Fig. 25.1 Anatomy of the eye. Reproduced with permission from Dodson, Paul, Diabetic Retinopathy: Screening to Treatment 2008, Oxford University Press.
Ophthalmology is the speciality concerned with diseases of the eye, the visual pathways of the CNS, ocular movements, and the adnexae (eyelids and orbits). It is a highly practical speciality with microsurgery, laser interventions, and minor operations forming a significant proportion of the workload. Patients of every demographic are seen from premature babies with retinopathy of prematurity to the very elderly with age-related macular degeneration (AMD) and glaucoma. The eye casualty offers the richest environment for learning about acute ophthalmic presentations (red eye/visual loss). Aim to spend at least two or three sessions here if possible. (See Fig. 25.1 and Fig. 25.2 for anatomy.)
Fig. 25.1 Anatomy of the eye. Reproduced with permission from Dodson, Paul, Diabetic Retinopathy: Screening to Treatment 2008, Oxford University Press.
Fig. 25.2 Anatomy of the fundus. Reproduced with permission from Dodson, Paul, Diabetic Retinopathy: Screening to Treatment 2008, Oxford University Press.
Eye casualty offers many opportunities to see examples of acute ophthalmology such as trauma, chemical injuries, orbital cellulitis, corneal foreign bodies, microbial keratitis, acute iritis, acute glaucoma, retinal vascular disease, optic neuropathies (ischaemic/demyelinating), ocular motility disorders (compressive and microvascular cranial nerve disorders), and central causes of visual loss (migraines, TIAs, stroke, CNS tumours, etc.). Ensure you gain experience in distinguishing causes of red eye and visual loss on clinical assessment.
The following four disorders form the majority of the ophthalmic outpatient workload. Try to gain an appreciation of how referrals are made, patients are assessed, treatments are delivered (including the timescales of urgency in each case), and progress assessed.
AMD is the most common cause of blindness in the elderly. Dry (atrophic) AMD may require visual rehabilitation and risk of progression reduced with vitamin supplements and smoking cessation. Wet (exudative) AMD is treatable and involves regular visits for treatment with intravitreal injections and assessing response to therapy.
Cataract is a common cause of reversible visual impairment. It is usually age related but accelerated by trauma, diabetes, and steroids.
Glaucoma is a major cause of world blindness and remains asymptomatic until late. Intraocular pressure (IOP) is the major modifiable risk factor, lowered by drops or by surgery to prevent progressive, irreversible visual field loss.
Diabetic retinopathy remains the commonest cause of blindness in the working population, either through complications of proliferative diabetic retinopathy (more common in type 1 DM), or diabetic macular oedema (more common in type 2 DM).
This is the most commonly performed operation by the NHS with >350,000 operations annually.
YAG (yttrium aluminium garnet) capsulotomy is performed for patients with posterior capsular opacification (clouding of the lens capsule) as a late complication following cataract surgery (Fig. 25.3—note the clear central visual axis created by an opening produced by the YAG laser in the posterior capsule) and YAG peripheral iridotomy to create a small hole in the iris and break an attack of acute angle-closure glaucoma (see 
p. 503 and Fig. 25.5). Pan-retinal photocoagulation is used to treat patients with proliferative diabetic retinopathy (note the circular white/black laser scars which vary in appearance depending on laser uptake and interval following laser in Fig. 25.4) and macular laser therapy may be used to treat macular oedema secondary to diabetes or retinal vein occlusion.
Figs 25.3 and 25.4 Ocular appearance following different forms of laser treatment. Photos courtesy of Mr. Martin Leyland.
This is an operation for patients with advanced or rapidly progressing glaucoma. The operation aims to create a communication between the anterior chamber and the subconjunctival space, to achieve long-term control of IOP without the need for drops.
Vitrectomy is an operation commonly performed for retinal detachment in which the vitreous gel is removed, the retina is flattened, and the retinal break is sealed.
Squint surgery involves adjusting the length and insertion of the extraocular muscles in children to improve binocular visual development and treat amblyopia, and in adults to alleviate diplopia and improve cosmesis. It often requires a GA.
These are commonly required to deliver biologic drugs (commonly against vascular endothelial growth factor (VEGF)) into the vitreous cavity for the treatment of wet (exudative) macular degeneration, retinal vein occlusion, or diabetic macular oedema. Antibiotics and anti-inflammatory agents can also be delivered by this route.
Red eye is one of the most common acute presenting complaints in ophthalmology. Careful clinical assessment (history and examination) will identify the cause and appropriate management strategy.
