Night contacts, technically known as Orthokeratology or Ortho-K, are specialized gas-permeable lenses worn exclusively while sleeping. These custom-designed devices gently and temporarily reshape the front surface of the eye, the cornea, to correct refractive errors. Ortho-K lenses allow the wearer to see clearly without any corrective eyewear after the lenses are removed in the morning. This non-surgical approach offers visual correction distinct from conventional glasses or daytime lenses.
How Night Contacts Reshape Vision
The mechanism behind night contacts relies on the cornea’s natural elasticity and a precisely engineered lens design known as reverse geometry. The lens rests on the tear film, creating a hydraulic force due to a pressure gradient between the lens and the corneal surface. This strategically redistributes the tear film, guiding the temporary change in corneal shape.
This gentle force causes a controlled migration and redistribution of cells in the outermost layer of the cornea, called the epithelium. Epithelial cells in the center of the cornea are subtly thinned, while those in the mid-periphery are thickened. This process effectively flattens the central curvature of the cornea, altering how light focuses onto the retina and providing clear vision for the rest of the day.
The effect is non-permanent and reversible because it involves only the temporary movement of soft tissue cells, not the deeper, structural layers of the eye. If lens wear is discontinued, the corneal epithelium will naturally return to its original shape, and the refractive error will reappear. This temporary correction typically lasts 16 to 24 hours, requiring consistent wear, often six to seven nights per week, to maintain visual clarity.
Determining Eligibility and Required Patient Commitment
Orthokeratology is most effective for individuals with mild to moderate nearsightedness (myopia) and a limited amount of astigmatism. The ideal prescription range for myopia correction falls between -1.00 and -6.00 Diopters (D), with astigmatism correctable up to around -1.75 D.
Children and teenagers are often considered excellent candidates because Ortho-K has been scientifically proven to slow the progression of myopia, a process called myopia control. While adults can use this treatment, the myopia control benefit is primary for younger patients.
Suitability is determined not only by prescription but also by the patient’s commitment and corneal health. Successful treatment requires high compliance, starting with wearing the lenses every night as prescribed. Consistent nightly wear ensures the cornea retains the desired shape for all-day vision.
This therapy requires adherence to a strict schedule of regular follow-up appointments to monitor the corneal reshaping process and ensure eye health. The eye care provider must continually assess the lens fit and visual outcome, particularly during the initial weeks of treatment.
Understanding the Risks and Proper Care
While Ortho-K is a safe, non-surgical vision correction method when managed correctly, the most significant risk is microbial keratitis, a serious eye infection. This complication is almost always linked to improper lens cleaning, poor hand hygiene, or exposure to contaminated water. Any contact lens worn overnight carries an elevated risk of infection compared to daily disposable lenses.
To mitigate this risk, patients must adhere to a strict care regimen. Before handling the lenses for insertion or removal, hands must be thoroughly washed with antibacterial soap and dried completely with a lint-free towel. Lenses must never be rinsed or stored in tap water, which contains microorganisms, such as Acanthamoeba, that can cause severe infections.
Lenses must only be cleaned and disinfected using the specific sterile saline and solutions recommended by the eye care professional, often involving a hydrogen peroxide system for deep disinfection. The lens storage case must also be regularly cleaned and replaced, typically every three months, to prevent the buildup of bacterial biofilms. Patients should be aware of minor, temporary side effects, such as glare or halos around lights at night, which can occur during the initial adjustment period.