Some factors contraindicate contact lens wear of any type, such as inflammation or disease of the anterior segment, any systemic disease that can be complicated by contact lens wear, poor hygiene, poor compliance, and lack of motivation (Table 11.1). Factors that may contraindicate soft lens wear include irregular corneas (i.e., keratoconus, ocular trauma), autoimmune disease, immunocompromised patients, chronic allergies, chronic antihistamine use, and giant papillary conjunctivitis (GPC, also known as contact lens papillary conjunctivitis [CLPC]).

The initial comfort afforded by soft lenses makes this lens type particularly appealing to patients.¹,² The initial comfort of soft lenses is due to the large diameter, thin edges, limited movement, and minimal resistance to lid closure.³ Potential contact lens patients often do not want to tolerate the adaptation period that may be present with GP lenses. In addition, the decreased initial reflex tearing and lens awareness help to reduce the time required for the practitioner to fit the lens. Likewise, the practitioner benefits from the ability to dispense new and replacement lenses from inventory.

Patient information to further consider when selecting soft lenses include refractive error, occupation, hobbies, wearing schedule, hygiene, and compliance. Typically, individuals with spherical refractive errors, low astigmatism, and lenticular astigmatism will be the best candidates for soft lens wear. These patients will be able to achieve acceptable visual acuity with a spherical or toric soft lens. Obviously, occupations with tasks that include exposure to fine particles of dust or mist (e.g., sandblasting) are not suitable for contact lens wear unless the recommended protective eye wear, such as safety goggles, is worn. Many occupations and hobbies may be enhanced by contact lens wear (e.g., those of athletes, actors, models, or politicians). These groups benefit from improved cosmesis and elimination of spectacle wear, which may decrease the field of view, fog up with precipitation changes, slide down, or possibly break. Soft lenses are preferable for athletes and sports activities as they are more difficult to dislodge than GP lenses. The minimal movement present with a soft lens aids in initial comfort; provides more stable vision, which may not be present initially with GP lens wear as a result of increased
lens movement; and reduces the likelihood of a trapped foreign body. Occasionally, patients desire lenses to wear strictly for sports, such as tennis or basketball, or just for social occasions to improve their appearance. Soft lenses are preferable for these part-time wearers. They are also advantageous for individuals desiring a change or enhancement of eye color as well as anyone benefiting from a disposable lens.

Soft lenses are more prone to deposits, and lens-wearing patients are more susceptible to infections than GP patients because of the characteristics of the lens. As a result, patients who exhibit poor hygiene, work in an environment that may be unsanitary or dirty (e.g., automobile mechanics, garbage collectors), or are noncompliant with their follow-up visits or care regimen are at risk to develop problems resulting from the contamination of their lenses. Extra caution is necessary for both the practitioner and the patient if these patients are to be fitted with any contact lens, in particular, a soft contact lens.

Other disadvantages of soft lenses are that some patients may experience reduced vision resulting from inadequate correction of refractive astigmatism, and the lenses are more fragile and more difficult to verify. Hydrogel lenses generally have lower oxygen transmission; however, silicone hydrogel lenses have higher or comparable oxygen transmission to GP lenses. Advantages and disadvantages are further summarized in Table 11.2.

Soft spherical lenses are available in powers of ±20 D, but most commonly the lenses are available in powers of approximately −10.00 to +4.00 D. If in doubt, it is important to check the power availability before fitting the lens. A smaller number of stock lenses and custom lenses are available in high plus, aphakic, and high minus powers. Toric lenses to correct for astigmatism are available in cylinder powers up to −1.75 or −2.25 D. Several lens brands and custom lenses are available in cylinder powers of −5.75 D or higher. Generally, the higher corrections are not available in a variety of materials, tints, or lens designs (i.e., bifocal).

Aspheric lenses, offered by several companies, may be beneficial for patients with low amounts of astigmatism (i.e., ≤ −0.75D). The lenses appear to improve spherical aberration, not correct astigmatism. Studies have shown that there is little difference between the spherical and aspheric lenses, although patients have reported subjective preferences for aspheric lenses.⁴,⁵

First-time wearers will generally benefit from a slightly thicker lens or one with an increased stiffness or modulus of elasticity. Both of these attributes help to make insertion, removal, and handling of the lens easier. Silicone hydrogel lens materials have a higher modulus than most soft contact lenses. Additionally, a handling tint will be beneficial for these patients.

Patients who experience frequent lens deposits, even when using a rigorous care routine, would be best fitted in a daily disposable lens. If this is not used, then a disposable or frequent-replacement
lens should be used (i.e., weekly to monthly replacement). Certain lens materials (i.e., Proclear and Preference by CooperVision and CSI by Ciba Vision) are more resistant to deposits. With the availability of disposable lenses, deposit issues should not be a problem if the patient is following the recommended replacement schedule.

