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A Guide to Suitability for Laser Eye Surgery – Part 2

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07
Jul
2017

Part 2 – Your age, gender, personality and prescription

In the first part of this guide (which you can find here), we looked at what your suitability for laser eye surgery, what prescription numbers mean, possible treatment options, specific medical health issues, previous eye problems and also certain medications that are known to be either a relative or complete block on having laser vision correction.

Consultation to review suitability for laser eye surgeryIn this second part, we look at some common factors, such as age, gender and dry eyes, that play a role in your suitability for having laser eye surgery or other refractive correction, and which type of surgery may be most relevant.

This information should be used together with a full consultation at a laser eye clinic, where your clinician will provide specific advice as to whether you are suitable for treatment. There are additional factors to those listed here and all these will need to be considered in the final decision regarding suitability for vision correction.

Your laser eye specialist may need to refer you to another doctor to gain additional information or tests before deciding if you are suitable for treatment.

“Successful laser eye surgery depends on being a good candidate”

Types of laser eye surgery

Laser in-situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) are the most common methods of excimer laser refractive surgery.

LASIK is the most frequently performed option, typically 90% of all laser patients undergo this technique. It is highly effective for short-sight (myopia) and astigmatism, and can be very beneficial for milder degrees of long-sight and also for many patients who just require reading glasses.

Who is the ideal candidate for laser eye surgery?

We have been steadily increasing our knowledge about the characteristics of the ideal laser refractive surgery candidate since the first procedure was performed in 1988. We now have an extensive understanding of who is most suitable to undergo the procedure and, more importantly, who should be declined for treatment.

Understanding the ideal candidate characteristics can help patients to understand if treatment is an option for them and, if so, which procedure is most suitable.

Factors that can affect suitability for laser eye surgery          

  1. Age
  2. Gender and dry eyes
  3. Type of glasses needed (refractive error)
  4. Patient’s personality
  5. Tobacco use

“Laser eye surgery patients are in overall good health and free of eye disease.”

 1.  Age

The ideal laser patient is over 18 years of age since the refractive error is more likely to be changing below this age. Some patients over the age of 21 are still experiencing an increase in their prescription making them unsuitable for LASIK or PRK.

However, it seems that the average age of candidates is increasing, and during recent years the mean age of subjects receiving surgery has shown an upward trend. This is likely due to how we use our eyes in the computer era, with increasing screen usage and less time outdoors. Both factors have been shown to be linked to a progression in short-sightedness.

“The age of the patient is often linked to the type of treatment procedure that they will require.”

Younger patients, in their 20s and 30s, are generally looking to correct short-sight, with or without some degree of astigmatism. The usual choice of procedure is LASIK, with a minority of patients having PRK.

Middle-aged patients in their 40s and 50s most often request treatment to assist with a loss of near vision. This is known as presbyopia and requires the use of reading glasses. This is often treated using laser blended vision, though patients in their 50s are also candidates for refractive lens exchange (RLE).

Patients aged 60 and over most commonly will require a refractive lens exchange (RLE), using a premium lens to correct both far and near vision. Cataracts (a whitening of the lens causing a drop in vision) become increasingly common after the age of 60. The surgery to remove them is identical to RLE.

Age Group Comment Procedure 1 Procedure 2
18-21 Prescription may not yet be stable LASIK PRK
22-40 Short-sight and astigmatism LASIK PRK
41-49 Developing presbyopia LASIK for distance vision LASIK Blended Vision
50-64 Established need for reading glasses LASIK Blended Vision Refractive Lens Exchange (RLE)
65+ Cataracts increasingly common Refractive Lens Exchange (RLE) Cataract surgery
Table 1: Primary and secondary laser eye surgery and lens replacement options for various age groups

 

Is there an upper age limit for laser eye surgery?

Man squinting assess suitability laser eye surgeryThere is no official upper limit for laser eye treatment. However, cataracts become increasingly common after the age of 60 and the natural optics of the ageing lens inside tend to degrade over this age. A lens exchange procedure becomes the preferred choice for most patients in this age group.

