The Science Behind Laser Vision Correction

Recognizing the Value of Visual Clarity and Acuity

The factors that help determine visual acuity include refractive error, visual angle, illumination and/or brightness, contrast, and period of exposure. Other potential indicators are irradiation, colour, glare, width of pupil, attention, and fatigue. The benchmark for healthy (or “perfect”) vision is typically a visual acuity measurement of 20/20.

However, there are a significant number of people whose vision does not fit within these parameters, meaning they suffer from vision loss. This may range in severity depending on the cause, extent of damage, and pre-existing conditions. 

Vision loss is defined on a broad scale as a limitation in one or more functions of the eye or visual system, most commonly involving:

• Impairment of visual acuity

• Impairment of visual fields

• Impairment of colour vision

The main causes of vision loss vary from case to case. However, there are currently four categories and an “other” that are used to make a diagnosis. They include:

• Age-related macular degeneration (AMD)

• Cataract

• Diabetic retinopathy (DR)

• Glaucoma

• Other causes of vision loss

Decreased visual clarity and acuity come with a multitude of challenges. The various cost components can impact every aspect of an individual’s life, affecting their overall quality of life, well-being, and longevity. The cost of vision loss is comprised of four components:

• Healthcare system costs

• Productivity costs

• Other economic and financial costs

• Loss of well-being

The Importance of Visual Acuity

Visual acuity is a measurement used to determine how sharp your vision is when you look at objects at a certain distance. It is typically represented in fractional scores, the most commonly recognized one being 20/20.

Eye care professionals measure visual clarity or acuity through a variety of different tests designed to determine how sharp or clear someone can see from 20 feet away. From there, a determination is made about the quality of your vision, and if any further intervention is required to help improve it.

Why does visual acuity matter?

Considering how much we rely on our eyesight to get through our day-to-day lives, we must receive the necessary care and support. Understanding your visual acuity matters for the following reasons:

Treatment: Conducting an eye exam ensures you receive the correct medication and/or treatment for any potential eye disorders or vision issues.

Legal functions: Visual acuity tests can help determine your eligibility for certain legal privileges, such as possessing a driver’s license.

Monitoring disease: Regular visual acuity tests can help monitor the progression of eye diseases, while also showing the effectiveness of current treatments.

Anyone who does not have a visual acuity score of 20/20 could be a candidate for visual correction, including eyeglasses, contact lenses, and/or vision surgery, such as LASIK. The extent of your treatment should be determined by a healthcare professional.

The Science Behind Laser Vision Correction: Corneal Reshaping

LASIK

Recognized as the most commonly performed laser vision correction procedure, LASIK (laser-assisted in-situ keratomileusis) combines the application of an excimer laser and a hinged corneal flap.  

The excimer laser is a computer-controlled laser that allows an eye care professional to have complete control over the amount of tissue that is removed from the cornea. During the procedure, a layer of the cornea (known as the corneal flap) is folded back to provide access to a deeper layer of the cornea that is reshaped by the excimer laser.

PRK

PRK (photo-refractive keratectomy) was the first type of laser vision correction to be performed. During the procedure, the outer layer of corneal skin cells is removed. The entire layer of corneal skin is removed without creating a flap, ensuring the tissue underneath can be reshaped. Once the skin removal is complete, an excimer laser is used to reshape the corneal tissue to help correct vision.

SMILE

Combining the benefits of both LASIK and PRK, the SMILE (small incision lenticule extraction) procedure requires only a small incision without creating a flap. Using a single laser, a thin contact lens-shaped layer just beneath the surface of the cornea is created. This layer is then removed through a tiny 2 to 3-millimeter opening, leaving the surrounding tissues to heal together.

Correcting Refractive Errors: Nearsightedness, Farsightedness, and Astigmatism

Nearsightedness

Nearsightedness—also known as myopia—refers to a vision issue where objects far away appear blurry. This occurs when your eyeball is either too long or your cornea is too curved, forcing light to focus in front of your retina rather than precisely on it. As a result, distant objects appear blurry to you. 

Treatments include:

• Prescription eyeglasses

• Contact lenses

• Laser vision correction

Farsightedness

Farsightedness—also known as hyperopia—occurs when your eyeball is shorter than normal, or your cornea is not sufficiently curved. Symptoms of this condition can include blurry vision up close and/or discomfort when focusing on reading or writing tasks. When this happens, your long-range vision remains unaffected. 

Treatments include:

• Prescription eyeglasses

• Contact lenses

• Laser vision correction

• Astigmatism

Astigmatism is usually indicated by vision that is blurry at all distances. This is caused when the curvature of your cornea and your lens does not match, which results in overlapping images that appear blurry. Astigmatism can either be present at birth or the result of an eye injury, disease, and/or surgery. 

Treatments include:

• Prescription eyeglasses

• Contact lenses

• Laser vision correction

Precision and Customization: Optimizing Visual Acuity Outcomes

EX500 Excimer Laser

With its increased speed and precision, this blade-free method of accessing the underlying corneal tissue helps patients achieve optimal vision.

IntraLase

This approach allows doctors to create a corneal flap without having to use a traditional microkeratome. Using highly precise laser energy, this process eliminates the need for a blade, thus reducing the risk of flap complications.

Wavefront LASIK

Wavefront technology makes it easier to create a custom treatment plan for patients who are undergoing laser vision correction. Through eye-mapping technology, this tool can detect minute, high-order aberrations. This map is then used to guide the laser throughout the entire corrective procedure.

Photo-Refractive Keratectomy (PRK)

Using a precise laser to correct a patient’s vision problems, this technology eliminates the need to create a flap in the cornea. Instead, the thin protective top layer of corneal cells is removed. A laser is then applied directly to the cornea, altering its shape and addressing any visual errors.

Factors Influencing Visual Acuity Outcomes

To achieve good visual and refractive outcomes after a laser vision correction procedure, eye care professionals must pay attention to all aspects of care regarding the patient. Regularly reviewing procedures retrospectively can help achieve lower complication rates, while simultaneously improving overall visual outcomes.

The Importance of Laser Vision Correction

It is recommended that people receive comprehensive visual acuity tests regularly to prevent the development of vision issues, diseases, and other impairments. With the appropriate solution—whether that be eyeglasses, contact lenses, or laser vision correction—most people can achieve clear vision.