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The LASIK Directory Blog

Welcome to the LASIK Blog, a resource for people interested in LASIK surgery. This consumer-friendly blog is intended to be used as a central resource to answer common questions about LASIK and to point you in the right direction.

Monday, January 31, 2011

Anti-VEGF Agents and IOP Spikes

Anti-VEGF injection is being investigated for treatment of the vascular or wet form of age-related macular degeneration (AMD). This is not an FDA-approved use for these medications, but it is becoming a popular off-label use. Wet AMD has no other good treatments and can quickly lead to serious vision loss, so any treatment that can reverse vision loss and preserve these gains can be expected to increase in popularity. However, researchers have discovered one major roadblock to this treatment avenue.

Following injections of anti-VEGF medications, patients have been experiencing spikes in intra-ocular pressure (IOP). Increased IOP can lead to optic nerve damage, and is the primary characteristic of most forms of glaucoma. Over time, elevated IOP can lead to vision loss. Short-term IOP spikes are a common side effect of all forms of eye injections, but the IOP spikes seen in anti-VEGF treatments seems to be long-term. Research suggests is may be related to a clogging of the open angle. One possible explanation is that the anit-VEGF drugs (primarily Avastin (bevacizumab) and Lucentis (ranibizumab)) may have been mishandled prior to injection and therefore contain a large number of silicone oil droplets. At least one study has shown that freezing the anti-VEGF drugs can cause silicone oil to leach the vials into the drug itself. When this occurs it causes a significant increase in the number of particles in the drug. Once inside the eye, the natural flow of fluids will draw them into the open angle, clogging it and causing secondary glaucoma.

If you are over the age of 45 and notice any changes in your vision, it is important to talk to an eye doctor to learn whether AMD may be responsible, and whether treatments are available for your form of the disease. Contact us today to find a local ophthalmologist.

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Monday, January 24, 2011

New Technique for Improving Cataract Surgery in Post-LASIK Patients

LASIK is a very successful vision treatment, but it cannot stop the aging of the eye's lens, which leads first to presbyopia and then to cataracts. Unfortunately, the changes LASIK makes in the cornea can make it more difficult to select an appropriate replacement lens during cataract surgery. Now, as the first generation of LASIK patients is reaching the age when cataract surgery becomes necessary, doctors are facing the challenge of trying to find an appropriate lens that will match the cornea to create a single effective visual system. Some researchers believe they have found the answer.

Results presented at the Hawaiian Eye conference show that intraoperative wavefront aberrometry might be an effective technique for improving the outcome of cataract surgery in LASIK patients. In the past, the challenge of calculating the appropriate intraocular lens to use in cataract surgery for prior LASIK patients involved some amount of guesswork. The new technique allows surgeons to measure the true refractive profile of the cornea during surgery to make precise decisions about the best intraocular lens to use. According to this very preliminary work, the new technique can significantly improve the accuracy of lens selection by as much as 0.5 diopters, which is the equivalent of one line on the Snellen eye chart.

If you have had LASIK surgery and are now beginning to experience the impact of aging eyes, such as presbyopia and cataracts, you need to talk to an ophthalmologist about the best treatment options for you. Please contact an ophthalmologist today.

Monday, January 17, 2011

Carbohydrate Consumption and Cataract Risk

We have long heard that a diet high in carbohydrates may be associated with a number of serious health conditions. Now research adds cataracts to that already-long list. Although the possible connection between carbohydrates and cataracts has been public knowledge for about five years, the weight of evidence has been split on the significance of the association.

In 2005, the US Department of Agriculture first put out its warning that a diet rich in carbohydrates could as much as double a woman's risk of developing cataracts. The USDA based its warning on a small study that looked at cataract diagnosis and carbohydrate consumption in 417 women aged 53 to 73. The study found that women who consumed a diet rich in carbohydrates (200-268 grams per day) were more than twice as likely to develop cataracts those who consumed a diet lower in carbohydrates (101-185 grams per day).

However, another study, published earlier the same year, looked at approximately 72,000 women and 40,000 men, showed did not seem to be a link between glycemic load and cataract risk.. study participants were followed for about 14 years (women) and 12 years (men). The study looked at subjects' dietary glycemic load, the elevated glucose levels in a person's blood that occurs primarily as a result of refined carbohydrate consumption. The study administrators adjusted for age, smoking, body mass index, and other factors before seeming to exclude a glycemic load/cataract risk tie. This study has been criticized as having excluded too many factors (including total calorie consumption and other dietary factors) and therefore conflated its results.

