Macular Disorders

The macula is the central region of the retina situated at the posterior pole of the eye, between the superior and inferior temporal arteries, 3mm lateral (temporal) to the optic disc. It is 5.5mm in diameter and contains within it the 1.5mm diameter fovea and within that, the foveola, a 0.35mm area that houses the highest concentration of cone photoreceptors in the retina (to the exclusion of rods) and is concerned with enabling maximal, central visual acuity. There are no vessels overlying the foveola which is entirely supplied by the underlying capillaries of the choroid.

Symptoms associated with macular dysfunction

• Impairment of central vision is the main symptom associated with macular disease. This may be characterised as something appearing to obstruct the central vision or a blurred patch (e.g. the words in the middle of a sentence).
• Metamorphopsia: this common symptom describes a distortion of images - notably of straight lines ('if you look at the window, do all the sides of the frame look nice and straight?')
• Distortion of image size may occasionally occur. They may appear bigger (macropsia) or smaller (micropsia). This may in turn give rise to diplopia as there is a discrepancy between the image perceived in the healthy and the diseased eye.

Assessment of macular function

• Visual acuity - the most important test is the assessment of visual acuity. Note the distant acuity using a Snellen chart, making sure that you have identified any past history of previous visual acuity problem (e.g. amblyopia) - 'is this about normal for you?'. If you have access to a near vision booklet, assess the near vision too. Ask the patient to hold the booklet at about 30cm (about an arm's length) and, using their usual reading glasses, read the short passages, one eye at a time.
• Amsler grid - there are several forms of Amsler grids but the most common one is a 10cm by 10cm grid printed on a plain white paper. It is evenly divided into 0.5cm by 0.5cm squares and has a small black dot at its centre. The steps to using it are:
  • Ask the patient to cover one eye and hold the grid about 30cm away from them, preferably resting on a surface so that they can draw on the paper.
  • 'What is at the centre of the paper?' - failure to see the dot suggests a central scotoma.
  • (If there is no central scotoma:) 'I want you to focus on the central dot and tell me whether you can see all four corners of the big box out of the corner of your eye'
  • 'Still focusing on the central dot, are any of the small boxes missing? Where? Can you shade out the area where they are missing?'
  • 'Finally, whilst still focusing on the central dot, do any of the lines appear distorted/wiggly? Where - can you draw over those lines that are not straight?'
  • Rest and then test the fellow eye.
  Abnormalities of any of the answers suggests macular pathology. Patients can use the grid at home and test themselves (remind them to do one eye at the time).

Examination of the macula

• Ophthalmoscopy - the macula is seen as a dark circular patch between the vascular arches, the fovea being about 1 disc diameter lateral to the disc itself. The foveola is usually seen as a bright pinpoint yellow reflex at the centre of the macula. The macula is right in front of your line of vision if you ask the patient to look directly at the light. However, this may be uncomfortable and it is best left until the end of the fundoscopic examination.
• Slit-lamp biomicroscopy - this will be carried out in the ophthalmology clinic; it provides a good view of the macula and the underlying retinal pigment epithelium.
• Fluorescein angiography - this involves the observation of the passage of fluorescein dye through the retinal and choroidal circulation. Fluorescein is injected peripherally and a few seconds later, a series of photographs are taken of the fundus through dilated pupils. Both eyes are photographed for comparison, the affected eye first. It enables the identification of abnormal blood vessels, loss of blood vessels, blockages and leaks. Most patients experience a temporary discolouration of the skin (yellow tinge) and urine (orange tinge) and some may experience nausea and vomiting. Uncommon but more serious adverse effects include allergy and anaphylaxis (and therefore these patients are asked to wait in clinic sometime after the angiography to monitor for this).
• Indocyanine green angiography - this is based on a similar principle to fluorescein angiography but enables a better visualisation of the choroidal circulation. It may be performed simultaneously with fluorescein angiography. Adverse effects are less common and include sneezing, pruritis, nausea and vomiting. Syncope, backache and local skin necrosis may less commonly occur. It is contraindicated in patients with an iodine allergy or who are pregnant.

