- Email: [email protected]
cell meter measurements of intraocular inflammation
Reproducibility and validity of laser flare/cell meter measurements of intraocular inflammation Akef EI-Maghraby, M.D., Adnan Marzouki, M.D., Tirupatur Mohammed Matheen, M.D., Julianne Souchek, Ph.D., Michelle Van Der Karr
ABSTRACT Preoperative and postoperative anterior chamber reactions in a series of cataract surgery patients were measured with a Kowa FC-1 000 laser flare/cell meter by two different technicians, and clinical assessments of inflammation were recorded. The average cell and flare readings by the two technicians were nearly identical at every time pOint, showing the laser flare/cell measurements to be highly reproducible. The correlations between laser flare/cell measurements and clinical assessments at postoperative time pOints were highly positive (P < .01), demonstrating the validity of the laser flare/cell measurements. Key Words: inflammation, laser flare/cell meter
The most widely used measure of inflammation has been clinical gradings of flare and cells obtained by slitlamp examination. However, clinical assessments are relatively insensitive as measures ofinflammation. They are also subjective, and thus vary widely among examiners. Techniques of assessing anterior chamber inflammation and breakdown of the blood aqueous barrier using slitlamp fluorophotometry have been suggested. 1,2 Following oral administration of fluorescein sodium, fluorophotometry has shown a discernible difference in fluorescein leakage. 2 - 4 However, fluorescein leakage and actual inflammation are only indirectly correlated, and thus not accepted by the United States Food and Drug Administration as a measure of inflammation. Research in topical nonsteroidal anti-inflammatory drugs for postoperative ocular inflammation, and studies of new surface-modified intraocular lenses, require more sensitive, reliable, noninvasive, and objective methods of assessing inflammation. The Kowa Instrument Corporation in Japan has developed a machine using laser technology to measure flare and cells quantitatively.5 Early clinical work with endogenous uveitis patients in Japan by Ohara et al. 6 has demonstrated a linear correlation between slitlamp gradings and aqueous flare measured by the meter. Similarly, those authors found a correlation (though nonlinear)
between the laser aqueous cell measurement and the slitlamp grade. 6 Other investigators have reported the laser flare/cell meter to provide more sensitive measurements of inflammation than slitlamp gradings. 7 ,8 Most published papers study patients with uveitis and other serious inflammatory diseases, and not the routine postoperative cataract surgical case. We recently acquired a Kowa FC-lOOO laser flare/cell meter and have begun a study to test the reproducibility of the laser flare/cell measurements between technicians and the validity of the measurements relative to clinical assessments of inflammation in patients having cataract extraction and posterior chamber lens implantation.
MATERIALS AND METHODS Patients were eligible for enrollment in the study if they were scheduled to have or had had uncomplicated primary cataract surgery by phacoemulsification. Patients with preoperative evidence of uveitis or any previous corneal or anterior chamber inflammatory disease were not eligible. On specified study days, all eligible patients presenting at the clinic for preoperative visits or for one to three day or one to three week postoperative examinations were enrolled.
From El-Maghraby Hospital, Saudi Arabia (El-Maghraby, Marzouki, Matheen), and the Center for Clinical Research, Department of Ophthalmology, University of Illinois at Chicago (Souchek, Van Der Karr). Analysis of the data was performed by the Center for Clinical Research. Reprint requests to Akef El-Maghraby, M.D., El-Maghraby Hospital, Post Office Box 7344, Jeddah, Saudi Arabia 21462. 52
J CATARACT REFRACT SURG-VOL 19, JANUARY 1993
300
EaUIVALENT READINGS
250
T E C
200
1
100
H
Fig. 1.
150
PEARSON CORRELATION COEFFICIENT
.. :
50
"
0.97
(El-Maghraby) Scatterplot of laser flare readings (photon countj msec) taken by the first technician versus those taken by the second technician on the same patients on the same day. All patients presented one to three days postoperatively.
