Pacific University College of Optometry

What is
Optometry?

Information for
Patients

Academic
Programs and
Admissions

Student
Resources

Catalog and
Calendars

Outside the
Classroom

PACIFIC UNIVERSITY College of Optometry: Contact Lenses

Contact lens services available at the Pacific University College of Optometry Family Vision Centers include: the fitting and management of contact lenses for refractive conditions such as nearsightedness, farsightedness, astigmatism, and presbyopia. Each of these conditions can be treated with a variety of lens types and materials.

Hydrogel (Soft) Lenses:

This type of contact lens is relatively soft and flexible, which allows it to drape over the entire surface of the cornea like a blanket. Soft lenses are composed of complex plastic polymers combined with a 38-74% water content. Advantages of this type of lens include disposability, shorter adaptation time, an ability to enhance or change eye color and a reduced possibility of dislodging from the eye in comparison to the rigid gas permeable lens.

Rigid Gas Permeable Lenses:

These lenses are relatively smaller in comparison with the soft lens and float on top of the tear layer of the cornea. RGP's are composed of a low flexure plastic polymer with a water content of <2%. This type of lens offers high optical quality, superior ocular health, easy care regimen, and durability.

Correction of Astigmatism:

Astigmatism includes refractive conditions in which the optical system of the eye cannot create a single point image on the retina from a single point object in real space. This situation usually arises when the cornea has meridional curvatures which are unequal. Toric soft contact lenses, as well as rigid gas permeable lenses can be used to compensate for this condition.

Correction for Presbyopia:

As the eye ages, it slowly loses the ability to focus on objects held at arms length or closer. Patients who are becoming presbyopic may want to consider the use of contact lenses (RGP or hydrogel) instead of spectacles. Several management strategies can be used in the correction of presbyopia.

Monovision: The most common type of correction for presbyopia with contact lenses involves two different lens powers for each eye. One eye is corrected for distance viewing and the other eye is corrected for near viewing.

Bifocal Contact Lenses: The design of bifocal contact lenses is similar to that of spectacle bifocal lenses. Some lenses contain a visible segment area for near viewing, while others incorporate the progressive or no-line design. Selection is based upon the type of lens which will provide the patient with stable and comfortable vision specific to his or her needs.


bifocal contact lens	bifocal contact on the eye

Wearing Schedules:

The amount of time the lens is worn each day and the frequency with which it is replaced is dependent upon many factors, such as patient convenience and compliance with lens care regimen. Realistic patient expectations about lens performance and the maintenance of good ocular health are among the primary goals for successful contact lens management.

daily wear: With this schedule, the lenses are worn for an average of 12 hours per day and then removed at night. After removal, the lenses are cleaned and disinfected before re-insertion the following morning.

extended wear: These lenses are worn overnight for 1-6 consecutive nights in select cases. Soft lenses in this category are generally thinner or have a higher water content(>60%) than normal daily wear lenses. This wearing schedule can create a greater risk (8 times greater compared to the daily wear schedule) of infections, including sight threatening corneal ulcers. RGP's possessing above average oxygen transmission can also be used on an extended wear basis. RGP's are less likely to cause eye infections than soft lenses when worn on an extended wear schedule.

corneal ulcer

disposable lenses: Disposable lenses are designed to be thrown away upon removal rather than cleaning and disinfection before re-insertion. A new lens is used each time one is removed. This can be an advantage since the amount of time spent by the patient on the care of the lenses is reduced. 1-day and extended wear lenses fall under this category.

frequent or planned replacement lenses: This category includes 1-week, 2-week, 1-month, 2-month, 3-month, and 6-month lenses. These lenses must be cleaned and disinfected upon removal before re-insertion. Planned or frequent replacement schedules can be beneficial for patients who experience comfort and vision problems created by excessive lens deposits, typically protein build-up. The insertion of a fresh lens can relieve these symptoms as well as reduce the potential for inflammation or infection.

SPECIALTIES:

Cosmetic:

These lenses are used to enhance or change eye color are available for occasional use as well improved cosmesis in patients with ocular trauma.

handling tints: This type of tint allows the patient to see the lens inside the lens case and aids in the prevention of losing the lens. However, these lenses do not change or enhance eye color. This tint, sometimes referred to as a visitint, is available in RGP and hydrogel lens styles.

enhancing tints: This tint is transparent and allows the patient to deepen or emphasize their natural eye color. This is most effective with lighter eye colors such as blue, green, and gray.

opaque tints: If a patient desires to change their eye color completely, then they would need to select an opaque tint. Results can vary depending upon individual pigment density of the iris.

examples of opaque tinted lenses

Therapeutic:

Treatment of certain patients with corneal dystrophies or defects such as keratoconus may involve the use of specific hydrogel or RGP lens styles. Post-surgical and post-trauma patients can also benefit from contact lenses designed for their specific needs.

Opaque contact lenses can be used as an alternative for patching in vision therapy. Patients with iris abnormalities from trauma or congenital forms like anirida can benefit from contact lenses which artifically simulate the pupil.

keratoconus: This is a non-inflammatory, self-limiting corneal disease involving progressive thinning, steepening, and distortion of the cornea. The resulting loss of optical quality in the cornea is improved best with RGP lenses especially designed for the patient.

corneal distortion caused by keratoconus

post-surgical: Patients who have had refractive surgery such as RK, PRK, and LASIK may need to improve their vision to a more desirable level with contact lenses in select cases. For patients who have had non- refractive surgery, such as a corneal transplant, a contact lens may serve to enhance vision as well as ocular health.

post-trauma: Corneal defects (such as abrasions, recurrent erosions and lacerations) caused by the introduction of a foreign body or substance into the eye may be managed with the use of contact lenses.

corneal lacerations closed with sutures

Appointments for contact lens exams can be scheduled with one of the clinics listed below.

CLINICS
Portland
Forest Grove
Southeast Portland
Northeast Portland

REFERENCES:
Bennet ES, Weissman BA, eds. Clinical Contact Lens Practice. Philadelphia: JB Lippincott, 1994.

Bennet ES, Vinita AH, eds. Clinical Manual of Contact Lenses. Philidelphia: JB Lippincott, 1994.

Buehler PO, Schein OD, Stamler JF, Verdier DD, Katz J. The increased risk of ulcerative keratitis among disposable soft contact lens users. Arch Ophthalol 1992;110:1555-8.