Retinal Diseases Part I:Retina and choroid

Done by:Mohammad Jaber

Zaid Al-Ghananeem

Mohammad Jomaa& Marah Saeed

Reviewed and Modified Dr. Mohammad Abusamak FRCS

•The retina itself is composed of two cellular layers: • Pigmented layer – the outer layer of the retina. It is

attached to the choroid layer and acts to support the neural layer. It continues around the whole inner surface of the eye.

• Neural layer – the innermost layer of the retina. It consists of photoreceptors; the light detecting cells of the retina (( rods and cones))

• •-Cones are responsible for daylight and colour vision • •-Rods are responsible for night vision.

Cones

• Structures in macula are specialized for high-acuity vision. Within macula are fovea and foveola that both contain a high density of cones, which are nerve cells that are photoreceptors with high acuity.

• The eye contains 3 types of cones, with different ranges of spectral sensitivity.

• The brain combines signals from neighboring cones to distinguish different colors.

• One type of rod, but rods are more sensitive than cones, so in dim light active, and without information provided by the separate spectral sensitivity of the cones it is impossible to discriminate colors. In the fovea centralis, cones predominate, and are present at high density.

Macula

• The macula in the human eye is the place where light is focused by the structures in the front of the eye (cornea & lens). It takes the picture that is sent to brain, where vision is completed.

• The macula provides us with ability to read and see in detail whereas rest of the retina provides peripheral vision.

* Lacks blood vessels. * Contains the fovea centralis: *Only has cones *Point of sharpest vision (100% visual acuity).

Symptoms of retinal disease

• Macular dysfunction • Blurred central vision. • Distorted vision ( metamorphopsia ) • A reduction ( micropsia ) or enlargement ( macropsia )

of object size may also occur if the photoreceptors become stretched apart or compressed together.

• areas of loss of the central visual field ( scotomata ) if part of the photoreceptor layer becomes covered, e.g. by blood, or if the photoreceptors are destroyed.

Peripheral retinal dysfunction (symptoms of macular dysfunction) :•Loss of visual field

•The field loss may be absolute, for example in a branch retinal artery occlusion, or relative (i.e. brighter or larger objects are visible) as in a retinal detachment. •Small areas of damage, e.g. small haemorrhages, do not produce clinically detectable defects. •Some diseases affecting the retina may predominantly affect one type of photoreceptor; in retinitis pigmentosathe rods are principally affected so that night vision is reduced (night blindness).

Retinal diseases Degenerative (non-vascular) • Central serous retinopathy. • Age-related macular

degeneration • Retinal detachment.

Vascular• Diabetic Retinopathy • Arterial occlusion • Venous occlusion • Hypertensive Retinopathy

Mechanism of Micropsia & Macropsia

• A reduction ( micropsia ) or enlargement ( macropsia ) of object size may also occur if photoreceptors become stretched apart or compressed together.

Peripheral retinal dysfunction

• The field loss may be absolute, for example in a branch retinal artery occlusion

Peripheral retinal dysfunction • The field loss may be relative, for example in a retinal detachment

VF defect in Retinitis Pigmentosa

• Some diseases affecting the retina may predominantly affect one type of photoreceptor; in retinitis pigmentosa the rods are principally affected so that night vision is reduced (night blindness).

Acquired macular disease

• Acquired disease of macula may destroy part or all of thickness of retina (e.g. age -related macular degeneration or a macular hole).

• In a number of conditions this damage is dramatically magnified by growth of new vessels from choroid through Bruch’s membrane and the retinal pigment epithelium (RPE), causing hemorrhage or exudation of fluid into the subretinal space and subsequent scarring of the retina.

• The neuroretina ceases to function if it is detached from the RPE, so these changescause marked disruption of macular function even before direct retinal damage occurs.

• Fluid may also accumulate within layers of retina at the macula (cystoid macular oedema) if normal tight junctions of the retinal capillaries that form inner blood – retinal barrier break down.

• This may occur following intraocular surgery, such as cataract surgery.

• The retina and sub-retinal layers may become separated by diffusion of fluid from choriocapillaris through an abnormal region of retinal pigment epithelium.

• This represents a breakdown of the outer blood – retinal barrier between choroid and retina, is termed central serous retinopathy. It may occur unilaterally, as a potentially reversible disorder particularly in young men

Age-related macular

degeneration

• Age - related macular degeneration (AMD) is commonest cause of irreversible visual loss in developed world

Pathogenesis• RPE removes and processes the used discs of photoreceptor

outer segments. Over time, undigested lipid products, such as age pigment lipofuscin, accumulate in RPE and excess material is transferred to Bruch’s membrane, impairing its diffusional properties. Extracellular deposits form between the RPE and Bruch’s membrane which can be seen with ophthalmoscope as discrete, sub - retinal yellow lesions called drüsen.

