Superior Temporal Research Articles

Determination of retinal surface area.

Previous attempts at determining retinal surface area and surface area of the whole eye have been based upon mathematical calculations derived from retinal photographs, schematic eyes and retinal biopsies of donor eyes. 3-dimensional (3-D) ocular magnetic resonance imaging (MRI) allows a more direct measurement, it can be used to image the eye invivo, and there is no risk of tissue shrinkage. The primary purpose of this study is to compare, using T2-weighted 3D MRI, retinal surface areas for superior-temporal (ST), inferior-temporal (IT), superior-nasal (SN) and inferior-nasal (IN) retinal quadrants. An ancillary aim is to examine whether inter-quadrant variations in area are concordant with reported inter-quadrant patterns of susceptibility to retinal breaks associated with posterior vitreous detachment (PVD). Seventy-three adult participants presenting without retinal pathology (mean age 26.25±6.06years) were scanned using a Siemens 3-Tesla MRI scanner to provide T2-weighted MR images that demarcate fluid-filled internal structures for the whole eye and provide high-contrast delineation of the vitreous-retina interface. Integrated MRI software generated total internal ocular surface area (TSA). The second nodal point was used to demarcate the origin of the peripheral retina in order to calculate total retinal surface area (RSA) and quadrant retinal surface areas (QRSA) for ST, IT, SN, and IN quadrants. Mean spherical error (MSE) was -2.50±4.03D and mean axial length (AL) 24.51±1.57mm. Mean TSA and RSA for the RE were 2058±189 and 1363±160mm2 , respectively. Repeated measures anova for QRSA data indicated a significant difference within-quadrants (P<0.01) which, contrasted with ST (365±43mm2 ), was significant for IT (340±40mm2 P<0.01), SN (337±40mm2 P<0.01) and IN (321±39mm2 P<0.01) quadrants. For all quadrants, QRSA was significantly correlated with AL (P<0.01) and exhibited equivalent increases in retinal area/mm increase in AL. Although the differences between QRSAs are relatively small, there was evidence of concordance with reported inter-quadrant patterns of susceptibility to retinal breaks associated with PVD. The data allow AL to be converted to QRSAs, which will assist further work on inter-quadrant structural variation.

Structural parameters associated with location of peaks of peripapillary retinal nerve fiber layer thickness in young healthy eyes.

The location of the peaks of the circumpapillary retinal nerve fiber layer (cpRNFL) thickness is affected by several ocular parameters. In this study, we have generated equations that can determine the peaks of the cpRNFL. This study was a prospective, observational, cross sectional study of 118 healthy right eyes. The axial length, optic disc tilt, superiortemporal (ST)- and inferiortemporal (IT)-peaks of the cpRNFL thickness, and angles of the ST and IT retinal arteries (RA) and veins (RV) were determined. The correlations between the location of the ST- and IT-peaks and ocular structural parameters and the sex, body height and weight were calculated. The best fit equations to generate the location of the ST/IT-peaks were determined using corrected-Akaike Information Criteria. The location of the ST-peak was 0.72+(0.40 x ST-RA)+(0.27 x ST-RV)+(0.14 x height)–(0.47 x papillo-macular-position)–(0.11 x disc tilt) with a coefficient of correlation of 0.61 (P<0.0001). The location of the IT-peak was 21.88+(0.53 x IT-RA)+(0.15 x IT-RV)+(0.041 x corneal thickness)-(1.00 x axial length) with a coefficient of correlation of 0.59 (P<0.0001). The location of ST/IT peaks is determined by different parameters of the ocular structure. These equations allow clinicians to obtain an accurate location of the peaks for a more accurate diagnosis of glaucoma.

Using perimetric data to estimate ganglion cell loss for detecting progression of glaucoma: a comparison of models.

