Objective 3

Question 1

What are possible causes for the types of corneal staining patterns shown in the graphic below?

Answer 1

Deposits on the posterior lens surface
Foreign body trapped behind lens (i.e. dust or sand, cosmetics and applicators) Insertion abrasions

Question 2

If a patient presents in your office and under slit lamp examination the corneas appear as in the graphic below, what is the problem and what would you suspect the cause to be?

Answer 2

Diffuse superficial punctate keratopathy caused by solutions

Question 3

If a patient exhibits signs of dimple veiling, corneal steepening, edema, staining and edge compression, what type of fitting problem would be indicated?

Answer 3

A tight fit

Question 4

Name at least four modifications that could be made to help with the fitting problems in Question #1 ( A tightfit causing dimple veiling, corneal steepening, edema, staining and edge compression)

Answer 4

Flatten base curve
Reduce diameter
Flatten or widen peripheral curves

Blend peripheral curves

Question 5

What modifications could you perform on a lens that frequently decenters?

Answer 5

Increase the total diameter of the lens.

Use a toric lens design.

Use a spherical lens fit steeper than K.

Question 6

If a patient shows signs of three & nine o’clock staining, positioning the lens superiorly will help the problems. Name three modifications or design changes you could make to accomplish this.

Answer 6

Increase lens diameter

Flatten lens cornea relationship

Change to toric lens design

Question 7

What modifications could you make to a lens that has caused corneal edema?

Answer 7

Flatten BC

Flatten peripheral curves

Reduce diameter

Question 8

List six modifications or lens design changes that can be made to rectify the problem of a high riding lens.

Answer 8

Decrease total lens diameter

Increase total lens diameter

Decrease edge thickness

Increase center thickness

Use prism ballast design

Make lens/cornea relationship flatter

Question 9

If a patient exhibits signs of adhesion phenomenon, what modifications would be appropriate?

Answer 9

Increase center thickness
Decrease O.Z. and/or overall diameter re-roll edges

Question 10

What could be done to help eliminate the corneal staining patterns shown in the graphic?

Answer 10

Polish posterior surface of the lens

Re-instruct patient on insertion & removal

Ask patient to try to eliminate or change environmental concerns and habits such as dust and cosmetics

Question 11

What are three methods of correcting residual astigmatism of 0.50 D or more?

Answer 11

Fit with spherical rigid lenses and have patient wear glasses that incorporate cylindrical correction over the lenses. Use spherical equivalent in the contact lens Fit with a front toric lens design

Question 12

If a patient comes in to see you for an evaluation of rigid lenses and the surface of the lenses show deposits what recommendation would you make to this patient?

Answer 12

More diligent cleaning with a surfactant cleaner.

Use of enzyme tablets.

Question 13

Given the following specifications what should be the thickness of the contact lens?

K 44.00 /46.00 @ 090
CL power: - 4.00 = 0.13mm (standard)
Corneal astigmatism = 2.00 D

Answer 13

0.15mm

Question 14

If a patient presents with burning and stinging immediately upon lens insertion, what are the possible causes of this problem?

Answer 14

Improper use or missing of solutions
pH of solution used Preservatives in solution used

Question 15

List at least four problems that may be cause unstable vision in a patient wearing rigid gas permeable lenses.

Answer 15

Optical zone diameter too small

Excessive blink-induced lens flexure resulting from a steep fit

Low minus thin lenses

Surface dry spots. Excessive blink-induced lens movement

Question 16

Charcteristics of Tight Fitting Lenses:

Answer 16

Base curve is too steep
Optic zone diameter is too large
Excessive bearing in the intermediate corneal areas
Peripheral curve is too steep or too narrow
Overall diameter too large

Question 17

Characteristics of Loose Fitting Lenses:

Answer 17

Base curve is too flat
Optic zone diameter is too small
Peripheral curves are too flat or too wide
Lens diameter is too small
Center thickness is too thick for the power

Question 18

Corneal and scleral changes caused by a high riding rigid lens are:

Answer 18

Epithelial edema
Stippling
Dimpling
Superficial vascular changes in the superior limbal areas

Question 19

How do you correct the following: reduction in diameter, reduction in the optic zone and flatter peripheral curves. Small power changes, fenestration.

