Description

ABOUT CONTACT LENS

Today, contact lenses are the preferred solution for many people because of the esthetic appearance, confidence and freedom that they offer. Their convenience and variety has made contact lenses increasingly popular.

Contact lenses are used to correct visual disorders, change the eye color or treat corneal diseases.

Contact lenses have come a long way from the glass-blown lenses of the 1800s which completely covered the pupil to our day’s thin, high technology, plastic corneal lenses. Today, there is a great variety of lenses and lens materials available to modern lens wearers for different areas of use.

To select the correct contact lens for the eye, an ophthalmologist specialized in contact lenses examines the eyes. The type, diopter, base curve and diameter of the lens to be used are determined in the examination. To confirm suitability, lenses with the closest diopter values possible are placed. The movement, stability and position of the lens is checked.

Criteria for Well-Fitting Contact Lenses 

Contact lenses are designed to stay on the cornea. Essentially, they remain in place by adhering to the lacrimal layer that covers the ocular surface and, to some degree, with pressure from the eyelids.

As the person blinks, eyelids slide over the contact lens surface, causing it to move slightly. This movement ensures that tears provide the necessary lubrication and helps to wash away any debris.

If the lens is too tight, it doesn’t move at all. This may lead to sensitivity in the eye. The user may feel comfortable at first but visual acuity is poor. In the long term, complications may arise.

If the lens is too loose, it moves excessively. The lower eyelid feels the lens too much. Vision becomes blurred when the person blinks. The lens moves off-center. The edges of the lens may bend.

• A good-fitting lens is well-centered and covers the cornea.

• The lens should move lightly for lacrimal circulation. It should be able to move 1 mm vertically in the push-up test and after blinking.

• The user should have clear vision, be comfortable and not feel the presence of the lens.

• Vision should not change after blinking.

• The edge line should not create pressure on the eye.

• Sleeping and swimming (either in a pool or in the sea) with contact lenses on should be avoided.

• If redness or a sensation of stinging occurs in the eyes while wearing contact lenses, the lenses should be taken off immediately and a doctor should be consulted.

Physical Properties of Lenses

Back surface: The part of the lens that contacts the cornea.

Front surface: The part of the lens that has no contact with the cornea. It is curved to modify the refraction of light to correct the refractive error.

Base curve: For a contact lens to be comfortable, its back surface which contacts the eye should be compatible with the front surface of the cornea and have a similar curvature. The base curve is the back central optic radius. Since it is the curve that determines the fitting of the lens in the eye, it is one of the most important parameters. If the lens is too tight, the base curve should be increased; if too loose, it should be decreased.

A higher base curve is FLAT. A lower base curve is STEEP.

Diameter: It’s the distance, measured in millimeters at the center, from one edge of the contact lens to the other edge. The diameter affects the lens fit. This value is 13.5 / 14.5 mm for soft lenses and 7 / mm for rigid lenses.

Advantages of Contact Lenses

• They provide a wider field of view than glasses.

• There are no frames to block peripheral vision.

• Optic correction characteristics are the same at all directions of gaze.

• Depth perception is better than glasses.

• They provide a natural appearance.

• Difficulties experienced with glasses such as getting wet, fogging up or discomfort on the nose and ears are avoided.

• Even people with no refractive errors (emmetropic people) can use color contact lenses (cosmetic artificial pupils) to change their eye color and have a more attractive appearance.

• They are practical in dynamic activities like sports.

• They are ideal for athletes, make-up artists, photographers, entertainment industry professionals, people working outdoors or those using devices like microscopes, telescopes etc. as part of their job.

TYPES OF CONTACT LENS

These are the most comfortable lenses and easiest to get used to.

Since they have a larger optical field, they provide a wider field of view. They are the lens group with the highest number of users thanks to high oxygen permeability.

• Replacement schedule contact lenses (monthly disposable)

• Daily lenses

• Toric lenses (for astigmatism)

• Lenses for near and distant vision

• Overnight wear contact lenses

• Aphakic lenses (pediatric)

• High-diopter and extended wear lenses

Spherical Contact Lenses 

Soft contact lenses for the correction of spherical refractive errors without astigmatism.

Toric Contact Lenses

Soft contact lenses that correct astigmatic refractive errors.

Multifocal Contact Lenses

Soft contact lenses which correct presbyopia, age-related loss of far vision which develops after the age of 40, and provide both near and far vision are called multifocal contact lenses.

