Fractal analysis of retinal vasculature in normal subjects on ultra-wide field fluorescein angiography

AIM: To evaluate the fractal feature of the retinal vasculature of normal eyes on a stereographic projected and montaged ultra-wide field(UWF) fluorescein angiography(FA).METHODS: Prospective, observational, cross-sectional study. Totally 59 eyes of 31 normal subjects were imaged using the Optos 200 Tx. Images obtained at different gaze angles stereographically projected and montaged. The early-phase UWF FA frames were processed to segment the retinal vasculature and the results were exported as binary masks. The fractal dimension(FD) was calculated using the box-counting method.RESULTS: The global FD for the entire retina was 1.6±0.04, with no difference between males and females(1.59±0.04 vs 1.61±0.04, P=0.084) or between right and left eyes(1.6±0.04 vs 1.6±0.05, P=0.61). FD was nonuniformly distributed among four quadrants(P<0.001) and decreased as the distance from the fovea increased(P<0.001). A negative association was observed between FD and age(R=-0.37, P=0.006), and this relationship was observed in the posterior and mid-peripheral retina(P<0.05) but absent in far-periphery(P>0.05).CONCLUSION: Fractal geometry is non-uniformly distributed across the retina in normal eyes and decreases from the fovea to the far-periphery. Subjects with an older age tend to have a smaller FD, however, the FD in the farperiphery does not appear to be influenced by age.

Macular Thickness by Optical Coherence Tomography in Normal Togolese Melanoderma Subjects: A Case Study of 338 Eyes

Objective: Maculopathies are more and more frequent. For the follow-up of its evolution and therapy, it seems important for us to determine the baseline in normal subjects by Optical Coherence Tomography (OCT). The goal here is to determine the acceptable range of macular thickness in normal black subjects in Lomé. Methodology: This is a retrospective study over a 6-month period. It did not include all patients with retinopathy of any cause, maculopathy, and glaucoma. The analyzed variables were the average macular thickness, the central macular thickness, and the total macular volume. Results: Out of the 433 macular OCT performed, 191 patients were selected;a total of 338 eyes. These included 96 men and 95 women. A sex ratio was 1.01. The median age was 44.1 years with extremes ranging from 10 to 70 years. The average macular thickness was 263.4 μm for the right eye and 263.7 μm for the left eye. The central macular thickness was 174.1 μm for the right eye and 173.3 μm for the left eye. The total macular volume was 7.4 in both eyes. Discussion: No significant statistical difference existed between the two sexes. The average macular thickness found in this study was within the range of normality observed in the literature, which is between 216 and 288 μm. Conclusion: The average macular thickness of the normal subject in Lomé was 263.4 μm.

Age related changes of the central lamina cribrosa thickness, depth and prelaminar tissue in healthy Chinese subjects

AIM： To investigate the variation in the central lamina cribrosa thickness（cLCT）, and the central anterior lamina cribrosa surface depth（cALCSD）, as well as the central prelaminar tissue thickness（cPLTT） related to age in healthy Chinese subjects.METHODS： A total of 96 eyes from 96 Chinese healthy subjects were recruited. According to age, the 96 cases were divided into three groups： the young group（YG, 18-39 y）, middle-age group（MG, 40-59 y） and older-age group（OG, 60 y and above）. Lamina cribrosa images were obtained from all participants using radial linear protocol by enhanced depth imaging spectral-domain optical coherence tomography. The cLCT, cALCSD and cPLTT were calculated from the average value of the lamina cribrosa thickness, anterior lamina cribrosa surface depth and prelaminar tissue thickness in the optic nerve head（ONH） centre point and paracentral points（150 μm from the centre point in the horizontal and vertical directions）. RESULTS： For the total subjects, the mean cLCT, c ALCSD and cPLTT were 235.18±41.27, 358.02±93.80 and 182.02±92.11 μm, respectively. No statistically significant differences in cLCT, cALCSD or cPLTT were found between gender and different eyes（P=0.27-0.92）. The cLCT of the OG was the thickest among the three groups, while the c PLTT of the YG was the thickest among the three groups（P〈0.05）. Age was positively correlated with cLCT（r=0.42, P〈0.001）, and negatively correlated with cPLTT（r=-0.24, P=0.02）. No significant correlation was found between the age and cALCSD（r=-0.06, P=0.55）. And no correlation has been found between axial length and cLCT, cALCSD and c PLTT（P=0.11-0.81）.CONCLUSION： The impact of age on the cLCT and the cPLLTT should be taken into account when analysing glaucoma and other diseases related to lamina cribrosa.