PurposeModels relating perimetric sensitivities to ganglion cell numbers have been proposed for combining structural and functional measures from patients with glaucoma. Here we compared seven models for ability to differentiate progressing and stable patients, testing the hypothesis that the model incorporating local spatial scale would have the best performance.MethodsThe models were compared for the United Kingdom Glaucoma Treatment Study (UKGTS) data for the right eyes of 489 patients recently diagnosed with glaucoma. The SITA 24‐2 program was utilised for perimetry and Stratus OCT fast scanning protocol for thickness of circumpapillary retinal nerve fibre layer (RNFL). The first analysis defined progression in terms of decline in RNFL thickness. The highest and lowest quintiles (22 subjects per group) were identified for change in thickness of inferior temporal (IT), superior temporal (ST), and global RNFL (μm year−1); a two‐way anova was used to look for differences between the models in ability to discriminate the two quintiles. The second analysis defined a ‘progression group’ as those who were flagged by the UKGTS criteria as having progressive loss in perimetric sensitivity, and a ‘no progression’ group as those with rate of change in Mean Deviation (MD) closest to 0 dB year−1 (87 subjects per group). The third analysis characterised variability of retinal ganglion cell (RGC) models for the two groups in the second analysis, using the standard deviation of residuals from linear regression of ganglion cell number over time to compute Coefficient of Variation (CoV).ResultsThe first analysis produced a negative result because the three anovas found no effect of model or interaction of model and group (F 6,294 < 3.1, p > 0.08). There was an effect of group only for the anova with the ST sector (F 6,294 = 12.2, p < 0.001). The second analysis also produced a negative result, because ROC areas were in the range 0.69–0.72 for all models. The third analysis found that even when variability in MD was low, the CoV was so large that test‐retest variation could include 100% loss of ganglion cells.ConclusionsTwo very different approaches for testing the hypothesis both gave a negative result. For all seven ganglion cell models, rates of ganglion cell loss were highly affected by fluctuations in height of the hill of vision. Methods for reducing effects of between‐visit variability are needed in order to assess progression by relating perimetric sensitivities and ganglion cell numbers.

Glaucoma Diagnostic Capability of Circumpapillary Retinal Nerve Fiber Layer Thickness in Circle Scans With Different Diameters.

To compare varying circumpapillary optical coherence tomographic (OCT) scan diameters for glaucoma diagnosis. Prospective, cross-sectional, observational study. Circumpapillary retinal nerve fiber layer thickness (RNFLT) was measured using spectral-domain OCT in 1 randomly selected eye. Scans with diameters of 3.5, 4.1, and 4.7 mm were obtained, each with 7 parameters: mean global (G) RNFLT and mean RNFLT for the temporal-inferior (TI), nasal-inferior (NI), temporal-superior (TS), nasal-superior (NS), nasal (N), and temporal (T) sectors. Areas under the receiver operating characteristic curve (AUCs) were calculated. Mean age was 55±18 years in 68 healthy eyes and 59±15 years in 95 glaucomatous eyes (P=0.12). Visual field mean deviation was -7.55±6.61 dB in glaucomatous eyes. In all 3 circle scans, mean TI RNFLT had the greatest AUC (0.974 to 0.983), followed by mean G RNFLT (0.949 to 0.956). The AUC of mean TI RNFLT in the 4.1-mm scan (0.983) was greater than the AUCs of mean TI RNFLTs in the 4.7- (0.978; P=0.128) and 3.5-mm (0.974; P=0.049) scans. The AUC of mean TI RNFLT in the 4.1-mm scan (0.983) was greater than the AUCs of mean G RNFLTs in the 3.5- (0.954; P=0.011), 4.1- (0.956; P=0.016), and 4.7-mm (0.949; P=0.011) scans. In 2 eyes with large parapapillary atrophy, RNFL segmentation error was noted only in the 3.5-mm scan in the area of parapapillary atrophy. Further investigations to find the spectral-domain OCT circle scan diameter with the best diagnostic capability and the least artifacts are warranted, especially focusing on larger-than-conventional circle scans.

