The contact lens is a device created to correct vision by light refraction to the retina. The wearing of contact lenses is increasing, not only for eye refraction but also often worn for cosmetic reasons. There are two types of contact lenses based on the basic material: soft contact lenses (soft lenses) and hard contact lenses (hard lenses). These material differences make different advantages and disadvantages of each type. To choose which is appropriate, the patient must know each contact lens's details that will be worn.

Which type of contact lenses are best?

A. Soft Contact Lenses 

The basic materials of soft contact lenses are hydrogel, HEMA (hydroxy methylmethacrylate), and vinyl copolymer. Soft contact lenses have hydrophilic properties, meaning these contact lenses can absorb water so that the consistency is soft and more comfortable to use. Based on its thinness, soft contact lenses are divided into two types:

a. Thin or ultrathin contact lenses.
These contact lenses tend to be easily damaged due to the contact lenses' thinness so that their use becomes more. This lens is easily wrinkled, so it is not very easy during the initial installation.

b. Silicone hydrogel contact lenses.
This contact lens is suitable for long-term use. Early contact lens users were encouraged to use this because the material was slightly harder than thin contact lenses. Has the nature of the material that is not easily torn. However, these contact lenses tend to be more expensive, and studies say there is an increased incidence of Contact lens-induced papillary conjunctivitis (CLIPC).

The advantages of soft contact lenses are:

- Require a relatively short adaptation.
- Comfortable to wear anywhere because it is not too sensitive to dusty air or foreign objects that enter the eye.
- contact lenses in various colors and sizes.
- Available in monofocal and bifocal lenses.

B. Hard Contact Lenses

Hard contact lenses are made from PMMA (polymethyl methacrylate). PMMA has excellent optical properties and is not easily broken. However, PMMA does not have oxygen permeability, so it is often felt uncomfortable when used. One way to overcome this is to increase the frequency of blinking so that oxygen is carried by the tear component and enters the corneal epithelium.

Because of the discomfort, hard contact lenses are rarely used and switch to Rigid gas-permeable (RGP) contact lenses. Today's RGP is often touted as a hard contact lens because the material tends to be harder than soft contact lenses.

C. Rigid gas-permeable (RGP) contact lenses.

RGP has a variety of diopters sizes and can correct higher minuses compared to soft contact lenses. For routine use, the RGP must be measured for the corneal curve, the correct refraction size, and identification of corneal irregularity, after which contact lens fitting is performed. When contact lens fitting, the doctor will check several things such as apical alignment, eyelid arch to the cornea, centering center, and tolerated diameter. After a good examination result, the patient will be tried to use at least 14 hours in 1 day. If there is no bad response, then RGP can be used as a contact lens that can be worn every day. RGP has oxygen permeability 5 times higher than soft contact lenses, thereby reducing the risk of epitheliopathy in the cornea.

RGP is divided based on material, including:

1. Cellulose acetate butyrate
2. Silicon acrylates
3. Fluorosilicon acrylates
4. Hydrophilic rigid gas-permeable

The advantages of RGP contact lenses compared to soft contact lenses are:

- The quality of vision is brighter and sharper
- Can correct astigmatism from small to large sizes
- Can correct irregular astigmatism.
- Easier to handle because of harder material
- Can be used in cases of dry eyes and corneal surface abnormalities
Treatment tends to be easier

Each contact lens has its advantages so that each patient may have different indications.

With all the advantages and disadvantages, soft and hard contact lenses have the following complications:

Serious eye infections can occur if contact lens care instructions are not used properly. Cleaning and removing contact lenses and their improper storage can cause eye infections.

As many as 40% -90% of contact lens users do not correctly use contact lenses. Corneal infection (keratitis) is an infection that causes pain in the eye closely related to the inaccuracy in the use of contact lenses.

Long-term and high-frequency wearing soft contact lenses can cause dry eyes, allergic reactions, and inflammation in the eye, so that regular eye check-ups are recommended.

By knowing the advantages, disadvantages, comparisons, indications, and side effects of use, it is hoped that doctors will be able to provide an excellent education to help patients make the right choice of contact lenses as needed.

Source: Alomedika
Writer: Dr. Intan

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