Lens Flashcards
Describe the anatomy of the lens?
- Convex structure behind iris
- 3 layers capsule-cortex-nucleus
- Clear, elastic structure to begin with but solidifies as px ages
- Suspended by zonules to ciliary processes of circular ciliary body
- Can change shape
- When ciliary body relaxed, it relaxes the zonules – when ciliary body stretches, it pulls the lens & flattens the lens
Describe physiology of the lens?
- It provides dioptric power
- Total eye dioptric power of 60D (2/3 cornea & 1/3 lens) – most of corneal refractive power comes from tear film interface
- Accommodation depending on age -> 15-20D at v young, 10D at 25 yrs old & only 1D at age 50
Describe the examinations to assess the lens?
- Essential part of exam of eye
- Start by hx taking
- Notice age & px symptoms – always correlate px symptoms with clinical findings
- Hazy vision (can be intermittent), glare, monocular diplopia
o Posterior subcapsular cataract – vision will drop at night-time but will be 6/6 during day - VA
- Contrast sensitivity
- SL exam – look at red reflex (good way of determining the opacity of the media)
- Fundoscopy
- Check IOP
What are the two types of lens pathology?
- Cataracts – v common
- Phacomorphic glaucoma – as result of dense cataract
Describe cataract?
- Opacity of lens – light does not get through media
- Most commonly age related but could also present as congenital cataract & traumatic cataract
- VA is important BUT take notice of px symptoms & other exam findings – glare & monocular diplopia
- Full ocular exam including refraction, SL, pupil, IOP & dilated fundoscopy
- Assess px lifestyle requirement – is poor vision affecting their function?
o If px is very happy with the vision that they have got then there may not be any need for referral
Very dense cataract could be 6/60 or perception of light even
Posterior subcapsular cataract may have good vision but then be very affected by the cataract at night
What will the vision be in a very dense cataract? When will px with posterior subcapsular cataract notice it most?
Very dense cataract could be 6/60 or perception of light even
Posterior subcapsular cataract may have good vision but then be very affected by the cataract at night
Describe age-related cataract?
- Incidence increases with age
- 30% of people aged 65 yrs & over have visually significant cataract in one or BE (VA 6/12 or less – sometimes VA can be 6/9 & px is still v affected by it)
- Multifactorial reasons – age, sex, race, DM, sunlight, genetic, steroids, nutrition
- No preventative measures so far
Describe traumatic cataract?
- Complex case
- Usually younger px group
- Requires significant force to occur – not usually due to simple trauma, more likely due to severe trauma
- V likely to have other ocular pathology e.g. zonule or iris damage
- Could be due to being punched in eye
- Higher risk of retinal detachment
- Technically difficult & special lenses might be needed
- Success rate is reduced in comparison to age-related cataract
- Image: traumatic cataract, iris has come apart (iris dialysis), lens may be quite wobbly & may not be able to put a simple lens inside the bag
Describe congenital cataract?
- Infant is born with cataract – all new-borns have red reflex test before discharge from hospital
- Cataract surgery is required urgently as infant can develop dense sensory deprivation amblyopia within days
- Choice of IOL or aphakia
o Vision is not going to be as good as a normal eye as near vision will be limited - Long term problem w/ glaucoma
Describe phacomorphic glaucoma?
- A swollen dense cataract (is thicker &) can press iris forward & cause acute angle closure glaucoma
- Treatment is URGENT cataract surgery
- Image: cataract is v dense, no red reflex, no view of fundus, AC seems shallow, this px requires URGENT cataract surgery not only to remove the cataract but also to save the eyesight
What is the pathway for referral of cataract?
- Assess px & eye
- Examine
- Measure
- Referred by optometrist to cataract assessment clinics
- Seen by nurses for general assessment & biometry
- Seen by consultant & consented for surgery if appropriate
Describe cataract surgery?
- 98% success
- Mostly performed under topical anaesthesia (eyedrops) but could be done with injection under Tenon’s capsule (subtenon injection) or general anaesthesia (depending on px’s co-operation (e.g. dementia or involuntary movement) and wishes) – the px WILL NOT SEE ANY OF THE OPERATION
- Mostly a day case procedure
- Depending on complexity of case & experience of surgeon – can take as little as 10mins operating time
What are the potential complications of cataract surgery?
Intra-operative (during surgery): usually dealt w/ by ophthalmologist
* Problems w/ corneal incision – poor wound reconstruction requiring suturing
* Capsular tear leading to vitreous loss & inability to implant IOL
* Drop nucleus – lens falls in vitreous cavity – requires vitreoretinal procedure
* Intra-ocular haemorrhage – supra-choroidal or expulsive haemorrhage – this is v rare but v significant
Immediate-early post-operative (after surgery): usually seen by optoms
* Wound leaks – leakage from wound – needs to be addressed as increases risk of infection
* Vitreous outside of wound – requires URGENT referral – route of infection
* Raised IOP – usually effectively treated by eye drops or tablets
* Lens dislocation
* Endophthalmitis – EMERGENCY phone referral
o Look out for hypopyon, red eye, pain etc
o Tx is urgent injection of antibiotics into eye – ideally within 6hrs so time is of the essence
* Incorrect lens power – resulting in refractive surprise – referral needed
Late complications:
* Chronic inflammation/infection
* Posterior capsular opacification – requires YAG laser capsulotomy
* Capsular shrinkage & lens dislocation – capsule phimosis
* Retinal detachment – high myopia w/ axial length of >25.5mm
Posterior capsular opacification – lens has become opacified and light is not getting through again
Tx is fairly straight forward (YAG laser capsulotomy)
Describe cataract surgery post operative review & meds?
- A combination of topical steroid & antibiotic drops are given for 2-4weeks
- There is no need for day 1 review
- Examined by optometrist within 7 days of surgery & then 4(-6) weeks after for refraction
- Post operative spec correction is usually required – usually have to wait about 6 weeks for it to stabilise
Describe the types of intra-ocular lenses (IOLs)?
- Mono‐focal
- Multi‐focal (diffractive and refractive) – MUST mention to px – they have to have the choice
o Multifocal lenses can potentially reduce the need for near vision glasses but are not for everyone (decrease contrast sensitivity and night glare)
o These lenses split the light – 30% for near & 70% for distance – they are not like varifocal lenses – they project picture of near, intermediate, distance at time & brain picks the correct image for that specific distance – takes a period of adaptation (about 1 month or 2 – ONLY work best if doing both eyes not so much just one eye) - Mono-vision – one eye is for near and one eye is for distance – if independency from glasses is wanted
- Toric IOLs (correct astigmatism)
- EDOF (Extended Depth Lenses)
- Most of NHS work is Mono‐focal lenses
CANNOT MIX AND MATCH IOL – if have mono-focal in one eye then must have it in other eye