Gas-Permeable Lenses (Rigid lenses)

Rigid lenses offer high oxygen permeability in addition to optical quality and durability. They provide the best results in the correction of corneal astigmatism and keratoconus, i.e. people with coning of the cornea.

Hybrid Contact Lenses

These lenses are used in keratoconus, an eye disease in which the clear corneal layer in front of the eye becomes thinner and bulges forward. A rigid lens material is used for the optics, i.e. center, of the lens while a soft lens material is used for the haptics, i.e. the peripheral part. 

Keratoconus patients often have high astigmatism so adequate vision cannot be achieved with eye glasses and soft contact lenses. Therefore, clear vision is achieved with gas permeable rigid contact lenses in these patients. However, adjustment to these lenses is difficult and not every patient can use them.  Hybrid contact lenses have a rigid center and a soft periphery. Patients can have a more comfortable and clear vision with hybrid contact lenses.

Color Contact Lenses

It is possible to have natural, stunning looks with color lenses. For eyes with refractive errors, color lenses can not only correct the refractive error, but also give the person their choice of eye color.

Chromagen Lenses

Chromagen lenses are unique products designed to help people who have color deficiency and difficulty in reading. Chromagen haploscopic filters are specially chromized and can be worn as glasses or contact lenses. These have been developed for people with color blindness and trials have demonstrated a success rate of 97%.

How Does Chromagen Work?

Chromagen haploscopic lenses change the level of each color going into the non-dominant eye and, in some cases, both the dominant and non-dominant eye, enabling enhanced color perception and color discrimination. For many people, developments in color perception and discrimination can be dramatic. The brightness of each color is strongly enhanced, including the colors perceived correctly.

Purposes of Chromagen Lenses:

• Enhancing overall color perception

• Achieving clearer and brighter color vision

• Discriminating between color tones

• Naming colors

• Improving safety (e.g. traffic and brake lights)

• Increasing visual capacity for color vision tests

These lenses are not effective in patients whose color vision is disrupted later due to retinal or optic nerve disorders.

Therapeutic Contact Lenses

Therapeutic contact lenses are used to improve epithelial healing in the cornea, prevent epithelial erosion or control the pain felt in the corneal surface.

Prosthetic Contact Lenses

If one eye has a different color than the other, you can have your ideal eye color with prosthetic lenses. A soft lens can be tinted any color that you want in order to eliminate the difference between the eyes.

USING CONTACT LENSES

How to Put Your Lenses on 

• Remove the lens from the package.

• Make sure that the lens isn’t inside out; if it is, turn it the right way round. (The edges should be upward)

• Using the middle finger of the left hand, raise your upper eyelid towards your eyebrow.

• Put the lens on the index finger of the right hand and, using the middle finger of your right hand, pull your lower eyelid down. Then, with your index finger, place the lens gently in the center of your eye.

• Keep this posture and look down to make sure that the lens is properly in place. Release your eyelids slowly.

• Repeat the same steps for the left lens.

How to Take Your Lenses off

• Wash and dry your hands thoroughly.

• Look upwards. Use your left hand to raise your upper eyelid, hold your lower eyelid in a fixed position with the middle finger of your right hand and put your index finger on the lower edge of the lens.

• Using your index finger, move the lens downwards from the colored part of your eye and gently squeeze it between your thumb and index finger to take it out of your eye.

• Avoid using your nails.

Lens Care and Cleaning

• First stages of lens use

• Keep your lens care materials within easy reach.

• Work on a clean, flat surface.

• Wash your hands with a lanolin-free soap and rinse well before handling the lenses.

• Always start cleaning with the same lens to avoid mixing them up (left/right).

Cleaning

• Put the lens into your palm.

• Apply a few drops of solution onto the lens.

• Rub both sides of the lens lightly by moving your index finger back and forth (without using your nails).

• By cleaning your lenses every time you take them off, you lift the deposit layer forming on them.

Rinsing

• After cleaning the lens, apply solution until it is rinsed.

• By rinsing the lenses every time you clean them, you make sure that the deposit and dust layer scraped off the lenses during cleaning is washed away.

Disinfection

• Put the lenses into the lens holder.

• Make sure that the lenses are well submerged in the solution.

• Close the case cover tightly.

• Keep the lenses in the case for at least four hours or overnight.

• By disinfecting your lenses every time you take them off, you make sure that microorganisms causing irritation or infection are destroyed.