Evaluation of retinal and choroidal thickness changes in overweight and obese adults without ocular symptoms by swept-source optical coherence tomography

AIM:To evaluate the relationship of overweight and obesity with retinal and choroidal thickness in adults without ocular symptoms by swept-source optical coherence tomography(SS-OCT).METHODS:According to the body mass index(BMI)results,the adults enrolled in the cross-sectional study were divided into the normal group(18.50≤BMI<25.00 kg/m^(2)),the overweight group(25.00≤BMI<30.00 kg/m^(2)),and the obesity group(BMI≥30.00 kg/m^(2)).The one-way ANOVA and the Chi-square test were used for comparisons.Pearson’s correlation analysis was used to evaluate the relationships between the measured variables.RESULTS:This research covered the left eyes of 3 groups of 434 age-and sex-matched subjects each:normal,overweight,and obesity.The mean BMI was 22.20±1.67,26.82±1.38,and 32.21±2.35 kg/m^(2) in normal,overweight and obesity groups,respectively.The choroid was significantly thinner in both the overweight and obesity groups compared to the normal group(P<0.05 for all),while the retinal thickness of the three groups did not differ significantly.Pearson’s correlation analysis showed that BMI was significantly negatively correlated with choroidal thickness,but no significant correlation was observed between BMI and retinal thickness.CONCLUSION:Choroidal thickness is decreased in people with overweight or obesity.Research on changes in choroidal thickness contributes to the understanding of the mechanisms of certain ocular disorders in overweight and obese adults.

Three-dimensional choroidal vascularity index and choroidal thickness in fellow eyes of acute and chronic primary angle-closure using swept-source optical coherence tomography

AIM:To compare the three-dimensional choroidal vascularity index(CVI)and choroidal thickness between fellow eyes of acute primary angle-closure(F-APAC)and chronic primary angle-closure glaucoma(F-CPACG)and the eyes of normal controls.METHODS:This study included 37 patients with unilateral APAC,37 with asymmetric CPACG without prior treatment,and 36 healthy participants.Using swept-source optical coherence tomography(SS-OCT),the macular and peripapillary choroidal thickness and three-dimensional CVI were measured and compared globally and sectorally.Pearson’s correlation analysis and multivariate regression models were used to evaluate choroidal thickness or CVI with related factors.RESULTS:The mean subfoveal CVIs were 0.35±0.10,0.33±0.09,and 0.29±0.04,and the mean subfoveal choroidal thickness were 315.62±52.92,306.22±59.29,and 262.69±45.55μm in the F-APAC,F-CPACG,and normal groups,respectively.All macular sectors showed significantly higher CVIs and choroidal thickness in the F-APAC and F-CPACG eyes than in the normal eyes(P<0.05),while there were no significant differences between the F-APAC and F-CPACG eyes.In the peripapillary region,the mean overall CVIs were 0.21±0.08,0.20±0.08,and 0.19±0.05,and the mean overall choroidal thickness were 180.45±54.18,174.82±50.67,and 176.18±37.94μm in the F-APAC,F-CPACG,and normal groups,respectively.There were no significant differences between any of the two groups in all peripapillary sectors.Younger age,shorter axial length,and the F-APAC or F-CPACG diagnosis were significantly associated with higher subfoveal CVI and thicker subfoveal choroidal thickness(P<0.05).CONCLUSION:The fellow eyes of unilateral APAC or asymmetric CPACG have higher macular CVI and choroidal thickness than those of the normal controls.Neither CVI nor choroidal thickness can distinguish between eyes predisposed to APAC or CPACG.A thicker choroid with a higher vascular volume may play a role in the pathogenesis of primary angle-closure glaucoma.