• Unilateral red eyes with pain and visual loss require urgent ophthalmic referral suggesting potentially sight-threatening pathology
• Bilateral red eyes without pain and unaffected vision may be treated in the community
This is an ophthalmic emergency, an acute severe rise in IOP results from obstruction of the drainage angle of the eye.
Include unilateral severe pain/headache, nausea/vomiting, haloes, and reduced vision (secondary to corneal oedema) and may be provoked by poor light environments/prone posture.
An ovoid, mid-dilated pupil may be observed (ischaemic iris; Fig. 25.5). IOP may be 60–80 mmHg (normal IOP <21 mmHg). Bimanual palpation of an eye through a closed eyelid will reveal a unilateral hard eye.
Intensive topical antihypertensive drops, topical steroids, pilocarpine to open the drainage angle, and systemic acetazolamide (Diamox®).
Management options include alpha agonists (apraclonidine), beta antagonists (timolol), carbonic anhydrase inhibitors (oral acetazolamide or topical dorzolamide), parasympathomimetics (e.g. cholinergic agents like pilocarpine), and prostaglandin analogues (latanoprost). Once IOP is reduced, corneal oedema should resolve and clear the view for YAG iridotomy laser to be performed. This is the definitive treatment which must be performed on both eyes to prevent contralateral angle-closure glaucoma. The anterior segment appearance following laser iridotomy is shown in Fig. 25.5.
Fig. 25.5 The appearance of a laser peripheral iridotomy opening following acute angle-closure glaucoma. Image courtesy of Mr. Imran Yusuf.
Age, female sex, hypermetropia, and those of Central or South-East Asian origin.
Bacterial keratitis in contact lens wearers necessitates urgent treatment to prevent corneal ulceration, which may 
corneal perforation in extreme cases. Always ask about contact lens use in any patient with a (usually unilateral) red eye.
Include pain and photophobia, and vision may be reduced if the infection results in axial corneal opacity or secondary inflammation.
Note the corneal infiltrate (opacity) typical of bacterial keratitis (Fig. 25.6), and the advanced corneal ulcer with large central ring infiltrate, corneal thinning, and hypopyon seen in advanced bacterial keratitis with a very inflamed eye (Fig. 25.7).
Figs 25.6 and 25.7 Examples of the clinical appearance of microbial keratitis Photos courtesy of Mr. Martin Leyland.
May require a diagnostic corneal scrape before treatment with broad-spectrum topical antibiotics. Quinolones (ofloxacin) are typically used to cover Pseudomonas spp., an important cause of contact lens-related keratitis; chloramphenicol has no action against this organism and should not be used. Treatment is typically hourly drops for 48 hours, tailored according to clinical response and microbiology Gram stain/sensitivities.
Anterior uveitis commonly causes recurrent red eye, pain, photophobia, and reduced vision in susceptible patients.
The pupil may be irregular due to iris adhesions (Fig. 25.9) with appearance of an irregularly shaped pupil and a hypopyon (fluid level of sterile pus in the anterior chamber: Fig. 25.8) may be visible. White blood cells can be visualized directly with the slit lamp, IOP is measured and dilated fundoscopy performed to exclude posterior uveitis.
The HLA-B27 haplotype (typical of seronegative spondyloarthropathies) predisposes to recurrent iritis which is often more severe.
Figs 25.8 and 25.9 Clinical appearance of anterior uveitis with hypopyon (left) and posterior synechiae (right). Photos courtesy of Mr. Martin Leyland.
With sarcoid, IBD, etc. may be excluded by serum assays and imaging (CXR) if iritis is recurrent, bilateral, or severe.
Is with frequent topical steroid drops, tailored over 4–6 weeks depending on severity. Topical steroids, in any context, must not be used for >4 weeks without monitoring by an ophthalmologist: secondary glaucoma or herpes simplex keratitis may progress undetected and cause permanent visual loss. Posterior uveitis (TB, syphilis, toxoplasmosis, etc.) is often sight-threatening and may require vitreous sampling, oral or intravitreal treatments, and a more aggressive diagnostic workup.
This is the most devastating complication of any intraocular procedure (cataract surgery, trabeculectomy, vitrectomy, intravitreal injection, etc.).
Results from bacterial entry into the eye, commonly Staphylococcus. epidermidis, Staph. aureus, and Streptococcus spp.
Describes haematogenous seeding of bacterial/fungal/protozoal infection into the eye often in immunosuppressed patients. Treatment is of the underlying cause, but a careful search for a systemic focus may be required (blood culture, echocardiography, etc.) as directed by history, examination, and suspected causative organism.
