REFRACTIVE DEFECTS OF THE EYE

Myopia

Myopia is a refractive error in which distant objects cannot be seen clearly because the cornea is longer than normal. In individuals with myopic eye defect, the light coming into the eye from outside is refracted incorrectly in the cornea and focused in the anterior region of the retina. As a result, myopic patients cannot see far away clearly.

Myopia is one of the most common eye problems all over the world and is seen in more and more people every day. One of the main reasons for this is the increasing use of technological devices such as phones, tablets, televisions and smart boards in daily life.

The first symptoms of myopia often appear between the ages of 6-13. Myopia symptoms occur at an early age with problems such as not being able to see letters clearly in the classroom environment. In adults, it causes complaints such as not being able to see subtitles while watching television and having difficulty driving at night.

The disease is diagnosed during a general eye examination. If the person is diagnosed with myopia at an early age, the degree of the disease may progress until the post-adolescent period.

For the treatment of myopia, the quality of life of patients can be improved with methods such as glasses, contact lenses and laser eye surgery. Treatment can be performed more easily at low degrees of visual defect. As myopia progresses, there is a risk of permanent vision loss. The risk of diseases such as glaucoma, cataracts and retinal detachment also increases in people with high degrees of the disease.

Myopia is the problem of not being able to see far away clearly due to the fact that the light entering the eye cannot be focused properly in the retina due to the long outer layer of the eye. Patients have difficulty seeing distant objects and various signs, while they have no problem seeing near.

Myopia is a refractive error like hyperopia and astigmatism. The light that enters the eye is refracted in the frontmost transparent layer (the cornea) and the lens to reach the visual point on the retina. In a healthy eye, this process takes place without a refractive error and the light is focused exactly where it should be. If there is a problem with the curvature of the cornea or lens, the light falls to a point in front of the retina. As a result, myopia, the inability to see far away clearly, occurs and blurring of distance vision occurs.

What are the Symptoms of Myopia?

Symptoms of myopia are generally similar among adults. However, there are differences in symptoms between children and adults. Myopia symptoms in adults are often manifested as follows.

• Failure to see distant objects clearly and blurring of distant landmarks
• The need to squint the eyelids in order to see far away clearly and clearly
• Headache complaints due to eye strain
• Double vision due to eye strain
• Halos in the field of vision as a result of strenuous eye activity
• Difficulty driving, especially at night, during sunrise and twilight
• Difficulty reading signs and license plates at night
• Difficulty in perceiving changes in traffic flow at a distance while driving

Myopia is usually detected in childhood and shows its first symptoms during this period. Symptoms of myopia in children are as follows:

• Eye shift or strabismus
• Rubbing the eyes at significant intervals
• Desire to sit closer to the blackboard in the classroom and closer to the television and computer screen at home
• Distant objects attract less attention
• Frequent blinking

What Causes Myopia?

The human eye has two parts, the cornea and the lens, which allow it to focus images. The cornea is the dome-shaped open surface of the eye. The lens is a transparent biconvex structure. In a normally shaped eye, each of the focusing elements has a smooth curvature. Myopia is seen when the eyeball is longer than normal or the cornea is too curved.

Myopia can be caused by genetic and environmental factors. If the cause of myopia is due to genetic factors, it can be congenital, and if it is due to environmental factors, it can occur later due to various external factors.

Some of the environmental factors include:

• Spending insufficient time in daylight
• Spending a lot of time with devices such as smartphones, computers and tablets in daily life
• Excessive reading and prolonged focus on nearby signs increase the risk of myopia
• The habit of engaging in eye-straining activities in poorly lit environments
• Myopia can also occur in people with diabetes or cataracts. Apart from these general causes, the disease can also occur due to special conditions such as
• The ciliary muscle contracts and stays contracted
• Myopia development can be observed in conditions that can affect lens hydration, such as elevated blood sugar, pregnancy toxemia and dysentery
• Retinopathy of prematurity and myopia may occur in newborn babies after uncontrolled oxygen therapy
• Some types of medication such as alcohol, corticosteroids, tetracyclines, neuroleptics can cause edema where the ciliary muscle is located. This can cause the lens of the eye to be pushed forward and cause problems with distance vision

When should you consult an ophthalmologist?

