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Keratoconus, or "conical cornea" (from kerato- cornea and conus cone), is a degenerative disorder of the eye in which the cornea thins and changes shape to become more conical than the normal parabolic. more...

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Kostmann syndrome
Seborrheic keratosis

Symptoms and diagnosis

Keratoconus can cause the vision to become distorted quite badly, with "ghosting", "streaking", and light sensitivity all often reported. The exact nature of the visual distortion introduced by keratoconus is most clearly seen with a high contrast field such as a point of light on a dark background – instead of seeing one point the person may see over 100 images spread out in a complex and random pattern. The pattern does not change from day to day, but over the seasons it often takes on new forms. Doctors tend not to ask exactly what the patient sees, but rather test the vision on a standard Snellen chart of progressively smaller letters. Definitive diagnosis is obtained using corneal topography, a non-invasive visualization of the shape of the surface of the cornea.

The visual distortion comes from two sources, one being the irregular deformation of the surface of the cornea; the other being scarring that occurs on its exposed highpoints. Although some think the scarring is from abrasion by contact lenses, the phenomenon also appears in those who do not use lenses and as such appears to be an aspect of the corneal degradation.

Keratoconus and the associated vision loss, if in both eyes, can affect the person's ability to legally drive a car and function normally. Corrective lenses though, in most cases, allow the person to still drive a car.

Prevalence and cause

The National Eye Institute reports that keratoconus is the most common eye dystrophy in the United States, affecting approximately 1 in every 2,000 Americans, but some reports place the figure as high as 1 in every 500.

Keratoconus seems to have genetic components. Keratoconus is also diagnosed more often in people with Down Syndrome, though the reasons for this link have not yet been determined. Keratoconus has been associated with atopic diseases, which include asthma, allergies, and eczema, and it is not uncommon for several or all of these diseases to affect one person. Science has no definitive explanation of what causes keratoconus, however a number of studies suggest that eye rubbing may contribute to its development.


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Revisiting Daily Disposables
From Optometric Management, 9/1/05 by Schwallie, Joseph

While daily disposables may no longer conjure up excitement amongst practitioners, they are still considered a desirable advancement by our patients.

With the advent of silicone hydrogel contact lens materials and a renewed interest in extended wear, the excitement surrounding daily disposable contact lenses has waned in the last few years. Despite this subdued interest, daily disposable contact lenses are capable of providing many benefits while exceeding patient expectations. Convenience, comfort, clinical performance, and safety are just a few of the reasons daily disposable contact lenses should be considered a viable alternative for our patients. Of course, patient needs will often dictate the approach we take in prescribing a given contact lens. Knowing the advantages of daily disposable lenses will allow you to determine if this modality will meet those needs.

It's hard to believe, but daily disposable contact lenses became a reality in the marketplace more than ten years ago. While most international markets experienced growth in the utilization of daily disposable lenses, some countries embraced the concept faster than others. An evaluation of international contact lens prescribing in 2004 showed daily disposables only comprised 6% of new daily wear fits in the United States, compared with over 30% in markets like Japan, Norway and the United Kingdom.1 The discrepancy between international markets is likely related to the preferences and perceptions of not only patients, but also practitioners. Despite this discrepancy, the daily disposable lens category will continue to grow in the United States as product lines expand and consumer demand increases. There are currently three spherical daily disposable lenses available in the U.S. market, along with a daily disposable bifocal and a daily disposable toric (see table, page 102).


The primary factor driving the increased use of daily disposable lenses is convenience. Eliminating the time and effort involved in cleaning and disinfecting, as well as the need to purchase the products, simplifies the daily routine for patients. The current availability of daily disposable lenses makes this modality available to nearly every contact lens wearer. While every patient will appreciate a simplified lifestyle, the convenience aspect of daily disposable lenses may be especially appealing to certain categories of patients.

Children and teens represent a significant population of patients who are particularly attracted to the convenience of daily disposables. In addition, these patients represent the largest portion of new patients in the vision-correction market at 36%.2 Parents are also attracted to the convenience and safety of daily disposable lenses. Prior to the introduction of disposable lenses, the fear of losing or tearing a lens added to the apprehension of parents considering contact lens wear for younger children. With daily disposables, the level of concern regarding loss or damage is much lower when the cost of lens replacement is $0.50 per lens, versus $50 per lens. Easy access to lens replacements helps address the issue of lost and torn lenses as well. Eliminating lens care also appeals to parents. They appreciate knowing they won't have to rush out to the store to purchase more contact lens solution when their child tells them at 11:00 p.m. that they ran out.

