Radial Keratotomy was a refractive procedure developed in the Soviet Union and involved making radial incisions in the cornea. This flattened the tissue reducing the amount of nearsightedness. Most of these patient’s corneas changed over time resulting in either regression to nearsightedness again or the more common ending, farsightedness with astigmatism. These latter patients usually have “softer” corneas and frequently have irregular refractions and are not always correctable to 20/20.

The big question that then asked is, ” what procedure can I have to correct my vision now”? These has been considerable discussion as to weather PRK or LASIK is better for these patients. As usual, there are always as many answers and opinions. Many refractive surgeons prefer doing LASIK after RK for 2 reasons. The first is that there is a reduced incidence of post operative corneal haze as opposed to PRK. The second is that it still leaves PRK as a third procedure should one be required to finalize the refractice corneal power.

Studies performed by the FDA during the 1990s demonstrated that in addition to the increased likelihood of the post operative haze with PRK there was also a tendency to heal unpredictably. With the introduction of Mitomycin to be used after PRK, there was a substantially lower incidence of corneal haze. This was a huge step forward in improving the results and an increase in PRK procedures. One consideration though is the long term side effects of Mitomycin use. These are still unknown and only time will give us the answer. Furthermore, there is an increased incidence of corneal haze with each PRK performed. Thus a surgeon must factor this into his/her equation when deciding what procedure to perform. If an enhancement must be done years after the initial one, PRK may not be available if corneal haze may be the result. In addition, the increased risk of hyperopic shift after RK always lurks in the shadows. As a result, a number of refractive surgeons prefer doing LASIK as the first procedure after RK leaving PRK as a back up should it be needed.

While there is no data linking increased cataract development in post refractive surgery patients, many will get them as they age. These surgically altered corneas will make implant calculations much more difficult. In addition, will there be secondary problems with the inner most layer of the cornea, the endothelial cell layer, affecting the cataract procedure.

Another consideration when choosing LASIK over PRK after RK is the risk of intrastromal bubbles escaping through the RK incisions and getting trapped between the epithelium and the focusing lens. This in turn blocks the laser and the flap can not be made. The procedure would have to be stopped and reperformed in 6 months using a microtome instead of intralase.

In summary, choosing either PRK or LASIK after RK depends on a host of factors and making the wrong choice can have very detrimental affects. As always only an experienced refractive surgeon should be called upon when enhancing an RK altered eye.

Comments(2)

Known as the great imitator, Syphilis has been all but eradicated in the US, but is still a prevalent problem in third world and developing countries. It is caused by the spirochete Treponema palidum. It still remains a global problem and can easily be transmitted to the US via any individual that has exposure to individuals from other lands. 12 million new cases were diagnosed in 1999 alone! Two thirds of the acquired cases occurred in male homosexual relationships; which was also related to HIV infections in the same people.

Syphilis is a systemic disease that affects the eyes. It can be acquired transplacentally in utero or via sexual encounters after birth. Congenital syphilis can present in childhood with Hutchinson’s Teeth, saddle nose deformity, and deafness. Ocular complications are often interstitial keratitis, and a displaced natural lens ( ectopia lentis).

Acquired syphilis is broken down into 4 stages. The first is the development of a painless chancre which appears 2-6 weeks after exposure to the spirochetes usually at the site of introduction. Secondary syphilis occurs 4-10 weeks after exposure and presents as fever, malaise and a generalized rash on the palms or soles. The third stage called latent, is undetectable may last for many years. The final stage, called tertiary, is characterized by neurologic and cardiovascular changes and occurs many years after exposure. Morbidity and death are complications at this stage.

The ocular manifestations involve most structures. Conjunctivitis, episcleritis, scleritis, interstitial keratitis, conjunctival injection, and terrier chamber inflammation, natural lens dislocation, uveitis, glaucomatous precipitates, iris nodules and dilated iris blood vessels known as roseola are very common in tertiary syphilis. In addition, elevated intraocular pressure is very common and is called Inflammatory Ocular Hypertension Syndrome. In addition, the back of the eye can become involved in the form of chorioretinitis, retinitis, vasculitis, vitritis, and panuveitis.

