Disc-fovea Angle Research Articles

Validity and Reliability of 2 Cirrus Optical Coherence Tomography Procedures for Measuring Objective Ocular Torsion

Torsional eye position by the disc-fovea angle (DFA) is a relevant objective parameter in vertical strabismus. DFA measurement with optical coherence tomography (OCT) has proven to be a good alternative to the gold standard measurement in fundus photography. Our study aims to analyze the validity and reliability of 2 undescribed Cirrus high-definition OCT (HD-OCT; Carl Zeiss Meditec) methods that offer clinical advantages for measuring objective cycloposition in normal patients compared with Spectralis spectral-domain OCT (Heidelberg Engineering) and the reference method. Prospective validity and reliability analysis. Objective cycloposition by means of the DFA was measured in the right eyes of 59 binocularly normal individuals attending the ophthalmology service of a medical institution. DFA was obtained by fundus photography (gold standard), FoDi software of Spectralis spectral-domain OCT, HD 1 line scan of Cirrus HD-OCT, and macular cube of Cirrus HD-OCT (fundus, FoDi, line, and cube methods, respectively). Measurements were performed 3 times for each method and the patient was repositioned and realigned between captures. Posterior manual quantification was made by 2 observers with external protractor software for the fundus and cube methods. The 3 OCT methods showed and excellent agreement with fundus photography (ICC 0.83-0.84) with no significant differences comparing mean values (P = .36 for fundus-FoDi, P = .09 for fundus-line, and P = .09 for fundus-cube). Absolute differences between methods were 1.5°. All methods showed excellent reliability (ICC 0.92 for FoDi, 0.91 for line, 0.92 for cube, and 0.91 for fundus). The minimal detectable change was lower than 3° and the absolute difference between repeated measurements was 1° for all methods. Interrater reliability was excellent for methods requiring manual quantification (ICC 0.98 for cube, ICC 0.94 for fundus). Measurement of the DFA by Cirrus HD-OCT methods in normal patients was a valid and reliable alternative for the cycloposition assessment. Among the methods, the Cirrus OCT HD 1 line improved clinical performance due to the simplicity and speed of measurement, with no need to export the image for quantification.

Objective excyclotorsion increases with aging in adults

ABSTRACT Introduction It has been reported that the disc-fovea angle (DFA), a measure of objective cyclotorsion, increases with age. DFA was measured in three age groups of adults and the effects of age, sex, and laterality on DFA is reported. Methods and Subjects A retrospective study was performed on patients who had a glaucoma checkup or who visited for suspected cataract, who underwent fundus photography between 2013 and 2021. Patients with visual acuity <0.7, axial length >27 mm, strabismus or ocular diseases affecting fusion were excluded. DFA was measured from digital fundus photographs obtained from 249 participants comprising three age groups (group I, 44.4 ± 0.5 years, n = 58; group II, 63.7 ± 3.6 years, n = 129; group III, 81.0 ± 3.8 years, n = 62). The sum of right- and left-eye DFAs is named as total DFA. Results Dunnett’s post-hoc test after ANOVA showed that the left-eye DFA and total DFA of group III were significantly larger than those of group I (p = .01 and p < .01, respectively). Total DFA of female participant (15.6 ± 4.7°, n = 168) was significantly larger than that of male participant (13.9 ± 4.3°, n = 81) (p < .01). The DFA of the left eye (8.2 ± 3.5°, n = 249) was significantly larger than that of the right eye (6.8 ± 3.3°, n = 249) (p < .001). Group III was subdivided based on eye dominance (right eye dominance, n = 36; left eye dominance, n = 13; NA, n = 13). The DFA in the nondominant eye (9.7 ± 4.6°) was significantly larger than that in the dominant eye (7.4 ± 3.7°) (p < .01). Discussion This study found a slight increase of DFA with age. Furthermore, DFA in female or DFA in the left-eye was larger than DFA in male or in the right-eye.

Automated measurement of the disc-fovea angle based on DeepLabv3.