Is typically with red eye, grossly reduced vision, relative afferent pupillary defect (RAPD), and hypopyon visible in the anterior chamber, with vitritis.
Urgent diagnostic sampling of vitreous ± anterior chamber fluid is required with intravitreal injection of antibiotics (commonly ceftazidime and vancomycin), topical steroids, antibiotics and dilating drops, with oral antibiotics (typically quinolones), sometimes with use of oral steroids after 24 hours. Early vitrectomy is advised if vision or light perception or worse to remove pus/cytokine soup from the vitreous cavity.
Scleritis causes unilateral red eye with deep pain (like toothache) which may wake the patient up at night.
Reveals injection of deep scleral vessels, and may reveal scleral thinning with appearance of darker hue due to exposure of underlying choroid. Scleritis is vasculitis of the sclera and systemic vasculitides are associated (e.g. RA, polyarteritis nodosa, granulomatosis with polyangiitis (formerly known as Wegener’s granulomatosis) must be excluded with serum assays.
Topical steroids and oral NSAIDs are required; rarely scleral thinning and perforation may occur. Referral to a rheumatologist is advised for treatment of the underlying systemic disorder.
This may also cause red eye in patients with connective tissue diseases. Corneal perforation may occur if inappropriately managed.
Conjunctivitis may be allergic, bacterial, viral (commonly adenovirus), or have another cause. Enquire about recent history of URTI or affected contacts—adenoviral conjunctivitis is highly contagious. Although this may present unilaterally, typically the second eye may become affected 2–3 days later (Fig. 25.10). Dryness/grittiness is typical and it is usually a self-limiting condition. The treatment is symptomatic (regular lubricants). Photophobia suggests secondary keratitis, which requires topical steroids. Bacterial conjunctivitis is more purulent and commonly unilateral.
Fig. 25.10 Bilateral viral conjunctivitis. Photo courtesy of Mr. Martin Leyland.
Describes conjunctivitis within the first week of life and is an emergency: corneal scarring may result. Chlamydia and gonococcal conjunctivitis may affect teenagers/young adults who are sexually active; specific treatment and genitourinary medicine referrals are mandatory. Allergic conjunctivitis: commonly causes bilateral itching with red eyes with chemosis (conjunctival oedema), typically in atopic patients (history of asthma, eczema, etc.) and may be seasonal. Follicles are often demonstrated on the tarsal conjunctiva. Eversion of upper lid may reveal flat-topped lesions—papillae—a sign of severe allergy. Any corneal involvement is sight-threatening and requires topical steroids. Topical and oral antihistamines/mast cell stabilizers are often sufficient.
Evaporative dry eye is very common and may result in mild conjunctival hyperaemia. It occurs due to blockage of Meibomian glands, with secondary reduced lipid content within the tear film and consequent rapid tear film evaporation. Gritty/burning eyes are the presenting symptoms.
A Meibomian cyst (chalazion) may occur intermittently secondary to viscous Meibomian gland secretions blocking the Meibomian ducts.
May reveal crusting around the base of the eyelashes, and fluorescein examination may reveal multiple, tiny epithelial erosions secondary to rapid evaporation of the tear film.
Is regular lubricants and lid hygiene to unblock the Meibomian gland ducts and encourage physiological secretions to restore the composition of the tear film.
Is a typically unilateral, harmless collection of blood under the conjunctiva.
It appears uniformly red (Fig. 25.11), and may cause mild ocular discomfort if large.
Fig. 25.11 Subconjunctival haemorrhage. Photo courtesy of Mr. Martin Leyland.
If spontaneous, BP measurement is required to exclude systemic arterial hypertension. Patients on anticoagulant and antiplatelet therapies are also at higher risk. Topical lubricants are often sufficient to alleviate discomfort if present. Traumatic subconjunctival haemorrhages require a complete examination to exclude associated ocular injuries (hyphaema, orbital blowout fracture, etc.).
The visual system is best considered from the tear film anteriorly to the primary visual cortex posteriorly with cornea, anterior chamber, lens, vitreous, retina, optic nerve, optic chiasm, and optic radiations between them. Pathology of any aetiology (infection, inflammation, neoplasia, etc.) affecting any of these structures can result in acute visual loss. Keep your differential appropriately broad, and use information from history and examination and knowledge of the visual pathways to determine the structure(s) affected and the underlying pathology.
Determine whether visual loss is unilateral or bilateral, painful or painless.
Causes a dramatic, unilateral, painless, severe loss of vision due to retinal infarction.
