Thickness In Healthy Subjects Research Articles

Informative value of biometric indices of iris, sclera and cornea in primary open-angle glaucoma diagnosis

Aim: to study the thickness of cornea, iris and scleral tissue, to determine its asymmetry between fellow eyes in healthy subjects and in patients with primary glaucoma. To determine the relationship between changes in biomechanical properties of the cornea and sclera and iris thickness in healthy subjects and in patients with primary glaucoma.
 Materials and methods. 10 patients (20 eyes) with primary glaucoma were examined. The control group consisted of 10 people (20 eyes). In all patients ultrasound biomicroscopy (Humphrey Instruments (USA), Model 840) was performed.
 Results and discussion. The article presents a study of the corneoscleral and iris tissue thickness in primary glaucoma, as well as the increase pattern of the revealed asymmetry in corneoscleral and iris tissue thickness from normal state to glaucoma. A positive direct correlation between the indices of cornea, sclera, and iris thickness in the primary glaucoma group and between biometric parameters of sclera and iris and the of corneal hysteresis value in primary open-angle glaucoma.

A Functional Regression Model of the Retinal Nerve Fiber Layer Thickness in Healthy Subjects.

PurposeA new functional regression model is presented to explain the intersubject variability of the circumpapillary retinal nerve fiber layer (RNFL) thickness in healthy subjects.MethodsTo evaluate the functional regression approach we used data from 202 healthy volunteers, divided equally into training samples (TS) and validation samples (VS). Covariates included RNFL, fovea distance, fovea angle, optic disk ratio, orientation and area provided by Fourier-domain–optical coherence tomography, age, and refractive error. Root mean square errors (RMSE) were calculated for each of the 256 sectors and for the 12 clock-hour sectors in the TS and VS and were compared to the RMSE of the previous model and the standard deviation of the raw data.ResultsWith the functional regression approach, we were able to explain on average 27.4% of the variation in the TS and 25.1% of the variation in the VS. The new model performed better compared to a multivariate linear regression model. It performed best in the superior-temporal and inferior-temporal clock-hour sectors where the percentage of RMSE reduction ranged between 26.3% and 44.1% for the TS and between 20.6% and 35.4% for the VS.ConclusionsThe new functional regression approach improves on the multivariate linear regression model and allows an even larger reduction of the amount of intersubject variability, while at the same time using a substantially smaller number of parameters to be estimated.Translational RelevanceThe demonstrated reduction of interindividual variation is expected to translate into an improved diagnostic separation between healthy and glaucomatous subjects, but this remains to be demonstrated in further studies.

Choroidal Thickness in Healthy Subjects.

Purpose:To measure the choroidal thickness by enhanced depth imaging optical coherence tomography (EDI-OCT) in normal eyes.Methods:In a prospective case series, 208 eyes of 104 normal Iranian subjects were enrolled. Complete ophthalmic examination was performed. Inclusion criteria were best corrected visual acuity (BCVA) ≥20/20, ≤ ±1 diopter of refractive error in either spherical or cylindrical components, normal intraocular pressure (IOP) and no systemic or ocular diseases. The choroidal thickness was measured by EDI-OCT subfoveally, and 1500 μm and 3000 μm nasal and temporal to the fovea.Results:Mean age was 34.6 ± 9.8 years (range, 18–57 years). Mean subfoveal choroidal thickness was 363 ± 84 μm. Choroidal thickness was 292 ± 76 and 194 ± 58 μm at 1500 and 3000 μm nasal to the fovea, respectively, and 314 ± 77 and 268 ± 66 μm at 1500 and 3000 μm temporal to the fovea, respectively. There was no statistically significant difference in the choroidal thickness between sexes and laterality of the eyes. Choroidal thickness at fovea (P < 0.001) and at all extrafoveal locations decreased significantly for every 10 years increase in age.Conclusion:In normal Iranian subjects participating in this study, mean choroidal thickness was comparable with other reports.

Variability of choroidal and retinal thicknesses in healthy eyes using swept-source optical coherence tomography - implications for designing clinical trials.

