| Purpose: 1. To find the most sensitive indicators in screening the subclinical keratoconus of Pentacam and Corvis ST. 2. To compare the differences of three instruments, Corvis ST,Pentacam and the Topcon non-contact tonometer. 3. To detect the differences of corneal biomechanics between Mongolian and Han.Methods: 1. Select 40 people(40 eyes) in the control group and 20 patients(20 eyes) in the subclinical keratoconus group, Pentacam and Corvis ST inspections are performed. Maximum anterior corneal power at central 6.0 mm(Max P6A), maximum posterior corneal power at central 6.0 mm(Max P6P), maximum anterior corneal elevation above the BFS at central 6mm(Max AE6), maximum posterior corneal elevation above the BFS at central 6mm(Max PE6) of Pentacam and the first applanation time(1AT),the second applanation time(2AT), the first applanation length(1AL),the second applanation length(2AL),the first applanation velocity(Vin),the second applanation velocity(Vout),time from the start until the highest concavity(HC time),deformation amplitude(DA) and the central curvature radius at highest concavity(HC radius) of Corvis ST are chosen to compared between the two groups by independent samples t-test, P<0.05 was considered statistically significant. Draw ROC curve, calculate the area under the curve of each index, and to find the most sensitive indicators of Pentacam and Corvis ST, compare the sensitive of the two instruments in screening subclinical keratoconus. 2. 60 patients(120 eyes) with refractive in Inner Mongolia are selected, and were performed Corvis ST, Pentacam and Topcon tonometer examination.The central corneal thickness(CCT) between Corvis ST and Pentacam and the intraocular pressure(IOP) between Corvis ST and Topcon tonometer are compared, and in the same time,the corneal biomechanics parameters between Mongolia and Han are compared. All the parameters are analyzed by paired t test, SPSS 13.0. P<0.05 was considered statistically significant.Result: 1. The differences of the four indicators measured by Pentacam are all statistically significant between the control group and the subclinical keratoconus group(P<0.05), and 1AT,2AT, 2AL, Hc radius, DA of Corvis ST are statistically significant(P<0.05). Compare the area under the ROC curve of these parameters, we can find that Max P6 A, Max P6 P, Max AE6,Max PE6 of Pentacam and 2AT, DA are sensitive parameters in screening subclinical keratoconus. 2. The mean CCT measured by Corvis ST and Pentacam are 533.33 ± 36.18 and545.52 ± 33.80, and the difference was statistically significant(P<0.05). The mean IOP measured by Corvis ST and Topcon tonometer are 13.62±2.99 and 15.77±2.80 respectively,the difference was statistically significant(P<0.05). 3. There was no significant difference of the contrast of corneal biomechanical parameters between Mongolia and Han(P>0.05).Conclusion: 1. MaxP6 A, MaxP6 P, MaxAE6, MaxPE6 of Pentacam have significant differences between the control group and the subclinical keratoconus group, they were closely related to the development of keratoconus. 1AT, 2AT, 2AL, DA, HC radius of Corvis ST have differences between the control group and the subclinical keratoconus group, and2 AT and DA have the most significant differences, but they are less sensitive than the parameters of Pentacam, so, Pentacam is still an important method of screening and diagnosis in subclinical keratoconus. 2. Compared with Pentacam and Topcon tonometer, the Corvis ST was a different instrument, and the measurement results can not replace each other. 3. The corneal biomechanical parameters had no significant difference between Mongolia and Han. |
