Ординатура / Офтальмология / Английские материалы / Contact Lenses in Ophthalmic Practice_Mannis, Zadnik. Coral-Ghanem, Kara-Jose_2003
.pdf220 C. Coral-Ghanem and M.D. Bailey
wearer may benefit from wetting agents, especially if the wetting agents are instilled several minutes prior to contact lens removal. While wetting is not an absolutely necessary step in contact lens care, it may contribute substantially to the success of contact lens use.
33.What are the steps for contact lens maintenance?
Step 1: Cleaning the Contact Lens Case
The case must be cleaned at least once a week with hot water and soap. The case should then be air dried, and after drying, kept closed. In general, disposable cases are recommended, and cases should be replaced at least every 6 months. Materials that foster the growth of microorganisms can accumulate in contact lens cases, and contamination may occur from the user’s fingers or from a dirty contact lens. It has been demonstrated that in cases of ocular infection the pathogens identical to those that caused the infection are frequently found in the contact lens case or under the fingernails of the user. Such contaminated contact lens cases may be the vector for ocular infection.
Step 2: Hygiene of Hands, Eyes, and Ocular Adnexa
Prior to inserting a contact lens, wearers should wash their hands with soap to remove foreign material, grease, nicotine, and contaminants that may damage the contact lens or infect the eye. Soaps with antiseptic cream, chemical deodorants, or strong fragrances should be avoided because these substances can be inadvertently instilled in the eye during transfer of the lens. The hands should be dried on lint-free towels, and nails should be kept clean. It is also important to remove contact lenses prior to using creams/cleansers to clean eyelid margins and eyelashes.
Step 3: Cleaning
Wearers should use a cleaning solution that contains detergent substances that are indicated for their type of contact lens. These solutions are not effective for the removal of proteins. The excessive friction that is required to remove proteins from contact lenses may produce scratches or grooves in the hydrophilic lens or may deform the rigid gas permeable lens. For this reason, wearers should use enzymatic cleaners, which specifically remove proteins, in addition to the cleaning solution.
Step 4: Rinsing
Rinsing is indicated to remove loose deposits and cleaning solution from the surface of the contact lens. With the contact lens in the palm
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of the hand, the user should direct a stream of solution at the lens, either multiuse solution or saline, lightly rubbing the lens surface back and forth. A second rinse without rubbing is then performed. Some solutions permit placement of the lens in the eye without rinsing.
Step 5: Disinfection
After cleaning and rinsing, the contact lens should be placed in a disinfectant to eliminate pathogenic microorganisms. Some systems use a separate solution for this step. In multipurpose solution systems, the same solution is used for both steps. Wearers usually place their lenses in the disinfecting solution overnight.
Step 6: Neutralization
Neutralization is necessary for strong disinfectants that may irritate the eye. For example, hydrogen peroxide solutions are neutralized during the disinfection step.
Step 7: Wetting
Wetting drops are used before insertion of the contact lens, during contact lens wear to alleviate symptoms of dryness, and to aid in removing a contact lens.
34.What should guide the professional in indicating to the user the correct method of cleaning and disinfection?
The following factors should be taken into consideration:
Contact Lens Material
All forms of disinfection can be used with low-water-content contact lenses.
With high-water-content lenses, one can use all forms of disinfection except thermal disinfection.
Contact Lens Type
Hydrophilic contact lenses that are not frequently changed require the use of specific solutions such as daily surfactant and weekly enzymatic cleaning. Contact lenses that are exchanged every 3 months or more frequently can be managed with multiuse solutions, especially in wearers who do not have a tendency to form deposits.
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Tear Film Deficiency/Blepharitis
Patients with tear film deficiency have a greater propensity to have preservative reactions and may be more susceptible to deposit formation. Patients with dry eyes and/or blepharitis frequently have a higher lipid level in the tear film. For this reason, they should use an enzymatic cleaner that contains lipase.
Use of Systemic or Ocular Medication
Antihistamines
The antihistamines have various degrees of effects, similar to atropine, including the tendency to alter tear film integrity.14,15 Their use can unmask clinically significant dry eye that would otherwise remain subclinical.
