Week 5 - Lens and cataract surgery Flashcards
What is the Lens anatomy?
• Convex structure behind iris
• 3 layers (Capsule-Cortex-Nucleus)
• Clear, elastic structure
• Suspended by zonules to ciliary processes of the circular ciliary body
• Can change shape
What is the lens purpose?
• It provides diopteric power
• Total eye diopteric power of 60D (2/3 cornea and 1/3 lens)
• Accommodation depending on age (15-20D at very young, 10D at 25 years old and only 1D at the age of 50)
How is the lens examined?
• H&S
• Note px age/symptoms
- hazy vision? glare? monocular diplopia?
• VA
• Contrast sensitivity
• Slit lamp exam
• Fundoscopy
• Cheap IOP
What are lens pathologies?
• Cataract
• Phacomorphic glaucoma
What is cataract?
• Commonest reason for referral by optometrist
• Opacity of the lens (light does not get through the media)
• Most commonly age related but could also present as congenital cataract and traumatic cataract
What is age related cataract?
• Commonest worldwide reason for visual impairment and blindness
• Incidence increases with age
• Overall 30% of people aged 65 years old and over have visually significant cataract in one or both eyes (VA of 6/12 or less)
• Multifactorial reasons (age, sex, race, diabetes, sunlight, genetic, steroids, nutrition..)
• No preventative measures so far..
What is the cataract referral pathway?
• Assess patient and the eye!
• Examine
• Measure
• Referred by optometrist to cataract assessment clinics
• Seen by nurses for general assessment and biometry
• Seen by consultant and consented for surgery if appropriate
What is Biometry?
• A process whereby power of intra-ocular lens needed is determined
- Axial length of the eye and curvature of the cornea
• A hyperopic eye will need a bigger lens and a myopic eye will need a smaller lens (diopteric power)
• Can aim to leave the eye emmetropic after the operation
• Biometry can be done with ultrasound machine or an optical system
What is cataract surgery?
• 98% success
• Mostly performed under topical anaesthesia but could be done with iniection under the Tenon’s capsule or general anaesthesia
• Mostly a day case procedure
• Depending on the complexity of the case and experience of the surgeon can take as little as 10 minutes operating time
What are the two categories of cataract surgery complications?
• Intra-operative (during the surgery)
• Post-operative (After the surgery)
What are the Intra-operative (during the surgery) complications?
• Problems with corneal incision (poor wound reconstruction requiring suturing)
• Capsular tear leading to vitreous loss and inability to implant an intraocular lens (IOL)
• Drop nucleus (lens falls in the vitreous cavity)
• Intra-ocular hemorrhage (supra-choroidal or expulsive)
Immediate-early post operative complications?
• Wound leaks
• Vitreous outside of the wound
• Raised IOP
• Lens dislocation
• Endophthalmitis
• Incorrect lens power (refractive surprise)
What are the Late Complications?
• Chronic inflammation/infection
• Posterior capsular pacification (requires YAG laser capsulotomy)
• Capsular shrinkage and lens dislocation (capsule phimosis)
• Retinal detachment (high myopia with axial lens of over 25.5mm)
What is the post cataract surgery review and medication procedure?
• A combination of topical steroid and antibiotic drops are given for 2-4 weeks
• There is no need for day 1 review
• Examined by optometrist within 7 days of the surgery and then 4 weeks after for refraction
• Post operative spectacle correction is usually required
What are the different type of intra-ocular lenses?
• Mono-focal
• Multi-focal (diffractive and refractive)
- Multi-focal lenses can potentially reduce the need for near vision glasses but are not for every one (decrease contrast sensitivity and night glare)
• Toric IOLs (correct astigmatism)
•Extended Depth Lenses
• Most of NHS work is Mono-focal lenses