An ophthalmologist should be consulted for any symptoms related to vision. If you have blurred vision when looking at distant objects and signs, which is one of the symptoms of myopia, and if this blurring prevents you from performing your daily activities, it is useful to consult an ophthalmologist.

Göz sağlığı için temel hususlardan biri de düzenli göz doktoru kontrolüdür. Bu noktada önerilen yaklaşım ailesinde miyop olan kişiler;

• Every 5-10 years in your 20s and 30s,
• Every 2-4 years between 40 and 54,
• Every 1-3 years from age 55 to 64,
• Every 1-2 years after the age of 65

should not neglect regular ophthalmologist check-ups.

Regular eye check-ups are important for early diagnosis of myopia and other eye problems in children. After 6 months of age, 3 years of age, pre-school and school age, an ophthalmologist check-up is recommended every two years.

Types of Myopia

Simple Myopia: It usually starts between the ages of 6-18. Although the degree is less than 6, it may progress for 3-4 years after it starts and then pause.

Curvature Myopia: It is the type that occurs as a result of the increase in refraction due to the increase in the curvature of the cornea or natural lens in the eye over time. Conditions such as corneal ectasia and keratoconus can cause this form of the disease.

Refractive Myopia: As a result of diabetes or other different metabolic disorders, the refractive rate in the lens of the eye may increase in the initial stage of the cataract problem due to the aforementioned metabolic disorders, so the possibility of myopia occurs.

Axis Myopia: Except for the abnormal anterior and posterior length in the outermost layer of the eye, there is no abnormality in all eye structures. Despite conditions in which all eye elements can be considered to have a healthy light refraction, the light coming into the eye is focused in front of the retina due to the length of the anterior and posterior diameter of the eye.

Congenital Myopia: It is usually recognized at the age of 2-3 years when the child is not interested in distant areas and ignores distant objects, events and signs. It is a high-grade form of the disease that is often non-progressive.

Pathological Myopia: Mostly cases above 7 degrees. Due to the over-extension of the anterior and posterior axis of the eyeball, the retinal tissue covers the nasal area of the pupil. Thus, the vessels make a curve and come out of the optic nerves. Degenerative changes occur especially in the posterior part of the eye.

Night Myopia: Although there is no deterioration in vision during the daytime or in lighted environments, there is deterioration in the quality of vision at night or in dimly lit environments. It is one of the common types of myopia. It is very dangerous when driving at night. Therefore, glasses must be worn when driving at night.

False Myopia: It is a temporary vision problem that occurs as a result of sudden spasms in the eye and surrounding muscles.

Degrees of Myopia

Eyes with myopia grades of -4, -3, -2, -1, 0 and 0.75 are defined as low, -4 to -6 as medium and -6 and above as high grade.

How is Myopia Test Performed? How is it Diagnosed?

The myopia test is performed to determine the degree to which the eyes can focus on distant shapes and to determine the degree of optical lenses needed to correct distance vision.

This test measures visual acuity written as a fraction of 20/40. During the test, the patient is shown letters on a Snellen chart and is asked to recognize the letters.

Using a device called a phoropter, the ophthalmologist places a series of lenses in the front of the patient's eye. Afterwards, the light focus of the eyes is measured with the help of a retinoscope. The glasses number, i.e. the degree of vision problem the person has, is determined according to the answers given by the person. If deemed necessary, the doctor may also use eye drops to keep the focus of the eye unchanged during the test.

Once myopia has been diagnosed in a person, periodic eye examinations should also be performed. Eyes with a larger than normal cornea and outer surface are at risk of retinal tears. If these tears are not recognized early, larger vision problems may occur in the future.

How is myopia treated?

Myopia treatment is performed with one of the following options: prescription glasses, prescription contact lenses, laser treatment or intraocular lens surgery.

For the treatment of myopia, glasses or contact lenses can be used continuously depending on the degree of the person's refractive problem, or they can be used while doing certain jobs. Glasses or contact lenses do not reduce the degree of the disease, but can only prevent the eye degree from increasing.