Visual acuity is often reduced to counting fingers or worse with a dense RAPD. Retinal examination reveals retinal pallor and a ‘cherry red spot’ at the macula due to an intact choroidal circulation. A Hollenhorst plaque (cholesterol embolus) may be demonstrated in a proximal vessel secondary to rupture of atheromatous plaque from the ipsilateral carotid artery. A branch retinal artery occlusion occurs when only a branch of the retinal artery is occluded, with retinal pallor/oedema visible in the distribution of the occluded retinal arteriole manifesting as partial visual field loss.
Acute treatment (<6 hours after the onset of symptoms) may involve dislodging the embolus (with drops, ocular massage, hyperventilation, etc.) into a smaller arteriole. Irreversible visual loss is the rule, which may be altitudinal if the embolus affects only a branch retinal artery rather than the central retinal artery.
Contributory systemic cardiovascular risk factors must be addressed: TIA clinic referral and carotid Dopplers/echocardiogram are required.
Giant cell arteritis must be excluded with ESR/CRP if >50 years of age. Amaurosis fugax describes transient monocular visual loss, and is considered a TIA variant affecting the central retinal artery.
Results in acute-onset unilateral visual loss, although vision may be relatively preserved in comparison to central retinal artery occlusion. A RAPD may be present.
Include atherosclerosis (retinal vein is compressed by a rigid adjacent retinal artery), or hypercoagulable states (myeloma, Waldenström’s macroglobulinaemia, dehydration, etc.)—recall Virchow’s triad.
Reveals retinal haemorrhages in all quadrants (if central) or sectoral (if branch of retinal vein only), with cotton wool spots and optic disc swelling. Visual loss is due to macular oedema and/or retinal ischaemia.
Involves addressing cardiovascular risk factors, reducing IOP with topical drops if elevated. Retinal laser is required if new vessels are present or there is retinal ischaemia. Macular oedema may be treated with laser, intravitreal steroid, or anti-VEGF injections.
Fig. 25.12 Typical appearance in central retinal vein occlusion. Photo courtesy of Mr. Imran Yusuf.
Is usually non-vasculitic (i.e. caused by atherosclerosis rather than temporal arteritis). Typically occurs over the age of 55 with males and females being equally affected.
A RAPD is often present, and colour vision lost proportionally to visual acuity. Optic disc swelling with haemorrhages are often present acutely. Visual field defects may be altitudinal (respecting horizontal meridian).
Is to exclude temporal arteritis by performing ESR/CRP as clinically indicated, control modifiable vascular risk factors (BP, cholesterol, blood glucose, etc.), and exclude contributory hypotensive drugs. Steroids may provide some benefit, although evidence is not conclusive. Disc swelling typically lasts 6–12 weeks, followed by optic atrophy. There is a significant risk of fellow eye involvement.
Causes sudden severe loss of vision in patients with new blood vessel formation (neovascularization) that occurs most commonly in patients with proliferative diabetic retinopathy or following ischaemic central retinal vein occlusion. New vessels grow into the vitreous from the retina and bleed, causing recurrent vitreous haemorrhage. The red reflex is lost when attempting fundoscopy. Retinal detachment may coexist and B-scan US is important to exclude this.
Often involves waiting for the haemorrhage to clear before undertaking pan-retinal photocoagulation laser. A non-clearing vitreous haemorrhage (>3 months) may necessitate vitrectomy to restore a clear ocular media. Acutely, the most important step is to exclude a retinal detachment.
Bleeding or exudate from a choroidal neovascular membrane is the cause of acute visual loss in patients with wet (exudative) AMD which presents with acute central visual loss and distortion. The fovea is relatively avascular; however, haemorrhage in front of the macula (premacular haemorrhage) may occur due to bleeding from a retinal vessel during the Valsalva manoeuvre when central venous pressure (and retinal venous pressure) is acutely elevated.
Is with ‘flashing lights’ (vitreoretinal traction) and ‘floaters’ (vitreous haemorrhage), which often do not occur in the above-mentioned disorders. Visual field loss (often described as a dark curtain) may exist.
Reduced visual acuity suggests that the macula has detached (poorer prognosis: Fig. 25.13), although acuity is spared in macula-on detachment.
Fig. 25.13 Macula-off retinal detachment. Photo courtesy of Mr. Imran Yusuf.
Occurs in every healthy eye, typically between 40 and 60 years of age as the vitreous liquefies but may occur earlier in myopes (short-sighted patients). Posterior vitreous detachment does not cause significant visual loss but may create a retinal break in ~5% of patients; progressive recruitment of fluid in the subretinal space (via the break) causes retinal detachment. A localized break is treated with laser photocoagulation to prevent retinal detachment; therefore, all patients with flashes and floaters should undergo retinal examination.
