The bloody retina: C-19080 O/D.
Retinal vein occlusion
Retinal venous occlusion is usually sub-divided into central retinal vein occlusion (CRVO), hemi-retinal vein occlusion (HRVO) and branch retinal vein occlusion (BRVO), dependent upon the site of the obstruction and area of retina affected. The obstruction usually occurs at a point where an artery and vein cross. At these points, the artery and vein share a common sheath. Changes within the arterial wall cause it to thicken, and the relatively low-pressure vein, trapped within the common sheath, is compressed leading to obstruction of blood flow.
[FIGURE 1 OMITTED]
The obstruction to flow produces a back-pressure through the local venous system, and this leads to rupture of the capillaries, with intra-retinal haemorrhage and exudation ensuing. The area of retina affected will be one sector or quadrant in BRVO (Figure 1), the superior or inferior retina in HRVO, or all retinal quadrants in CRVO (Figure 2).
Dependent upon the extent and degree of obstruction to circulation, there may be scattered microinfarcts (cotton-wool spots) indicating ischaemia. Over time, ischaemia may cause new vessels to grow, either in the fundus where vitreous haemorrhage may result, or on the iris, which may lead to rubeotic glaucoma. Associated with vascular obstruction is usually a breakdown of the bloodocular barrier, leading to oedema, most evident in the macular area.
Diabetes affects the retinal capillaries, leading to capillary closure and leakage. Capillary closure leads to ischaemia, which may result in the formation of new vessels in the fundus or on the iris. The leakage gives rise to macular oedema, which reduces central vision, and to exudate formation. The exudates typically form in rings, which slowly enlarge. The fundal appearance of diabetic retinopathy includes scattered flame-shaped haemorrhages and some larger blot haemorrhages (Figure 3). The latter become more evident with increasing ischaemia, and may be a feature of the pre-proliferative state. Proliferative retinopathy is characterised by new vessels on the vascular arcades, or on the disc; and in some cases by new vessels on the iris (rubeosis iridis). The neovascularisation may be accompanied by the formation of sheets or bands of glial ("scar") tissue, which can lead to tractional retinal detachments, and the new vessels may lead to vitreous haemorrhage, with sudden loss of vision.
[FIGURE 2 OMITTED]
[FIGURE 3 OMITTED]
Sub-retinal new vessels may form in any condition that compromises the integrity of Bruch's membrane. The most common cause by far is age-related macular degeneration (AMD), but other causes include myopia, choroidal inflammatory conditions such as punctate inner choroidopathy or the presumed ocular histoplasmosis syndrome, trauma, and angioid streaks. Most problems resulting from choroidal new vessels (CNV) relate to loss of central vision because of elevation of the macula by sub-retinal fluid leaking from the vessels. Sometimes, however, the vessels can bleed, resulting in sub-retinal haemorrhage (Figure 4). There is usually some evidence of retinal elevation, and careful examination reveals that the bleed is deep into the retina (it is overlain by retinal vessels). On occasion, the bleed can be at high pressure, with breakthrough haemorrhage into all layers of the retina and into the vitreous. This usually results in marked visual loss.
The "valsalva manoeuvre" is forced expiration against a closed glottis: in other words, straining. When you strain, you drive up the pressure through the venous system, and this can result in small vessels bursting. In the fundus, this is usually seen as a circumscribed dark haemorrhage in the macular area, and it is often described as "sub-hyaloid" because of the way it seems to be contained. In fact, it is usually sub-internal limiting lamina, but it may break though into the vitreous when it becomes diffuse, with more generalised loss of vision.
Retinal arterioles may sometimes show localised dilatations in the macular area known as macroaneurysm. There is an association with hypertension, and there may have been previous embolic episodes. These macroaneurysms may rupture and bleed (Figure 5). The clinical picture is very similar to that seen with a valsalva bleed.
