Understanding Vision Problems—Types, Causes, and Correction, According to Germany's Ophthalmologists

The eye is an optical system, similar to a camera. Like a camera, the eye consists of several refractive media (particularly the cornea and the lens).

These refract incoming light (e.g., an image) so that it converges at a focal point on the retina—usually at the point of sharpest vision. The degree of refraction is called diopters.

If the incoming light rays are projected incorrectly onto the retina, the image becomes blurry, and this is referred to as a refractive error.

Illustration of nearsightedness and farsightedness caused by distorted eyeballs

• Nearsightedness (myopia)
• Farsightedness (hyperopia)
• Astigmatism (corneal curvature) and
• Presbyopia

Your eyeglass prescription provides information about the type of vision problem you have.

Here’s what the abbreviations on your eyeglass prescription mean:

R: Values for the right eye

L: Values for the left eye

sph (sphere): describes your nearsightedness or farsightedness in diopters (dpt). 

Negative values indicate nearsightedness. In the eyeglass prescription above, this is -3.75 dpt for the right eye. Farsightedness is indicated by positive values, e.g., +1.5 dpt.

cyl (cylinder): describes your astigmatism in diopters; in the example above, it is -1.0 dpt for the right eye. The sign does not matter.

ach (axis): indicates the axis of your astigmatism in degrees. In our example, the astigmatism in the right eye has a direction of 90°.

add (Addition): indicates the value for presbyopia once it develops. The value +2.75 dpt is added to the spherical correction.

In addition to correction with glasses and contact lenses, there are three laser correction procedures that alter the refractive power of the cornea: LASIK, LASEK, and PRK.

Thanks to precise laser technology, many refractive errors can be corrected simply, safely, and permanently.

The procedures differ in the microsurgical corrections they use to alter the refractive power.

The following procedures are available:

• Implantation of an artificial lens
• Replacement of the natural lens
• Removal of the natural lens

An ophthalmologist can determine which procedure is suitable for your eye through a detailed preliminary refractive examination.

Information on nearsightedness

Nearsightedness (myopia) is one of the most common types of refractive errors, along with farsightedness and astigmatism. The technical term “myopia” is derived from Greek: “myops” roughly translates to “squinting face,” because people with nearsightedness often do indeed squint. Due to nearsightedness, distant objects appear blurry.

In most cases, nearsightedness is caused by an eyeball that is too long. This can be hereditary, but it can also result from being born prematurely. It typically develops during the first three decades of life. Experts also refer to it as axial myopia.

Vision Correction for Nearsightedness @ ZZMC /AdobeStock

Another form of this condition is refractive myopia. In this case, the cornea or lens has excessive refractive power. Refractive myopia is also not uncommon in cases of cataracts with a severely clouded cornea. It is unclear whether external factors such as sunlight, prolonged screen time, or reading in poor lighting cause the condition.

It is rare for both eyes to be affected equally. In most patients, one eye has worse vision than the other. It often occurs in conjunction with astigmatism.

Symptoms of Myopia

The most obvious symptom is blurred distance vision. This is particularly noticeable at night in the early stages. However, patients can see nearby objects perfectly normally.

Diagnosis and Treatment of Myopia

A simple eye exam at an ophthalmologist’s or optometrist’s office can determine whether a person is nearsighted. A refraction test then determines the exact degree of the vision impairment. This is expressed in negative diopter values, such as -2.

All treatments aim to correct the refractive error so that the focal point of the incoming light rays is no longer in front of the retina but behind it.

This vision problem is usually corrected with glasses. However, younger people are more likely to opt for contact lenses or laser therapy, mostly for cosmetic reasons. Unfortunately, health insurance companies cover the costs only in exceptional cases.

Laser surgery is becoming increasingly popular. However, as with any surgery, complications can arise. The patient may still need vision correction even after the surgery. Laser surgery is not suitable for all nearsighted patients. Special examinations, however, can quickly provide clarity.

If you decide to use contact lenses, you should opt for hard lenses. Although it takes longer to get used to them, they are far more comfortable. A distinction is made not only between soft and hard lenses, but also between daily, monthly, and annual lenses. No matter which type of contact lens you choose, hygiene should be your top priority. A new type of lens is the overnight lens, which you wear only at night and then go without any corrective aids during the day.

Preventing Myopia

There’s little you can do to prevent it. However, you should have regular eye exams. Patients who suffer from nearsightedness are more susceptible to damage to the cornea. This is especially true for contact lens wearers. They should make sure to have their retinas checked regularly. Eye exercises cannot correct or prevent nearsightedness.

