Visual defects Flashcards
What are the symptoms of visual loss?
Blurred/out of focus Glare Distorted vision Things look pale Shadow Floater
What is blurred vision normally due to?
Refractive problem ie. Cornea, lens, shape of eye
Macular problem
What is glare normally due to?
Corneal or lens problem
Often due to cataract
What is distortion normally due to?
Condition affecting retina E.g. Wet macular degeneration Macular hole Macular pucker Retinal detachment
What is things looking pale normally due to?
Optic nerve disease
E.g. Optic neuritis
Compressive optic nerve disease
Condition affecting retina
E.g. Wet macular degeneration
Central serous retinopathy
What is things floating normally due to?
Vitreous syneresis
Posterior vitreous detachment
Vitreous haemorrhage
What are the symptoms of cateracts?
Gradual onset
Symptoms depend on type of cataract
Blurred vision, glare, change in refraction
What are the signs and symptoms of dry age related macular degeneration?
Drusen - yellow deposits under the retina
RPE pigmentation
RPE atrophy
Gradual deterioration - sudden may mean wet ARMD
Particularly affects reading vision
What are the signs and symptoms of wet age related macular degeneration?
Rapid loss of vision
Distortion
How does antiVEGF work as a treatment for choroid neovascular membrane?
VEGF stimuates growth of choroidal neovascular membrane
antiVEGF binds to VEGF and prevents it acting on choroidal neovascular membrane
What is lens accommodation?
change in the shape of the lens in order to focus short or long distance
How does vision correction for far sight work?
When the eyeball is too short from front to back, light rays are focused at some point behind the retina - far sighted
A convex lens placed in front of the eye will provide the necessary refraction to allow near objects to be brought into focus
How does vision correction for short sight work?
When the eyeball is too long from front to back, parallel light rays converge at some point before the retina
A concave lens placed in front of the eye will provide the necessary refraction to allow distant objects to be brought into focus on the retinal surface
How do we see in colour?
in each cone there is one of 3 types of opsins
opsins = receptor proteins
each opsin works at different wavelengths (different colours) - blue, green, red
What causes an alternate perception of colour?
anomalous trichromat - all of their three cone types are used to perceive light colours but one type of cone perceives light slightly out of alignment