In today's practice, it's not uncommon for children as young as eight years old to present to your office for a contact lens exam. For these patients, convenience and ease of use are paramount to success. A study at the Ohio State University's College of Optometry examined daily disposable lenses in children.3 Results showed eight- to 11-year-old subjects are able to independently care for daily disposable contact lenses and wear them successfully. The researchers reported a 90% success rate with subjects who "usually did not have a problem" or "never had a problem" handling their contact lenses.

Contact lens wearers with certain occupational and recreational needs are also excellent candidates for daily disposables. Frequent travelers comment about the ease of traveling with daily disposable contact lenses because they don't have to pack solutions and spare lenses are readily available. Contact lens patients who work in environments where there is a risk of lens contamination are also excellent candidates. For example, individuals who work at dusty construction sites, fume ridden chemical plants, smoky restaurants, or even hospitals will appreciate the added aspects of a cleaner, safer contact lens. It's also great for keratoconus patients who use a piggy-back system to improve comfort and corneal physiology.


The health benefits are a significant element to the excellent comfort obtained with daily disposable lenses. Lenses that are replaced every day are cleaner and allow less time for deposits to build-up on the surface compared with lenses that are replaced less frequently.4 Using a clean lens every day can help patients avoid problems associated with contact lens deposits, such as contact lens-induced papillary conjunctivitis and bacterial binding. Daily disposable contact lenses may also offer an improvement over two-week disposable lenses.

One study showed 82% of patients preferred the overall comfort of a daily disposable lens when compared with a two-week disposable lens.5 The obvious difference between these replacement regimens suggests that comfort is better when contact lenses are replaced more frequently. Over time, contact lenses will accumulate a variety of components commonly found in the tear film. These deposits contribute to lens discomfort, as well as potentially adding to the risk of inflammatory reactions and infections.

Of course, any lens that is used more than once requires cleaning and disinfection at the end of each day. The potential adverse impact of disinfecting solutions on the comfort of contact lenses cannot be ignored. Several contact lens disinfecting systems have been associated with corneal staining, palpebral hyperemia, itching and dryness. And, dryness and discomfort are the most often cited reasons for discontinuation of contact lens wear. If you suspect a patient is experiencing discomfort or dryness related to solution sensitivity, the simplest resolution may be eliminating the solutions altogether.

Another common cause of discomfort associated with contact lens wear is allergies. Research shows that 20% to 30% of the U.S. population suffers from some form of allergic eye disease. One study evaluated patients with seasonal allergic conjunctivitis wearing either daily disposable contact lenses or a new supply of their habitual contact lenses.7 Patients who wore the daily disposable lenses had fewer total symptoms of seasonal allergic conjunctivitis compared with patients who wore their habitual lenses. Another study showed certain allergy eyedrops used concomitantly with daily disposable contact lenses may be beneficial and prevent chronic absorption of the medication or its preservative.8 The authors concluded that use of Livostin with daily disposable contact lenses is safe and associated with minimal symptoms. While eliminating the allergen is the only true way to avoid allergic conjunctivitis, recommending a contact lens option to increase patient satisfaction will benefit not only the patient, but also your practice.


Studies suggest that even though 75% of soft contact lenses are prescribed for a replacement schedule of less than two weeks, only 25 % of patients adhere to that schedule.9 One-fourth of patients stretch the replacement schedule to one month and 23% to as long as six months. Another study showed 53% of patients replace their lenses less frequently that recommended.1" Many practitioners find that, among all types of lens wear, daily disposable wearers had the highest level of patient compliance. Some studies report this to be as high as 93%." The chart above shows compliance rates with replacement schedules for daily disposable, continuous wear and two-week disposable lenses.12 It also shows compliance rates with cleaning and disinfection systems, as well as patient compliance with changing their contact lens case at least once a year. While cleaning, disinfection and case replacement may not be an issue with single use lenses, it may compound the issue of non-compliance with two-week disposables and other multi-use lenses.

Part of the high level of compliance with daily disposable lenses may stem from this fact: Patients select daily disposable lenses for the convenience of not having to clean them. Purchasing the lenses for their added convenience, and then avoiding compliance by cleaning and re-using the lenses doesn't make sense. Of course, some wearers will undoubtedly try to wear their lenses beyond one day. In this instance, it's quite possible that lens performance may suffer. According to CIBA Vision, patients tempted to re-use their Focus Dailies lens will experience about a 25% reduction in comfort with each successive day of use.