AimThe aim was to study the variability of choroidal scleral interface (CSI) thickness in healthy subjects and its relevance for designing future studies.MethodsA total of 123 volunteers were imaged using swept-source optical coherence tomography. Early treatment diabetic retinopathy grid was used.ResultsMean central retinal thickness was 285.85±14.53 µm and 287.18±12.93 µm, and mean central CSI thickness was 273.94±77.77 µm and 271.19±78.85 µm for the right and left eyes, respectively. Mean retinal and CSI thicknesses correlated negatively with age (p=0.023, r=−0.208 and p<0.0001, r=−0.426, respectively) and axial length (p=0.016, r=−0.220 and p<0.0001, r=−0.504, respectively). To detect a CSI change of at least 112 µm, a sample size of 11 or 36 per group is needed for a single- or double-arm study, respectively (α=0.05, power =0.90, no loss to follow-up, assuming standard deviation in future studies as 100 µm).ConclusionFuture clinical studies using CSI as end point are possible with regard to sample size needed.

Choroidal thickness measurements around the optic disc in healthy subjects using Swept‐Source optical coherence device

PurposeTo measure the peripapillary choroidal thickness in an extensive area around the optic nerve and several established sections in healthy subjects using a swept‐source optical coherence tomography (SS‐OCT) device.MethodsA total of 86 healthy subjects were included in the study. An optic disc 6.0 × 6.0 mm three‐dimensional scan of the right eye was obtained using the Deep Range Imaging (DRI) OCT Triton. Centered in the optic disc a 26x26 cube‐grid was generated to automatically measure the choroidal thickness. Seven choroidal zones were established and analysed: 3 superior (temporal, central, and nasal), 3 inferior (temporal, central, and nasal) and the optic nerve headResultsPeripapillary coroidal thickness was significantly thinner in the central superior, nasal superior, and nasal inferior zones in healthy eyes. Choroidal thickness in the central superior zone was 156.17 ± 80.89 μm; in the nasal superior zone was 168.34 ± 73.45 μm and in the nasal inferior zone was 137.47 ± 65.96 μm.ConclusionsPeripapillary choroidal thickness in healthy subjects is higher in the temporal and superior zones around the optic disc. SS‐OCT could be a useful tool to evaluate choroidal thinning.

Mapping diurnal changes in choroidal, Haller’s and Sattler’s layer thickness using 3-dimensional 1060-nm optical coherence tomography

To test the significance of diurnal changes in choroidal, Haller's and Sattler's layer thickness in healthy subjects using spatial analysis of three-dimensional (3D) 1060-nm optical coherence tomography (OCT) scans. Automatically generated choroidal, Haller's and Sattler's layer thickness maps were statistically analyzed for 19 healthy subjects at two time points (8 a.m. and 6 p.m.) that represent the currently proposed ChT peak and nadir. All subjects were imaged by high-speed 1060-nm OCT over a 36° × 36° field of view. Spatial distribution of layer thickness was analyzed using the Early Treatment Diabetic Retinopathy Study (ETDRS) grid. The choroid was significantly thicker at 8 a.m. than at 6 p.m. (p < 0,0125, paired t-test, Bonferroni correction). Diurnal variation of mean choroidal thickness (ChT) for all ETDRS subfields was 12 μm. Haller's layer thickness showed no significant diurnal variation (P > 0.0125), but Sattler's layer was thicker in the morning than in late afternoon (P < 0.0125). Our measurements indicate that diurnal ChT variation may exist, but is less relevant than previously proposed by studies using single location imaging. Sattler's layer shows diurnal variation in line with ChT.

Enhanced depth OCT imaging of the lamina cribrosa for 24 hours

The lamina cribrosa thickness (LCT) could be affected by dynamic changes in its structure. Using Spectral-domain-optical coherence tomography (SD-OCT), we have studied the behaviour of the laminar region in 14 young subjects over 24h. Significant changes in LCT were observed, depending on the time at which the measurement was taken, with the maximum thickness being observed at 7.30 p.m., and the minimum at 7.30 a.m. This finding could suggests a circadian pattern in the LCT thickness in healthy subjects, which could have implications for the classification, diagnosis and prognosis of both normal and glaucomatous subjects.

