Introduction to Contact Lenses Flashcards
Why contact lenses?
- more natural vision, unlike glasses like these, are further away
- glasses slip/ leave marks
- better for myopes in regards to spectacle magnification/ appearance (lenses within glasses changes their visual acuity as its further away from the eye)
- FOV is reduced with glasses
- glasses can fog up/ steam in winter
- better for anisometropia, as different mag affects power in lenses
- can correct irregular astigmatism = rigid contact lenses
- UV protection
- soft contact lenses useful in sports
- cosmetic advantageous
- fewer arbitrations
What are the 4 different types of contact lenses?
- Rigid Gas Permeable (RGP)
- Soft
- Silicone Rubber
- Hybrid
Name the two different material types of soft contact lenses?
- Hydrogel
2. Silicone Hydrogel
What is the disadvantage of hydrogel lenses? (type of soft contact lens)
- can get dry towards the end of the day
- lose its shape
List the motivations for using contact lenses
- cosmetic
- convenience
- refractive
- Pathological e.g allergies, irregular cornea, keratoconus
List 5 choices for choosing RGP lenses
- vision is better
- corneal irregularity
- dry eyes
- compliance
- SCL failure
List 3 choices for choosing SCL
- infrequent wear
- environment
- RGP failure, including fitting problems
What does it mean by History Taking?
- Traditionally a history and symptoms interview during an eye examination would be structured in the following order:
1. reason for the visit (the motivation for lens wear)
2. ocular history (any underlying
pathology through differential diagnosis)
3. medical history (patient medical history)
4. medication (for systemic condition and self-medication)
5. family history (diabetes/ glaucoma)
6. social history (should cover patient risk factors)
What are the general symptoms of contact lens wear?
- Visual disturbance (issues with patients clear vision)
- pain
- discomfort (e.g. at the end of the day )
What does it mean by SOCraTES?
Site – unilateral/bilateral
Onset – sudden, gradual, fluctuating, event-related
Character – flare/glare, blurring; burning/hot, gritty, itchy, watery, tired
Timing - constant/ intermittent, night
Exacerbating/relieving factors – near/distance, with contact lenses
Severity – mild, moderate, severe
How does SOCraTES help us?
- can start to narrow down your differential diagnosis to a specific cause
The general methodology of a differential diagnosis?
- consider all of the conditions that may have the stated symptoms
- ask to follow up questions
- a single condition is now narrowed down
- follow up with an eye examination
- treatment is found
- record accurately
How do we find out the patient’s medical history?
- ask patients to bring a list of their current/ ongoing medication
- ask patient to also bring their GP details (to follow up)
- use this information to find out any potential ocular side effects of the drugs & infections
Examples of medical history too look out for?
- allergy
- diabetes
- systemic inflammatory disease such as sarcoidosis (uveitis)
- thyroid eye disease
- dermatological conditions such as seborrhoiec dermatitis, atopic eczema, acne rosacea (blepharitis)
- Previous history of hay fever (atopy)
- Ocular surgery
What are the important follow-up questions to ask?
- onset
- The type
- is it well-controlled
- relevant family history
What does it mean by Social History?
- occupation
- driving
- smoking
- hobbies
Examples of things to consider when talking to patients about contact lens wear?
- low refractive error (motivation decreases for CL)
- horizontal prism
- ocular infections, inflammations, recurrent corneal erosions
- diabetes (use soft contact lenses = greater need for compliance)
- sinus and allergy problems
- sensitive eyes
- dry eyes / poor blinking
- acne rosacea / seborrheic conditions
- Adverse environments e.g. dusty
What are the 4 stages to contact lens fitting examination?
- Recent eye examination = recent spectacle prescription (BACK VERTEX DISTANCE)
- Patients unaided vision/ Visual acuity = near & distance
- Binocular status
- Ophthalmoscopy (anterior eye health)
What things should you have discussed with the patient prior to fitting?
Patient counselling and documentation regarding:
- recommended lens type
- modality of wear
- care / cleaning regimen
- possible risks / complications
- time before ‘full time’ wear is likely to be achieved
- possible visual compromise and discomfort
- what to do in an emergency
- costs involved
Refraction (comes from eye examination)
- convert to 0mm back vertex distance
- decision to go ahead with contact lens wear
Measurement of anterior eye parameters
- HVID = horizontal visible iris diameter
- Pupil diameter in dim and average illumination
- Interpalpebral aperture / lid position + tension
- corneal shape (keratometry/topography)
- tear film characteristics
*ideally during history & assessment
What do we need to measure prior to contact lens fitting?
(using a ruler/UV lamp)
- HVID (10-14mm)
- VPA (not relevant)
- Pupil in Max: dim illumination & Average: room illumination
*look at lecture slide
How can we measure Corneal Shape?
- using Keratometry
What is the general Care and Advice given in regards to contact lenses?
- the importance of solutions
- regular checks required
- use of daily’s is more hygeneic
What is the Legal advice given in regards to contact lenses?
- Always thoroughly wash your hands before handling CLs
- It is best to use a medicated soap (keep in stock for patients)
- When putting your CL away, place them in a fresh disinfecting solution
- Do not top-up
- If you wish to change solutions, ask your optometrist first
- If you wear your CLs infrequently, change the solutions of your case at least weekly
- Refrigerate your solutions and CL especially if worn infrequently
*ideally in writing
