retinal detachment

Retinal detachmentRetinal detachmentA Self Directed Learning package for medical students.

•Introduction•Learning outcomes

•Epidemiology•Anatomy of the eye

•Anatomy of the retina

•Pathogenesis- Rhegmatogenous-Tractional- Exudative•Quiz•Symptoms•Signs and investigations

•Treatment-External- Internal•Prognosis•Quiz•References•Glossary

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Introduction Although relatively rare, retinal detachment is an important

eye condition which leads to blindness if untreated. This self directed E-learning package will help you in your

understanding and identification of the condition, and introduce you to some of the treatment options available.

To use this package, open the PowerPoint presentation as a slide show and click to move on to the next slide. Clicking on the contents bar to the left of the page will allow

you to jump directly to that slide Clicking on blue underlined words will take you to a glossary

for more information Answering the questions (by clicking on the options provided)

will help to consolidate what you have learnt






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Learning outcomesAt the end of this SDL you should:

Be able to describe the epidemiology of retinal detachment, including the risk factors

Understand the pathophysiology of retinal detachment, and be able to describe the three main types

Be able to describe the symptoms associated with retinal detachment, and the investigations used in diagnosis

Be aware of the treatment options and the associated prognosis






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Epidemiology Rare

1 in 10,000 per year Lifetime risk of 1 in 300

Incidence increases with age with a peak at 50-60 years An increased risk is seen in:

Severe myopia (> 6 diopters) Lifetime risk increases to 1 in 20, and tends to affect younger patients Approximately 50% of retinal detachments occur in myopic individuals.

Following cataract surgery Overall risk increases to around 1% but depends on a variety of patient

characteristics such as previous myopia or eye trauma Trauma Family history Retinal pathology such as lattice degeneration Vitreous humour pathology such as posterior vitreous detachment

There is a 10-15% risk of developing a retinal detachment after a posterior retinal detachment

Previous retinal detachment There is a 15% chance of developing a detachment in the other eye.






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Anatomy of the eye

Light passes through the cornea and aqueous humour and enters the pupil aperture where it is focused by the lens onto the most sensitive part of the retina – the fovea.

Ora serrata

Copyright free image obtained from http://commons.wikimedia.org/wiki/File:Schematic_diagram_of_the_human_eye_en.svg






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Anatomy of the retina The retina is responsible for

converting focused light images into nerve impulses for conduction to the occipital lobes of the brain.

It consists of two parts, separated by the subretinal space:

1. Neurosensory retina – a thin, transparent layer of connecting neural cells transmitting impulses to the optic nerve:

Photoreceptors Bipolar cells Ganglion cells

2. Retinal pigment epithelium (RPE) – a single layer of pigmented cells which maintain photoreceptor physiology by synthesising and storing metabolites and vitamins.






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Pathogensis

ScleraChoroid

RPENeurosensory retina

Subretinal space

A retinal detachment (RD) is a separation of these two retinal layers. There are three types:

1.Rhegmatogenous

2.Exudative

3.Tractional






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Rhegmatogenous RD This is the most common form of retinal detachment. A tear or hole in the neurosensory retina (called a

retinal break) allows vitreous fluid to enter the subretinal space.

It is often preceded by a posterior vitreous detachment (PVD), whereby the gel-like vitreous humour liquefies with age and contracts, peeling away from the retina to cause a break. This condition is commoner is severe myopes (due to the elongated shape of the globe) and following eye trauma.

An underlying weakness of the retina (such as lattice degeneration) also increases the likelihood of a break forming.






9Sclera

ChoroidRPENeurosensory retina

Subretinal space Vitreous humour

Tractional RD This is distinguished from rhegmatogenous retinal detachment by

the fact that the retina does not break. Instead, traction produced by contractile membranes on the

surface of the neurosensory retina causes the retina to be pulled apart.

This is often associated with proliferative diabetic retinopathy, as the abnormal blood vessel growth across the surface of the retina can act as a traction point.

Fibrous tissue deposited after trauma can also be responsible. The traction can eventually result in a retinal tear, giving rise to a

combined rheumatogneous and tractional retinal detachment.






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Exudative RD This type, also known as serous retinal detachment,

results from an excess of fluid in the subretinal space, and does not involve a retinal break.