Strengthening of Quadriceps by Neuromuscular Magnetic Stimulation in Healthy Subjects

BackgroundQuadriceps muscle strengthening is one of the rehabilitation strategies for improving walking in some people with gait impairments, and neuromuscular electrical stimulation (NMES) has been used for that reason. The strengthening effect of neuromuscular magnetic stimulation (NMMS) on the quadriceps has been demonstrated in various conditions, but not specifically for gait training. The purpose of this study was to determine whether the effect of NMMS is clinically applicable. ObjectiveTo determine the effect of NMMS on quadriceps muscle strength, cross-sectional area (CSA) and thickness in healthy subjects. DesignSingle-blind, prospective, case-control study. SettingTertiary academic hospital setting. ParticipantsA total of 40 healthy volunteers were randomly assigned to an NMMS (n = 20) or control group (n = 20). InterventionsFifteen minutes of quadriceps NMMS of at maximum tolerable intensity, 3 times per week for 5 weeks. Main Outcome MeasurementsAt baseline and after the intervention, the CSA and thicknesses of the rectus femoris and vastus intermedius were measured by ultrasound. Isometric and isokinetic maximal and average peak torques of the dominant side knee extensors were also measured at pre- and postintervention. ResultsThere were no between-group differences in strength, CSA, or muscle thickness at baseline. Isometric maximum and average peak torque of NMMS group were increased significantly after 5 weeks of intervention (P < .001). The isokinetic maximum and average peak torque of NMMS group were increased significantly at both angle velocities of 60°/sec and 120°/sec after 5 weeks of intervention (P < .001). However, neither group showed a significant difference in cross-sectional area or thickness after training. ConclusionNMMS can be a useful strengthening method for large skeletal muscles such as the quadriceps. Level of EvidenceII

Effects of age and gender on macular thickness in healthy subjects using spectral optical coherence tomography/scanning laser ophthalmoscopy.

To examine healthy subjects for normal macular thickness values and determine the effects of gender and age in a Turkish population, using spectral optical coherence tomography/scanning laser ophthalmoscopy (OCT/SLO). Six hundred fourteen eyes of 307 subjects with no history of ocular diseases and normal ophthalmic examination were recruited in this cross-sectional, prospective study. The participants were divided into three groups based on age (between 20 and 29years: group 1, between 30 and 39years: group 2, between 40 and 49years: group 3). All subjects were scanned with spectral OCT/SLO, performed by one examiner to acquire the retinal thickness map in the ETDRS grid, and values were recorded for nine sectors, and effects of age and gender were evaluated. When all the subjects were evaluated, the thicknesses were lower in women than men in all sectors (p<0.001). When divided in groups based on age, this difference remained only in the outer segments. However, the differences in outer layers, except outer nasal layer, were thicker in women in group 3 when compared to others in group 3. When compared between groups, only central thickness in group 3 was shown to be higher than group 1 (p=0.06). There was no significant difference of thicknesses in any sector when compared right and left eyes of all subjects. The study reports the variation in retinal thickness between age and gender in a relatively large sample of a Turkish population. It is important to consider these effects while interpreting the OCT images to make an appropriate diagnosis in retinal diseases.

Reliability of musculoskeletal ultrasound imaging to measure supraspinatus tendon thickness in healthy subjects.

[Purpose] The purpose of this study was to assess intra-rater and inter-rater reliability of musculoskeletal ultrasound (MSKUS) as a tool to measure supraspinatus tendon thickness in healthy subjects. [Subjects and Methods] Twenty healthy subjects were assessed in similar sitting position. Two experienced musculoskeletal ultrasound specialists measured supraspinatus tendon thickness. Tendon was measured twice in one day by each of two raters with an interval of one hour for within day reliability and was re-measured following one week for between days reliability. Data analysis was performed using the intraclass correlation coefficient (ICC) and standard error of measurement (SEM). [Results] Results reflected excellent within day intra-rater and inter-rater reliability with Mean ± standard deviation (SD)=5.14 ± 0.83 and 5.17 ± 0.78, ICC (2,1)=0.89–0.93 and ICC (2,2)=0.98 (0.95−0.99) and SEM=0.18–0.18 and 0.17 while between days intra-rater rater and inter-rater reliability with Mean ± SD=5.14 ± 0.83 and 5.17 ± 0.78, ICC(2,1)=0.88–0.90 and ICC(2,2)=0.95 (0.88−0.98), SEM=0.17–0.38 and 0.17 [Conclusion] The results of the current study indicate that MSKUS is a reliable tool for measuring supraspinatus tendon thickness in healthy subjects.

Ultrasonographic assessment of the anterolateral ligament of the knee in healthy subjects.

