Gradual Loss of Vision

There are a number of reasons why a patient's vision may be gradually declining. This can be very worrying for some patients. In others, the loss is so subtle that it is only picked up on routine screening by the optician. When the patient presents, it is important to take a thorough history as the patient's perception of visual impairment (I can't read the paper) may be different than yours (he can see the words but they appear distorted rather than blurred, making the reading difficult).

Many causes of gradual visual loss can be diagnosed on history and examination alone with only the most basic additional investigations. This record will provide you with an outline of how to assess the patient presenting with gradual loss of vision and the possible diagnoses and features that may help confirm these. Follow the links to find out more about the diagnoses themselves.

History

A routine history is mandatory and will often guide you to a possible cause. Specifically ask about:

• What is the problem?
  • Unilateral vs. bilateral
  • Blurred vision: the whole field? Close, distance or both?
  • Restricted visual field? Often noted following difficulties in driving, knocking into things at the periphery of vision
  • Vision not blurred but distorted (e.g. dent in printed words, window frame, objects appearing smaller or larger)
  • Bits of visual field missing altogether: central vs. peripheral, what is the remainder of the vision like?
• Onset: when, any significant health issues at that time?
• Progression: slow and steady decline, step-wise drops in visual acuity?
• Are there any associated factors? Pain (very important diagnostically, see below), redness, visual phenomena e.g. halos, flashes of light.
• Any precipitating factors? Specifically ask about changes over the course of a day, better in the day or at night?

Other important aspects of the history include the past ocular history, medical history, family history, medication and social history:

• Is this affecting their life-style?
• Are there implications with regards to their work or driving?
• Will this mark the loss of their independent living?

Examination

Important points to note on examination are:

• The visual acuity of both eyes. Does this improve using a pinhole?
• The red reflex: a media opacity (appears black against the red reflex) suggests a corneal, lens or vitreous problem. To localise the site of the opacity with respects to the pupil [lens]:
  • Slowly shift the direction of your ophthalmoscope light
  • Look at the direction in which the opacity appears to move in relationship to the pupillary (central) axis
  • If there is no 'movement' of the opacity, it lies within the pupil [lens]
  • If the opacity 'moves' in the same direction, it is anterior to the lens [cornea]
  • If the opacity 'moves' in the opposite direction, it is posterior to the pupil [posterior lens or vitreous]
  If the media is clear, it is more likely to be a retinal or optic nerve disorder.
• If there is a normal red reflex, take a good look at the fundus.
• Do a functional testing of visual field, pupils, optic nerve and macula.

Our record on Examination of the Eye explains in detail how to do all these tests. Complement your examination with a blood pressure check and urine glucose test. A neurological examination may be necessary if everything else seems completely normal.

