Repeatability,interocular correlation and agreement of optic nerve head vessel density in healthy eyes:a sweptsource optical coherence tomographic angiography study

AIM:To assess the repeatability,interocular correlation,and agreement of quantitative swept-source optical coherence tomography angiography(OCTA)optic nerve head(ONH)parameters in healthy subjects.METHODS:Thir ty-three healthy subjects were enrolled.The ONH of both eyes were imaged four times by a swept-source-OCTA using a 3 mm×3 mm scanning protocol.Images of the radial peripapillary capillary were analyzed by a customized Matlab program,and the vessel density,fractal dimension,and vessel diameter index were measured.The repeatability of the four scans was determined by the intraclass correlation coefficient(ICC).The most well-centered optic disc from the four repeated scans was then selected for the interocular correlation and agreement analysis using the Pearson correlation coefficient,ICC and Bland-Altman plots.RESULTS:All swept-source-OCTA ONH parameters exhibited certain repeatability,with ICC>0.760 and coefficient of variation(CoV)≤7.301%.The obvious interocular correlation was observed for papillary vessel density(ICC=0.857),vessel diameter index(ICC=0.857)and fractal dimension(ICC=0.906),while circumpapillary vessel density exhibited moderate interocular correlation(ICC=0.687).Bland-Altman plots revealed an agreement range of-5.26%to 6.21%for circumpapillary vessel density.CONCLUSION:OCTA ONH parameters demonstrate good repeatability in healthy subjects.The interocular correlations of papillary vessel density,fractal dimension and vessel diameter index are high,but the correlation for circumpapillary vessel density is moderate.

Correlation between optical coherence tomography, multifocal electroretinogram findings and visual acuity in diabetic macular edema

AIM:To analyze the correlation between macular morphology and function in eyes with diabetic macular edema(DME).METHODS:Fifty-five eyes with different visual acuity(VA)of 32 patients who suffered from DME were analyzed using multifocal electroretinography(mfERG)and optical coherence tomography(OCT).The parameters of mfERG including implicit times and response amplitude were compared to those of 50 normal eyes of 36 age-matched subjects.Correlation analysis was performed between VA,the parameters of mfERG including implicit times and response amplitude,and the central macular thickness(CMT).RESULTS:The amplitude of N1 and P1 were significantly decreased and their latency were significantly increased in five ring regions of the retina in patients with DME.There was statistically significant correlation between logMAR BCVA and P1 amplitude densities in rings 1-4(r=-0.306,-0.536,-0.470,-0.362;P=0.023,<0.01,<0.01,0.007 respectively),N1 amplitude in ring 2 and ring 3(r=-0.035,-0.286;P=0.019,0.034 respectively).There was poor correlation between the CMT and best-corrected visual acuity(BCVA;r=0.288,P=0.033),but there was no significant correlation between CMT and amplitude or implicit time of N1 and P1(P>0.05)in the central macular ring.Multiple stepwise regression analysis showed that P1 amplitude density in ring 2 was the only contributor to the VA.CONCLUSION:It seems to be more appropriate of combining use of mfERG with OCT for the evaluation of macular function in eyes with DME.

Substrate temperature dependence of chemical state and magnetoresistance characteristics of Co–TiO2 nanocomposite films

Co−TiO2 nanocomposite films were prepared via magnetron sputtering at various substrate temperatures.The films comprise Co particles dispersed in an amorphous TiO2 matrix and exhibit coexisting ferromagnetic and superparamagnetic properties.When the substrate temperature increases from room temperature to 400℃,Co particles gradually grow,and the degree of Co oxidation significantly decreases.Consequently,the saturation magnetization increases from 0.13 to 0.43 T at the same Co content by increasing the substrate temperature from room temperature to 400℃.At a high substrate temperature,conductive pathways form among some of the clustered Co particles.Thus,resistivity rapidly declines from 1600 to 76μΩ·m.The magnetoresistive characteristic of Co−TiO2 films is achieved even at resistivity of as low as 76μΩ·m.These results reveal that the obtained nanocomposite films have low Co oxidation,high magnetization and magnetoresistance at room temperature.