Comparison of choroidal thickness in high myopic eyes after FS-LASIK versus implantable collamer lens implantation with swept-source optical coherence tomography

AIM:To investigate the changes in choroidal thickness(CT)in high myopic eyes after femtosecond laser-assisted in situ keratomileusis(FS-LASIK)surgery or central hole implantable collamer lens(ICL V4c)implantation using swept-source optical coherence tomography(SS-OCT).METHODS:We examined the right eyes of 116 patients with high myopia who were candidates for FS-LASIK surgery and ICL implantation.Sixty eyes underwent ICL V4c implantation and 56 eyes were subjected to FS-LASIK surgery.The CT was measured with SS-OCT.All data were recorded preoperatively and 2 h,1 wk,1 and 3 mo postoperatively.Other demographic information was collected,including age,sex,uncorrected visual acuity(UCVA),best corrected visual acuity(BCVA),spherical equivalent(SE),intraocular pressure(IOP)and axial length(AL).RESULTS:The UCVA improved in both groups and showed no significant differences between groups.There also were no significant differences between the two groups in postoperative BCVA and SE(P=0.581 and 0.203,respectively).The foveal CTs,inner nasal and outer nasal CTs were significantly thicker at 2 h postoperatively in both groups(P<0.05)but returned to baseline levels in 1 wk;after 1 mo,no significant differences were found relative to the preoperative values.At 3 mo in each group,nine regions showed variations in the CT as compared with preoperative thickening,but only the foveal and nasal area CTs preoperative differences were statistically significant(P<0.05).In addition,there was no significant difference in 9 regions of CT between the two groups at all follow-up times(P>0.05).CONCLUSION:The CTs after ICL implantation and FSLASIK surgery are significantly thicker than those before operation,especially in the foveal and nasal areas,but there is no significant difference between the two methods.

Renal function and choroidal thickness using swept-source optical coherence tomography in diabetic patients

AIM: To assess the relationship between choroidal thickness and renal function in diabetic patients. METHODS: Cross-sectional retrospective clinical study of 42 eyes of 21 ocular treatment-na?ve diabetic patients. Demographic data included: age, sex, type and course of diabetes. Ocular data included: severity of diabetic retinopathy;retinal thickness at the central macular region, as well as choroidal thickness at the central and paracentral quadrants, using automatically generated maps by swept-source optical coherence tomography;presence of cystic macular edema;and ocular axial length(AXL). Lab-test parameters included: glycated hemoglobin(HbA1c), albuminuria, albumin/creatinine ratio in urine, and glomerular filtration rate. RESULTS: A significant negative correlation was mainly observed between several choroidal thicknesses, age(P<0.020) and ocular AXL(P<0.030). On the contrary, a significant positive correlation was found between all choroidal thicknesses, HbA1 c(P<0.035) and albuminuria(P<0.040). CONCLUSION: Choroidal thickness can represent an additional tool to help clinicians predicting the renal status in ocular treatment-na?ve diabetic patients.

DEVELOPMENT OF HIGH-SPEED SWEPT-SOURCE OPTICAL COHERENCE TOMOGRAPHY SYSTEM AT 1320 nm

A swept-source optical coherence tomography(SSOCT)system based on a high-speed scanning laser source at center wavelength of 1320 nm and scanning rate of 20 kHz is developed.The axial resolution is enhanced to 8.3μm by reshaping the spectrum in frequency domain using a window function and a wave number calibration method based on a Mach-Zender Interferometer(MZI)integrated in the SSOCT system.The imaging speed and depth range are 0.04 s per frame and 3.9 mm,respectively.The peak sensitivity of the SSOCT system is calibrated to be 112 dB.With the developed SSOCT system,optical coherence tomography(OCT)images of human finger tissue are obtained which enable us to view the sweat duct(SD),stratum corneum(SC)and epidermis(ED),demonstrating the feasibility of the SSOCT system for in vivo biomedical imaging.

WAVELENGTH PROBING OPTICAL COHERENCE TOMOGRAPHY

In swept-source optical coherence tomography(SSOCT),the swept-source stimulates system by a series of wavelengths in time sequence;a photo detector then collects all reflected/backscattered light from testing sample as the components of Fourier series.Due to the nature of the SSOCT,the processing in spectral domain can merge multiple swept-sources with different central wavelengths,which greatly increases the resolution of the OCT imaging.In the wavelength probing OCT,a standard broadband SSOCT system is used to extract the internal structure of the sample,and another narrow band light can be used to probe the spectral feature of the sample at the probing wavelength.