[FIGURE 4 OMITTED]
The retinal arterioles are able to alter their calibre in response to blood pressure changes. In the young, with healthy vessels, this happens uniformly in the retinal arterioles, so that in response to a rise in blood pressure there is a diffuse constriction of these vessels. In the ageing adult, however, with the (often widespread) vessel wall changes known as atheroma, the arterioles lose some of this capacity for constriction, so that it is seen in a patchy distribution. This is the most easily seen correlate of raised blood pressure in the fundus. Consequently, with reduced blood flow through constricted vessels, some areas of the retina may show signs of ischaemia, with flameshaped haemorrhages and microinfarcts (cotton wool spots). In severe cases, the optic nerve head may be swollen.
Inflammatory conditions affecting the retina and/or retinal vasculature can sometimes produce a haemorrhagic fundal appearance. This can result from a cytomegalovirus retinitis in a patient who is immunocompromised.
Changes in blood constituents can make the blood hyper-viscous, or produce a bleeding tendency, and these can give rise to a haemorrhagic fundus appearance. Examples of causative diseases are leukaemia and Waldenstrom's macroglobulinaemia. The fundus appearance is usually one of scattered blot haemorrhages (Figure 6).
Swollen optic nerve
When the optic nerves are swollen, eg in papilloedema, there are often flame haemorrhages in the retina surrounding the optic nerve head. The pathology and differential diagnosis of swollen discs is a subject in its own right, and will not be discussed further here.
When a retinal tear results from vitreous traction, a retinal vessel crossing the tear may also be torn or avulsed, and this may lead to an area of intraretinal haemorrhage, or more commonly vitreous haemorrhage.
Perhaps the first question is whether the patient has presented to you with visual loss, or is the haemorrhagic fundus picture a chance finding? Fairly rapid onset central visual loss suggests CNV or maybe a valsalva bleed; the former likely to be associated with distortion. Patients may describe quadrantanopic or hemi-field visual (field) loss with BRVO or HRVO respectively. The onset is usually rapid in these cases.
Does the patient have diabetes?
Are they hypertensive? The latter is associated not just with hypertensive retinopathy, but is often a feature of retinal arteriole macroaneurysm, and is often associated with retinal vein occlusions.
Does the patient have a history of inflammatory eye disease or systemic inflammatory disease? They may describe it as an autoimmune disease for which they take systemic steroids or other immunosuppressant drugs. Some immune-suppressed states, for example infection with human immunodeficiency virus (HIV), can result in cytomegalovirus retinitis.
Did visual loss or symptoms follow a bout of straining? This can result in a valsalva bleed, but sometimes retinal vein occlusions occur in otherwise fit young people during or just following a strenuous bout of physical activity, eg weightlifting.
Does the patient have a bleeding tendency, for example bleeding gums, or a tendency to bruise with minimal or no trauma?
When examining the retinal haemorrhage, consider the following features:
* Single or multiple
* Uniocular or binocular
* Associated signs
A single large central haemorrhage suggests bleed from a CNV or macroaneurysm (Figure 5), or a valsalva bleed. Multiple small bleeds restricted to the upper or lower macula suggests a macular branch vein occlusion. Multiple flame-shaped and moderately-sized blot haemorrhages in a quadrantic or hemiretinal distribution suggest a BRVO (Figure 1) or HRVO respectively. Multiple (usually large) flame-shaped and blot haemorrhages scattered throughout all four quadrants are the hallmark of CRVO (Figure 2). Vein occlusions may be associated with microinfarcts ("cotton wool spots"). Multiple flame-shaped haemorrhages distributed in association with the major vascular arcades are seen in some retinal inflammatory conditions, while haemorrhage in the peripheral retina is one of the signs seen in cytomegalovirus inflammation.
