Contact Lenses

What Is a Contact Lens?

We have 3 alternatives for correcting vision disorders: eyeglasses, contact lenses, and laser surgery. Contact lenses are soft or rigid optical devices placed on the surface of the eye.

What Are the Types of Contact Lenses?

Contact lenses are mainly divided into 2 classes: soft lenses and rigid lenses.

Soft Contact Lenses: These are the most commonly used lenses in the world. They are generally used to correct distance vision problems such as myopia, hyperopia, and astigmatism. Soft lenses used to correct the inability to see near objects (presbyopia) are also available.

Rigid Contact Lenses: In corneal irregularities such as keratoconus and corneal scarring, soft lenses are not sufficient. In these conditions, rigid lenses provide better vision. However, prescribing, adapting to, and using rigid lenses is more difficult than with soft lenses. For this reason, the physician's experience is very important in fitting the right rigid lens. Types of rigid lenses include corneal rigid lenses, hybrid lenses, and scleral lenses.

What Are the Properties of Contact Lenses (Diameter, Oxygen Permeability, etc.)?

In addition to power, contact lenses also have properties such as diameter, size, water content, oxygen permeability, and rigidity (modulus).

Lens Power: Lens power and eyeglass power are close to each other up to 4 diopters. Beyond 4 diopters, however, lens power begins to differ from eyeglass power. For astigmatism lenses, the cylinder power starts at 0.75 and continues up to 2.75.

Lens Diameter / Size: The most important parameter considered when choosing the right lens for a person is the lens's diameter and size. These parameters are very important in determining whether the lens fits the eye tightly or loosely. Lens diameter and size vary between brands.

Water Content: Water content greatly affects the comfort of wearing the lens. If a person has dry eye, or works at a computer, the lens's water content becomes even more important.

Oxygen Permeability: When choosing a soft lens, the first thing that comes to our patients' minds is oxygen permeability. However, nearly all of today's soft lenses are made of silicone hydrogel and have sufficient oxygen permeability.

Rigidity (Modulus): While a higher rigidity makes the lens easier to handle, insert, and remove, it can negatively affect comfort.

Daily Lenses or Monthly Lenses?

The main lens wear schedules are:

Daily Wear, Monthly Replacement: The person puts the lens in each morning and removes it in the evening, placing it in solution. At the end of the first month, the lens is discarded.

Weekly Wear, Monthly Replacement: The person wears the lens for 6 days a week. At the end of the sixth day, the lens is removed and placed in solution for 1 day. It is worn again with the new week. At the end of the first month, the lens is discarded.

Continuous Monthly Wear: The person puts the lens in and does not remove it at all for a month. At the end of the first month, the lens is removed and discarded.

Daily Disposable: The lens put in each morning is discarded that evening. A new lens is worn every day.

Although many lenses are approved for weekly and monthly wear, our recommendation is the daily disposable or daily wear/monthly replacement schedule. Nearly all scientific studies have shown that lens-related problems occur far less often with these wear schedules. Sleeping with contact lenses in is strongly discouraged.

How Is a Contact Lens Prescription Written?

Unfortunately, many contact lens wearers buy lenses based solely on their eyeglass prescription. However, as mentioned above, every lens has different properties. Moreover, each person's eye structure, working conditions, and expectations differ. For this reason, a detailed exam and a lens trial fitting must always be done before purchasing lenses.

First, the appropriate lens wear schedule is determined by discussing topics with the patient such as the environments they spend time in, occupation, hobbies, whether they play sports, and expectations. A detailed exam is then performed, and the lenses that might be suitable for the patient are determined, along with trial lenses. For this reason, the more trial lens sets a clinic has, the greater the likelihood of finding the right lens for the patient. Trial lenses are placed on the patient's eyes, and the patient waits 20 to 30 minutes. The patient's comfort and the lens's position, movement, and fit on the eye are then assessed. For astigmatism lenses, it is checked whether the lens settles at the correct axis. Finally, the power of the lens deemed suitable is fine-tuned.

What Rules Should Be Followed When Wearing Contact Lenses?

For hyperopia to cause symptoms, the eye's accommodation mechanism must fail to compensate for it. If the accommodation mechanism cannot compensate for the hyperopia, the following may occur:

• Contact lens wearers should pay great attention to hand hygiene. Fingernails should be kept short if possible.
• Do not spend time in dusty environments while wearing lenses.
• Do not shower, swim in a pool, or swim in the sea while wearing lenses.
• Lenses must always be removed before sleeping.
• Makeup should be applied after inserting lenses, and removed after taking the lenses out.
• Do not deviate from the wear schedule recommended by your doctor.
• Switch to a new lens at least once a month, and never use torn lenses.
• The solution in the lens case should be changed every day. The lens case itself should be replaced once a month, along with the lenses.
• Lenses must never be cleaned with tap water, isotonic saline, or distilled water.
• Never use someone else's lenses, even just to try them.
• Hands must always be washed thoroughly and dried before inserting or removing lenses.
• The lens should not come into contact with the eyelashes while inserting or removing it.
• If you experience stinging, redness, blurred vision, discharge, light sensitivity, or itching in your eyes, be sure to see your doctor.