lasik for astigmatism melbourne

LASIK for Astigmatism – How Does The Treatment Work?

Many patients believe that they are unable to access laser eye surgery due to their prescriptions involving astigmatism. While this may have been true in the past, with advancements in our ability to make precise calculations during laser eye surgery to accurately correct astigmatism, LASIK for astigmatism is now in fact just one of several refractive surgical techniques used to give an astigmatic patient clear vision without depending on glasses or contact lenses.

 

What is Astigmatism?

Before delving into how LASIK eye surgery, or any laser eye surgery, can be used to correct astigmatism, it helps to first understand what astigmatism is.

Astigmatism is a type of refractive error, an imperfection of the eye’s focusing system which leads to blurry or uncomfortable vision. It may occur alongside either long sightedness (hyperopia) or short sightedness (myopia). Most cases of astigmatism arise due to an uneven curvature of the cornea, which is the transparent dome at the front surface of the eye. This results in light entering at different positions through the cornea being bent, or refracted, by different degrees. The outcome of this is that different rays of light come to focus at two distinct points on the retina at the back of the eye, which we then perceive as blurry or distorted vision. A less common source of astigmatism is the crystalline lens inside the eye, in a case known as lenticular astigmatism.

Many eyecare practitioners will use the analogy of an AFL football versus a soccer ball – on an AFL football, following one line along the ball from tip to tip results in a flatter curvature than if you were to trace along the perpendicular meridian, around the girth of the ball. Conversely, a soccer ball is perfectly round and you will find the same degree of curvature no matter which line you follow around the ball. When it comes to the cornea or lens, light is refracted more sharply when passing through the steeper curve, which results in these rays coming to a focus point earlier within the eye than rays that passed through the flatter line of curvature, which will focus to a point further in the eye.

Patients with uncorrected astigmatism may find they experience:

  • Glare sensitivity, such as seeing oncoming car headlights or streetlights as a “starburst”
  • Ghosting, which refers to the perception a faint double image where there is only one object
  • Headaches, often after prolonged reading or other near vision activities

Originally, the only way to correct astigmatism was through the use of spectacle lenses. Since then, contact lens technology has developed to be able to correct higher degrees of astigmatism, and now soft contact lenses can often cover prescriptions of up to almost -6.00 dioptres of astigmatism; custom-made hard contact lenses can often correct astigmatism even higher than this.

Patients with astigmatism can be assured that now LASIK eye surgery, other forms of laser eye surgery such as PRK, and refractive techniques that don’t involve a laser, such as refractive lens exchange, are considered safe and accurate methods of surgically correcting astigmatism.

 

How Does LASIK for Astigmatism Work? 

LASIK for astigmatism works much the same way as general LASIK eye surgery. Laser eye surgery procedures work on the premise of reshaping the cornea through the process of photoablation, the removal of select areas of corneal tissue in order to redirect the passage of light through this surface.

After topical anaesthetic is applied, a flap of superficial corneal tissue is first created using either a manual bladed instrument or a femtosecond laser tool, and then moved aside while still remaining attached to the eye. An excimer laser is then applied to the underlying corneal layers for the reshaping process, and the corneal flap then repositioned when the work is done.

In order to accurately correct refractive error with LASIK eye surgery, whether the script involves astigmatism or not, precise mathematical wavefront measurements are taken of the eye and then fed into a complex computer algorithm, along with other biometric data of your eye. This then guides the excimer laser during surgery to ensure the correct areas of the cornea are subject to photoablation of just the right amount to correct your prescription. As astigmatic scripts can be a complex combination of both corneal and lenticular sources of astigmatism, it is important to be able to achieve precise biometric measurements prior to going into surgery, something that was not always available. With advancements in the ability to make accurate wavefront calculations, LASIK for astigmatism of up to around 5 dioptres has become possible.

As with any laser eye surgery, general eligibility criteria do apply for people interested in LASIK eye surgery. As LASIK involves removal of corneal tissue, it is important to establish a minimum corneal thickness to ensure that a sufficient amount of tissue remains to maintain the mechanical stability and integrity of the eyeball. As higher prescriptions typically require a greater amount of photoablation, a patient with a script within the treatable range may find they are in fact unsuitable for LASIK due to insufficient corneal tissue available to address their script. Such people may be guided towards another refractive procedure, such as PRK, intraocular contact lens, or refractive lens exchange.

 

 

Note: Any surgical or invasive procedure carries risks. Before proceeding, you should seek a second opinion from an appropriately qualified health practitioner.

is laser eye surgery safe melbourne

Is Laser Eye Surgery Safe? – What You Need To Know

Glasses and contact lenses can be inconvenient – they fog up, fall off, slip down, need cleaning, need constant maintenance – for people highly dependent on optical correction, vision correction with laser eye surgery can be a tempting solution. But any sort of operation to the eye can be a daunting thought and before you go under the metaphorical knife, you really want to know is laser eye surgery safe and what are the risks?

