Contact lenses are thin lenses placed directly on the cornea to correct refractive errors like nearsightedness, farsightedness, and astigmatism, similar to eyeglasses. Beyond vision correction, many choose contact lenses for their aesthetic appeal, convenience during physical activity, and an unrestricted field of vision compared to eyeglasses.

According to Master of Science, Doctor Phung Van Thanh from the High-Tech Eye Center at Tam Anh General Hospital Hanoi, contact lenses are not just one type but encompass several distinct categories.

Soft contact lenses

These are the most widely used type today, made from flexible materials like hydrogel or silicone hydrogel. They allow oxygen to pass through the cornea, providing a comfortable feel and easy adaptation. Within this group, lenses are categorized by their wear schedule:

Daily disposable contact lenses are worn for one day and discarded after removal. This type helps reduce the risk of biological deposit buildup and infection compared to multi-day lenses. They are suitable for new users, infrequent wearers, or those with sensitive eyes. However, the cost can be higher if used daily.

Scheduled replacement lenses (bi-weekly or monthly) offer a more cost-effective option. Users must remove the lenses daily, clean and store them properly, and replace them according to recommended schedules. Exceeding the wear period or improper care can increase the risk of eye irritation and keratitis.

Extended wear soft lenses are designed with higher oxygen permeability and can be worn overnight under a doctor's prescription. However, wearing lenses during sleep can increase the risk of keratitis due to reduced oxygen exchange and bacterial growth, requiring professional monitoring.

Doctor Thanh examines a young man's eyes. Photo: Tam Anh General Hospital

Doctor Thanh examines a young man's eyes. Photo: Tam Anh General Hospital

Rigid gas permeable lenses (RGP)

RGP lenses are small-diameter, rigid contact lenses that maintain a stable shape on the cornea. They are suitable for individuals with high astigmatism, irregular corneas, or keratoconus. Compared to soft lenses, RGP lenses provide sharper and more stable vision, accumulate fewer protein deposits, and offer high durability, typically lasting one-two years. Users may need a few days to a few weeks to adapt and must adhere to regular cleaning and follow-up appointments.

Ortho-K

Ortho-K refers to rigid gas permeable lenses worn during sleep. They temporarily reshape the cornea to provide clear vision during the day without the need for eyeglasses. This method is also used to control myopia progression in children. Its effectiveness is maintained only with consistent nightly wear; if stopped, the cornea will revert to its original state. Ortho-K involves high costs, a complex fitting process, and requires specialized monitoring.

Specialized contact lenses

Beyond the common types, several specialized contact lenses are prescribed for specific conditions:

Hybrid lenses combine a rigid center for sharp vision with a soft skirt for increased comfort. They are often used for individuals with high astigmatism or those who have difficulty adapting to RGP lenses.

Scleral lenses have a large diameter, resting on the sclera instead of the cornea, creating a protective fluid reservoir over the eye's surface. This type is suitable for individuals with severe dry eyes, corneal deformities, or those who have undergone previous corneal surgery. These specialized lenses require in-depth fitting and monitoring.

Doctor Thanh recommends that anyone considering contact lenses undergo examination, fitting, and monitoring by an ophthalmologist, rather than purchasing and using them independently. Users must strictly adhere to hygiene instructions, replace lenses on time, and avoid sleeping overnight with types not designed for this purpose. Should signs such as red eyes, pain, excessive tearing, or blurred vision appear, users must stop wearing the lenses and seek an immediate eye examination.

Ly Nguyen