A range of problems can affect the macula, the most common of which in this country is age-related macular degeneration which is covered in a separate article, as is macular oedema, another common problem. Outlined below is a summary of other problems affecting the macula.

Central serous chorioretinopathy (CSCR)

• Description³ - also known as central serous retinopathy (CSR), this condition is characterised by fluid leakage at the level of the retinal pigment epithelium (which lies just beneath the photoreceptors) in the macular area. It is usually idiopathic but may be associated with systemic hypertension, systemic and inhaled steroids and with pregnancy. There are also interesting psychological associations typically described: patients are more likely to have type A personalities, conversional neuroses and be using psychopharmacological medications. Stress or a disturbing psychological event precedes the onset of CSCR in about 90% of patients. However more recently, there has been some debate over these apparent psychological links.⁴
• Presentation² - the patient (typically aged between 20 and 45, and 8 times more likely to be male) complains of acute blurring of the vision which may range from a mild central disturbance to a severe drop (e.g. 6/60). Colours may appear washed out and there can be a central scotoma. It is usually unilateral. Metamorphopsia and image size distortion are also common. Examination reveals a decrease in visual acuity and very occasionally, an RAPD (although presence of this prompts the thought of optic neuritis). Examination of the fundus reveals a well demarcated, localised serous detachment of the neurosensory retina from the retinal pigment epithelium in the macular region.
• Management - usually, reassurance and conservative management. Some patients with non-resolving CSCR require laser treatment after 4-6months.
• Outcome¹ - this tends to be excellent with spontaneous and full recovery usually occurring between 1 and 6 months. Occasionally the course is prolonged (6-12 months) and rarely, it becomes chronic (>12 months). Only the latter is associated with permanent impairment of visual ability and in these patients, the history has often been atypical and there may be bilateral pathology.

Macular hole

• Description - this describes an absence of neural retinal tissue in the centre of the macula. The exact pathophysiology is unclear but it is thought to represent the end-point of the process whereby vitreous shrinkage causes traction on the fovea eventually resulting in hole formation. It has also been associated with systemic vascular disease, hormonal variations, cystic retinal degeneration, trauma, retinal detachment and anterior vitreoretinal traction.⁵ However, the majority of holes are idiopathic.³ It is staged according to whether it is impending (stage 1a), occult (stage 1b), established but partial thickness (stage 2), full thickness (stage 3) or enlargened where there are secondary changes that have occurred around the original hole (stage 4).¹
• Presentation - this tends to occur in older (>55yo) women (~70% of patients).³ The complaint varies on the staging: an impending macular hole may be an incidental finding in an asymptomatic patient but full thickness holes characteristically present with a painless loss or distortion of central vision (usually to 6/60 or less). Sometimes, it is not noticed by the patient who compensates with the fellow eye and it is only picked up when pathology develops in the fellow eye. Diagnosis is confirmed on slit-lamp examination but occasionally, a fluorescein angiogram is required to confirm this.
• Management - this depends on the staging of the hole. Surgical closure of the hole is considered up until stage 3 associated with a visual acuity of 6/18 or worse and of less than a year in duration. It is associated with an improvement in 80% of eyes¹ but it requires considerable post-operative patient involvement (a technique known as posturing is used, whereby the patient has to maintain their head in a certain position for about 10 days for the gas bubble inserted at the time of surgery to stay in place). Referral to a low visual aid clinic may be more appropriate in a number of patients.
• Outcome⁵ - 50% of stage 1 holes will progress to stage 2 or worse and 70% of stage 2 holes progress to stage 3: surgery aims to prevent progression in the early stages but can only aim to try and preserve vision in the later stages. About 15% of fellow eyes will develop a macular hole over 5 years.¹

