined it the PCLI Asymmetry Test—or PAT for short. Here’s how it works.

PCLI Asymmetry Test (PAT)

1. Using topography, measure the curvature of the cornea's steepest spot. This is normally the center but if there is a steeper eccentric spot, place the topographer cursor over it and measure it there.
2. Find the mirror image spot 180 degrees from the steep spot and the same distance from the center. Measure it the same way.
3. Mark both spots on the print out, write their curvature numbers, and determine the difference between the two.
   
   If the difference is:

• less than 2 diopters—cornea can be considered within normal limits.
• between 2 and 3 diopters—proceed with caution. Patient should be steered away from corneal surgery. However, if factors such as CL history, slit lamp findings, age, family history, refractive stability, and corneal thickness are positive, LASIK may be considered. A bed of 300u after the treatment may be preferred to the usual limit of 250u.
• more than 3 diopters—LASIK is contraindicated.

If you have any questions or would like to learn more about the fundamentals behind PAT, contact any one of our doctors.

High levels of antioxidants and zinc reduce the risk of advanced age-related macular degeneration (AMD) by about 25 percent. These same nutrients also reduce the risk of vision loss caused by advanced AMD by about 19 percent. And they have no significant effect on the development or progression of cataract.

These findings were obtained from the 5-year results of the Age-Related Eye Disease Study (AREDS). A total of 4757 men and women between ages 55 and 80 years were enrolled. Their macular status ranged from no evidence of AMD in either eye to relatively severe disease with vision loss in one eye and good vision (20/30 or better) in the fellow eye.

People who are at high risk or have advanced AMD should consider daily doses of the formulation used in the study:

• 500 mg vitamin C
• 400 IU of vitamin E
• 15 mg of beta-carotene
• 80 mg of zinc as zinc oxide
• 2 mg of copper as cupric oxide

Bausch and Lomb, a collaborator in the AREDS, provided the nutrients which are now marketed as Ocuvite PreserVision. Other companies produce similar formulas. Copper was added to the AREDS formulations containing zinc to prevent copper deficiency, which may be associated with high levels of zinc supplementation. Since antioxidant vitamins may be purchased separately, it is important to inform patients to include copper when ever taking high levels of zinc.

AREDS participants reported few side effects. About 7.5% of participants assigned to the zinc treatment suffered urinary tract problems that required hospitalization, compared to 5% of the non-zinc group. Participants in the two groups that took zinc also reported a higher rate of anemia. A well known side effect of beta-carotene—yellowing of the skin—was reported slightly more often by participants taking antioxidants. Of special importance, two large clinical studies sponsored by the National Cancer Institute have shown beta-carotene to significantly increase the risk of lung cancer among smokers. A responsible clinical recommendation is that smokers not take beta-carotene—or stop smoking.

Source: National Eye Institute www.nei.nih.gov

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