Screening for LASIK And Why You Cannot Trust A Scan


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One of the most disturbing aspects of Refractive Surgery is the complete lack of ability for a prospective patient to be correctly screened. Most people are under the illusion that clinics and surgeons are capable of completely and thoroughly screening patients for surgery and that the technology exists to perform these screenings.

What has become apparent, is that not only is the technology incapable of detection serious contraindications for surgery, but that surgeons themseleves are not capable of interpretting the results of their tests.

Have a look at the pre-operative scans below:

You might be thinking that the above scans show three different eyes, the first with serious problems, the second with moderate issues and a final normal eye.

In fact what you are seeing is the same eye being scanned on the same machine three times. Why do they look so different? This is simply down to the scales used on the topography.

And this is the issue, surgeons cannot agree on what would be classed as ‘normal’. Which means that the evaluation process is essentially useless.

A recent study on post-refractive patients who developed ectasia (a serious sight threatening ailment) demonstrates the dangers of poor refractive screening.

“This study assessed the variability of subjective as- sessment of corneal topographic pattern in 11 eyes that developed ectasia after LASIK and 14 eyes that under- went LASIK and were stable, as judged by experienced reviewers not informed of the patient outcomes during the review. The results demonstrate great variability of these subjective topographic classifi cations among and between examiners for both the normative 0.5 D and the American National Standards Institute standard absolute 1.5 D color scales.

The significant variability in grading of corneal topography patterns by experienced topography readers reported herein highlights the challenge that faces re-fractive surgeons who are evaluating patients as candidates for LASIK. Although it is often easy in retrospect to find suspicious characteristics in topography maps in the eyes of patients who have developed post-LASIK ectasia, this study demonstrates why there is still some latitude in absolute determination for surgical candidacy. It is clear that not all examiners are using the same strategy for pattern evaluation, and further work on reducing the subjective variability of interpretation of corneal maps could potentially help refractive surgeons improve their ability to accurately interpret corneal topography maps.

Further, the variability reported emphasizes the utility in considering a multitude of other screening parameters beyond simply the topographic pattern, whether or not it be through the use of specific screening systems such as the ERSS. There was significant variability on the subjective topographic classifications among different examiners using the same scale. The variation in score from 0 to 4 occurred in 68% (17 of 25) of eyes with the absolute scale and in 44% (11 of 25) of the cases with the normative scale along with little agreement among the examiners, demonstrating the great variability of subjective classification of the topography.”

When is Refractive sugery not for you?

You are probably NOT a good candidate for refractive surgery if:

  • You are not a risk taker. Certain complications are unavoidable in a percentage of patients, and there are no long-term data available for current procedures.
  • It will jeopardize your career. Some jobs prohibit certain refractive procedures. Be sure to check with your employer/professional society/military service before undergoing any procedure.
  • Cost is an issue. Most medical insurance will not pay for refractive surgery. Although the cost is coming down, it is still significant.
  • You required a change in your contact lens or glasses prescription in the past year. This is called refractive instability. Patients who are:
  • In their early 20s or younger, 
  • Whose hormones are fluctuating due to disease such as diabetes,
  • Who are pregnant or breastfeeding, or 
  • Who are taking medications that may cause fluctuations in vision, 

– are more likely to have refractive instability and should discuss the possible additional risks with their doctor.

  • You have a disease or are on medications that may affect wound healing. Certain conditions, such as autoimmune diseases (e.g., lupus, rheumatoid arthritis), immunodeficiency states (e.g., HIV) and diabetes, and some medications (e.g., retinoic acid and steroids) may prevent proper healing after a refractive procedure.
  • You actively participate in contact sports. You participate in boxing, wrestling, martial arts or other activities in which blows to the face and eyes are a normal occurrence.
  • You are not an adult.  Currently, no lasers are approved for LASIK on persons under the age of 18.

Precautions
The safety and effectiveness of refractive procedures has not been determined in patients with some diseases. Discuss with your doctor if you have a history of any of the following:

  • Herpes simplex or Herpes zoster (shingles) involving the eye area.
  • Glaucoma, glaucoma suspect, or ocular hypertension.
  • Eye diseases, such as uveitis/iritis (inflammations of the eye)
  • Eye injuries or previous eye surgeries.
  • Keratoconus

Other Risk Factors
Your doctor should screen you for the following conditions or indicators of risk:

  • Blepharitis. Inflammation of the eyelids with crusting of the eyelashes, that may increase the risk of infection or inflammation of the cornea after LASIK.
     
  • Large pupils. Make sure this evaluation is done in a dark room. Although anyone may have large pupils, younger patients and patients on certain medications may be particularly prone to having large pupils under dim lighting conditions. This can cause symptoms such as glare, halos, starbursts, and ghost images (double vision) after surgery. In some patients these symptoms may be debilitating. For example, a patient may no longer be able to drive a car at night or in certain weather conditions, such as fog.
  • Thin Corneas. The cornea is the thin clear covering of the eye that is over the iris, the colored part of the eye. Most refractive procedures change the eye’s focusing power by reshaping the cornea (for example, by removing tissue).  Performing a refractive procedure on a cornea that is too thin may result in blinding complications.
  • Previous refractive surgery (e.g., RK, PRK, LASIK).  Additional refractive surgery may not be recommended.  The decision to have additional refractive surgery must be made in consultation with your doctor after careful consideration of your unique situation.
  • Dry Eyes. LASIK surgery tends to aggravate this condition.