Myopic maculopathy

• Description - high myopia is associated with progressive elongation of the globe and associated degenerative changes in various structures including the macula. Some of these may be attributed to the stretching of the vitreous which the exerts chronic traction on the retina. This results in a variety of problems including myopic maculopathy. (Other problems include retinal detachment, cataract formation and an increased prevalence of primary open angle glaucoma).
• Presentation - patients usually present beyond 50yo with decreased vision. Examination reveals macular pigmentary abnormalities ± a macular hole. There may also be associated macular haemorrhage. A number of associated features include a crescenteric white patch of sclera around the disc, large patches of retinal pigment epithelium atrophy (characterised by areas of well-defined creamy-whiteness on the retina) and features of the other associated ocular problems outlined above.
• Management - optimal refractive correction helps with visual problems and laser treatment may be of benefit in some patients. Any associated ocular problems need to be addressed.
• Outcome - this is ultimately a progressive condition and when severe, the outcome is poor with a gradual decline in visual acuity.

Macular epiretinal membrane

• Description - this is the phenomenon where neural support cells grow over the macula to form a membrane (epiretinal gliosis). This may be idiopathic or occur secondary to retinal surgical procedures, retinal vascular disease, intraocular inflammation or trauma. The membrane may be thin (cellophane maculopathy) or thickened and contracted (macular pucker).
• Presentation - these middle-aged to elderly patients may be asymptomatic or present with a decrease in visual acuity (mild in cellophane maculopathy e.g. 6/9, more in macular pucker e.g. 6/12 or worse). Examination reveals a glistening membrane over the macula ± retinal wrinkles radiating out from the macula.
• Management - cellophane maculopathy does not need treatment but macular pucker may benefit from surgery involving peeling off the membrane. Any underlying problem will also be addressed.
• Outcome - visual acuity may not necessarily be improved but any image distortion may be helped by surgery.

Choroidal folds

• Description - these arise as a consequence of choroidal congestion, scleral folding or contraction of one of the neuroretinal membranes. The condition is usually idiopathic but can also arise due to orbital disease (e.g. thyroid eye disease), choroidal tumours (e.g. melanomas), ocular hypotony (e.g. following certain kinds of surgery) and a number of other reasons.
• Presentation - patients will predominantly complain of metamorphopsia but depending on the underlying cause and the extent of the folds, they may also complain of a decreased visual acuity. Parallel grooves (like wrinkled cling film) can be seen stretching across the retina.
• Management - this depends on the underlying cause.
• Outcome - this depends on the underlying cause.

Best disease (vitelliform macular dystrophy)

• Description - this belongs to a group of hereditary fundus dystrophies known as the 'inherited pattern dystrophies'. This rare condition is inherited in an autosomal dominant pattern.
• Presentation - asymptomatic or decreased vision - it may not be detected until later on in life when there is another reason to carry out a fundal examination. It is characterised by well-defined, round yellow lesions which are often compared to an egg yolk. It is a bilateral condition.
• Management - there is no effective treatment but laser is sometimes used to address complications such as neovascular membrane formation.
• Outcome - this depends on the type but ranges from excellent (adult vitelliform macular dystrophy) to poor (juvenile Best disease: there is progressive macular scarring from the fifth decade of life which can eventually lead to legal blindness).

Idiopathic polypoidal choroidal vasculopathy

• Description - this condition is characterised by an abnormality of the choroidal vessels which predisposes them to bleeding (giving rise to the term posterior uveal bleeding syndrome), particularly around the macular region.
• Presentation - the patient (more often non-caucasian) presents with sudden, painless, unilateral visual impairment. Retinal pigment epithelial or full thickness retinal detachments may be observed on examination ± vitreous haemorrhage.
• Management - some patients benefit from laser treatment.
• Outcome - this is usually good with spontaneous resolution of the haemorrhage.

Maculopathy in optic disc pit

• Description - an optic disc pit is a rare congenital abnormality associated with a visual field defect. Occasionally, the macula becomes involved in this condition: it accumulates subretinal fluid (possibly from the subarachnoid space, possibly from the vitreous) and this may eventually be associated with a retinal pigment epithelial detachment.
• Presentation - these patients present at puberty with a progressive, painless visual impairment. The optic disc pit itself may be asymptomatic and so this may be the first time this diagnosis is made.
• Management - some patients are observed at three-monthly intervals, others benefit from laser treatment. Occasionally, surgery (removal of the vitreous or gas injection) may be advocated.
• Outcome - this depends on the degree of macular involvement and need for treatment.