Answer 19

Make modifications to current lens

Question 20

How would you correct: Increases in lens diameter, increase optic zone diameter and decreases in peripheral curves. Change Base curve and the center thickness. Large power changes

Answer 20

Order NEW lens these problems cannot be solved with modifications

Question 21

What problem may be due to any of the following:

Use of incompatible care products

Improper use of care product (i.e. lens cleaning just prior to insertion)

Inadequately blended peripheral curves

Deposits on the concave lens surface

Accumulation of mucus under the lens

Poor edge design

Incomplete blinking

Lenses fitted too steeply

Answer 21

Persistent Excessive Lens Awareness:

Question 22

This problem is usually due to the use of incompatible solutions. In this case, a solution with different chemical components should be tried. Such staining may also be caused by the presence of deposits on the posterior lens surface due to ineffective lens care. These deposits are best removed by lens polishing.

Answer 22

Generalized Corneal Staining:

Question 23

This problem may be due to any of the following:

Preservatives in the care solutions

Presence of pingueculae

Infectious or allergic conjunctivitis

Inadequate lens lubrication

Excessive mucus accumulation as occurs in dry eyes

Answer 23

Ocular Redness Without Staining:

Question 24

This problem may be related to increased mucus production, i.e. GPC, keratitis sicca, eroding sutures after cataract surgery, chronic allergies or medications. Patients with this problem should supplement the recommended optimum lens care regime with a weekly enzyme treatment and be re-instructed in the use of the proper care solutions.

Answer 24

Excessive Development of Lens Deposits:

Question 25

The presence of discrete non-wetting areas on a new or recently modified or polished lens, are usually due to the persistence of hydrophobic products used during lens fabrication. These hydrophobic contaminants have a greater affinity for RGP lens and can only be removed by the lens manufacturer using a special solvent. Surfactant cleaners are generally ineffective.

Other causes of a large wetting angle and loss of surface wettability include surface contamination with cosmetics, hair spray, skin preparations, inadequate tear lubrication, incomplete blinking, improper care solutions and dry lens storage.

Answer 25

Lens Surface Dry Spots:

Question 26

This may be due to repeated, excessive compression of lenses during handling (especially low minus lenses having a less-than-recommended center thickness) or excessive flexing of minus lenses on astigmatic corneas

Answer 26

Recurrent Lens Warpage

Question 27

The problem may be due to any of the following:

Excessive blink-induced lens flexure resulting from a steep fit

Excessive blink-induced lens movement

Optical zone diameter too small

Low minus thin lenses

Surface dry spots.

Answer 27

Unstable Vision:

Question 28

Reduced vision correction in relation to changes in refractive error may be due to lens warpage, front surface deposits, or switched lenses.

Answer 28

Reduced Contact Lens-corrected Vision:

Question 29

_________ problems may be due to careless handling, storage procedures or the use of lenses having less-than-recommended center, edge or junction thickness, especially for patients having poor manual dexterity.

Answer 29

Repeated Lens Breakage:

Question 30

Subjective Symptoms: Photophobia, Halos or Streamers Around Lights, Spectacle Blur

Objective Signs: Edema can be observed using sclerotic scatter with our without magnification in the slit lamp. If magnification is used, the biomicroscope must be out of click-stop. Sometimes central corneal clouding can be observed with the naked eye.

Assessment/Causes: Non Gas Permeable Materials (PMMA), Partial or inadequate blinking, Tight lens or lack of adequate movement, Over-wear, Adaptive edema

Answer 30

Rigid Lens Induced Corneal Edema

Plan/Correction: Reduce total diameter, Flatten or blend peripheral curves, Flatten base curve, Gas permeable material

Question 31

Subjective Symptoms: Flare around lights, especially at night, Vision distortion, Dryness may also be present

Objective signs: The practitioner will be able to view the lens in a superior position with the naked eye or with a slit lamp.

Assessment: Upper lid tension causes superior displacement, Thick edge design, Steep lens/cornea relationship, Displaced corneal apexdecreased.

The lens/cornea relationship may be made flatter.

Answer 31

High Riding Lens

Effects of gravity on lenses:

Ø Minus Lens Design
Ø Thin Lens Design

A high riding rigid aspheric lens can be corrected by reducing the total lens diameter in steps of 0.2 mm, or by making the lens with a hyperflange design. Using a steeper base curve along with a diameter reduction can be effective in giving the lens a more central position. In some cases, prism ballast may be necessary.

Plan: Any of the six methods listed below may correct a high riding lens depending on the patient’s lid configuration.

The total lens diameter may be increased.

The total lens diameter may be decreased.

The edge thickness may be

The center thickness may be increased.

A prism ballast design may be used.