Retinal nerve fiber layer thickness in normal Egyptian population

Purpose The aim of this study was to collect normative retinal nerve fiber layer thickness (RNFLT) data in the Egyptian population using the Spectralis SD-OCT and to assess its correlations with demographic data and ocular parameters. Participants and methods A total of 100 healthy eyes of 100 Egyptian individuals were enrolled in this study. BMI was calculated for each participant. Uncorrected visual acuity (UCVA) and best-corrected visual acuity were measured and converted to the logarithm of the minimum angle of resolution (logMAR). Autorefraction, keratometric (K) readings, and axial length were obtained. Patients underwent a comprehensive ophthalmic examination, including cup disc (CD) ratio and intraocular pressure (IOP) measurement. RNFLT measurement by Spectralis SD-OCT scanning was carried out using circular scans of the retinal nerve fiber layer of a diameter of 3.4 mm centered on the optic nerve head. Results The mean global (G) RNFLT was 101.74±10.05 μm (range: 79.0–123.0 μm). The mean RNFLT was the least at the temporal (T) sector, followed by nasal (N), nasal superior (NS), nasal inferior (NI), temporal superior (TS), and temporal inferior (TI) sectors. Using Pearson’s correlation, age showed a significant negative correlation with T and TI sectors. BMI showed a significant positive correlation with the G RNFLT and NS and TI sectors. Square root of logMAR of UCVA showed a significant negative correlation with the G RNFLT and NI and TI sectors. Spherical equivalent showed a significant positive correlation with the G RNFLT and the N sector. K-readings showed a significant positive correlation with the G RNFLT and N, NS, TS, NI, and TI sectors. IOP showed a significant negative correlation with the NS sector only. CD ratio showed a significant negative correlation with the G RNFLT and NS, TS, and TI sectors. Axial length showed a significant negative correlation with the G RNFLT and N, NS, and TI sectors. Using regression analysis, RNFLT was directly related to better UCVA, hyperopic refractive error, and steeper cornea, and inversely related to age, IOP, and CD ratio. Conclusion The mean RNFLT was the least at the T sector, followed by N, NS, NI, TS, and TI sectors, respectively. RNFLT was directly related to better UCVA, hyperopic refractive error, and steeper cornea, and inversely related to age, IOP, and CD ratio.

Increased glutamate/GABA+ ratio in a shared autistic and schizotypal trait phenotype termed Social Disorganisation.

Autism and schizophrenia are multi-dimensional spectrum disorders that have substantial phenotypic overlap. This overlap is readily identified in the non-clinical population, and has been conceptualised as Social Disorganisation (SD). This study investigates the balance of excitatory glutamate and inhibitory γ-aminobutyric acid (GABA) concentrations in a non-clinical sample with high and low trait SD, as glutamate and GABA abnormalities are reported across the autism and schizophrenia spectrum disorders.Participants were 18 low (10 females) and 19 high (9 females) SD scorers aged 18 to 40 years who underwent 1H-MRS for glutamate and GABA+macromolecule (GABA+) concentrations in right and left hemisphere superior temporal (ST) voxels.Reduced GABA+ concentration (p = 0.03) and increased glutamate/GABA+ ratio (p = 0.003) in the right ST voxel for the high SD group was found, and there was increased GABA+ concentration in the left compared to right ST voxel (p = 0.047). Bilateral glutamate concentration was increased for the high SD group (p = 0.006); there was no hemisphere by group interaction (p = 0.772).Results suggest that a higher expression of the SD phenotype may be associated with increased glutamate/GABA+ ratio in the right ST region, which may affect speech prosody processing, and lead behavioural characteristics that are shared within the autistic and schizotypal spectra.

Decreases in retinal nerve fiber layer and ganglion cell-inner plexiform layer thickness in schizophrenia, relation to insight: a controlled study

Objective: The present study aimed to examine retinal nerve fiber layer (RNFL) and ganglion cell inner plexiform layer (GCIPL) thicknesses in schizophrenia patients according to the control group and in schizophrenia patients with good and poor insight. Methods: Sixty-three patients with schizophrenia recruited from the outpatient clinic of psychiatry and 39 healthy controls were included in the study. Patients were separated to two groups: good insight (n=31) and poor insight (n=32) schizophrenia. Group with schizophrenia were evaluated by using Positive and Negative Symptoms Scale (PANSS), Scale to Assess Unawareness of Mental Disorder. Changes in RNFL and GCIPL of all participants were analyzed with spectral optical coherence tomography (OCT). Results: Schizophrenia patients with good and poor insight were similar according to mean age of onset for illness, mean duration of illness, mean number of hospitalizations and mean daily used antipsychotic doses equivalent to chlorpromazine. There was no difference between the schizophrenia patients and the control group in terms of age and gender. In patients with schizophrenia all quadrants of RNFL, superior temporal (ST), superior (S), and inferior (I) quadrants of GCIPL were thinner than the controls. Inferior, inferior nasal quadrants of GCIPL and all quadrants of RNFL except nasal quadrant in schizophrenia patients with poor insight was found to be thinner than the schizophrenia patients with good insight and controls. Discussion: OCT can be used to detect neurodegeneration in schizophrenic patients. It can be argued that the GCIP layer may be a more sensitive biomarker than other retinal layers, requiring further investigation in this area.