Age - related macular degeneration

• Collections of drusen in the macula give rise to the condition termed age - related maculopathy or ARM where vision is normal.

• The neighboring RPE and photoreceptors may also show degenerative changes, producing

• the dry or non – exudative form of AMD. Vision is abnormal

Age - related macular degeneration

• In less common, exudative or ‘ wet ’ form, new vessels from choroid, stimulated by angiogenic factors such as vascular endothelial growth factor (VEGF), grow through Bruch’s membrane and RPE into sub - retinal space, where they form a sub - retinal neovascular membrane . Subsequent haemorrhage into sub - retinal space or even through retina into vitreous is associated with profound visual loss.

• SignsFoveal reflex is absent. Yellow, well drusen may be seen, areas of hypo- &-hyperpigmentation.

Exudative AMD sub-retinal, or pre-retinal, hemorrhages seen.The experienced observer may detect

elevation of the retina stereoscopically + fluid

Risk factors:

• Smoking• Artificial fats• Sunlight• A diet high in processed,

packaged foods and low in fresh vegetables

• Uncontrolled hypertension and high cholesterol

• Obesity:• Advanced age• A gene variant that regulates

inflammation• Family history

Investigation

Diagnosis is based on appearance of retina.In patients with a suspected exudative AMD and with vision that is not severely affected, a fluorescein angiogram is performed to delineate the position of the sub - retinal neovascular membrane .The position of membrane determines whether patient may benefit from laser treatment.

• Treatment• There is no treatment for non-

exudative AMD. Dry

• Treatment• Patients with visual loss in one eye and high-

risk features in fellow eye or bilateral high-risk features but normal vision (large or confluent drüsen or significant hypo - and hyperpigmentation) may benefit from high -dose antioxidant vitamins and zinc.

• Betacarotene is, however, avoided in smokers or those who have recently stopped smoking because of the increased risk of lung cancer.

• Smoking itself is associated with an increased risk of developing haemorrhagic, exudative AMD and patients should be encouraged to stop.

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Other degenerative conditions associated with formation of sub-retinal neovascular membranes

• Degenerative changes and sub-retinal neovascular membranes also occur at maculae of very myopicpatients and can cause loss of central vision, in young adulthood.

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Other degenerative

conditions associated with

formation of sub-retinal

neovascular membranes

• Sub-retinal neovascular membranes may grow through elongated cracks in Bruch’ s membrane called angioid streaks classically in rare recessive disorder pseudoxanthoma elasticum , and in systemic diseases Paget’s disease and sickle cell disease.

• Again there may be a profound reduction in central vision. Vision is also reduced if crack itself passes through fovea.

Central serous retinopathy• Localized accumulation of fluid between neuro-retina

and RPE separates two layers and disturbs photoreceptor layer.

• Results from localized breakdown in normal barrier function of RPE.

• Usually unilateral and typically affects young or middle-aged males.

• Patients complain of distortion and blurred vision and visual acuity may fall markedly.

Macular oedema• This extracellular accumulation of fluid within the retina is a further cause of

distorted and blurred vision .Ophthalmoscopy reveals a loss of the normal foveal reflex and with experience a rather cystic appearance to the fovea. If the diagnosis is in doubt a confirmatory optical coherence tomogram (OCT) scan or a fluorescein angiogram can be performed. The fluorescein leaks into the oedematous retina in a characteristic pattern.

• Macular oedema may be associated with numerous and diverse eye disorders, including:

intraocular surgery; uveitis; retinal vascular disease (e.g. diabetic retinopathy and retinal vein occlusion); retinitis pigmentosa.• Treatment can be difficult and is dependent on the associated eye disease.

Steroids in high doses are helpful in macular oedema caused by uveitis; acetazolamide may be helpful in treating patients with retinitis pigmentosaor following intraocular surgery.

• Prolonged macular oedema can cause the formation of a lamellar macular hole.

Toxic maculopathies• The accumulation of some drugs in the RPE can cause macular damage.

These include the antimalarials chloroquine and hydroxychloroquine, used quite widely in the treatment of rheumatoid arthritis and other connective – tissue disorders, which may cause a toxic maculopathy. Chloroquine is the more toxic. Patients on chloroquine require regular visual assessment for maculopathy (Figure 11.6 ). The maculopathy is initially only detected by accurate assessment of macular function. At this early stage, discontinuation of the drug reverses the maculopathy. Later, a pigmentary target lesion is seen ophthalmoscopically, associated with metamorphopsia and an appreciable and irreversible loss of central vision.