Is there a lower age limit for laser eye surgery?

The lower limit for treatment is 18. However, most patients with short-sight (the typical prescription in this age group) have not yet reached stability and their myopia is often still progressing. In practice, most patients are age 21 and over at the time of treatment.

Stability of your prescription

A patient’s prescription should not have changed for one year prior to treatment. It can sometimes be difficult to definitively ascertain that this is indeed the case, as the patient may not have visited for an eye examination for some time.

Myopia typically progresses for 10-15 years from the age of onset and asking about the age of onset can be useful. Additionally, most patients have stabilised by their mid to late 20s.

2. Gender and dry eyes

Overall the number of men and women seeking vision correction is the same, with a consistent 50:50 split.

Man with eye dropsBoth sexes show reluctance to wear glasses in certain situations. A recent poll showed that just over half of people took their glasses off when on a date or taking a selfie.

The main effect of gender is in the incidence of dry eye problems which are more common in women.

A US study showed that dry eye disease (DED) affected 1 in 7 adults aged 48 or older, with approximately 50% more cases in women than men. Dry eye disease also affects postmenopausal women, those taking HRT or using the contraceptive pill.

Reliable epidemiological data from the large Women’s Health Study and Physician’s Health Study indicate the prevalence of dry eye leading to symptoms in the United States is about 7% for women and 4% for men over the age of 50, which equates to around 3.2 million women and 1.05 million men with DED in the United States.

Dry eye disease is a growing problem. Twenty-five percent of patients who visit eye clinics report symptoms of dryness affecting their eyes, making it an increasing public health issue and one of the most common conditions seen by eye care clinicians. (Dry eye: diagnosis and current treatment strategies. O’Brien PD, Collum LM  Curr Allergy Asthma Rep. 2004 Jul; 4(4):314-9.)

3. Type of the refractive error

One of the most important eligibility criteria for refractive surgery is having a stable refraction, which means that the prescription for glasses or contact lenses has stayed the same.

This usually occurs after the age of 18 to 22 years for short-sighted patients, with or without astigmatism. Patients are often asked to produce past refraction details from their optician visits, for up to the previous 3 years, to show that they have some level of stability.

A patient with a large recent change in refraction will be advised to wait until two consecutive prescriptions are similar. The goal is to avoid patients undergoing refractive surgery and then find that a year later their prescriptions naturally became worse, leaving them once again with some degree of blur.

Laser eye surgery for short-sight and astigmatism is typically very stable post-operatively and should last many years. However, if the eyes condition worsens and myopia progresses, it may incorrectly appear that the treatment has worn off.

Laser refractive surgery changes the curvature of the cornea and can correct most cases of myopia (short-sight), hyperopia (long-sight) and astigmatism. It can also correct the need for reading glasses for patients affected by presbyopia (the need for reading glasses in middle age).

Myopia is corrected by making the cornea flatter, while hyperopia is corrected by making the cornea more curved. In the case of astigmatism, the cornea is made more spherical in shape.

The amount of refractive error with good outcomes has different ranges depending on the type of prescription and the excimer laser used. The table below shows the treatment range possible using the WaveLight Allegretto excimer platform:

Table to show whether your prescription is suitable for laser eye surgery

Table 2 – Prescription ranges for laser eye surgery

Original Eye test by Ferdinand MonoyerShort-sight treatment range

Short-sight between -0.25D to –14.00D is technically possible with the WaveLight platform, while other lasers have a lower range of correction. The limiting factor for extreme prescriptions is the thickness of the cornea, which will be measured at your consultation.

With the WaveLight system, which removes a smaller amount of tissue that some other lasers, most prescriptions up to -9.00 dioptres of myopia are treatable. Higher degrees of short-sight require a thicker than average cornea.

Astigmatism treatment range

Astigmatism can be corrected up to a severity of 6.00 dioptres. In the general population, 95% of astigmatism prescriptions are up to 2.00 dioptres, and most people have some degree of this refractive error, even if only minor, perhaps 0.25 or 0.50 dioptres. It is less common to have no astigmatism whatsoever.

