The five best contact lenses for dry eye
What is dry eye?
Dry eye is a commonly experienced eye condition that causes discomfort and reduced wearing time for the sufferer. It occurs when there is either insufficient quantity or quality of tears to lubricate the eye. This lubrication provides nourishment for the eye and protects the ocular surface, making tears crucial to good ocular health. If left untreated dry eye can eventually cause visual impairment and damage to the front surface of the eye.
What are the role of tears?
Tears are produced by tiny glands around the eye. In a perfectly working eye, the tears are blinked across the cornea providing multiple benefits including:
- protection from eye infection
- removal of foreign matter
- maintenance of a smooth and clear eye surface
When too many tears are produced, the eye will drain the excess into tiny ducts that sit at the corner of the inner eyelid. These drain the tears into the back of the nose for removal. This is why we often blow our nose during and after crying.
Dry eye interrupts the natural operation of tears in the eye due to an imbalance of tear production and drainage.
What causes dry eye?
There are two ways that dry eye is caused. The sufferer either doesn't produce enough tears or the quality of the tears being produced is not adequate. Tears aid in nourishment, protection and maintenance of the health of the eye. If not producing enough, or the tear quality is poor, dry eye will develop.
The actual tear film comprises of three distinct layers: oil, water, mucous. The lower mucous layer helps the tear layer stick to the eye, the middle water layer is the lubrication, and the outer oily layer acts as a seal on the tear layer to reduce evaporation.
There are two categories of dry eye;
1. Insufficient tear volume. A reduced volume of tears may occur for a variety of reasons including age, side effects from medicines (such as fluid tablets or diuretics, antihistamines, some blood pressure medications and anxiety medications) medical conditions such as auto-immune diseases, hormonal changes, and exposure to adverse environmental conditions such as dry climates, wind and smoke which may cause the tears to evaporate more rapidly. A lack of adequate fluid intake will also contribute to ocular dryness.
2. Inadequate quality of tears. If one of the distinct layers in a tear film is deficient, the tears may not spread evenly across the eye or may evaporate more quickly.
What are the symptoms of dry eye?
- gritty, scratchy sensation
- burning eyes
- foreign body sensation
- blurry, filmy vision
- excessive watering of eye
Dry eye can cause significant discomfort, and if left untreated can eventually cause long term damage to the ocular surface.
What is the treatment for dry eye?
Treatments for dry eye include:
1. Increase tears - Eye drops with artificial tears can be used to lubricate the eye. These lubricants act to replace the reduced tear quantity or quality caused by dry eye. Contact lens wearers should use specific contact lens solutions such as "Blink n Clean" drops for both improved ocular lubrication and reducing lens surface deposits. preservative free drops are always preferable to minimise the exposure of the ocular surface to preservatives.
2. Safeguard tears - Punctal occlusion is a small procedure that either temporarily or permanently closes the tear ducts that drain away tears. By closing the drain, the naturally produced tears will remain in the eyes longer. For temporary closure, ducts are blocked using a silicone plug that looks similar to a mushroom. For permanent closure, a minor operation is required.
3. Supplements - There is evidence that increasing the intake of omega 3 by taking 2000-3000mg daily supplements such as fish oil or flaxseed oil can relieve dry eye symptoms. It can take several months for an improvement in tear production to occur. Other advantageous diet inclusions include walnuts, oily fish, soybean, kale, spinach and eggs.
4. Dry eye contact lenses - For contact lens wearers there are a growing number of lenses designed to minimise dry eye symptoms. The most effective are listed below.
5. Environment - It is important to maintain a hydrated environment - use air-conditioning sparingly or at least direct the flow of air away from the face. Have plants in the room to help humidify the air and consider placing "floral foam" in a bowl of water. This is a block of foam available from florists and soaks up water to humidify the atmosphere. Wear sunglasses that wrap around the face to protect the eyes from drying wind.
6. Medication - A number of medications can exacerbate or cause dry eye. These include Betablockers (blood pressure), antihistamines (allergies), diuretics (fluid tablets) and antidepressants.
