| Schlemm's canal, also known as canal of Schlemm or the scleral venous sinus, is a circular channel in the eye that collects aqueous humor from the anterior chamber and delivers it into the bloodstream via the anterior ciliary veins. Both Schlemm's canal basic research and clinical research was a primary focus of ophthalmologists in the past few years. Early investigation on Schlemm's canal was performed with light microscopy or electron microscopy, which limited the application to clinic in vivo. The rapid development of medical imaging technology increased the possibility of evaluating Schlemm's canal in vivo. In 2010, ultrasound biomicroscopy (UBM) and optical coherence tomography were found to be reliable instruments in investigating the Schlemm's canal, which was reported in Ophthalmology and IOVS. As a high resolution, non-contact imaging technique, OCT has become one of the most developed ophthalmic imaging methods.Twenty years had passed since the appearance of OCT. With 20 years updating, the OCT techniques were improved greatly. The appearance of spectral-domain OCT (SD-OCT)is one of the breakthroughs in this field. With the much faster scanning speed and higher resolution, the imaging in vivo becomes more clear and intuitive. In 2008, Asrami firstly found that anterior segment Fourier-domain optical coherence tomography permits detailed noncontact imaging of the angle and its structures, providing a tool to improve our understanding of the pathogenesis of narrow-angle glaucoma. Schlemm's canal and the trabecular meshwork were visualized in all of the patients. Questions arise then:compared with the traditional HE staining, whether the measurement of Schlemm's canal in vivo by SD-OCT is more accurate and reproducible; whether the diameter or the area of Schlemm's canal is the better parameter in investigating Schlemm's canal; whether the diameter and the area of Schlemm's canal is related to the location of Schlemm's canal, intraocular pressure, patients'age and sex; what is the difference of Schlemm's canal among normal subjects, primary open angle glaucoma (POAG) and primary angle closure glaucoma (PACG). Few reports about the above problems has been released.In connection with the above crucial problems in clinic, the current study performed the comparison of imaging and measurement of Schlemm's canal, including the diameter and the area, between HE staining and SD-OCT (RTVue) on normal subjects. In addition, POAG patients and PACG patients were also recruited to evaluate their relationship and difference after the affecting factors on Schlemm's canal measurements by SD-OCT were also studied.Part?Repeatability and Reproducibility of Schlemm's canal Measurements by SD-OCT in Normal SubjectsPurpose[1] To compare the Schlemm's canal measurements of normal subjects by SD-OCT and HE staining, and to explore the parameter suitable for evaluating Schlemm's canal.[2] To characterize the Schlemm's canal under SD-OCT, and to evaluated the repeatability and reproducibility of Schlemm's canal measurements by SD-OCT in normal subjects.Methods[1] RTVue-OCT was used to measure the Schlemm's canal of 126 eyes of 126 normal subjects. One eye of subjects was randomized to this study, the measuring values and the coefficients of variance of the measurements by these two instruments were compared. Line scanning model was used to obtain images of anterior eye segment in four locations in each eye, including superior, inferior, nasal and temporal location. SPSS 16.0 was used for processing the data. Quantitative variables are summarized by mean±standard deviation and range. One-Way ANOVA Bonferroni adjustment was performed to evaluate the difference between four locations; nonparametric Spearman correlation was used to compare the measurement of Schlemm's canal diameter and area. Finally, Schlemm's canal diameter and area in HE slice provided by eye bank was compared with that measured by SD-OCT using Mann-Whitney test.