Visual impact of sub-Tenon anesthesia during combined phacoemulsification and vitrectomy surgery

AIM:To investigate the visual impact of sub-Tenon anesthesia during combined phacoemulsification and vitrectomy surgery.METHODS:In this prospective case series, consecutive patients who underwent combined phacoemulsification and pars plana vitrectomy(PPV) under sub-Tenon anesthesia between October 2008 and September 2009 were enrolled. The patients were asked whether they could see the light of the operating microscope or not between various surgical steps with their contralateral eye being covered.RESULTS:A total of 163 eyes of 163 patients were enrolled in this study. After their contralateral eyes were covered, 152(93.3%) patients said that they could not see any light at least during one of the surgical steps. All eyes recovered to at least light perception on the first postoperative day. The incidence of no light perception during the surgery was not related to demographic factors, including age, gender, or type of ocular diseases.CONCLUSION:The incidence of no light perception during combined phacoemulsification and vitrectomy under sub-Tenon anesthesia was high in our study.Patients should be duly informed about this temporary but potential intraoperative event.

A simple,low-cost 3D printed adaptor for endoillumination in intraocular surgery

Dear Editor,The application of three-dimensional (3D) printing techniques in ophthalmology enables cost-effective design and production of custom medical instruments.Complications of cataract surgery,such as a dropped nucleus,cortex,or intraocular lens,may require vitreoretinal surgery.Although there is a vitrectomy port in most phacoemulsification machines,endoillumination is not available.There are some external light source devices such as Photon (Synergetics),XenotronⅢ(Geuder) and Bright Star (DORC),but they are expensive and may not be available in all hospitals.This study was approved by the Institutional Review Board of Joint Shantou International Eye Center.

Reduced Macular Vascular Density in Myopic Eyes

Background： Morphological changes of the vasculature system in patients with myopia have been observed by Doppler ultrasound and fundus fluorescein angiography （FFA）; however, these studies have limitations. Doppler ultrasound provides low-resolution images which are mainly obtained from visualized large vessels, and FFA is an invasive examination. Optic coherence tomography （OCT） angiography is a noninvasive, high-resolution measurement for vascular density. The purpose of this study was to investigate the change of vascular density in myopic eyes using OCT angiography. Methods： This cross-sectional study includes a total of 91 eyes ~Yom 47 participants including control, moderate, and high myopia that were evaluated by OCT angiography. Patients with myopia were recruited from the Refractive Department, Shenzhen Aier Eye Hospital, from August 5, 2015 to April 1, 2016. Emmetropic eyes were from healthy volunteers. The vascular density at macula and optic disc regions, ganglion cell complex （GCC） thickness, and retinal nerve fiber layer （RNFL） thickness were measured. Their relationships with axial length （AL） and refractive error were analyzed. One-way analysis of variance （ANOVA）, Pearson＇s correlation, and generalized estimating equation were used for statistical analysis, Results： Both superficial and deep macular vascular density were highest in control （25.64% ± 3.76% and 37.12% ± 3.66%, respectively）, then in moderate myopia （21.15% ± 5.33% and 35.35% ± 5.50%, respectively）, and lowest in high myopia group （ 19.64% ± 3.87% and 32.81% ± 6.29%, respectively） （F =13.74 and 4.57, respectively; both P 〈 0.001）. Both superficial （β = -0.850 and 0.460, respectively） and deep （β = -0.766 and 0.396, respectively） macular vascular density were associated with AL and spherical equivalent （all P 〈 0.001 ）. Superficial macular vascular density was associated with GCC thickness （β = 0.244, P = 0.040）, independent of spherical equivalent. The vascular density in optic disc region had no difference among the three groups, and it was not associated with AL, spherical equivalent, or RNFL thickness. Conclusion： Our results suggested that with the increase of myopia, the vascular density decreased in macular region, but not in optic disc region.