Ophthalmology: Optometry & Orthoptics

Question 1

Describe how we test visual acuity in adults

Answer 1

• Test each eye separately
• Wear glasses/contacts if have them
• Test at 6m (can be less if poor visual acuity)
• If visual acuity lower than expected can recheck visual acuity using pinole (if better through pinhole this could indicate uncorrected refractive error or cataract)

Question 2

Stat the two charts we use to test visual acuity in adults

Answer 2

• Snellen chart
• LogMAR chart

Question 3

Explain how to record visual acuity on a Snellen chart

Answer 3

• Numerator is distance e.g. 6 for 6m
• Denominator is the distance at which someone with normal vision would be able to see this letter
• If pt doesn’t get all of letters on line correct express as either:
  
  • line above + however many letters from line below
  • Line they were on - how many letters on that line they got wrong

Question 4

Explain how to record visual acuity on a LogMAR chart

Answer 4

• Each line has score of 0.1
  
  • 5 letters on each line hence each letter has a score of 0.02
• 10 lines, therefore max score of 1
  
  • Higher number= worse vision
• Value of the best read line + (0.02 x number of letters incorrect)

Question 5

Briefly outline how we can assess vision in children

*Don’t worry about detail; just have awareness

Answer 5

• Keeler preferential looking cards: big cards with lines of different spacings/gratings on, examiner sees if look towards grating. 8 weeks-12 months
• Cardiff acuity cards: simple picture at top or bottom of card, see if child looks at picture. 3-18 months
• Kay pictures: pictures and matching picture card that child can point to to copy the one you showed them. 2 - 4 yrs
• LogMAR keeler book: letters and matching letter card. 4+ years

Question 6

If visual acuity is to low to use the Snellen or LogMAR chart, how else can we test visual acuity?

Answer 6

1. Counting fingers
2. Hand movements
3. Perception of light
4. No perception of light

**Worse as you go down

Question 7

What is the minimum driving standard visual acuity?

Answer 7

• Snellen= 6/12
• LogMAR= 0.3

Question 8

Define strabismus

Strabismus can be classified into concomitant and paralytic; explain meaning of each

What is meant by convergent and divergent squint?

We also talk about manifest and latent deviation when talking about strabismus; explain meaning of each

Answer 8

Definition: Strabismus (squint) is misalignment of the visual axes

Classification

• Concomitant (common): angle of deviation (i.e. the size/magnitude of the squint) is the same in all positions of gaze- due to imbalance of extraocular muscles
• Paralytic (rare): angle of deviation (size/magnitude of the squint) varies in different positions of gaze- due to paralysis of extraocular muscles

Convergent vs divergent

• Most often, one eye turns inwards (convergent squint) or outwards (divergent squint). Less often, it may turn up or down (vertical squint).

Deviation

• Manifest deviation – this refers to a deviation of the eyes (misalignment/strabismus) that is present when both eyes are open and the patient is looking at a target and alert (see figure 1 examples). Largely when we talk about strabismus it is this manifest deviation we are concerned with
• Latent deviation – everyone has a tendency for their eyes to naturally turn outwards or inwards at rest. When awake and alert and looking at an object/target we align the eyes. Latent deviations are therefore usually of no clinical significance. Clinically they may become significant if the latent deviation becomes manifest when under conditions of fatigue and/or physiological stress (stress, illness, drugs, alcohol).

Question 9

What test can we use to quickly screen for strabismus in children? Explain how to perform this test

Answer 9

Corneal reflection test: holding a light source 30cm-1m (sources vary) from the child’s face to see if the light reflects symmetrically on the pupils

Question 10

We can use corneal light reflection test to quickly screen for a squint; what test is used to determine the nature of the squint? Describe how this test is done

Answer 10

Cover test

• ask the child to focus on an object
• cover one eye
• observe movement of uncovered eye
• cover other eye and repeat test

Question 11

Define the following squints on the image

Answer 11

Convergent (esotropia) more common than divergent (exotropia)

Question 12

Why is it so important to correct strabismus in children?

Answer 12

Can lead to amblyopia (brain fails to fully process inputs from one eye & over time favours the other reye)

Question 13

What is amblyopia?

State some potential causes

Answer 13

Amblyopia, also called lazy eye, is a disorder of sight in which the brain fails to fully process inputs from one eye and over time favours the other eye/reduced vision -typically in one eye- that results from the brain suppressing input from the affected eye due to unequal visual signals from each eye

• Causes include:
  
  • Strabismus
  • Anisometropia
  • High bilateral refractive error
  • Stimulus deprivation e.g. due to ptosis, congenital cataract
  • High astigmatism

Question 14

Discuss the management of strabismus in children

Answer 14

• Glasses (must allow period of refraction adaptation when give new prescription (~20 weeks))
• Above not worked, occlusive patch over better eye
• Squint surgery (once vision is equal in both eyes but squint still noticeable even with refractive correction)

Question 15

If someone says they have double vision, what key things must you establish?

Answer 15

• Is it monocular or binocular?
• Is it horizontal, vertical or oblique

Question 16

What are the potential treatment options for adults with diplopia

Answer 16

• Prisms (stick on glasses or incorporated into glasses)
• Occlusion (eye patch, occlusive contact lens, blenderm)
• Surgery