Anatomy of the Eye & Refractive Errors

Question 1

Where is the anterior segment and the posterior segment of the eye?

Answer 1

Anterior segment – cornea to lens. Posterior segment – everything behind the lens.

Question 2

Describe the innervation of the cornea.

Answer 2

• Cornea is densely innervated by ophthalmic division of trigeminal nerve via anterior ciliary nerves. Corneal nerves have a sensory and trophic function.
• Damage to corneal nerves can lead to loss of sensation and epithelial breakdown.
• Important to check corneal sensation in suspected herpetic eye disease.

Question 3

What are 7 Key ophthalmic symptoms to screen for during a ophthalmic history taking?
- Outline the ophthalmic history/exam protocol?

Answer 3

Question 4

List 5 ‘Red Flag’ features of ophthalmic pathology?

Answer 4

Question 5

List 11 Closed questions relevant to visual disturbance to ask during an opthalmic history taking?

Answer 5

Question 6

Answer 6

Question 7

What are refractive errors?
- 4 types?

Answer 7

• Refractive errors are a type of vision problem that makes it hard to see clearly. They happen when the shape of your eye keeps light from focusing correctly on your retina (a light-sensitive layer of tissue in the back of your eye).
• Refractive errors are the most common type of vision problem. More than 150 million Americans have a refractive error — but many don’t know that they could be seeing better. That’s why eye exams are so important.
• If you have a refractive error, your eye doctor can prescribe eyeglasses or contact lenses to help you see clearly.

Question 8

Myopia
- Pathophysiology?
- Clinical features?
- Treatment?
- Complications?

Answer 8

Myopia (short-sightedness)
- Pathophysiology: abnormally increased axial length of the eye or, less commonly, increased refraction → focal point anterior to the retina.
- Clinical features: clear near vision, blurred far vision.
- Treatment: glasses with concave (diverging) lenses or refractive surgery
- Complications: retinal detachment, macular degeneration.

Question 9

Presbyopia
- Pathophysiology?
- Clinical features?
- Treatment?

Answer 9

Presbyopia
- Pathophysiology: age-related decrease in lens elasticity, strength of ciliary muscle, and lens curvature → decreased lens accommodation (focusing on an object up close)

Clinical features
- Similar to hyperopia
- Preexisting myopia may temporarily compensate presbyopia, leading to better near vision (second sight)

Treatment: reading glasses with convex lenses or refractive surgery

Question 10

Astigmatism
- Pathophysiology?
- Clinical features?
- Treatment?
- Complications?

Answer 10

Astigmatism
- Pathophysiology: abnormal curvature of the cornea → refractive error hinders even refraction → two or more focal points, which can be anterior and/or posterior to the retina, depending on the curvature
- Clinical features: blurred vision at all distances

Treatment
- Regular astigmatism: cylindrical lenses
- Irregular astigmatism: corrective contact lenses and refractive surgery

Complications: early onset increases risk for amblyopia