CORNEAL HYSTERESIS MEASURED WITH OCULAR RESPONSE ANALYZER IN GLAUCOMATOUS, HYPERTENSIVE AND NORMAL EYES.

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CORNEAL HYSTERESIS MEASURED WITH OCULAR RESPONSE
ANALYZER IN GLAUCOMATOUS, HYPERTENSIVE AND NORMAL
EYES.

• Olivia ABITBOL (1,2), Jihene BOUDEN (1,2), Serge
  DOAN (1,2), Thanh HOANG-XUAN (1,2), Damien
  GATINEL (1,2)
• Fondation Rothschild (1), Hôpital Bichat-Claude
  Bernard (2), Paris, FRANCE.

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Financial Disclosures

• None

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PURPOSE

• To identify differences in corneal hysteresis
  (CH) and central corneal thickness (CCT) between
  healthy, glaucomatous patients, and patients with
  ocular hypertension (OHT).

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METHODS

• Retrospective observational study
• We measured the CH (ORA) and ultrasonic CCT in
  318 eyes of 161 patients.
• Patients were divided in three groups normal,
  OHT and glaucomatous.
• For each patient, one eye was randomly selected.
• We used a Student test to search for significant
  differences between the different groups
  (plt0.05).

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RESULTS demographic variables of patients
Number of eyes 161 Age (years)
Normal 75 61.4 (45-85)
OHT 20 56.0 (23-82)
Glaucoma 66 64.3 (37-93)

• No statistically significant age difference
  between normal and glaucoma patients (p0.11)
• Nor between normal and OHT patients (p0.07).
• Age difference between OHT and glaucoma
  subjects statistically significant (p0.015)

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RESULTS mean values of CCT and CH for the
different groups
CCT (µm) CCT (µm) CH (mm Hg) CH (mm Hg)
mean SD Min-maxi mean SD Min-maxi
Normal 560.2 36.3 483-657 10.4 1.6 7.1-14.9
OHT 560.7 40.4 512-646 10.1 1.6 6.5-13.8
Glaucoma 537.4 42.3 435-654 8.7 1.5 4.3-12.6
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RESULTS mean CH values in different groups
CH
(mm Hg)
OHT
Glaucoma
normal
plt0,05
plt0,05
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RESULTS

• Mean CH and CCT were significantly lower in
  glaucomatous group than in normal and OHT groups.
  
• However, the difference between the normal and
  OHT groups was not significant.

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DISCUSSION

• Our results are in agreement with Congdon et
  al.s report, who postulated that as a thin CCT,
  a low CH could be an independent risk factor for
  glaucoma evolution.1 Several hypotheses can be
  made to explain these results
• First, IOP is under-estimated in patients with
  thin pachymetry.2 Similarly, a low CH value, (i.e
  softer cornea), could be responsible for
  under-estimation of IOP when measured with the
  Goldmann aplanation tonometer.
• Second, it is possible that CCT and CH each
  correspond to risk factors for glaucoma,
  independent of IOP. Eyes with lower CH and/or
  thinner CCT than normal could indicate structural
  weakness.
• Finally, as it is responsible for the optic
  nerve heads lesions, chronic ocular hypertension
  could also be responsible for alterations in
  corneal structure, with subsequent reduction of
  the CH and CCT.

1. Congdon NG, Broman AT, Bandeen-Roche K, Grover
D, Quigley HA. Central corneal thickness and
corneal hysteresis associated with glaucoma
damage. Am J Ophthalmol 2006141868-75.
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CONCLUSION

• In our series, CH was lower in glaucomatous eyes
  than in OHT and normal eyes.
• Like CCT, CH could become an important clinical
  marker for glaucoma diagnosis and management.