Painless unilateral visual impairment developing gradually over a period of hours
The most common predisposing factors include hypertension, hypercholesterolaemia, diabetes, smoking and glaucoma.
Acquired or inherited coagulation disorders and hyperviscosity states predispose to venous thrombosis.
Definition
Circulatory disturbance of the central retinal vein usually at the optic nerve at the level of the lamina cribrosa of the sclera
Branch vein occlusion (in a main or a minor branch) occurs at the arteriovenous crossing causing the so-called crossing sign.
Occurrence
The most common primary vascular disease of the retina and the second most common circulatory disturbance of the ocular fundus after diabetic retinopathy
Occurs with similar frequency in both sexes; patients are usually over 65 years old (90% are over 50 years old).
In a 15-year population follow-up, 18 new branch vein occlusions and 5 central retinal vein occlusions were observed per 1 000 persons.
Venous occlusion is usually unilateral. In about 10%, an occlusion develops also in the other eye within a period of 5 years.
Predisposing factors
Hypertension, hypercholesterolaemia and diabetes are the most common. Ageing as such is also a predisposing factor.
Arterial changes, i.e. arteriosclerosis, and increased thrombotic tendency associated with the above-mentioned conditions as background factors
Untreated glaucoma (in about 20% of patients with central retinal vein thrombosis)
so-called drusen of the papilla (structurally narrowed optic disc area, due to drusen formation)
Symptoms and findings
Visual acuity varies from almost normal to counting fingers or discerning hand movements according to the location and severity of the occlusion.
Painless unilateral visual impairment over a period of hours
Often noticed first in the morning when the patient wakes up
Various transient visual disturbances, i.e. amaurosis fugax, may also occur in venous circulatory disorders, even if more seldom than in arterial disorders.
In a severe occlusion ophthalmoscopy shows
veins congested and tortuous
an oedematous retina and often also optic disc
widespread dot and blot haemorrhages in the retina (pictures 12)
In partial occlusion the findings are less severe, i.e. only consisting of congested and tortuous veins and some few isolated haemorrhages.
In hemispheric and branch vein occlusion the changes are only in the affected area of the fundus.
Branch vein occlusion is most commonly in the upper temporal quadrant.
Vision is impaired if haemorrhages and/or oedema reach to the centre of the macula.
Investigations and referral criteria
General examination (general practitioner, occupational health services) without delay
Blood pressure
Plasma glucose (glucose tolerance test if needed)
Lipids
Basic blood count with platelet count
Intraocular pressure
Investigations to reveal coagulation disorders in atypical cases (essential risk factors do not explain thrombosis), in bilateral occlusion and in patients with a family history of venous thrombotic tendency. See also Evaluation of Thrombophilia.
Urgent referral to ophthalmological examination in specialized care to assess the need of local treatment, if central vision is clearly impaired. Prompt initiation of VEGF inhibitor treatment may restore large part of vision.
In other patients, examination by an ophthalmologist is indicated within about a month.
Treatment and prognosis
According to the currently prevailing view, an effective immediate emergency medication does not exist. ASA is recommended if there are no contraindications.
LMW heparin has been shown to improve the prognosis of vision and to reduce the development of late complications (neovascularization and associated glaucoma).
It is essential to identify and treat the predisposing factors (see above).
Treatment targeted at the eye
The goal of treatment, started early enough by an ophthalmologist, is to prevent further loss of vision and, to the extent possible, to restore visual acuity.
Glucocorticoid may also be administered as an intravitreal implant, which remains effective for about 3 months.
A VEGF inhibitor is usually administered 3 times at 1-month intervals, and thereafter it is administered on an individual basis depending on the response.
Neovascularization can be treated by laser treatment of the ocular fundus.
If left untreated, extensive occlusion of retinal veins leads to neovascularization in the retina and optic papilla and in the anterior eye in the iris (rubeosis iridis) and the iridocorneal angle.
The prognosis of neovascular glaucoma is poor, i.e. a proportion of the eyes will become blind despite treatment (panretinal laser photocoagulation, peripheral retinal cryotherapy and diode laser photocoagulation of the ciliary body).