Urgent (same or next day) vitrectomy in macula-on cases and within a week for macula-off cases. Other forms of retinal detachment include tractional retinal detachment in diabetic patients, or exudative retinal detachment due to inflammatory or malignant disorders of the choroid/retina.
May present exclusively with visual field loss (particularly posterior circulation strokes which may result in occipital infarction, affecting the primary visual cortex). Middle cerebral artery strokes (anterior circulation) will likely cause sensory/motor deficits. Confrontation visual fields are therefore mandatory in the assessment of patients with visual loss.
May present with transient visual loss (typically lasting <1 hour) and may be associated with systemic symptoms (motor deficits) depending on the affected cerebral artery. Management of TIAs may include neuroimaging (CT/MRI depending on timing of presentation), TIA referral for cardiovascular risk factor assessment, ECG/echocardiography, and carotid Dopplers. Remember that posterior circulation strokes stem from vertebrobasilar artery insufficiency so carotid Dopplers may therefore not identify the responsible pathology.
Commonly presents with visual aura produced secondary to CNS vasospasm resulting in 15–30 min of evolving, bilateral scotomas which typically enlarge before disappearing. Scintillations (zigzags), flashing lights, and other ‘positive’ visual symptoms may exist. In classical migraine, a headache follows secondary to sequential CNS vasodilatation. This is not invariable and acephalgic migraines describe those without headache. Differentiating migraine from TIA relies on a careful history.
Painful visual loss associated with a red eye (acute angle-closure glaucoma, microbial keratitis, iritis, etc.).
Is an important disease in that it is treatable, yet failure to do so can result in irreversible visual loss. Large vessel vasculitis of the short posterior ciliary arteries causes infarction of the optic nerve.
It affects patients aged >50 with symptoms including temporal headache, scalp tenderness, jaw claudication, systemic upset (weight loss, night sweats, etc.) Visual symptoms may be present: it can present as anterior ischaemic optic neuropathy (most common, with disc swelling and haemorrhages), central retinal artery occlusion, or rarely, isolated sixth nerve palsy. Management is urgent with high-dose systemic steroids. Raised inflammatory markers (ESR/CRP) are typical. Temporal artery biopsy is diagnostic to support long-term steroid use, although it is not 100% sensitive due to ‘skip lesions’. Temporal artery ultrasound may prevent the need for biopsy.
Occurs secondary to demyelination typically affecting young females, often unilaterally.
Include central scotoma, pain on eye movements, and signs include reduced visual acuity, RAPD, and reduced red saturations or colour vision.
Fundoscopy reveals disc swelling in ~20%, although 80% have demyelination behind the optic nerve head (retrobulbar neuritis) and therefore have a normal funduscopic appearance.
Gadolinium-enhanced MRI can demonstrate lesions separated in space and time and therefore can be diagnostic of MS (McDonald criteria, 2010) in the setting of an acute isolated demyelinating episode.
Disease-modifying drugs (alemtuzumab, natalizumab) may prevent disability if started early. Referral to neurology is therefore considered appropriate.
Cataract describes opacity of the crystalline lens. It is associated with 
age, but may form earlier in patients with diabetes, steroid use, associated syndromes (such as myotonic dystrophy), radiation, or patients with a history of skin disease. Baby checks must include an examination of red reflexes: loss of the red reflex suggests either congenital cataract or retinoblastoma, which if missed may result in blindness or death, respectively.
Include reduced vision and glare (particularly with posterior subcapsular cataract). Patients are often referred from optometrists through their GP.
Is required to confirm that cataract is the principal cause of visual loss (Fig. 25.14), particularly to check that the disc and macula are healthy.
Fig. 25.14 A significant cataract in the right eye of a patient. Photo courtesy of Mr. Martin Leyland.
Most patients undergo phacoemulsification surgery under local anaesthetic. Sedation/GA may be required in some cases (head tremor, poor patient cooperation). To select the appropriate intraocular lens (IOL) implant power, corneal measurements and axial length of the eye are taken to plan the refractive outcome.
Patients are typically seen at 2 weeks with measurement of visual acuity and refractive error. Only one eye operation is performed in most cases on a single day due to the risk of endophthalmitis (contaminated drugs/instruments would otherwise affect both eyes).
Glaucoma is a major cause of irreversible blindness worldwide. It describes a group of diseases whose endpoint is damage to the optic nerve with loss of retinal ganglion cells, progressive visual field constriction, and blindness. The central acuity is preserved until late and consequently, most forms of glaucoma are asymptomatic until significant field loss is present.
