Lesson 17 - Contact Lens Prefitting

Question 1

Contraindicate

Answer 1

A medical reason to a certain path of treatment should not be used given the patient’s circumstances.

Question 2

OCT

Answer 2

Ocular coherence tomography. It allows for very high-resolution images of the cornea, scleral, and conjunctival tissue, making scleral lens and hybrid fitting simpler. It is also used to obtain internal and external cross sections of the eyeball for measuring the thickness of the tear fluid under the lens and for measuring the thickness of the cornea, sclera, and edema, analogous to an ultrasound.

Question 3

Schirmer’s test

Answer 3

A common dry eye test for tear production. It measures the reflex tears from the lacrimal gland.

Question 4

Anterior chamber

Answer 4

The space between the back of the cornea and the front surface of the iris

Question 5

In order to optimize your patient’s success with contact lens wear, you should thoroughly evaluate your patient for any ____ or ____ issues that will cause potential problems wearing contact lenses. This will also help you to determine what?

Answer 5

In order to optimize your patient’s success with contact lens wear, you should thoroughly evaluate your patient for any predisposing health or lifestyle issues that will cause potential problems wearing contact lenses. Taking a thorough health history and collecting as much eye health data as possible will also help you to determine which contact lens types may be contraindicated for them as well as help you to figure out the best contact lens options for your patient.

Question 6

In discussing lifestyle with the client, you’ll want to discuss their what?

Answer 6

In discussing lifestyle with the client, you’ll want to discuss their occupation, environment, hobbies and personal hygiene, and wearing schedules.

Question 7

Lifestyle questions: occupations

Answer 7

First, some occupations can expose the patient to chemical fumes that can irritate the eye. For example, hair and nail salons, automotive mechanic shops, chemical refineries, construction workers, farm, textile, chemical industries, and welders have high exposure to irritations. Additionally, some job shifts are 12-hour shifts or more that can cause corneal overwear issues.

Question 8

Lifestyle questions: environments

Answer 8

Some occupational or living environments have very low humidity that can cause dry eye contact lens issues. Hospitals, clinics, computer areas, and labs as well as airplanes have low humidity environments with constant air conditioning that can dry the environment.

Question 9

Lifestyle questions: hobbies and personal hygiene

Answer 9

Hobbies and personal hygiene can play an important role in deciding someone’s candidacy for contacts. Smoking, poor personal hygiene, use of adhesives, or any products that produce fumes will cause contact lens wear problems. Water sports, boxing, and martial arts are contraindicated for scleral lenses.

Question 10

Lifestyle questions: wearing schedules

Answer 10

When contact lenses are approved for extended wear by the FDA, it does not mean that every person that wears these lenses will be successful wearing these contact lenses several hours or overnight. There are physical and environmental conditions that can alter a person’s ability to wear contacts lenses even though certain contact lenses perform better than others for extended wear. The doctor must assess the patient’s ability to wear contact lenses and their wearing schedule.

Question 11

In addition to lifestyle, there are a variety of medical risk factors to look for when assessing whether a client would be a good candidate for contact lens wear. You’ll want to be aware of what main points of a client’s medical history?

Answer 11

In addition to lifestyle, there are a variety of medical risk factors to look for when assessing whether a client would be a good candidate for contact lens wear. You’ll want to be aware of these main points of a client’s medical history: adnexa, medications, allergies, gender, age, motivation, measurements.

Question 12

Medical questions: adnexa

Answer 12

Adnexa is a Latin term that means “fasten to.” Therefore, it is used to describe parts throughout the body that are connected to organs. In terms of the eyes, it means the lids, lashes, conjunctival, and tear film. These will need to be assessed prior to contact lens wear. Good personal hygiene plays an important role in contact lens success. Hands and fingernails should be clean prior to handling any contact lenses. Clean lids and lashes are important, because they harbor bacteria that can infect the eyes especially for patients wearing soft contact lenses.

Question 13

Medical questions: medications

Answer 13

A healthy tear film and good tear quantity are essential for successful contact lens wear. The following medications can affect the tear film causing dry eye problems: antihistamines, diuretics, decongestants, hormones, certain antidepressants, dermatologic agents, pain relievers, antihypertensives, gastrointestinal medications, chemotherapy medications, and antipsychotic medications.

Question 14

Medical questions: allergies

Answer 14

Allergies and antihistamines will affect the tear film and the cornea integrity, causing dry eye.

Question 15

Medical questions: gender

Answer 15

Women can have more problems that can affect tear film and contact lens wear.