An isolated flame-shaped haemorrhage is sometimes seen in an otherwise healthy fundus. If there are scattered or widespread flame haemorrhages in both fundi, however, one must suspect that the patient has diabetes. Look for microaneurysms, and often there are also scattered blot haemorrhages (Figure 3). The latter lie in a deeper layer of the retina, whereas the flame haemorrhages are flame-shaped because they lie in the superficial, nerve-fibre layer, and the nerve fibre distribution imposes this shape on the haemorrhage. The diabetic fundus may show microinfarcts and/ or exudates, which may be scattered or forming rings (circinate exudates). In more severe retinopathy there may be new vessels peripherally or on the optic nerve head. Hypertensive retinopathy may present as bilateral scattered flame haemorrhages, with or without microinfarcts. Usually, it is evident that the retinal arterioles are very constricted. Because of atheromatous change, there is usually patchy constriction ("A/V" nipping), with some areas of normal arteriole calibre. In severe cases, the optic nerve head may appear swollen.
[FIGURE 5 OMITTED]
With bleeds from CNV and ruptured retinal macroaneurysms there is usually blood at various levels in and around the retina. With the former in particular, much of the blood is sub-retinal. To determine if the blood is sub-retinal, look to see the anatomical relationship between the blood and the retinal vessels: do the vessels pass superficial to the blood? If so, the bleed is most certainly sub-retinal.
If there is significant visual loss in the affected eye, look for an afferent pupil defect (APD). You can still examine for this if you have dilated only one pupil. Its presence suggests marked retinal damage or ischaemia, or possibly an associated optic neuropathy. Is the eye red with ciliary injection, and is there anterior chamber flare and cells, or vitritis, all of which suggest an underlying inflammatory aetiology? Some associated signs of diabetic retinopathy have been described above. In particular, where such cases are associated with visual loss you should look for macular oedema.
With large central haemorrhages, look for a retinal macroaneuysm on a branch arteriole. This is usually pale in colour, and several times the diameter of the parent vessel. With bleeds associated with CNV there may be a history of AMD and the affected eye may have developed distortion of central vision. Often, one can discern the signs of degenerative AMD (drusen and pigmentary disturbance). In this, as with many of the conditions described above, the fellow eye can give useful clues, but note the comment about APD before dilating both pupils. CNV often give rise to a clinically evident elevation of the central macula, and you may even see some CNV as greyish sub-retinal lesions. Those CNV associated with myopia will usually show a typical myopic fundal appearance, and there is a strong clue from the refraction.
Haemorrhage from haematological abnormalities usually takes the form of bilateralscatteredlargeblot haemorrhages, with no evidence of inflammation or ischaemia. Note the history.
In the peripheral retina, vasculitic haemorrhage may be accompanied by a patchy whitish sheathing of the retinal vessels, and retinitis gives rise to large haemorrhages interspersed with large areas of swollen, pale retina, an appearance reminiscent of a pizza.
If the patient has known diabetes, and the clinical signs are those of background retinopathy, then you should ask the patient if they attend for annual photoscreening that has been organised nationally. If they do not, then you should advise them how to access this service. If the visual acuity or clinical appearance suggest macular oedema, or if there are exudates encroaching on the central macula, or if you suspect new vessels, then ask the patient if they are already being seen and treated in an eye clinic. If they are, ask when the next review or treatment is scheduled. If their problem is being addressed, they should have an appointment for review or treatment within the next few days or weeks. If the patient indicates that they are not to be seen in clinic for many months, then they are probably referring to a routine follow-up visit. If you cannot be sure that the problem is already being addressed, then you should make an urgent referral to your local ophthalmic department, preferably to a retina specialist.
If the patient does not have known diabetes, but you find flame haemorrhages and microaneurysms suggestive of diabetes, then the patient should be referred to the general practitioner (GP) on an urgent basis. Similarly, if there are the bilateral scattered flame haemorrhages with arteriolar constriction suggestive of hypertensive retinopathy, then urgent medical intervention should be sought, within 24 hours, either from the GP or the local hospital emergency department.
