Common conditions of the eye

Question 1

Explain why corneal grafts are less likely to be rejected

Answer 1

• The avascularity of the cornea is of benefit to surgeons when preforming a graft surgery as it means there is a lesser chance of foreign antigens from a corneal graft being recognised by the recipient, so lesser chance of a graft rejection
  
  • This has lead researchers to believe the cornea is an immune privileged site
  • There are no lymphatics draining the eyeball; though lymph drains the eyelids

Question 2

How are cataracts formed?

Answer 2

• Older (embryological, foetal) fibres are never shed- compact in the middle
  
  • There is no blood supply to the lens, which depends entirely on diffusion for nutrition
  • Absorbs harmful UV rays preventing them from damaging the retina but in the process, get damaged themselves
  • Damaged lens fibres → opaque → cataract

Question 3

What is conjunctivitis and what is the treatment?

Answer 3

○ Self-limiting bacterial or viral infection of the eye
○ Red, watering eyes with some discharge
○ No loss of vision as long as the infection doesn’t spread to the cornea
○ Treatment: antibiotic eye drops if likely to be bacterial

Question 4

What is a stye or hordeolum and what is the management for them?

Answer 4

○ Blockage of sebaceous glands cause this condition

○ Management: Warm compress, eyelid hygiene, may need surgical incision and cuettage

Question 5

Explain corneal ulcers

Answer 5

○ Infections
- viral/ bacterial/ fungal infection of cornea
- Needs aggressive management to prevent spread, scarring
○ Non-infectious ulcers
- Trauma
- Corneal degeneration
- Dystrophy

Question 6

What are corneal dystrophies?

Answer 6

○ They are a group of diseases affecting the cornea which are
§ Bilateral
§ Opacifying
§ Non-inflammatory
§ Mostly genetically determined
§ Sometimes due to accumulation of substances such as lipids in the cornea

Question 7

What are the clinical presentations of corneal dystrophies?

Answer 7

• First to fourth decade
• Most commonly- decreased vision
• Start in one of the layers of the cornea and spread to others

Question 8

What is the management of cataracts?

Answer 8

• Eye drops do not treat cataracts
• Surgery: (day case) small incision causing the lens capsule to be opened and the cataracts lens is removed by emulsification (phacoemulsification)
• Lens implant after cataract surgery

Question 9

What is glaucoma?

Answer 9

○ Raised intraocular pressure
○ 2nd most common global cause of blindness
○ Consequences of raised IOP
- Pressure on optic nerve head as nerve fibres die out
- When seen by ophthalmoscopy the optic disk appears unhealthy, pale and cupped
- This results in an altered field of vision
- Ultimately all nerve fibres are lost, which results in blindness

Question 10

Describe Primary open angle glaucoma (POAG)

Answer 10

• Bilateral
• Patients can be asymptomatic for a long period of time
• Picked up on routine eye exams

Question 11

What is the management of POAG?

Answer 11

- Eye drops to decrease IOP
	□ Prostaglandin analogues
	□ Beta blockers
	□ Carbonic anhydrase inhibitors
- Laser trabeculoplasty
- Trabeculoplasty surgery

Question 12

What is angle closure glaucoma?

Answer 12

• Sudden onset, painful, vision lost/ blurred; headaches (often confused with migraine)
• Red eye, cornea often opaque as raised IOP drives fluid into the cornea
• AC shallow, and angle is closed
• Pupil mildly dilated
• IOP severely raised

Question 13

Why does the angle close?

Answer 13

□ Functional block in a small eye: large lens
□ Mild-dilated pupil results in the periphery of the iris crowding around the angle which means that outflow is obstructed
□ Iris stick to the pupillary boarder (synechia) which prevents reaching AC which leads to iris ballooning anteriorly and obstructing the angle

Question 14

How do you manage an acute episode of angle closure glaucoma?

Answer 14

□ Decrease IOP
® IV infusion with or without oral therapy: carbonic anhydrase inhibitors (acetazolamide)
® Analgesics, antiemetics
® Constrictor eye drops- pilocarpine
® If no contraindication, beta-blocker drops such as timolol
® Steroid eye drops (dexamethasone)
□ Iridotomy (laser)- both eyes- to bypass blockage

Question 15

What are the causes of uveitis?

Answer 15

• Isolated illness
• Non-infectious autoimmune causes e.g. presence of HLA-B27 predisposes to anterior uveitis
• Infectious causes: chronic diseases such as TB
• Associated with systemic diseases e.g. ankylosing apondylosis

Question 16

What are the types of uveitis?

Answer 16

• Anterior uveitis
  □ Iris with or without ciliary body inflamed
  □ Leaks plasma and white blood cells into the aqueous humor
  □ These are seen during slit lamp examination as a hazy anterior chamber and cells deposited at the back of the cornea
  □ The eye is red, painful with visual loss
  □ Cells in the AC may settle inferiorly- hypopyon
• Intermediate uveitis
  □ Ciliary body inflamed
  □ Leaks cells and proteins
  □ This leads to a hazy vitreous, Patients complain of “floaters” or hazy vision
• Posterior uveitis
  □ Choroid inflamed
  □ Since the choroid sits under the retina, the inflammation frequently spreads to the retina causing blurred vision