Cataracts Flashcards
What are cataracts?
Cataract is the opacification of the crystalline lens that results from the normal ageing process, trauma, metabolic disorders, medications, or congenital problems.
What is the function of the lens?
The job of the lens is to focus light coming into the eye onto the retina at the back of the eye. It is held in place by suspensory ligaments attached to the ciliary body. The ciliary body contracts and relaxes to focus the lens. When the ciliary body contracts it releases tension on the suspensory ligaments and the lens thickens. When the ciliary body relaxes it increases the tension in the suspensory ligaments and the lens narrows. The lens is nourished by the surrounding fluid and doesn’t have a blood supply. It grows and develops throughout life.
What are the causes of cataracts?
Most cataracts develop over years with advanced age in the presence of risk factors. Other causes include ocular trauma and previous ocular surgery or laser treatment causing traumatic capsule damage. Certain medical conditions are associated with cataracts, particularly diabetes that increases the risk of cataract development by up to five times, but also hypertension, metabolic syndrome, renal impairment, systemic lupus erythematosus, and atopic dermatitis.
Congenital cataracts occur before birth and are screened for using the red reflex during the neonatal examination.
What are the risk factors for cataracts?
- Increasing age
- Smoking
- Alcohol
- Diabetes
- Steroids
- Hypocalcaemia
What are the clinical features of cataracts?
Symptoms are usually asymmetrical as both eyes are affected separately. It presents with:
- Very slow reduction in vision
- Progressive blurring of vision
- Change of colour of vision with colours becoming more brown or yellow
- “Starbursts” can appear around lights, particularly at night time
Briefly differentiate the changes in vision that occur with cataracts, glaucoma and macular degeneration
Cataracts cause a generalised reduction in visual acuity with starbursts around lights.
Glaucoma causes a peripheral loss of vision with halos around lights.
Macular degeneration causes a central loss of vision with a crooked or wavy appearance to straight lines.
What are the signs of cataracts on examination?
A key sign for cataracts is the loss of the red reflex. The lens can appear grey or white when testing the red reflex. This might show up on photographs taken with a flash.
What investigations should be ordered for cataracts?
- Dilated fundus examination
- Measurement of the intra-ocular pressure
- Glare vision test
- Slit lamp examination of anterior chamber
Briefly describe the management of cataracts
If the symptoms are manageable then no intervention may be necessary.
Cataract surgery involves drilling and breaking the lens into pieces, removing the pieces and then implanting an artificial lens into the eye. This is usually done as a day case under local anaesthetic. It usually gives good results.
It is worth noting that cataracts can prevent the detection of other pathology such as macular degeneration or diabetic retinopathy. Once cataract surgery is performed these conditions may be detected. Therefore, the surgery may treat the cataract but they may still have poor visual acuity due to other causes.
What is endophthalmitis?
Endophthalmitis is a rare but serious complication of cataract surgery. It is inflammation of the inner contents of the eye, usually caused by infection. It can be treated with intravitreal antibiotics injected into the eye. This can lead to loss of vision and loss of the eye itself.
What differentials should be considered for cataracts?
- Refractive error
- Dry eye
- Glaucoma
- Macular oedema
- Retinal detachment
- Optic neuritis
