Refractive errors are the most prevalent type of vision problem. More than 150 million people suffer from at least one type of refractive error in the United States alone. But as ocular technologies have developed, eye specialists have become more equipped to diagnose and treat these conditions, and help patients regain visual clarity.
What Are Refractive Errors?
Refractive errors are a classification of vision-related conditions that make it difficult to see clearly. This problem occurs when the shape of the eye keeps light from focusing on the retina, the light-sensitive layers of nerve tissue at the back of the eye. When light enters the eye, the cornea – the clear front layer of the eye – refracts it onto the lens. So, instead of light focusing on the retina, it focuses in front of or behind it. This then results in blurred vision.
What Are the 4 Types of Refractive Errors?
An optician discusses the four main types of refractive errors:
1. Nearsightedness (Myopia)
Nearsightedness makes far-away objects appear blurry. It occurs when there is a problem with the shape of the lens or cornea, or when the eyeball grows too long from front to back. Both of these conditions make light focus in front of the retina.
This refractive error typically starts from 6 to 14 years of age. Studies have found that children who spend more time outdoors are less likely to develop nearsightedness. Severe nearsightedness, also known as high myopia, can increase the risk of other eye conditions like retinal detachment.
2. Farsightedness (Hyperopia)
Farsightedness makes nearby objects appear blurry. Instead of having a cornea that is too steep, which is the case of nearsightedness, those who are farsighted have a cornea that is too flat. It makes light focus behind the retina instead of on it. People with this condition are usually born with it.
Astigmatism can make nearby and faraway objects look distorted. It occurs when the cornea or lens has an irregular shape, making light refract differently as it enters the eye. Some individuals with this type of refractive error are born with it, although many people also develop it as children or young adults. It is common to have astigmatism in conjunction with another refractive error like nearsightedness or farsightedness.
Presbyopia makes it difficult for older adults to see things at a close distance. As you age, the lens in your eye stiffens and loses its ability to zoom in and out. It prevents light from focusing correctly on the retina.
Everyone gets presbyopia as they get older, commonly after the age of 45. Like astigmatism, presbyopia may also come with another type of refractive error.
What Are the Symptoms of Refractive Errors?
Common symptoms of refractive errors include:
Having blurry, double or hazy vision
Seeing a glare around bright lights
Feeling a strain in the eye, especially when it is tired or sore
Having trouble focusing when reading a book or looking at a screen
It is important to get annual eye exams so your doctor can make sure your vision is as clear as possible. If you wear lenses or glasses and have these symptoms, chances are you need a new prescription. Talk to your eye specialist and be transparent about the vision problems you are experiencing so they can help you find the appropriate treatment for your condition.
How Do Eye Doctors Check for Refractive Errors?
Refractive errors are assessed as part of a comprehensive eye examination. An eye doctor will ask the patient to read letters that are up close and far away and may give the patient eye drops to dilate their pupil and check for other eye-related problems.
What Are the Treatments for Refractive Errors?
Eye doctors can treat refractive errors with glasses or contact lenses or, in some instances, surgery.
Glasses and Contacts
Eyeglasses are the simplest and safest way to correct refractive errors. The eye doctor will prescribe the right eyeglass lenses or fit you for the right contact lenses to give you the clearest vision possible. With contact lenses, the doctor will also show you how to wear, clean and store them properly.
The only way to correct refractive errors without glasses or lenses is via refractive surgery. For corneal-related issues like myopia, hyperopia or astigmatism, laser vision correction works best as these procedures reshape the cornea to improve its focusing power. LASIK is the most common type of refractive surgery. For age-related vision conditions, such as presbyopia, there are surgical procedures that focus on the lens.
What You Need to Know About LASIK Surgery
LASIK uses a strong beam of light to change the shape of the cornea and make vision clearer. After undergoing LASIK surgery, most patients see well enough that they stop wearing their eyeglasses or contact lenses for most of their day-to-day activities. LASIK, however, cannot fix presbyopia since everyone develops it as they age.
While the benefits of LASIK surgery make it seem like an appealing treatment for refractive errors, it is not for everyone. You will need a comprehensive dilated eye exam to know if LASIK surgery is right for you. There are eye conditions that can increase the risk of complications from LASIK. These include:
Keratoconus, a disease that makes the cornea thin and bulge outward over time
Eye infections like ocular herpes or hepatitis
Just like any surgery, LASIK can cause certain side effects, including blurry vision, sensitivity to light, dry eye, etc. These side effects usually go away after a few months, although your doctor may give you eye drops to ease them. Rarely can these issues be permanent.
What You Need to Know About Lens Replacement Surgery
Unlike corneal-related refractive errors that require the reshaping of the cornea, presbyopia and other age-related vision conditions require the replacement of the natural lens inside the eye with an artificial lens designed to provide focusing power according to the needs of the patient. This provides a long-lasting vision correction for conditions like presbyopia while also addressing other existing refractive errors, such as myopia, hyperopia or astigmatism. Generally, patients over the age of 50 with any level of nearsightedness, farsightedness or astigmatism can be suitable for lens replacement surgery.
Good health is crucial to be suitable for multifocal lenses. Individuals with macular degeneration, for example, will not be suitable for multifocal lenses. Those with diabetes are also not suitable for lens replacement. Those who have cataracts, however, are often fitted to have high-performance trifocal lenses.
The different types of lens replacement procedures are:
Refractive Lens Exchange (RLE)
This is a sought-after surgery for patients with presbyopia. During the RLE procedure, the dysfunctional natural lens in the eye is replaced with an advanced technology lens. Once you have this procedure, you will not develop cataracts as you get older as artificial lenses cannot get cataracts. Some doctors combine RLE with laser vision correction to treat any existing refractive error. Possible side effects of RLE include dry eye, red eye, blurry vision, light sensitivity and discomfort in the eye. These can last a few days to a week.
Refractive Cataract Surgery
Like RLE, cataract surgery involves replacing the natural lens with a synthetic lens. But whereas RLE is performed to minimize the dependence on glasses or contacts, cataract surgery is performed mainly to correct blur caused by a foggy natural lens.