Includes a history (including family history of glaucoma), risk factors (trauma, steroid use, vasospasm such as migraine/Raynaud’s phenomenon), measurement of IOP, assessment of optic disc appearance, and automated visual field testing (perimetry), increasingly supplemented with optic nerve imaging studies (e.g. optical coherence tomography of optic disc).
Optic discs demonstrate progressive optic disc cupping in glaucoma (the cup—a depression in the centre of the optic disc—becomes deeper and wider; Fig. 25.15). The neuroretinal rim becomes progressively thinner with irreversible loss of retinal ganglion cells and consequent visual field loss. Patients with raised IOP but no visual field loss and normal appearing optic discs have ‘ocular hypertension’: they are at risk of glaucoma and require monitoring.
Fig. 25.15 Progressive cupping of the optic nerve in glaucoma. Photos courtesy of Mr. John Salmon.
Is the major modifiable risk factor in patients with glaucoma, and treatment is aimed to reduce the IOP to a level at which no further visual field loss occurs. Normal IOP is <21 mmHg (measured by tonometry), but target IOP may need to be kept lower in glaucoma as every mmHg drop in IOP confers a protective effect.
Topical drops are often used initially, but laser treatments (trabeculoplasty) and surgical procedures (trabeculectomy) to outflow of aqueous may be required if medical treatment is not adequate.
Top tip
Glaucoma clinics are an excellent setting for practising direct ophthalmoscopy. Examine optic discs through undilated pupils if possible; try to draw the optic disc (practise interpretation) and compare it with the ophthalmologist’s drawing.
AMD is the leading cause of blindness in the retired population. Central visual loss occurs, with preservation of the peripheral visual field, even in advanced AMD.
Describes the accumulation of drusen at the macula and atrophy of the retina (Fig. 25.16). Treatment is with high-dose vitamins (lutein/zeaxanthin) if drusen are large, and visual rehabilitation with magnifiers/lights to assist in reading and activities of daily living.
Is the result of leakage from the choroidal neovascular membrane that forms under the macula. Leakage of fluid (blood/exudate) results in distortion and loss of vision (Fig. 25.17). Amsler’s charts are provided to patients with dry AMD to identify new distortion that may herald the onset of wet AMD, and prompt timely referral for investigation/treatment.
Figs 25.16 and 25.17 Typical appearance of dry (left) and wet (right) AMD. Photos courtesy of Mr. Imran Yusuf.
Honours
Intravitreal injection of biologic drugs that inactivate VEGF are effective treatments in wet AMD, reducing leakage and stabilizing/improving vision. Drugs used include Lucentis® (ranibizumab), Eylea® (aflibercept), and rarely Avastin® (bevacizumab). The CATT and IVAN studies proved non-inferiority of Avastin® compared with Lucentis® with no statistically significant differences in serious adverse events. However, Lucentis® and Eylea® are licensed in AMD, and are often used. Eylea® requires less frequent dosing and may be cost-effective due to reduced hospital visits for each patient.
Is the most common cause of blindness in the working population. It is asymptomatic until advanced; annual screening for diabetic patients >12 years of age is provided by the NHS with screening photographs. Patients with visually threatening changes are referred to the eye clinic.
Is graded as background (dot/blot haemorrhages, exudates), pre-proliferative (cotton wool spots/venous changes), or proliferative diabetic retinopathy (new blood vessels on the retina, optic disc, or iris; see Fig. 25.18). New vessels result in vitreous haemorrhage, tractional retinal detachment, or rubeosis iridis (new vessels occlude the drainage angle causing raised IOP).
Fig. 25.18 Proliferative diabetic retinopathy with pre-retinal haemorrhages and neovascularization of the optic disc head. Photo courtesy of Mr. Imran Yusuf.
Multiple dot (small microaneurysms), and blot haemorrhages (large with indistinct edges). Blot haemorrhages are indicative of ischaemia if multiple and are a poorer prognostic sign (Fig. 25.19).
Fig. 25.19 Severe background diabetic retinopathy with multiple blot haemorrhages visible in a single quadrant. Photo courtesy of Mr. Imran Yusuf.
Neovascularization in diabetic retinopathy occurs due to retinal ischaemia secondary to microvascular disease. This is demonstrated in the fluorescein angiogram: dark regions represent ischaemia (capillary non-perfusion) with enhancing (hyperfluorescent) areas representing leakage from adjacent new, pathological blood vessels. New vessels may also proliferate at the optic disc with collections of pre-retinal blood visible (see Fig. 25.18).
Pan-retinal photocoagulation is required in these patients to reduce production of VEGF from the ischaemic retina which may result in regression of new vessels.
