Ophthalmology - Gradual visual disturbance Flashcards
Outline some causes of gradual visual loss
Glaucoma Refractive error Cataracts Retinal degeneration Macular degeneration Compressive lesions (i.e. on the optic nerve)
How should refractive errors be investigated?
The pinhole test is more useful for identifying refractive errors. If there is a refractive error, the vision will improve when the pinhole is used. A patient with thick glasses should wear them for the pinhole test. Once other causes of visual loss have been excluded, the patient can be sent to the optometrist for refraction and correction of refractive error.
How can corneal disease cause gradual visual loss?
Various disorders can cause gradual loss of the corneal endothelial cells and increasing oedema in the cornea (for example, Fuch’s endothelial dystrophy). This leads to a gradual decrease in visual acuity that does NOT improve substantially with pinhole. If the damage is advanced the cornea may appear opaque. A corneal graft from a donor may be required.
What is a cataract? How can it be diagnosed and what other features should you look for?
This is probably the most common cause of gradual visual loss. It can be diagnosed through testing for the red reflex. The patient should be referred if the visual disturbance interferes with their lifestyle. If a patient with a cataract cannot project light or has an afferent pupillary defect, however, other diseases such as retinal detachment must be excluded.
How do patients with glaucoma present with gradual visual loss?
Unfortunately, the patient with primary open angle glaucoma may not complain of visual disturbance until late in the course of the disease. Hence, the need for screening. Primary open angle glaucoma should, however, be excluded in any patient with gradual visual loss. Establish whether there is a family history of glaucoma. The vision can be 6/6 so the visual field should be checked with a red pin. Also check for cupping of, or asymmetry between, the optic discs.
How does age related macular degeneration present?
This may occur gradually and is typified by loss of the central visual field. There are usually pigemented changes to the macula. The disease occurs in both eyes, but is asymmetrical, and it is more common in short sighted individuals. The gradual deterioration is not treatable, but if acute visual distortion develops this may indicate a leaking area under the retina (choroidal neovascularisation), which may respond to laser photocoaglation.
What is a macular hole?
A macular hole is a full thickness absence of neural tissue at the centre of the macula. Between 10% to 20% of full thickness macular holes (FTMH) will become bilateral. Patients usually present with painless loss of central vision or distortion of the central visual field, although early macular holes may be asymptomatic.
Patients with established FTMH can be treated with vitrectomy and instillation of intraocular gas (to provide retinal tamponade), which have a higher chance of closing the hole successfully.
What are the important clinical features of diabetic maculopathy?
Diabetic retinopathy occurs in both insulin dependent and non-insulin dependent diabetics and affects ALL age groups. The patient may or may not give a history of diabetes, although the longer the duration of diabetes the more likely the patient is to have retinopathy. Remember that although the patient may describe the onset of visual loss as gradual, sight threatening diabetic retinopathy may still be present.
Non proliferative diabetic retinopathy is typified by microaneurysms, dot haemorrhages, and hard yellow exudates with well defined edges. There may also be oedema of the macula, which is less easy to identify but can lead to a fall in visual acuity. Non proliferative diabetic retinopathy at the macula (diabetic maculopathy) is the major cause of blindness in type 2 diabetics, but it also occurs in younger type 1 patients. Some forms of diabetic maculopathy may be amenable to laser photocoagulation.
How is gradual visual disturbance managed?
The initial management of gradual visual loss depends on the cause. Refractive errors usually require no more than a pair of glasses. Cataracts can be removed an an artificial lens implanted. Glaucoma requires treatment to lower the IOP. In general, patients with unexplained visual loss should be referred.
What steps can be taken to maximise low vision?
Strong light from behind for reading Magnifying aids Large print books Closed circuit television Home aids - e.g. tactile markins for cookers
What is hereditary degeneration of the retina?
These conditions are relatively rare (for example, retinitis pigmentosa) but should be suspected if there is a family history of visual deterioration. Symptoms include night blindness and intolerance to light. Most types of retinal degeneration are not yet treatable, but some are associated with metabolic disorders that CAN be treated. These patients should be referred.
Patients with severe visual impairment may develop visual hallucinations and sleep disturbance. It is particularly important for these patients to have an opportunity to discuss their diagnosis and prognosis and to have genetic counselling.