Isotretinoin
The use of isotretinoin shortens tear breakup time as the result of a decrease in the secretion of lipid from the meibomian glands.16,17 This drug may cause dry eye symptoms, and 20% of isotretinoin and 8% of contact lens wearers present with symptoms of contact lens intolerance.16
Beta Blockers
A reduction in lacrimal secretion can be related to the collateral effects of beta blockers, administered either systemically or topically. Propranolol, practolol, timolol, and various others may be related to dry-eye symptoms.18–20
Birth Control Pills
The use of birth control pills has been anecdotally associated with contact lens wear problems. There are no studies that prove the effect of contraceptive agents on contact lens intolerance. The possible etiologic mechanisms include alteration of tear production and an induced change in the corneal curvature.21,22
Aspirin
Aspirin that is taken orally may be excreted in the tear film and absorbed by a hydrophilic contact lens, producing epithelial defects.23,24
Anticholinergic Drugs
Atropine and related drugs may cause drying of the mucous membranes. Scopolamine and certain other antinausea medications may produce dry eye symptoms and difficulty using contact lenses. Other drugs with possible anticholinergic activities, such as phenothiazines,
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anxiolitic agents, and tricyclic antidepressants, have been associated with dry eye and contact lens intolerance.25
Work Environment
Wearers who work in a polluted work environment may require specific solutions to maintain contact lens hygiene. The practitioner may also suggest daily disposable lenses.
History of Allergy
In patients with allergies, 3% hydrogen peroxide or thermal disinfection may be the best answer, as these patients may be more likely to develop sensitivity to chemical cleaners and preservatives.
Practicality and Cost
The best maintenance and care plan for wearers is the one that has the greatest probability of being followed. If they feel the cleaning procedures are impractical or if the system is too costly, they may be less likely to adhere to proper cleaning and maintenance.
35.How should rigid gas permeable lenses be maintained?
Maintenance of the rigid gas permeable (RGP) lens should include either specific solutions or multiuse solutions. Specific solutions include products such as Duracare and Totalens (Allergan), Opti-Soak (Alcon), and Optimum (Lobob). Multiuse solutions include products such as Boston Simplicity (Bausch & Lomb) and Unique-pH (Alcon). The RGP lens may form the same types of deposits as hydrophilic lenses but usually to a lesser extent. Microorganisms easily adhere to a contact lens with deposits. A clean lens makes it difficult for these organisms to adhere as easily.
Steps to follow include:
1.Hand washing, avoiding soaps with perfume or creams.
2.Handling the contact lenses right to left, in the same order always, to avoid switching the contact lenses.
3.Placing of two or three drops of cleaning solution on the surface of the contact lens, wetting the lens completely.
4.Gently rubbing each side of the contact lens in the palm of the hand, back and forth for approximately 20 seconds, with the concave surface up.
5.Complete rinsing with multiuse solution or saline, avoiding tap water.
6.Disinfecting with specific or multiuse solutions, and placing the con-
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tact lens in a storage solution and disinfectant for 4 hours or for the entire night. The wearer should use new solution each night and should make sure that the contact lens is completely submerged.
7.Rinsing with multiuse or saline solution prior to inserting the contact lens.
8.Placing wetting drops on the contact lens prior to inserting it in the eye.
9.Emptying the storage case, rinsing it, and drying it while open.
The following steps are recommended in addition:
1.Always clean the contact lens immediately after removal from the eye.
2.Use very light rubbing action during the cleaning. Significant pressure on a RGP lens can cause damage and modify the parameters of the lens. This is particularly important for wearers who have switched to RGP lenses from PMMA lenses, as the RGP lens is more fragile.
3.The RGP contact lenses should not be rubbed between fingers, because they may be broken or deformed in this manner.
4.Thermal disinfection should not be used.
5.When an RGP contact lens is being used on an extended wear basis, it should be removed at least once a week for cleaning and disinfection.
6.To remove proteins, the wearer should use an enzymatic cleaner daily or enzyme cleaner in the pill form once per week.
7.Contact lens solutions should not be used after the expiration date. Extra rigid contact lenses should be stored dry and clean, in a container that is also dry and clean. Prior to using an RGP lens that has been in dry storage, it is recommended that the RGP contact lens be placed in conditioning/disinfecting solution for at least 4 hours to increase comfort.
36.How should rigid contact lenses be inserted and removed?
The wearer should be given the following instructions:
1.Close the drain in the sink or place a clean paper towel over the drain prior to handling a contact lens to avoid loss of the lens.
2.Wash the hands to remove dirt and microorganisms that may accumulate on the contact lens and cause ocular irritation or infection. Dry with a lint-free towel.
3.Rinse the lens with multiuse solution or sterile saline to remove traces of dirt, lint, and other particulate material. If foreign bodies adhere to the contact lens at the time of insertion, it may cause ocular discomfort.
