The development of soft contact lenses began in the early 1960s with the pioneering work of Otto Wichterle in Prague, Czechoslovakia. The evolution of the modality has included dramatic changes in lens materials, care solutions, wearing schedules and, most recently, frequency of lens replacement. During the first decade and a half the industry focused its attention on the development of more deposit resistant and physiologically acceptable materials. Practitioners were awaiting a lens with enough oxygen transmissibility and deposit resistance that could be safely worn for thirty continuous days without compromising corneal integrity.
It soon became apparent that thirty-day extended wear was contraindicated for a significant percentage of the contact lens wearing population, and the decision to limit overnight wear to seven days was agreed upon between lens manufacturers and the Food and Drug Administration (FDA).
In 1987 Vistakon released the first "disposable" lens, Acuvue. The initial intent of the lens was for single use for seven consecutive days of overnight wear. The lens would be virtually maintenance free, requiring only removal of the old lens and insertion of a new lens on a weekly basis.
Negative publicity surrounding the overnight use of soft contact lenses had lessened the demand from patients and many practitioners began instructing their patients to re—use the lens on a daily wear or occasionally extended wear basis with one to two weeks disposal. Because of this, the FDA evaluated the definition of a “disposable” lens. In 1988, the decision was announced that the wording “disposable" would be defined as a single use product as is the case for all other medical devices. The terminology on product labeling was quickly changed to accommodate this decision. Package inserts now specifically indicate that planned lens replacement may be prescribed for either single use disposable wear or reusable frequent replacement wear.
The frequency of lens replacement and wear schedules has been left to the discretion of the practitioner and can be varied from one patient to another Today, the manufacturers usually recommend a suggested schedule of replacement for their lenses, but this is not mandated by the FDA. Many reusable lenses are often improperly referred to as "disposable" lenses. Caution should be exercised when dispensing “true" disposable lenses to patients in which reuse was never intended. Package inserts quite specifically define disposable wear as a single use wear of the product, therefore no cleaning or disinfection solutions have been approved for use with the product.
The newest member of this family of lenses is the single use daily wear disposable from Vistakon. This lens offers simplicity, as it requires no lens care; and is used strictly on at daily wear basis. Patients that are thought to be sensitive to lens care products or heavy lens deposits are: excellent candidates for daily wear disposable enses.
Soft Lens Complications
A number of soft-lens complications often escape detection in the early stages because the patient may be asymptomatic or vague. Most of these corneal complications can only be observed with a biomicroscope and sodium flourescein or flourosoft. Unfortunately, these relatively small complications can develop into significant corneal problems if not detected and resolved. The following are examples of corneal, conjunctival and lid complications that may be best suited for use with soft tenses that are replaced more frequently.
Corneal and Conjunctival Complications
Arcuate Staining: Arcuate staining is a sift lens complication that is often referred to as smile stain. Patient symptoms range from a mild awareness to severe discomfort depending on the severity of the condition. Slit lamp examination with flourescein reveals a coarse arcuate punctate epithelial disruption in the inferior mid-peripheral cornea. This can occur on patients with clean, well-fitted lenses on either a daily or extended wear basis. It appears independent of water content, lens thickness or patients prescription.
Although the etiology is unclear; theories include incomplete blinking, mechanical disruption of the epithelium by the contact lens, or desiccation from metabolic debris trapped beneath the contact lens. It has been suggested that this inactive tear film may have a toxic effect on the localized epithelium.
Treatment includes lens discontinuation until the epithelium heals. Ocular lubricants may be prescribed to lessen the dryness symptoms. The patient should be refitted, using a different soft lens material, and followed closely for possible reoccurrence of the condition. Daily disposable lenses may aid in increasing on-eye lens dynamics to aid in the removal of trapped debris.
Limbal Epithelial Hypertrophy is an area of heaped-tip epithelium located in the peri-limbal cornea. Although this is not a serious complication, its presence may be a precursor to future problems such as corneal vascularization. This condition is associated with both daily and extended wear soft contact lenses and often goes undetected since most patients are asymptomatic. Detection of the peripheral furrows cannot be made with the white light of the slit lamp. Fluorescein is required to highlight the condition. The hypertrophy may initially appear in one quadrant of the cornea expanding to a band or ring around the entire cornea near the limbus.