0.001 50
100
150
200
250
300
TECH 2
Laser flare/cell meter measurements of flare and cells were performed by two different technicians on the same patient on the same day. The technicians followed a uniform protocol so neither was aware of the previous measurements. Clinical assessments of flare and cells were made with the highest intensity slit beam on the slitlamp and the smallest aperture, an illumination angle of 30 to 45 degrees and 16x magnification. Values were obtained during five seconds of measurement under standardized dim room illumination. The following ordinal grades were used: For flare, a grade of 0 for no flare, 1 for trace flare, 2 for mild intensity, 3 for moderate intensity, and 4 for strong intensity. For cells, a grade of 0 for no cells, 1 for 1 to 5 cells, 2 for 6 to 15 cells, 3 for 16 to 30 cells, and 4 for more than 30 cells. Clinical assessments were made on patients who presented for postoperative visits. To prevent bias, the physician making the clinical assessments did not see the laser flare/cell measurements. Reproducibility of the laser flare/cell measurements was evaluated by comparing measurements made consecutively by the two technicians. Validity was first evaluated by examining the mean laser flare and cell 120
Eighty-five cases were enrolled. Twenty-five of the patients were measured preoperatively, 45 were measured one to three days after surgery, and 15 were measured one to three weeks after surgery. Sixty-eight percent were male, 32% were female, and the average age was 57.7 years. Figures 1 and 2 plot the two technicians' laser flare and cell readings for cases at one to three days postoperative. Most points fall on or close to the equivalency line, indicating good repeatability from one technician to the next. The Pearson correlation coefficients were very high, 0.96 for cells and 0.97 for flare (P< .001). The mean cell counts and flare measurements are shown in Table 1. The average cell and flare readings of the two technicians were nearly identical at every time point, indicating good reproducibility.
Fig. 2.
80
C
60
1
40
H
RESULTS
EaUIVALENT READINGS
100
T E
measurements at each time point and then by examining the correlation between clinical assessments of inflammation and the laser flare/cell measurements. Cases were stratified by the clinical grading of flare or cells.
:
"
PEARSON CORRELATION COEFFICIENT
""
....
20
0.96
(EI-Maghraby) Scatterplot oflaser cell readings (peak particle countjO.075 mm 3) taken by the first technician versus those taken by the second technician on the same patients on the same day. All patients presented one to three days postoperatively.
peO.OOl O~--L-~--~--~--~---L--~--~--~--~--~~
o
10
20
30
40
50
60
70
80
90
100
110
120
TECH 2 J CATARACT REFRACT SURG-VOL 19, JANUARY 1993
53
Table 1. Mean laser flare and cell measurements by technician.
Flare/Cells
Number of Patients
Flare* Preop 1-3 days postop 1-3 weeks postop Cellst Preop 1-3 days postop 1-3 weeks postop * Photon count/msec t Peak count/0.075 mm3
Laser Measurements (Mean [SEM]) Tech I Tech 2
25 45 15
1.0 (0.3) 52.3 (6.3) 15.0 (3.7)
0.7 (0.2) 53.3 (5.6) 14.5 (3.7)
25 45 15
1.4 (0.6) 31.0 (3.5) 4.7 (1.6)
1.4 (0.8) 31.8 (3.6) 4.7 (1.6)
Figure 3 shows the mean laser flare and cell measurements preoperatively, one to three days and one to three weeks postoperatively. The measurements reflect the expected time course of postoperative inflammation, with low measurements for cases measured preoperatively and at one to three weeks postoperatively and higher measurements for cases measured one to three days postoperatively. The mean laser flare and cell measurements for each clinical flare and cell score are shown in Table 2. The preoperative cases did not have clinical scores greater than 0, so cases at one to three days and one to three weeks postoperative are presented. The correlations between the laser flare/cell measurements and the clinical
scores were significantly positive, with higher clinical grades associated with higher laser flare/cell measurements.
