Ophthalmology - Cataracts, Age Related Macular Degeneration Flashcards
Cataracts - what is it?
Cataracts are where the lens in the eye becomes cloudy and opaque
This reduces visual acuity by reducing the light that enters the eye
Cataracts - what is the function of the lens, what is it held by?
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
Cataracts - what does the ciliary body do?
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
Cataracts - what are risk factors?
- Increasing age - most common cause
- Smoking
- Alcohol
- Diabetes
- Steroids
- Hypocalcaemia
Cataracts - what are the clinical features?
Gradual onset of:
- Reduced vision
- Faded colour vision - colours becoming more brown or yellow
- Glare: lights appear brighter than usual
- Halos around lights
- Progressive blurring of vision
- “Starbursts” can appear around lights, particularly at night time
Cataracts - what is a key sign for cataracts?
A key sign for cataracts is the loss or defect of the red reflex
Cataracts - what is the type of visual problems that you get with cataracts, OAG, 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
Cataracts - investigations?
- Ophthalmoscopy: done after pupil dilation. Findings: normal fundus and optic nerve
- Slit-lamp examination Findings: visible cataract
Cataracts - what are the non-surgical and surgical management options?
Non-surgical:
In early stages, age-related cataracts can be managed conservatively - prescribing stronger glasses/contact lens, or use of brighter lighting, help optimise vision but do not actually slow down the progression of cataracts, therefore surgery will eventually be needed
Surgical:
Cataract surgery involves drilling and breaking the lens into pieces, removing the pieces and then implanting an artificial lens into the eye
Cataracts - complications following surgery?
- Endophthalmitis - inflammation of the inner contents of the eye, usually caused by infection, treated with intravitreal antibiotics injected into the eye, this can lead to loss of vision and loss of the eye itself
- Posterior capsule opacification: thickening of the lens capsule
- Retinal detachment
- Posterior capsule rupture
Age Related Macular Degeneration (ARMD) - what is it?
Age-related macular degeneration is a condition where there is degeneration in the macula that cause a progressive deterioration in vision
Degeneration of the central retina (macula) is the key feature with changes usually bilateral
ARMD - what is the key finding you can see on fundoscopy?
ARMD is characterised by degeneration of retinal photoreceptors that results in the formation of drusen, can be seen on fundoscopy and retinal photography
ARMD - what are the two types?
Dry (90% of cases)
Wet (10% of cases)
ARMD - what are the four layers of the macula?
The macula is made of four key layers:
- At the bottom, there is the choroid layer, which contains blood vessels that provide the blood supply to the macula
- Above that is Bruch’s membrane
- Above Bruch’s membrane there is the retinal pigment epithelium
- Above that are the photoreceptors
ARMD - what are Drusen?
Drusen are yellow deposits of proteins and lipids that appear between the retinal pigment epithelium and Bruch’s membrane
Some drusen can be normal, with normal drusen being small (< 63 micrometres) and hard
Larger and greater numbers of drusen can be an early sign of macular degeneration
They are common to both wet and dry ARMD
ARMD - which of wet or dry ARMD has the worst prognosis?
Wet
ARMD - what are the classical features of dry MD?
dry macular degeneration
- also known as atrophic
- characterised by drusen - yellow round spots in Bruch’s membrane
ARMD - classical features of wet MD?
also know as exudative or neovascular macular degeneration
characterised by choroidal neovascularisation
leakage of serous fluid and blood can subsequently result in a rapid loss of vision
carries worst prognosis
ARMD - risk factors?
- Age
- Smoking
- White or Chinese ethnic origin
- Family history
- Cardiovascular disease
ARMD - what is the classical type of vision loss to differentiate it from other conditions?
ZeroToFInals: There are some key visual changes to remember for spotting AMD in your exams:
- Gradual worsening central visual field loss
- Reduced visual acuity
- Crooked or wavy appearance to straight lines
ARMD - what are the findings you are looking for on examination?
- Reduced acuity using a Snellen chart
- Scotoma (a central patch of vision loss)
-
Amsler grid test can be used to assess the distortion of straight lines
- Fundoscopy, Drusen are the key finding
ARMD - management of dry ARMD?
Lifestyle measure that may slow the progression:
- Avoid smoking
- Control blood pressure
- Vitamin supplementation has some evidence in slowing progression
ARMD - management of wet ARMD?
Anti-VEGF medications are used
Vascular endothelial growth factor is involved in the development of new blood vessels in the retina
So, medications such as ranibizumab, bevacizumab and pegaptanib block VEGF and slow the development of new vessels
They are injected directly into the vitreous chamber of the eye once a month
They slow and even reverse the progression of the disease
Start within 3 months