Observation Study of the Retina with the Alzheimer’s Disease or Amnestic Mild Cognitive Impairment Patients

Objective: We investigated the regularity changes of the retinal nerve fiber layer (RNFL) and macular ganglion cell complex (mGCC) of the Alzheimer’s disease (AD) and amnestic Mild Cognitive Impairment (aMCI) patients. Methods: 24 AD patients, 22 aMCI patients and 30 health controls whose age were above 60 years old were recruited in the study. The RNFL thickness and the mGCC average thickness were measured by Fourier-domain optical coherence tomography (FD-OCT). Results: Compared with the controls, we found statistically significant lower of the intraocular pressure (IOP) in the AD and aMCI patients. When compared with the AD patients and controls, aMCI patients showed a significant decrease in RNFL thickness in ST (Superior Temporal), TU (Temporal Upper) and temporal (TU+TL) quadrants. The average thickness of the mGCC was significantly thinner in the aMCI patients than in the AD patients and Controls. The Gross Loss of Volume (GLV) was significantly higher in the aMCI group than in the patients and Controls. Conclusion: AD and aMCI patients had lower IOP, but there was no evidence that IOP would decrease with the progression of disease. Retinal degeneration in the aMCI patients detected by OCT may be a pathological indicator of the disease.

Magnocellular Deficit in Dyslexia: A Preliminary Analysis of Possible Patterns of Visual Field Deficit Tested with Frequency Doubling Illusion

Purpose: To identify distinguishing visual field (VF) deficiencies in dyslexic children by exploring responses to spatial frequency doubling illusions, characteristically involving the magnocellular visual pathway. Methods: Eighteen dyslexic subjects and nine controls [mean age 8.4 ± 1.4 years (range, 7-13 years)] were consecutively enrolled and underwent VF examination on a Frequency Doubling Technology (FDT) Visual Field Instrument. Among the 19 locations of the right eye (RE) and left eye (LE) VFs, 7 topographic patterns were identified: central (CE), superior-temporal (ST), and outer superior-nasal (OSN), inner superior-nasal (ISN), inner inferior-nasal (IIN), outer inferior-nasal (OIN), inferiortemporal (IT). The default settings included measurements of both eyes separately at all 19 VF locations, exploring the central 30-degree radius of eccentricity. For each pattern indicated the thresholds of contiguous 5 point clusters of the VF in both eyes were averaged: the 7 threshold averages obtained were compared for each eye between the control and dyslexic groups. Results: For RE and LE there was non-statistically significant difference between control and affected cases for all patterns except for CE, IIN, IT patterns in the left eye (P<0.05). The two groups were comparable for loss of fixation, false positive error, and false negative error. These data indicate that the dyslexic reader's left eye presents less sensitivity to FD illusions in almost all inferior retinal hemifield. Conclusion: Dyslexics analyzed using FD illusions may be less sensitive in specific sections of the VF. This topographic failure may help to confirm that a deficit in the magnocellular visual pathway is correlated to reading difficulties.

Measurement and analysis of retinal nerve fiber layer thickness in chronic progressive external ophthalmoplegia and kearns-sayre syndrome

Objective To determine the retinal nerve fiber layer thickness (RNFLT) of chronic progressive external ophthalmoplegia (CPEO) and kearns-sayre syndrome (KSS) patients using spectral-domain optical coherence tomography (SD-OCT) and to analyze the potential influence factors for RNFLT of these patients. Methods 18 CPEO and 4 KSS (CPEO with retinitis pigmentosa and cardiac block) patients, all were muscle biopsy confirmed, were included in this study. There were 7 males and 15 females, the average age was (29.09±13.40) years, the average onset age was (16.4±10.7) years and the average disease duration was (11.30±7.30) years. All the patients underwent SD-OCT examination for the left eye, the peripapillary RNFL thickness was measured using the Spectralis 3.45 mm circle scan protocol. 8 quadrants were scanned including superior temporal (ST), temporal upper (TU), temporal lower (TL), inferior temporal (IT), inferior nasal (IN), nasal lower (NL), nasal upper (NU) and superior nasal (SN). The relationship between RNFLT and onset time, disease duration was analyzed by Pearson correlation analysis. Results The average RNFLT of ST, TU, TL, IT, IN, NL, NU, SN in the 22 patients were (136.3±24.1), (85.4±25.7), (68.2±11.7), (128.2±28.7), (127.3±29.5), (66.7±16.8), (70.1±17.6) μm, respectively. The circumferential average RNFLT was (101.5±14.4) μm. There was no significant difference between the KSS group and CPEO group (P>0.05). The decrease of the circumferential RNFLT had no relationship with the onset age (r=-0.306, P=0.11), but a negative relationship with the disease course (r=-0.518, P=0.03). There were negative relationships between the disease course and RNFLT of 4 nasal quadrants (IN: r=-0.555, P=0.01, NL: r=-0.630, P=0.00, NU: r=-0.559, P=0.01, SN: r=-0.557, P=0.01). Conclusion There is no difference in RNFLT of patients with CPEO and KSS. There is a negative relation between RNFLT (especially RNFLT of 4 nasal quadrants) and disease course. Key words: Ophthalmoplegia, chronic progressive external; Kearns-Sayre syndrome; Tomography, optical coherence