• Phenothiazines (thioridazine particularly) used in high doses for prolonged periods (to treat psychoses) may cause retinal damage.

• Tamoxifen, selective estrogen receptor modulator (SERM). ... women and men diagnosed with hormone-receptor-positive, early-stage breast cancer after surgery (or possibly chemotherapy and radiation) in high doses, may cause a maculopathy.

Vitreous floaters and posterior vitreous detachment

• With ageing, vitreous gel undergoes degenerative changes over the age of 60 (earlier in myopes), with liquefaction and the formation of fragments of condensed vitreous They cast shadows on the retina, giving rise to the common symptom of vitreous ‘ floaters ’. These take the form of spots or cobwebs which obscure vision only slightly and move when the eyes move, reflecting the fluid nature of the vitreous. Symptoms are most marked on bright days, when the small pupil throws a sharper image on the retina.

• Sometimes, in older patients or myopes, the vitreous gel collapses and separates from points of retinal attachment, a condition termed a posterior vitreous detachment. This gives rise to acute symptoms of:

• photopsia (flashing lights) – due to traction on the peripheral retina by the detaching vitreous;• a shower of floaters – representing condensations within the collapsed vitreous, or sometimes a vitreous haemorrhage caused when the detaching vitreous ruptures a small blood vessel during the formation of a retinal tear or hole.• For this reason presentation with recent symptoms of an acute vitreous

detachment is an indication for full assessment of the vitreous and peripheral retina with full pupil dilation.

Retinal detachment A retinal detachment is an ophthalmic emergency requiring urgent diagnosis and treatment PathogenesisThe potential space between the neuroretina and its pigment epithelium corresponds to the cavity of the embryonic optic vesicle. The two tissues are loosely attached in the mature eye and may become separated: • If a tear occurs in the retina, allowing liquefied vitreous to gain entry to the sub -retinal space. This causes a progressive, rhegmatogenous, retinal detachment which may be partial or total. • If it is pulled off by contracting fibrous tissue on the retinal surface, e.g. in theproliferative retinopathy of diabetes mellitus ( traction retinal detachment ). • When, rarely, fluid accumulates in the sub - retinal space as a result of an exudativeprocess, which may occur with retinal tumours or during toxaemia of pregnancy ( exudative retinal detachment ).

• Tears in the retina are most commonly associated with the onset of a posteriorvitreous detachment. As the gel separates from the retina the traction it exerts (vitreous traction ) becomes more localized and thus greater. Occasionally it may besufficient to tear the retina. An underlying peripheral weakness of the retina such aslattice degeneration increases the probability of a tear forming when the vitreouspulls on the retina. Highly myopic people have a significantly increased risk ofdeveloping retinal detachment.

Retinal detachment refers to the detachment of the inner layer of the retina(neurosensory retina) from the retinal pigment epithelium

• MOST COMMON CAUSE OF TRACTIONAL retinal detachment is .. Fibrosis in diabetic retinopathy

• Causes of exudative retinal detachment ..

• 1-toxemia

• 2-tumor

• 3-hypertensive retinopathy

Rhegmatogenous retinal detachment EpidemiologyAbout 1 in 10 000 of the normal population will suffer a rhegmatogenous retinal detachment. The risk is greater in patients who: • are high myopes;• have undergone cataract surgery, particularly if this was complicated

by vitreous loss;• have experienced a detached retina in the fellow eye;• have been subjected to recent severe eye trauma. SymptomsRetinal detachment may be preceded by symptoms of a posterior vitreous detachment, including floaters and flashing lights. With the onset of the retinal detachment itself the patient notices the progressive development of a field defect, often described as a ‘shadow ’ or ‘curtain’ . Progression may be rapid when a superior detachment is present. If the macula becomes detached there is a marked fall in visual acuity.

Clinical features: symptoms

*Floaters *Flash of light (photopsia)

Localized retinal detachment: scotoma (visual field defect) Depending on the location of the detachment, a rising wall/dark shadow may appear from the top to the bottom (descending curtain) or from the bottom to top. The visual field defects may begin in either the nasal or temporal visual field .

Extensive retinal detachment and/or macular involvement: Sudden, painless loss of vision in the affected eye Relative afferent pupillary defect

Degenerative diseases of the retina: 4. RETINAL DETACHMENT:

Signs

Detached retina is visible on ophthalmoscopy as a floating, diaphanous membrane which partly obscures choroidal vascular detail.

Accumulation of fluid in the sub-retinal space (a bullous retinal detachment) undulating movements of the retina will be observed as eye moves.

