Measurement area and repeatability of semiautomated assessment of corneal endothelium in the Topcon specular microscope SP-2000P and IMAGEnet system.
OBJECTIVE
To investigate the repeatability of the semiautomatic assessment of corneal endothelial cells and its association with the measurement area in the Topcon SP-2000P microscope and IMAGEnet system.


METHODS
Specular microscopic images of 86 healthy subjects were captured and analyzed using the Topcon SP-2000P microscope and IMAGEnet system. The same images were analyzed twice, on separate days, by the same examiner using the built-in measurement tool of the IMAGEnet system. The measurement areas were defined with a frame mounted on a computer screen. Four different-sized measurement areas were chosen for the semiautomatic measurements: box A (5.4 × 13.9 cm(2)), box B (4 × 10 cm(2)), box C (4 × 7 cm(2)), and box D (2 × 5 cm(2)). Average cell size (ACS), endothelial cell density (ECD), coefficient of variance, and hexagonality were measured. Repeatability was assessed based on the limit of agreement (LOA).


RESULTS
The means of ACS, ECD, and hexagonality were not statistically different across 4 measurement areas (analysis of variance, P > 0.05). The mean differences (bias) were modest for ACS (range, -1.9∼3.9 μm(2)), ECD (range, -27.2∼14.6 cells per square millimeter), coefficient of variance (range, -0.14∼1.00), and hexagonality (range, -1.3%∼6.8%). Limits of agreement (mean difference ± 1.96× SD) were greater in the measurements with smaller areas: limit of agreement values for ECD were 14.6 ± 99.6, -3.8 ± 101.1, -27.2 ± 179, and -15.8 ± 488 cells per square millimeter for boxes A, B, C, and D, respectively. Similar trends were found in the repeatability of ACS and hexagonality.


CONCLUSIONS
Repeatability is improved when larger measurement areas are chosen.
State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
Xiaohu
X
Ding
Qunxiao
Q
Huang
Yingfeng
Y
Zheng
Yuzhen
Y
Jiang
Shengsong
S
Huang
Mingguang
M
He
D000368:Aged; D002452:Cell Count; D048430:Cell Shape; D048429:Cell Size; D003941:Diagnostic Techniques, Ophthalmological; D004728:Endothelium, Corneal / Q000166:cytology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008853:Microscopy / Q000295:instrumentation; D008875:Middle Aged; D015203:Reproducibility of Results