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Abstract
Purpose
To compare the anterior segment parameters including precorneal tear film thickness (PTFT) using Pentacam®(Oculus, Wetzlar, Germany) between normal control and dry eye groups and to examine the relationships between the PTFT and other parameters for dry eye.
Methods
The present study included 23 normal controls (31 eyes) and 25 patients with dry eyes (31 eyes). We compared meas-urements including PTFT, corneal thickness and astigmatism using Pentacam® and analyzed the correlations among the PTFT and fluorescein tear break-up time (FBUT), Schirmer I test (without anesthesia), and ocular surface disease index (OSDI).
Results
The mean PTFT in dry eyes (21.1 ± 2.0 μ m) was significantly thinner than in normal eyes (37.6 ± 2.0 μ m; p < 0.01). In the dry eye group, the corneal thickness was thicker than in the normal eye group but there were no clinically significant differences. The dry eye group experienced more frequent and severe corneal astigmatism compared with the normal group. OSDI scores showed a weak negative correlation with objective clinical measures of dry eye (FBUT, Schirmer I test) but was not statistically significant. However, OSDI was statistically significantly negatively correlated with PTFT (r = -0.46, p < 0.01). The PTFT showed a weak positive correlation with FBUT and Schirmer I test without statistical significance.
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Figure 1.
Precorneal tear film thickness can be measured by Scheimpflug imaging. (A) The scheimpflug images before and after the fluorescein staining. Note the high-bright visualized tear film (white arrow) and the different optical density of ocular interface (white circle) after fluorescein instillation. (B) Compare 2 image view. The central thickness in the dif-ference A-B section means the thickness of precorneal tear film (black arrow). Only the data presented quality of speciality (black circle) was “OK” were included. We also evaluated the thickness of tear film on temporal, superior, nasal, and in-ferior side and corneal reflective power.
Figure 2.
The relationship between PTFT and corneal astig-matism. PTFT = precorneal tear film thickness; D = diopter; r = Pearson’s correlation coefficient. * p-value by pearson’s correlation analysis.
Figure 3.
The relationship among FBUT, Schirmer I test and OSDI. FBUT = fluorescein break-up time; OSDI = ocular surface disease index; r = Pearson’s correlation coefficient. * p-value by Pearson’s correlation analysis.
Figure 4.
The relationship between the PTFT and parameters for dry eye (FBUT, Schirmer I and OSDI). PTFT = pre-corneal tear film thickness; FBUT = fluorescein break-up time; OSDI = ocular surface disease index; r = Pearson’s cor-relation coefficient. * p-value by Pearson’s correlation analysis.
Table 1.
The comparison of the corneal thickness and TFT between normal group and dry eye group
| Normal group (n = 31) | Dry eye group (n = 31) | p-value* | |
|---|---|---|---|
| Age (years) | 32.8 ± 9.3 | 49.5 ± 15.0 | <0.01 |
| Sex (No. of female, %) | 27 (87.1) | 28 (90.3) | 0.32‡ |
| Corneal spherical power (D) | 43.7 ± 1.0 | 43.8 ± 1.3 | 0.7 |
| Corneal astigmatism (D) | 1.0 ± 0.6 | 1.2 ± 0.5 | 0.3 |
| CCT (μ m) | 548.6 ± 4.4 | 549.4 ± 4.4 | 0.01† |
| Central TFT (μ m) | 37.6 ± 2.0 | 21.1 ± 2.0 | <0.01† |
Table 2.
The thickness of the localized tear film and the comparison of the distribution of the thickest area between normal and dry eye group
| Normal group | Dry eye group | p-value* | |
|---|---|---|---|
| Area | |||
| Superior (μ m) | 38.7 ± 18.3 | 28.1 ± 17.2 | 0.03 |
| Inferior (μ m) | 29.6 ± 18.4 | 20.3 ± 17.9 | 0.07 |
| Nasal (μ m) | 29.7 ± 13.1 | 25.2 ± 14.9 | 0.24 |
| Temporal (μ m) | 34.4 ± 16.5 | 21.1 ± 16.6 | <0.01 |
| Central (μ m) | 35.5 ± 10.0 | 23.2 ± 11.2 | <0.01 |
| Distribution of the thickest area | |||
| Superior (n, %) | 18 (58) | 13 (42) | |
| Inferior (n, %) | 9 (29) | 4 (13) | |
| Nasal (n, %) | 1 (3) | 8 (26) | 0.03† |
| Temporal (n, %) | 3 (10) | 3 (10) | |
| Central (n, %) | 0 (0) | 3 (10) | |
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