Differentials
Refractive error
SIGNS / SYMPTOMS
Vision improves to normal with a correct spectacle prescription.
INVESTIGATIONS
Testing of vision with a pinhole will help indicate whether a change in glasses prescription could improve vision without surgery.
Dry eye
SIGNS / SYMPTOMS
Subjective and objective signs and symptoms including abnormal corneal and tear film findings.
INVESTIGATIONS
Using a drop of fluorescein and calculating the tear break-up time provides a guide to the degree of stability of the pre-ocular tear film and the likelihood of dry eye. Results with dry eye are likely to be abnormal (<7 seconds).
Glaucoma
SIGNS / SYMPTOMS
Possible reduced contrast and decrease in peripheral vision.
INVESTIGATIONS
Intra-ocular pressure measurement may reveal increased pressure.
Visual field testing may reveal classic glaucomatous visual field defects.
Loss of neuro-retinal rim tissue and enlarged vertical cup-to-disc ratio may be seen on ophthalmoscopy.
Epiretinal membrane
SIGNS / SYMPTOMS
Distorted or wavy vision, monocular diplopia, and aniseikonia.
INVESTIGATIONS
Fundus examination: evidence of epiretinal membrane or puckering of the macula.
Macular oedema
SIGNS / SYMPTOMS
Blurred or distorted vision.
INVESTIGATIONS
Swelling on examination or on macular imaging.
Retinal detachment
SIGNS / SYMPTOMS
Flashes of light and numerous little floaters. This may precede a "curtain" coming over the vision. The patient should be checked for an afferent pupillary defect.
INVESTIGATIONS
Fundus examination: evidence of tears, vitreous haemorrhage, or detachment.
Optic neuritis
SIGNS / SYMPTOMS
Decreased or patchy vision in one eye, pain on eye movement, or decreased colour vision.
Often associated with a diagnosis of multiple sclerosis.
INVESTIGATIONS
MRI is the most important test to evaluate the optic nerve and to look for any evidence of white matter changes in the brain, especially if the fundus appears normal on physical examination.
Defects on visual acuity and colour vision testing, and afferent pupillary defect.
Vitreous haemorrhage
SIGNS / SYMPTOMS
May have a history of trauma or poorly controlled diabetes mellitus.
A sudden decrease in vision or large patchy areas of blurry vision.
INVESTIGATIONS
Visual acuity reduced on testing.
On dilated fundus examination, there may be evidence of blood in the vitreous.
Age-related macular degeneration
SIGNS / SYMPTOMS
Wavy vision or a central area of vision that is blurry.
INVESTIGATIONS
Fundus examination: may be signs of wet or dry macular degeneration, such as drusen (retinal metabolic by-products that are normally removed) or sub-retinal fluid.
Infectious or inflammatory causes of decrease in visual acuity
SIGNS / SYMPTOMS
Symptoms and signs are specific to each individual diagnosis.
A complete examination should be performed to find any possible underlying cause of vision loss.
INVESTIGATIONS
Fundus and slit lamp examination are required. Other investigations depend on the symptoms and signs detected and the suspected diagnosis.
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