The contact lens market
has been booming over the past few decades for cosmetic use and for refractive correction. The United States Food and Drug Administration (US FDA) classifies contact lenses as a medical device for cosmetic uses and refractive correction; therefore, they cannot be purchased legally without a prescription that specifies the contact lens brand and lens parameters.1
Some reasons patients consider contact lenses include:
- Contact lenses allow for natural field of view and reduced distortions
- They can provide superior vision for sports and other physical activities.
- Compared to glasses, contact lenses offer better and more natural vision.
Contact lenses are a great adjunct to glasses for improved quality of vision however one must understand their limitations. Hygiene and proper care of the lenses is very important to avoid complications including infections. Studies have shown that patients who purchase their lenses on the internet have a higher risk of contact lens-related complications.15
This article will review the basics of usingsoft contact lenses
along with associated complications.
To pre-empt many contact lens complications, when selecting a contact lens for a patient, consider the following:
- Contact lens material
- Lens oxygen transmissibility
- Modality/Replacement schedule
- Contact lens comfort
- Contact lens fit
Contact lens materials13,15,16 are commonly in two categories:
- These are gel-like plastic lenses
- They are thin, pliable and conform to ocular surface
- These are advanced hydrogel lenses with silicone technology
- They allow for more oxygen to pass through the lens and reach the ocular surface
- These are popular for daily wear
Lens oxygen transmissibility (Dk/t)13,15,16 takes into consideration a material’s oxygen permeability (Dk) and the lens thickness (t). The higher value identifies the higher amount of breathability. A low Dk value lens has greater risk of limbal hyperemia and 3x increase risk of neovascularization.
The replacement schedule is dependent on contact lens modality. Soft lenses have these general classifications, based on how frequently they should be discarded:
- Daily disposable lenses — Discard after a single day of wear
- Biweekly lenses — Discard every two weeks, or sooner
- Monthly lenses — Discard monthly or quarterly
Even with proper care, soft contact lenses should be replaced frequently to prevent the build-up of lens deposits and contamination that increase the risk of eye infections.
Contact lens comfort13,15,16 is dependent on lens design and lens modulus. Lens design (base curve and diameter) determines the fit and shape of lens on the cornea. Lens modulus determines the thickness of the lens (eg. the higher the Dk/t value, the stiffer the lens). Tear exchange and lens movement may be limited if the lens is too soft. Contrarily, distortions may occur if the lens is too stiff.
Contact lens cost13,15,16 is dependent on the modality of choice and what supply is ordered. Daily lenses are usually seen as more expensive by most patients; however, the cost of contact lens solution must be taken into account with the purchase of monthly and bi-weekly lenses. Cost comparison should always be considered in terms of wear time for patients; if a patient requests a contact lens for occasional wear (1-2x per week), then daily lenses may be more affordable. However, if the patient would like to wear lenses 4-5x per week, it may be beneficial to present monthly lenses as an option.
To summarize, choosing the perfect lens for a patient is dependent on several factors. Patient expectations should be met, however one must not forget the patient’s medical history and how the lens fits on their eye.
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Use this list to prescribe the perfect contact lenses for each patient, every time.
Contact lens wear and care
Patient education regarding contact lens wear time and care is important prior to the release of contact lens prescription. Contact lens wearers should always practice good hygiene when handling lenses.
Guidelines for the standard of care include the following recommendations:
- Exercise proper hand washing
- Patients should always wash their hands prior to handling contact lenses.
- Washing hands with soap and water is recommended for at least 20 seconds.
- If soap and water is not available, use hand sanitizer with at least 60% alcohol.
- Disinfect contact lenses
- For daily disposable lenses, one should discard lens daily
- For biweekly or monthly contact lenses, one should disinfect the lenses daily with hydrogen peroxide solution or multipurpose solution
- Replacement schedule for contact lenses
- For daily disposable lenses, one should discard lens daily
- For biweekly contact lenses, one should replace lens every 2 weeks
- For monthly contact lenses, one should replace lens every month
- Discontinue contact lens wear
- Patients who have cold or flu symptoms should temporarily stop wearing lens
- Patient should not wear lenses if eye infection is suspected
- Patient should not wear lenses if lens is torn
Restrictions for contact lens use
Contact lenses should not be worn when sleeping
, swimming, or showering. Studies show a higher risk of infections when patients sleep in lenses.4
Lack of oxygen to the cornea can cause complications and may lead to blindness in severe cases.
Contact lens complications
Although contact lenses can be used safely, it is still a medical device with limitations. Patients assume the use of contact lenses can replace the need for spectacle correction; however, this is not the case.