How do contact lenses contribute to dry eye?
Often dry eye is a pre-existing condition exacerbated through wearing contact lenses but some research indicates that long term contact lens wear may contribute to the development of dry eye. At least 50 percent of contact lens wearers present with occasional dry eye symptoms.
Contact lenses contain water, so to maintain their correct shape and optics they need to maintain hydration. Just like a sponge, the contact lens will soak up the tears available in order to maintain lens hydration. This can include soaking up the tears needed for the ocular surface. The result can be a dry eye condition.
What are the best contact lenses for dry eye?
The best contact lenses for dry eye are:
- Soft Hydrogel lenses with low water content soft lenses are often high in water content which encourages the lens to soak up more moisture and tears leading to dry eye. Choosing a lens with a lower water content and surface coating will lessen this process and diminish the lens sucking the tears from the eye.
- Silicone Hydrogel contact lenses - The technology behind silicone hydrogel lenses means that to maintain shape and optical effectiveness, these lenses require oxygen rather than water. This is known as oxygen permeability, which reduces the need for the lens to soak up the tears and moisture in the eyes. Different silicon hydrogel lenses have various treatments to the lens surface and matrix to reduce drying and make the lenses more hydrophilic.
- Daily disposables - Some daily wear lenses contain extra moisturising agents within the matrix of the lens, which releases moisture on each blink. This keeps the lens hydrated and reduces the need to absorb tears from the eyes.
For dry eye sufferers, the following lenses have been found to maximise lubrication and comfort and are recommended:
Proclear Compatibles - The Proclear range of lenses are made from omafilcon B which is a hydrogel material which features superior retention of moisture. This material has been found to retain 96% of its water content for up to 12 hours. The lenses are deposit resistant which means that the surface maintains its hydrophilic behaviour resulting in less drying. The lenses are manufactured using their PC technology which is molecule called phosphorylcholine. This is a hydrophilic molecule which means it attracts water ensuring the lenses retain their moisture throughout the day. Manufactured in a hydrogel material, they are an ideal lens for wearers who are unable to tolerate a silicon hydrogel lens.
BioTrue ONE day - This is a silicone hydrogel contact lens that is replaced daily. The daily replacement schedule means that the lens surface will be fresh and clean every day, minimising the risk of developing hydrophobic or water repelling deposits on the lens surface which would lead to dry eye. Manufactured from nesofilicon A, the lens is designed to maintain its water content during a full day of wear. BioTrue lenses incorporate a wetting agent in the lens matrix.
My Day Daily Disposable - This lens combines a daily replacement regime with hydrogen silicone technology. Featuring a new material called stenfilicon A, which forms the silicon matrix of the lens into channels, the lens is more efficient at delivering oxygen to the cornea. As a result, a lower silicon content of only 4.4% is required, which means that the lens is able to be more hydrophilic or wettable, leading to greater comfort. The contact is available in a daily wear mode which means less surface deposits with better wetting.
Acuvue Oasys (with Hydraclear Plus) - These 2 weekly disposable lenses are made from senofilicon A which has a low modulus (stiffness) and is a silicon hydrogel material. The lens material incorporates Hydraclear which is a wetting agent incorporated in the matrix of the lens. This leads to increased wettability and less dryness.
Dailies Total 1 - This lens combines all the recommendations for dry eyes in one: a silicone hydrogel daily contact lens with low water content. The delefilicon A material means that the lenses have a high degree of comfort and oxygen permeability and are designed to provide all day moistness and freshness. The lens has a variable water content with a lower water content in the centre of the lens whilst the outer most surface has a water content that approaches the cornea's natural water content. This means that the surface of the Total 1 lens has a particularly high degree of lubricity or slipperiness. This results in a high degree of comfort and oxygen permeability and are designed to provide all day moistness and freshness. Because of the increased lubricity totally dry fingers are essential to successfully remove these lenses from your eye.
Nothing can ever replace the weight and positive influence of a good eye and contact lens care program.
Posted 17 January 2020