Indications and Contraindications for Contact Lens Wear

Question 1

Advantages of Myopia in Contact Lens Wear

Answer 1

Minus lenses have a minimizing effect when placed in front of the eye. The minimizing effect is impacted by vertex distance, contacts eliminate this unwanted effect.

Question 2

Disadvantages of Myopia in Contact Lens Wear

Answer 2

Typically occur if they are an emerging presbyope. A minus lens is apex to apex, when a person looks through lenses to read they are looking through base in prism. This assists in the accommodative process. High minus patients may need readers when using contacts.

Question 3

What is the Jack in the Box effect in regards to hyperopia?

Answer 3

The prismatic effect of an aphakic lens will create a blind spot for the patient in which images will appear and disappear when the line of sight is changed from the periphery to the direct line of sight.

Question 4

What factors impact the amount of magnification that a spectacle lens would have?

Answer 4

Thickness, curvature, vertex distance, and the materials index of refraction.

Question 5

Why is the field of view in higher powers limited by corrective lenses?

Answer 5

The clearest portion of the lens is stagnant within the frame, and the eye moves behind it. Since a contact lens has an optical zone that is designed to cover the pupil and track the movement of the eye, vision is not compromised when looking at different fields of view.

Question 6

What is “With the Rule” Astigmatism?

Answer 6

1. Steeper curve at the vertical meridian (90 degrees +/- 30 degrees)
2. K readings would be 44/43 @ 180
3. More common with myopes and younger patients
4. RX -3.00 -1.00 x 180M
5. Most common type

Question 7

What is “Against the Rule” Astigmatism?

Answer 7

1. Steeper Curve at the horizontal meridian
2. K reading would be 42/41 @ 090
3. More common in older individuals
4. RX -2.00 -1.50 x 090

Question 8

What is “Oblique” Astigmatism?

Answer 8

1. Curves are at an angle to the horizontal or vertical meridian (45 or 135 degrees)
2. Axis would be between 30 and 60 or 120 and 150
3. K reading would be 42.50/44.50 @ 040
4. RX -4.00 -2.25 x 055

Question 9

Corneal Astigmatism

Answer 9

The astigmatic effect is due to an uneven bending of light created by different meridians of the cornea.

Question 10

Lenticular Astigmatism

Answer 10

The astigmatic effect due to an uneven bending of light from the crystalline lens. Cannot be corrected with a spherical and lacrimal lens. Is indicated if the amount of astigmatism in the “K” readings is different than the amount indicated by the RX.

Question 11

How do contact lenses help anisometropia patients?

Answer 11

If there is a difference between the two eyes of more than 5.7%, the brain may have difficulty fusing the two images together. In children this results in visual suppression and in adults it results in double vision. Contacts minimize this disparity due to the placement on the eye.

Question 12

Indications for Contact lenses: Irregular Astigmatism

Answer 12

Irregular astigmatism is created by disease or scarring and it creates power meridians that are not 90 degrees apart. Due to the irregularity, glasses cannot meet the visual needs of the patient. A hard contact lens and the lacrimal lens should be used because the tear film will create a smooth refractive surface and prevents light scattering on the uneven corneal surface.

Question 13

Indications for Contact Lenses: Corneal Disease/Damage

Answer 13

Soft Contacts can be used as bandage lenses. A lens can act as a barrier between the epithelium and the eyelid to promote healing and promote pain relief.

Question 14

Indications for Contact Lenses: Keratoconus

Answer 14

Keratoconus is a steepening and thinning of the cornea that causes an asymmetrical cone to develop. It is managed through hard contacts. The cause is unknown but may be hereditary.

Question 15

Early Stages of Keratoconus

Answer 15

1. increased myopia and astigmatism
2. Photophobia
3. Sensitivity

Question 16

Advanced Stages of Keratoconus

Answer 16

1. Corneal bulge with downward gaze (Munson’s)
2. Scissoring with retinoscopy
3. Fleischer’s ring, iron deposits form along the base of the cone that creates a brownish green ring
4. Striae (White stress lines)
5. Scarring

Question 17

Indications for Contact Lens Wear: Pigment and Iris Disorders

Answer 17

The loss of pigment can create a scattering of light inside the globe, resulting in poor visual acuity. A specialized contact with an iris painted on the lens will improve the acuity of this patient.

Question 18

Ocular Indications: Eyelid

Answer 18

1. Healthy with good elasticity
2. Free of Abnormal secretions
3. No to minimal signs of blepharitis
4. Free of styes or gland dysfunction

Question 19

Ocular Indications: Tear Film

Answer 19

1. Tear break up time is greater than blink time
2. A lacrimal lake that is sufficient for tear exchange
3. Satisfactory tear production

Question 20

Ocular Indications: Conjunctiva

Answer 20

Look for disruptions on the surface that could be aggravated by contact wear, such as follicles, discharge, abnormal coloring and growths.

Question 21

Ocular Indications: Cornea

Answer 21

1. Free of inflammation and infection
2. Previous damage and scarring should be noted.

Question 22

Common lifestyle indications for contact lens wear

Answer 22

1. Contact sports
2. Working extremes in temperature so eyewear does not fog
3. Moving indoors and out so the patient can wear sunglasses

Question 23

Common lifestyle contraindications for contact lens wear

Answer 23

1. Dusty environments
2. Tasks that require a lot of accommodation
3. Occupations and hobbies that require the use of spray chemicals.
4. Water Sports (increased risk of acanthamoeba keratitis )

Question 24

Medical Contraindications for contacts: Acne

Answer 24

For patients on Accutane, contacts can cause dry eye and ocular sensitivity.

Question 25

Medical Contraindications for contacts: Allergies

Answer 25

Concerns for reactions to preservatives, materials and deposit build up. Antihistamines can also case palpabrae conjunctivitis

Question 26

Medical Contraindications for contacts: Auto Immune Disorder

Answer 26

Concern for ocular inflammation and dry eye. Most immune disorder medications make dry eye worse.

Question 27

Medical Contraindications for contacts: Congestive Heart Failure

Answer 27

The medication Digoxin can alter color vision and decrease visual acuity, lid and conjunctival inflammation and mydriasis.

Question 28

Medical Contraindications for contacts: Depression

Answer 28

Benzodiazepines can cause photosensitivity and decreased light response and mydriasis, ocular irritation and decreased visual acuity.

Question 29

Medical Contraindications for contacts: Diabetes

Answer 29

Concern is reduced healing, decreased corneal sensitivity, and dry eye.

Question 30

Medical Contraindications for contacts: Hormone Changes

Answer 30

Concern is dry eye, decreased corneal sensitivity and changes in corneal shape. HRT and birth control can also increase corneal edema

Question 31

Medical Contraindications for contacts: Hypertension

Answer 31

Beta Blockers and Diuretics can cause dry eye and lid inflammation, photosensitivity and increased straining.

Question 32

Medical Contraindications for contacts: Gastro-Intestinal

Answer 32

Donnatal can cause blurred vision from accommodation loss

Question 33

Medical Contraindications for contacts: Psychosis

Answer 33

Concern would be contact lens adaption, and antipsychotics can cause dry eye.

Question 34

Medical Contraindications for contacts: Respiratory

Answer 34

Concern is chronic inflammation, photophobia, lacrimal debris discharge, burning, itching and tearing.

Question 35

Medical Contraindications for contacts: Skin disorders

Answer 35

Excessive Deposits, lid irritation, blepharitis, punctate keratitis.

Question 36

Medical Contraindications for Contacts: Thyroid Dysfunction

Answer 36

Can cause poor blinking, dry eye and bulging globe. Makes it difficult for the lens to stay on the eye.