Correlation of retinal nerve fibre layer thickness and spontaneous retinal venous pulsations in glaucoma and normal controls.

PurposeTo study the relationship between amplitude of spontaneous retinal venous pulsatility (SRVP) and retinal nerve fibre layer (RNFL) thickness in glaucomatous eyes, and to determine if this parameter may be a potential marker for glaucoma severity.Method85 subjects including 50 glaucoma (21 males, 67±10 yrs) and 35 normals (16 males, 62±11 yrs) were studied. SRVP amplitude was measured using the Dynamic Vessel Analyser (DVA, Imedos, Germany) at four regions of the retina simultaneously within one disc diameter from the optic disc—temporal-superior (TS), nasal-superior (NS), temporal-inferior (TI) and nasal-inferior (NI)). This was followed by RNFL thickness measurement using spectral domain optical coherence tomography (Spectralis OCT). The correlation between SRVP amplitude and corresponding sectoral RNFL thickness was assessed by means of non-linear regression (i.e. logarithmic). Linear regression was also applied and slopes were compared using analysis of covariance (ANCOVA).ResultsGreater SRVP amplitude was associated with thicker RNFL. Global SRVP amplitude was significantly lower in glaucoma eyes compared with normals (p<0.0001). The correlation coefficient of the linear regression between RNFL and SRVP at TS, NS, TI and NI quadrants in the glaucoma group were r = 0.5, 0.5, 0.48, 0.62. Mean SRVP amplitude and RNFL thickness for TS, NS, TI and NI quadrants were 4.3±1.5, 3.5±1.3, 4.7±1.6, 3.1±1 μm and 96±30, 75±22, 89±35 and 88±30 μm, respectively. The ANCOVA test showed that the slope of linear regression between the four quadrants was not significant (p>0.05). Since the slopes are not significantly different, it is possible to calculate one slope for all the data. The pooled slope equals 10.8 (i.e. RNFL = 10.8SRVP+41).ConclusionWhile SRVP was present and measurable in all individuals, the amplitude of SRVP is reduced in glaucoma with increasing RNFL loss. Our findings suggest the degree of SRVP may be an additional marker for glaucoma severity. Further studies are needed to determine the mechanism of reduction in SRVP, and whether changes can predict increased risk of progression.

Macular retinal sensitivity using MP-1 in healthy Malaysian subjects of different ages

PurposeTo determine the influence of age and gender on macular sensitivity to light in healthy subjects of 4 age groups using the MP-1 microperimeter. MethodsA prospective study was carried out on 50 healthy subjects (age range: 18–60 years) divided into 4 age groups; 18–30 years, 31–40 years, 41–50 years and 51–60 years. Full-threshold microperimetry of the central 10° of retina was performed utilizing 32 points with the MP-1. Macula area was divided into four quadrants, which were superior nasal (SN), inferior nasal (IN), inferior temporal (IT) and superior temporal (ST). ResultsTotal mean sensitivity at 10° for age groups 18–30 years, 31–40 years, 41–50 years and 51–60 years were 19.46±0.30, 19.40±0.39, 19.47±0.35 and 18.73±0.75 (dB), respectively. There was a significant difference in total mean retinal sensitivity at 10° and at the four quadrants with age but not for gender. The retinal sensitivity was highest in the IT quadrant and lowest in the SN quadrant for all age groups. The linear regression analysis revealed that there was a 0.019dB, 0.016dB, 0.022dB, 0.029dB and 0.029dB per year age-related decline in mean macular sensitivity within the central 10° diameter in the SN, IN, IT and ST quadrants respectively. ConclusionAmong normal healthy subjects, there was a linear decline in retinal light sensitivity with increasing age with the highest reduction in the superior nasal quadrant and lowest in the inferior temporal quadrant.