The aim of our study was to determine inter-observer agreement in the ultrasonographic identification of the anterolateral ligament (ALL) and in the evaluation of its length and thickness in healthy subjects. 80 healthy volunteers (160 knees) (42 males and 38 females) were enrolled in the study. All subjects underwent ultrasound (US) examination of both knees, performed by two physicians with over ten years of musculoskeletal US experience. In order to keep the ALL under optimal tension, the knee was flexed at approximately 30-35°, slightly internally rotated and length and thickness of the ligament were measured. ALL was identified in 93.8% (150 out of 160) and in 92.5% (148 out of 160) of the knees by Evaluator 1 and Evaluator 2, respectively. Interobserver agreement was substantial to almost perfect for the visualization of the ALL ( =0.90) and for measurements of its length (ICC = 0.83), and strong for measurements of its thickness (ICC = 0.75). In our study on healthy subjects, ALL has been visualized with a high rate of reproducibility. Further studies are needed to see if US may be a reliable and reproducible diagnostic tool in patients with traumatic or degenerative knee disorders. II, evidence obtained from cohort study.

Macular thickness in healthy subjects and diabetics without diabetic macular edema

Purpose: To compare macular thickness values in normal subjects and diabetic patients without diabetic macular edema (DME) using optical coherence tomography (OCT). Methods :comparative prospective case control study was conducted on 150 eyes with varying stages of diabetic retinopathy compared with 50 normal control. We used the Topcon,3D OCT-2000 machine to perform the fast macular scan which gives 3 concentric circles : 1 , 3 and 5 mm. centered on the fovea . The mean ± standard deviation of macular thickness by area in these eyes were analyzed and compared. Results: OCT findings demonstrated that the macula in the diabetic patients with no diabetic retinopathy group was significantly thinner than that of the control group with mean (233.34±29.15) and (221.38±24.26) respectively. In addition, our findings showed that the macular thickness with mean (221.38±24.26) ,(231.30±29.34) and (256.48 ±39.62)gradually increased with the duration of DM with mean (5.48±4.39) ,(13.96±4.93) and (14.70±4.17) respectively probably because of an increase in vascular permeability in the diabetic retinas . Conclusion: OCT will allow the detection of early changes and designing a personalized, noninvasive treatment .the role of neurodegeneration in the pathogenesis of DR is a solid basis for proposing neuroprotection as an effective strategy for preventing or arresting DR.

Relationship Between Retinal Perfusion and Retinal Thickness in Healthy Subjects: An Optical Coherence Tomography Angiography Study.

PurposeTo investigate the relationship between retinal perfusion and retinal thickness in the peripapillary and macular areas of healthy subjects.MethodsUsing spectral-domain optic coherence tomography and split-spectrum amplitude decorrelation angiography (SSADA) algorithm, retinal perfusion and retinal thicknesses in the macular and peripapillary areas were measured in healthy volunteers, and correlations among these variables were analyzed.ResultsOverall, 64 subjects (121 eyes) including 28 males and 36 females with a mean ± SD age of 38 ± 13 years participated. Linear mixed-models showed that vessel area density was significantly correlated with the inner retinal thickness (from the inner limiting membrane to the outer border of the inner nucleus layer; P < 0.05), but not with the thickness of the full retina (P > 0.05) in the parafoveal area. The area of the foveal capillary-free zone was negatively correlated with the inner and full foveal thicknesses (all P < 0.001). In the peripapillary area, the vessel area density was positively correlated with the thickness of the retinal nerve fiber layer (P < 0.001).ConclusionsIn healthy subjects, retinal perfusion in small vessels was closely correlated with the thickness of the inner retinal layers in both the macular and peripapillary areas.

CHOROIDAL THICKNESS IN RELATION TO ETHNICITY MEASURED USING ENHANCED DEPTH IMAGING OPTICAL COHERENCE TOMOGRAPHY.