DISCUSSION In our clinical setting, the measurements of flare and cells using the laser flare/cell meter were highly reproducible, with nearly identical readings from two different technicians. The readings were also well correlated with ordinally graded clinical assessments of flare and cells, indicating that the technology validly measures clinical inflammation. The mean laser flare measurements at one to three days were very similar for cases graded at 2 flare and at 3 flare (79.3 and 82.5, respectively; see Table 2). The FC-I000 laser machine has shown linear correlations between photon counts and protein concentration up to 3,000 mg/dl (Ogawa T, Ohara K, Shimizu H, unpublished observation), making it unlikely that the relationship is nonlinear. The fact that the laser machine did not appear to discriminate between aqueous flare grades of 2 and 3+ may reflect a lack of discrimination in clinical assessments at high levels of flare. Our results compare favorably with a similar study presented by Gimbel et al. ("Objective Assessment of Inflammation: Laser Flare/Cell Meter," American Academy of Ophthalmology meeting, 1990), in which the authors found a significant correlation between laser cell readings and clinical assessments of anterior chamber cells. In general, we found higher correlations between laser measurements of flare and cells and clinical assessments of flare and cells, perhaps because we saw higher overall levels of inflammation
Table 2. Mean laser flare and cell postoperative measurements by clinical grade. Postoperative Time Clinical Score 1-3 Days Cells 0-1; 2 3 0-1§ Flare 2 3 1-3 Weeks 0 Cells 1-211 0 Flare
N
Mean Laser Measurement Mean SEM* S.D·t
P-Value
0.81
<.001
0.74
<.001
10
13.5 36.9 53.8 28.3 79.3 82.5
2.6 6.6 3.9 4.8 14.0 5.2
11.7 22.7 14.0 23.1 46.5 16.6
8 6 5 9
1.0 9.3 0.8 22.4
0.3 3.2 0.5 4.2
0.8 7.8
0.62
<.01
1.1
0.83
<.001
20 12 13 24 11
12.7
* Standard error of the mean. t Standard deviation. Only one patient had a clinical grade of o. § Two patients had a clinical grade of o. I Only one patient had a clinical grade of 2.
*
54
Spearman Correlation
J CATARACf REFRACf SURG-VOL 19, JANUARY 1993
52.8
FLARE CELL ,/
1.4
SEMo.69
PREOP n-25
I' 1-3 DAYS n-45
n-15
Fig. 3. (EI-Maghraby) Mean aqueous flare (photon count/msec) and cell count (peak particle count/O.075 mm 3 ) measured by the laser flare/cell meter in samples of patients preoperatively and at 1-3 days and 1-3 weeks postoperatively. Standard errors of the means (SEM) are indicated.
which could have made differentiation among clinical scores easier and masked any low level noise picked up by the laser. REFERENCES 1. Sanders DR, KraffMC, Lieberman HL, et al. Breakdown and reestablishment of blood-aqueous barrier with implant surgery. Arch Ophthalmol 1982; 100:588-590 2. Sanders DR, Kraff M. Steroidal and nonsteroidal antiinflammatory agents; effect on postsurgical inflammation and blood-aqueous humor barrier breakdown. Arch Ophthalmoll984; 102:1453-1456 3. Flach AJ, Kraff Me, Sanders DR, Tanenbaum L. The quantitative effect of 0.5% ketorolac tromethamine solution and 0.1 % dexamethasone sodium phosphate solution on postsurgical blood-aqueous barrier. Arch Ophthalmol 1988; 106:480-483
4. Araie M, Sawa M, Takase M. Topical flurbiprofen and diclofenac suppress blood-aqueous barrier breakdown in cataract surgery: a fluorophotometric study. Jpn J Ophthalmol 1983; 27:535-542 5. Sawa M, Tsurimaki Y, Tsuru T, Shimizu H. New quantitative method to determine protein concentration and cell number in aqueous in vivo. Jpn J Ophthalmoll988; 32:132-142 6. Ohara K, Okubo A, Miyazawa A, et al. Aqueous flare and cell measurement using laser in endogenous uveitis patients. Jpn J Ophthalmol 1989; 33:265-270 7. Oshika T, Araie M, Masuda K. Diurnal variation of aqueous flare in normal human eyes measured with laser flarecell meter. Jpn J Ophthalmol 1988; 32:143-150 8. Oshika T, Nishi M, Mochizuki M, et al. Quantitative assessment of aqueous flare and cells in uveitis. Jpn J Ophthalmol 1989; 33:279-287