If there is sub-retinal blood in the macular area, particularly with subretinal fluid and a complaint of distorted vision, then you should assume that active CNV is present. Same-day referral to an ophthalmic department, ideally directly to a macular or retinal clinic, should be made. If this cannot be done, you should consider sending the patient to the (ideally ophthalmic) accident and emergency department. Explain to the patient that the possibility of treatment may depend upon early assessment of the condition.
[FIGURE 6 OMITTED]
If the bleed has arisen from a visible macroaneurysm, or there is a good history of a valsalva-type bleed, then it is unlikely that any treatment will be offered in the short-term, so urgent referral is not strictly necessary. However, it is likely that the patient will be very anxious regarding their visual symptom, and early reassurance would be welcome. To this end, a prompt referral to a retinal specialist is helpful. Refrain from marking the request "urgent" which has become an overused term (when everyone is "urgent" then no-one is urgent!). There is an association between macroaneurysm and hypertension, and there may be benefit in asking the GP to review this.
Many patients with retinal vein occlusion receive no treatment for the affected eye, but some are treated for associated macular oedema or neovascularisation. Furthermore, there may be significant predisposing medical factors in these patients that warrant early assessment. For that reason, prompt referral to a retinal clinic is advisable. Same day referral to an emergency department is not necessary, but patients should be seen within 2-4 weeks. (1,2)
If a patient presents with a bilateral haemorrhagic fundus appearance that does not fit neatly into one of the categories above, and a history of a tendency to bleed easily (bruising, bleeding gums), and malaise or lethargy, then they may have a serious haematological abnormality. In such cases, systemic assessment becomes more important than ophthalmological appraisal. An appointment with the GP within 24 hours, or failing that an assessment at the local A&E department is advisable, and referral to the ophthalmology department can be by letter or fax. Patients with apparent vasculitis or retinitis also require urgent medical work-up, but in these cases early input by the ophthalmologist can aid diagnosis, and same-day assessment in the ophthalmic department is warranted. The ophthalmic department will almost certainly have established urgent referral pathways to physicians and other specialists.
Module questions Course code: C-19080 O/D
1. Which is TRUE? Unilateral widespread flame-shaped haemorrhages:
a) Are strongly suggestive of diabetes
b) Are rarely associated with raised blood pressure
c) Are usually associated with an afferent pupillary defect
d) Often result from central retinal vein occlusion
2. Which is TRUE? Sub-retinal haemorrhage:
a) May complicate myopia
b) Obscures the retinal vessels
c) Is a frequent finding in otherwise normal eyes
d) Is unlikely to be associated with a significant visual defect
3. Which is TRUE? Hypertensive retinopathy:
a) Is not associated with cotton wool spots (microinfarcts)
b) Is associated with retinal arteriolar constriction
c) Is not associated with swelling of the optic nerve head
d) Is associated with widespread microaneurysms
4. Which is TRUE? Valsalva bleeds:
a) Usually result from a haematological abnormality
b) Strongly suggest a diagnosis of diabetes
c) Require urgent treatment
d) Often present with central visual loss
5. Which is TRUE? In a patient with known diabetes:
a) Bilateral scattered blot haemorrhages demand urgent referral
b) Central sub-retinal haemorrhage demands urgent referral
c) Flame haemorrhages with cotton wool spots (microinfarcts) demand urgent referral
d) All of the above
6. Which is TRUE? Retinal vein occlusion:
a) Does not always produce visual symptoms
b) Constitutes an ophthalmic emergency
c) Is not associated with microinfarcts
d) All of the above
See www.optometry.co.uk/clinical. Click on the article title and then on 'references' to download.
Mark Benson, MB, ChB, MSc, FRCS, FRCOphth
Mark Benson is a director of the Midland Eye Institute, and consultant ophthalmic surgeon to the Heart of England NHS Trust, for which he runs retinal and cataract services. He is senior clinical lecturer to the University of Birmingham, a section editor for the journal Eye, and an examiner for the Royal College of Ophthalmologists.
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|Title Annotation:||CET: CONTINUING EDUCATION & TRANING|
|Date:||Jul 13, 2012|
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