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OD2 S1 > Fusion: 1-2 Lasik - Week 12 > Flashcards

Fusion: 1-2 Lasik - Week 12 Flashcards

1
Q

What 5 features in this patient’s history are relevant/worth taking note of?

A

41 yr old accountant
sharp pains in eyes for the last week
refractive surgery 7 months earlier
grittiness and irritation few months after surgery
no longer uses eye drops from after surgery

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2
Q

What does lasik do? Explain the procedure (3)

A

Permanently changes cornea by cutting a corneal flap
Tissue from corneal centre is removed with excimer laser
Corneal flap is replaced

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3
Q

What is lasik used for? (3)

A

Correction of myopia, hyperopia and astigmatism

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4
Q

What medications should you take after lasik and for how long? (2, 1)

A

Antibiotic and Steroid anti-inflammatory eye drops (2-3 weeks)

*e.g. antibiotic = chloramphenicol
anti-inflamm = voltaren

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5
Q

How often should you use artificial tears/eye lubricating drops after lasik?

A

every 2 hours

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6
Q

How often should you use antibiotic eye drops after lasik?

A

4 times a day

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7
Q

How does the patient describe the pain in regards to:
A: location
B: severity
C: binocular/monocular
D: transient/constant
E: gaze

A

A: frontal
B: sharp acute pain
C: binocular
D: transient
E: no particular gaze

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8
Q

Does the patient have air-conditioning at work?

A

yes

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9
Q

List 10 symptoms of dry eye

A

burning
itchy
aching
heavy eyes
fatigued eyes
sore eyes
red
photophobia
blurred

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10
Q

What is the central pathogenic mechanism behind Dry Eye Disease? (DED) And what does this result in?

A

Hyperosmolarity. Results in ocular surface inflammation and damage

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11
Q

How does hyperosmolarity arise?

A

Arises from a loss of tear film homeostasis, where there is reduced aqueous tear flow and/or increased evaporation of the aqueous tear phase from the exposed ocular surface

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12
Q

What are the 3 main features of DED?

A

Loss of tear film homeostasis
Hyperosmolarity (as a result)
Ocular surface inflammation and damage (as a result)

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13
Q

What do you call dry eye resulting from reduced aqueous tear flow?

A

aqueous-deficient dry eye

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14
Q

What do you call dry eye resulting from increased evaporation of the aqueous tear phase?

A

evaporative dry eye

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15
Q

Briefly describe how you would structure the consultation in this patient (considering you suspect dry eye disease)? (3)

A
  1. Clinical presentation: consider age, gender, tasks, env.
  2. Consider differentials: determine likely presentation, use ocular surface dryness index
  3. Further tests: TBUT, assess osmolarity, ocular surface staining
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16
Q

Provide 5 questions you may ask when suspecting dry eye disease/dry eye

A

How severe is your eye discomfort?
Do you have any mouth dryness or swollen glands? (could indicate sjogren’s)
How long have symptoms lasted and was there any triggering event?
Is vision affected and does it clear on blinking?
Do you wear CLs?

*Note there are other questions too

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17
Q

List 3 risk factors for dry eye

A

Smoking
Certain medications
CL wear

(also Lasik)

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18
Q

What tests do you perform to diagnose DED? (1, 3)

A

Symptomology (screening) plus 1 of either:
- non-invasive TBUT (NIBUT)
- Osmolarity
- Ocular surface staining

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19
Q

How can you classify between the 2 subtypes of DED?

A

Evaporative: if - abnormal lipid, MGD (meib. gland, dysfunction)
Aqueous deficiency: if - low volume

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20
Q

What is the formula for OSDI? (Ocular Surface Disease Index)

A

OSDI = (sum of severity for all answered questions x 100) / (total # of questions answered x 4)

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21
Q

What is the OSDI range criteria for the following DED severity levels?
- Mild DED
- Moderate
- Severe

A

Mild: 13-22
Moderate: 23-32
Severe: >/= 33

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22
Q

How does hyperosmolarity correlate to DED severity?

A

High correlation. Increases linearly with disease severity

23
Q

How is tear stability assessed?

A

by gathering a small sample from lower eyelid tear meniscus

24
Q

What are the 2 important values to note during tear testing?

A
  1. Highest reading between the two eyes
  2. Inter-eye variation (difference between the two eyes)
25
Q

What test can we use to assess tear volume?

A

Schirmer Test: provides an estimation of the stimulated reflex tear flow

26
Q

How does the Schirmer Test work: How do you perform it and how do you score/measure? (3)

A

fold schirmer paper strip by hooking it over the temporal 1/3 of the lower lid margin:
- px must keep eyes open and fixate on a target
- score by observing the measured length of wetting from the mouth after a period of 5 minutes

27
Q

What is the cut-off for normal values in the Schirmer Test specified as?

A

Less than 10mm/5min

Anything that is less than 10mm/5min is considered DED

28
Q

What does a TBUT rupture time less than or equal to 10 seconds indicate?

A

malfunction in oil content of lacrimal fluid

29
Q

What would be a positive result for DED in osmolarity testing? Did our patient satisfy this criteria?