[2] Intraobserver variability (repeatability) was investigated in study arm 1, in which examinations were performed twice by the same examiner with two-day interval. Interobserver variability (reproducibility) was investigated in study arm 2, in which examinations were performed by 2 different examiners with a randomly assigned order of examiners. The coefficient of variation (CV) and the interclass correlation coefficient (ICC) was calculated by SPSS 16.0. Spearman correlation was used to compare the mean and standard error of Schlemm's canal diameter and area.Results[1] The measuring values of Schlemm's canal diameter in four locations were as followed:superior (48.8±7.6)?m, inferior (47.0±10.4)?m, nasal (44.0±12.5)?m and temporal (46.5±13.5)?m, while those of Schlemm's canal area were (15646±3160)?m2, (14185±3604)?m2, (13398±1889)?m2, (14956±2740)?m2, repectively. There were significant differences on the diameter (F=3.396,P=0.008) and area (F=13.941, P=0.000) of Schlemm's canal among four locations. Bonferrioni adjustment revealed significant difference in diameter only between superior and nasal (P=0.004). For area, superior v.s. nasal (P=0.000), superior v.s. inferior (P=0.000) and nasal v.s. temporal (P=0.000) also showed significant difference. The correlation analysis showed no significant relationship between diameter and area in four locations:superior (?=-0.042, P=0.639), inferior (?=0.007, P=0.938), nasal (?=-0.074, P=0.412) and temporal (?=0.098, P=0.274).Based on results above, Schlemm's canal by SD-OCT can not be considered as a whole when compared with HE slice, meaning that all four locations should be analyzed respectively. The diameter and area of HE Schlemm's canal by HE staining were (36.9±18.6)?m and (0.009±0.006) mm2, respectively. There were significant differences on the diameter of Schlemm's canal between each location and HE slice:superior (Z=-1.979, P=0.048), inferior (Z=-1.955, P=0.051), nasal (Z=2.033, P=0.042) and temporal (Z=-2.255, P=0.024). Meanwhile, there were significant differences on the area of Schlemm's canal between each location and HE slice:superior (Z=-3.118, P=0.002), inferior (Z=-2.696, P=0.007), nasal (Z=-2.442, P=0.015) and temporal (Z=-3.019, P=0.003).[2] For intraobserver variability, CV and ICC values in the diameter and the area of superior Schlemm's canal were 5.8% and 0.792,18.5% and 0.589, respectively. CV and ICC values in the diameter and the area of inferior Schlemm's canal were 10.5% and 0.768,8.9% and 0.726, respectively. CV and ICC values in the diameter and the area of nasal Schlemm's canal were 7.1% and 0.786,22.1% and 0.807, respectively. CV and ICC values in the diameter and the area of temporal Schlemm's canal were 7.1% and 0.757,9.5% and 0.507, respectively. For interobserver variability, CV and ICC values in the diameter and the area of superior Schlemm's canal were 7.1% and 0.781,8.0% and 0.705, respectively. CV and ICC values in the diameter and the area of inferior Schlemm's canal were 15% and 0.756,14% and 0.557, respectively. CV and ICC values in the diameter and the area of nasal Schlemm's canal were 16.9% and 0.730,8.0% and 0.788, respectively. CV and ICC values in the diameter and the area of temporal Schlemm's canal were 14.2% and 0.792,21.2% and 0.772, respectively.No significant correlations were found between mean values of the diameter of Schlemm's canal and measurement variability for each participant:?=0.158, P=0.518 (intraobserver variability);?=-0.019, P=0.939 (interobserver variability). Similarly, no significant correlations were found between mean values of the area of Schlemm's canal and measurement variability for each participant:?=0.259, P=0.284 (intraobserver variability);?=0.196, P=0.422 (interobserver variability).Conclusion[1] SD-OCT yields well visualization and accurate definition of Schlemm's canal, which enables the comprehensive and intuitive observation in vivo. The measuring values of the diameter and area of Schlemm's canal were similar to previous report.[2] SD-OCT revealed significant difference among different location in Schlemm's canal, meaning that the effect of locations on the measurement of Schlemm's canal should be noted. Because the correlation analysis showed no significant relationship between diameter and area in four locations, both the diameter and the area are needed in evaluating the Schlemm's canal.[3] A possible reason for the pheromone that both the diameter and the area of Schlemm's canal by SD-OCT were larger than those in HE slice was that samples were shrinked after HE staining.[4] The repeatability and reproducibility of Schlemm's canal measurements by SD-OCT were moderate, indicating SD-OCT was a reliable imaging technique.[5] No significant correlations were found between mean values of the diameter and the area of Schlemm's canal and measurement variability, revealing better results for repeatability and reproducibility.Part?Affecting Factors on Schlemm's canal Measurements by SD-OCT in Normal SubjectsPurpose[1] To explore the possible effect of age and sex on Schlemm's canal measurements. [2] To explore the possible effect of central corneal thickness (CCT) and axial length of eye on Schlemm's canal measurements.