Week 2.07 Planned Overnight Lenses Flashcards
Keratoconus
- Corneal shape changes – degeneration in centre then can develop to keratoglobus where the whole cornea becomes cone shaped not just the centre
- Corneal ectatic disease
- Males more than females
- Hayfever eczema asthma more common to get keratoconus
- Onset usually during teens
- Bilateral although not symmetrical in 90% of cases
What are risk factors for keratoconus
- relative
- Down’s syndrome
- ocular allergy
- south Asian
- eye rubbing
What are the early signs of keratoconus
Asymmetrically reduced VA
Increased ATR astigmatism
Scissor reflex ret
Irregular K mires
Corneal thinning
What is collagen cross linking
- cornea strengthened by increasing links between collagen fibrils
- epithelium removed
- stroma soaked with riboflavin to absorb UVA
- UVA applied for 30 mins
What is a corneal graft
Surgical procedure where a damaged or diseased cornea is replaced with a healthy donor cornea
Lamellar corneal graft
Deep lamellar keratoplasty - partial thickness graft
Better corneal regularity
Quicker visual recovery
Technically very difficult
Post graft
- Careful monitoring for rejection
o Raised IOP
o Cloudy cornea
o Neovascularisation around limbus - ~10 months of healing time
- Do not fit lenses for at least 6 months
o High oxygen flux required
o Complex fit due to wound edge
o LASIK can be successful
Bandage CLs
- Protection (entropian, sutures, recurrent corneal erosions)
- Pain relief – epithelium not well ‘stuck’ on rapid eye movements when sleeping can dislodge that epithelium and can cause pain (bulbous keratotomy, filamentary keratitis)
- Leaking wound
- Healing (chronic epithelial defects, corneal ulcer, post PRK/LASEK, post cross linking)
- Maintenance of corneal hydration (scleral)
What are the different types of planned sleeping in CLs
- Extended wear (EW) – up to 30 nights wear before removing and replacing the lens. For convenience
- Continuous wear (CW) – over 30 nights wear before removing and replacing lens. Often used in hospital lens fitting. Prescribed for therapeutic purpose
- Flexible wear: napping, occasional overnight/accidentally overnight
What are some lens options for 2 weekly or 1 weekly overnight
Balafilcon pure vision
Senofilcon Acuvue oasys
Comofilcon biofinity
RGP lends options for overnight
Hexafocon Boston
Paflufocon fluoroperm
Boston XO EyeDream ortho-k
Complications of sleeping in lenses
- Hypoxia changes
- Epithelial/stromal oedema
- Limbal hyperaemia
- Corneal neovascularisation
- Endothelial polymegathism
- Myopic shifts
Silicone hydrogel: - Mechanical complications
- Superior epithelial accurate lesions – indentation from thickness of lens
- Mucin balls
- Contact lens induced papillary conjunctivitis (CLIPC)
RGP - Lens binding
- Discomfort
- 3&9 o’clock staining
What is MK
Is a complication of sleeping in lenses
- Sight threatening – identify and refer within hours to limit loss of vision
Mechanism:
- Affects central cornea
- Presence of lens on the eye affects epithelial metabolism reducing adhesion of epithelial cells
- Microbes adhere to lens
- Epithelial trauma provides route in
- Microbes adhere to cornea and invade corneal tissue
- Release of toxins and enzymes
- Immune reaction
o Infiltrates
o Oedema
Risk factors for MK
- Sleeping in lenses (not just hypoxia issue) – stagnant tears, increase in temp etc
- Contaminated solutions
- Contact with water – swimming or showering in lenses etc
o Problem for EW/CW - Diabetes
- Smoking
- Poor lens/case hygiene
Who’s suitable for extended wear
- Motivated
- Circumstances
o Travel
o Environment
o Occupation
o Dexterity
Infants
Elderly - Low risk circumstances and personality