Contact lens overwear syndrome occurs when patients wear lenses beyond the prescribed length of time, especially when the patient sleeps with lenses or neglects to replace them. Studies show the risk of microbial keratitis is 5.4x higher in cases of overnight wear of contact lenses.4
- Etiology: reduction in oxygen that reaches the cornea
- Symptoms: redness, eye pain, decreased vision, photophobia
Below is a list of signs of contact lens overwear syndrome, ranging from mild to severe conditions:
Contact lens acute red eye (CLARE)1,12
- Acute onset red eye usually seen with contact lens overwear or sleeping in lenses
- Etiology: hypoxia, mechanical irritation, solution hypersensitivity or lens intolerance
- Symptoms: irritation/discomfort, red eye especially with increased wear
- Signs: conjunctival injection with focal or diffuse epithelial or subepithelial infiltrates in mid-peripheral cornea
- Treatment: discontinue contact lens use, prescribe topical steroid, counsel on proper CL wear and hygiene
Figure 1: CLARE12
Giant papillary conjunctivitis (GPC)1,12
- Papillary reaction under the upper tarsal conjunctiva
- Irritation/itching upon removal of lens
- Blurry vision after increased wear time
- Movement of lens upon blink
- Inability to tolerate lens, foreign body sensation/pain during wear time
- Thickened palpebral conjunctiva
- Enlarged papillae upon lid eversion
- Discontinue contact lens wear for 1 to 2 weeks
- Prescribe topical antihistamine (if mild) and/or topical steroid (if advanced)
- Growth of new blood vessels onto the cornea
- Etiology: lack of oxygenation to the cornea
- Treatment: change to more oxygen permeable contact lens or daily wear; if severe, may require discontinuing contact lens wear permanently
Figure 2: Corneal neovascularization12
- Symptoms: pain, redness, photophobia
- Signs: epithelial defect with underlying subepithelial infiltrates – may be central or peripheral
- Treatment: discontinue CL wear, prescribe fortified antibiotic q1-2 hours, follow up 1 day until improvement noted
Figure 3: Bacterial ulcer12
Contact lenses can provide great vision and comfort. Patient education on limitations of CL wear can help significantly minimize these complications.
Contact lenses and COVID-19
With the turn of events with the COVID-19 pandemic, numerous questions about the safety and use of contact lenses have arisen. The general consensus among practitioners and the American Optometric Association and the American Academy of Optometry is that contact lenses are safe to use as long as patients follow standard contact lens hygiene protocols.5,7,8
Contact lenses are a great adjunct to spectacle wear. When used correctly, one can achieve great vision and comfort. However, if used incorrectly, contact lenses can cause detrimental complications including severe infections and blindness. Patients should always be reminded of proper contact lens hygiene, the importance of purchasing contact lenses based on a valid prescription, and the importance of annual contact lens assessments to ensure satisfactory lens comfort, fit, and vision.
- Fulmer, P. Here’s how to handle these complications of contact lens overwear. 2016. https://eyesoneyecare.com/resources/vertex-distance-conversion-downloadable-cheat-sheet/#unlock-formhttps://uihc.org/health-topics/dos-and-donts-contact-lens-wear
- American Optometric Association. Types of Contact Lenses. https://www.aoa.org/healthy-eyes/vision-and-vision-correction/types-of-contact-lenses?sso=y
- Dart Jk, Radford CK, Minassian D, Verma S, Stapleton F. Overview of Contact Lenses. Ophthalmology. 2008; 115(10):1647.
- Abesamis-Dichoso C. Contact Lenses Still Safe In Covid 19 Era. Modern Optometry. May/June 2020.
- Chalmers RL, Keay L, McNally J, Kem J. Multicenter case-control study of the role of lens materials and care products on the development of corneal infiltrates. Optom Vis Sci. 2012;89(3):316-325.
- Contact lens wear during COVID 19. American Optometric Association. www.aoa.org/covid-19-patient-resources/contact-lens-wear-during-covid-19.
- COVID-19 and contact lenses: the facts you need to know. Centre for Ocular Research and Education. https://core.uwaterloo.ca/covid-19/
- COVID-19 Eye Health Care Guide for Patients. American Optometric Association. https://www.aoa.org/healthy-eyes/caring-for-your-eyes/covid-19-eye-health-care-guide-for-patients?sso=y
- Cole J. Choosing the right contact lens modality. Review of Optometry. August 15 2017. https://www.reviewofoptometry.com/article/ro0817-choosing-the-right-contact-lens-modality
- Nixon G. A Review of Contact Lens Modalities. Contact Lens Spectrum. March 1 2006. https://www.clspectrum.com/issues/2006/march-2006/a-review-of-contact-lens-modalities
- Townsend W. When the Problem is Not Infectious. Review of Cornea & Contact Lenses. October 10 2010. https://www.reviewofcontactlenses.com/article/when-the-problem-is-not-infectious
- Athreya PK, Bhardwaj GK. Contact Lens Materials and Modalities. Tr Ophtha Open Acc J. 2008;1(2):10-14. https://lupinepublishers.com/ophthalmologyjournal/pdf/TOOAJ.MS.ID.000106.pdf
- Allansmith MR, Korb DR., Grenier JV et al. Giant Papillary Conjunctivitis in Contact Lens Wearers. Am J Ophthalmol. 1977;83(5):697-708.
- Jones L. Modern Contact Lens Materials: A Clinical Performance Update. Contact Lens Spectrum. September 2002. https://www.clspectrum.com/issues/2002/september-2002/modern-contact-lens-materials-a-clinical-performa
- Stapleton, Fiona, et al. The incidence of contact lens–related microbial keratitis in Australia. Ophthalmology 115.10 (2008): 1655-1662
- Ng,M. Contact Lens Tips Every Optometrist Wants You To Know. March 2020. http://www.drmikeng.com/new-blog/2019/2/24/contact-lens-tips-every-optometrist-wants-you-to-know
- Nixon, G. A Review of Contact Lens Modalities. Contact Lens Spectrum. March 2006. https://www.clspectrum.com/issues/2006/march-2006/a-review-of-contact-lens-modalities