Picture of abducens nerve palsy

Retinal vein occlusion

Flame and blot haemorrhages and cotton wool spots (retinal microinfarcts) are seen in a wedge distribution, appearances typical of branch retinal vein occlusion. Central retinal vein occlusion leads to these appearances throughout the retina (‘bloodstorm’).

Central retinal vein occlusion results in painless, sudden loss of vision. Branch retinal vein occlusion causes visual loss when the macula is involved, but if the macula is spared the occlusion may be an incidental finding.

Sudden painless loss of vision in one eye

The differential diagnosis of sudden painless loss of vision in one eye includes:

• Central retinal artery occlusion
• Central retinal vein occlusion
• Retinal detachment
• Vitreous haemorrhage
• Acute optic neuropathy 
• Migraine
• Giant cell arteritis

Nystagmus

It is described by the direction of the fast phase

When occurring as a result of a peripheral lesion, e.g. acute vestibular neuronitis, it is reduced by fixation and is associated with symptoms of vertigo

Downbeat nystagmus indicates a medullary-cervical junction lesion

Causes of multidirectional gaze-evoked nystagmus include multiple sclerosis and excess anti-epileptic medication.

Pendular nystagmus is caused by an inability to fixate, commonly congenital blindness.

Blurry vision

Iritis causes photophobia but will have an acute onset, usually with a red eye. These symptoms usually predominate so that iritis rarely presents with blurring of vision as a cardinal symptom. It is also usually unilateral.

Retinitis pigmentosa (RP) can occur in some types of renal failure, especially Alport’s syndrome, associated with deafness and a positive family history. The cardinal symptom in RP is poor night vision, but glare is not a typical description and symptoms are very gradually progressive from a relatively early age.

Glaucoma causes gradual loss of visual field and is rarely symptomatic in middle age, even with a positive family history. Glaucoma is not usually associated with renal failure or systemic medication.

Cataract is relatively common in renal transplant patients, as risk factors include renal failure and long-term systemic corticosteroid medication. The symptoms are typical, as vision becomes worse in bright light when the pupil constricts, confining the light path to the central part of the lens where it is thickest and the typical steroid-induced cataract most pronounced.

Antihypertensive medications cause many side effects, but blurring of vision is not usually one of them.

Scleritis

An adult who presents with red eyes and severe pain has scleritis until proven otherwise. This is much less common than iritis, and should prompt a search for underlying systemic vasculitis such as rheumatoid arthritis or Wegener's granulomatosis, the latter being most likely in this case in view of the upper respiratory tract symptoms.

Scleritis is a sight-threatening condition that requires treatment with systemic immunosuppression.

Causes of swollen optic disc

The optic disc is swollen. If vision were normal, this appearance could be due to papilloedema secondary to raised intracranial pressure (but not due to hypertension in the absence of any retinal haemorrhages or cotton wool spots). However, vision is impaired, making optic disc swelling secondary to an acute optic neuropathy the correct diagnosis.

The commonest cause of acute optic neuropathy in a young woman is multiple sclerosis. It will be important to pursue this possibility in the history:
▪ has this ever happened before?
▪ have you ever had problems with your arms / legs / walking / balance before?
▪ have you ever seen a neurologist about any problems before?

Aside from fundoscopy, key issues to check on examination of the eye are:
▪ visual acuity
▪ presence of a central scotoma
▪ impaired colour appreciation so that, compared with the normal eye, colours look washed out
▪ a relative afferent pupillary defect.
A full neurological examination to look for evidence of deficit elsewhere will be appropriate.

The eventual level of recovery of visual acuity is difficult to predict, hence a guarded prognosis must be given. Deciding whether or not to engage the patient in discussion about multiple sclerosis and/or further tests to pursue this diagnosis requires careful consideration.
Reference

Scleritis

Photophobia, visual blurring, keratitic precipitates (best seen with a slit lamp) and irregularity of the pupil are all features of iritis. Severe pain suggests scleritis and is not typical of iritis or the milder condition of episcleritis, where the inflammation usually affects just a sector of the globe of the eye. In scleritis the pain often disturbs sleep, and can literally drive people to bang their head against the wall and ask for the eye to be removed.

Scleritis is often associated with systemic symptoms and a manifestation of vasculitis: check an MSU for blood / protein, full blood count, renal / liver / bone function, inflammatory markers and autoimmune / vasculitic serology (in particular rheumatoid factor and serum ANCA).

Glaucoma

The peripheral rim of the optic disc is narrow and pale, the central cup is wide - features typical of chronic glaucoma.

Mydriatics: Drugs Used to Enlarge the Pupil

Fig 1: Dilated Pupils

Cyclopentolate 1%, Tropicamide 0.5%, Tropicamide 1%, Phenylephrine 2.5% Phenylephrine 10% can be used to dilate the pupils, but tropicamide (0.5% for children, 1% for adults) is best for diagnostic purposes, dilating the pupil for two to four hours by blocking the parasympathetic terminals in the pupillary constrictor muscle. Cyclopentolate works in a similar manner but lasts for six to eight hours.

Fig 2: Pupillary Constrictor Muscle

Phenylephrine drops dilate the pupil by stimulating the sympathetic system. They should be used with caution both in children and in adults with ischaemic heart disease because they can induce hypertension, exacerbate angina or induce arrhythmias.

Source: Fig1, Fig 2,

Diabetic Eye Disease

Foveal oedema

Fig 1: The fovea: this is the view of an eye a doctor sees looking,  just like a map. The central area of the retina is the 'macula', shown by the dotted black ring. Light focuses here, so any damage may affect a sight. The very central area, the yellow dot, is the the fovea.

Distortion and micropsia arise when the photoreceptors within the deeper layers of the retina become irregularly spaced. Such symptoms are typical of diabetic maculopathy, but not typical of proliferative retinopathy which is characteristically asymptomatic until an acute vitreous haemorrhage occurs.

Cataract occurs at an earlier age than usual in diabetes, but these symptoms are not typical.

Retinal vein occlusion may also present with foveal oedema but is less likely as a cause, especially in a relatively young woman without extra vascular risk factors.

Oral hypoglycaemic medication does not cause foveal damage. Although transient blurring of vision may occur when the blood sugar is first brought under control, this is more typical of type 1 diabetes, in which normalization is more rapid and more profound after using insulin for the first time.

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The appearances are of background diabetic retinopathy with hard exudates in a circular or circinate pattern at the fovea. Blot haemorrhages are also seen, but there are no new vessels to indicate diabetic proliferative retinopathy. The fact that the fovea is involved in this case will mean that the patient’s vision is affected and the eye can be described as showing ‘maculopathy’.

Diabetic maculopathy as seen here will be treated by focal or ‘grid’ laser coagulation, the primary goal being to seal leaking areas close to the fovea.

Wernicke’s encephalopathy

Wernicke’s encephalopathy typically presents with ophthalmoplegia (horizontal and vertical nystagmus, weakness / paralysis of the lateral rectus muscles, weakness / paralysis of conjugate gaze), ataxia (predominantly affecting stance or gait, and often without clear-cut intention tremor) and confusion.

Horizontal nystagmus

Vertical nystagmus

Lateral rectus muscle

Conjugate gaze