To investigate the posterior choroidal thickness in healthy subjects of three different ethnicities. In this prospective cross-sectional study, the choroidal thickness of 88 individuals (176 eyes) was measured using enhanced depth imaging-spectral domain optical coherence tomography. Subfoveal choroidal thickness was measured between the retinal pigment epithelium-Bruch membrane complex and chorioscleral interface. Nasal, temporal, superior, and inferior choroidal thicknesses at 0.5, 1.5, and 3.0 mm locations from the fovea were evaluated as well. Males and females were perfectly matched by number in all groups. The mean age of the entire study population was 27.43 ± 1 years. Mean subfoveal choroidal thicknesses of whites, Africans, Asians, and entire study population were 403.62 ± 37.4 μm, 372.47 ± 31.4 μm, 383.64 ± 40 μm, 386.64 ± 10.5 μm, respectively. Mean spherical error of the entire study population was -1.2685 diopter. Whites had the longest eyes on average 24.17 mm > 24.08 mm (Africans) > 23.86 mm (Asians), with the statistical mean of 24.04 mm for the entire study population. Subfoveal choroidal thickness was not significantly correlated with ethnicity in either ethnic group (P > 0.05). Subfoveal choroid thinned by 2.51 μm per 1 year increase in age (P = 0.282). Subfoveal choroidal thickness and sex were not significantly correlated to (P = 0.402). Subfoveal choroidal thickness was in strong negative correlation only with refractive error (P = 0.01) and axial length (P = 0.008). The intereye difference in subfoveal choroidal thickness was not statistically significant (P = 0.845). Enhanced depth imaging-spectral domain optical coherence tomography is a productive imaging method to study the choroidal thickness. Subfoveal choroidal thickness is not significantly correlated with ethnicity. The study reproduced previously found relations between thinner choroids and longer axial lengths, and increasing myopic refraction and showed no significant associations between subfoveal choroidal thickness and age and sex. Either the right or left eye can be used in future studies.

Evaluation of extensor digitorum brevis thickness in healthy subjects: A comparative analysis of nerve conduction studies and ultrasound scans

Objectives(1) To evaluate the relationship between the thickness and compound muscle action potential (CMAP) of the extensor digitorum brevis (EDB) muscle; (2) to obtain reference values for distal lower extremity muscle thickness as a possible measure of peripheral neuropathy; and (3) to evaluate various factors associated with unexplained EDB atrophy. MethodsWe measured the thickness of EDB, abductor hallucis brevis (AHB) and tibialis anterior (TA) muscles in 80 healthy volunteers with ultrasound and assessed EDB CMAP with fibular nerve stimulation. Two foot muscle-associated lifestyle factors were assessed and sociodemographic information was collected. ResultsA significant correlation was observed between the amplitude of the fibular nerve CMAP and EDB thickness. The thickness of each of the three muscles was greater in men compared to women. EDB thickness decreased significantly with age although the thicknesses of the AHB and TA muscles were not correlated with age. ConclusionsEDB thickness was closely associated with fibular nerve CMAP but with less variation and differed among groups by age and sex; it was not associated with lifestyle factors. SignificanceThe ability to obtain this measure painlessly with ultrasound and its low variation recommend it as a potentially useful complementary measure of distal neuromuscular function.

Influence of disc-fovea angle and retinal blood vessels on interindividual variability of circumpapillary retinal nerve fibre layer

BackgroundTo assess whether intersubject variability of circumpapillary retinal nerve fibre layer (RNFL) thickness in healthy subjects acquired with spectral domain optical coherence tomography (SD-OCT) can be reduced by considering the...

Multivariate Model of the Intersubject Variability of the Retinal Nerve Fiber Layer Thickness in Healthy Subjects.

We present and validate a multivariate model that partially compensates for retinal nerve fiber layer (RNFL) intersubject variability. A total of 202 healthy volunteers randomly attributed to a training (TS) and a validation (VS) sample underwent complete ophthalmic examination, including Fourier-domain optical coherence tomography (FD-OCT). We acquired FD-OCT data centered at the optic disc (OD) and the macula. Two-dimensional (2D) projection images were computed and registered, to determine the distance between fovea and OD centers (FD) and their respective angle (FA). Retinal vessels were automatically segmented in the projection images and used to calculate the circumpapillary retinal vessel density (RVD) profile. Using the TS, a multivariate model was calculated for each of 256 sectors of the RNFL, including OD ratio, orientation and area, RVD, FD, FA, age, and refractive error. Model selection was based on Akaike Information Criteria. The compensation effect was determined for 12 clock hour sectors, comparing the coefficients of variation (CoV) of measured and model-compensated RNFL thicknesses. The model then was applied to the VS, and CoV was calculated. The R value for the multivariate model was, on average 0.57 (max = 0.68). Compensation reduced the CoV on average by 18%, both for the TS and VS (up to 23% and 29%), respectively. We have developed and validated a comprehensive multivariate model that may be used to create a narrower range of normative RNFL data, which could improve diagnostic separation between early glaucoma and healthy subjects. This, however, remains to be demonstrated in future studies.