[3] To explore the possible effect of cornea-limbus thickness on Schlemm's canal measurements.Methods[1] RTVue-OCT was used to measure the Schlemm's canal of 126 eyes of 126 normal subjects. One eye of subjects was randomized to this study, the measuring values and the coefficients of variance of the measurements by these two instruments were compared. Line scanning model was used to obtain images of anterior eye segment in four locations in each eye, including superior, inferior, nasal and temporal location. Information of subjects was recorded. IOL master was used to measure the axial length.[2] SPSS 16.0 was used for processing the data. Quantitative variables are summarized by mean±standard deviation and range. Mann-Whitney test was performed to evaluate the difference between different sex; nonparametric spearman correlation was used to compare the age and the measurement of Schlemm's canal. Finally, spearman correlation was also used to compare the CCT or axial length and the measurement of Schlemm's canal.[3] Spearman correlation was used to compare the cornea-limbus thickness and the measurement of Schlemm's canalResults[1] The age of 57 male subjects was (36.9±19.6) years, while the age of female subjects was (44.4±20.0) years. The age of total subjects was (41.0±20.1) years. There were significant differences both on the diameter and area of Schlemm's canal between different sexes. For the diameter, statistical values were as followed: superior (Z=-0.950, P-0.342), inferior (Z=-1.319, P=0.187), nasal (Z=-1.835, P=0.067) and temporal (Z=-0.447, P=0.655). Those of Schlemm's canal area were as followed:superior (Z=-0.697, P=0.486), inferior (Z=-1.231, P=0.218), nasal (Z =-0.644, P=0.520) and temporal (Z=-1.810, P=0.070). The correlation analysis showed no significant relationship between age and measurements of diameter and area in four locations. For diameter, statistical values were as followed:superior (?=-0.123, P=0.270), inferior (?=0.098, P=0.275), nasal (?=-0.025, P=0.780) and temporal (?=0.030, P=0.741). For, area, statistical values were as followed:superior (?=0.021, P=0.812), inferior (?=0.044, P=0.625), nasal (?=-0.094, P=0.296) and temporal (?=-0.076, P=0.399).[2] The CCT of 126 subjects was (554.7±38.7)?m. The axial length was (23.7±2.1) mm.The correlation analysis showed no significant relationship between CCT and measurements of diameter and area in four locations. For the diameter, statistical values were as followed:superior (?=-0.099, P=0.269), inferior (?=-0.043, P=0.631), nasal (?=-0.048, P=0.592) and temporal (?=-0.017, P=0.854). Those of Schlemm's canal area were as followed:superior (?=0.037, P=0.683), inferior (?=0.035, P=0.700), nasal (?=0.068, P=0.449) and temporal (?=0.129, P=0.151).The correlation analysis showed no significant relationship between axial length and measurements of diameter and area in four locations. For diameter, statistical values were as followed:superior (?=-0.138, P=0.123), inferior (?=0.063, P=0.483), nasal (?=0.075, P=0.402) and temporal (?=0.137, P=0.125). For, area, statistical values were as followed:superior (?=-0.047, P=0.602), inferior (?=-0.042, P=0.643), nasal (?=-0.122, P=0.175) and temporal (?=0.060, P=0.506).[3] The cornea-limbus thickness of 126 subjects was (844.9±41.9) mm, ranging from 744.7mm to 962.7mm. The correlation analysis showed no significant relationship between cornea-limbus thickness and measurements of diameter and area in four locations. For the diameter, statistical values were as followed:superior (?=0.007, P=0.939), inferior (?=-0.023, P=0.798), nasal (?=0.030, P=0.741) and temporal (?=0.133, P=0.139). Those of Schlemm's canal area were as followed:superior (?=0.017, P=0.849), inferior (?=-0.007, P=0.942), nasal (?=0.102, P=0.255) and temporal (?=0.160,P=0.073).Conclusion[1] SD-OCT revealed no significant difference in Schlemm's canal measurements among different sex and age, meaning that the effect of age and sex on the measurement of Schlemm's canal could be ignored.[2] No significant correlations were found between values of CCT and axial length and Schlemm's canal measurements, revealing the effect of them on the measurement of Schlemm's canal could be ignored.[3] Although no significant correlations were found between values of cornea-limbus thickness and Schlemm's canal measurements, its thickness could be used as quality controlling factor. In currents study, the cornea-limbus thickness in which clear SD-OCT images were obtained was about 845 mm.Part?Schlemm's canal Measurements by SD-OCT in POAG patientsPurpose[1] To explore the Schlemm's canal measurements of POAG patients by SD-OCT.