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III. Glaucoma Management > IOP, CCT, and Hysteresis (M) > Flashcards

IOP, CCT, and Hysteresis (M) Flashcards

1
Q

Why is the IOP correction factor no longer done?

A

relationship was not linear

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2
Q

What is the normal range of IOP?

A

10 to 21mmHg

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3
Q

What are the problem cells in the trabecular meshwork when there is trouble with outflow?

A

juxtacanilicular

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4
Q

What is the device that has the tip match the contour of the cornea so that the IOP is independent of the CCT or corneal irregularity?

A

Dynamic Contour Tonometry (DCT) or Pascal DCT

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5
Q

What is the difference between the “systolic IOP” and the “diastolic IOP” called? 1. What does this indicate? 2

A
  1. ocular pulse amplitude (OPA)

2. higher for glaucoma patients

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6
Q

What are the contributions to variable IOP?

A
  1. peaks and troughs with circadian rhythm

2. supine position

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7
Q

What were the risk factors that were most likely to develop glaucoma found in the OHTS?

A
  1. above 25.75mmHg IOP

2. less than 555um corneal thickness

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8
Q

What are the three measurements that the ocular response analyzer (ORA) provides?

A
  1. difference between measurements (corneal hysteresis)
  2. IOPcc = corneal compensated IOP
  3. IOPg = Goldmann correlated IOP
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9
Q

What is the non-contact tonometer that takes a measurement as the cornea is flattened and as it recovers? 1. What does this measure? 2

A
  1. ocular response analyzer (ORA)

2. corneal hysteresis (tensile strength of cornea)

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10
Q

What is taking multiple IOP readings on the same patient with the same tonometer in a given day called?

A

serial tonometry

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11
Q

What errors lead to an underestimate of IOP for Goldmann readings?

A
  1. mires too thin
  2. repeat measurements
  3. over 3D with the rule cyl
  4. thin cornea
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12
Q

When is the IOP the highest?

A

during sleep

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13
Q

What did the OHTS study show?

A
  1. only 10% of people with IOP 24 to 32 ended up getting glaucoma with no Tx
  2. Tx did help to reduce the risk of developing glaucoma
  3. thinner corneas lead to artificially lower IOP and vice versa
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14
Q

What errors lead to an overestimate of IOP for Goldmann readings?

A
  1. mires too thick
  2. pressure on globe from examiner or blepharospasm
  3. valsalve
  4. superior gaze of over 15deg
  5. over 3D against the rule cyl
  6. thick cornea
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15
Q

What is the equation for the IOP?

A 
IOP = AHP - TMOut - UvScOut + EVP
AHP = aqueous humor production
TMOut = trabecular meshwork outflow
UvScOut = uveoscleral outflow
EVP = episcleral venous pressure
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16
Q

What was the most significant risk factor for an ocular hypertensive patient to convert to glaucoma?

A

reduced CCT

17
Q

What are the three categories of central corneal thickness amounts?

A
  1. normal
  2. thin CCT (less than 530) is significant
  3. thick CCT (more than 590) may be protective
18
Q

What techniques should be used in order to obtain the patients peak IOP?

A
  1. alternate morning and afternoon appointments

2. obtain at least one IOP within 1 to 2 hours of awakening

19
Q

What is the disadvantage of a tonopen?

A

less accurate

20
Q

What has proven to be the key factor resulting in progression of glaucoma?

A

mean IOP

21
Q

How much of a decrease in the rate of progression does each 1mmHg lowering of IOP cause?

A

10% decrease

22
Q

What is the normal central corneal thickness (CCT)?

A

544

23
Q

What are the factors that decrease the hysteresis of an ORA?

A
  1. Age
  2. Fuch’s dystrophy
  3. eye rubbing prior to measure
  4. POAG
  5. ocular pulse amplitude
  6. PSD on VF
24
Q

What are the factors that increase the hysteresis of an ORA?

A

CCT

25
Q

What is the silicone hydrogel lens that contains sensors detecting IOP over 24hrs called?

A

Triggerfish IOP monitoring CL

26
Q

What is the normal CH value for patients while doing the ORA? 1. High CH value? 2

A
  1. 7 or lower

2. 12 or higher

27
Q

What is the baseline physiological IOP that is the lowest it can possibly be (name and number)?

A

episcleral venous pressure (9 to 11mmHg)

III. Glaucoma Management (9 decks)

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