“My vision has gradually become cloudy and dim, but there is no pain in my eye” - what differentials would you consider?
The main differentials are:
- cataracts
- age related macular degeneration (dry type)
- diabetic retinopathy
- primary open angle glaucoma
Gradual progressive loss of vision is a common complaint in the elderly. Although cataract is a common diagnosis, it is important to exclude coexisting conditions such as age related macular degeneration, diabetic retinopathy and glaucoma.
“My vision has gradually become cloudy and dim, but there is no pain in my eye” - what issues in the history support the diagnosis?
The gradual onset and progressive visual loss is typical of cataract and dry ARMD.
“My vision has gradually become cloudy and dim, but there is no pain in my eye” - what additional features in the history would you seek to support a particular diagnosis?
Is the deterioration in vision for distance, near or both? Cataracts affect BOTH near and distance vision, whereas ARMD and diabetic maculopathy may affect near vision to a greater extent than distance vision. Ask about a history of diabetes and hypertension. Does the patient smoke? Is there a family history of glaucoma?
“My vision has gradually become cloudy and dim, but there is no pain in my eye” - what clinical examination would you perform and why?
Measure the visual acuity. Examine the red reflex - this is reduced if there is nuclear sclerotic cataract. Intraocular pressure is measured. Ophthalmoscopy is performed looking for signs of ARMD and diabetic retinopathy, including retinal haemorrhages and hard exudates at the macula. Examine the optic disc closely. Note the colour, the contour of the disc margins and the cup:disc ratio. The cup:disc ratio is enlarged in primary open angle glaucoma.
“My vision has gradually become cloudy and dim, but there is no pain in my eye” - what investigations would be most helpful and why?
If diabetic maculopathy is detected, the patient may require fundus fluorscein angiography. Fluorescein angiography may also be helpful in excluding wet ARMD, which may coexist with the dry type. The blood pressure, blood sugar and lipid profile are measured. Visual fields analysis is performed if glaucoma is suspected.
Outline the treatment options for dry ARMD
Unfortunately, there is no effective treatment of dry ARMD. Although prophylactic laser treatment has been tried, there is little evidence that is has any benefit. The Age Related Eye Disease Study (AREDS) evaluated the effect of high doses of zinc and selected anti-oxidants (beta carotene and vitamins C and E) and found significant reduction in the risk of progression in patients with advanced ARMD (categories 3 and 4). Further studies have shown that omega 3 fatty acids did not affect the progression of advanced ARMD.
There may be benefits to substituting lutein/ zeaxanthin for beta carotene in the original AREDS formulation, especially for current or former smokers. Specific nutritional supplements are therefore indicated in advanced ARMD. The patient should also be advised to stop smoking. Arrangements for the provision of low visual aids and rehab should be made.
Outline the main treatment options for primary open angle glaucoma
Medical treatment: most cases can be managed with primary open-angle glaucoma is successfully treated with antiglaucoma eyedrops
Laser treatment: laser trabeculoplasty is sometimes used in the treatment of glaucoma (it is also performed in diabetic maculopathy, if there is clinically significant macular oedema)
Surgical treatment: glaucoma filtration surgery (trabeculectomy) or a glaucoma drainage device may become necessary if medical treatment is not tolerated or effective
“I have difficulty seeing at night” - what is the differential diagnosis?
Differential diagnosis includes:
- retinitis pigmentosa (RP)
- vitamin A deficiency
- primary open angle glaucoma
- cataracts
- degenerative myopia
- previous panretinal laser photocoagulation
“I have difficulty seeing at night” - what issues in the history support the diagnosis?
Night blindness (nyctalopia) is a feature of MANY diseases. Vitamin A is necessary for the conversion of light energy to an electrical signal in the rod outer segments. The rods function at low levels of illumination, so vitamin A deficiency results in night blindness. Difficulty with night vision may indicate an abnormality of rod function and is characteristic of retinitis pigmentosa. However, ANY cause of extensive peripheral retinal degeneration, including primary open angle glaucoma and degenerative myopia, results in peripheral visual field loss and poor night vision. Cataracts cause a general reduction in the amount of light entering the eye and can therefore produce similar symptoms.
“I have difficulty seeing at night” - what additional features in the history would you seek to support a particular diagnosis?
