Painful uninflammed eye

• Assessing the painful, uninflammed eye in primary care (BMJ, 2015)

• Eye conditions (Moorfields eye hospital)

Red eye

• Optic neuritis: painful loss of vision in a young woman. Classically causes a central scotoma, loss of colour vision and a relative afferent papillary defect (RAPD). Multiple Sclerosis is the most common cause of optic neuritis (also known as retrobulbar neuritis), accounting for 25–60% of cases. 

• Acute iritis: acute red eye & visual loss (not so profound) 

• Central artery occlusion would be rare in the absence of cardiovascular risk factors. 

• Red eye (CKS)

Acuity / Visual loss

• Acute or sub-acute loss of vision can be classified according to the site of the lesion within the visual pathway - in the anterior chamber, the vitreous, the retina, the optic nerve or the intracerebral optic pathway. 

• Giant cell arteritis: temporal headaches & visual disturbance not eye pain. Older.

• Retinal detachment - usually painless. 

• Retinal artery occlusion: sudden, painless loss of vision, uncommon. The pupil reveals a poor response to direct light but a normal consensual light response.  Fundoscopy reveals a pale and opaque retina as a consequence of oedema, thready retinal arteries and a fovea that resembles a 'cherry red spot'. This is an emergency requiring immediate referral

• Retinal vein occlusion (RVO): obstruction of the retinal venous system by thrombus formation and may involve the central, hemi-central or branch retinal vein. Central retinal vein occlusion (CRVO) results from thrombosis of the central retinal vein when it passes through the lamina cribrosa. It is classically characterised by disc oedema, increased dilatation and tortuosity of all retinal veins, widespread deep and superficial haemorrhages, cotton wool spots, retinal oedema and capillary non-perfusion in all four quadrants of the retina. In less severe forms the disc oedema may be absent. 

• The most common presentation is of unilateral, painless blurred vision, metamorphopsia (image distortion) ± a field defect (usually altitudinal). 

• multiple haemorrhages in all areas of the retina, with a few cotton wool spots, characteristic of central retinal vein occlusion

• Central retinal vein occlusion (CRVO): retinal veins are engorged and some haemorrhages are present. The condition is less abrupt than a central retinal artery occlusion. It occurs more commonly in the elderly. the patient frequently presents with sudden unilateral painless loss of vision or blurred vision, often starting on waking. There are widespread dot-blot and flame haemorrhages throughout the fundus associated with disc oedema. In severe cases, a marked afferent pupillary defect is present. There may occasionally be an associated retinal detachment.

• Branch retinal vein occlusions are due to blockage of just one of the four retinal veins, each of which drains about a quarter of the retina. Central retinal vein occlusion is due to blockage of the main retinal vein, which drains blood from the whole retina. In general, visual loss is more severe if the central retinal vein is blocked.

• Follow up as risk of the subsequent development of neovascularisation of the iris and consequential secondary glaucoma

• Acute closed angle glaucoma and anterior uveitis are both associated with eye pain, photophobia, change in pupil shape/size and loss of vision. The retina is difficult to visualise.  These two conditions should be treated as an emergency with immediate referral to an ophthalmologist

• Severely sight impaired (formally blind): VA <3/60 or VA >3/60 & contracted visual fields

• Certificate of vision impairment (CVI) (takes in to account both visual acuity and visual field measurements) must be completed by an ophthalmologist: formally certifies someone as sight impaired (previously referred to as partially sighted) or as severely sight impaired (previously referred to as blind). With the permission of the patient the CVI is shared so that the local authority they are ordinary resident in, is able to make contact with them to offer and explain the benefits of registration on a local sight register and to ensure services are accessible as appropriate

•  For Group 1 licence holders (which includes motor cars and motor cycles), VA must be ≥ 6/12 with both eyes open or in the only eye if monocular. There are greater requirements for Group 2 bus and lorry drivers. All drivers must also have a minimum field of vision. Any driver unable to meet these standards must not drive and must notify the DVLA immediately.

• Drugs: Most patients taking amiodarone will develop corneal microdeposits (reversible on withdrawal of treatment). These rarely interfere with vision; but drivers may be dazzled by headlights at night.

• All the drugs listed can have an effect on soft contact lens users; but only sulfasalazine will cause this characteristic staining.

• Drugs can affect a soft contact lens in five different ways – increasing lens deposits, discolouring the lens, dehydrating the lens, causing corneal oedema, decreasing lacrimation and decreasing eye movement/blink reflex. Some drugs may affect the lens in more than one way. For example, the oral contraceptive pill can cause decreased lacrimation, corneal oedema and encouragement of lens deposits.

Visual acuity

• Myopia. (short/near-sighted) Far away objects appear blurred and near objects appear clearly. The eyeball is too long, or the cornea is too steep, so images are focused in the vitreous inside the eye rather than on the retina. The near point is reduced. It will appear in young people during periods of growth.

• Astigmatism: The refractive error of the astigmatic eye stems from a difference in degree of curvature refraction of the two different meridians (i.e. the eye has different focal points in different planes). For example, the image may be clearly focused on the retina in the horizontal plane, but not in the vertical plane. Astigmatism causes difficulties in seeing fine detail, and in some cases vertical lines (e.g. walls) may appear to the patient to be tilted.

• Amblyopia: caused by either no transmission or poor transmission of the visual stimulation through the optic nerve to the brain for a sustained period or during early childhood, resulting in poor or dim vision. Amblyopia normally only affects one eye.

• Hypermetropia (long/far-sighted): defect of vision caused by an imperfection where the eyeball is too short, or the lens cannot become round enough, causing difficulty focusing on near objects.

• Presbyopia is a condition where the eye exhibits a progressively diminished ability to focus on near objects with age. The first symptoms are usually first noticed between the ages of 40–50.

Visual fields

• A pituitary tumour compressing the optic chiasm is the most likely cause of a bitemporal hemianopia. 

• Retinitis pigmentosa will cause peripheral visual field loss and tunnel vision

• Multiple sclerosis may cause optic neuritis which is commonly unilateral and may result in a central scotoma.

Resources:

• Assessing fitness to drive: a guide for medical professionals (DVLA)

• Snellen chart (eyetestnow.com)