High-Speed Optical Coherence Tomography System Using a 200-kHz Swept Light Source with a KTN Deflector

We demonstrate a high-speed swept-source optical coherence tomography (SS-OCT) system, which is based on a high-speed swept light source and a Mach-Zehnder interferometer with a high-speed photodetector. The light source is an external-cavity laser tuned by a KTN electro-optic deflector, which exhibits a very fast response and large deflection. The scanning wavelength range is almost 80 nm up to 200 kHz with a ±400-V deflector driving voltage. The system acquires 1 mm × 1 mm images consisting of 200 × 200 pixels within few milliseconds. We present preliminary SS-OCT images of an in-vitro human nail and an in-vivo finger pad.

Comparison of ocular biometric parameters between two swept-source optical coherence tomography devices and Scheimpflug tomography in patients with cataract

AIM:To assess and compare the variations and agreements across different ocular biometric parameters using swept-source optical coherence tomography(SS-OCT)and Scheimpflug tomography in patients diagnosed with cataract.METHODS:This prospective case series was conducted at Tianjin Medical University Eye Hospital.In total,212 eyes from 212 patients scheduled for phacoemulsification were included.Eyes were evaluated preoperatively using two SSOCT devices(IOLMaster700 and CASIA2)and Scheimpflug tomography(Pentacam).Central corneal thickness(CCT),anterior chamber depth(ACD),aqueous depth(AQD),white-to-white distance(WTW),flat simulated keratometry(Kf),steep simulated keratometry(Ks),mean keratometry(Km),and total corneal keratometry(TKm)were measured.Intraclass correlation coefficient(ICC),95%confidence intervals(CI)and limits of agreement(LoA)widths were conducted to assess differences and correlations between devices.RESULTS:All parameters,except for Ks,were significantly different.Pairwise comparison revealed no significant differences between keratometry obtained by IOLMaster 700 and Pentacam.LoA widths of all paired comparisons for Ks were>0.80 D.Except for WTW between IOLMaster 700 and CASIA2 and between CASIA2 and Pentacam,other Pearson’s coefficients between devices showed a strong correlation(all r>0.95).The ICC of WTW(ICC=0.438,95%CI 0.167-0.625)showed poor reliability.The reliability of CCT,ACD,and AQD was excellent(all ICC>0.95),whereas that of TKm was good(ICC=0.827,95%CI 0.221-0.939).A significant linear correlation was also observed among devices.CONCLUSION:The ocular parameters derived from the use of IOLMaster700,CASIA2,and Pentacam exhibit significant discrepancies;as such,measurements from these devices should not be deemed as interchangeable.

Advances in swept-source optical coherence tomography and optical coherence tomography angiography

Background:The fast development of swept-source optical coherence tomography(SS-OCT)and swept-source optical coherence tomography angiography(SS-OCTA)enables both anterior and posterior imaging of the eye.These techniques have evolved from a research tool to an essential clinical imaging modality.Main text:The longer wavelength and faster speed of SS-OCT and SS-OCTA facilitate better visualization of structure and vasculature below pigmented tissue with a larger field of view of the posterior segment and 360-degree visualization of the anterior segment.In the past 10 years,algorithms dealing with OCT and OCTA data also vastly improved the image quality and enabled the automated quantification of OCT-and OCTA-derived metrics.This technology has enriched our current understanding of healthy and diseased eyes.Even though the high cost of the systems currently limited the widespread use of SS-OCT and SS-OCTA at the first beginning,the gap between research and clinic practice got obviously shortened in the past few years.Conclusions:SS-OCT and SS-OCTA will continue to evolve rapidly,contributing to a paradigm shift toward more widespread adoption of new imaging technology in clinical practice.