It is the least common form of retinal detachment The fluid can be due to:

Abnormal choroidal circulation, e.g. due to intraocular tumours such as malignant melanoma of the choroid

Inflammatory processes such as scleritis or posterior uveitis , although this is rare.

Central serous retinopathy

Choroid

RPE

Neurosensory retina

Sclera

Vitreous humourSubretinal space






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Quiz

1. The 2 layers of the retina are called the neural layer and the choroid

2. Retinal detachment caused by a tear in the neural retina is called rhegmatogenous.

3. Exudative retinal detachment is associated with diabetic retinopathy

4. Posterior vitreous detachment can occur as part of the normal ageing process

T F

T F

T F

T F

Answer the following true or false questions:






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SymptomsEasy to remember as the 4 Fs:1. Flashing lights (Photopsia) – caused by traction on the retina and usually seen in

the periphery.

2. Floaters – caused by condensations in the vitreous humour causing shadows to be cast onto the retina. Theseare described by patients as spots or strands moving with eye movements. They can also occur due to small bleeds into the vitreous humour during a retinal tear. As floaters are common in myopic patients, it is a sudden onset or an increased number which are important.

3. Visual Field defect – often manifesting as a dark shadow or curtain coming across the eye from the periphery.

4. Falling acuity - Loss of central vision or visual blurring occurs when the detachment directly involves the fovea, or if the usual light pathway is obscured by a detachment elsewhere.

PVD can present with photopsia and floaters, but field loss is an indication of a retinal tear. However, as PVD can develop into retinal detachment, any of the above

symptoms merit further investigation.

Artist impression of floaters against a blue

sky *

* Copyright free image from http://www.cynical-c.com/archives/bloggraphics/Floaters.png






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Clinical examination of the symptoms, i.e. confirmed visual field loss and falling acuity

Relative afferent pupillary defect – in severe rheumatogenous retinal detachment

Intraocular pressure (measured using a tonometer) may be decreased

On dilated fundoscopy: Loss of red reflex – the area of retina

detached determined the degree of loss. Grey retina which “balloons” forwards if there

is marked fluid accumulation in the subretinalspace. This detached portion will move in an undulating as the eye moves, and may have corrugated folds.

Retinal tears appear reddish/pink due to underlyingchoroidal blood vessels.

Signs and investigations

* Image obtained, with permission, from stlukeseye.com

*






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Further tests to confirm the diagnosis include: Using a slit lamp (which uses high-power lenses) to

obtain a more detailed view of the retina. The Goldmann triple mirror test, which uses a slit lamp

and a contact lens surrounded by three mirrors on an anaesthetised cornea to examine the peripheral retina.

Ultrasonography of the eye showing the detached retina as a highly reflective signal.

CT or MRI if a tumour or foreign body is suspected.

Signs and investigations (continued)

Slit lamp*

*Image obtained copyright free from: www.gettyimages.co.uk






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Surgery is the only treatment and patients should be referred to an ophthalmologist immediately.

There are four main aims of surgery:

1. Relief of vitreo-retinal traction2. Closure of retinal break (if present)3. Drainage of subretinal fluid4. Reattachment of neurosensory retina to RPE

There are two main surgical approaches which meet these aims: external and internal.

Treatment






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1. Relief of vitreo-retinal traction Using a scleral buckle - a silicone

sponge which pushes on the retinafrom the outside. This creates an inward indentation which decreases traction, and also helps to close anyretinal tears present.

2. Closure of retinal break The break is further secured using cryotherapy or lasers. This technique can also be used

for the prophylactic closure of retinal breaks which have not yet led to a detachment.

3. Drainage of subretinal fluid Using a needle through the sclera and choroid (sclerostomy)

4. Reattachment of neurosensory retina to RPE The scleral buckle helps to hold them in place, while the cryotherapy or laser treatments

create local inflammation which strengthens the attachment.

External approach

Retinal break

Silicone sponge

Sutures

This approach is more commonly used in this country and all procedures are done without entering the globe of the eye.






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Internal approach 1. Relief of vitreo-retinal traction

By vitrectomy – some or all of the vitreous is removed using instruments inserted into the vitreous cavity through the pars plana

2. Closure of retinal break Inert gas or silicone oil is injected to form a

bubble which pushes against the tear from the inside (Pneumatic retinopexy). Any subretinal fluid will be resorbed, and the bubble itself is gradually absorbed over months. To ensure that the bubble stays in the correct position, the patient may have to maintain a specific head posture for a few days, and thissurgery is only practical for breaks in the superior retina.

