11.5.1 Retinal Vasculopathies And Systemic Diseases

Question 1

How does the fibres of the superficial nerve fibre lie?

Answer 1

Parallel to retinal surface

Question 2

How does the elements of the deeper retinal layers lie

Answer 2

Parallel to the incident of light

Question 3

Blood supply of the retina

Answer 3

Inner - retinal blood vessels
Outer (incl. photoreceptors) - choriocapillaries

Question 4

Intraretinal hemorrhages important fundus signs

Answer 4

• blood track in same direction as the adjacent retinal elements.
• Superficial blood tracks along the fibres in the nerve fibre {parallel to the surface} -> flame-shaped or striated appearance
• Deeper layers tracks along the deeper fibres, {perpendicular to the surface} -> dot and blot appearance

Question 5

Microaneurysms important fundus signs

Answer 5

• Small, perfectly round, red spots on the retina, with a diameter smaller than that of the large vein at the disc margin
• irregularity = spot is a deep haemorrhage and not a microaneurysm

Question 6

Hard exudates important fundus signs

Answer 6

• Yellowish-white spots with well circumscribed (hard) margins.
• represent intraretinal lipid deposition and are a sign of true intraretinal exudation.
• Lipids which have leaked into the tissues during exudation tend to be less easily reabsorbed because of their large molecular size.

Question 7

Cotton wool spots important fundus signs

Answer 7

• White spots with poorly circumscribed, often striated or fluffy (soft) margins.
• represent areas of severe nerve fibre layer ischaemia or infarction.

Question 8

Relative retinal pigment epithelial change important fundus signs

Answer 8

• Any damage to the retinal pigment epithelium causes irregular black and white markings in the fundus due to:
  ➡️hypertrophy
  ➡️hyperplasia
  ➡️atrophy
  ➡️migration of the pigment epithelium.
• Pigment epithelial damage is usually associated with damage to adjacent structures such as retina and choriocapillaris.

Question 9

Grading of Hypertension & Arteriosclerosis retinopathy

Answer 9

HYPERTENSION
1. Hypertension results in diffuse narrowing of the visible blood column in arterioles relative to venules due to generalised vasoconstriction.
2. As hypertension becomes worse, areas of focal vasoconstriction produce areas of focal narrowing.
- Focal narrowing is the most reliable fundoscopic sign of systemic hypertension and usually indicates a diastolic >110mmHg.
3. Severe hypertension produces arteriolar obstruction and vessel wall necrosis which manifest as nerve fibre layer haemorrhages, hard exudates and cotton wool spots.
4. Malignant hypertension with diastolic pressures of 130-140mmHg is associated with optic disc swelling.

ARTERIOSCLEROSIS
1. Arteriosclerosis results in diffuse narrowing of the visible blood column in arterioles relative to venules due to hypertrophy and fibrosis of the media.
- light reflex from the vessel wall = more prominent and the blood column becomes paler to produce an appearance of copper wiring and eventually silver wiring when the reflex is relatively broad and the blood column is very pale or invisible.
2. Arteriolovenular (AV) crossing changes become more prominent as the sclerosis progresses.
-First the venule tapers to disappear behind the arteriole, called AV nipping, and eventually it changes direction at the crossing.

Question 10

Diabetes Mellitus Pathology

Answer 10

• basic pathology is a microvasculopathy.
• It consists of the following:
  (a) Capillary outpouching: microaneurysms.
  (b) Capillary occlusion:
  ➡️leakage
  ➡️haemorrhage
  ➡️ischaemia

Question 11

Diabetes Mellitus consequences + complications of ischaemia

Answer 11

Ischaemia → neovascularisation
- Neovascularisation - abortive attempt to revascularise ischaemic retina.
- produces vascular endothelial growth factor (VEGF) which diffuses to all parts of the eye and stimulates the ingrowth of new vessels.
- New vessels → leakage haemorrhage

Complications of neovascularisation:
- Neovascular glaucoma: destruction of the iridocorneal drainage angle.
- Massive intraretinal exudation.
- Vitreous haemorrhage → vitreous traction bands → tractional retinal detachment. The net effect is that neovascularisation does much more harm than good.

Question 12

Classification of Diabetes Mellitus
Extramacular retinopathy
Muculopathy

Answer 12

Extramacular retinopathy
BACKGROUND
- Microaneurysms
- Hard exudates
- Haemorrhages (Mainly deep: dot and blot; Unusually superficial: flame shaped)
PREPROLIFERATIVE
- Venous beading, kinking and looping
- Cotton wool spots
- Extensive deep haemorrhages
- Vascular occlusions
PROLIFERATIVE
- Neovascularisation

Maculopathy
BACKGROUND
- As for extramacular retinopathy but with minimal exudation
EXUDATIVE
- Emphasis on oedema and hard exudates
ISCHAEMIC
- Usually an angiographic diagnosis

Question 13

Central retinal arterial occlusion mechanism

Answer 13

• Thrombosis and embolism.
• The effects of an occlusion may be transient or permanent.
• Carotid atherosclerotic plaques are the main source of emboli in older patients
• Cardiac valvar lesions are the main source in younger patients.