Measurement of crystalline lens tilt in high myopic eyes before cataract surgery using swept-source optical coherence tomography

Background:To measure the crystalline lens tilt in eyes with various degrees of myopia before cataract surgery using swept-source optical coherence tomography(SS-OCT).Methods:We used SS-OCT(IOLMaster 700)to scan 131 emmetropic eyes(axial length<24.5 mm),25 mild/moderate myopic eyes(axial length 24.5–26 mm),and 123 high myopic eyes(52,29,and 42 eyes with axial lengths of 26–28,28–30,and>30 mm,respectively)as part of the routine preoperative examination before cataract surgery.SS-OCT involved B-scans along six meridians.The data were analyzed to assess the magnitude and orientation of the lens tilt and their correlation with other optical biometric parameters.Result:The mean tilt was 3.36±0.98°in emmetropic eyes,3.07±1.04°in mild/medium myopic eyes,and 2.35±1.01°in high myopic eyes.Tilt correlated significantly and inversely with axial length(Pearson’s r=−0.427,P<0.001).The crystalline lens tilt predominantly faced the upper outer quadrant relative to the visual axis,symmetrically in both eyes,with mean angles of 24.32°and 147.36°in the right and left eyes,respectively.The variability in the lens tilt direction increased with increasing axial length(χ^(2) test,P<0.001).Conclusion:The magnitude of crystalline lens tilt decreased with increasing axial length.The direction of tilt was predominantly towards the upper outer quadrant in both eyes.The variability in the tilt orientation increased with increasing axial length.Trial registration:NIH(clinicaltrial.gov),NCT03062085.Registered 23 February 2017.

Angle-to-angle and spur-to-spur distance analysis with high-resolution optical coherence tomography

Background:To measure angle-to-angle(ATA)and spur-to-spur(STS)distances along six meridians using highresolution swept-source optical coherence tomography(SS-OCT)and to compare those values with horizontal white-to-white(WTW)distance.Methods:Sixty-eight eyes from 68 patients were quantitatively assessed with the Anterion SS-OCT(Heidelberg Engineering,Heidelberg,Germany).ATA and STS distances were measured with the SS-OCT B-scan in six cross-sectional images corresponding to the vertical(6-12 o'clock),1-7 o'clock,2-8 o'clock,horizontal(3-9 o'clock),4-10 o'clock and 5-11 o'clock meridians.WTW was measured horizontally with the device's infrared camera.A Pearson correlation analysis was carried out to compare ATA and STS distances with WTW.Results:The largest values were found for the vertical meridian and the shortest for the 2-8 o'clock meridian,both for ATA and STS distances.No statistically significant differences were found between WTW,ATA and STS along the horizontal meridian(P>0.1).However,ATA and STS showed statistically significant differences elsewhere,except for the horizontal and the 2-8 o'clock meridians(P>0.05).Moreover,we found that ATA and STS varied significantly depending on the meridian being assessed,except for ATA at 4-10 versus 3-9 o'clock and for STS at 4-10 versus 3-9 o'clock and at 3-9 versus 2-8 o'clock(P>0.1).R2 values ranged from 0.49 to 0.75 for ATA and STS at the different meridians,showing the best correlation at 3-9 o'clock meridian(0.64 and 0.75,respectively)and the worst at 6-12 o'clock meridian(R2=0.49 for both ATA and STS).Conclusions:ATA and STS distances vary radially,thus showing that the anterior chamber is vertically oval.Therefore,it is advisable to measure these two distances along the meridian to be used.