The condition resolves itself within seven to ten days after discontinuation of lens wear. Treatment includes refitting into a lens with greater on-eye movement and decreasing wearing time if the program persists.
Corneal Vascularization is an in-growth of blood vessels into the normally clear, avascular cornea. It is best observed with the white light of the biomicroscope. Patients are often asymptomatic.
There are two possible explanations for vessel growth in the corneal tissue, the hypoxia theory and the vasostimulation theory. In the hypoxia theory, the corneal tissue becomes edematous, resulting in an increase of lactic acid, which may result in reduced venous drainage. additionally, chronic edema may result in stromal softening or loss of lamellar compactness reducing the physical barrier to vessel penetration.
The vasostimulation theory suggests that epithelial trauma induced by contact lens wear causes a release of enzymes. The enzymes stimulate inflammatory cell migration to the site, which releases vasostimulating agents that cause blood vessels to grow in that direction.
Whatever the mechanism, vascularization of corneal tissue is an indication of less than optimal conditions. When vessels are observed, their length should be carefully measured and their location charted, in some cases, it may be necessary to reduce wearing time or even discontinue contact lens wear if any underlying pathology needs to be treated. Refitting options should be directed toward decreasing the physiologic insult to the cornea, and may include: using a· material with higher oxygen transmissibility, flattening the fitting relationship to avoid peripheral lens tightening and avoiding care systems that could induce a toxic or allergic response. Follow up care should be more frequent with special attention directed to the fitting relationship of the contact lens and the peripheral cornea.
Superior Limbic Keratoconjunctivitis (SLK) induced by soft contact lenses can appear in as short a time as one month or after years of successful contact lens wear. Patient symptoms include burning, itching, redness and photophobia that may worsen with time.
Slit lamp examination reveals mild papillary hypertrophy, inflamed superior tarsal conjunctiva, bulbar conjunctival staining, superior limbal hypertrophy, and puncture staining of the superior one third of the cornea. This condition usually occurs bilaterally and can advance to a micropannus or slight opacification of the cornea near the superior limbus.
The etiology of SLK is unclear, but solution hypersensitivity should be strongly suspected. The possibility of an immunologic response secondary to lens spoilage should also be considered. In either case, daily disposable or more frequent replacement of lenses in conjunction with an non-preserved care system should be utilized after the SLK is resolved. Unfortunately, resolution requires discontinuation of the contact lenses of as long as ten months in severe cases.
Solution Sensitivity (Chemical Keratitis) can occur at any time during the patient’s contact lens wearing history. The reaction can be acute with onset at the first use of a particular solution. Because this reaction is so obviously solution related, it is relatively easy to diagnose. When the reaction is delayed, as is usually the case, it is much more difficult to identify the source of the problem. This is especially true if the patient has been using various brands of saline and disinfecting solutions.
Subjectively, the patients complaints will include burning, stinging on lens insertion, photophobia and possibly an increase in discharge from both eyes. Unfortunately, these symptoms resemble those of a dry eye and often patients are encouraged to discontinue contact lens usage. Slit lamp Endings reveal a diffuse limbus-to-limbus punctate staining and conjunctival injection. This toxic destruction of corneal and conjunctival epithelial cells can occur in both soft and RGP lens wearers. In extreme cases, formation of chemically induced sub-epithelial infiltrates can be observed. They will appear as diffuse grayish opacities located in the anterior one half of the cornea. Lens wear should he discontinued until the cornea clears, which can take from five days to three weeks.
Rigid lens wearers can usually continue successful lens wear with a change of solutions. Soft lens wearers often require lens replacement due to the absorption of preservatives from their previous care system. At the very least, the soft lens patient should be placed on a preservative-free disinfecting system. Ideally, the use of daily disposable lenses will eliminate the need for any exposure to lens care products.