PurposeTo assess the value of automatic disc-fovea angle (DFA) measurement using the DeepLabv3+ segmentation model.MethodsA total of 682 normal fundus image datasets were collected from the Eye Hospital of Nanjing Medical University. The following parts of the images were labeled and subsequently reviewed by ophthalmologists: optic disc center, macular center, optic disc area, and virtual macular area. A total of 477 normal fundus images were used to train DeepLabv3+, U-Net, and PSPNet model, which were used to obtain the optic disc area and virtual macular area. Then, the coordinates of the optic disc center and macular center were obstained by using the minimum outer circle technique. Finally the DFA was calculated.ResultsIn this study, 205 normal fundus images were used to test the model. The experimental results showed that the errors in automatic DFA measurement using DeepLabv3+, U-Net, and PSPNet segmentation models were 0.76°, 1.4°, and 2.12°, respectively. The mean intersection over union (MIoU), mean pixel accuracy (MPA), average error in the center of the optic disc, and average error in the center of the virtual macula obstained by using DeepLabv3+ model was 94.77%, 97.32%, 10.94 pixels, and 13.44 pixels, respectively. The automatic DFA measurement using DeepLabv3+ got the less error than the errors that using the other segmentation models. Therefore, the DeepLabv3+ segmentation model was finally chosen to measure DFA automatically.ConclusionsThe DeepLabv3+ segmentation model -based automatic segmentation techniques can produce accurate and rapid DFA measurements.

Comparison of subjective cyclofusion ranges and objective ocular torsion in normal participants according to age.

To investigate the relationship between subjective cyclofusion ranges and objective ocular torsion in normal participants according to age. This cross-sectional study included 120 participants aged ≥ 20years with no ocular diseases. The subjective cyclofusion ranges were measured centrifugally and centripetally in the direction of excyclotorsion and incyclotorsion, respectively, concurrently with rotational diplopia production by rotation using synoptophore. Disc fovea angle (DFA) was defined as the angle formed by two lines: a line passing through the center of the optic nerve papilla and fovea and a horizontal line passing through the center of gravity of the optic papilla using fundus photographs. The participants were aged 49.1 ± 17.7years. The total cyclofusion centrifugal (sum of extorsion and intorsion) and centripetal ranges were 10.9 ± 2.2° and 7.2 ± 1.8°, respectively, both of which decreased in participants in their 60s and 70s (p < 0.01). The DFA was - 7.0 ± 3.4° in the right eye (- : excyclo, + : incyclo) and - 8.0 ± 3.2° in the left, which was associated with age (p < 0.001). The correlation between the DFA and centrifugal (r = - 0.13, p = 0.16) and centripetal (r = - 0.002, p = 0.99) cyclofusion ranges of extorsion was not significantly different. The centrifugal (r = 0.37, p < 0.001) and centripetal (r = 0.40, p < 0.001) cyclofusion ranges of intorsion were positively correlated. Subjective cyclofusion ranges decreased in both extorsion and intorsion in the elderly. Objective ocular torsion showed excyclotorsion with age. When strabismus surgery is performed in elderly patients with torsional strabismus, the decrease in subjective cyclofusion ranges should be considered.

Minimal detectable change of the disc‐fovea angle for ocular torsion assessment

AbstractPurposeThe disc‐fovea angle (DFA) is used as a relevant indicator of ocular torsion change in cyclovertical strabismus. However, interpretation of the variation in time must differentiate whether a real change has occurred or if the disparity is due to random measurement error. The aim of the study was to obtain the minimal detectable change (MDC) of the DFA. It represents the minimal variation between two measurements that may be considered a real ocular torsion change.MethodsA prospective cross‐sectional study was conducted in San Carlos Clinical Hospital of Madrid, Spain. Sixty healthy right eyes from 60 patients (31 men and 29 women) were recruited. Three digital fundus photographs were obtained, and between measurements, the patient moved their head away from the head support and then returned. Two observers quantified the DFA with software designed with MATLAB. Test‐retest and interrater reliability were calculated.ResultsMean participant age was 56.1 years (SD 16.6, range 25–85). Mean DFA was 8.1° (SD 3.5, range 1.3–18.5). Test‐retest reliability for Observer 1 (Ob1), Observer 2 (Ob2) and interrater reliability were excellent (ICC 0.80, 0.83 and 0.95, respectively). Precision was 2.9° (Ob1) and 3.0° (Ob2), and the MDC95 was 4.1° (Ob1) and 4.2° (Ob2). Bland‐Altman analysis revealed an absence of bias and a homoscedastic distribution of the differences.ConclusionsThe MDC of the DFA in fundus photography was 4°, which represents the minimal change that may be considered a real change in ocular torsion. This result may improve the interpretation of ocular torsion changes in surgery and clinical scenarios.

Neural Network-Based Retinal Nerve Fiber Layer Profile Compensation for Glaucoma Diagnosis in Myopia: Model Development and Validation.

