Dr. David H. Haight has been involved with contact lens fitting of all types for over 30 years. He has servedas Co-chief of the Contact Lens Clinic at the Manhattan Eye, Ear & Throat Hospital and in that capacity has taught resident ophthalmologists techniques of lens fitting and proper followup care.
He is often quoted in the print media as an authority on contact lenses and has been interviewed about them on WCBS AM radio. Dr. Haight has been offering contact lens services in his private practice since 1985. A wide variety of lenses are currently available. Following below is a brief summary of the more common types of lenses and their applications.
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This is the original type of soft lens in use for over 40 years. It offers an excellent combination of comfort, good vision, low complication rate and durability. Lenses may be available in a variety of water contents ranging from low to moderately high. Low water content lenses are better for individuals with dry eyes and also offer slightly crisper vision. Higher water content lenses are generally more comfortable. These lenses are usually preferred if patients suffer from seasonal or ocular allergic reactions. Daily wear lenses must be removed each night for cleaning and disinfection. Weekly enzyme cleaning may also be needed to remove stubborn protein build-up. The life span of these lenses is about one year
Soft Lenses - Extended wear
Extended wear lenses are generally thinner than daily wear lenses and have higher water content. They are designed to permit overnight wear and can be left in for up to one week at a time. They are usually quite comfortable, but may not give as crisp vision as their daily wear counter parts. The main advantage to these lenses is the convenience they afford. They should be removed at least weekly for cleaning and disinfection. Careful follow – up is required because the rate of infection or allergic reaction with extended wear is up to 10 times greater than for daily wear. Some people will use them on a daily wear basis, thus taking advantage of the comfort without the added risks. The average life span of the lens is 6 – 12 months.
Soft Lenses - Disposables
Disposable lenses are essentially extended wear lenses designed to be discarded in a short period of time. They offer all the advantages of extended wear without the need for as much care. In the standard application the lens may be worn for 1 to 2 weeks and then replaced with no cleaning or disinfection needed. Others may use them as daily wears; in that application the lenses may be stored in disinfection solution overnight but not cleaned or enzymed. Most Disposables have a life span of 1 – 2 weeks. A daily disposable is available which permits a new lens every day. On the other end of the spectrum are planned replacement lenses, which are hybrids between daily and extended, wear lenses. The life span of these lenses is 2 -3 months and most can be used for overnight wear. This class of lens has become very popular since it combines comfort with reduced maintenance and readily available replacements
Soft Lenses - Toric
Toric lenses are soft lenses designed to correct astigmatism. They have an optical power that varies in relation to the position on the eye. Most rely upon some weighting at the bottom so that the proper alignment will be maintained. Fitting of these lenses is more demanding and can require more than one fitting session. Modern torics are capable of correcting large amounts of regular astigmatism. They are available as daily, extended wear, and disposable lenses. However given the exact prescription and ocular condition of an individual not all options may be available. Handling and durability are similar to the types listed above
Soft lenses - Bifocal
A variety of lenses are available with different corrective power for near and far. These lenses may be useful for patients over forty who do not wish to use reading glasses over their contacts. In some ways bifocal lenses mimic the corrective action of bifocal glasses. Most are daily wear lenses but a few extended wear and disposable types exist. There are even a few types of combined toric and bifocal lenses. Success with this lens type has been modest. As an alternative one can try monovision. In this application the dominant eye is fit for distance and the fellow eye is given a reading correction. The brain then automatically concentrates on whichever eye has the better vision. Some patience is required to determine whether a bifocal or monovision is better but the rewards can be worthwhile.
Soft Contact Lenses - Colored
Recently a variety of colored contacts have been introduced. These fall into three major categories.
• VISIBILITY TINTS
These lenses have a very slight tint (usually blue ) that makes it easier to visualize them in a lens case or when handling them for cleaning. This tint is not visible when worn and does not change the color of the eye.
• ENHANCER TINTS
These colors are designed to work with light colored eyes such as blue or green. The tint will work with the eye’s natural color to intensify or alter the perceived color. The overall effect can be very natural since the underlying iris color and pattern does not have to be covered up. These tints will not work for dark eyes.
• OPAQUE TINTS
This type of lens can completely alter the color of any eye, light or dark. The surface of the lens is treated with an opaque color placed in a pattern, which mimics the normal structure of the iris. Because none of the eye’s natural color shows through, the eye will take on the color of the lens. This feature is the great attraction of opaque lenses. The drawback is that in some eyes the effect does not appear completely natural.
Colored lenses are available as daily and extended wear, disposable and planned replacement lenses. However all colors and patterns are not made in each style. Colors for astigmatism are more limited and presbyopia is not yet available. Colored lenses may be worn even if no visual correction is needed ( no optical power in the lens. ).
Rigid Gas Permeable Lenses (RGP)
Derived From Original Hard Lenses
Gas permeable lenses are derived from the original hard lenses. They are rigid lenses, which permit oxygen but not water to pass through. This type of lens may be used for any of the corrections mentioned above. However there are certain situations in which it is preferable. Soft lenses are very flexible and will conform to the underlying shape of the eye. If that shape is irregular due to astigmatism or a corneal disorder a soft lens will not improve the vision. RGP lenses will because the front surface gives the eye a smooth and regular curvature, while the back surface masks the eye’s irregularity. Thus better vision can be obtained. RGPs may also be helpful for people with dry eyes or allergic reactions. Often the corrected vision will seem crisper with an RGP than with a soft lens. In general the risk of infection or allergic reaction to the lens is lower with an RGP than with a soft lens. The life span of an RGP may be one to several years with proper care. The daily maintenance is also less involved than for a soft lens.
Custom Made To Fit
RGP lenses are all custom made to fit each eye, and the fitting process can be lengthier than for soft lenses. Most commonly they are used for daily wear, but in some instances may be used for extended wear. RGPs require a break-in period of several days to a week or more during which the wearing time is gradually increased. Because the rigid lens may cause the cornea to alter shape slightly, vision with glasses may be blurred immediately following removal of the lens. This “spectacle blur” may last for hours to days. RGPs may be tinted for visibility, but do not change eye color. There are no disposable RGPs. Some types of RGPs are available as bifocals. Specialty designs are available for correction of severe distortions of the cornea as found in conditions such as keratoconus.
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The forgoing is a brief description of the various types of contact lenses most commonly used. A detailed consultation is necessary to determine which lens is best for any individual. Contacts can add enjoyment to daily activities and provide a better quality of vision. However to be safely used the care regimen prescribed for each lens wearer should be meticulously followed. All lens wearers should return for check-ups as recommended and require an annual comprehensive eye exam.