CONTACT LENS INSERTION PROCEDURE

Preparation of the patient - Use topical local anaesthetic only. Sedation may be required; however, third eyelid prolapse is a disadvantage. Excessive topical local may slow the blink rate causing dehydration of the contact lens (extra lubrication may be required initially if this is the case).

Measurement of the cornea and lens size - Callipers are used to measure the cornea from limbus to limbus. Use the nearest (but smaller) lens size to the actual diameter of the cornea.

Preparation of the cornea - Ensure no hair or debris remains on the cornea. Remove undermined edges of epithelium from around the ulceration (extreme care is required in cats). A drop of extra-ocular visco-elastic (Keralon) provides a good liquid base for the lens to sit on (optional).

Preparations of the contact lens - Remove the lens from its container using a cotton-tipped applicator and make sure it is inverted the correct way (Taco test - see TIPS below).

Insertion of the lens - Place the lens onto the cornea either with fingers or with using the same cotton-tipped applicator. Take care to remove any air bubbles and ensure that the lens is under the leading edge of the third eyelid using the cotton-tipped applicator.

Tips:

The Taco Test - Squeeze the two edges of the lens together and it should form a 'taco' shape when correctly orientated. If the lens resists this movement and curls onto the fingers then it is "inside-out". The tapered edge of the lens angles out like a saucer if the lens is "inside out". As the lens is removed from its container by a cotton-tipped applicator, when it is correctly orientated, the lens wraps around the applicator and then unfurls when the free overhanging edge of the lens is "smoothed" onto the cornea.

Use only drops not ointments - Ointments or oil based drops (e.g. Cyclosporin) clogs the oxygen transference of the lens and must not be used.

Keep the lens wet - The lenses are hydrophilic (i.e. water loving) and they cannot be used in cases of inadequate tear film.

Check at least weekly - Weekly examination of patients with contact lenses is recommended, with cleaning and replacement of the lens if necessary.

Problems:

For lenses that keep falling out - Use a different size lens and/or different curvature - there are three sizes denoting curvature for each available lens diameter. A Partial Tarsorraphy assists with retention of the lens in some animals.

For lenses that dehydrate - Rehydrate the lens by soaking it in distilled or de-mineralised water (D-water) and as long as the lens is not torn or damaged in any way then it can be re-used after autoclaving.

Autoclaving:

Lenses should be autoclaved if they become contaminated. Return the lens to its original container after cleaning with D-water and fill the container with D-water. Remove the seal from inside the lid and screw on very loosely. Place autoclave indicator tape on the bottle then autoclave using the setting where depressurization is graduated over time allowing D-water not to be boiled and therefore evaporate off.

CONTACT LENS INSERTION PROCEDURE

Tips:

Problems:

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