Solar maculopathy

• Description - solar radiation can cause photochemical effects in the retina as a result of looking directly or indirectly in the sun.
• Presentation - this is 1-4 hours after exposure; the patient complains of impairment of central vision ± metamorphopsia ± a central scotoma. Examination reveals a variously impaired visual acuity and there may be small unilateral or bilateral yellow spots around the macula. About 2 weeks later, these are surrounded by mottling.
• Management - observation.
• Outcome - the outcome is usually good with recovery to normal or near-normal visual acuity within 6 months. Mild symptoms may persist.

Angioid streaks

• Description - these arise as a result of degenerative structural abnormalities in the layers of the neuroretina and manifest themselves as crack-like dehiscences associated with calcium deposition.
• Presentation - initially asymptomatic or slight decrease in vision but over time, this becomes quite marked. There will be linear brown lesions on fundoscopy which intercommunicate in a ring-like fashion and eventually, the optic nerve will be affected too. This condition is associated with pseudoxanthoma elasticum, Ehlers-Danlos syndrome, rarely with Paget's disease and some haemoglobinopathies.
• Management - some patients may benefit from laser treatment.
• Outcome - ultimately, this is poor as the streaks creep over the fovea, cause exudative leaks in the macula and associated haemorrhage.

Cancer-related maculopathy

• Description - this rare condition tends to occur in patients with small cell lung carcinoma and occasionally other epithelial tumours. It may be the first manifestation of these tumours. It is characterised by an autoimmune photoreceptor destruction but there are no ocular metastases.
• Presentation - gradual onset of dimming of the vision and associated shimmering photopsia (flashes of light). There may be bizarre visual images seen and night blindness. The symptoms are bilateral (but may be asymmetrical) and progressive with little to see on fundus examination.
• Management - there may be a response to systemic steroids.
• Outcome - the prognosis is poor, both visually and systemically.

Drug-induced maculopathies

A number of maculopathies can manifest themselves as a result of systemic drug intake. The optimal management for these conditions is discontinuation of the medication where possible and observation in the ophthalmology outpatient clinic. Many resolve in time.

• Phenothiazines - drugs used in the treatment of schizophrenia can cause pigmentary changes affecting the macula, characterised by brown clumping of pigment ± loss off retinal pigment epithelium. Patients on these medications may be asymptomatic or present with blurred vision, browning of the vision or difficulty in seeing at night.
• Antimalarials - chloroquine and hydroxychloroquine both have the potential for retinotoxicity and may also result in corneal deposits. The retinopathy is related to the total cumulative dose and is more marked with chloroquine. Patients present with decreased vision (which may be severe in end-stage chloroquine maculopathy - less than 6/60 - and characterised by a 'bull's eye' macular lesion: a well defined red centre surrounded by a mottled yellow periphery), abnormal colour vision and difficulty in adjusting to darkness. It is useful to check the visual acuity before administering these drugs, prescribing hydroxychloroquine rather than chloroquine where possible and advising the patient to present early should they experience any visual symptoms. It is also helpful to give them an Amsler grid to use once a week. Routine ophthalmological screening is not currently the established practice.
• Toxic crystalline maculopathy - tamoxifen, canthaxanthin and methoxyflurane occasionally cause toxic retinopathy when taken in higher doses. They tend to manifest themselves as a decrease in visual acuity and are seen as tiny, glistening deposits arranged in a ring around the macula.

Valsalva maculopathy

• Description - intraocular bleeding can occasionally occur as a result of a sudden, severe increase in intrathoracic or intra-abdominal pressure.
• Presentation - the patient may complain of sudden distortion of central vision in one or both eyes and fundoscopy reveals a small, isolated macular haemorrhage in one or both eyes.
• Management - conservative
• Outcome - excellent