Measurement of crystalline lens tilt in high myopic eyes before cataract surgery using swept-source optical coherence tomography

Background:To measure the crystalline lens tilt in eyes with various degrees of myopia before cataract surgery using swept-source optical coherence tomography(SS-OCT).Methods:We used SS-OCT(lOLMaster 700)to scan 131 emmetropic eyes(axial length<24.5 mm);25 mild/moderate myopic eyes(axial length 24.5-26 mm),and 123 high myopic eyes(52,29,and 42 eyes with axial lengths of 26-28,28-BO,and>30 mm,respectively)as part of the routine preoperative examination before cataract surgery.SS-OCT involved B-scans along six meridians.The data were analyzed to assess the magnitude and orientation of the lens tilt and their correlation with other optical biometric parameters.Result:The mean tilt was 3.36±0.98。in emmetropic eyes,3.07±1.04° in mild/medium myopic eyes,and 2.35±1.01° in high myopic eyes.Tilt correlated significantly and inversely with axial length(Pearson,sr=-0.427,P<0.001).The crystalline lens tilt predominantly faced the upper outer quadrant relative to the visual axis,symmetrically in both eyes,with mean angles of 24.32°and 147.36°in the right and left eyes,respectively.The variability in the lens tilt direction increased with increasing axial length(x2 test,P<0.001).Conclusion:The magnitude of crystalline lens tilt decreased with increasing axial length.The direction of tilt was predominantly towards the upper outer quadrant in both eyes.The variability in the tilt orientation increased with increasing axial length.Trial registration:NIH(clinicaltrial.gov),NCT03062085.Registered 23 February 2017.

新型SS-OCT与Scheimpflug眼前节分析仪测量年龄相关性白内障患者角膜屈光力及散光的一致性

目的:探讨年龄相关性白内障患者应用新型扫频源光学相干断层扫描仪(SS-OCT)与Scheimpflug眼前节分析仪测量角膜屈光力、角膜散光的Bland-Altman分析。方法:选取2021-01/12我院收治的年龄相关性白内障患者177例282眼。分别采用SS-OCT与Scheimpflug眼前节分析仪测量角膜前表面、后表面、全角膜的陡峭轴屈光力(Ks)、平坦轴屈光力(Kf)、平均角膜屈光力(Km)、角膜散光、散光轴向。所有参数进行配对样本t检验、组内重复性检验、Pearson相关性和Bland-Altman一致性分析。结果:SS-OCT与Scheimpflug眼前节分析仪测量的角膜前表面屈光力Ks、Kf、Km均无差异(P>0.05)。Scheimpflug眼前节分析仪测量的角膜后表面以及全角膜屈光力Ks、Kf、Km均大于SS-OCT测量值(P<0.05)。SS-OCT与Scheimpflug眼前节分析仪测量的角膜前表面、角膜后表面以及全角膜的散光度数和轴向均无差异(P>0.05)。所有参数的组内相关系数(ICC)均大于0.88,提示组内重复性较好。SS-OCT与Scheimpflug眼前节分析仪测量的角膜前表面、角膜后表面以及全角膜的Ks、Kf、Km、散光度数和轴向均呈正相关(P<0.05)。Bland-Altman一致性分析显示,SS-OCT与Scheimpflug眼前节分析仪测量的角膜前表面、角膜后表面以及全角膜的Ks、Kf、Km、散光度数和轴向的一致性较好(P<0.05)。结论:新型SS-OCT与Scheimpflug眼前节分析仪测量的角膜屈光力、角膜散光参数具有高度一致性,可适用于年龄相关性白内障患者角膜屈光力及角膜散光的诊断。

Agreement of corneal curvature and central corneal thickness obtained from a swept-source OCT and Pentacam in ectopia lentis patients