Question 14

Central retinal arterial occlusion signs and symptoms

Answer 14

Symptoms
- Sudden, unilateral, severe loss of vision in a comfortable white eye.
- One or more episodes of temporary loss of vision known as amaurosis fugax may precede occlusion. (sudden loss of vision which spontaneously resolves within 24 hours, but usually within a few minutes. Due to temporary embolic occlusion of the central retinal artery)

Signs
- Visual acuity is usually HM to no PL.
- Visual field loss.
- Relative afferent pupil defect.
- Mild optic disc swelling.
- Milky white retina especially around the macula as a result of nerve fibre layer ischaemia and swelling.
- Cherry red spot: Because the retina in the centre of the macula is thin, swelling is minimal in this area, and the normal colour of the choriocapillaris can still be seen through the retina. Because of the surrounding pale retina, the centre of the macula appears unusually red.
- Narrowed arterioles and venules
- An embolus may be visible in the artery.

Question 15

Why does neovascularisation not occur in central retinal arterial occlusion?

Answer 15

The infarcted retina is unable to produce as vasoproliferative factor

Question 16

Central retinal venous occlusion associations

Answer 16

• Hypertension and arteriosclerosis
• Diabetes mellitus
• Glaucoma

Question 17

Central retinal venous occlusion symptoms and signs

Answer 17

Symptoms
- Sudden, unilateral loss of vision of very variable degree in a comfortable white eye.

Signs
- Visual acuity and visual field vary from almost normal to severe loss, depending on the degree of obstruction: 6/9 to HM
- Afferent pupil defect in severe cases.
- Dilated and tortuous venules.
- Optic disc swelling.
- Retinal haemorrhages are widely spread throughout the fundus into the periphery.
➡️Mainly nerve fibre layer (flame shaped) in less severe cases.
➡️Mainly deep (dot and blot) in more severe cases.
- Cotton wool spots in more severe cases.
- Hard exudates may occur.

Question 18

Central retinal venous occlusion complication

Answer 18

Neovascularisation

Question 19

Retinopathy of prematurity risk factors

Answer 19

• Birth weight < 1 500g.
• Birth weight < 2 000g with an unstable clinical course.
• Gestational age < 30 weeks.
• High saturation O2 therapy.

Question 20

Retinopathy prematurity pathogenesis

Answer 20

• Vascularisation of the human retina begins at about 16 weeks of gestation. It starts at the optic disc and progresses to the periphery but is only completed at about 40 weeks of gestation.
• For reasons which are poorly understood, babies with the risk factors tend to develop neovascularisation at the junction of vascularised and nonvascularised retina.
• Leakage, haemorrhage and fibrosis result, and the contraction of the resultant fibrovascular membrane leads to tractional retinal detachment. The end stage is known as retrolental fibroplasia, and is a cause of leukocoria, the appearance of a white pupil.
• The role of high saturation O2 therapy is controversial. There are circumstances under which it may both worsen and improve the retinopathy, and so should still be considered a risk factor and used with caution at as low a saturation as is practical.

Question 21

Define retinitis pigmentosa

Answer 21

Group of inherited diseases characterised by progressive deterioration of photoreceptor and retinal pigment epithelial structure and function.
The term “retinitis” is a misnomer as there is no evidence of retinal inflammation.

Question 22

Clinical findings of retinitis pigmentosa

Answer 22

SYMPTOMS
- bilateral and relatively symmetrical.
- age of onset and speed of progression varies between and within affected families.
- Night blindness is usually the first symptom.
- clumsiness due to the gradual reduction of visual field.
- Initially visual acuity is unaffected, but it declines later.

SIGNS
FUNDOSCOPY
- Irregular retinal pigment epithelial clumping is first noticed in the midperiphery (bone spicule appearance)
- Retinal pigment epithelial atrophy produces depigmentation between the areas of pigment clumping.
- As the disease progresses, the pigment changes spread centrally and peripherally. The macular area is spared until very late in the course of the disease.
- Retinal arterioles are narrowed secondary to retinal atrophy.
- disc becomes pale as a result of the loss of nerve fibres
VISUAL FIELDS
- ring scotoma that gradually enlarges peripherally and centrally

Question 23

Age related macular degeneration (ARMD)
Classification
Symptoms
Signs

Answer 23

CLASSIFICATION
- Atrophic or dry type: avascular degenerative changes.
- Exudative or wet type: subretinal neovascularisation.

SYMPTOMS
- Painless decrease in visual acuity to 6/60 or worse in a comfortable white eye:
➡️Dry: gradual decrease over many years.
➡️Wet: sudden visual loss may occur due to haemorrhage or exudation.
- Metamorphopsia: image distortion due to retinal distortion occurs mainly in the wet type.
- Symptoms of a central or paracentral scotoma (partial loss of vision = blind spot)

SIGNS
- Decreased visual acuity.
- Metamorphopsia or a central scotoma may be demonstrable using an Amsler grid.
Fundoscopy
- Dry type
(i) Drusen: round yellowish spots of various sizes visible subretinally.
(ii) Pigmentchangesinthemaculararea.
- Wet type
(i) Drusen
(ii) Consequences of subretinal neovascularisation:
• Leakage under the RPE and/or neuroretina
• Haemorrhage under the RPE and/or neuroretina
• Scar formation under and in the neuroretina

Question 24

Retinoblastoma
Epidemiology
Presentation

Answer 24

Epidemiology
- rare (commonest primary intraocular malignancy in children)
- age of diagnosis = 18 months
- 30% bilateral
- caused by defect in gene coding for a tumour suppressor protein
- inherited or sporadic

Presentation
- Leukocoria 67%
- Strabismus 20%
- Others 13%, for example proptosis, uveitis, hyphema, glaucoma, or absence of the red reflex during a routine examination.