One of the main concerns of myopic patients is the increase in eye numbers. Although the number increase is usually experienced during the growing age, it stops between the ages of 18-21 when puberty begins to end. Glasses, contact lenses and eye laser applications are treatment options for eyes up to 6-7 degrees. Myopia, which causes retinal degeneration, can increase when the eye number is above 8-10 degrees and after the age of 20.

If the patient's eye number is at a level that cannot be corrected by eye laser surgery due to its thin cornea structure and high degree, intraocular lens treatment can be applied between the ages of 35-40 and later. The lenses in question are monofocal lenses, trifocal lenses and phakic intraocular lenses. Which intraocular lens treatment is appropriate for the patient is decided by the ophthalmologist after a general eye examination and various examinations together with the patient.

For the treatment of myopia, laser eye surgery can be applied to other patients after the age of 18. Myopia is permanently treated with laser eye surgery applications.

Laser Treatment for Refractive Defects

There are many different options for laser treatment of myopia. The most commonly used laser treatment methods are No Touch Laser, LASIK, Femto LASIK and I-LASIK, which are excimer laser types. Laser treatment is usually applied after the age of 18. In order for laser treatment to be applied, it is necessary to make sure that the eye number does not increase.

The appropriate myopia treatment for the patient is decided by the ophthalmologist after eye examinations and various examinations. Excimer laser methods are recommended for patients who do not prefer to wear glasses and contact lenses.

Hyperopia:

Hyperopia is a vision defect, also known colloquially as "farsightedness". Because the outside of the cornea is smaller than normal, light from outside is focused on the back of the retina. As a result, patients cannot see near objects clearly.

Hyperopia is one of the most common refractive problems in our country and in the world. It is usually a congenital visual defect with genetic transmission. While hyperopia in infants disappears spontaneously when they complete their eye development, some of them may continue to have this problem in childhood and adulthood.

Symptoms of hyperopia often appear in childhood. People with these symptoms say that signs and letters blur and intertwine when reading at close distances. They have difficulty doing fine work that requires close vision. After a while, these problems are accompanied by eye and headache problems.

While the primary treatment for hyperopia is provided with glasses or contact lenses, laser eye surgery is also among the treatment options after the age of 18. As with many vision problems, early diagnosis and treatment is very important. Refractive errors in the eye, when left untreated for a long time and recognized late, can lead to significant problems such as lazy eye and strabismus over time.

For these reasons, it is important for the eye health of people over the age of 40 who do not have any eye disease or visual defect in their family's health history or in themselves to undergo regular ophthalmologist check-ups every 3-4 years.

What is Hyperopia?

Hyperopia is a near sight problem that occurs when the rays coming into the eye focus on the back of the retina instead of the surface of the retina. People with this problem have smaller pupils than normal. Accordingly, the cornea and the eye lens do not have the power to refract the rays coming into the eye sufficiently.

Hyperopia is a refractive problem like astigmatism and myopia, but is sometimes confused with presbyopia. Hyperopia is a congenital refractive error and is caused by a deformity of the cornea. Presbyopia, on the other hand, is a problem of blurred near vision caused by the loss of flexibility of the lens of the eye after the age of 40. In addition, these people usually do not have a problem with distance vision, but only with seeing nearby letters, objects and signs.

To understand hyperopia and various other refractive errors, it is useful to first understand the pathways through which vision functions. In healthy vision, the rays coming into the eye from the outside first pass through the cornea, the outermost layer of the eye, to the natural lens of the eye, where they are refracted again. As a result, they are evenly distributed to the visual point on the retina and fall in an inverted manner. The image falling invertedly on the fovea centralis region on the retinal surface is perceived by rod and cone cells and sent to the brain via nerve cells. The brain processes and makes sense of these images transmitted to it through the retina. In this way, the visual function is realized.

The problem in people with hyperopia is that the elements that refract this image as light enters the eye are shorter than normal. Therefore, the light coming into the eye from outside is focused behind the retina instead of falling on its full surface. As a result, blurring of near vision occurs.

Degrees of Hyperopia

Patients with a high degree of refractive error may have problems with distance vision as well as near vision. The severity of near sight due to refractive error is also classified according to its degree.

