Lecture 2 - Ocular Pathology - pre-fit considerations Flashcards
Why can diabetes cause problems when fitting contact lenses?
- Reduced Corneal Sensitivity
- Corneal Oedema, risk of neovascularisation
- Delayed Healing, epithelial fragility
- Susceptibility to infection (bacterial, fungal)
- Dry Eye ~ 50% (so expect staining)
- Unstable Refraction
- Keratitis
- Blepharitis
- Xanthelasmata
- -> poor lipid metabolism
Diabetes should not interfere with contact lens wear
What should you consider when fitting diabetic px?
Informed Consent
Liase (co-operation) with other professionals involved in the care of the patient
Consider glycaemic control
More frequent aftercare
High permability and transmissiblity of Oxygen
Reinforce Hygiene & Handling
Proceed with caution…
Why can Hyperthyroidism or exophthalomas cause problems when fitting contact lenses?
The exophthalmos causes lid lag, reduced blink rate and dry eye contraindicate contact lenses.
Why can Chronic Catarrh & Sinusitis cause problems when fitting contact lenses?
There is an increased risk of infection when corneal abrasions occur. There may be excess mucus in the tears which will be visually distracting. A blocked naso lacrimal system may encourage epiphora.
Why can Cold sores cause problems when fitting contact lenses?
The Herpes Simplex Virus may be transferred from the mouth to the eyes via the fingers that touch the cold sores and then are used to insert contact lenses. Another source of infection arises from licking the contact lenses prior to insertion. Herpes keratitis leads to dendritic ulcers. The virus lies dormant in the nervous system and can be re-activated at any time.
No CL wear with an active ulcer!
Why can Skin conditions and allergic reactions cause problems when fitting contact lenses?
Allergic reactions to the contact lens solution preservatives and to lens surface deposits are common.
Allergic reactions tend to show a gradual build up of signs and symptoms whereas a toxic reaction is usually accompanied by a rapid onset of symptoms.
Why can Atopic eczema cause problems when fitting contact lenses and how can it be managed?
This is often linked with hay fever and/or asthma. The condition encourages surface deposits.
If contact lenses are fitted, the material should have good wetting properties.
Lid irritation can be minimised by fitting a large lens with minimal edge clearance and minimal edge thickness (radial edge thickness 0.12 mm).
Why can Keratoconjunctivitis sicca (Sjogren’s syndrome) cause problems when fitting contact lenses and how can it be managed?
This is associated with rheumatoid arthritis. It is characterised by a poor lacrimal secretion.
Dry eyes and contact lenses don’t go together.
The sealed or channeled scleral lens may help to protect the cornea.
An alternative would be a soft contact lens with artificial tears instilled at regular intervals.
Why can Xerophthalmia (vitamin A deficiency) cause problems when fitting contact lenses?
This can cause keratomalacia. It may be worth checking on patient’s diet.
Typically the corneal ulcer is centrally located and bilateral, Grey and indolent (little pain, slow to heal).
The cornea becomes soft and necrotic (death of cells) (hence the term keratomalacia). Perforation (holes in the cornea) is common.
Why can Seborrhoeic eczema cause problems when fitting contact lenses and how can it be managed?
This manifests as dandruff and blepharitis.
Any lenses must induce minimal lid irritation.
There is a risk of staphylococcal keratoconjunctivitis.
The blepharitis may be treated with tetracycline, taken orally: 250 mg twice daily for six weeks. This will be inactivated if taken with milk and is not advised for pregnant women or young children.
Why can Acne Vulgaris cause problems when fitting contact lenses and how can it be managed?
Occurs at puberty and is generally not aggravated by contact lens wear.
There may be problems of greasing and frothing of lenses.
Solutions containing polyvinyl alcohol may help with the greasing of lenses.
Why can Acne rosacea cause problems when fitting contact lenses?
There will be accentuated blood vessel dilatation in the conjunctiva and the skin of the eye regions of the face.
Ocular involvement more severe in males
Often get posterior blepharitis
Punctate keratitis is associated with this condition and may become worse by contact lens wear.
Why can Epidermolysis bullosa cause problems when fitting contact lenses?
This is a rare inherited skin disease which may produce anything from mild blepharitis and conjunctivitis to pronounced vesicle formation over the anterior eye.
High water content soft lenses worn on a daily basis are recommended.
Why can Psoriasis (skin disease showing a red patchy appearance) cause problems when fitting contact lenses?
Contact lenses are not likely to aggravate this condition but the associated nervous disposition may cause problems during adaptation.
Why can Surgery cause problems when fitting contact lenses?
Surgery performed on the extraocular muscles may produce scar tissue on the bulbar conjunctiva which may affect the fit of a soft lens. Scar tissue on the cornea does not usually cause problems unless the scar is raised above the normal corneal contour.
Why can Keratitis and conjunctivitis cause problems when fitting contact lenses?
Active keratitis makes contact lens wear impossible.
Contact lenses may however be of exceptional benefit to a patient who develops corneal irregularity or scarring from a past ulcer but it must be noted that the irritation in the presence of a contact lens may encourage the condition to recur.
Active conjunctivitis minimises the possibility of successful contact lens wear although lenses may successfully be worn during the quiet phases.
Why can Iritis, iridocyclitis or uveitis cause problems when fitting contact lenses?
Patients should not be fitted because the added irritation of a contact lens may activate the condition. It must be remembered that the disease may flare again spontaneously and contact lens wear could be blamed as the trigger.
Why can Keratitis sicca cause problems when fitting contact lenses?
This dry eye condition may make the wearing of contact lenses difficult.
However some patients welcome the reduced evaporation of tears from the cornea when a lens is worn, especially a scleral RGP - CL may act as a bandage.
Why can Trachoma cause problems when fitting contact lenses and how can it be managed?
Chronic keratoconjunctivitis caused by Chlamydia trachomatis (obligate intracellular organism)
Repeated episodes cause chronic follicular conjunctival inflammation (active trachoma), which leads to tarsal conjunctival scarring
Scarring distorts the upper tarsal plate and leads to entropion and trichiasis (cicatricial trachoma)
Results in corneal abrasions, corneal scarring and opacification, and, ultimately, blindness
Endemic in Africa, Asia, Middle East, Australian Aboriginals
Old, inactive cases may find that a contact lens helps protect the cornea against scarring which is often present on the lids.
A scleral RGP lens may be the best option.
Why can Glaucoma cause problems when fitting contact lenses?
Scleral and soft contact lenses rest on the anterior cillary veins which constitute a major drainage route for the aqueous.
These lenses may, therefore, influence the intraocular pressure (IOP). It could be argued that this will be raised or lowered (due to the massaging effect of a moving lens).
The situation is no clearer for corneal lenses. It may well be that contact lenses do not affect the IOP but the conservative practitioner would probably advise against contact lens wear.