4.Place the contact lens on the index finger of the dominant hand. With the middle finger of the other hand, lift the upper lid at the lashes. The middle finger of the dominant hand is then used to pull the inferior lid down (Figure 21.1).
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Figure 21.1. Correct technique for bimanual insertion of a rigid contact lens.
5.Using a mirror on a table and looking directly at the contact lens, the wearer can then place the contact lens on the cornea. After placement of the lens, the wearer may then release the eydids, first the inferior and then the superior lid.
Removal Method 1
1.Open a towel and place it on the table in order to avoid losing the contact lens.
2.Use the index finger of the right hand to remove the contact lens from the right eye and of the left hand to remove the contact lens from the left eye. The finger is placed at the junction of the lateral border of the lid (Figure 21.2).
3.Open the eyes wide and pull the lids to the side. At the same time, blink, looking straight ahead, to eject the contact lens. This procedure can be performed with either the index finger or the thumb of the same hand. The other hand can be positioned below the eye to catch the contact lens.
Removal Method 2
This method uses both hands for removal. The most important factor is grasping the contact lens between the lid margins to push the lens out with a blink.
1.Grasp the inferior lid with the dominant hand and the superior lid with the other.
2.Apply pressure with two fingers in the direction of the center of the eye at the edge of the contact lens (Figure 21.3).
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Figure 21.2. Traction on the lateral canthus for removal of a rigid contact lens.
3.The lid margin may evert, making it difficult to remove the contact lens if the lid is pressed incorrectly (Figure 21.4).
Removal Method 3
1.Grasp the suction cup with thumb and forefinger of the dominant hand.
2.Grasp the upper lid with the index finger of the other hand.
3.Look straight ahead, using a mirror.
4.Touch the suction cup to the surface of the contact lens. The suction cup will cling to the contact lens, facilitating removal (Figure 21.5A and B).
Wearers with poor palpebral tone, problems with lid margin position, and/or contact lenses of large diameter may have more success with methods 2 and 3.
37.How should gas permeable lenses be stored?
Steps in storage are as follows:
1.Wash hands with a neutral soap and dry on a lint-free towel.
2.Clean the contact lens case.
3.Remove the contact lens from the eye and place it in the palm of the hand.
4.Use the right hand to manage the right lens and the left hand to manage the left lens, to avoid switching the lenses.
5.Place two or three drops of cleaning solution on each surface of the contact lens, covering it completely.
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Figure 21.3. Alternate method for rigid contact lens removal using both hands to grasp the contact lens between the lid margins. Slight pressure on the lower lid will tilt the lens forward and away from the cornea.
6.Gently rub each side of the contact lens with the index finger for 20 seconds.
7.Rinse with multiuse solution or saline for 10 to 20 seconds.
8.Place the contact lens in a clean case, and before closing it, check to be sure that the edge of the lens is not caught in the top of the case.
9.Disinfect the contact lens.
10.Check to be sure that the contact lens is not everted before placing it on the eye.
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Figure 21.4. Incorrect method of manipulating the lower lid causing eversion of the lid.
The following practices are strongly recommended:
1.Always clean and disinfect the contact lens after removal from the eye. This applies to all types of contact lenses, including disposable contact lenses.
2.Avoid rubbing a dry contact lens, because at the time of removal there may be particulate matter on the lens that can scratch the surface during the cleaning process.
3.Check the expiration date of the solution.
4.If cleaning the contact lens becomes difficult, consider the use of ultrasonic cleaning.
38.How should a hydrophilic contact lens be inserted and removed?26
Step 1
Follow steps 1 through 3 described above for insertion and removal of an RGP lens.
Step 2
Examine the lens to be sure that it is clean and moistened without cracks or particulate matter. Then place the lens on the tip of the index finger and look at it against a bright light. If the lens appears damaged or dry, it should not be placed in the eye (Figure 21.6).
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Figure 21.5. A: Correct placement of the suction cup. B: Removal of the rigid contact lens with the suction cup.
Step 3
Check to make sure that the contact lens is right side up. When placed in the eye inside out, it is uncomfortable, moves excessively, and may not provide good vision. To determine if the contact lens is inside out, place it on the tip of the index finger against a light, and look at the shape of its borders. If it is correctly oriented, the shape should be similar to that shown in Figure 21.7A. If inverted, it will appear as in Figure 21.7B.
As demonstrated in Figure 21.8A, if the edge of the lens forms a round arc when positioned on the tip of index finger, it is correctly