Inflammatory conditions such as contact lens induced papillary conjunctivitis, limbal hyperemia, and moderate-to-severe corneal staining are just a few of the potential complications associated with non-compliance to the recommended replacement schedule. Lenses worn past their recommended replacement schedule risk accumulating a greater amount of tear components such as albumin, lysozyme and lactoferrin, which increase bacterial adhesion of certain strains of Staphylococcus and Pseudomonas to the surface of a contact lens, potentially increasing the risk of microbial keratitis.13-16


Discussion about daily disposable contact lenses wouldn't be complete without touching on the sensitive issue of cost. Despite the benefits of daily disposable lenses, many patients, as well as practitioners, eliminate them as a potential option because the preconceived notion is that they are too expensive. Undoubtedly, there will be some patients who will be taken aback by the annual cost associated with daily disposable contact lenses. However, these patients may be equally surprised to learn how much they are already spending on their contact lenses and solutions. The simple answer to the question, "Do daily disposables cost more than my current two-week disposable lenses?" is yes. But a more appropriate answer that provides direction is, "Yes, but would you like to know the difference in cost and give the lenses a test drive before you decide?" If the patient answers "No," you can move along and complete your exam. If the answer is "Yes," then you can proceed with further explanation. Showing concrete examples of annual price comparisons is often helpful, including the cost of solutions as well as lenses. The chart on the right shows a relative comparison of the annual cost of various contact lens modalities and their accompanying solutions.17 Some practitioners also find value in offering cost comparisons relative to a cup of coffee, owning a cell phone, or adding premium options to their eyeglasses.

As practitioners, we must put aside our tendencies to pre-judge the affordability of daily disposable lenses for a given patient. As noted above, some patients will have absolutely no interest in paying one cent more for their contact lenses, especially if they are non-compliant with their current replacement schedule. All too often it's not until I show patients how much they are paying for their current two-week disposable lenses that they blurt out, "Oh, I don't spend that much on contact lenses because I only replace them every other month." Of course, this opens up a whole new can of worms, but it's the kind of truthful information that allows us to make recommendations based on the best medical interest of the patient.

Much like any aspect of a practice, success is highly dependent upon your commitment, enthusiasm and willingness to inform and educate patients about daily disposable lenses. Most experts agree that the best way to do this is to offer them a small supply of diagnostic lenses.

Offering the option of daily disposable contact lenses to every patient who qualifies helps us address their needs. As a primary care practitioner, if you feel a daily disposable contact lens is the best option for your patient, it is your duty to recommend it.


This Strategic Skill Builders Continuing Education course is made possible by a special grant from CIBA Vision. Blacken the most appropriate answers on the mail-in card and mail it no later than September 15, 2006 to: CE Test, Optometric Management, 8360 Old York Road, Elkins Park, PA 19027. Please allow at least 6 weeks from the closing date to receive your certification.

If you pass the test, you'll receive credit from the Irving Bennett Business and Practice Management Center at the Pennsylvania College of Optometry. This course has been approved by the Council on Optometric Practitioner Education (COPE) for two continuing education credits. The COPE LD. Number is 14445-CL. For more information, e-mail

1) Which country showed a low percentage of new daily disposable lens fits compared with other countries:

a. United States

b. United Kingdom

c. Japan

d. Norway

2) In some countries outside the U.S., daily disposables comprise what percentage of new daily wear lens fits:

a. 10%

b. 20%

c. 30%

d. 50%

3) Daily disposable lenses are currently available in:

a. Spherical lenses

b. Toric lenses

c. Bifocal lenses

d. All of the above

4) What is the primary factor driving the increased use of daily disposables?

a. Price

b. Comfort

c. Compliance

d. Convenience

5) What percentage of entrants into the vision-correction market do teens represent?

a. 71%

b. 45%

c. 36%

d. 23%

6) At what age can children successfully wear daily disposable lenses?

a. 5 years old

b. 8 years old

c. 10 years old

d. 13 years old

7) Which factor(s) influences parents' decisions about lenses for children?

a. Low replacement cost for lost or torn lenses

b. The added health benefits

c. Eliminating lens care

d. All of the above

8) Which patients may appreciate the convenience of daily disposables?

a. Frequent travelers

b. Construction workers

c. Athletes

d. All of the above

9) Daily lens replacement reduces may help patients avoid:

a. Inflammatory reactions

b. Infections

c. Discomfort

d. All of the above

10) What percentage of patients preferred daily disposable lenses compared with two-week disposables?

a. 51%

b. 61%

c. 74%

d. 82%

11) Which of these may contact lens cleaning solutions contribute to?

