Eye diseases and degenerations and laser vision correction

Refractive surgery enables patients with vision defects to enjoy life without glasses or contact lenses. What happens if qualifying examination results reveal that a candidate for the procedure suffers from an eye disease or degeneration? Is every eye condition an absolute contraindication to laser vision correction treatment?

What eye diseases are most commonly diagnosed during the preliminary examination qualifying for the laser vision correction surgery?

• Keratoconus
  This disease occurs when the cornea becomes thinner and bulges into a cone shape, which causes the light rays that fall on the retina to blur. As a result, a person with keratoconus sees a blurred and distorted image that cannot be properly corrected either with glasses or contact lenses. Other symptoms of keratoconus include: hypersensitivity to light and glare, eye redness and swelling or double vision.
• Glaucoma
  The eye constantly produces the so-called aqueous humour stale that is responsible for removing harmful metabolic products and nourishes the cornea and the lens. It is located in the anterior and posterior chambers of the eye. As new liquid flows in, the same amount needs to be drained. The fluid finds its outlet through an area known as the drainage angle. This process keeps the pressure in the eye stable. We talk about glaucoma when the drainage angle does not function properly, resulting in excessive accumulation of the aqueous humour and in turn increased intraocular pressure. This condition leads to gradual damage to the optic nerve. Typical symptoms of glaucoma include: headaches, eye pain, frontal pain, decreased or blurred vision, increased intraocular pressure, and visual field defects. Untreated glaucoma can lead to blindness.
• Cataract
  The natural intraocular lens contains crystallins, i.e. unique proteins that constitute its main protein components. Some of them are soluble in water; however, with age the number of insoluble proteins increases and the degree of hydration of the lens decreases. These proteins begin to break down, causing the lens to fog. Consequently, a person suffering from cataract sees a blurry, hazy or less colourful image. The changes that occur during the development of cataract are irreversible and they progress individually.
• Retinal and macular degeneration
  The retina is a thin layer of cells that lines the posterior wall of the eye. It reacts to light and converts it into nerve signals, which then travel to the brain, making us able to see. The macula is the central part of the retina, which is responsible for the sharpest visual acuity. Diseases that lead to retinal or macular degeneration may manifest themselves with a variety of symptoms. The most frequently observed symptoms include sudden or gradual vision deterioration or distortion of the visible image, scotomas, flashes, and a visible dark spot in the very centre of the visual field. The group of diseases associated with damage to the retinal or macular structure includes the following: retinal detachment, retinal degeneration (e.g. lattice degeneration), diabetic or hypertensive retinopathy or age-related macular degeneration (AMD).
• Dry Eye Syndrome (DES)
  The eyes need tears to to stay healthy and comfortable. If they do not produce a sufficient amount of them, it is called the Dry Eye Syndrome (DES). DES also occurs when the eyes do not produce the right type of tears or the functioning of the tear film is distorted. The condition is accompanied by a range of symptoms, such as burning and stinging sensations, eye redness, excessive tearing and periodic vision fluctuations. The cause of DES may be the use of certain medications or the occurrence of systemic diseases.

Is every eye disease an absolute contraindication to laser vision correction?

Laser vision correction involves remodelling the anterior part of the cornea using an excimer laser. Thanks to this, the image is properly focused on the retina, which means the patient can enjoy sharp vision, permanent correction results and life without the necessity to wear glasses or contact lenses. The treatment does not interfere with the deeper structures of the eye, e.g. the optic nerve.

Certain eye diseases are an absolute contraindication to performing a laser vision correction surgery. Why? Degenerative diseases, such as advanced glaucoma or macular degeneration gradually lead to a loss of sight. In such a case, laser correction will not help to improve vision, which is why the patient is not eligible for the procedure.

In the case of keratoconus or cataract, a laser vision correction procedure is not recommended only for a certain time. It is necessary to perform a cataract removal surgery first. Then, after 6 months, the patient can undergo the laser vision correction procedure to further improve eyesight. For those who have previously been disqualified from the laser vision correction surgery due to keratoconus, the cross-linking treatment may increase their chance for positive qualification result.

Dry Eye Syndrome is a condition which is a relative contraindication to undergoing the laser vision correction procedure. Everything depends on its severity as well as on the degree of eye dryness, because it may negatively affect the corneal healing process following the surgery. It is then necessery to implement pharmacological treatment (such as antiinflammatory and moisturising drops or ointments) or take other measures, for instance implants in the lacrimal point. Followingsuccessful treatment, the laser vision correction procedure can be considered. If the Dry Eye Syndrome occurs as a secondary condition in the course of general diseases, it is absolute contraindication to the laser vision correction surgery.

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