A

A positive result is considered to be >/= 308mOSm/L

Our patient had RE: 320 and LE: 318. So yes she does have a positive osmolarity result for DED

30
Q

What is the healthy population mean result for osmolarity testing?

A

301 and 299mOSm/L

31
Q

What are the 2 general approaches for tx/management of DED?

A

Tear replacement approaches: artificial tears
Tear conversion approaches: punctal occlusion with plugs

32
Q

Name 3 artificial tear drops to treat DED (in terms of compounds used)

A

Carboxylmethyl cellulose (CMC)
Hyaluronic acid (HA)
Combination of CMC and HA

33
Q

What are 5 potential complications of LASIK?

A

Mild irritation
Light sensitivity/photophobia
Glares
Halos
Dry Eyes

34
Q

List 4 symptoms of Dry eye

A

Blurred vision
Light sensitivity
Stinging sensation
Watery eyes (as counterintuitive as it sounds)

35
Q

How can we measure the subjective sensation of ocular pain experienced by the patient? (2)

A

OPAS: Ocular Pain Assessment Survey
IASP: International Association for the Study of Pain - has a grading system for describing pain

36
Q

What proportion of Lasik patients have dry eye symptoms post lasik?

A

Around 50%

37
Q

For people with DED post lasik: How long after lasik do symptoms peak? And how long until they typically resolve? What does this timeline match/correlate with?

A

symptoms peak: 1-3 months post-op
symptoms resolve: within 6 months

This matches up with central corneal sensation and a period of rapid nerve density recovery [so relates to corneal neuropathic pain]

38
Q

What is ADDE type DED?

A

Aqeuous Deficient Dry Eye

39
Q

What 4 types of DED occur post-lasik?

A

ADDE type DED
Hyposecretory issue (lacrimal unit dysfunction)
Reflex afferent block
Trigeminal nerve injury

40
Q

Describe the corneal pain pathway

A
  1. (ipsilateral) Sensory fibres within the trigeminal ganglion project centrally to 2 spatially discrete regions of the trigeminal brainstem complex
  2. These 2 regions are: trigeminal subnucleus interpolaris/caudalis transition region (Vi/Vc) and the caudalis/upper cervical cord junction (Vc/C1)
  3. (contralateral) 2nd order neurons in Vi/Vc and Vc/C1 project to higher centres in the brain, such as the thalamus, paralimbic region and somatosensory cortex, which contributes to the ocular pain sensation

(note, they also project to other regions of the brain to mediate other things like eyeblink and lacrimation)

41
Q

Where are most corneal nerves derived from?

A

ophthalmic division of trigeminal nerve

42
Q

Where in the cornea do stromal nerve trunks enter?

A

peripheral corneal stroma

43
Q

Where in the cornea are free nerve endings found?

A

within epithelial layers

44
Q

Name the 3 subtypes of corneal sensory neurons

A

Polymodal nociceptor neurons
Cold thermoreceptor neurons
Selective mechano-nociceptor neurons

45
Q

How are corneal nerves affected by lasik? (3)

A

corneal nerves are transected
- incl. subbasal plexus and stromal nerves
- subbasal plexus density decreases by over 80%

46
Q

How long does complete regrowth of the subbasal nerve take after lasik?

A

years

47
Q

How does disease to the nerves affect responsiveness/sensitivity to stimulation (i.e. pain sensitivity)? By what mechanism does this occur?

A

Increases responsiveness/sensitivity. This happens via altering the spontaneous and stimulus-evoked firing pattern and then changing the density and distribution of Na and Ca channels, K channel expression and activation threshold

48
Q

How can environmental conditions increase pain sensitivity?

A

Mechanical stress can alter corneal nerve fibre architecture, leading to inflammation

49
Q

Define neuropathic pain

A

pain caused by damage or disease affecting the somatosensory nervous system

50
Q

List 3 symptoms of neuropathic pain

A

burning
coldness
pins and needles

51
Q

What are 3 theories/perspectives on neuropathic pain

A

Injured afferent hypothesis:
Intact nociceptor hypothesis:
Role of central sensitization

52
Q

Explain the Injured afferent hypothesis

A

injured afferent itself is what causes the neuropathic pain

53
Q

Explain the Intact nociceptor hypothesis

A

the intact nociceptors that survive injury and that innervate the region affected by the transected nerve fibers sensitize and have spontaneous activity.

These changes in the intact nociceptors may induce ongoing pain and may account for certain aspects of hyperalgesia.

54
Q

Explain the role of central sensitization in neuropathic pain

A

Central sensitization refers to the augmented response of central signaling neurons.

When it occurs as a result of inflammation, central sensitization is strongly dependent on ongoing input from nociceptors. Thus, if nociceptive input is blocked in the injury zone, secondary hyperalgesia abates promptly (LaMotte et al., 1991). This same dependence on peripheral input probably also applies to central sensitization associated with neuropathic pain, but this issue requires further clarification. This distinction is of great importance clinically. If mechanisms of pain are completely centralized, it might be argued that attention to peripheral mechanisms is unlikely to be therapeutically beneficial.

OD2 S1 (47 decks)

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