Routine examination prior to contact lens use

Routine examination prior to contact lens use

Many factors determine whether a patient is a good candidate for the use of contact lenses. First, a detailed history and ocular examination

are necessary prior to fitting a contact lens.

 The history collects information about the patient’s general medical health, ocular health, family history of eye disease, and previous use of contact lenses.Motivation is one of the most important factors for the success of fitting. 

Patients with moderate to high refractive errors may be better candidates for contact lens wear than those with low degrees of refractive error. A good way to make this judgment is to evaluate the number of hours per day that the patient wears glasses. 

Patients who are minimally dependent on glasses in general have a low degree of success

with contact lens fitting. Poorly motivated patients frequently may not care for their contact lenses adequately and may not adapt to the lenses, particularly rigid gas permeable lenses.

 

 

 

General Health

Allergies

The patient should be questioned about allergies to medications, foods, and other substances. The allergic patient is more susceptible to adverse reactions to contact lenses and their maintenance products.

Diabetes

In moderate or severe cases of diabetes, there is occasionally corneal hypesthesia, leading to a greater propensity for corneal erosion and

infection. Diabetic patients are not candidates for extended-wear contact lens use.

Pregnancy and Menopause

Pregnant women with water retention may be intolerant of a contact lens. In general, contact lens fitting should be avoided during pregnancy. 

Some patients in menopause may present significant changes in the quality and quantity of the lacrimal tear film that may cause contact

lens intolerance.

Chronic Respiratory Disease

Patients with chronic respiratory disease such as asthma, sinusitis, and other similar conditions may have difficulty in fitting a contact lens.

During respiratory crises they may have conjunctival hyperemia, tearing, light sensitivity, and generalized discomfort that is aggravated by the use of contact lenses.

Psychological Conditions

It is essential that the contact lens wearer be sufficiently responsible to follow medical instructions, including information about the duration of wear, contact lens maintenance, understanding of the signs and symptoms of contact lens related problems, the risks of contact lens wear, and an understanding of when prompt assistance must be obtained.

Medication Use

The contact lens wearer must be informed also of the medications, either topical or systemic (such as nasal decongestants, diuretics, ben-

zodiazepines, immunosuppressants, etc.), that may alter the tear film and that may contraindicate or make difficult contact lens use.

Ocular Health

One must ask about the following issues:

1. Any previous ocular injury

2. Lid infection

3. Conjunctivitis

4. Cataract

5. Glaucoma (including family history)

6. Dry eye

7. Any surgery to the eye or ocular adnexa

8. Previous contact lens use

9. Medication intolerance

Contact Lens History

The following contact lens information should be obtained:

1. Types of contact lens previously worn

2. Success and complications with previous lenses

3. Reasons for the use of contact lens (cosmetic, spectacle intolerance,

aphakia, keratoconus, improvement of visual acuity)

4. Patient occupation (to determine if the patient is exposed to chemical

products or works in a dirty or dusty environment)

5.  Previous refractive correction

6. Sports and recreational activities

 

 

Ophthalmic Examination

Refraction

Corneal Curvature

The procedure most commonly employed is manual or automated keratometry, which measures the central corneal curvature. One may also use photokeratoscopy or computed topography.

Biomicroscopy

The biomicroscope is used to evaluate the lid, conjunctiva, tear film, cornea, iris, pupil, and anterior chamber.

Measurement of Palpebral Aperture Height

The opening of the normal palpebral fissure ranges from 7 to 13 mm (average is approximately 10 mm). The size of the palpebral fissure may contribute to or detract substantially from stabilization of the lens, especially rigid gas permeable contact lenses. 

Measurement of the palpebral aperture height is done at the slit lamp, with the patient looking at the examiner’s ear. It may be accomplished in the following ways:

● Noting in millimeters, with the help of a ruler, the distance between lids.

● Noting the position of the lid in relationship to the limbus, the lid at the limbus is annotated as zero; covering the corner, it is notated in

millimeters of area covered (for example, + 1, + 2 mm), and if sclera is left exposed, it is noted as -�1, �-2 mm, etc.

Lid Tone

Lids that are extremely tense or tight may alter the movement of the contact lens. There is no precise clinical method to measure lid tension.

One can estimate lid tension by grasping the lid between the index finger and thumb and pulling it away from the globe. 

It can then be classified as loose or tight. Studies have found a relation among lid tension, palpebral aperture height, and contact lens fitting characteristics.

Blinking

The examiner should evaluate the frequency and thoroughness of the blink. Anincomplete blink may change the movement of the lens on

the eye and the distribution of the tear film, with consequent desiccation of the cornea and/or conjunctiva and lens intolerance.Normal

frequency of blinking is 12 to 15 times per minute, which is increased with head movement and is diminished during states of attention, such as reading, watching television, driving, and computer use.

Corneal Diameter

The average horizontal diameter is approximately 11.7 mm (varying

generally between 11 and 12.5 mm).30,31 The vertical diameter is approximately 1 mm less.31 This is an important measurement in the determination of lens diameter.

Corneal Sensation

Corneal sensation may be diminished in systemic diseases such as diabetes, intrinsic eye disease (herpes simplex keratitis, for example), pregnancy, the menstrual cycle, the use of topical or systemic medications, or as a result of corneal surgery.

 Contact lens wear may also induce decreased corneal sensation.Contact lens wearers with decreased corneal sensation may be more prone to corneal erosion and/ or infection. Corneal sensation can be grossly evaluated using a wisp of cotton or, more precisely, with the esthesiometer of Cochet-Bonnet.