Long-sight treatment range

Although newer models of excimer laser platforms allow for larger ablation diameters, the predictability and stability of hyperopic refractive surgery continue to be lower compared with myopic corrections, especially at higher degrees of hyperopia.

Other potential challenges of hyperopic refractive surgery include slower healing until the prescription is fully stable, fewer patients seeing 20/20 compared to short-sighted corrections, and higher rates of retreatment.

The combination of these factors can reduce surgeons’ willingness to perform hyperopic refractive surgery, and most clinicians will not treat greater than +4.00 dioptres, even if the laser (as in the case of the WaveLight Allegretto) is approved up to +6.00.

If the patient is greater than 50 years of age, refractive lens exchange (RLE) may be a better option.

4. Personality

Motivation for treatment should be assessed carefully preoperatively, and patients should not feel coerced into proceeding. Patients should have a cooling off period between their consultation and treatment.

Expectations should be realistic, particularly when the prescription is very high or when treating long-sightedness. Both these conditions may take longer to settle down than typical short-sighted corrections.

If the only acceptable outcome from your treatment is perfect vision, then you should appreciate that no medical intervention can absolutely guarantee a perfect result. Laser vision correction produces a very high level of vision outcomes but cannot guarantee perfect vision for all patients. Perfectionists may not be good candidates for any form of laser eye treatment or lens-based surgery.

Patients with obsessive-compulsive traits or disorder may not be suitable for vision correction, as expectations can sometimes be unreasonably high.

Personality also plays a role in good aftercare. You will need to be of a mindset that understands the need for regular post-operative appointments and also be compliant in taking medications and eye drops when requested.

If you feel that you are not able to either attend regularly or use drops and tablets as instructed, you should not proceed with laser eye surgery.

5. Tobacco use

Man with cigarette dry eyes red eyes irritationCigarette smoking has been reported to be one of the factors in a multitude of clinical conditions that cause a dysfunctional tear film (the wet layer moistening the front of your eyes), resulting in dry eye. A recent study has shown significantly poorer tear film stability and increased evaporation of tears in smokers.

Your tears are made up of a triple layer sandwich. The innermost part is made from mucous, the ‘filling’ is the main watery layer (what we normally think of when we say ‘tears’), and the outermost layer is a thin oily lipid layer produced by oil glands within your eyelids.

The oily layers act as a type of cling film, helping to keep the water from evaporating too quickly. Your eyes are basically warm and, without the oil covering, tears would start to evaporate away in 2 or 3 seconds. With an effective oil layer in place, your tear film should be stable for 10 seconds or longer; that’s plenty of time to keep your eyes wet until the next blink comes along.

Smoking damages the ultra-thin fatty layer of the tear film, leading to excess evaporation. This can lead to many smokers having problems with dry eyes, including stinging or burning eyes and eye redness.

LASIK induces temporary dry eye for 3-6 months after treatment, and smoking can exacerbate symptomatic dry eye.

Because of the increased risks associated with smoking and LASIK, patients are advised to refrain from smoking for at least four to six weeks before surgery and then another four to six weeks after surgery. Read more on the effects of smoking on your eye health here.

Summary

In the first second part of this guide, we looked at specific health conditions that can be a complete or potential contraindication for having laser eye surgery. Some medical conditions mean that laser eye surgery is not an option for you, whereas others need some further consideration and test for you individually, and treatment may still be possible. Read more about these considerations here.

Now, we have also looked at some general considerations for your suitability for having refractive laser eye surgery, including age and which procedure might be most applicable. We have also reviewed some common issues, such as dry eyes, the type of glasses you wear and the implication for treatment, plus the effect of smoking on the health of your eyes. We always try to work with you, to ensure your treatment is done with great care. Want to learn more? Contact us today!

 

By: David

If you are interested in vision correction at Focus Clinic please call us on 0207 307 8250 and book a free consultation.

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 Samar Hamada