Eyeglasses and contact lenses are the two most common options for vision correction. Both offer unique optical properties, and come with practical advantages, and disadvantages that may affect how they suit your lifestyle and purchase decisions.
Understanding the differences can help you make a better decision about your vision correction needs, so let’s drill down now…
Understanding vision correction
Both eyeglasses and contact lenses are used to correct refractive errors, which may be:
- Myopia (nearsightedness)
- Hyperopia (farsightedness)
- Astigmatism (irregular curvature of the cornea or lens)
- Presbyopia (age-related difficulty in focusing on near objects)
Both eyeglasses and contact lenses alter the path of light that enters the eye to focus it correctly on the retina.
Optical characteristics of eyeglasses
Lens material and design
Lens materials
Lenses can be made from various materials, including glass, plastic (CR-39), polycarbonate, and high-index plastics. Each material has different optical and physical properties, such as refractive index, weight, and durability.
Designs
Spectacle lenses come in single vision (one distance), and bifocals, trifocals, and progressive lenses for different distance and near needs.
Vertex distance
The vertex distance is the space between the back surface of the eyeglass lens and the front surface of the cornea.
The vertex distance can impact the performance of the lenses, particularly with a higher prescription. It can lead to slight magnification or minification of images and peripheral distortion.
Patients that wear glasses for distance correction often have a higher number value prescription in their glasses than they would for contacts. Those who wear glasses for reading may have a higher number value in their contacts than their glasses. The reason between the difference in your glasses and contact lenses is usually due to vertex distance.
Field of view
- The frame of the glasses can limit the field of view. Your peripheral vision may be less clear or obstructed by the frame, which can be problematic in certain sports.
- Larger eyeglass lenses can increase the field of view compared to a smaller lens, but the frame still creates a boundary. Field of view concerns may be a reason to prefer contacts.
Optical aberrations
Types
Spherical aberration, chromatic aberration, and astigmatism are more pronounced in glasses lenses due to the distance from the eye. These aberrations are what make driving at night more difficult.
Mitigation
High-quality lens material like high-index and an anti-reflective coating can reduce some of these aberrations, but some are just inherent due to the way the eye is made. The materials contact lenses are made of often induced more aberrations.
Types
Spherical aberration, chromatic aberration, and astigmatism are more pronounced in glasses lenses due to the distance from the eye. These aberrations are what make driving at night more difficult.
Mitigation
High-quality lens material like high-index and an anti-reflective coating can reduce some of these aberrations. The materials contact lenses are made of often induce more aberrations.
Prismatic effect
Prismatic effect can occur when looking through the edges of glasses lenses which causes image displacement or distortion.
The effect is more apparent in higher prescriptions and can be minimized with well-centered lenses and appropriate frame choices. Wrapped sunglasses may also induce a more prismatic effect for patients with a lot of astigmatism, which may cause difficulties.
Optical characteristics of contact lenses
Lens material and design
Materials
Soft contact lenses are either hydrogel or silicone hydrogels, which are materials that allow oxygen to reach the cornea, maintaining eye health.
Designs
Contact lenses can be soft lenses, rigid gas permeable (RGP), and hybrid varieties, with options for single vision, toric (for astigmatism), multifocal, and customized designs for specific conditions like keratoconus.
No vertex distance
Contact lenses sit directly on the cornea, eliminating the vertex distance issue and providing more natural vision correction. The direct placement on the cornea often results in better visual acuity and reduced peripheral distortion compared to glasses.
Contact lenses are often preferred by those with high prescriptions, a substantial difference in the power between the two eyes or someone with a lazy eye. Focusing up close is also more difficult through contacts lenses if you wear a prescription for distance.
Field of view
- Contact lenses move with the eye, providing a full field of vision without frame obstruction which is particularly beneficial for athletes and those with active lifestyles.
- Vision remains consistent across the entire field, without the edge effects seen in glasses.
Enhanced vision
Contact lenses move with the eye, providing a full field of vision without frame obstruction which is particularly beneficial for athletes and those with active lifestyles.
Uniform clarity
Vision remains consistent across the entire field, without the edge effects seen in glasses.
Optical aberrations
Reduced aberrations
The proximity of contact lenses to the cornea reduces spherical and chromatic aberrations, providing clearer and more consistent vision.
Higher order aberrations
Some individuals might experience different higher-order aberrations with contact lenses, which can affect night vision and contrast sensitivity.
Stability and consistency
Lens movement
Soft contact lenses fit closely to the cornea, providing stable and consistent vision. RGP lenses may offer even sharper vision due to their advanced optics and precise fit.
Environmental conditions
Contact lenses are less affected by weather conditions such as rain, fog, and temperature changes, which can fog glasses.
Accommodation
Accommodation can also be called focusing. The ciliary muscles can change the shape of the lens to focus rays of light.
Accommodation varies between glasses and contact lenses.
- If you are myopic, you must focus more through your contact lenses.
- If you are hyperopic, if you must accommodate more through glasses. As you approach 40, you may find yourself having difficulty seeing up close with your contacts, but you can read with your glasses, accommodation is the reason.
Practical considerations and individual preferences
Comfort
- Glasses are generally more comfortable from the start (depends on the prescription). It is normal to feel the edge of the contact lens the first couple of days, but the awareness should improve over time.
- Today’s contact lenses with advanced technology and materials are very comfortable for daily wear.
Convenience and maintenance
- Glasses are easy to put on and take off, requiring minimal maintenance; however, they can be heavy, prone to fogging, and need to be kept clean.
- Contact lenses require proper hygiene and regular cleaning to prevent infections. Daily disposables offer convenience with no cleaning required.
Lifestyle
- Contact lenses offer more freedom and better vision for sports and physical activities. They are unlikely to fall out or be damaged during movement.
- Glasses can convey a professional image and often reflect your personal style. They may also serve as a physical barrier against dust and debris or bodily fluids in a healthcare setting.
Cost
- Glasses generally have a higher initial cost but lower ongoing expenses.
- Contact lenses must be purchased regularly and may require cleaning solutions, which can add up over time. Daily lenses cost more initially, but do not require the ongoing purchase of solutions.
Health and safety
- Contact lenses require diligent care to avoid infections and complications such as dry eyes, keratitis, and pseudomonas.
- Some contact lenses offer UV protection, but they do not cover the entire eye. Glasses can be ordered with UV-protective coatings and sunglasses offer more comprehensive sun protection. Even if your contacts have UV protection, sunglasses are still necessary to protect the eye and lid tissue.
Are contact lenses or eyeglasses the way to go?
Both glasses and contact lenses have distinct optical characteristics that influence their suitability for different individuals and their lifestyles.
Glasses offer ease of use, lower maintenance, and may serve as a fashion accessory, while contact lenses provide a wider field of view, more natural vision correction, and may be best for those with an active lifestyle.
Ultimately, the choice between glasses and contact lenses depends on your preferences. Understanding the differences can help you better comprehend why you see differently with glasses than contact lenses. For many, a combination of both might be best, providing both flexibility and optimal vision correction depending upon the situation.
