Contact Lens Fitting1. Introduction to Contact Lens Fitting

CONTACT LENS FITTING – PROTOCOL

Patient screeningPreliminary examination &

measurementsTrial lens fittingLens dispensingAfter-care

PATIENT SCREENING

Establish why the patient wants CLs

Is the patient suitable for CLs ?

Obtain baseline information

Advise patient of their options

PRELIMINARY EXAMINATION AND MEASUREMENTS

A slit-lamp examination of the anterior segment.

Keratometry.Corneal and pupil size measurements.Assessment of lid characteristics.A tear assessment.A spectacle refraction and calculation

of the ocular Rx (corneal-plane refraction).

KERATOMETRY Corneal curvature is the most important

measurement needed before starting CL fitting.

Measures only 3 mm of the corneal curvature

Corneal topography gives the complete mapping of the cornea.

KR measurement is sufficient in most of the fittings.

Corneal irregularity also noted.

The reading also tell us about the degree of corneal astigmatism.

The BC of the CL is determined by the corneal curvature measurements.

CORNEAL DIAMETER HVID – Horizontal Visible Iris Diameter

VVID – Vertical Visible Iris Diameter

With a simple millimeter scale ,measuring the limbus to limbus size both across the horizontal and vertical lengths.

The corneal diameter aids in determination of the total diameter of the CL.

PUPIL SIZE

The diameter of the pupil is measured by a simple millimeter scale both in standard room illumination and low illumination .

This aids in determining the optic zone size of the CL.

TRIAL FITTING: ROUTINE Diagnostic fitting

A diagnostic or trial fitting uses a series of lenses, chosen on the basis of the findings of the preliminary examination.

Lenses are assessed sequentially until a desirable fit is obtained.

The aim of the trial fit is ensure a good lens-cornea relationship with the design chosen and to confirm the final Rx required.

Final lens order

TRIAL FITTING: LENS SELECTIONBack optic zone radius (BOZR).Total diameter (TD).Water content (for soft contact lenses).Lens design (lenticular, multicurve,

surface shape, etc.).Lens type (spherical, toric, bifocal, etc.).Lens material.BVP

TRIAL FITTING: PROCEDURE Initial lens selection.Trial lens fitting and vision assessment.Subsequent trial lens selection.

If Trial lens required is not available: Empirical Prescribing

TRIAL FITTING: DESIRED RGP LENS FIT Central alignment. (BOZR of the lens closely

matches the central corneal curvature)

Moderate edge clearance

Good centration.

Corneal Coverage (SCL)

Adequate movement

Comfort

TRIAL FITTING: FINAL LENS ORDER

Lens parameters

Lens material and type

Special requirements

Delivery date required

LENS DISPENSING

•Provide information on the lens care regimen

• Practise insertion and removal techniques • Provide information on adaptation • Provide information on signs of

complications • After-care visit schedule

AFTER-CARE Investigate complaints Perform general ocular examination:

- Over-refraction - Slit-lamp microscopy - Other tests particular to the patient

Assess lens fit Review lens care regimen Schedule next after-care visit

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