a. Corneal staining

b. Cataracts

c. Stromal acidosis

d. Filamentary keratitis

12) How much of the U.S. population suffers from allergic eye disease?

a. 5-10%

b. 10-20%

c. 20-30%

d. 50-60%

13) Daily disposable lenses can alleviate which allergic symptoms?

a. Burning

b. Redness

c. Both a and b

d. Neither a nor b

14) What can be safely treated with eye drops and daily disposable lenses?

a. Allergies

b. Bacterial Infections

c. Viral Infections

d. All of the above

15) Compliance with daily disposable lens replacement schedule has been shown to be as high as:

a. 93%

b. 87%

c. 80%

d. 75%

16) Which replacement schedule shows the lowest level of compliance?

a. Daily disposables

b. Continuous wear

c. 2-Week disposables

d. IOLs

17) What can habitual over-wear of soft contact lenses contribute to?

a. Contact lens-induced GPC

b. Limbal hyperemia

c. Moderate-to-severe corneal staining

d. All of the above

18) Re-use of contact lenses can increase the adhesion of:

a. Moraxella

b. Candida

c. Pseudomonas

d. Used car salesmen

19) The cost of daily disposable lenses is comparable to:

a. Continuous wear

b. 2-week disposables including lens care

c. Both a and b

d. Neither a nor b

20) Which is most important to achieve success with daily disposables?

a. Practitioner commitment

b. Staff enthusiasm

c. Patient education

d. All of the above

To send in your answers to these questions, fill out the continuing education card included, affix a stamp and mail it in.


1. Morgan PB, et al. International Contact Lens Prescribing in 2004. CL Spectrum. 2005 Jan; 20(l):34-37.

2. BarrJT. 2004 Annual Report. CL Spectrum. 2005 ]an; 20(1):26-31

3. Walline J, Long S, Zadnik K. Daily Disposable Contact Lens Wear in Myopic Children. Optom and Vis Sc. 2004 Apr; 81(4):255-259.

4. Curtis W. Continuous Wear or Daily Disposables: What's Best For Your Patients. CL Spectrum. 2002 Aug; 17(8): 33-37.

5. Sindt C. Daily Disposable Versus Two-Week Disposable Lenses. CL Spectrum; 2000 May; 15(5),33-36.

6. Dillehay SM, et al. A Comparison of Multi-purpose Care Systems. CL Spectrum. 2002 Apr; 17(4):30-3S.

7. Stiegmeier MJ, Thomas S. Seasonal Allergy Relief with Daily Disposable Lenses. CL Spectrum. 2001 Apr; 16(4):24-28.

8. Kirstein MD, et al. Topical Antihistamine Proven Safe in Single-use Lens Wear. CL Spectrum. 2001 jun; 16(6):40-42.

9. Collins M], Carney L.G. Compliance with Care and Maintenance Procedures Amongst Contact Lens Wearers. J Optom Asso of Australia. 1986; 69:166-199.

10. clay don BE, Efron N. Non-compliance in contact lens wear. Ophthalmic Physiol Opt 1994 April; 14(4):356-64.

11.Ky W, Schenck K., Stenson S. Clinical Survey of Lens Care in Contact Lens Patients. CLAO. 1998 October; 24(4):216-219.

12. Dillehay S, et al. Patient Experience and Management in HDK Silicone Hydrogel Soft Contact Lenses, Posters. April 2004.

13. Nichols KK, et al. Corneal Staining in Hydrogel Lens Wearers. Optom Vis Sd. 2002 Jan; 79(1):20-30.

14. Langis M, Giasson C]. Overwear of Contact Lenses: Increased Severity of Clinical Signs as a Function of Protein Absorption. Optom Vis Sd. 2002 March; 79(3):184-192.

15. Choo J, et al. Bacterial Populations on Silicone Hydrogel and Hydrogel Contact Lenses after Swimming in a Chlorinated Pool. Optom Vis Sd. 2005 Feb; 82(2):134-137.

16. Miller M], et al. Effects of Protein, Mucin and Human Tears on Adherence of Pseudomonas aeruginosa to Hydrophilic Contact Lenses. J Clinical Microbiol. 1998 Jan;26(3):513-5l7.

17. Mai-Le K, Caroline P. The Cost of Lens Care Vs. Daily Disposable Contact Lenses. CL Spectrum. 2001 JuI; 16(7):25-27.


Copyright Boucher Communications, Inc. Sep 2005
Provided by ProQuest Information and Learning Company. All rights Reserved

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