A tear in the retina appears reddish pink because of underlying choroidal vessels.

There may be associated debris in the vitreous comprising blood (vitreous hemorrhage) and pigment, or the free - floating lid (operculum) of a retinal hole.

SignsThe detached retina is visible on ophthalmoscopy as a floating, diaphanous membrane which partly obscures choroidal vascular detail. If there is a marked accumulation of fluid in the sub - retinal space (a bullous retinal detachment) undulating movements of the retina will be observed as the eye moves. A tear in the retina appears reddish pink because of the underlying choroidal vessels. There may be associated debris in the vitreous comprising blood (vitreous haemorrhage) and pigment, or the free - floating lid (operculum) of a retinal hole. Managementsurgical Prognosis• If the macula is attached and the surgery successfully reattaches the

peripheral retina, the outlook for vision is excellent.• If the macula is detached for more than 24 hours prior to surgery, the

previous visual acuity will probably not recover completely. Nonetheless asubstantial part of the vision may be restored over several months.

• If the retina is not successfully attached and the surgery is complicated,then fibrotic changes may occur in the vitreous ( proliferativevitreoretinopathy , PVR ), which may cause traction on the retina andfurther retinal detachment. A complex vitreoretinal procedure may permitvision to be retained, but the outlook for vision is much poorer.

Traction retinal detachment

The neuroretina is pulled away from the pigment epithelium by contracting fibrous tissue which has grown on the retinal surface. This may be seen in proliferative diabetic retinopathy or may occur as a result of proliferative vitreoretinopathy.

Vitreoretinal surgery, requiring excision of the contracting bands, is required to repair these detachments. In these cases it may be necessary to inject silicone oil into the vitreous cavity, temporarily, to hold the retina flat.

Type of retinal detachment

Rhegmatogenous retinal detachment

Non-rhegmatogenous retinal detachment

Tractional retinal detachment

Exudative retinal detachment

Mechanism •Most common type •Retinal tears → retinal fluid, which is formed by vitreous degeneration, seeps into the subretinal space → retinal detachment

•Formation of vitreoretinal bands → traction on the vitreoretinal band during eye movements or as a result of sudden decrease in intraocular pressure→ retinal detachment

•Subretinal fluid accumulation without retinal tears

•Tumor growth

Degenerative diseases of the retina: 4. RETINAL DETACHMENT:

Risk factors •Pathological myopia • •Previous intraocular surgery (e.g., cataract • surgery) •Posterior vitreous detachment •Trauma •Retinal • detachment of the other eye •Peripheral retinal • breaks •Lattice degeneration •Retinoschisis •CMV retinitis •Family history of retinal • detachment

•Proliferative diabetic retinopathy •Retinopathy of prematurity •Sickle cell • retinopathy

•Systemic diseases • Pre-

eclampsia • Hypertensio

n • Bleeding

disorders • Polyarteritis

nodosa •Ocular diseases

• Sudden decrease in intra-ocular pressure due to perforating injuries or intraocular surgery

•Retinoblastoma •Malignant melanoma • of

Type of retinal detachment

Rhegmatogenous retinal detachment

Non-rhegmatogenous retinal detachment

Tractional retinal detachment

Exudative retinal detachment

Degenerative diseases of the retina: 4. RETINAL DETACHMENT:

Inherited retinal and photoreceptor dystrophies

Retinitis pigmentosa

Retinitis pigmentosa is inherited disorder of photoreceptors has several genotypic and phenotypic varieties.

It may occur in isolation or in association with systemic diseases, such as Usher ’ s syndrome (recessive disorder characterized by deafness and retinitis pigmentosa), abetalipoproteinaemia and Laurence – Moon syndrome.

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بالليل النظر صعوبة شكوى اهم

in retinitis pigmentosa the rods are principally affected so that night vision is reduced (night.(blindness

• Pathogenesis

The disease affects both types of photoreceptors, but the rods are particularly affected. The inheritance may be:

o autosomal recessive (sporadic cases are often in this category);

o autosomal dominant;

o X- linked recessive.

Several forms of retinitis pigmentosa have been shown to be due to mutations in the gene for rhodopsin

• Epidemiology

The prevalence of this group of diseases is 1 in 4000.

• Symptoms

The age of onset, progression and prognosis are dependent on the mode of inheritance. In general the dominant form is of later onset and milder degree, while recessive and X - linked recessive forms may present in infancy or childhood. Patients notice poor night vision, visual fields become increasingly constricted and central vision may ultimately be lost.

