1. Factors Affecting ORA Parameter and Comparing with NCT in Normal Korean
Jun Her MD. PhD, Sung-wook Kim MD, Jae-hwan Ahn MD
Inje University, College of Medicine, Busan Paik Hospital,
Busan, South Korea
We have NO financial interest

2. Purpose
To identify normal range of factors which can be measured with Ocular Response Analyzer(ORA, Depew, NY, USA) in normal Korean, and to analyze factors affecting ORA by measuring intraocular pressure of noncontact tonometer (NCT) and central corneal thickness (CCT).

3. Methods
Three hundred and one normal Korean subjects who did not have special ophthalmological diseases and surgeries in the past were recruited for this study.

4. Methods
Corneal hysteresis(CH), corneal response factor(CRF), corneal compensated IOP(IOPcc), Goldman related IOP(IOPg) were measured using ORA and the results and factors were analyzed.
The results were divided into a juveniles group(n=57) and to adult group over age 20 (n=244) and compared.

5. Methods
Principle of ocular response analyzer (ORA)

6. Results Table 1. Normal ranges of ORA Parameters in Korean Parameter
Race
N. Of Eye
Ave ± St dev mmHg
Range mmHg CH
Korean
301
10.70 ± 1.45
7.5 ~ 15.8
American1
246
11.19 ± 1.63
7.24 ~ 15.8
CRF
10.40 ± 1.61
6.5 ~ 15.9
10.46 ± 1.75
5.37 ~ 15.74
IOPcc
14.90 ± 2.50
9.2 ~ 21.7
IOPg
14.61 ± 2.70
8.3 ~ 21.7
CCT
± 34.13
470 ~ 658
1 : David Luce, David Taylor. Reichert Ocular Response Analyzer Measures Corneal Biomechanical Properties and IOP. Provides New Indicators for Corneal Specialties and Glaucoma Management.

7. Results “ CH and CRF were significantly higher in juvenile group ”
Table 2. Comparision of ORA parameters between Juvenile group and Adult group
Juvenile
(≤19 years)
Adult(>19 years)
IOPcc
15.52
14.76
IOPg
15.78
14.35
CRF
11.06
10.25 CH
10.62
NCT
15.44
14.00
P<0.05

8. Results “ No significant difference from male and female ”
Table 3. Comparision of ORA parameters between Female group and Male group
Female
Male
IOPcc
14.78
14.98
IOPg
14.52
14.68
CRF
10.39
10.41 CH
10.73
10.68
CCT
541.83
543.55
NCT
14.1
14.38

9. Results Table 3. Statistical correlations between parameters. Age
IOPcc
IOPg
CRF CH
CCT
NCT
0.79
-0.42
0.50
0.67
0.22
0.13
0.73
0.87
0.30
0.58
0.28
0.32
The red squares indicate significance with a high level of correlation.
The blue squares indicate significance with a moderate correlation.
Strong
Moderate

10. Summary Among normal Koreans
- CH : mean 10.7 ±1.45 mmHg, distribution 7.5~15.8 mmHg.
- CRF : mean ±1.61 mmHg, distribution 6.5~15.9 mmHg
Juvenile vs Adult
- CH and CRF were significantly higher in juvenile group.
Statistical correlations between parameters
- Positive correlation was found between CCT & NCT and CH & CRF
(but the magnitude was weak (P<0.01))
- IOPcc and IOPg (as measures of IOP in ORA) had significamt
correlation with IOP of NCT
- In particular IOPcc appeared to be independent of corneal thickness

11. Conclusions(1)
Mean CH among normal Koreans were lower than those of Americans (P<0.01), indicating racial differences.
CH and CRF were significantly higher in the juvenile group, indicating difference in biomechanical properties of eye ball due to age.
IOPcc and IOPg measured in ORA have significant clinical correlation with IOP of NCT.
In particular, IOPcc will become more important as it is independent of corneal thickness which should be compensation in general measurement of IOP and reflects biomechanical properties.

12. Conclusions(2)
Futher investigation should be advised to determine whether IOPcc as tonometer being independent of corneal thickness and incorporating new concept of biomechanics would be more useful than IOP of NCT.