The Study of Retinal Nerve Fiber Layer Thickness of Normal Eyes Using Scanning Laser Polarimetry

Purpoe: To evaluate retinal nerve fiber layer (RNFL) thickness measurements in local normal Chinese subjects of different age groups and analyse the correlation of RNFL thickness with age using scanning laser polarimetry (SLP,GDxVCC). To assess the reproducibility of RNFL thickness measurement with GDxVCC. Methods: The RNFL thickness of 67 normal subjects (123 eyes) were measured by GDxVCC. The average TSNIT parameters were calculated. The differences of RNFL thickness between sex,right and left eyes,superior and inferior were compared. The relationship between RNFL thickness and age was analyzed with correlation analysis and linear regression analysis. The intraclass correlation coefficients (ICC) of three images in every eye were calculated. Results: The average peripapillary RNFL thickness at the superior,inferior and whole ellipse regions in 123 eyes of 67 normal subjects were (70.30±6.76)(?)m,(67.35±6.77)(?)m and (56.87±4.53)(?) m,respectively. The average TNSIT standard deviation was 23.68±4.61 and the average inter-eye symmetric value was 0.86±0.11. There were significant difference of RNFL thickness between superior and inferior (t=4.952,P < 0.001). There were significant difference of inferior RNFL thickness and TNSIT standard deviation between right and left eyes (P=0.005 and 0.002),while not significant difference of superior RNFL thickness and whole mean RNFL thickness between right and left eye (P=0.086 and 0.529). There was no significant difference in TSNIT parameters between different genders. There was a slight negative correlation average RNFL thickness in superior sector with age (decreased approximately 0.15 microns per year,P=0.047) in the subjects aged below 60 years old. The ICC values of RNFL thickness were >0.8 in superior,inferior and global. Conclusions: The RNFL thickness can be measured accurately by GDxVCC and the reproducibility of RNFL thickness measurement by GDxVCC is good. There was a slight negative correlation between average RNFL thickness in superior with age. More researches on the effects of age on RNFL thickness by GDxVCC are needed.

STUDY OF REGIONAL STABILITY OF ECD DISTRIBUTION IN NORMAL BRAIN

Objective To evaluate in vivo stability of ethylenedylbis cysteine diethylester (ECD) brain SPECT. Methods Each of 13 normal volunteers (31. 2 ± 11. 8 years) has 12 dynamic SPECK scans ac-quired in 60min 1h after an injection of 99mTc-ECD using a triple headed gamma camera equipped with ultra high resolution fan beam collimators. Average counts per pixel were measured from frontal, temporal, parie-tal, occipital regions, cerebellum, basal ganglia, thalamus and white matter. Regional ECD clearance rates, regional gray-to-white matter (G/W) ratios and the change of the G/W ratio were calculated. Results The average ECD clearance rate was 4. 2% /h, ranged from 3. 03% /h to 5. 41% /h corresponding to white matter and occipital. There was no significant difference between regional ECD clearance rates. Regional G 7W ratio was between 1.27 to 1.75. The G/W ratio of temporal lobe was lower than the occipital ( P <0.05). The change of regional G/W ratio with time is slow. Conclusion Regional ECD distribution is stable in normal brain. ECD clearance from brain is slow and no significant regional difference.

The correlation between serum uric acid level and early- phase insulin secretion in subjects with normal glucose regulation

Objective To investigate the correlation between serum uric acid(SUA)level and early-phase insulin secretion in subjects with normal glucose regulation(NGR).Methods Totally 367 community NGR residents confirmed by a 75g oral glucose tolerance test were enrolled.