• Signs

The three signs of typical retinitis pigmentosa are:

1. peripheral clumps of retinal pigmentation (termed ‘ bone spicule ’ pigmentation);

2. attenuation of the retinal arterioles;

3. disc pallor – optic atrophy.

Patients may also have cataracts at an early age and may develop macular oedema.

• Investigation

A careful family history will help to determine mode of inheritance.

The diagnosis can usually be made clinically. Electrophysiological tests are useful in diagnosis. The electroretinogram (ERG) response may be lost early in disease, where there may be few clinical signs.

• Management

Unfortunately, nothing can be done to prevent the progression of the disease.

• Prognosis

X - linked recessive and autosomal recessive disease produce the most severe visual symptoms. About 50% of all patients with retinitis pigmentosa will have an acuity of less than 6/60 by the time they reach 50.

Cone dystrophy less common than retinitis pigmentosa. It is autosomal dominant, but many cases are sporadic. Patients present in the first decade of life with poor vision. Examination reveals an abnormal, banded macular appearance which has been likened to a bull’s-eye target. No treatment is possible, but it is important to provide appropriate help, not only to maximize vision but also to help with educational problems. Genetic counselling should be offered.

• Albinism

These patients have defective melanin synthesis. There are two types:

1. Ocular albinism, where the lack of pigmentation is confined to the eye. This is X - linked and nearly all of the affected individuals are thus male.

2. Oculocutaneous albinism, a recessive disorder where the hair is white and the skin is pale; a few of these patients can manufacture some melanin. This is an autosomal recessive defect .

• Albinism

These patients have defective melanin synthesis. There are two types:

1. Ocular albinism, where the lack of pigmentation is confined to the eye. This is X - linked and nearly all of the affected individuals are thus male.

2. Oculocutaneous albinism, a recessive disorder where the hair is white and the skin is pale; a few of these patients can manufacture some melanin. This is an autosomal recessive defect .

Retinoblastoma

• Commonest malignant tumor of eye in childhood

• Frequency of 1 per 20 000 births.

• Inherited autosomal dominant condition, but most cases are sporadic.

History and symptoms • Present (age of 8 months if inherited and 25

months if sporadic) with:

• A white pupillary reflex (leucocoria) due light scatter from pale elevated tumour posterior pole of eye.

• Sometimes tumor is bilateral on presentation.

• A squint due to reduced vision.

• Occasionally, with advanced tumors, painful red eye.

Signs and Investigations

a whitish - pink mass protruding from the retina into the vitreous cavity. Dilated

fundoscopy:

The diagnosis is usually a clinical one. Cerebrospinal fluid and bone marrow must be examined to check for metastatic disease. Investigations

Treatment

1. Removal (enucleation) of eye in advanced cases.

2. Radiotherapy and brachytherapy

3. Cryotherapy

– killing the tumor in a series of freeze – thaw cycles using an externally applied cryoprobe.

4. Laser photocoagulation -small tumors.

5. Metastatic disease (direct spread -optic nerve or hematogenous route) treated with chemotherapy.

6. Regular follow - up and examination of fellow eye of an affected child is required.

Prognosis

• Depends on extent of disease at diagnosis.

• Overall, mortality is 15%.

• Unfortunately 50% of children with germinal mutation will develop a second primary tumor (e.g. osteosarcoma of femur) or tumor related to treatment with radiotherapy.

Multiple choice questions

1. Match symptoms with the likely abnormal part of retina.• a Distortion of vision (metamorphopsia).• b Loss of superior visual field.• c Difficulty seeing at night.

i The inferior half of the retina.

ii The macula.

iii The rods.

iv The cones.

2. Age- related macular degeneration

• A) Commonest cause of irreversible visual loss in developed world.

• B) Associated e disease of retinal pigment epithelium.• C) Associated with growth of blood vessels beneath retina.• D) Caused by a hole forming at macula.• E) Commonly treated with surgery.

Macular edemaA) Relates to accumulation of fluid within macula.B) Causes blurring of vision.C) Seen following intraocular surgery.D) Associated with growth of abnormal vessels in retina.E) Treated with steroids.

5. A patient presents with a history of 3 days of floaters, flashing lights and then a dense, curtain - like field loss.A) Most likely diagnosis is retinal vein occlusion.B) Most likely diagnosis is retinal detachment.C) Most likely diagnosis is posterior vitreous detachment.D) Patient needs urgent referral to an eye unit.E) Vision will settle with no intervention.

6. A 1-year-old child presents with a squint. Doctor notices that red reflex appears white.A) White red reflex is normal finding in a child of this age.B) Child may have a retinoblastoma.C) Child has albinism.D) Urgent referral is required.E) The other eye needs to be assessed.