Types of Contact Lenses: A Comprehensive Guide

Contact lenses have dramatically revolutionized the world of optometry, offering an unprecedented level of freedom to people with vision impairments. However, with a variety of options now available in the market, choosing the right pair can be overwhelming. Let’s dive into the world of contact lenses and uncover the distinct types that cater to varying needs and lifestyles.

Soft Contact Lenses

Soft contact lenses are one of the two major types of contact lenses, the other being hard or rigid gas-permeable lenses. They are made of soft, flexible plastics that allow oxygen to pass through to the cornea, the front surface of your eye.

Here's a bit more detail about soft lenses:

Material

Soft contact lenses are usually made from hydrophilic (water-loving) plastics known as hydrogels, or specifically silicone hydrogels for some newer models. These materials are permeable to oxygen, which is necessary to maintain the health of the cornea.

Comfort

Due to their softness and flexibility, these lenses are generally considered more comfortable and are easier to adapt to than rigid gas-permeable lenses.

Types of Soft Contact Lenses

• Disposable (Monthly Wear): These lenses are removed nightly and require cleaning and disinfection. They're typically replaced on a schedule that can range from every two weeks to monthly.
• Extended Wear: These can be worn overnight, but they still need to be cleaned and disinfected weekly. Not everyone's eyes can tolerate extended wear, and there's a higher risk of eye infections.
• Disposable (Daily Wear): These are discarded nightly, so there's no need for cleaning. They're convenient but cost more than other lens types.

Gas Permeable (GP) Contact Lenses / Hard Contact Lenses

Gas Permeable (GP) contact lenses, also known as Rigid Gas Permeable (RGP) lenses and Hard contact lenses, are a type of contact lenses made from durable materials that are permeable to oxygen.

They are rigid lenses but are different from the older style of hard contact lenses which were made from a material known as PMMA (polymethyl methacrylate) that did not allow any oxygen to reach the cornea.

Here's a bit more detail about GP lenses:

Material

GP lenses are made from a type of plastic that is permeable to oxygen, which helps keep the eye's cornea healthy. The materials used in GP lenses typically include fluorine and silicone, which make the lens oxygen permeable.

Vision Quality

GP lenses often provide clearer vision than soft lenses as they maintain their shape when blinking, which can provide a more stable and consistent vision. They are particularly suitable for people with certain types of prescriptions, such as high astigmatism, or conditions like keratoconus where the cornea is irregularly shaped.

Durability

GP lenses are durable and resistant to deposit buildup. They're also less likely than soft lenses to tear.

Adaptation

GP lenses may require a longer adaptation period for new wearers, as they feel different from soft lenses. But most people eventually find them to be comfortable after an initial adjustment period.

Maintenance

Like other contact lenses, GP lenses need to be properly cleaned and stored to maintain eye health.

Types

GP lenses also come in different types such as multifocal GP lenses (to correct presbyopia) and orthokeratology lenses (designed to reshape the cornea and reduce myopia temporarily).

Overall, while GP lenses might not be as initially comfortable as soft lenses, they provide excellent vision clarity and durability, making them a good choice for many individuals. As always, a consultation with an eye care professional is recommended to decide the best type of contact lens for your personal needs.

Multifocal Contact Lenses

Multifocal contact lenses are designed to provide clear vision at all distances for people who have refractive errors and are also experiencing the normal age-related decline in near vision called presbyopia.

Presbyopia typically occurs after the age of 40 when the eye's lens hardens and can't change shape as easily as it once did. This makes it harder to read, work on a computer, and perform other close-up tasks.

Multifocal contact lenses have different power zones for near and far vision, somewhat similar to bifocal or progressive eyeglasses, allowing the wearer to see clearly at all distances.

Types of Multifocal Lenses

They are available in both soft and rigid gas permeable (GP) materials and can be used as daily wear or extended wear lenses. They also come in different designs:

• Concentric Design: These lenses have either a central circular area dedicated to one distance (near or far), with alternating rings for near and far distances radiating out from the centre.
• Aspheric Design: These lenses gradually transition from one power to another across the lens surface, similar to progressive eyeglasses.
• Segmented Design: Similar to bifocals, these lenses have a distinct flat line separating the near and far viewing zones. This design is typically only found in GP lenses.