Question 16

Medical questions: age

Answer 16

Age tends to change the eyelid anatomy and lacrimal gland function to decrease tear film.

Question 17

Medical questions: motivation

Answer 17

As with anything, motivation plays a large part in whether your patient will be a successful contact lens wearer, be willing to learn to insert, remove, and if necessary, properly clean their lenses on a regular, ongoing basis.

Question 18

Medical questions: measurements

Answer 18

Consideration must be given to the patient’s measurements from keratometry readings, the topography of the cornea and tear film from the topographer, the patient’s prescription, and availability of current lens parameters.

Question 19

To wear contact lenses successfully, your patient’s eye health should first be evaluated to ensure that their eye is healthy enough to wear a contact lens. If the eye and eye area are not clean and healthy, wearing a contact lens could increase the risk for what?

Answer 19

To wear contact lenses successfully, your patient’s eye health should first be evaluated to ensure that their eye is healthy enough to wear a contact lens. If the eye and eye area are not clean and healthy, wearing a contact lens could increase the risk for an eye infection as well as vision and comfort issues.

Question 20

Assessment of ocular structures: adnexa

Answer 20

It is important to assess the adnexa and tear film quality. Assess the health status of the tears, amount of tears at the lower part of the lids, tear break-up time (TBUT), and tear gland. Look carefully at the lid margins for clogged oil glands or inflammation.

Question 21

Assessment of ocular structures: lid health and lashes

Answer 21

The lashes function to keep dust and small particles away from the cornea. The eyelids spread the tears across the cornea by blinking. Rule out pathologies of the lids and lashes.

Question 22

Assessment of ocular structures: cornea

Answer 22

Assess the health of the corneal layers. The endothelium layer is responsible for regulating the fluid across the cornea and keeping the cornea clear and transparent, important for contact lens wear. Some of the conditions that are contraindicated for regular cosmetic contacts include corneal endothelial degenerations, diabetes, and immunocompromised patients.

Question 23

Assessment of ocular structures: degenerations

Answer 23

Some corneal degenerations will cause corneal surface irregularities like scarring. Epithelial degenerations can cause wetting problems with the surface. Keratoconus is a progressive corneal disease where the cornea thins and protrudes forward. If the corneal curvature is very steep, it will require specific types of contacts.

Question 24

Assessment of ocular structures: limbus

Answer 24

The limbus is the junction between the cornea and sclera. Assess the limbal area and ensure it is healthy. If the contact lens is fit too tightly, it may affect the health of the limbal area. Measure the diameter, thickness, and study the topographical map to look for irregularities.

Question 25

Assessment of ocular structures: anterior chamber

Answer 25

The anterior chamber is the space between the back of the cornea and the front surface of the iris. If there is a problem with the fluid drainage through the anterior chamber, the pressure can build and cause a type of glaucoma. Glaucoma can interfere with contact lens wear because of the side effects of the topical medications that cause vision side effects.

Question 26

Assessment of ocular structures: posterior segment

Answer 26

The posterior segment of the eye consists of the posterior two-thirds of the eyeball. It includes the choroid, retina, vitreous humor, and optic nerve. Problems such as infection in this area will affect vision regardless of what type of contact lens is used.

Question 27

Assessment of ocular structures: crystalline lens

Answer 27

The lens is composed of fibrous elastic tissue that causes the lens to change in curvature during the process of focusing or accommodating, which is to focus at near distances.

The lens hardens over time until it can no longer accommodate after age 65. In addition, over time the lens can become cloudy from aging, certain systemic diseases such as diabetes, from UV exposure, and from certain medications. If a cataract is already present at the time the patient is being fitted for contact lenses, they will not be able to get optimal vision until the cataract is removed.

Question 28

Recall in a previous lesson, the topographer will allow us to view the status and health of ____, and it measures the ___ thickness and curvature on several points of the ___. Knowing the greatest and lowest elevations of the ___ will determine if you will choose what? It is also a useful tool for determining what?

Answer 28

Recall in a previous lesson, the topographer will allow us to view the status and health of the entire corneal surface, and it measures the corneal thickness and curvature on several points of the cornea. Knowing the greatest and lowest elevations of the cornea will determine if you will choose a soft spherical lens, a soft toric lens, a spherical gas-permeable lens, or other types of designs for your client. It is also a useful tool for determining lens flexure.