This method is used in conjunction with laser or cryotherapy to aid break closure.

3. Drainage of subretinal fluid Fluid can be drained from inside, through the retinal break itself.

4. Reattachment of neurosensory retina to RPE The tamponade helps to hold them in place, while the cryotherapy or laser

treatments create local inflammation which strengthens the attachment.

This approach (also called vitreoretinal surgery) is sometimes used for larger retinal tears and instruments are inserted into the globe itself.

Retinal break

Oil or gas bubble






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Prognosis The amount of recovery depends on the

degree and duration of detachment, and whether or not the fovea was involved initially

Prompt surgery is usually successful at restoring vision, although detachments involving the fovea may have residual visual acuity loss

Complications of surgery include the formation of fibrotic areas in the vitreous which can cause retinal traction (proliferative vitreoretinopathy) and lead to further detachment.






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Quiz – read the following clinical case and answer the true or false question which follow

On examination you expect to find:

5. Loss of red reflex

6. Increased intraocular pressure

7. A ballooning retina with undulating folds

Clinical case: A 67 yr old man who has recently recovered from a cataract operation presents to A & E with a 2 day history of floaters and flashing lights and now reports a “dark curtain” obscuring his vision.

T F

T F

T F






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Quiz

8. Removal of the vitreous is carried out at the junction of the photosensitive and non-photosensitive retina.

9. Vitreoretinal surgery involves the use of a silicone sponge.

10. The prognosis for this man’s vision after the operation is good.

After slit lamp examination, the man is diagnosed as having a large rhegmatogenous retinal detachment and undergoes emergency vitreoretinal surgery.

T F

T F

T F






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References and further reading Batterbury, M., Bowling, B. Ophthalmology – an illustrated colour text. London: Churchill

Livingston, 1999

James, B., Chew, C., Bron,. Lecture notes: Ophthalmology. Oxford: Blackwell Publishing, 2007 (10th edition)

Friedman, N. J., Kaiser, P.K. Essentials of ophthalmogy. Saunders Elsevier, 2007

Galloway, N. R., Amoaku, W. M. K., Galloway, P. H., Browning A. C. Common eye diseases and their management. London: Springer, 2006 (3rd edition)

Ivanisević, M., Bojić, L., Eterović, D. Epidemiological study of nontraumatic phakic rhegmatogenous retinal detachment. Ophthalmic Res. 2000; 32:5, 237–9.

Tuft, S.J.,Minassian, D., Sullivan, P. Risk Factors for RetinalDetachment after Cataract Surgery: A Case–Control Study. Ophthalmology 2006; 113:4, 650-656.

All images are either drawn by the author or obtained from copyright free sources and referenced on the slides.






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Glossary Central serous retinopathy – an idiopathic condition in which small breaks in the RPE allow

choroidal fluid to leak into the subretinal space. It is usually unilateral and self-limiting ,and tends to affect young males.

Choroid – layer of blood vessels, connective tissue and pigment cells between the retina and the sclera, providing oxygen and nutrients to the retina.

Lattice degeneration – condition of unknown aetiology whereby the peripheral retina becomes atrophic. It is an important cause of retinal detachment (present in 40% of cases), especially in young myopic patients. The condition is also seen in patients with Marfan and Ehlers Danlos syndromes.

Myopia – Also known as short sightedness. Distant images are brought to a focus in front of the retina instead of on it. This is often due to an elongated eye, and affected patients are unable to see distant objects clearly.

Pars plana – The area at the posterior part of the cilliary body, at the junction where the transition from non-photosensitive retina to photosensitive retina occurs (known as the ora serrata)

Posterior uveitis – inflammation of the choroid often associated with systemic diseases such as connective tissue diseases as well as infectious disease such as syphilis.

Retinal break – a full thickness fissure in the neurosensory retina which can either be a tear (caused by vitreous traction ) or a hole (caused by chronic atrophy of the retina).

Scleritis – inflammation of the sclera often associated with connective tissue diseases such as rheumatoid arthritis.

Vitreous humour – a viscous gel-like substance filling the posterior part of the eye between the lens and the retina. Its purpose is to provide support to the globe of the eye. With age, the vitreous humour becomes more liquid (syneresis) as the collagen network breaks down. This can lead to vitreous detachment.

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