[2] To compare the Schlemm's canal measurements of normal subjects and POAG patients. [3] To explore the possible relationship of intraocular pressure (IOP) and Schlemm's canal measurements, and to explore the diagnostic value of its measurements on POAG by SD-OCT.Methods[1] RTVue-OCT was used to measure the Schlemm's canal of 43 eyes of 43 POAG patients.43 eyes of 43 age-matched and sex-matched normal subjects were also recruited. One eye of subjects was randomized to this study. the measuring values and the coefficients of variance of the measurements by these two instruments were compared. Line scanning model was used to obtain images of anterior eye segment in four locations in each eye, including superior, inferior, nasal and temporal location. SPSS 16.0 was used for processing the data. Quantitative variables are summarized by mean±standard deviation and range. Axial length, CCT, IOP and Schlemm's canal diameter and area in POAG patients were compared with that in normal subjects using Mann-Whitney test.[2] Nonparametric Spearman correlation was used to compare the measurement of Schlemm's canal and IOP.[3] The area under the ROC curve were calculated to study the diagnostic values of Schlemm's canal measurements on POAG patients.Results[1] The age of 43 POAG patients was (42.6±14.1) years, including 29 male subjects and 14 female subjects. The measuring values of Schlemm's canal diameter in four locations were as followed:superior (43.6±11.6)?m, inferior (36.0±8.8)?m, nasal (41.1±11.6)?m and temporal (41.1±7.0)?m, while those of Schlemm's canal area were (12907±2662)?m2, (11347±4221)?m2, (10765±514)?m2, (11800±3110)?m2, repectively. The axial length, CCT and IOP of 43 POAG patients were (23.1±0.6) mm, (539.6±25.9)?m, (30.0±4.9) mmHg, respectively. Statistical values were as followed:axial length (Z=-0.374,P=0.709), CCT (Z=-1.632, P=0.103), IOP (Z=-5.835, P=0.000). There were significant differences only in IOP measurement between two groups. There were no significant differences on the diameter of Schlemm's canal between two groups. Statistical values were as followed:superior (Z=-1.887, P=0.059), inferior (Z=-1.205, P=0.228), nasal (Z=-1.212, P=0.226) and temporal (Z=-0.465, P=0.642). However, there were significant differences on the area of Schlemm's canal between two groups. Statistical values were as followed:superior (Z=-3.077, P=0.002), inferior (Z=-2.984, P=0.003), nasal (Z =-5.346, P=0.000) and temporal (Z=-3.351, P=0.001). Finally, no significant differences were found on the corneal-limbus thickness between two groups. Statistical values were as followed:superior (Z=-0.281, P=0.778), inferior (Z =-1.583, P=0.113), nasal (Z=-1.415, P=0.157) and temporal (Z=-0.466, P=0.641).[2] No significant correlations were found between mean values of the diameter of Schlemm's canal and IOP for POAG patients and normal subjects:superior (?=-0.135, P=0.361), inferior(?=-0.230, P=0.116), nasal (?=-0.107, P=0.469) and temporal (?=-0.038, P=0.798). However, correlations were significant between mean values of the area of Schlemm's canal and IOP:superior (?=-0.514, P=0.000), inferior (?=-0.497, P=0.000), nasal (?=-0.745, P=0.000) and temporal (?=-0.486, P=0.000).[3] On the diagnosis of POAG, the areas under ROC curves of the diameter of Schlemm's canal were as followed:0.658 (superior location),0.600 (inferior location),0.602 (nasal location) and 0.462 (temporal location). In addition, the areas under ROC curves of the area of Schlemm's canal were as followed:0.757 (superior location),0.750 (inferior location),0.946 (nasal location) and 0.781 (temporal location)Conclusion[1] SD-OCT yields well visualization and accurate definition of Schlemm's canal in POAG patients, which enables the comprehensive and intuitive observation.[2] SD-OCT revealed no significant difference in the diameter of Schlemm's canal between POAG patients and normal subjects. However, significant difference in the area of Schlemm's canal between POAG patients and normal subjects was detected. The correlation analysis showed significant relationship between IOP and the area of Schlemm's canal. The exact role of Schlemm's canal changes in the pathological process of POAG needs further investigation.[3] The diagnostic value of the area of Schlemm's canal in POAG was better than that of the diameter.Part?Schlemm's canal Measurements by SD-OCT in PACG patientsPurpose[1] To explore the Schlemm's canal measurements of PACG patients by SD-OCT.