Contact Lens Complications Introduction The last 20 years has seen a tremendous increase in the use of contact lenses. Despite the recent trend towards fashionable eyewear and the advances in refractive surgeries, there are still approximately 1 million Australians who are currently wearing contact lenses. This is partly because of the variety of lens materials, replacement schedules, specialty designs, and convenient contact lens care systems available today. While there are many benefits of contact lenses, both cosmetic and therapeutic, contact lens wear is not without risk of complications. Ocular complications of contact lenses include iatrogenic (inappropriate fit, prescription or wearing schedule), patient non-compliance or misuse, as well as inherent problems with the patients tear film, lids, lashes, or meibomian glands. Contact lenses are implicated in the pathophysiology of many anterior segment disorders.
Most commonly, these complications are due to hypoxia (oxygen deprivation to the cornea), mechanical stress, infection, or immunological factors. Soft contact lenses, also known as hydrogels, worn as extended wear (that is, up to a 7 consecutive day wearing schedule including overnight wear) have a significantly higher incidence (10-15 times the rate for daily wear hydrogels) of ocular complications. This is because corneal hypoxia is greatly exacerbated by overnight contact lens wear. A recent study found that in any given year, over 7% of all contact lens wearers experience an ocular complaint that is serious or bothersome enough to warrant a visit to their optometrist. The list of potential problems is long, and while many of the complaints are relatively minor, a few are potentially sight-threatening (see Table).
Table: Possible complications of Contact Lens Wear Potentially Sight ThreateningUsually Not Sight ThreateningUlcerative bacterial keratitisCorneal edemaFungal and protozoal keratitisGiant papillary conjunctivitisSuperior limbic keratoconjunctivitis3-9 O’clock stainingCorneal vascularizationCorneal abrasionCorneal distortionSolution hypersensitivityEpithelial microcystsEndothelial polymegathismContact Lens Acute Red Eye (CLARE) Contact Lens Related Problems Lens comfort problems There are many reasons why a contact lens may be uncomfortable to wear, including underlying eye disease and other contact lens complications discussed on this page. In cases where the eyes are healthy and the contact lenses are new, there is always the possibility that a lens is defective. Generally, if a lens of a given brand and curvature has been worn successfully in the past without problem, a new and uncomfortable lens makes one strongly suspicious of an abnormally curved lens, or a lens with a scratch or other defect. Since most manufacturers offer a warranty for defective lenses, it may be reasonable to return the lens for replacement or refund. In cases of new gas permeable or hard lenses, sometimes the lens can be smoothed or polished to improve the comfort. If a new lens of a different brand than has been worn before is uncomfortable, the problem may be with the fit (tightness) of the lens, the thickness of the lens, and the edge design of the lens.
Some soft contact lenses have a very high oxygen permeability (extended wear type lenses), and these may be more comfortable for some people. However, these lenses also demand more ocular lubrication to keep them hydrated and moist, so eyes which are somewhat dry may not be comfortable with this type of lens. If a lens is too tight, the cornea may become starved for oxygen, leading to discomfort (see Tight Lens Syndrome below). On the other hand, a lens that is too loose may irritate the eye due to excessive movement with blinking. Finally, certain characteristics of lenses (thickness and edge design) may be simply uncomfortable for some people. It may take a follow-up examination by the optometrist to distinguish between these problems.
An old lens that becomes uncomfortable may be developing deposits on the lens, scratches or nicks in the lens, or problems with the tears lubricating the surface of the lens. People are different with how long a given lens will remain comfortable, and good care of lenses will usually extend the life of a lens. Having to replace lenses frequently due to rapid protein deposit formation or other problems is a good reason to consider disposable lenses. As mentioned above, the development of an underlying eye disorder not related to the contact lenses can make their use uncomfortable. Some conditions include eye allergy, dry eye, blepharitis, conjunctivitis, eyelid problems, iritis, phlyctenulosis, and pterygium.
Pregnancy or hormonal changes are known to cause difficulty in contact lens use in women. Finally, other contact lens complications discussed below can cause discomfort with lens use. Wearing Time Problems People can develop problems with being unable to wear a lens as long as they would like. Sometimes this problem is simply related to external problems such as a high pollen count or being in an environment with poor air quality or low humidity. In cases where it becomes increasingly difficult to wear an older lens as long as previously, the lens may be developing protein deposits or other defects. Hard or gas-permeable lenses can often be polished, and will be comfortable to wear again, while soft lenses usually have to be replaced.
Some people are unable to wear any type of lens for the entire day, but can only wear the lens for a limited period of time. In cases where the eyes are somewhat dry, the use of rewetting drops (preferably preservative-free) can extend the time that the lenses can be used. Some people need to remove the lenses at some point during the day, such as lunchtime, and can then subsequently wear them longer during the afternoon. If one is having a problem with the wearing time of lenses, it is usually a good idea to have an eye examination to rule out any other potential problem such as infection or allergy. A lens case with solution should be carried if the lenses need to be removed during the day, since wearing a lens longer than it is comfortable can lead to disaster.
One should never put a contact lens in tap water, or in solutions not designed for lens storage or disinfection. It is also unwise for a contact lens wearer to use solutions other than those recommended by their optometrist. Wearing Problems Contact lenses are better at correcting certain types of vision problems than others can correct. Simple nearsightedness or farsightedness is usually easily corrected using contact lenses, but astigmatism can be more challenging to correct, especially with soft lenses. Contact lenses have varying success in correcting the need for reading glasses, with bifocal contact lenses rarely being successfully prescribed. Toric soft lenses have an astigmatism correction built into the lens, but rotation of the lens can lead to a shifting of the astigmatism correction, and temporarily blurred vision.
For people with severe or irregular astigmatism, rigid gas-permeable lenses (RGPs) or hard lenses may offer better visual results. Irregular astigmatism is a situation where the cornea is distorted due to a scar or underlying disorder. Sometimes rigid contact lenses are the ONLY way to correct the vision in these cases, as even glasses will not help (as in keratoconus). Many people who use contact lenses may experience halos around lights at night, and sometimes ghost images. This probably is a normal phenomenon in most people, and occurs when the pupil is larger (or more dilated) than the optical area of a soft lens, or of the lens itself in cases of rigid lenses. However, seeing a rainbow around lights indicates swelling of the cornea (corneal oedema), and indicates that the lenses have been in too long and should be removed. Blurred vision in one eye or the other with a contact lens that was previously clear could indicate a more serious eye problem, and should be checked by the optometrist. Of course, it is possible that lenses can become switched between the eyes, but usually this is fairly obvious.
An older lens can develop deposits and other surface problems, which can make the vision not only blurry, but also can make the lens uncomfortable to wear. Contact Lens Allergy The fact that a contact lens is constantly touching the eye leads to the possi …