Ultrasound imaging of the diagonal dimension of the deep cervical flexor muscles: A reliability study on healthy subjects

The purpose of this study is to assess the reliability of a new ultrasound imaging (USI) parameter and procedure for the evaluation of the size of the deep cervical flexor (DCF) muscles. Thirty-one healthy male subjects (21.6±2.5 years old) participated in this study. Two images of the diagonal dimension (DD) of the DCF of the subjects, at 1.5 fingerbreadths below the laryngeal prominence of the thyroid cartilage in a relaxed state, were taken on separate days with a 1-week interval. The intraclass correlation coefficient between the days was 0.82 (95% confidence interval, 0.65-0.91). The standard error of measurement and minimal detectable change were 0.8mm and 2.1mm, respectively. The results indicated that the DD may be used as a reliable USI parameter to measure the DCF thickness in healthy subjects.

Effects of a tear supplement containing hyaluronic acid (HA) on tear film thickness in healthy subjects

AbstractPurpose We have recently introduced a new technique for the measurement of tear film thickness (TFT) using ultra‐high resolution optical coherence tomography (OCT) in humans. In the present study we hypothesized that the effect of a hyaluronic acid (HA) containing lubricant on TFT can be evaluated using this technique after single instillation.Methods 16 healthy volunteers were included into the present study. The design was randomized, double‐masked and placebo controlled. Subjects randomly received in one eye HA‐containing eye drops (0.15%, Olixia®, Croma Pharma, Austria) and in the other eye NaCl 0.9%. Measurement of TFT was performed at baseline and thereafter every 10 minutes until 60 minutes after start of instillation. A repeated measures ANOVA model was employed to study statistically significant differences.Results 8 female and 8 male subjects with a mean age of 26.8±4.8 years were included in this study. Baseline TFT was 5.0±0.5 μm in placebo and 4.8±0.5 μm in HA treated eyes. A significant effect of HA containing eyedrops on TFT was seen over time (p=0.014). 10 minutes after instillation TFT increased to 5.5±0.8 μm in the HA containing eyedrops and remained almost stable in the placebo group (5.1±0.8 μm). Post hoc analysis revealed that TFT was increased up to 30 minutes after instillation and then returned to baseline.Conclusion The results of the present study indicate that HA containing eyedrops increase pre‐corneal TFT for as long as 30 minutes in healthy subjects. This effect is not seen with NaCl administration. Our data also indicate that measurement of TFT with ultra‐high resolution OCT is a promising technique to study residence time of eye drops at the ocular surface.

Diurnal variation of retinal thickness in healthy subjects.

To investigate diurnal fluctuations in retinal thickness using spectral domain optical coherence tomography (SD-OCT). Spectralis SD-OCT was used to obtain data from the right eye of 21 healthy subjects (mean age, 31.3 years) at 7 AM, 1 PM, and 7 PM. For each eye, a full peripapillary retinal nerve fiber layer circular scan and a 19-line horizontal raster scan (6- by 6-mm area) centered on the fovea were performed. Retinal nerve fiber layer thickness was greater at 7 AM or 1 PM than at 7 PM for nasal (79.1 μm [1 PM] vs. 77.6 [7 PM]; p = 0.024), inferior (134.1 [7 AM] vs. 131.9 [7 PM]; p = 0.009), and inferonasal (115.2 [7 AM] vs. 115.6 [1 PM] vs. 112.4 [7 PM]; p < 0.001) subfields. Macular thickness was greater at 7 AM than at 7 PM for inferior 6 mm (290.2 μm [7 AM] vs. 287.8 [7 PM]; p < 0.001) ETDRS (Early Treatment Diabetic Retinopathy Study) subfield. Macular volume was greater at 7 AM than at 7 PM for nasal 3 mm (0.541 mm vs. 0.538; p = 0.028) and inferior 6 mm (1.538 vs. 1.525; p < 0.001) ETDRS subfields. The remaining studied areas did not show any significant change throughout the day. The Spectralis SD-OCT retinal thickness measurements showed a small but statistically significant diurnal variation in nasal and inferior subfields toward smaller values in the evening. However, the overall change is close to the instrument's resolution and repeatability.