Information on Farsightedness

When it comes to farsightedness (hyperopia), experts distinguish between axial and refractive hyperopia. Unlike with nearsightedness, those affected see clearly at a distance but perceive nearby objects only blurrily.

Axial hyperopia is the most common form of farsightedness. In this condition, the eye—and thus the distance between the cornea and the retina—is too short. In refractive hyperopia, on the other hand, the lens’s refractive power is insufficient for sharp vision.

In both forms, the focal point of the incoming light rays lies behind the retina. If the axial length is shortened by just one millimeter, this already results in a change of +3 diopters. Axial hyperopia is present from birth in most cases.

Farsightedness can also affect children and adolescents, although they are usually quite good at compensating for the visual impairment. However, the extra strain on the eyes can lead to side effects such as eye pain or headaches.

Farsightedness often develops with age and occurs either on its own or in combination with presbyopia. Nearly everyone over the age of 45 suffers from farsightedness and requires appropriate corrective lenses. However, it generally does not worsen with age. Only presbyopia tends to set in earlier in patients with hyperopia.

Symptoms of Farsightedness

The symptoms of farsightedness are usually more pronounced in older adults than in children and adolescents. Those affected can no longer see nearby objects clearly, which becomes noticeable, for example, when reading magazines and books.

Because the eye has to work harder with farsightedness, those affected usually experience eye and headaches and tire quickly.

Diagnosis and Treatment of Farsightedness

To diagnose this refractive error, the optometrist or doctor must first determine the eye’s refractive power. This examination quickly reveals the diopter value the patient requires. In cases of farsightedness, the diopter value is always positive (e.g., +1.5).

All treatment methods aim to correct existing refractive errors. Both glasses and contact lenses are frequently used for this purpose. However, contact lenses often cause burning or dry eyes and require very careful maintenance. Contact lenses and appropriate care products do, however, involve costs.

For patients who suffer from both farsightedness and nearsightedness, so-called progressive lenses are suitable. In this case, the lenses are divided into different zones. Looking through the lower half corrects farsightedness, while looking through the upper half corrects nearsightedness. In the past, patients with multiple refractive errors needed a separate pair of glasses for each condition. Thanks to progressive lenses, this is now a thing of the past.

Farsightedness can also often be corrected with laser surgery. However, the surgery is often not as successful for farsightedness as it is for nearsightedness. The risks and side effects are equally low. Corneal scarring and overcorrection or undercorrection of farsightedness are the most common surgical risks.

The surgery is an option for patients with up to four diopters of hyperopia. For higher diopter values, the implantation of an artificial lens is possible. This procedure is very popular and can be performed on an outpatient basis at a doctor’s office. The cost of LASIK surgery ranges from about 1,000 to 3,000 euros per eye. Since this is a purely cosmetic procedure, health insurance plans cover the cost only in exceptional cases.

Prevention of Farsightedness

It is not possible to prevent this refractive error. However, for children with farsightedness, it is important to correct the condition early to prevent esotropia (crossed eyes).

Information on Astigmatism

Astigmatism is a refractive error—similar to nearsightedness and farsightedness—that occurs less frequently. It can affect one or both eyes.

Patients with astigmatism may experience blurred vision at both near and far distances. The term “astigmatism” comes from the fact that those affected perceive a point as a blurred line or “rod.”

In people with astigmatism, the curvature of the cornea deviates from its natural shape. A normal cornea is uniformly curved (similar to a sphere). Astigmatism results in areas of the cornea that are curved to varying degrees, which negatively affects the refractive power.

A distinction is made between regular and irregular astigmatism. In most cases, astigmatism is congenital, although scarring resulting from corneal injuries can also be a cause.

Healthy eye (top) and eye with astigmatism (bottom). The abnormal curvature distorts the light and prevents it from being focused correctly at the focal point. The image appears blurry

Symptoms of Astigmatism

People with mild astigmatism usually do not notice it.

Blurred vision is often accompanied by eye pain and headaches caused by eye strain.

Diagnosis and Treatment

An ophthalmometer can be used to precisely determine the curvature and radius of curvature in every plane. Here, too, the diopter value indicates the severity of the condition.

Regular astigmatism can be corrected with glasses or rigid gas-permeable contact lenses. If the cornea is severely damaged, surgical corneal replacement is necessary.

Laser surgery can correct the condition in many cases. However, the prognosis for success becomes more challenging the more severely the cornea is curved. If the angle between the cornea’s maximum and minimum refractive planes exceeds 90°, glasses are no longer effective. In such cases, special contact lenses or a corneal transplant may be considered.

Prevention

Astigmatism is a refractive error that cannot be prevented. Parents should have their children examined by an ophthalmologist as early as possible to rule out future refractive errors.