Epithelial Splitting is a commonly missed epithelial defect in the superior limbal area of the cornea. Patients are usually asymptomatic but may experience a slight foreign body sensation. These superior epithelial arcuate lesions are usually found during routine contact lens examination.
The linear breaks are mated in the superior corneal epithelium beneath the upper lid and are typically unilateral. Normal corneal epithelium separates the lesion from the limbus with little or no injection of the superior bulbar conjunctiva. The lesions are approximately 5mm wide and 2 to 5mm in length with depths to the Basement membrane.
Although etiology is unknown, the condition appears to be related to a mechanical bending of a more rigid lens by the upper lid. The treatment includes discontinuation of lens wear until the lesion has healed, usually within 24 to 48 hours. The patient should then be refitted in a less rigid plastic on as daily disposable or frequent lens replacement system.
Soft Lens Associated Corneal Hypoxia (SLACH Syndrome) is a spontaneous focal loss of epithelium attributed to long-term, chronic hypoxia. This complication is usually seen in daily wear soft lens patients wearing lenses that are at least one year old. Symptoms include bilateral blurry vision with pain; tearing and photophobia eight hours alter lens removal. Slit lamp examination reveals bilateral circular epithelial defects that can cover 30 to 40% percent of the corneal surface. Contact lens induced hypoxia is believed to lead to a loosening of intercellular junctions with a loss of epithelial adherence to the underlying Bowman’s membrane. Refitting the patient with a more oxygen transmissible daily disposable or frequent replacement lens is advisable.
Microcysts - Patients with epithelial microcysts are usually asymptomatic or have mild complaints of reduced lens comfort. Microcysts are usually discovered on routine follow up care months after lens wear has been initiated.
On slit lamp observation, microcysts appear as small, translucent, irregular shaped inter-epithelial cysts. They form near the basement layer of the epithelium and more forward toward the anterior surface. Microcysts consist of degenerated basement membrane cells. The etiology for their formation is a delayed response to high levels of corneal hypoxia. Their appearance does not seem to affect vision or have any direct clinical consequences. The cysts are best seen with retro-illumination and will not stain with fluorescein until they break through the epithelial surface. Although epithelial cell migration is thought to be approximately seven days, on average it takes months for the microcysts to resolve following lens discontinuation. During this time, the number of cysts can increase and decrease in cycles.
Patients with significant numbers of microcysts should be refitted with a more oxygen transmissible lens. If the number of microcysts persists, the wearing time will need to be reduced, i.e., from extended wear to daily wear.
Giant Papillary Conjunctivitis (GPC) – The subjective symptoms of GPC vary depending on the severity of the condition. Itching, especially following lens removal, and mucus discharge in the nasal corner of the eye in the morning are early diagnostic signs of GPC. Patients may also complain of increased lens awareness resulting in reduced lens wearing time. Although GPC usually affects both eyes, it is common for one eye to be at a more advanced stage than the other.
It is necessary to evert the upper lid and evaluate the upper tarsal plate using a slit lamp to determine the stage of the condition. In stage 1, the tarsal conjunctiva appears relatively normal with it velvety appearance and no observable papillae. The: only signs are the patient’s complaints of mucus discharge in the morning, and
itchiing on lens removal.
In stage 2, the early clinical stage, small papillae are observable and the patient is more aware of the lenses. Complaints of increased itching while wearing lenses and decreased wearing time should be expected.
In stage 3, the moderate stage, there is an observable increase in the elevation, size and number of papillae. Patients at this stage will experience increased itching and discharge, blurred vision from deposit formation, and decreased wearing time.
By stage 4, the severe stage, papillae can be 1mm or larger and should be observed with fluorescein to check for apical papillary scarring. There is severe mucus discharge resulting in heavy lens coatings that frequently cause superior displacement of the contact tens. Typically, the patient cannot tolerate the lenses and discontinues lens wear.
There are a number of factors that favor tile development of GPC. They include, lens deposition, extended wear schedules, infrequent lens replacement, genetic predisposition and seasonal peaks in airborne pollens and molds. Environmental factors such as air pollutants and chemical toxicity from lens care products can also contribute to the processes leading to GPC.