Characterized by haemorrhages or exudates at the macula (Fig. 25.20) causing chronic visual loss. Any pathology at the macula must be referred promptly as visual loss occurs early. Visual acuity is partly a function of macula integrity. Any pathology affecting the macula affects visual acuity early. Diabetic macular oedema typically affects type 2 diabetics, and results in chronic visual loss. Signs include exudates at the macula, and haemorrhages (Fig. 25.20). Microvascular non-perfusion (ischaemic maculopathy) may occur, demonstrated on the fluorescein angiogram with capillary non-perfusion (hypofluorescence) at the fovea. The patient in Fig. 25.20 can be expected to have reduced visual acuity.
Fig. 25.20 Macula exudates in diabetic maculopathy. Photo courtesy of Mr. Imran Yusuf.
Treatment of diabetic eye disease must address systemic risk factors (blood glucose, BP, cholesterol, smoking, weight). Management of proliferative diabetic retinopathy is pan-retinal photocoagulation laser which aims to reduce the oxygen demand from an ischaemic peripheral retina at the expense of visual field loss. Treatment is titrated (new blood vessels regress leaving fibrous tissue behind) to reduce loss of visual field which may threaten driving vision. Patients not responding despite laser coverage may require vitrectomy which removes existing VEGF by removing the vitreous in which it is contained although ongoing ischaemia may produce VEGF thereafter. Vitrectomy also removes the scaffold for new vessels. Patients with macula oedema may benefit from macula laser (avoiding the perifovea), or anti-VEGF agents/steroids if oedema is recalcitrant.
Honours
The Diabetes Control and Complications Trial (DCCT) was a landmark longitudinal study identifying that intensive glycaemic control (HbA1c <6%) in diabetic patients was associated with a huge reduction in risk of diabetic retinopathy, nephropathy, and neuropathy over the 6-year study period. BP should be limited to 130/80 mmHg in diabetic patients, and 125/75 mmHg if microalbuminuria coexists.
These are excellent for photo documentation of retinal or optic nerve pathology, for assessing response to treatment or identifying disease progression, or for medicolegal purposes such as documentation of retinal haemorrhages in abusive head trauma (non-accidental injury). Wide-field retinal imaging (with documentation of the retinal periphery) is now possible through an undilated pupil (Optomap®). Handheld retinal cameras are available for infants and supine/anaesthetized patients (RetCam®). In addition to optic nerve and retinal photographs, digital photography is used in oculoplastic surgery to document lid position, eyelid lesions, and evaluating the success of surgical intervention.
Optical coherence tomography provides rapid, non-invasive images using infra-red light to acquire cross-sectional images of the macula for assessment of wet AMD or macular oedema (in which fluid/exudate appears as focal cysts or subretinal fluid secondary to diabetic maculopathy, retinal vein occlusion, or following cataract surgery). Degenerative changes can be seen in dry AMD. It is now widely used in ophthalmology and an integral part of care in AMD.
B-scan US is useful to rule out retinal detachment in the presence of media opacity (dense cataract or vitreous haemorrhage), to measure the depth of choroidal naevi/melanomas, or to demonstrate fluid in posterior scleritis. Anterior segment US can delineate the configuration of the drainage angle.
Fluorescein angiography is useful in the diagnosis and management of retinal vascular disease such as AMD, proliferative diabetic retinopathy (to highlight new vessels and ischaemic retina amenable to laser), wet AMD, retinal vein or artery occlusion, or where diagnostic uncertainty exists. Fluorescein is injected intravenously, passing progressively through the retinal arterial tree, capillaries, and venous system. Shellfish allergy is a contraindication; anaphylaxis is rare otherwise.
We wish to thank Mr John F. Salmon, Consultant Ophthalmologist at the Oxford Eye Hospital for being the senior reader for this chapter and for providing some of the presented images; Mr Martin Leyland, Consultant Ophthalmologist at the Royal Berkshire Hospital, Reading, for kindly providing many anterior segment photographs; and medical students Daniel Fitzgerald and Stuart Faragher for their valued feedback.
During your ophthalmology placement, you may have the opportunity to attend an ophthalmic theatre list. There are >350,000 cataract operations performed in the UK annually and you should aim to observe two or three phacoemulsification and IOL procedures.
Phacoemulsification describes emulsification of the crystalline lens with US energy through a small incision through which the residual lens matter is aspirated. It is commonly performed with local anaesthetic (topical only (anaesthetic drops), under Tenon’s capsule (subTenon)), although sedation/GA is sometimes used.