J CATARACT REFRACTSURG-VOL 19, JANUARY 1993
55
ABSTRACT Preoperative and postoperative anterior chamber reactions in a series of cataract surgery patients were measured with a Kowa FC-1 000 laser flare/cell meter by two different technicians, and clinical assessments of inflammation were recorded. The average cell and flare readings by the two technicians were nearly identical at every time pOint, showing the laser flare/cell measurements to be highly reproducible. The correlations between laser flare/cell measurements and clinical assessments at postoperative time pOints were highly positive (P < .01), demonstrating the validity of the laser flare/cell measurements. Key Words: inflammation, laser flare/cell meter
The most widely used measure of inflammation has been clinical gradings of flare and cells obtained by slitlamp examination. However, clinical assessments are relatively insensitive as measures ofinflammation. They are also subjective, and thus vary widely among examiners. Techniques of assessing anterior chamber inflammation and breakdown of the blood aqueous barrier using slitlamp fluorophotometry have been suggested. 1,2 Following oral administration of fluorescein sodium, fluorophotometry has shown a discernible difference in fluorescein leakage. 2 - 4 However, fluorescein leakage and actual inflammation are only indirectly correlated, and thus not accepted by the United States Food and Drug Administration as a measure of inflammation. Research in topical nonsteroidal anti-inflammatory drugs for postoperative ocular inflammation, and studies of new surface-modified intraocular lenses, require more sensitive, reliable, noninvasive, and objective methods of assessing inflammation. The Kowa Instrument Corporation in Japan has developed a machine using laser technology to measure flare and cells quantitatively.5 Early clinical work with endogenous uveitis patients in Japan by Ohara et al. 6 has demonstrated a linear correlation between slitlamp gradings and aqueous flare measured by the meter. Similarly, those authors found a correlation (though nonlinear)
between the laser aqueous cell measurement and the slitlamp grade. 6 Other investigators have reported the laser flare/cell meter to provide more sensitive measurements of inflammation than slitlamp gradings. 7 ,8 Most published papers study patients with uveitis and other serious inflammatory diseases, and not the routine postoperative cataract surgical case. We recently acquired a Kowa FC-lOOO laser flare/cell meter and have begun a study to test the reproducibility of the laser flare/cell measurements between technicians and the validity of the measurements relative to clinical assessments of inflammation in patients having cataract extraction and posterior chamber lens implantation.
MATERIALS AND METHODS Patients were eligible for enrollment in the study if they were scheduled to have or had had uncomplicated primary cataract surgery by phacoemulsification. Patients with preoperative evidence of uveitis or any previous corneal or anterior chamber inflammatory disease were not eligible. On specified study days, all eligible patients presenting at the clinic for preoperative visits or for one to three day or one to three week postoperative examinations were enrolled.
From El-Maghraby Hospital, Saudi Arabia (El-Maghraby, Marzouki, Matheen), and the Center for Clinical Research, Department of Ophthalmology, University of Illinois at Chicago (Souchek, Van Der Karr). Analysis of the data was performed by the Center for Clinical Research. Reprint requests to Akef El-Maghraby, M.D., El-Maghraby Hospital, Post Office Box 7344, Jeddah, Saudi Arabia 21462. 52
J CATARACT REFRACT SURG-VOL 19, JANUARY 1993
300
EaUIVALENT READINGS
250
T E C
200
1
100
H
Fig. 1.
150
PEARSON CORRELATION COEFFICIENT
.. :
50
"
0.97
(El-Maghraby) Scatterplot of laser flare readings (photon countj msec) taken by the first technician versus those taken by the second technician on the same patients on the same day. All patients presented one to three days postoperatively.
