11.5.2 Degenerative Conditions Of Retina, Retinal Cancer & Detachments

Question 1

Viterous degeneration

Answer 1

• In all adults gradual degenerative liquefaction of the vitreous occurs.
• Small liquid filled spaces develop in the central gel. These gradually coalesce to form larger liquid filled spaces which eventually involve large parts of the central gel

Question 2

Posterior vitreous detachment (PVD)
Def
RF

Answer 2

Def:
- in posterior hyaloid membrane
- communication between lacunae of liquified vitreous and potential space between retina and posterior hyaloid membrane
- dissection of fluid into potential space separates posterior hyaloid membrane from retina (gradual / rapid)

Pathogenesis:
- floaters in form of moving threads and dots in visual field are caused by local thickenings in degenerative gel (increase during PVD)
- traction is placed on retina in areas of tighter adhesion between posterior hyaloid membrane and retina (stim photoreceptors = flashes of light) -> disappear when PVD is complete

Risk factors
- myopes
- diabetics
- vitreous inflammation
- haemorrhage

Question 3

Define Retinal detachment

Answer 3

• The loose adhesion between the neuroretina and the retinal pigment epithelium (RPE) is broken
• two structures are anatomically separated from each other by the collection of fluid.

Question 4

Classification of retinal detachment

Answer 4

Classification by mechanism

SEROUS
- Exudation occurs under the neuroretina. E.g. inflammatory conditions, tumours.

TRACTION
- Vitreous bands exercise mechanical traction on the neuroretina without causing retinal breaks. E.g. advanced diabetic retinopathy.

RHEGMATOGENOUS
- Each of the following 3 factors must be present to cause the detachment:
1. A retinal break (hole or tear).
2. Vitreoretinal traction on the edge of the break.
3. Fluid movement through the break.
- duration of this process may vary from hours to years.
- commonest and the most important type of retinal detachment

Question 5

Retinal break formation

Answer 5

1. Vitreous traction during PVD
2. Vitreous traction during direct blunt trauma to the eye. Traction occurs during transient distortion of the globe.
3. Degenerative holes with vitreous traction.

Question 6

Rhegmatogenous retinal detachment symptoms & signs

Answer 6

SYMPTOMS
- Symptoms of posterior vitreous detachment, if this is the cause: Light flashes, floaters.
- Symptoms of a vitreous haemorrhage:
A retinal blood vessel is often involved in a retinal tear, and the red blood cells in the vitreous cause a sudden shower of dot-like floaters.
- Symptoms of the detachment:
A shadow or curtain over part of the visual field.
A sudden loss of vision when the macula is included in the detachment.

SIGNS
- Loss of visual field (Because the neuroretina is metabolically dependent on the RPE, any retinal detachment causes a scotoma in the area of the detachment)
- Decrease in visual acuity if there is a macular detachment or vitreous haemorrhage.
- Relative afferent pupil defect if the detachment is large.
- Absent red reflex: (The detached retina becomes irregular, white and opaque, obscuring the underlying choriocapillaris which is responsible for the red reflex)
- Bulging white retinal folds containing blood vessels are seen during ophthalmoscopy

Question 7

Primary congenital glaucoma
General
Signs & symptoms

Answer 7

• Rare
• Usually sporadic
• Often bilateral, may be asymmetric
• Features depend on age of onset and level of IOP e.g.
  • True congenital: elevated IOP in-utero
  • Infantile: manifest before 3
  • Juvenile: between 3 and 16

Signs & Symptoms

Corneal haze
- May be first sign noted by parents
- Due to oedema of the cornea
- Causes:
• Lacrimation
• photophobia
• blepharospasm

Buphthalmos
• Large eye due to elevated IOP prior to age three
• Thinned sclera may take on a blueish appearance
• Enlarged eye can be myopic (short sighted)

Other signs
- Breaks in corneal lining – Haab Striae
- Opticdisccupping

Requires urgent referral