• Refractive error - this is characterised by an improvement of the visual acuity with the use of a pin-hole (if you don't have a specific occluder with pin-holes, a biro point-sized hole in a stiff piece of cardboard will do). Refer to the optician.
• Cataracts - the patient often complains of glare in dark conditions (and so difficulty in driving at night) and may complain that colours appear more dull than they used to. There may be an abnormal red reflex and in advanced cases, the cataract may be visible to the naked eye (this is increasingly rare these days). Other aspects of the examination should be normal unless there is concurrent pathology. Refer routinely.
• Age-related (senile) macular degeneration (ARMD) - there is a gradual central field loss possibly preceded by distortion of straight lines (door frame, lines of print appear abnormal) which can be verified on an Amsler grid (see examination of the eye). Some experience a blue-yellow colour abnormality. It is bilateral but not symmetrical. Refer routinely. Any sudden drop in visual acuity suggests either the 'wet' form of ARMD or another pathology - refer urgently (within 48h).
• Certain types of glaucoma - chronic open angle glaucoma is most commonly picked up through screening. If it is so advanced that the patient is the first to notice it, very little can be done. It is characterised by a progressive peripheral visual field loss and cupping of the optic discs (this means that the ratio of the central area of the optic disc: the peripheral rim gets larger as the rim thins out - in extreme cases, it may not be there at all). The degree of urgency depends on how advanced the damage is.
• Diabetic retinopathy - look for this in the poorly controlled diabetic or the pregnant diabetic patient (who should be on a more intense screening programme throughout her pregnancy anyway) particularly. The problem may due to the diabetic microvascular problems (i.e. exudates and haemorrhages), to associated pathology (diabetic cataract) or unrelated pathology (e.g. glaucoma). Refer promptly (within a week) as the problem can be arrested and complications minimised.
• Optic nerve compression - these are rare but should be considered if there is a history of headaches and if you find any neurological or endocrinological abnormalities (e.g. acromegaly) on examination. Look for a relative afferent pupillary defect (not present in the above conditions), a pale or swollen optic disc (the margins are not clear) and visual defect abnormalities such as bitemporal defects.
• Drug toxicity - consider this in the patient on hydroxychloroquine (maculopathy), for example or on systemic steroids (cataracts and glaucoma). Excessive alcohol or smoking can also affect the visual acuity through microvascular effects. The only treatment is discontinuation of the offending drug but refer to confirm the diagnosis. The ophthalmologist will liaise with the prescribing doctor as to the solution thereafter. In some cases, such as where there is tamoxifen retinopathy, a balance will have to be struck between the necessity of the drug and the visual consequences.
• Hereditary Retinal Dystrophies (see our dedicated record) - these are rare and depending on the exact problem, present anywhere from early childhood to middle-age. Some are rapidly progressing, others very slow. Typical features particularly include nyctalopia (difficulty in seeing at night) and intolerance to light. Poor appreciation of movement in the peripheral visual field may also be a feature. Ask about similar problems in family members (who may not have been diagnosed). Children should be referred more promptly than adults for whom a routine referral is fine. These patients will need genetic counselling as well as support where the prognosis is poor.

This is much rarer and tends to suggest a more sinister pathology. There may be slowly a progressive neoplastic (e.g. choroidal melanoma) or inflammatory process (e.g. chorioretinitis) or a systemic problem (e.g. sarcoidosis or collagen vascular disease). Consider lesions on the optic nerve (e.g. granuloma or neuroma). Be guided by the patient's past medical history, a neurological as well as ocular examination and baseline blood tests (these can be carried out at the same time as a referral is made). All these patients should be referred. Referral is more urgent than with painless conditions and patients should really be seen within a few days.

Most of these patients need referring to your local ophthalmology team for confirmation of the diagnosis and subsequent management. If your examination appears completely normal, consider referring the patient to an optician in the first instance - it may be a simple problem of a refractive error. In some areas, there are partnerships between community opticians and ophthalmologists to speed up the referral process (e.g. for simple cataracts). Generally, referral need not be urgent if the loss is gradual but be guided by the level of distress experienced by the patient and if in doubt, discuss this with your local team. As a rule of thumb, those conditions that need more prompt attention tend to be:

• Those whose progression can be slowed or stopped (e.g. diabetic retinopathy)
• Where sinister pathology is suspected (e.g. choroidal melanoma)
• Where the loss is bilateral
• Where there is pain

The possibility of blindness is a terrifying thing in all people. In the younger person, there are huge issues relating to socialising, studying, getting a job. In the older person, independent living may be jeopardised. In all patients, there may be existential questions about self-definition, fear of isolation and the possibility of depression. This needs to be acknowledged yet sensitively balanced with the reality of the condition e.g. it is fairly unusual for conditions to lead to total blindness and the patient can often learn to use their residual vision. There is a range of practical support (visual aids, mobility training, educational support for children) and there are many support groups that can offer help, whether general (e.g. the RNIB) or specific (e.g. the Macular Disease Society).

You will find more information on management and support of these patients in our relevant records (see links above) and in our record on Blindness and Partial Sight.