Many contact lens wearers experience dry-eye symptoms with lens wear. As many as 50% of contact lens wearers have reported symptoms of dry eye.⁶,⁷,⁸ Factors that affect dry-eye symptoms are wettability, dehydration, contact lens solutions, poor tear film quality, environmental temperature, time of day, humidity, wind, and blink rate.⁶,⁹ In hydrogel lens materials, low-water-content and thicker lenses are thought to dehydrate less than high-water-content or thin lenses. This is thought to be the one of the reasons why patients are more comfortable in low-water-content, thick hydrogel lenses. However, a fixed relationship between initial water content and dehydration cannot always be demonstrated.⁹ Additionally, some studies have shown that increasing the lens thickness has a greater effect on dry-eye symptoms than the water content.¹⁰

Recent advances have given practitioners more lens options to aid marginal dry-eye patients. Extreme H₂O (Hydrogel Vision Corp) is a hydrogel lens that the manufacturer claims retains its water saturation on the eye, thus exhibiting less dehydration and better end-of-the-day comfort. Proclear (CooperVision), mentioned previously, is deposit resistant and contains phosphorylcholine, which aids in hydration of the lens.¹¹ Focus Dailies with AquaRelease (Ciba Vision) and 1-Day Acuvue Moist (Vistakon) contain lubricating agents incorporated into the material, which reportedly make the lens more wettable and increase comfort, particularly end-of-the-day comfort. The lubricating agent in Focus Dailies with AquaRelease is polyvinyl alcohol (PVA), and the agent in 1-Day Acuvue Moist is polyvinyl pyrrolidone (PVP). In the Dailies lens, the lubricating agent is released from the lens during wear, whereas in the Acuvue lens, the agent is not released. Study data comparing these lenses to their predecessors and to each other are few and results appear variable regarding how much impact they have.⁶ However, they do provide an option to the patient, and after a trial period, the patient may determine whether he or she detects improvement. Another benefit of daily disposable lenses is that no solutions are necessary, eliminating preservative sensitivities.

Silicone hydrogels have demonstrated increased comfort for dry-eye patients.¹²,¹³ This may be because of increased oxygen transmission, decreased water content, and internal wetting agents and natural wettability of some of the lens materials.

Besides trying to find the best lens material for a marginal dry-eye patient, the choice of a care system is important. Hydrogen peroxide is beneficial, especially to patients sensitive to a preserved solution. With the newer preservatives, sensitivity symptoms are more subtle, manifesting in dryness, decreased wear, and superficial staining. Many dry-eye symptoms may be caused by one-bottle lens care symptoms or coated lenses.¹⁴ A good first step is to use a nonpreserved hydrogen peroxide care regimen. In addition, there are some chemically preserved solutions that are reported to increase comfort and decrease dryness. If hydrogen peroxide is not beneficial to the patient, the use of one of these solutions should relieve dryness symptoms. In addition, lubricating drops can be used to rehydrate and rinse the lens in the eye.

Only certain lenses are approved by the Food and Drug Administration (FDA) for therapeutic use (sometimes called bandage lenses). Close monitoring and frequent replacement are required. Silicone hydrogel lenses with high oxygen permeability (Dk) that are FDA approved for therapeutic use are Focus Night and Day (Ciba Vision), PureVision (Bausch & Lomb), and
Acuvue Oasys (Vistakon).¹⁵ Conditions that warrant the use of a therapeutic contact lens include corneal erosions, chronic epithelial defects, bullous keratopathy, mechanical trauma, dry eyes, and filamentary keratitis. Therapeutic lenses are also used following ocular surgery, to aid in sealing a corneal wound, and for drug delivery. Therapeutic lenses should not be used in the presence of an active ocular infection, in filtering blebs, or for patients who will not return for follow-up evaluation.¹⁶

Obviously, a patient presenting with a serious ocular or systemic disease is not a good candidate for contact lenses, other than those approved for therapeutic use. For example, diabetic patients are at risk when fitted with soft or GP contact lenses because of a decreased wound-healing ability. However, studies have shown that diabetic patients can successfully wear daily-wear (DW) lenses if carefully monitored.¹⁷ For those patients with some form of ocular compromise (i.e., staining, papillary hypertrophy, deficient tear quality), DW is indicated because prolonged lens wear, such as extended wear (EW), may increase these symptoms. Additionally, daily disposable lenses should be considered for these patients.

Children fitted with a soft lens may experience difficulty inserting the large lens diameter. A few lenses are available in smaller diameters (i.e., 13 mm), and this may aid in lens insertion. Most children who are motivated to wear a soft contact lens will be able to learn to insert and remove the contact lens. If the contact lens is considered medically necessary (i.e., aphakia, anisometropia) and the child is too young to perform insertion and removal, the parents may be taught to insert, remove, and care for the lens. There are many contact lenses to use with children that have a 13.8-mm diameter. In addition, disposable lenses are a good modality for children to provide a cost-efficient lens, to be used as spare lenses, and to decrease the complications of lens care.

Presbyopes may have difficulty viewing the lens when inserting, removing, or caring for it. A visibility tint or a cosmetic tint is beneficial to these patients when handling the lens. Additionally, they may appreciate a slightly thicker or higher modulus lens, which is easier to handle.

A lens material with high oxygen transmission (Dk/t) is required for aphakic patients. Generally, these lenses are silicone based, available in limited parameters, and very expensive. O2 Optix Custom (Ciba Vision) is a quarterly replacement silicone hydrogel lens that is available in aphakic powers of +10 to +20 D. It has a Dk/t of 117 at −3.00 D. This lens is more affordable than most conventional specialty lenses and provides frequent replacement. (See Chapter 17 for more information.)