EYE-REVISE

• Cataract = opacification of the crystalline lens

• 3 types:

  • nuclear sclerosis - lens turns yellow / brown in colour​

  • cortical 

  • posterior subcapsular

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Symptoms

• gradual loss of vision​ - general blurring

• glare

• Risk factors / causes

• age - most common cause, typically occur over 65 years ​

• ocular disease e.g. uveitis

• systemic disease e.g. diabetes

• traumatic 

• drug induced - topical or systemic steroids

• congenital 

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Management

• refractive - cataracts cause myopic shift in vision - can manage with myopic (minus) lenses in some cases​

• surgery - phacoemulsification (breakdown and removal of opaque lens) and implantation of artificial intraocular lens

• Indications for treatment:

  • lifestyle factors e.g. professional diver​

  • functional factors - impairment of vision hinders day to day activities

  • disease factors - cataract blocks view of back of the eye, preventing retinal screening in diabetic patients, for example

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Cataract surgery

• phaco tip used to breakdown the cataractous lens - uses ultrasound ​

• broken down lens is aspirated (sucked out) 

  • known as phacoemulsifcation​

• leaves behind transparent posterior layer - the posterior capsule which is normally situated behind the lens

• eye is left very hypermetropic (long-sighted) 

• artificial lens (intraocular lens, IOL) implanted onto the posterior capsule

• can be performed as day surgery in vast majority of cases

• 3 measurements required to calculate power of IOL

  1. corneal curvature​

  2. axial length of eye

  3. A-constant of the lens

• Anaesthesia for surgery - 2 options:

  1. general anaesthesia​

  2. local anaesthesia - methods:

     • sub-tenon injection​

     • peri-bulbar injection

     • topical - eyedrops

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Complications of surgery

• rupture of posterior capsule - 3%​

• endophthalmitis - 0.1% --> emergency, can cause blindness if delay in diagnosis of treating

• haemorrhage

• uveitis

• macula oedema (leakage of fluid from blood vessels into the macula causing swelling)

• retinal detachment

• posterior lens capsule opacification - clouding of the transparent posterior layer

  • late complication (months or years) 

  • may require laser treatment with Nd:YAG infrared laser​