Adaptation

Some people may require a period of adjustment when starting to use multifocal lenses, as their eyes learn to select the correct power choice within the lens.

Customisation

The lenses can be customised based on whether you prefer to use your near or far vision more. For example, you might choose the near vision for reading or other close work and the far vision for activities like driving.

 The lenses can be customised based on whether you prefer to use your near or far vision more. For example, you might choose the near vision for reading or other close work and the far vision for activities like driving.

Toric Contact Lenses

Toric contact lenses are specifically designed to correct astigmatism, a common vision condition caused by an irregularly shaped cornea or lens in your eye. People with astigmatism have an eye shape that's more like a football (elongated) rather than a perfect sphere like a basketball. This irregular shape distorts the way light enters the eye, leading to blurry or distorted vision.

Unlike standard spherical contact lenses, toric lenses have different powers in different meridians of the lens to compensate for the asymmetry of the eye's shape. They also have a mechanism to prevent the lens from rotating on your eye, ensuring that the corrective power is properly aligned.

Design

Toric lenses are designed with two powers in one lens: one to correct astigmatism, and the other to correct myopia (short-sightedness) or hyperopia (long-sightedness). They also have a design feature that enables the lenses to rotate to the proper orientation on the cornea, aligning the powers with the appropriate areas.

Materials

Toric lenses are available in both soft and rigid gas permeable (GP) forms. Soft toric lenses are very comfortable and easier to wear, while GP toric lenses provide sharper vision.

 Fit

Fitting toric lenses takes more time and requires more expertise than fitting regular spherical lenses. This is because of the additional measurements needed to align the lens correctly.

Orthokeratology (Ortho-k) Lenses

Orthokeratology, or Ortho-K, is a non-surgical procedure that involves the use of specially designed contact lenses to reshape the curvature of the cornea (the front surface of the eye) temporarily to improve vision. This procedure is mainly used to correct myopia (nearsightedness), but can also be used for hyperopia (farsightedness), astigmatism, and sometimes presbyopia (difficulty focusing on close objects).

Here are some important points about Ortho-K lenses:

Design and Material

Ortho-K lenses are made of rigid gas permeable (GP) material, and the design is customized for each individual's eyes. They are larger than standard GP lenses and are designed to apply pressure to the cornea to flatten it.

Wear Schedule

Ortho-K lenses are typically worn overnight while you sleep. They gently reshape the cornea, and when you remove them in the morning, your vision is temporarily improved, often enough to go throughout the day without glasses or contact lenses. However, the effect is not permanent, and if you stop wearing the lenses, your cornea will gradually return to its original shape, and your vision will revert to its previous prescription.

Use Cases

Ortho-K is a popular option for people who want to be glasses-free during the day but aren't good candidates for refractive surgery (like LASIK). It's also been used as a method for myopia control in children, slowing the progression of nearsightedness.

Adaptation

It may take several days or weeks to achieve the best vision correction with Ortho-K. Initially, the improvement in vision may not last for the entire day, and in some cases, supplemental glasses may be needed during this adjustment period.

Decorative (Cosmetic) Contact Lenses

Decorative or cosmetic contact lenses are designed to change the appearance or colour of your eyes. While they do not correct vision, they can drastically change your look by enhancing or completely changing your eye colour, or even giving a special effect, such as cat eyes or vampire eyes for a costume.

Types of Cosmetic Lenses

They come in a wide range of designs, from subtly enhancing the natural eye colour, completely changing it (like from brown to blue), or providing dramatic looks for occasions like Halloween or theatrical performances.

Prescription

Coloured contact lenses can be bought with or without a prescription. Meaning that you can simply buy them for cosmetic purposes without it correcting your vision, or you can get them with a prescription. Whether you are getting it with or without a prescription, an optometrist or ophthalmologist can instruct you on proper lens care.

Safety

It's crucial to remember that while they can be fun, decorative contact lenses are not toys and should be treated with the same handling care as corrective contact lenses. They must be cleaned and stored properly to prevent infection. Never share these lenses with others.

Always purchase contact lenses from a reputable source, not from unregulated outlets, like costume shops, unknown online stores, or street vendors, and only use them under the guidance of an eye care professional.

It's important to have a comprehensive eye exam and consultation with an optometrist or ophthalmologist to determine the best type of contact lenses for your eyes and lifestyle.