AIM:To assess the inter-device consistency of corneal curvature and central corneal thickness between Pentacam and a swept-source Fourier-domain anterior segment optical coherence tomography(AS-OCT)in ectopia lentis patients.METHODS:Totally 72 eyes of ectopia lentis patients were recruited.Central corneal thickness(CCT),corneal curvature values and corneal astigmatism were obtained from both the Pentacam and AS-OCT(CASIA2).Repeatability was evaluated for both devices.The coef ficient of repeatability(COR)and the relative COR was calculated.Bland-Altman plots were conducted to evaluate the interdevice agreement of measurement.Orthogonal linear regression was used to examine any proportional bias.RESULTS:The mean difference of CCT,steep anterior corneal cur vature(anterior K_S),flat anterior corneal curvature(anterior K_f),anterior corneal astigmatism(ACA),steep posterior corneal cur vature(posterior K_S),flat posterior corneal cur vature(posterior K_f),posterior corneal astigmatism(PCA),steep true net power(TNP K_S),flat true net power(TNP K_f)and total corneal astigmatism(TCA)between Pentacam and CASIA2 were 7.03±9.70μm,-0.19±0.41 D,-0.27±0.35 D,0.04±0.47 D,-0.17±0.23 D,-0.11±0.11 D,-0.02±1.02 D-0.41±0.43 D,-0.52±0.46 D,and-0.15±0.96 D,respectively.For measurement of TNP K_f with the Pentacam and CASIA2,a mean difference of 0.52 D and COR of 0.90 with P=0.02 was detected.There was no significant difference in CCT(P=0.393),anterior K_f(P=0.107),anteriorKs(P=0.414),ACA(P=0.131),posterior K_f(P=0.286),posterior Ks(P=0.418),PCA(P=0.105),TNP Ks(P=0.054),and TCA(P=0.977)between Pentacam and CASIA2.CONCLUSION:Our study reveals good agreement of CCT,corneal curvature and corneal astigmatism measured by CASIA2 and Pentacam in ectopia lentis patients.However,there was significant difference for CCT and corneal curvature values obtained by the two devices.

Comparison of 24×20 mm^(2) swept-source OCTA and fluorescein angiography for the evaluation of lesions in diabetic retinopathy

AIM: To compare ultra-widefield(24×20 mm^(2)) sweptsource optical coherence tomography angiography(SSOCTA) and fluorescein angiography(FA) in the evaluation of diabetic retinopathy(DR) lesions. METHODS: Forty-six eyes of 23 patients with treatmentna?ve DR were included at Peking University People’s Hospital from September 1, 2021, until December 31, 2021, as well as 23 age and gender matched healthy controls. Quantitative assessments of DR lesions on FA and SS-OCTA(superficial capillary plexus, SCP, 24×20 mm^(2)) were performed.RESULTS: Area of fovea avascular zone(FAZ) was larger in DR cases than controls(0.34±0.069 mm^(2) vs 0.287±0.108 mm^(2), P=0.006). In DR eyes, the mean FAZ area was 0.34±0.069 and 0.334±0.087 mm^(2) on SS-OCTA and FA, respectively(P=0.428), while the median FAZ perimeter was 2.382(IQR, 2.201-2.59) and 2.333(IQR, 2.138-2.6) mm on SS-OCTA and FA images(P=0.733). There was no significant difference in the size of the non-perfusion area(NPA) between the images on SS-OCTA and FA(12.389, IQR 4.96-28.3 and 11.125, IQR 5-28.31 mm^(2), P=0.197). The median total microaneurysm(MA) count was 35(IQR, 19-46) and 73(IQR, 43-93) on SS-OCTA and FA(P<0.001), respectively. No significant difference in intra-retinal microvascular abnormality(IRMA) and neovascularization (NV) count was found between the two techniques. The intraclass coefficient(ICCs) of all the parameters above indicated stable repeatability.CONCLUSION: Ultra-widefield SS-OCTA represents a reliable, noninvasive, and quantitative imaging technique in the assessment of microvasculature in DR, which offers a potential substitute for FA in DR evaluation.

Assessment of anterior chamber angle changes after phacoemulsification with swept-source OCT