Lamina cribrosa microarchitecture in normal monkey eyes part 1: methods and initial results.

To introduce quantitative postmortem lamina cribrosa (LC) microarchitecture (LMA) assessment and characterize beam diameter (BD), pore diameter (PD), and connective tissue volume fraction (CTVF) in 21 normal monkey eyes. Optic nerve heads (ONHs) underwent digital three-dimensional (3D) reconstruction and LC beam segmentation. Each beam and pore voxel was assigned a diameter based on the largest sphere that contained it before transformation to one of twelve 30° sectors in a common cylinder. Mean BD, PD, and CTVF within 12 central and 12 peripheral subsectors and within inner, middle, and outer LC depths were assessed for sector, subsector, and depth effects by analysis of variance using general estimating equations. Eye-specific LMA discordance (the pattern of lowest connective tissue density) was plotted for each parameter. The ranges of mean BD, PD, and CTVF were 14.0 to 23.1 μm, 20.0 to 35.6 μm, and 0.247 to 0.638, respectively. Sector, subsector, and depth effects were significant (P < 0.01) for all parameters except subsector on CTVF. Beam diameter and CTVF were smaller and PD was larger within the superior-temporal (ST) and inferior-temporal (IT) sectors (P < 0.05). These differences were enhanced within the central versus peripheral subsectors. Beam diameter and CTVF were larger and PD was smaller (P < 0.05) within the middle LC layer. Lamina cribrosa microarchitecture discordance most commonly occurred within the ST and IT sectors, varied by eye, and generally diminished as CTVF increased. Our data support previous characterizations of diminished connective tissue density within the ST and IT ONH regions. The clinical importance of eye-specific LMA discordance warrants further study.

Assessing assumptions of a combined structure-function index.

PurposeMedeiros et al. developed a combined structure-function index for glaucoma by combining two ganglion cell models developed by Harwerth et al. The current study assessed assumptions of the Medeiros combined structure-function index by evaluating whether the two Harwerth models gave similar distributions of ganglion cells in an independent dataset.MethodsThe Harwerth models were applied to our previously published data for retinal nerve fibre layer (RNFL) thickness (Stratus OCT 3.4) and visual field sensitivities (24-2 SITA Standard) from one eye each of 51 patients with glaucoma and 62 age-similar control subjects free of eye disease. RNFL thicknesses and perimetric sensitivities were converted to ganglion cell numbers using the Harwerth model for perimetry and the Harwerth model for RNFL. These two estimates of ganglion cell number were compared for the inferior temporal (IT) and superior temporal (ST) sectors of the optic disc and the corresponding visual field locations. Comparisons were made with 14 visual field locations per sector (including a point in the macula for the inferior temporal sector) and with 13 locations (no point in the macula). Data for controls and patients were analysed separately, comparing mean values for RNFL perimetry models. Bonferroni correction was applied to control for repeated tests of significance. The difference between mean values for the RNFL and perimetry models was quantified by equating the means for controls through reduction of the assumed axon diameter used by the RNFL model.ResultsFor the control group, the Harwerth RNFL model yielded smaller mean number of retinal ganglion cells than the Harwerth perimetry model, 23–47% lower (t > 13, p < 0.0001). This corresponded to mean axon diameters from 0.48 to 0.69 μm, with the smallest axons when the 14th location in the macula was included. With these new axon diameters, estimates of ganglion cell numbers for patients were still lower than for the RNFL model, by 19–28% (t > 6.5, p < 0.0001).ConclusionsThe Harwerth RNFL model consistently gave lower ganglion cell numbers than the Harwerth perimetry model, and this discordance persisted in patients even after reducing assumed axon diameter for controls. This finding contradicts the assumptions of the Medeiros structure-function index.