0.001 50
100
150
200
250
300
TECH 2
Laser flare/cell meter measurements of flare and cells were performed by two different technicians on the same patient on the same day. The technicians followed a uniform protocol so neither was aware of the previous measurements. Clinical assessments of flare and cells were made with the highest intensity slit beam on the slitlamp and the smallest aperture, an illumination angle of 30 to 45 degrees and 16x magnification. Values were obtained during five seconds of measurement under standardized dim room illumination. The following ordinal grades were used: For flare, a grade of 0 for no flare, 1 for trace flare, 2 for mild intensity, 3 for moderate intensity, and 4 for strong intensity. For cells, a grade of 0 for no cells, 1 for 1 to 5 cells, 2 for 6 to 15 cells, 3 for 16 to 30 cells, and 4 for more than 30 cells. Clinical assessments were made on patients who presented for postoperative visits. To prevent bias, the physician making the clinical assessments did not see the laser flare/cell measurements. Reproducibility of the laser flare/cell measurements was evaluated by comparing measurements made consecutively by the two technicians. Validity was first evaluated by examining the mean laser flare and cell 120
Eighty-five cases were enrolled. Twenty-five of the patients were measured preoperatively, 45 were measured one to three days after surgery, and 15 were measured one to three weeks after surgery. Sixty-eight percent were male, 32% were female, and the average age was 57.7 years. Figures 1 and 2 plot the two technicians' laser flare and cell readings for cases at one to three days postoperative. Most points fall on or close to the equivalency line, indicating good repeatability from one technician to the next. The Pearson correlation coefficients were very high, 0.96 for cells and 0.97 for flare (P< .001). The mean cell counts and flare measurements are shown in Table 1. The average cell and flare readings of the two technicians were nearly identical at every time point, indicating good reproducibility.
Fig. 2.
80
C
60
1
40
H
RESULTS
EaUIVALENT READINGS
100
T E
measurements at each time point and then by examining the correlation between clinical assessments of inflammation and the laser flare/cell measurements. Cases were stratified by the clinical grading of flare or cells.
:
"
PEARSON CORRELATION COEFFICIENT
""
....
20
0.96
(EI-Maghraby) Scatterplot oflaser cell readings (peak particle countjO.075 mm 3) taken by the first technician versus those taken by the second technician on the same patients on the same day. All patients presented one to three days postoperatively.
peO.OOl O~--L-~--~--~--~---L--~--~--~--~--~~
o
10
20
30
40
50
60
70
80
90
100
110
120
TECH 2 J CATARACT REFRACT SURG-VOL 19, JANUARY 1993
53
Table 1. Mean laser flare and cell measurements by technician.
Flare/Cells
Number of Patients
Flare* Preop 1-3 days postop 1-3 weeks postop Cellst Preop 1-3 days postop 1-3 weeks postop * Photon count/msec t Peak count/0.075 mm3
Laser Measurements (Mean [SEM]) Tech I Tech 2
25 45 15
1.0 (0.3) 52.3 (6.3) 15.0 (3.7)
0.7 (0.2) 53.3 (5.6) 14.5 (3.7)
25 45 15
1.4 (0.6) 31.0 (3.5) 4.7 (1.6)
1.4 (0.8) 31.8 (3.6) 4.7 (1.6)
Figure 3 shows the mean laser flare and cell measurements preoperatively, one to three days and one to three weeks postoperatively. The measurements reflect the expected time course of postoperative inflammation, with low measurements for cases measured preoperatively and at one to three weeks postoperatively and higher measurements for cases measured one to three days postoperatively. The mean laser flare and cell measurements for each clinical flare and cell score are shown in Table 2. The preoperative cases did not have clinical scores greater than 0, so cases at one to three days and one to three weeks postoperative are presented. The correlations between the laser flare/cell measurements and the clinical
scores were significantly positive, with higher clinical grades associated with higher laser flare/cell measurements.