Diagnosis of ocular syphilis relies largely on serologic testing. There are two types of antibody based serum tests called non-treponemal and treponemal.

The treatment of choice is penicillin for all stages of the disease. IV penicillin G 18-24 million units daily for 2 weeks followed by intramuscular procaine penicillin 2.4 million units for 3 weeks. If the patient is allergic to penicillin then alternative antibiotics must be used such as tetracycline, doxycycline, chloramphenicol, ceftriaxone and the macrolide family of medications. The long term complications of untreated syphilis include glaucoma, uveitis, cataracts, epiretinal membranes and macular edema.

The best way to avoid all these extremely unpleasant complications is to seek immediate medical care at the first sign of any disease. In this case the chancre is an unmistakable sign and should never be ignored. The fact that is goes away should not be construed as a green light to good health.

Comments(0)

Macular Degeneration is a progressive disorder that damages the central most part of the retina called the Macula. This area of the eye has the highest concentration of neuroreceptors and thus the most acute vision. Any alteration in this section of the retina will result in decreased vision.

A recent study published in The Archives of Internal Medicine on Feb 23 2009, indicated that the use of Vitamin B supplements can reduce both the onset and severity of this debilitating condition. The study was conducted on female health care professionals with a history of cardiovascular disease, or who were at risk of developing it. 5205 women were followed for an average of 7.3 years. Those taking the Vitamin B were found to have a 41% reduced risk of significant degeneration as compared to those who were given placebos during the same time period.

The test group took a combination of Vitamin B6, B12 and folic acid. Dr Wm Christen , the study’s lead author, believes the positive effects were do to the Vitamin’s ability to reduce the blood levels of the amino acid homocysteine which have been implicated in vision loss resulting from macular degeneration. Further studies need to be performed before vitamin therapy becomes an accepted treatment modality, but it does show promise in reducing the cases and severity of this condition.

Comments(1)

Glaucoma is an eye disease that results in loss of vision and total blindness if untreated. It is caused by an increased pressure inside the eye that gradually decreases blood flow to the optic nerve. In doing so, the optic nerve dies. Many systemic disorders increase the likelihood of contracting glaucoma, but there is usually a positive family history in many of these patients. The question that needs to be asked is, “are there procedures or factors that will increase the chances of getting glaucoma?”

The answer to this inquiry is maybe. LASIK is a surgical procedure that alters the shape of the cornea in order to reduce or eliminate its’ refractive power and thereby decrease a persons’ need for eye glasses. In doing so the cornea is made thinner because of the lasers’ ablation of the central corneal tissue. This decrease in corneal thickness also results in a more flexible or softer cornea.

Measuring intraocular pressure is best done by the use of a procedure called Goldmann applanation. It involves a tono tip that is gently applied to the anterior corneal surface creating mires or semi circles that ” read” the internal ocular pressure. A thick cornea will “push” back on the applanator resulting in a higher reading while a thinner cornea will give more ground thus resulting is a lower reading. Therefore, corneal thickness directly influences the results on this extremely important test.

Post LASIK patients, because of thinner corneas, will usually have what appear to be lower intraocular pressures. In patients with a predisposition toward contracting glaucoma this factor further complicates a usually difficult situation. Central Corneal Thickness ( CCT) measurements are done routinely and average corneas should be at least 500 microns thick. Post LASIK patients will be much thinner depending on how much cornea had to be ablated. The problem arises when trying to accurately measure the pressures. If one of these post surgical patients is a glaucoma suspect then attempting to determine an accurate IOP will be very difficult. Therefore, while LASIK does not increase the chances of contracting glaucoma, it does make diagnosing and treating much more complex.

The most important point to remember from this is that if an individual has a family predisposition for glaucoma, LASIK may not be a good procedure to have since it may result in a more difficult and complex situation later on when dealing with a dangerous condition.

Comments(1)