AIM:To assess the changes of anterior chamber angle in patients with shallow anterior chamber after phacoemulsification combined with intraocular lens(IOL)implantation,based on anterior segment swept-source optical coherence tomography(AS-SS-OCT)measurements.METHODS:This was a prospective case control study;sixty eyes of sixty case were scheduled for cataract surgery with normal intraocular pressure(IOP).Based on anterior chamber depth(ACD)and gonioscopy findings,the eyes were divided into two groups:group of shallow anterior chamber and narrow angle(SAC group,30 eyes);and group of normal anterior chamber group with wide angle(NAC group,30 eyes).Measurements of ACD,anterior chamber volume(ACV),iris volume(IV),lens vault(LV),angle opening distance(AOD),angle recess area(ARA),trabecular iris space area(TISA),and trabecular iris angle(TIA)were conducted in each group before and 3mo after surgery.RESULTS:There was no significant difference in age,axial length(AL),corneal curvature,corneal diameter,intraocular pressure,and IV between two groups before surgery,except for the LV(P=0.000).ACD and ACV were prominently larger in the NAC group than the SAC group 3mo after operation(3.69±0.38 vs 3.85±0.39 mm,P=0.025;161.37±19.47 vs 178.26±20.30 mm3,P=0.002).AOD750,ARA750 in nasal and inferior quadrants,TISA750 in all quadrants except temporal,and TIA750 in all quadrants in SAC group were significantly smaller than those in NAC group after operation(all P<0.05).CONCLUSION:Cataract surgery can deepen anterior chamber and increase the width of anterior chamber angle in Chinese subjects,but the angle related parameters including AOD750,ARA750,TISA750,TIA,TISA750,and ACV in patients with shallow anterior chamber and narrow angle do not reach the normal level.

Various configuration types of the foveal avascular zone with related factors in normal Chinese adults with or without myopia assessed by swept-source OCT angiography

·AIM:To describe the morphological characteristics of foveal avascular zone(FAZ)in normal Chinese adults with or without myopia by swept-source optical coherence tomography angiography(SS-OCTA)and analyze the possible associated factors.·METHODS:Normal Chinese adults with or without myopia aged between 18 and 60 y were recruited into the study.One eye in each individual was randomly selected for scanning using SS-OCTA.FAZ parameters,central retinal thickness(CRT)and central choroidal thickness(CCT)were then analyzed.Correlations between systemic and ocular variables and FAZ parameters were subsequently evaluated.The subgroup analysis based on refractive error was also carried out.·RESULTS:In total,127 eyes out of 127 normal subjects were finally included in the study(mean age29.5±8.22 y,61 males and 66 females).The pattern of FAZ was variable:round configuration in 28 eyes(22%),quadrilateral configuration in 23 eyes(18%),pentagonal configuration in 20 eyes(16%),oval configuration in 15 eyes(12%),triangular configuration in 6 eyes(5%)and irregular configuration in 35 eyes(28%).The mean area of FAZ was0.37±0.12 mm^(2).Females had a larger FAZ(0.41±0.11 mm^(2)vs0.32±0.11 mm^(2))compared with that of males(P<0.01).All myopic individuals showed smaller FAZ area and perimeter compared with that of normal individuals(P<0.01).There was no obvious correlation between age and FAZ.In the univariate regression analysis,both axial length(AL)and refractive error were significantly related to FAZ parameters.However,only CRT showed negative correlation with FAZ in the multivariate regression analysis.·CONCLUSION:The pattern of FAZ configuration in normal Chinese adults with or without myopia is highly variable.Establishing quantitative parameters of FAZ would not only provide details of macular pathophysiology but could possibly contribute as a biomarker in disease staging.

Angle-to-angle and spur-to-spur distance analysis with high-resolution optical coherence tomography