Since 2005, two other studies have added support to a connection between high levels of carbohydrate consumption and increased cataract risk. A 2006 study looked at the diets of 3377 participants aged 60-80 and sought a connection with cataract risk. The study analyzed glycemic loads of the participants and gauged this against cataract diagnosis. It found that those in the highest quartile of glycemic load were 1.29-1.43 times more likely to be diagnosed with two types of cataracts compared to those in the lowest quartile. A more recent study, following up on the results of the 2006 study, looked at the diet and cataract risks of 1609 subjects. The results seemed to indicate that one type of cataract was 3.19 times more likely in the highest quartile of carbohydrate consumption than in the lowest. Unfortunately, as with previous studies, there is a possibility that missing data on confounding factors could be obscuring the existence or nonexistence of a connection.

There are many reasons to consider shifting to a diet lower in carbohydrates. To learn whether cataracts are one of them, please contact a local ophthalmologist today.

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Monday, January 10, 2011

Are Phakic IOLs Better than LASIK?

Although LASIK is the most popular refractive surgery, far more popular than the use of phakic IOLs, sometimes described as implantable contact lenses, there are some questions about whether it is the best refractive surgery for many different kinds of visual problems, including high myopia. Obviously, phakic IOLs offer many of the same benefits as LASIK: long-term vision correction, the freedom to see without using glasses or contacts, and the potential for even better vision correction than offered by traditional methods. Therefore, phakic IOLs are a natural competitor to LASIK surgery. But which one gives the best results?

Over the last few years, a number of studies have suggested that the crown for best results may go to phakic IOLs. At least two published studies and a conference lecture in the last few years suggest that phakic IOLs may give slightly better visual quality. One 2009 study looked at 46 eyes receiving STAAR's Implantable Collamer Lens (ICL) and 47 eyes that underwent custom LASIK for high myopia (<= -6 diopters), comparing pre-surgical and post-surgical higher-order-aberrations and contrast sensitivity. The study showed that phakic IOLs produced significantly fewer higher-order aberrations, and improved contrast sensitivity, whereas LASIK actually reduced contrast sensitivity. Another 2009 study looking at 45 patients (20 with two different phakic IOLs and 25 with LASIK) showed that one month after surgery, phakic IOL patients had recovered much more of their visual acuity than LASIK patients.

Additional support was given to phakic IOLs by a lecture given by Dr. Pablo Artal of the Optical Laboratory of the University of Murcia in Spain. Though his research was only suggestive and had not been formulated for publication, it suggested that LASIK may increase spherical aberrations as the degree of myopia increased, while phakic IOLs maintain or reduce spherical aberrations as myopia increases. However, the actual difference in visual outcomes was not as great as would be predicted by the measured refractive errors.

If you are looking for a long-term vision correction option for high myopia, you should talk to a local ophthalmologist today to learn more about your options and which one might be right for you.

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Monday, January 03, 2011

YAG Laser Treatment Does Not Prevent Pigmentary Glaucoma

Pigmentary glaucoma is an unusual form of the disease caused by blockage in the drainage canals. Unlike primary open angle glaucoma, in which years of normal sediment accumulates in the drainage canals, the debris clogging the angle is actually pigment granules from the iris. In some people, exercise, trauma, or other events cause the granules to flake off and become suspended in the aqueous humor. Once suspended, the eye's natural current takes them to the drainage angle, where they become caught and eventually prevent drainage. With drainage decreased, pressure builds up in the eye, leading to optic nerve damage and vision loss.

One proposed treatment for pigmentary glaucoma is ND:YAG laser peripheral iridotomy, a treatment for narrow angle glaucoma that actually blasts a hole in the iris to increase drainage. A study published in the journal ophthalmology, however, seems to cast doubt on the effectiveness of this treatment method. 116 patients with pigment dispersion syndrome and elevated intraocular pressure were assigned to either laser treatment or a control group to see if fewer developed pigmentary glaucoma with laser treatment than without. Unfortunately, the study showed that there was no difference between the time to development of pigmentary glaucoma in the two groups, nor did the laser group show a reduced incidence of pigmentary glaucoma.

Although ND:YAG laser peripheral iridotomy did not function as a good preventative treatment for pigmentary glaucoma, there are fortunately several other treatment options available. To learn more about pigmentary glaucoma and its treatment, contact a local ophthalmologist today.

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