[2] To compare the Schlemm's canal measurements of normal subjects and PACG patients.[3] To explore the possible relationship of intraocular pressure (IOP) and Schlemm's canal measurements, and to explore the diagnostic value of its measurements on PACG by SD-OCT.Methods[1] RTVue-OCT was used to measure the Schlemm's canal of 41 eyes of 41 PACG patients.41 eyes of 41 age-matched and sex-matched normal subjects were also recruited. One eye of subjects was randomized to this study, the measuring values and the coefficients of variance of the measurements by these two instruments were compared. Line scanning model was used to obtain images of anterior eye segment in four locations in each eye, including superior, inferior, nasal and temporal location. SPSS 16.0 was used for processing the data. Quantitative variables are summarized by mean±standard deviation and range. Axial length, CCT, IOP and Schlemm's canal diameter and area in PACG patients were compared with that in normal subjects using Mann-Whitney test.[2] Nonparametric Spearman correlation was used to compare the measurement of Schlemm's canal and IOP.[3] The area under the ROC curve were calculated to study the diagnostic values of Schlemm's canal measurements on PACG patients.Results[1] The age of 41 PACG patients was (62.9±10.0) years, including 21 male subjects and 20 female subjects. The measuring values of Schlemm's canal diameter in four locations were as followed:superior (54.2±12.6)?m, inferior (51.0±7.8)?m, nasal (42.9±14.3)?m and temporal (47.0±16.4)?m, while those of Schlemm's canal area were (15222±2462)?m2, (14648±1798)?m2, (14555±1937)?m2, (15741±2392)?m2, repectively. The axial length, CCT and IOP of 41 PACG patients were (23.0±0.6) mm, (550.8±30.6)?m, (30.2±8.4) mmHg, respectively. Statistical values were as followed:axial length (Z=-3.106, P=0.002), CCT (Z=-0.981, P=0.326), IOP (Z=-4.717, P=0.000). There were significant differences in axial length and IOP measurement between two groups. There were no significant differences on the diameter of Schlemm's canal between two groups. Statistical values were as followed:superior (Z=-1.841, P=0.066), inferior (Z=-0.177, P=0.859), nasal (Z =-1.651, P=0.099) and temporal (Z=-1.717, P=0.086). However, comparison results of the area of Schlemm's canal between two groups were various. Statistical values were as followed:superior (Z=-1.021, P=0.307), inferior (Z=-1.468, P=0.142), nasal (Z=-1.992, P=0.046) and temporal (Z=-2.262, P=0.024). Finally, no significant differences were found on the corneal-limbus thickness between two groups. Statistical values were as followed:superior (Z=-0.638, P=0.524), inferior (Z=-0.702, P=0.483), nasal (Z=-0.128, P=0.898) and temporal (Z=-0.714, P=0.475).[2] No significant correlations were found between mean values of the diameter of Schlemm's canal and IOP for PACG patients and normal subjects:superior (?=0.207, P=0.226), inferior (?=-0.042, P=0.809), nasal (?=-0.258, P=0.128) and temporal (?=-0.210, P=0.219). However, correlations was various between mean values of the area of Schlemm's canal and IOP:superior (?=-0.108, P=0.531), inferior (?=0.088, P=0.610), nasal (?=0.370, P=0.026) and temporal (?=0.274, P=0.105).[3] On the diagnosis of PACG, the areas under ROC curves of the diameter of Schlemm's canal were as followed:0.321 (superior location),0.483 (inferior location),0.660 (nasal location) and 0.667 (temporal location). In addition, the areas under ROC curves of the area of Schlemm's canal were as followed:0.599 (superior location),0.358 (inferior location),0.309 (nasal location) and 0.282 (temporal location)Conclusion[1] SD-OCT yields well visualization and accurate definition of Schlemm's canal in PACG patients, which enables the comprehensive and intuitive observation.[2] SD-OCT revealed no significant difference in the diameter of Schlemm's canal between PACG patients and normal subjects. However, significant difference in the area of nasal and temporal Schlemm's canal between PACG patients and normal subjects was detected. The correlation analysis showed only significant relationship between IOP and the area of Schlemm's canal in nasal location. The exact role of Schlemm's canal changes in the pathological process of PACG needs further investigation.[3] The diagnostic value of the diameter and area of Schlemm's canal in PACG was low. Further researches were warranted to address this issue. |
PDF Full Text Request