Background:To measure angle-to-angle(ATA)and spur-to-spur(STS)distances along six meridians using highresolution swept-source optical coherence tomography(SS-OCT)and to compare those values with horizontal white-to-white(WTW)distance.Methods:68 eyes from 68 patients were quantitatively assessed with the Anterion SS-OCT(Heidelberg Engineering,Heidelberg,Germany).ATA and STS distances were measured with the SS-OCT’s B-Scan in six cross-sectional images corresponding to the vertical(6-12 o’clock),1-7 o’clock,2-8 o’clock,horizontal(3-9 o’clock),4-10 o’clock and 5-11 o’clock meridians.WTW was measured horizontally with the device’s infrared camera.A Pearson correlation analysis was carried out to compare ATA and STS distances with WTW.Results:The largest values were found for the vertical meridian and the shortest for the 2-8 o’clock meridian,both for ATA and STS distances.No statistically significant differences were found between WTW,ATA and STS along the horizontal meridian(p>0.1).However,ATA and STS showed statistically significant differences elsewhere,except for the horizontal and the 2-8 o’clock meridians(p>0.05).Moreover,we found that ATA and STS varied significantly depending on the meridian being assessed,except for ATA at 4-10 versus 3-9 o’clock and for STS at 4-10 versus 3-9 o’clock and at 3-9 versus 2-8 o’clock(p>0.1).R^(2) values ranged from 0.49 to 0.75 for ATA and STS at the different meridians,showing the best correlation at 3-9 o’clock meridian(0.64 and 0.75,respectively)and the worst at 6-12 o’clock meridian(R^(2)=0.49 for both ATA and STS).Conclusions:ATA and STS distances vary radially,thus showing that the anterior chamber is vertically oval.Therefore,it is advisable to measure these two distances along the meridian to be used.

Using choroidal thickness to detect myopic macular degeneration

AIM:To explore the usage of choroidal thickness measured by swept-source optical coherence tomography(SS-OCT)to detect myopic macular degeneration(MMD)in high myopic participants.METHODS:Participants with bilateral high myopia(≤−6 diopters)were recruited from a subset of the Guangzhou Zhongshan Ophthalmic Center-Brien Holden Vision Institute High Myopia Cohort Study.SS-OCT was performed to determine the choroidal thickness,and myopic maculopathy was graded by the International Meta-Analysis for Pathologic Myopia(META-PM)Classification.Presence of MMD was defined as META-PM category 2 or above.RESULTS:A total of 568 right eyes were included for analysis.Eyes with MMD(n=106,18.7%)were found to have older age,longer axial lengths(AL),higher myopic spherical equivalents(SE),and reduced choroidal thickness in each Early Treatment Diabetic Retinopathy Study(ETDRS)grid sector(P<0.001).The area under the receiver operating characteristic(ROC)curves(AUC)for subfoveal choroidal thickness(0.907)was greater than that of the model,including age,AL,and SE at 0.6249,0.8208,and 0.8205,respectively.The choroidal thickness of the inner and outer nasal sectors was the most accurate indicator of MMD(AUC of 0.928 and 0.923,respectively).An outer nasal sector choroidal thickness of less than 74μm demonstrated the highest odds of predicting MMD(OR=33.8).CONCLUSION:Choroidal thickness detects the presence of MMD with high agreement,particularly of the inner and outer nasal sectors of the posterior pole,which appears to be a biometric parameter more precise than age,AL,or SE.

Monitoring of edema progression in permanent and transient MCAO model using SS-OCT

Cerebral edema is a severe complication of acute ischemic stroke with high mortality but limited treatment.Although parameters such as brain water content and intracranial pressure may represent the global assessment of edema,optical properties can appear heterogeneously throughout the cerebral tissue relative to the site of injury.In this study,we have monitored the edema formation and progression in both permanent and transient middle cerebral artery oc-clusion models in rats.Edema was reflected by the decrease of optical attenuation coefficient(OAC)value in OCT system.By utilizing swept-source optical coherence tomography(SS-OCT),we found that in photochemically induced permanent focal stroke model,both the edema size and edema index,steadily developed until the end of monitor(7 h).Comparatively,when transient ischemia was introduced with endothelin-1(ET-1),the edema was detected as early as 15 min,and began to recover after 30 min until monitor was finished(3 h).Despite the majority of the edema being recovered to some extent,the condition of a small region within the edema kept deteriorating,presumably due to the reperfusion damage which might result in serious clinical outcomes.Our study has compared the edema characteristics from two different acute ischemic stroke situations.This work not only confirms the capability of OCT to temporal and spatial monitor of edema but is also able to locate focal conditions at some areas that might highly determine the prognosis and treatment decisions.