Factors Determining the Peripapillary Retinal Nerve Fiber Distribution

To evaluate the influence of the arrangement of the retinal vessels and other ocular features on the peripapillary retinal nerve fiber layer (RNFL) distribution. Fifty normal eyes were included in the study. Axial length (AL), spherical equivalent of the refractive error, and central corneal thickness (CCT) were measured. The interpeak distance of the peripapillary RNFL thickness; the angle between the superior temporal (ST) and inferior temporal (IT) retinal veins; and the average peripapillary RNFL thickness were obtained from the printout results of the spectral-domain optical coherence tomography. The distance from the optic disc center to the foveola and the ratio of distance to disc width were measured from fundus photographs. All measurements were evaluated for correlations among one another and multiple regression analysis and factor analysis was used to determine how ocular factors independently related to the RNFL distribution. As the AL became longer (P=0.033), and the angle between the ST and IT veins became smaller (P<0.001), the 2 peaks of the peripapillary RNFL thickness moved farther apart. In multiple regression analysis, angle between the ST and IT veins (β=-0.587, P<0.001) and CCT (β=-0.275, P=0.011) were significantly related to interpeak distance of the peripapillary RNFL. Decreasing angle between the IT and ST veins, thinner CCT, and increasing AL all appeared to increase the separation of the RNFL peaks. Inter-vessel polar angle affected more on determining the location of the peak in RNFL thickness map. These factors might be used to optimize normative data of the peripapillary RNFL.

The role of visual representations during the lexical access of spoken words

Do visual representations contribute to spoken word recognition? We examine, using MEG, the effects of sublexical and lexical variables at superior temporal (ST) areas and the posterior middle temporal gyrus (pMTG) compared with that of word imageability at visual cortices. Embodied accounts predict early modulation of visual areas by imageability – concurrently with or prior to modulation of pMTG by lexical variables. Participants responded to speech stimuli varying continuously in imageability during lexical decision with simultaneous MEG recording. We employed the linguistic variables in a new type of correlational time course analysis to assess trial-by-trial activation in occipital, ST, and pMTG regions of interest (ROIs). The linguistic variables modulated the ROIs during different time windows. Critically, visual regions reflected an imageability effect prior to effects of lexicality on pMTG. This surprising effect supports a view on which sensory aspects of a lexical item are not a consequence of lexical activation.

The Locations of Circumpapillary Glaucomatous Defects Seen on Frequency-Domain OCT Scans

To examine the locations of local glaucomatous damage around the optic disc as seen in the circumpapillary retinal nerve fiber layer (RNFL) on frequency domain optical coherence tomography (fdOCT). Optic disc fdOCT volume scans from 54 healthy control eyes and 114 patient eyes, classified as suspected or mild glaucoma, were analyzed. All patient eyes had 24-2 visual fields (VFs) with mean deviations better than -5.5 dB. By hand-correcting automated segmentation, the RNFL thickness profile was obtained for a circumpapillary circle. RNFL defects were defined as regions where the patient's RNFL thickness fell below the 99% confidence limit of control values. The location of a defect was defined as the point of greatest difference between the patient's thickness and the 99% limit. The locations of major blood vessels (BVs) were marked, and separated into superior-nasal (SN), superior-temporal (ST), inferior-temporal (IT), and inferior-nasal (IN) groups. Of the 114 patient eyes, 45 exhibited a total of 75 RNFL defects. The locations of these defects clustered around the ST, SN, and IT, but not the IN BVs. The absence of defects in the IN region indicates that the locations of local defects are not simply related to either BV location or RNFL thickness. The local defects in the ST and IT regions can be related to arcuate defects seen on 24-2 and 10-2 VFs. However, the defects in the SN region suggest the presence of VF defects that may be overlooked because they fall largely outside the 24-2 test grid.

Comparison of optic nerve morphology in eyes with glaucoma and eyes with non-arteritic anterior ischemic optic neuropathy by Fourier domain optical coherence tomography