BackgroundDue to the axial elongation–associated changes in the optic nerve and retina in high myopia, traditional methods like optic disc evaluation and visual field are not able to correctly differentiate glaucomatous lesions. It has been clinically challenging to detect glaucoma in highly myopic eyes.ObjectiveThis study aimed to develop a neural network to adjust for the dependence of the peripapillary retinal nerve fiber layer (RNFL) thickness (RNFLT) profile on age, gender, and ocular biometric parameters and to evaluate the network’s performance for glaucoma diagnosis, especially in high myopia.MethodsRNFLT with 768 points on the circumferential 3.4-mm scan was measured using spectral-domain optical coherence tomography. A fully connected network and a radial basis function network were trained for vertical (scaling) and horizontal (shift) transformation of the RNFLT profile with adjustment for age, axial length (AL), disc-fovea angle, and distance in a test group of 2223 nonglaucomatous eyes. The performance of RNFLT compensation was evaluated in an independent group of 254 glaucoma patients and 254 nonglaucomatous participants.ResultsBy applying the RNFL compensation algorithm, the area under the receiver operating characteristic curve for detecting glaucoma increased from 0.70 to 0.84, from 0.75 to 0.89, from 0.77 to 0.89, and from 0.78 to 0.87 for eyes in the highest 10% percentile subgroup of the AL distribution (mean 26.0, SD 0.9 mm), highest 20% percentile subgroup of the AL distribution (mean 25.3, SD 1.0 mm), highest 30% percentile subgroup of the AL distribution (mean 24.9, SD 1.0 mm), and any AL (mean 23.5, SD 1.2 mm), respectively, in comparison with unadjusted RNFLT. The difference between uncompensated and compensated RNFLT values increased with longer axial length, with enlargement of 19.8%, 18.9%, 16.2%, and 11.3% in the highest 10% percentile subgroup, highest 20% percentile subgroup, highest 30% percentile subgroup, and all eyes, respectively.ConclusionsIn a population-based study sample, an algorithm-based adjustment for age, gender, and ocular biometric parameters improved the diagnostic precision of the RNFLT profile for glaucoma detection particularly in myopic and highly myopic eyes.

Location of Parapapillary Gamma Zone and Vertical Fovea Location. The Beijing Eye Study 2011.

PurposeTo assess the spatial relationship between the locations of the parapapillary gamma zone and the fovea.MethodsIn a non-glaucomatous subgroup of the population-based Beijing Eye Study population, we measured the mean angle between the optic disc–fovea line and the horizontal (disc–fovea angle), the vertical distance of the fovea from the horizontal through the optic disc center (fovea vertical distance), and the location and width of the widest part of parapapillary gamma zone.ResultsThe study included 203 individuals (203 eyes; mean axial length, 24.4 ± 1.5 mm; range, 22.03–28.87 mm). The widest gamma zone part was located most often temporal horizontally (51.7%), then inferiorly (43.8%), superiorly (2.5%), and nasally (2.0%). The disc–fovea angle (mean, 7.50° ± 4.00°; range, –6.30° to –23.25°) was significantly higher (P = 0.003; i.e., fovea located more inferiorly) in eyes with the widest gamma zone inferiorly (8.46° ± 4.37°) than in eyes with the widest gamma zone temporally (6.71° ± 3.46°) and in eyes with the widest gamma zone temporally, superiorly, or nasally combined (6.75° ± 3.53°; P = 0.003). The fovea vertical distance (mean, 0.65 ± 0.33 mm; range, –0.20 to 1.67 mm) was longer (P = 0.001; i.e., fovea located more inferiorly) in eyes with the widest gamma zone inferiorly (0.73 ± 0.33 mm) than in eyes with the widest gamma zone temporally (0.58 ± 0.30 mm) and in eyes with a temporal, superior, or nasal gamma zone combined (0.58 ± 0.31 mm; P = 0.001). The fovea vertical distance increased (multivariate analysis) with the widest gamma zone location inferiorly (β = 0.25; P = 0.001) and wider width of the gamma zone (β = 0.19; P = 0.01).ConclusionsAn inferior fovea location is associated with a wider inferior gamma zone and vice versa, supporting the notion of an inferior shifting of Bruch's membrane as the cause for an inferior gamma zone.

