Recent advancements in contact lenses have led to the introduction of a new generation of contact lenses. These lenses are made in monthly disposable, multifocal, toric, and UV contact lenses. There are also other contact lenses that change the shape of the cornea and correct the person’s vision without surgery, which are called orthokratology or CRT. Usually, this type of contact lenses is used overnight; during this time, the shape of the cornea is changed, and the person’s vision will improve throughout the day without using contact lenses.
Colored Contact Lenses
At Tehran Noor Eye Hospitalcolored contact lenses are divided into the following groups:
- Visibility tinted lenses
- Color enhancement contact lenses
- Opaque contact lenses
- Light-filtering contact lenses
Colored lenses can only be cosmetically applied, as well as to correct astigmatism, presbyopia or refractive errors.
Visibility Tinted Lenses
A light blue or green color is added to the contact lenses to be detected when the lenses are inserted or removed or when they fall to the ground. Because the color is very light, it does not affect the natural color of the eye.
Color Enhancement Contact Lenses
The transparent lenses are darker than the visibility tinted lenses and intensify your natural eye color. This type of lenses is more suitable for people who have bright eyes and want to sharpen their eyes.
Opaque Contact Lenses
Colors of these lenses, which include a wide range of colors, change significantly the natural color of the eye. Companies that make tinted contact lenses do their best to make these lenses look like irises, even creating a series of colored lines and shapes on the lenses to make them look more natural. The center of these contact lenses, which is the pupil's location, is transparent so you can look beyond it.
Light-Filtering Contact Lenses
These lenses are newly manufactured and are mostly used in sports fields to exacerbate certain colors, for example, the yellow filter makes tennis or golf balls more specific in the field and easier to target.
Continuous Wear Contact Lenses
Continuous contact lenses are lenses that can be used at bedtime. Some of these contact lenses are only usable daily and should be taken at bedtime. Continuous lenses bring more oxygen to the cornea, most of them can be used for up to 7 days and discarded after 7 days.
There are two types of contact lenses that can last for up to 30 days: CIBA night and day contact lenses and Bausch and Lomb pure vision contact lenses. However, the contact lenses that are worn overnight increase the risk of eye infection than daily contact lenses, because dangerous organisms that enter the eyes through the fingers, eyelids, or lens solutions come under contact lenses and grow better overnight and increase the risk of corneal infection. Of course, because 30-day or 7-day interchangeable contact lenses do not require contact lens solutions, they reduce the amount of microorganisms that enter the eye and don't increase the risk of infection. 30-day contact lenses, that are now available, are made of highly penetrating oxygen-permeable silicon hydrogels.
For example, the "night and day" lenses allow 6 times more oxygen to pass through the lens to the cornea than regular contact lenses. It has been shown that smoking is an important risk factor for continuous wear contact lenses complications.
To reduce the risk of corneal infection through continuous contact lenses, the lenses can not always be worn. For example remove the lenses before sleeping and only sleep with them when you are napping during the day or when you are on vacation and you have to sleep while you wear contact lenses. Of course in this situation the risk of using the lens solution and lens case is added.
Be sure to remove the lenses quickly and contact your ophthalmologist immediately when you feel uncomfortable or burned or discolored.
-Rigid Gas Permeable Lenses (RGP)
Rigid contact lenses, that are oxygen permeability, are different from the old- fashioned hard lenses of previous decades. Hard contact lenses were initially made of PMMA, causing discomfort when used because they were not permeable to oxygen. Gas permeable lenses became available and common in the mid-1980s. Rigid gas permeable lenses made of silicone-containing compounds are more flexible than PMMA and transmit more oxygen to the cornea, even more than do traditional soft contact lenses.
- Gas Permeable Lenses (GP)
GP lenses provide sharper vision, last longer, are more resistance to sediments, easier to clean, and because of their longer durability, they are cheaper than lenses than soft lenses. But it should be said that soft lenses are more comfortable than gas permeable lenses which need to get used to them.