Loss of Vision

These pages will help you formulate a list of differential diagnoses for some of the conditions you will face focusing upon visual loss. It should be emphasized that these are rough guidelines and each patient will have to be managed according to the specific clinical scenario.

The information in the following links is adapted from my text entitled "Ophthalmology in Primary Care" published by The Royal College of General Practitioners and available for purchase here.

These are general guidelines and each case should be taken on its merits. If concerned, contact the hopital eye service for advice.

Flashes and Floaters

Flashes and floaters are common symptoms, and in most cases represent no significant pathology, especially if they are long-standing. Possible causes include a posterior vitreous detachment, ocular migraine and vitreous haemorrhage.

Sometimes the posterior vitreous detachment causes a retinal hole to form, with the subsequent risk of retinal detachment.

Long-standing flashes and floaters – no need to refer.
Flashes and floaters of under six weeks' duration – refer soon via letter
Flashes and floaters with decreased vision – refer urgently.

Judge each case on its merits.

Certain risk factors should be taken into account, and these features will increase the suspicion of pathology:
- Myopia, particularly if highly myopic – look at the thickness of the lenses in the patient's glasses
- Younger age, i.e., under 55 years
- Pseudophakia/aphakia (previous cataract extraction – pseudophakia means replacement lens placed, aphakia means no lens placed).
All patients should be warned about the symptoms of retinal detachment and advised to contact the hospital eye service urgently if they experience the following:
- Sudden increase in floaters ('swarm of tadpoles').
- Solid or grey curtain moving across peripheral field of vision.

Is there a retinal tear or hole?

The only way to know is for an ophthalmologist to examine the retina with specialised lenses and visualise every part.
Ideally, this should be done for every patient but resources are not available for such blanket screening.
Optometrists are skilled at fundoscopy and many use slit lamp biomiscroscopy to assess the retina. They are thus a good initial port of call for such patients.

Is this a posterior vitreous detachment (PVD)?

Probably. The key question is whether this has caused a retinal tear.
PVD is a normal ageing phenomenon – it may occur without symptoms or cause flashes and floaters.
The flashes are usually short–lived but floaters may persist.
Classically, patients describe a single spider's web or floater complex which 'wobbles' in and out of vision.
Often flashes persist, particularly at night or on eye movement.

Gradual Blurring of Vision

May be related to cataract or AMD.

Patients who have had previous cataract surgery may have developed posterior capsular opacification, which warrants routine referral.

Sending the patient to their optician for assessment is prudent.

Recent treatment for Posterior Capsular Opacification - June 2017
Hi there, just a brief note to say how pleased I am with the service that you provided. I had cataract surgery in 2015 and after shortly afterwards my eyesight started to deteriorate, in one eye and then the other. Following several attempts to get to this corrected I had laser treatment for Posterior Capsular Opacification by Dr Alwitry.

He was very professional and I felt completely at ease during the treatment. My vision is massively improved. Just as he had predicted.

With much appreciation

Sudden Blurring of Vision

Is this central serous retinopathy?

Indications

Usually affects young or middle-aged men.
Relatively rapid onset of distortion and reduced vision in one eye.
Vision is not excessively reduced – usually in the region of 6/12.

What do I find?

Usually hard to see anything abnormal with the ophthalmoscope.

What do I do?

Refer urgent/soon via letter for confirmation of the diagnosis.

Is this wet AMD?

Indications

Usually older patient.
May have long history of gradual mild blurring of vision (pre-existing dry AMD).
Patients often say that straight lines do not appear straight (metamorphopsia). Ask the patient to look at a window frame or any form of grid and to describe what they see Peripheral vision is normal.

What do I find?

Visual acuity is reduced.
There may be haemorrhage at the macula. If you are skilled at fundoscopy you may see a greyish/green lesion below the retina.

What do I do?

Such patients may be eligible for photodynamic laser therapy to minimise the degree of visual loss. These patients should be referred immediately via letter to the closest PDT service for assessment. [As above.]

Sudden Loss of Vision (Bilateral)

Partial loss of vision

An occipital CVA will infarct the visual cortex on one side, resulting in a homonymous hemianopia of the contralateral side to the lesion.

Often the macula is spared, leaving the visual acuity intact.

If just a portion of the visual cortex is lost, the patient may only lose one corresponding quadrant of vision in each eye – a homonymous quadrantinopia.

Sudden blurring of vision

The degree of visual loss associated with the above conditions may vary, depending on the degree of the pathology. For example, a patient with a mild case of central retinal vein occlusion may have vision of 6/12, while another patient's vision may be reduced to hand motions.

Total loss of vision

In order suddenly to lose all vision in both eyes the patient would have to sustain a cerebrovascular occlusive event compromising both occipital lobes (visual cortices), optic tracts or radiations simultaneously.

The patient may have previously lost vision in one eye but only noticed it when they lost the vision in their good eye. They become concerned, check their vision in both eyes and notice that vision is poor bilaterally.

Very rarely patients will have retinal pathology affecting both eyes in rapid succession (may occur in untreated GCA).

Occasionally malingerers present claiming to have complete vision loss: watch how they walk and act. If the patient is completely blind he or she will not fixate on you and will struggle to negotiate obstacles.

Sudden Loss of Vision (Unilateral) - Central Field Defect

Is this optic neuritis?

Indications:

Patient usually young and female.
Onset usually sudden, but may get progressively worse over a two-week period, and then improves over the next four to six weeks.
Often described as a central black blob in the vision.

What do I find?

There will be a central field defect.
There will be a RAPD.
The optic disc is swollen in one third of cases
(Look closely at the macula to ensure that there is no haemorrhage there).

What do I do?

The patient should be referred soon. There is a significant risk that the patient is developing multiple sclerosis – check neurology.

Is this wet/haemorrhagic age-related macular degeneration (AMD)?

Indications

Usually older patient.
May have long history of gradual mild blurring of vision (pre-existing dry AMD).
Often begins with distortion followed by rapid reduction of vision associated with a macular haemorrhage.
Peripheral vision is normal.

What do I find?

Visual acuity is reduced.
There may be a significant haemorrhage at the macula.

What do I do?

If the patient has a large macular haemorrhage, the prognosis is poor. If there is no haemorrhage or limited haemorrhage, the patient may be eligible for photodynamic therapy. These patients should be referred immediately via letter to the nearest photodynamic therapy (PDT) service for assessment. If the diagnosis is uncertain the patient should be assessed at eye casualty.