DISCUSSION In our clinical setting, the measurements of flare and cells using the laser flare/cell meter were highly reproducible, with nearly identical readings from two different technicians. The readings were also well correlated with ordinally graded clinical assessments of flare and cells, indicating that the technology validly measures clinical inflammation. The mean laser flare measurements at one to three days were very similar for cases graded at 2 flare and at 3 flare (79.3 and 82.5, respectively; see Table 2). The FC-I000 laser machine has shown linear correlations between photon counts and protein concentration up to 3,000 mg/dl (Ogawa T, Ohara K, Shimizu H, unpublished observation), making it unlikely that the relationship is nonlinear. The fact that the laser machine did not appear to discriminate between aqueous flare grades of 2 and 3+ may reflect a lack of discrimination in clinical assessments at high levels of flare. Our results compare favorably with a similar study presented by Gimbel et al. ("Objective Assessment of Inflammation: Laser Flare/Cell Meter," American Academy of Ophthalmology meeting, 1990), in which the authors found a significant correlation between laser cell readings and clinical assessments of anterior chamber cells. In general, we found higher correlations between laser measurements of flare and cells and clinical assessments of flare and cells, perhaps because we saw higher overall levels of inflammation
Table 2. Mean laser flare and cell postoperative measurements by clinical grade. Postoperative Time Clinical Score 1-3 Days Cells 0-1; 2 3 0-1§ Flare 2 3 1-3 Weeks 0 Cells 1-211 0 Flare
N
Mean Laser Measurement Mean SEM* S.D·t
P-Value
0.81
<.001
0.74
<.001
10
13.5 36.9 53.8 28.3 79.3 82.5
2.6 6.6 3.9 4.8 14.0 5.2
11.7 22.7 14.0 23.1 46.5 16.6
8 6 5 9
1.0 9.3 0.8 22.4
0.3 3.2 0.5 4.2
0.8 7.8
0.62
<.01
1.1
0.83
<.001
20 12 13 24 11
12.7
* Standard error of the mean. t Standard deviation. Only one patient had a clinical grade of o. § Two patients had a clinical grade of o. I Only one patient had a clinical grade of 2.
*
54
Spearman Correlation
J CATARACf REFRACf SURG-VOL 19, JANUARY 1993
52.8
FLARE CELL ,/
1.4
SEMo.69
PREOP n-25
I' 1-3 DAYS n-45
n-15
Fig. 3. (EI-Maghraby) Mean aqueous flare (photon count/msec) and cell count (peak particle count/O.075 mm 3 ) measured by the laser flare/cell meter in samples of patients preoperatively and at 1-3 days and 1-3 weeks postoperatively. Standard errors of the means (SEM) are indicated.
which could have made differentiation among clinical scores easier and masked any low level noise picked up by the laser. REFERENCES 1. Sanders DR, KraffMC, Lieberman HL, et al. Breakdown and reestablishment of blood-aqueous barrier with implant surgery. Arch Ophthalmol 1982; 100:588-590 2. Sanders DR, Kraff M. Steroidal and nonsteroidal antiinflammatory agents; effect on postsurgical inflammation and blood-aqueous humor barrier breakdown. Arch Ophthalmoll984; 102:1453-1456 3. Flach AJ, Kraff Me, Sanders DR, Tanenbaum L. The quantitative effect of 0.5% ketorolac tromethamine solution and 0.1 % dexamethasone sodium phosphate solution on postsurgical blood-aqueous barrier. Arch Ophthalmol 1988; 106:480-483
4. Araie M, Sawa M, Takase M. Topical flurbiprofen and diclofenac suppress blood-aqueous barrier breakdown in cataract surgery: a fluorophotometric study. Jpn J Ophthalmol 1983; 27:535-542 5. Sawa M, Tsurimaki Y, Tsuru T, Shimizu H. New quantitative method to determine protein concentration and cell number in aqueous in vivo. Jpn J Ophthalmoll988; 32:132-142 6. Ohara K, Okubo A, Miyazawa A, et al. Aqueous flare and cell measurement using laser in endogenous uveitis patients. Jpn J Ophthalmol 1989; 33:265-270 7. Oshika T, Araie M, Masuda K. Diurnal variation of aqueous flare in normal human eyes measured with laser flarecell meter. Jpn J Ophthalmol 1988; 32:143-150 8. Oshika T, Nishi M, Mochizuki M, et al. Quantitative assessment of aqueous flare and cells in uveitis. Jpn J Ophthalmol 1989; 33:279-287
J CATARACT REFRACTSURG-VOL 19, JANUARY 1993
55