It is important to determine the onset of symptoms. Patients with RP often begin having difficulty with night vision in teenage years (e.g. they may report having had difficulty finding their way around a cinema or other dark environment). Does the patient have a hearing deficit? Usher’s syndrome is a variation of RP that also impair’s hearing. Ask about symptoms that may suggest constriction of the peripheral visual field, such as involvement in RTAs. Is the patient myopic? Does the patient wear spectacles or contact lenses? The incidence of myopia is increased in RP. Ask about a family history of RP, night blindness, glaucoma and cataracts. Enquire about any history of abdominal surgery involving small bowel resection and liver disease, which may cause malabsorption and hypovitaminosis.
“I have difficulty seeing at night” - what clinical examination would you perform and why?
Measure visual acuity and assess visual fields to confrontation. Examine the red reflex, which may be reduced in eyes with cataract. Posterior subcapsular cataract often occurs in patients with RP. Check the intra-ocular pressure. Dilated fundoscopy may show the classic appearance of RP with pigment proliferation and accumulation of pigment shaped as bone corpuscles (“bone spicules”) in the midperipheral retina. There may be diffuse large areas of chorioretinal atrophy in degenerative myopia. Examine the optic disc carefully for optic atrophy and/or pathological optic disc cupping (enlarged cup: disc ratio). Look for retinal arteriolar attenuation and cystoid macular oedema seen as a dull or absent foveal light reflex, because this may occur in patients with RP.
“I have difficulty seeing at night” - what investigations would be most helpful and why?
In patients with RP or advanced glaucoma, visual field testing shows marked constriction of the peripheral field (tunnel vision). In RP, the electroretinogram is the most useful diagnostic test. It is reduced in amplitude or non-recordable and helps confirm the diagnosis. Cataracts are uncommon at such a young age and, if present, fasting blood sugar should be requested to exclude diabetes.
Outline the treatment options available for RP
In patients with RP, the eyes should be examined annually to determine the progression of the disease and to monitor for the development of cataract and glaucoma. Genetic counselling is mandatory. A complete family history and ophthalmological assessment of all family members will help to classify the disease as X chromosome linked, autosomal dominant or autosomal recessive. Many patients with RP are legally blind in middle age.
What compressive lesions can affect the optic pathways?
These are relatively rare, but should always be considered. Clues in the history and examination include headaches, focal neurological signs, or endocrinological abnormalities such as acromegaly. There should NOT be an afferent pupillary defect in most patients with cataract, macular degeneration or refractive error. Therefore, if an afferent defect is seen, suspect a compressive or other lesion of the optic pathways. Testing of the visual fields may show a bitemporal field defect due to a pituitary tumour. The optic discs should be checked for optic atrophy and papilloedema.
What drugs can cause gradual visual disturbance?
Several drugs may cause gradual visual loss. In particular, a history of excessive alcohol intake or smoking; methanol ingestion; or taking chloroquine, hydroxychloroquine, isoniazid, thioridazone, isotretanoin, tetracycline, or ethambutol should lead to suspicion of drug induced visual deterioration. Systemic, inhaled or topical corticosteroids may cause cataracts and glaucoma.
How is a patient registered as blind?
Blind or partially sighted registration is not essential but it helps patients to access financial benefits and specialist support and advice from local authorities.
The person should be referred to a consultant ophthalmologist who, with the patient’s agreement, completes form BD8. The requirements for registration are:
1) Partially sighted - the patient must have vision of 6/60 or worse in both eyes. The vision can be better than 6/60 if the visual fields are markedly reduced, for example, a patient with 6/6 vision but severely restricted fields caused by POAG
2) Blind - the current statutory definition of blindness is “that a person should be so blind as to be unable to perform any work for which eyesight is essential”. However, many registered blind people continue in their employment with appropriate resources. The guidelines for registration as blind are a visual acuity of 3/60 or worse in both eyes
What is ARMD?
Age related macular degeneration is the late stage of age related maculopathy and is the most common cause of blindess in developing countries. The condition is characterised by progressive, bilateral atrophic changes in the choriocapillaris, Bruch’s membrane and the retinal pigment epithelium. The incidence of blinding ARMD increases sharply with age, and is present in about 15% of people aged over 85. ARMD can be divided clinically into dry (atrophic) and wet (exudative) forms.
