Contact lens intolerance is a frustrating reality for many long-term wearers, characterized by symptoms like persistent dryness, irritation, and redness. This condition is not a single diagnosis but rather a sign that the delicate balance of the eye’s surface has been disrupted. Understanding the underlying physical and physiological changes is the first step toward finding a lasting solution, which often requires attention beyond simply changing a lens brand.
The Most Common Causes: Dryness and Overwear
The primary reason for contact lens intolerance is a chronic imbalance in the tear film, known as dry eye syndrome. The tear film consists of oil, water, and mucus layers, which are essential for lubricating the eye and ensuring comfortable lens wear. When tear quality is poor or production is inadequate, the lens can become desiccated, leading to friction against the eye’s surface and a gritty, burning sensation.
A significant contributing factor is lens overwear, which involves wearing lenses longer than prescribed or sleeping in them. This practice restricts the cornea’s access to atmospheric oxygen, leading to oxygen deprivation, or hypoxia. Chronic hypoxia forces cells to respire anaerobically, producing lactic acid that causes the corneal tissue to swell (corneal edema). This swelling alters the lens fit and causes blurred vision, making comfortable wear impossible.
Another common culprit is the inevitable build-up of deposits on the lens material, even with diligent cleaning. Tears contain proteins, lipids, and other substances that adhere to the lens surface over time. These deposits reduce the optical clarity of the lens and act as a source of chronic irritation or an allergic trigger for the eyelid tissue. The continuous presence of these foreign materials can initiate inflammatory responses that affect the eyes’ ability to tolerate lenses.
Inflammatory and Structural Eye Changes
Chronic irritation from contact lens deposits and friction can trigger Giant Papillary Conjunctivitis (GPC). GPC is characterized by the development of large, dome-shaped bumps, or papillae, on the inner surface of the upper eyelid. These enlarged papillae rub against the lens with every blink, creating severe discomfort, excessive mucus discharge, and lens instability.
Chronic oxygen deprivation to the cornea can also lead to a serious structural change known as corneal neovascularization. The cornea is normally avascular, receiving its oxygen directly from the air. In response to long-term oxygen starvation from overworn lenses, the body attempts to compensate by growing new, fragile blood vessels from the limbus into the clear corneal tissue. The presence of these vessels can threaten the cornea’s transparency and is a definitive reason for an eye care professional to mandate stopping contact lens use.
Long-term lens use, particularly with older or less oxygen-permeable materials, can also lead to chronic corneal edema, or swelling, that affects the corneal structure. This swelling results from the endothelium, the inner layer of the cornea, being unable to pump out fluid effectively due to oxygen deprivation. Chronic edema can cause structural changes that make the proper fitting of any contact lens impossible, further contributing to intolerance.
Systemic and Medication-Related Factors
The body’s internal chemistry plays a major part in contact lens comfort, especially concerning hormonal shifts. Fluctuations in hormones like estrogen and progesterone, common during menopause, pregnancy, or with the use of hormonal contraceptives, can drastically alter the volume and composition of the tear film. Changes in androgen levels can affect the oil-producing meibomian glands along the eyelid margin, leading to increased tear evaporation and dry eyes.
Many common prescription and over-the-counter medications have a drying effect on the body, directly contributing to intolerance. Medications with anticholinergic properties, such as antihistamines, decongestants, and certain antidepressants, reduce tear production by blocking nerve signals. Other classes of drugs, including diuretics for blood pressure and isotretinoin for acne, can reduce the aqueous and oil components of the tear film, making the eye surface inhospitable for lens wear.
Age itself is an independent factor, as tear production naturally decreases after the age of 50 and the quality of the tear film becomes less stable. This natural decline, compounded by years of contact lens wear, can tip the balance toward permanent intolerance. The development of presbyopia, the age-related loss of near focusing ability, also necessitates different lens designs, which can introduce new fitting challenges and comfort issues.
Managing Intolerance and Vision Alternatives
If standard contact lenses are no longer tolerated, specialized lens options can often restore comfortable wear. Specialty lenses, such as rigid gas permeable (RGP) lenses or scleral lenses, are designed to vault over the sensitive corneal surface, resting instead on the sclera. Scleral lenses are custom-fitted and filled with a saline solution reservoir before insertion. This provides a continuous bath of moisture to the cornea, making them suitable even for severe dry eye or irregular corneas.
For those seeking to eliminate the need for contact lenses entirely, surgical alternatives offer a permanent solution. Refractive surgeries like Laser-Assisted In Situ Keratomileusis (LASIK) and Photorefractive Keratectomy (PRK) reshape the cornea to correct vision. PRK is often a better option for individuals with thinner corneas or chronic dry eye, as it does not involve creating a corneal flap like LASIK, which can temporarily worsen dryness.
The most immediate and safe alternative is a return to wearing glasses, which allows the eyes to rest and recover from any underlying inflammation or structural change. Consulting an eye care professional is necessary to identify the specific cause of intolerance. Treatment may involve addressing GPC with topical medications or managing chronic dry eye with prescription drops. Addressing the root problem, rather than simply trying a new lens, is the most effective path toward long-term eye health.