When it comes to the degrees of the disease, below 2 degrees are characterized as mild, between 2-5 degrees as moderate and above 5 degrees as high-grade cases.

Types of Hyperopia

Accommodative Type: A type in which the eye can only see near with the help of certain movements that stimulate the lens.

Structural Type: It is formed by the structure of the refractive elements of the eye. It is divided into 3 types.

Axial Type: It is the most common type of near sight problem. The main reason is the short anterior posterior length of the eye.

What are the Symptoms of Hyperopia?

• Slipping of letters or lines while reading
• Eye and headaches in people who read for long periods of time
• Seeing letters as intertwined in writing
• Rapid eye fatigue when looking up close
• Failure to see clearly up close

What Causes Hyperopia?

Hyperopia, which usually occurs with advancing age, can also be congenital. However, it can also increase with advancing age, this is due to the progressive decrease in the power of accommodation with age. In addition, genetic factors play an effective role in the formation of this visual defect. 

How Does a Hyperopia Patient See?

Hyperopia is a general problem of near sight. Patients experience deficiencies in visual acuity when reading at close range, as well as seeing blurred signs at close range. When people with hyperopia read from a book or a digital screen, they see letters and signs intertwined. 

How is Hyperopia Diagnosed?

The diagnosis of hyperopia is based on an ophthalmologist's eye examination, vision test and various measurements. During these measurements, it can also be measured whether the person has other refractive errors such as myopia and astigmatism.

If there is evidence of the disease, the degrees for each eye are determined with the help of a refractometer. In some patients, measurements can also be made by retinoscopy.

During these measurements, a harmless light is shone into the eye and it is determined how and to what degree this light is reflected from the retina. With this examination, the reflection of light is measured to determine whether the person can be diagnosed with nearsightedness. In addition, if the person is diagnosed, the degree of lens in question is also determined in order to obtain a healthy vision.

How is Hyperopia Treated?

Hyperopia is treated with prescription glasses, prescription contact lenses or laser surgery. The ophthalmologist determines one of the treatment methods suitable for the patient. The degrees of patients with very low degrees and symptoms are monitored with regular examinations.

If the ophthalmologist diagnoses farsightedness, the priority is the use of glasses or contact lenses. At this point, the main purpose of the treatment is to ensure that the image is focused at the right point on the retina.

The most commonly used method for the treatment of hyperopia is treatment with prescription glasses. In contrast to the thick-rimmed concave lens used in myopia treatment, thin-rimmed convex lenses are used. The lenses can become thicker depending on the degree of nearsightedness. This can affect image quality and sharpness. Whether glasses will be worn continuously varies from patient to patient.

In the use of contact lenses, a lens suitable for the patient's refractive error is prescribed to the patient. The patient places this contact lens in the anterior region of the cornea, the outermost surface of the eye. Some contact lenses are removed before going to bed, while others remain in the eye for a long time. It is important to pay attention to hygiene when wearing contact lenses to prevent infection of the eye.

Lens and spectacle wear have their own advantages. Both treatment methods improve the quality of life of the person and do not reduce the degree of refractive error.

The last method to be used for treatment is intraocular lens implantation. If the person's eye is not suitable for laser operation, phakic intraocular lens surgery can be applied if the patient meets the appropriate conditions.

What are the methods used in hyperopia treatment other than glasses and lenses?

Intraocular lens treatment is one of the most recommended methods by physicians in the treatment of near vision impairment. Thanks to this method, patients can continue their lives without the need for glasses. Another method recommended for treatment is laser treatment. There is no 100% zero number guarantee after laser treatment, but approximately 90 out of 100 people who have laser treatment for farsightedness can see fully without glasses or contact lenses.

Astigmatism:

Astigmatism is a vision problem caused by the incompatible curvature of the cornea or the lens of the eye due to its structure. Due to its formation, it is a refractive error like myopia and hyperopia. As with other refractive errors, light cannot focus on the point where it should focus on the retina. Depending on the type of astigmatism, it can focus in front or behind the retina. Thus, astigmatism patients cannot see clearly near or far depending on the area on the retina where the light falls.