 

Laser Eye Surgery

It helps to know what laser eye surgery actually is and how it achieves vision correction. Laser eye surgery refers to a group of refractive operations of varying techniques – surgical procedures designed to change the way light passes through the eye so that rays come to a clear focus on the retina to form sharp vision. Although not all refractive procedures actually involve a laser tool, those that do mostly concentrate on reshaping the front surface of the eye known as the cornea.

This reshaping process involves the removal of select areas of the cornea, literally changing its shape. The result is that light is bent along a different pathway as it passes through this tissue to come to a point at the back of the eye where we perceive vision as being clear, thereby providing vision correction without the need for external optical aids such as glasses or contacts.

As with any surgical procedure that involves an incision in the body, laser eye surgery does come with a degree of risk. Although certain techniques are associated with particular risks and complications that other methods may be able to ameliorate, surgical vision correction techniques are recommended to individuals on a case by case basis – which laser eye surgery method is safest for you and your eyes.

 

factors consider is laser eye surgery safe melbourneIs Laser Eye Surgery Safe?

Before any medical device or operation is approved for clinical application in Australia, it must first go through a strict process of approvals to ensure the safety of the public. Overall, laser eye surgery is considered to be a very safe procedure with a very low rate of complications; success rates are typically quoted around 98-99% in the developed world.

Complications from surgical vision correction resulting in a loss of more than one line on the visual acuity letter chart sit around 0.4% and more comfortingly, total loss of sight from laser surgery has never been reported in an Australian clinic. One of the most well-known, popular refractive techniques, LASIK is known to provide perfect 20/20 vision for over 90% of patients. Extensive studies into the safety of other refractive methods including PRK and SMILE® also tend to demonstrate that these techniques are comparable in safety and efficacy.

As mentioned earlier, when it comes to laser eye surgery each patient is assessed on a case by case basis by their ophthalmologist and clinical team. This determines the level of your risk of complication as well as guides your eye doctor in deciding which procedure is the best and safest for you. There are several factors your refractive specialist will take into consideration:

  • Your prescription – Each laser vision correction method will have been assessed for effectiveness and safety within a certain prescription range. Although this parameter is not considered in isolation, there are general rules of thumb when it comes to the treatable prescription range for each refractive technique, whether it’s astigmatism, or short- or far-sightedness. For example, LASIK and SMILE® can often be used to treat degrees of short-sightedness even into the double digits.
  • Your corneal thickness – Refractive techniques that require reshaping of the cornea rely on a minimum corneal thickness. As the reshaping process involves removal of tissue and the higher the script, the more tissue that needs to be removed, an adequate amount of tissue is needed to begin with in order to address the presenting prescription. In addition to this, there is a minimum residual corneal thickness that needs to remain after the reshaping process to maintain the mechanical integrity and stability of the eye. Compared to LASIK, PRK tends to be a safer option for patients with thinner corneas.
  • Lifestyle factors – Certain laser surgery techniques tend to be recommended for different types of lifestyles. While one aspect of this relates to a person’s visual demands, such as whether they have presbyopia and need treatment for both distance and reading vision, certain hobbies and vocations can also exclude certain surgery methods on the basis of safety. An example of this is a patient who serves in the armed forces or who undertakes wrestling as a pastime – LASIK surgery involves the formation of a hinged corneal flap before the underlying cornea can be reshaped. Although rare, this corneal flap may become dislodged in the event of physical trauma, making LASIK an unsuitable solution for such a patient. Another technique such as PRK or SMILE® would be more appropriate.
  • Pre-existing eye conditions – Some patients may be counselled against any type of laser eye surgery due to a pre-existing eye disease such as keratoconus or an active corneal infection. In many cases, manipulating the corneal tissue may exacerbate such conditions, which either need to first be treated and resolved, or may simply exclude the patient from refractive surgery altogether. Pre-existing dry eye, although not a complete contraindication to refractive surgery, may guide the surgeon to recommending a technique less likely to worsen the dryness, such as SMILE® instead of LASIK.

 

If you’ve been wondering ‘is laser eye surgery safe?’, the answer is yes. Of course, there are still risks involved but a discussion with your ophthalmologist will help to ensure you are counselled to the most appropriate technique for your situation. Call us now at (03) 9070 3580 for a consultation.

 

 

Note: Any surgical or invasive procedure carries risks. Before proceeding, you should seek a second opinion from an appropriately qualified health practitioner.