The aim of this study was to compare the optic nerve head (ONH) and peripapillary retinal nerve fiber layer (RNFL) thickness in eyes with glaucoma and non-arteritic anterior ischemic neuropathy (NAION) by Fourier domain optical coherence tomography (FDOCT), and to evaluate the diagnostic capability of FDOCT in glaucoma and NAION. This study included 26 eyes with glaucoma (36.6%), 15 eyes with NAION (21.1%) and 30 eyes of normal subjects (42.3%). Those with the following conditions were excluded; a visual field defect greater than one hemifield, spherical equivalent (SE) more than ±6 D, or the onset of NAION within 6 months. FDOCT was used to analyze the characteristics of ONH and RNFL thickness. Among the three groups of subjects, glaucomatous eyes had the largest cup area and cup volume, and the smallest rim area, rim volume and disc volume (P<0.05). NAION eyes had the smallest cup area and cup volume (P<0.05), but their rim area, rim volume and disc volume were comparable to those of control eyes (P>0.05). The cup-to-disc (C/D) ratio was increased in glaucomatous eyes but reduced in NAION eyes compared with control eyes. Glaucomatous eyes had the greatest loss of RNFL thickness in the temporal upper (TU), superior temporal (ST) and temporal lower (TL) regions (P<0.05), whereas NAION eyes had the smallest RNFL thickness in the superior nasal (SN) and nasal upper (NU) regions (P<0.05). The areas under the receiver operator characteristic curve (AROCs) of the temporal, superior and inferior RNFL in glaucomatous eyes were greater compared with that of the disc area (P<0.05). In addition, the AROCs of the temporal, superior and inferior RNFL were higher compared with that of nasal RNFL (P<0.05). The AROCs of all parameters for NAION were not significantly different, with the exception of superior, nasal superior and inferior temporal RNFL (P<0.05). In conclusion, FDOCT is able to detect quantitative differences in the optic disc morphology and RNFL thickness between glaucomatous and NAION eyes. These differences may provide new insights into the clinical characteristics and diagnosis of the two diseases.

Sound-identity processing in early areas of the auditory ventral stream in the macaque

Auditory cortical processing is thought to be accomplished along two processing streams. The existence of a posterior/dorsal stream dealing, among others, with the processing of spatial aspects of sound has been corroborated by numerous studies in several species. An anterior/ventral stream for the processing of nonspatial sound qualities, including the identification of sounds such as species-specific vocalizations, has also received much support. Originally discovered in anterolateral belt cortex, most recent work on the anterior/ventral pathway has been performed on far anterior superior temporal (ST) areas and on ventrolateral prefrontal cortex (VLPFC). Regions of the anterior/ventral stream near its origin in early auditory areas have been less explored. In the present study, we examined three early auditory regions with different anteroposterior locations (caudal, middle, and rostral) in awake rhesus macaques. We analyzed how well classification based on sound-evoked activity patterns of neuronal populations replicates the original stimulus categories. Of the three regions, the rostral region (rR), which included core area R and medial belt area RM, yielded the greatest classification success across all stimulus classes or between classes of natural sounds. Starting from ∼80 ms past stimulus onset, clustering based on the population response in rR became clearly more successful than clustering based on responses from any other region. Our study demonstrates that specialization for sound-identity processing can be found very early in the auditory ventral stream. Furthermore, the fact that this processing develops over time can shed light on underlying mechanisms. Finally, we show that population analysis is a more sensitive method for revealing functional specialization than conventional types of analysis.

Evidence for Altered LRP/RAGE Expression in Alzheimer Lesion Pathogenesis

There is significant evidence to suggest that a damaged or dysfunctional blood-brain barrier (BBB) may contribute to the pathogenesis of Alzheimer's disease (AD) lesions. Lipoprotein receptor-related protein (LRP-1) and receptor for advanced glycation end products (RAGE) are known to be important (BBB) capillary transport proteins. Altered expression of either of these capillary endothelial LRP-1 and RAGE receptor proteins could indicate a dysfunction of the BBB and its transport regulation of beta-amyloid (Abeta). Cortical samples from the superior temporal (ST) and calcarine occipital (COC) cortices of ten confirmed AD brains and ten comparison group (CG) brains were examined. The densities of neurofibrillary tangles (NFTs), senile plaques (SPs) and LRP-1 and RAGE positive capillaries were recorded and statistically analyzed. There was a statistically significant difference between AD and CG cases and the densities of LRP-1 and RAGE positive capillaries, the AD cases demonstrating the greater numbers. Further, in AD brains there were significant negative correlations between the Abeta burden of SPs and both LRP-1 and RAGE-positive capillaries [p < .001]. Additionally, there was a strong positive correlation between LRP-1 and RAGE capillaries in AD brains [p < .001]. These results suggest that alterations in the LRP-1 and RAGE mediated transport of Abeta take place in AD brains in lesion prone regions and may therefore contribute to SP lesion pathogenesis.