Question 32

Subjective symptoms: Halos around lights, particularly at night, Vision distortion, Dryness may also be present, Lens may become “sucked on” because the tear layer no longer exists between the cornea and the lens

Objective signs: The practitioner will be able to view the lens in an inferior position with the naked eye or with a slit lamp.

Assessment: Plus lens design, Flat lens cornea relationship, Thick lens, With-the-rule astigmatism, Displaced corneal apex

Answer 32

Low Riding Lens

Plan:

Any of the seven methods listed below may correct a low-riding lens depending on the patient’s lid configuration.

The total lens diameter may be increased.

The total lens diameter may be decreased.

The center thickness may be decreased.

A back surface toric or bitoric lens design may be used.

The base curve may be made steeper.

The base curve may be made flatter.

A minus carrier design may be used.

Contradictions in the methods used to correct a low-riding lens occur because opposing actions will sometimes make the same changes to the lens/cornea relationship. This is particularly true if the changes made to the lens parameters are combined. As an example, increasing the diameter of a low-riding rigid lens while flattening the base curve allows the lid to create more traction on the lens. Decreasing the diameter, without changing the base curve, will still give a flatter lens/cornea relationship to allow the lid to play a greater part in moving the lens upward.

A low riding rigid aspheric lens can be corrected by reducing the total lens diameter in steps of 0.2 mm, or by making the lens with a myoflange design. If the original lens is too small, a larger lens made with the myoflange may center better.

Question 33

This is caused by _______ positions of the cornea not being wetted with each blink, producing an area of dryness that stains with fluorescein.

Subjective symptoms: The patient may see an area of redness on both sides of the lens when they look in the mirror and will probably not be symptomatic in terms of discomfort.

Objective signs: The practitioner will see the same area of redness and will see staining with fluorescein with or without the slit lamp.

Assessment: Low-riding minus lens, Exposure due to minus lens, Thick edge design, Lack of adequate lens movement

Answer 33

Three and Nine O’clock Staining

Plan: Position lens superiorly by:

o increasing lens diameter
o flattening lens cornea relationship
o changing to toric lens design

Decrease edge thickness

Soft contact lens

Question 34

Subjective symptoms: The patient may not notice anything at first. In fact, the lens will be more comfortable in the beginning because it moves less, which creates less sensation. The lens may become more uncomfortable with longer wear since it is not moving freely and therefore, the tear layer is not being renewed at each blink.

Objective signs: Corneal staining, Dimple veil, Edge compression, Corneal edema, Corneal steepening

Assessment: Lens is too tight. There are several options for correction of this problem depending on the circumstance.

Answer 34

Tight Fit

Plan:

Flatten base curve

Reduce diameter

Flatten or widen peripheral curves

Blend peripheral curves

Question 35

Subjective symptoms: flare, photophobia, poor or intermittent visual acuity

Objective signs: A rigid lens may be decentered nasally, temporally, superiorly or inferiorly

Assessment: Flare, fluctuating visual acuity or photophobia are caused by the peripheral curves passing into the patient’s line of sight. This will be noticed particularly in low lighting situation because the pupil is dilated.

Lens can be displaced by a cornea with low or high against the rule astigmatism

Lens can be decentered by a displaced corneal apex

Answer 35

Decentered Lens

Plan: Increase the total diameter of the lens.

Use a toric lens design.

Use a spherical lens fit steeper than K.

Question 36

Subjective symptoms: Patient may complain of discomfort after long hours of wear. Lenses may become coated quickly. More discomfort is evident after lens removal. This phenomenon may be seen with a low-riding lens.

Objective signs: Trapped mucous debris, Corneal scleral imprint, Corneal staining, Altered tear layer

Assessment: Overnight wear of RGP lenses, Steep peripheral curve, Steep base curve, Large diameter, Displacement during sleep

Answer 36

Adhesion Phenomenom

Plan:

Flatten lens cornea relationship

Increase center thickness

Decrease O.Z. and/or diameter

Discontinue extended wear

Re-roll edges

Question 37

Subjective symptoms: Patient reactions may vary from no symptoms at all to extreme pain depending on the severity of the abrasion.

Objective signs: The abrasions on the cornea will be evident by the fluorescein staining patterns observed through the slit lamp.

Assessment: Loose lens, Sharp edge, Poorly polished or insufficient, Peripheral curve, Tight fit

Answer 37

Peripheral Corneal Abrasions

Plan

Modify edge design

Polish or flatten peripheral curves

Adjust base curves

Eliminate excessive steep or flat fit