Astigmatism is derived from the Greek prefix "a" meaning deprivation and stigma meaning point. The meaning of the word origin is the absence of a focal point in Greek. It is an eye problem characterized by blurred vision for distance or near vision, or both.

Astigmatism is one of the most common eye health problems worldwide, usually occurring at birth. From the moment the vision problem occurs, both distance and near vision are affected. The person sees distant objects and near objects blurred. Common symptoms are blurred vision in one direction horizontally, vertically and diagonally.

Astigmatism symptoms are usually first noticed during school age. Symptoms can manifest themselves for any distance. As with other eye problems, it is beneficial to consult an ophthalmologist for the success of the treatment from the moment the symptoms first appear.

Astigmatism treatment is performed with methods such as glasses, contact lenses or eye laser surgery if the refractive problem is at levels that affect the daily life of the person and reduce the quality of life. Astigmatism is more common in people with a family history of astigmatism and in people who have undergone surgical procedures related to eye health in the past.

What is Astigmatism?

The cornea, located in the front layer of the eye, has the task of protecting the eye from external factors and refracting light correctly. A properly structured cornea refracts light and transmits it to the retina, the mesh layer at the very back of the eye. The transmitted images allow us to see clearly.

In the eye with refractive error, the cornea cannot refract the incoming light correctly because there are some irregularities in the shape of the cornea, causing the image to be transmitted to the retina as blurred. It is a condition where the rays coming into the eye cannot be focused on the retina. 

What are the Symptoms of Astigmatism?

The most common astigmatism symptoms are as follows:

• Blurred vision at near, far and intermediate distances, distortions in different parts of the visual field,
• Eye fatigue and eye pain after reading or visual activities that require attention,
• Headache
• In severe cases, double vision and strabismus,
• Difficulty driving at night,
• Blurred vision of illuminated text and signs accompanied by light beams,
• The desire to squint to see clearly,
• Blepharitis,
• Frequent stye formation in the eye

How Does an Astigmatism Patient See?

In an eye with astigmatism, due to irregular curvature of the cornea or lens, the rays cannot focus normally on the retina and refractive error occurs. People with astigmatism cannot see clearly at near or far distances. Sometimes both near and far vision problems occur together.

They see the objects and shapes they look at as blurred with elongated and diffuse edges. They also see light rays on the edges of illuminated objects at night. However, among the symptoms of astigmatism, the deformity of vision is the characteristic feature of the disease.

What Causes Astigmatism?

Refractive errors can be genetic, congenital or caused by diseases that can cause changes in the cornea. Another effective reason for this formation is trauma to the eye or after an eye operation. One of the most important causes is keratoconus disease.

How is Astigmatism Diagnosed? How is the Test Performed?

Astigmatism can be detected by a detailed eye examination by an ophthalmologist. The astigmatism test is performed to determine the number of optical elements needed to improve the patient's vision by measuring how the eyes focus light. The following tests and examinations are used during this determination.

Visual acuity testing is performed at the first stage of the diagnostic and therapeutic procedure. It is a routine test to help diagnose astigmatism. During the test, the person is asked to read certain letters and signs from a distance of 20 feet. The lower the value in the denominator, the lower the visual acuity.

The ophthalmologist uses a phoropter to place a series of lenses in front of the patient's eyes to measure the focus of light. The measurement is done with the help of a lighted hand-held instrument called a retinoscope. Various letters and signs are shown to the patient and according to the answers, the degree of astigmatism is diagnosed and the optical material that gives the person the clearest vision is determined.

The ophthalmologist also measures the patient's corneal curvature using keratometry. The ophthalmologist focuses a circle of light on the cornea and measures the reflection of light. Corneal topography can also be used. This reveals the shape of the cornea and measures the curvature in specific areas of its surface. This measurement can also be used to determine whether the patient is suitable for contact lenses.

How to Treat Astigmatism?

Refractive errors can be diagnosed with a general eye examination and treated with glasses or contact lenses prescribed by a doctor. Eyeglasses or contact lenses do not cause eye degrees to regress.

For a complete cure, refractive surgery (laser or intraocular lens) may be recommended, depending on eye suitability. For severe cases, doctors may usually recommend refractive surgery. This type of surgery uses lasers or small blades to reshape the cornea for permanent correction.