The approach for controlling GPC differs depending on the stage of the condition. In the early stages, the condition can often be managed by more frequent lens replacement with daily disposable the ideal option. Lens care products should be preservative free and in situations where disposal or frequent replacement lenses are not an option, enzymatic cleaners may be used two to three times a week. Managing the more severe stages may require temporary discontinuation of the lenses and the introduction of mast cell stabilizers such as Cromolyn 4% (Fisons) Alomide 0.1% (Alcon) and Acular 9.5% (Allergan). If the patient is in extended wear, the wearing time should be reduced to daily wear.
Blepharitis - One of the most under-diagnosed conditions involving contact lens intolerance is blepharitis. Patient complaints include itching, burning and irritated eyes accompanied with mild photophobia.
Blepharitis can be classified as either Seborrheic or Staphylococcal, although the two most commonly occur in tandem. The hallmarks of seborrheic blepharitis include a chronic moderate lid inflammation with an oily or greasy crusty appearance of the lid margins and lashes. Approximately one-third of the patients have dry eye symptoms and there is a frequent association with seborrheic dermatitis.
Staphylococcal blepharitis has a relatively short duration and the signs and symptoms can wax and wane. There is lid inflammation and dandruff-like colarettes, which form along the base of the lashes. Lash loss is common. Although patients are dermatologically normal, approximately 50 percent will have associated dry eye symptoms.
Treatment for blepharitis involves the use of hot compresses followed by lid scrubs at least twice daily. In some cases, topical antibiotics are necessary to resolve symptoms. In mild cases, daily disposable or frequent replacement of contact lenses are recommended to reduce deposit formation and improve long term with lenses.
Meibomian Gland Dysfunction - Patients complain of burning eyes, especially upon awakening. Since there is frequent association with seborrheic blepharitis and dry eyes, the symptoms can include itching and light sensitivity. The tears appear foamy with some, and Meibomian glands dilated and easily expressed while others are plugged and difficult to express. Treatment is similar for blepharitis; hot compresses lid scrubs and lid massage as many as four times a day. Topical antibiotics and in some cases, oral tetracycline may be necessary therapy.
Patients are often contact lens intolerant with dryness and lens deposits the primary problem. Daily disposable or frequent lens replacement systems may help to resolve some of the problems associated with lens deposits. Lens wear can usually be maintained on a daily wear basis provided symptoms improve with treatment.
Rigid Lens Complications-
A number of rigid lens complications may not be resolved through changes in rigid materials or lens design. Often the complications can be resolved with soft contact lenses. This is the perfect opportunity to introduce patients to daily disposable or frequent replacement systems. While waiting for the cornea to stabilize, the patient can be fitted in lenses that can be easily disposed of when the lens power needs adjusting. Wearing the lenses, the patient can experience the advantages of planned replacement lenses and can be easily convened into the new lens modality.
Examples of conditions in which rigid lens wear may need to be terminated include; persistent RGP lens adherence, 3 and 9 o’clock staining that can’t be resolved, and vascularized limbal Keratitis. The latter is a more advanced form of 3 and 9 o’clock staining, with vascularization of the peripheral cornea, localized around an elevated semi-opaque lesion on the epithelium. Of course, soft lenses should always be considered if patients are intolerant of rigid lenses.
Although this article discusses a number of complications that can be resolved with daily disposable or frequent replacement soft lenses, it is not our intent to suggest their use be limited to problem cases. In fact, nearly all our new soft lens ﬁts are placed in a daily disposable or frequent replacement lens modality with replacement programs from one day to three months, The advantages for the patient include less corneal and lid complications and a built-in backup system. With the daily disposable lens system, the complete elimination of lens care products is a major advantage for many patients.
For the practitioner, having satisfied patients and more options for achieving this goal is a major benefit. Offering these new modalities to your patients will reinforce your commitment to working with the latest technologies and referrals from satisfied patients will help your practice continue to grow.