The Safety and Limits of Wearing Contacts Non-Stop: Understanding Corneal Hypoxia and Overwear

Introduction

Contact lenses, whether colored or not, are designed for specific wearing durations to ensure the safety and comfort of the wearer. When wearing contacts continuously without removing them for long periods, corneal hypoxia and overwear can occur, leading to various ocular issues. In this article, we will explore the typical wearing schedules for different types of contact lenses and the risks associated with prolonged wear.

Understanding Corneal Hypoxia and Overwear

Corneal hypoxia, or oxygen deficiency, is a condition that arises when the cornea does not receive enough oxygen. This can lead to swelling, halo effects around lights, blurriness, dryness, and discomfort. Over time, these issues can escalate, even leading to the formation of blood vessels in the cornea (neovascularization).

What Causes Corneal Hypoxia?

Corneal hypoxia is caused by reduced oxygen flow to the cornea. The typical contact lenses, especially soft lenses, can obstruct the cornea's access to vital oxygen, particularly when worn for extended periods without removal or cleaning.

Effect of Overwear on Contact Lenses

Regular contact lens wearers should follow the manufacturer's recommendation for wearing durations. For example, colored contact lenses are designed to be worn for only up to 6-8 hours, after which they can start to overwear. Overwear can also occur with other types of lenses, and the severity can vary depending on the individual's ocular health and the type of lens.

Giving Comfortable Wearing Hours: Wearing Duration for Specific Types of Lenses

Depending on the type of contact lens and its oxygen permeability, specific wearing durations can be comfortably tolerated.

Ultra-Permeable Multifocal RGP Lenses

Ultra-permeable multifocal RGP lenses, such as Boston XO2 Essentials III, can be worn for an extended period, averaging 12-18 hours per day. While these lenses are designed for long-term wear, comfort can vary and may require adjustments for certain individuals.

Well-Fitted Soft and RGP Lenses

Well-fitted contact lenses can be worn for up to 8 hours for daily wear, 12 hours for extended wear, or even 24 hours with newer, more breathable materials. However, personal tolerance varies, and some users may experience discomfort or dryness after 6-8 hours.

Risk and Recommendations

It is crucial to follow recommended wearing schedules, especially at night, as sleeping in contacts significantly increases the risk of infections. Always consult your eye doctor regarding the appropriate wearing schedule for your specific type of lenses. Factors such as lens material, comfort, and individual ocular health should be considered when determining the optimal wear and removal times.

Types of High-Breathability Contact Lenses

Several types of contact lenses are designed to provide high levels of oxygen permeability, reducing the risk of corneal hypoxia and overwear:

Silicone hydrogel soft lenses: Acuvue Oasys, Acuvue Max CV, Biofinity, BL Ultra, Alcon Air Optix, Night and Day RGP lenses: Boston XO2, Acuity 200, Paragon HDS, Menicon Z, Fluorperm 150 High-Permeability RGP lenses: BX Acuity 200 - rated for the highest oxygen permeability

New materials and designs continue to evolve, offering safer and more comfortable options for extended wear.

Conclusion

Contact lenses are incredibly convenient, but it is vital to use them within the recommended wearing schedules to maintain eye health and prevent complications such as corneal hypoxia. Always consult your eye care professional to ensure you are using the most suitable contact lenses for your specific needs.