Question 29

If the keratometry readings show very steep or very flat curvatures, the topographer will show the extent of where the steep areas lie and how much of the cornea is involved. This should help us know if a ___ or ___ lens can be used or if a ____ or ____ lens is needed.

Answer 29

If the keratometry readings show very steep or very flat curvatures, the topographer will show the extent of where the steep areas lie and how much of the cornea is involved. This should help us know if a standard soft or gas-permeable lens can be used or if a specialized scleral or hybrid lens is needed.

Question 30

It is important to have enough ____ to support a contact lens on the eye. A healthy ____ allows for the eye to feel more comfortable throughout the day with a contact lens on; it decreases the risk for what while wearing contacts; and it reduces the risk for what?

Answer 30

It is important to have enough tears to support a contact lens on the eye. A healthy tear film allows for the eye to feel more comfortable throughout the day with a contact lens on; it decreases the risk for dry, red eyes while wear contacts; and it reduces the risk for an eye infection.

Question 31

Schirmer Test #1

Answer 31

With a topical anesthetic, a piece of litmus paper is inserted in the lower cul de sac of lower lid. If there is more than 10 mm of moisture on the litmus paper in 5 minutes, there is an adequate amount of tears being produced.

Question 32

Schirmer Test #2

Answer 32

Performed without anesthesia, this test is for measuring reflex tearing.

Question 33

Tear Break-Up Time (TBUT)

Answer 33

When Fluorescein is instilled in the tear film, we measure the time it takes for the tear film to evaporate while observing it using a slit lamp and cobalt blue filter. Typically a TBUT under 10 seconds is considered abnormal.

Question 34

Where to start to select the diagnostic lenses

Answer 34

Look at their prescription. Will it be a sphere, toric, or multifocal?

What wearing modality will work best? Single use? Two week?

Will you need a silicone hydrogel or a hydrogel lens?

Will you need a colored lens?

Look at the K readings and the diameter of the cornea.

You can consult the published contact lens parameters from your local distributor, go online to review a chart of contact lens parameters.

Chart of contact lens parameters: http://www.odspecs.com/misc.html

Question 35

Remember the soft contact lens parameter availability will change fairly often, so always check to make sure what?

Answer 35

Remember the soft contact lens parameter availability will change fairly often, so always check to make sure the design and powers you need are available before placing an order.

Question 36

Soft contact lenses usually come in diameters of about ___.

The base curves usually come as steep ___, and as flat as ___.

Answer 36

Soft contact lenses usually come in diameters of about 13.8-14.5 mm.
The base curves usually come as steep as 8.3 mm, and as flat as 9.0 mm.

Question 37

Spherical lenses come by manufacture how? What about toric and multifocal contact lenses?

Answer 37

Spherical lenses come prepackaged by the manufacturer, individually sealed in sterile saline.

Toric and multifocal contact lenses also come prepackaged; however, some toric lenses may be custom made by the manufacturer.

Question 38

Once you decide on the brand and type of lens you will try, you will need to remember that if their flattest K reading is greater than 46.00 diopters, that is a fairly steep cornea, so you should try what lens? If their flattest K reading is less than 41.00, that is a fairly flat cornea, and you should try what lense?

Answer 38

Once you decide on the brand and type of lens you will try, you will need to remember that if their flattest K reading is greater than 46.00 diopters, that is a fairly steep cornea, so you should try a steeper base curve lens like 8.3 or 8.4 (remember that the base curves are in mm and the K readings are in diopters). If their flattest K reading is less than 41.00, that is a fairly flat cornea, and you should try a flatter base curve like 8.8 or 9.0.

Question 39

If the diagnostic lens is too steep or flat, the lens won’t center well, may be uncomfortable, will cause fluctuating vision, and may fold in the eye or fall out of the eye. To begin, select the base curve closest to their what, and you will save fitting time?

Answer 39

If the diagnostic lens is too steep or flat, the lens won’t center well, may be uncomfortable, will cause fluctuating vision, and may fold in the eye or fall out of the eye. To begin, select the base curve closest to their flattest K, and you will save fitting time.

Question 40

We will discuss how to assess the fit in the upcoming lesson. You will need ensure that the diagnostic lens moves at least ___ with each blink, centers evenly over the ___, and vision is good. Also assess the patient’s comfort with the lens.

Answer 40

We will discuss how to assess the fit in the upcoming lesson. You will need ensure that the diagnostic lens moves at least .5 mm with each blink, centers evenly over the corneal limbus, and vision is good. Also assess the patient’s comfort with the lens.