Iodine is used to clean the periocular skin and sterilize the ocular surface, and a sterile drape is applied to remove the eyelashes from the surgical field. Typically, two or three small clear corneal incisions (bloodless) are used for bimanual manipulation within the eye (main corneal incision: Fig. 25.21a). A circular hole is fashioned in the lens capsule (capsulorrhexis: Fig. 25.21b) to allow access to the lens, which is dissected from the capsule with saline (hydrodissection). The phacoemulsification probe is introduced into the eye, and the nucleus is typically divided into four before aspirating each in turn (Fig. 25.21c). Soft lens matter is aspirated with smaller probes, before the capsular bag is filled with viscoelastic and the IOL is commonly injected through a small wound and placed within the capsular bag (Fig. 25.21d). Intracameral (into the anterior chamber) cefuroxime has reduced the incidence of postoperative endophthalmitis (bacterial infection of the eye) sevenfold. Wounds are hydrated rather than sutured in most cases. Patients are given topical steroids and antibiotics to prevent postoperative infection and inflammation.
Trivia
Charles Kelman (1930–2004) considered that US energy used by dentists to clean teeth could be used to emulsify a cataract and remove it through small wounds. Cataract had traditionally been removed whole which requires large wounds and a long rehabilitation period, and results in significant astigmatism. He pioneered modern phacoemulsification surgery, in which the lens is divided within the eye and emulsified using a probe manipulated in the eye through a small incision of ~2 mm. This has permitted more predictable refractive outcomes and cataract surgery to be performed as an outpatient procedure. Over 100 million individuals have benefitted from phacoemulsification cataract surgery worldwide to date.
Fig. 25.21 Intraoperative appearances during phacoemulsification cataract surgery. Photos courtesy of Mr. Imran Yusuf.
To ask the boss
An IOL is implanted following removal of the cataract to replace the focusing contribution of the lens to the eye. The lens power predicted to produce distance vision (emmetropia) is calculated by measuring the corneal curvature and axial length. Some patients may be kept myopic for unaided reading vision if they are used to this. More than 6000 IOLs have been designed, differing in material, shape, and where in the eye it may be safely implanted. The first IOL was made from PMMA, as it was observed that shattered PMMA plastic from airplane windshields did not excite an inflammatory reaction in the eyes of affected pilots. Most commonly, an IOL is implanted in the capsular bag once the cataract within it has been removed.
Trabeculectomy describes the surgical fashioning of a communication between the anterior chamber and the subconjunctival space to permit an accessory pathway for aqueous humour to drain from the eye. This is created superior to the cornea, under the upper eyelid. It commonly reduces IOP to 10–15 mmHg without the need for topical drops, and may last for decades. In young patients, scarring can close the surgical communication and the procedure may be augmented with mitomycin C to eliminate subconjunctival fibroblasts which mediate fibrosis.
A diamond knife is used to fashion a scleral flap once the conjunctiva is dissected. The anterior chamber is then entered; a punch is used to remove a small piece of sclera from the base of the flap. A peripheral iridectomy (seen as a triangular defect in the iris; Fig. 25.22) is performed to prevent the iris from occluding drainage before the scleral flap is sutured back and conjunctiva sutured to prevent leakage (and passage of infection into the eye). A drainage bleb of conjunctiva is formed under the upper eyelid where it is hidden (Fig. 25.22). Intensive topical steroids are used for 3 months postoperatively to reduce the likelihood of scar formation. There is a risk of high or low pressure in the immediate postoperative period which needs to be closely observed and managed appropriately.
Fig. 25.22 The appearance of the eye following trabeculectomy surgery demonstrating a peripheral iridectomy and shallow bleb superiorly. Photo courtesy of Mr. John Salmon.
Vitrectomy entails surgical removal of the vitreous gel in order to gain access to the retina to peel membranes (for treatment of macular hole and epiretinal membranes), remove traction (retinal detachment), and clear ocular media (non-clearing vitreous haemorrhage). A surgical lens is mounted onto the operating microscope to permit a direct view of the retina. Surgical ports (typically three) are created in the pars plana 3.5–4 mm behind the limbus (junction of cornea and sclera) to safely enter the eye without damaging the lens or retina. Irrigation is secured to one port to maintain the pressure of the eye. A light pipe is used in the second port, and the vitrector (a guillotine with a high cut rate) is used to remove the vitreous gel through the third port. Dyes may be used to visualize fine retinal membranes to facilitate their removal. Laser and cryotherapy may be used to secure retinal breaks. Heavy gases may be used to create an endotamponade, taking several weeks to absorb. Silicone oil creates a stable long-term tamponade but may cause raised IOP. Vitrectomy the risk of cataracts.