Refractive Surgery Blog

Now that laser surgery for vision correction has been around for over a decade, patients who previously were hesitant to consider lasik have accepted the procedure to be safe and effective and are being evaluated in ophthalmologist's offices with increasing frequency. Fortunately, the technology we now have for this screening process has improved to the level that we are able to determine good candidates from bad ones almost all of the time. The interesting thing is this; we are finding that the number of patients with underlying corneal abnormalities (and thus not lasik candidates) is greater than we thought. Specifically, the condition known as keratoconus or corneal ectasia was previously thought to occur in 1/2,000 Americans but now reports are finding this condition to be occurring as commonly as 1/500 according the the National Eye Institute.

Keratoconus is a condition that usually begins to develop in the late teenage years and can progress until the age of about 40 when it slows down or stops. The condition occurs in both genders and all ethnicities but has a higher prevalence among females and in those with Asian heritage. The symptoms vary from those of just needing a glasses prescription to see more clearly to diminished vision and/or double or triple vision that is uncorrectable with glasses. The classic complaint of the keratoconus patient is seeing multiple ghost images out of the affected eye(s) or monocular polyplopia. There are many theories as to the cause of this conditions but its cause(s) still remains a mystery. Keratoconus is associated with certain allergic and arthritic disorders, Down's syndrome, chronic eye rubbing, corneal surgery and chronic contact lens wear. And, it has a recessive genetic component that can run in families.

While many keratoconus patients are unaware that they have an underlying corneal condition or dystrophy, others complain of severe visual difficulty. If patients with keratoconus cannot be corrected with glasses or soft contact lenses, there are now a number of innovative rigid lenses that can be used quite successfully to correct the myopia and astigmatism that is common in this corneal disorder.

In the most severe cases of corneal ectasia, surgical options can be used. Corneal transplantation has traditionally been the final answer for keratoconus patients. But now, other choices exist. Corneal ring inserts (Intacs or Ferrara rings) are being used more commonly today. They work by bolstering the thinned, bulging corneal tissue and tend to reduce the irregular corneal astigmatism that commonly occurs with keratoconus. While corneal ring inserts have not been widely used at this point in time, the results of using them have been encouraging. Another option that has shown promise is the use of riboflavin eye drops followed by exposure to UV-A light. This treatment increases the cross-linking of collogen in the cornea and improves its over-all strength. This option can be used in conjunction with corneal ring inserts or with conductive keratoplasty. Read more about CK.

Read more about General Eye Care.

Stuart Lewis, MD

Labels: Keratoconus

I receive questions regularly from patients and colleagues about the safety of Viagra, Levitra and Cialis usage. Specifically, many patients have heard about the possible effects on one's vision and want to know if there is any truth to the "rumor." The answer, in a word, is yes. I will try to outline some of the well documented information about these drugs.

Since receiving approval by the FDA in 1998, Viagra (Pfizer Labs) has been prescribed well over 23 million times in the United States alone. The way this drug works is by inhibiting an enzyme (phosphodiesterase 5 or PDE-5) and enhances the effects of nitric oxide in the body. Nitric oxide stimulates the smooth muscle which facilitates blood flow and causes the desired effects. However, this class of medications can also affect arteries elsewhere in the body and the results are unwanted side effects. In addition, Viagra-like drugs also inhibit the effect of PDE-6, a closely related enzyme to PDE-5. This enzyme is present in retinal photoreceptors and when blocked, causes light sensitivity (photophobia) and/or blue tinged vision.

Systemic side effects of this class of drugs include:

• Headache
• Facial flushing
• Nasal congestion
• Nausea
• Other gastrointestinal problems
• Pulmonary hypertension

These side effects are dose related and occur in 3% of men taking 25 -50 mg to 50% of men taking 200 mg and 100% of men taking 600 -800 mg.

A rarer and poorly understood eye disorder called nonarteritic anterior ischemic optic neuropathy (NAION) has been reported in several men and is presently being investigated. NAION is the most common acute optic nerve disease in adults over age 50 and shares a number of common risk factors with erectile dysfunction (ED): age over 50, high blood pressure, high cholesterol, and diabetes. "Most of the cases in which NAION has occurred in men taking Viagra have involved patients with underlying anatomic or vascular risk factors associated with the development of NAION" according to Pfizer. In other words, it is not clear that there is a cause and effect relationship between Viagra use and NAION.

The bottom line is that one should not take these medications unless they are needed as there are serious health and visual risks associated with them. Patients with the following conditions should check with their ophthalmologist prior to taking any ED drug:

• Retinitis pigmentosa
• Diabetes
• Retinal pathology - including macular degeneration and optic nerve disorders

Also, check with your primary care physician to rule out other serious medical conditions that could be problematic with the use of this class of drug.

Read more about General Eye Care.

Stuart Lewis

Labels: Medications