Refractive Defects

What is refractive error?

It is the inability of the rays of light coming into the eye to fully focus on the visual center (retina). It is a common disorder that reduces the visual acuity of the eye. It is characterized by difficulty in seeing far or near.

What are the types of refractive errors?

There are 4 types of refractive errors;

Emetropia: Eyes with full distance vision and no visual defects.

Myopia: It is the focusing of rays coming parallel to the eye in front of the retina. The anterior posterior diameter of the eye is longer than normal. This feature is structural and is passed on genetically. Myopes can see near but not far.

They usually squint when looking into the distance. Until the age of 18, the degree of myopia may increase as growth continues. However, it may also increase after the age of 18 due to the increased use of cell phones and tablets.

Hyperopia: It is the focusing of rays coming parallel to the eye behind the retina. The anterior posterior diameter of the eye is shorter than normal. Hypermetropes have difficulty seeing near, but if they have high numbers, they also have difficulty seeing far. Low-numbered hypermetropes can see with accommodation, but in this case they complain of eye fatigue. They feel eye discomfort and headaches, especially when they have to work close for a long time.

Astigmatism: It develops when the rays coming into the eye are refracted in different planes and do not form a single focus. Astigmats have blurred vision both near and far. It may be accompanied by hyperopia or myopia.


Presbyopia: It is the normal aging process of the eye. Since the lens is flexible in young people, the anterior posterior diameter of the lens increases while looking close, increasing its refractive power and providing clear vision near. However, the lens hardens with age. In this case, near vision deteriorates and reading becomes difficult. It starts approximately at the age of 40 and progresses with age.

What are the risk factors for refractive errors?

Refractive error can be seen in everyone in the society. However, if there is a refractive error in the family, the likelihood of it being seen in other members of the family increases. Presbyopia is seen in everyone with age.

What are the symptoms of refractive errors?

These symptoms include blurred vision, headache, eye fatigue, double vision, squinting and difficulty in reading.

What is the treatment method?

Glasses: Wearing glasses does not cause the number to progress or regress. It improves the

defective focusing and provides a clear image on the retina. It also helps to prevent symptoms such as eye strain and headaches.

Contact lenses: They are no different from glasses in terms of clarifying the image and relieving symptoms caused by blurred vision. However, they require care and are not suitable for younger patients.

Excimer Laser: With the laser treatment method, suitable patients can get rid of some or all of their refractive errors. In excimer laser treatment, the method suitable for the eye is decided

after a detailed examination. Until the age of 18, excimer laser treatment is not applied to any patient.

PRK: In this application, an area of 9 mm is scraped from the epithelial layer on the cornea and made epithelium-free. Then laser treatment is applied. The epithelium will then renew itself.  After this procedure, patients may feel pain for the first 3 days.  It may take up to 6-8 weeks for the best vision to recover.

F-LASIK: This procedure has two stages. First, a layer (flap) is created from the cornea with a thin and circular incision. The corneal flap is carefully lifted towards the hinge. In the 2nd stage, laser treatment is applied to the center of the cornea. Then the flap is carefully placed in place.

In this method, patients complain of stinging on the first day, but complaints regress on the 2nd day. It takes approximately 3-7 days for the vision to reach the best level. Improvement of vision is faster and more comfortable in terms of pain.

SMILE: This procedure has two stages. A lenticule is created in the cornea with a laser. Then this lenticule is removed through a 2-4 mm incision area. Since a smaller incision is created in this method, flap complications seen in flap surgery are not seen.

Since the corneal incision is smaller, dry eye due to loss of sensation is less common. Stinging may occur on the first day, but the patient’s complaints decrease on the 2nd day. Recovery of vision may take 4-5 weeks.

Intraocular lenses: With the development of cataracts, the lens inside our eye loses its transparency. With cataract surgery, the natural lens is removed and replaced with specially manufactured lenses. Previously, single-focal (monofocal) lenses were used, which allowed us to see far away clearly. However, patients had to wear close-up glasses after surgery because they had difficulty seeing near.

Today, with new technologies, multi-focal (trifocal / multifocal) lenses, also called smart lenses, have been produced that provide clear vision both far and near. While they used to be used only after cataract surgery, today they can also be preferred in young patients whose cornea is not suitable for refractive surgery.