ABSTRACT
AIM: To investigate the difference, correlation, and consistency of corneal thickness and the thinnest point position detected by Pentacam HR corneal topography map and RTVue optical coherence tomography(OCT)in patients with keratoconus.METHODS: Cross-sectional comparative study. The corneal curvature map, corneal thickness map, thinnest point position, and thinnest point thickness were detected by Pentacam HR and RTVue OCT. Paired sample t-test was used for data consistent with normal distribution, and paired sample rank sum test was used for data inconsistent with normal distribution. Spearman correlation analysis and Bland-Altman analysis were used for the correlation and consistency of the two measurement methods.RESULTS: A total of 63 patients(105 eyes)with keratoconus were included in this study, including 49 males(77.8%)and 14 females(22.2%), aged 22.24±6.19 years; among them, relevant data of Pentacam HR topographic map: Km was 47.85±4.73D and Kmax was 55.43±8.72D. In measuring central corneal thickness and the thinnest point thickness of keratoconus, the Pentacam HR was 4.70μm and 19.46μm thicker than the mean value measured by RTVue OCT(P<0.05). There was no significant difference between the horizontal and vertical coordinates of the thinnest points measured by the two devices(P>0.05). The central corneal thickness and the thinnest point thickness measured by the two devices were highly correlated, the horizontal coordinate of the thinnest point was moderately correlated, and the vertical coordinate of the thinnest point was weakly correlated. Bland-Altman analysis showed that the central corneal thickness, the thinnest point thickness, the horizontal coordinate of the thinnest point, and the vertical coordinate of the thinnest point were 95.2%(100/105)and 93.3%(98/105), 95.2%(100/105), 95.2%(100/105)respectively, which were within the 95% consistency limit, while the consistency ranges were -36.00～+26.62μm, -42.27～+3.36μm, -0.80～+0.84mm, and -1.95～+1.06mm, respectively.CONCLUSION: In keratoconus, the central corneal thickness and the thinnest point thickness measured by Pentacam HR were higher than those measured by RTVue OCT. It is not recommended that the central corneal thickness and the thinnest point thickness measured by the two instruments be interchangeable in clinical use because of the wide range of consistency between the two instruments' results. The position of the thinnest corneal point measured by the two instruments is similar and consistent, so it could be considered to replace the measured values of the two instruments in clinical use.
ABSTRACT
Background Many studies showed that attenuation of retinal nerve fiber layer(RNFL)in early glaucoma is one of the important signs.How to accurately and quantitatively measure RNFL thickness is very important for the early diagnosis and monitoring of glaucoma.0bjective This study was to evaluate the clinical value of Optovue RTVue OCT and Heidelberg Retina Tomograph Ⅲ(HRT-Ⅲ)confocal scanning laser ophthalmoscopy in glaucomatous eyes. Methods This cross-sectional study included 40 eyes of 26 patients with suspected open-angle glaucoma(SOAG),48 eyes of 29 patients with open-angle glaucoma and 48 eyes of 27 healthy subjects.Optical nerve head(ONH) parameters and peripapillary RNFL thickness were measured in all the subjects with Optovue RTVue OCT and HRT-Ⅲ,meanwhile all the eyes received perimetry with Humphrey 750-I.Glaucoma variables obtained from Optovue RTVue OCT and HRT-Ⅲ were analyzed among the groups.Topographic Optovue RTVue OCT and HRT-Ⅲ parameters,including disc area(DA),cup area(CA),rim area(RA),rim volume(RV),cup volume(CV),cup/disc area ratio(C/DAR)as well as superior,temporal,inferior and nasal average RNFL thickness,were analyzed.The relationship of ONH parameters and RNFL thickness was analyzed using a linear correlation.The correlation between the mean defect(MD)of the visual field and the tomography parameters in glaucomatous eyes was described by bivariate Pearson correlation coefficients.Resuits The ONH parameters and RNFL thickness obtained by HRT-Ⅲ and OCT showed significant difference(P<0.05).ONH parameters such as RA,C/DAR,CA and RV were statistically changed in SOAG and the POAG patients compared with the normal subjects(q=6.47,q=7.67,P<0.05).The superior and inferior RNFL thickness parameters in three groups were positively correlated between HRT-Ⅲand OCT(r=0.362,r=0.441,r=0.395,P<0.05),Topographic Optovue RTVue OCT and HRT-Ⅲ parameters including CV,CA,RA and C/DAR fitted Pearson analysis(all P<0.05).In POAG group。The RA,RV,CV,C/DAR from Optovue RTVue OCT were correlated with MD with the significant coefficient 0.284,0.286,0.340,0.371 respectively(P<0.05),and evidently correlations also were found between RA,RV,C/DAR with MD respectively with the coefficient 0.339,0.859,0.422(P<0.05)by HRT-Ⅲ. Conclusion Both Optovue RTVue OCT and HRT-Ⅲ can difierentiate ONH analysis with a similar outcome in glaucomatous eye.The C/D value.RA,superior and inferior RNFL thickness based on Optovue RTVue OCT and HRT-Ⅲare distinguishing indexes in the diagnosis of early glaucomatous damage.