Thinner temporal peripapillary retinal nerve fibre layer in Stargardt disease detected by optical coherence tomography

PurposeTo evaluate peripapillary retinal nerve fibre layer (RNFL) thickness measured by spectral domain optical coherence tomography (OCT) in patients with Stargardt disease (STGD).MethodsA cross-sectional, monocentric, observational case-control study. Twenty patients (39 eyes) with ABCA4 mutations graded according to the Fishman STGD classification were included. RNFL measurement was performed using Heidelberg Spectralis SD-OCT. RNFL thickness in STGD patients was compared to age-matched data of healthy individuals provided by the device’s manufacturer. A manual readjustment of the optic disc-fovea angle was performed when needed.ResultsThe mean age at first diagnosis of STGD was 22.9 years (range 9 to 50) and 39.1 years (range 18 to 74) at the time of examination. Thirty-nine percent of eyes (15 eyes) needed manual adjustment of the optic disc-fovea angle due to malfixation of the patients during OCT. The temporal quadrant corresponding to the macula showed a RNFL 16% thinner than controls (mean − 12 μm, 95%CI − 9 to −15 μm). However, global RNFL thickness did not differ from controls due to increased RNFL thickness of 12% in the nasal sectors. Duration and stage of STGD were not correlated to thinner RNFL.ConclusionSTGD seems to be associated with thinner peripapillary RNFL in the sector of axons projecting to the degenerated macular area. It is yet unclear as to whether this results from anterograde transneuronal degeneration of direct injury to retinal ganglion cells.

Range of forced cyclorotation in superior oblique palsy and V-pattern strabismus.

To quantify a passive range of cyclorotation using a smartphone application and evaluate its associations with fundus torsion and rectus muscle cyclorotation in superior oblique palsy (SOP) and V-pattern strabismus. Fifty-two patients showing overelevation in adduction (30 with congenital SOP and 22 with V-pattern strabismus) underwent forced cyclorotation on the photographs. A photograph of the globe was taken in maximally excyclorotated and incyclorotated positions after marking at the 6 and 12 o'clock limbus under general anaesthesia, and the rotational alignment of these markings was read using the toriCAM application. The degrees of forced cyclorotation were compared between the two groups. Disc-fovea angle on fundus photographs and rectus muscle cyclorotation in the coronal view on orbital computed tomography were correlated with the range of forced excyclorotation. The range of forced excyclorotation was greater in V-pattern strabismus than that in SOP (58.5° vs. 46.8°, p < 0.001), whereas the ranges of incyclorotation were similar between the two groups (39.0° vs. 39.0°, p = 0.543). Regression analysis revealed a significant increase in the range of excyclorotation with the degree of rectus muscle excyclorotation, after accounting for age and angle of hypertropia (r2 = 0.475, p = 0.001). The range of excyclorotation did not correlate with the amount of fundus extorsion and grade of overelevation in adduction. The range of excyclorotation was correlated with the rectus muscle excyclorotation in these populations, suggesting that the results from this forced cyclorotation test may reflect orbital alignment and oblique muscle status.

Validity and Reliability of Semiautomatic Ocular Cycloposition Measurement With Spectralis Optical Coherence Tomography

Disc-fovea angle determined by fundus photography (P-DFA) is considered the gold standard for cycloposition assessment. Fovea-to-disc alignment (FoDi) software of the spectral-domain optical coherence tomography (SD-OCT) (Spectralis) also measures the DFA (O-DFA) based on subject fixation and offers important clinical advantages. This study aimed to analyze the validity and reliability of measuring cycloposition using OCT and to determine its performance in eyes with poor foveal definition. Validity and reliability analysis. In 60 eyes with normal foveal definition and 32 eyes with poorly defined fovea, ocular cycloposition was assessed by 2 observers using 5 fundus photographs and 5 FoDi analyses each. Patients were repositioned after every capture. Cycloposition assessed by O-DFA was 7.6 ± 3.5-degrees, and P-DFA was 7.9 ± 3.8-degrees. The concordance between methods was good (intraclass correlation coefficient [ICC], 0.71), with absolute differences ranging from zero to 4-degrees in 85% of the subjects. The precision was 1.4-degrees for O-DFA and 3.0-degrees for P-DFA. Repeatability and reproducibility were excellent in both techniques. In the group of patients with poor foveal definition, the precision of P-DFA changed from 3.0-degrees to 4.8-degrees, whereas the O-DFA remained stable. OCT had a good agreement with the fundus photography method. O-DFA showed better precision than P-DFA. O-DFA repeatability and reproducibility were excellent and unconditioned by foveal status.

Disc-fovea Angle Is Associated With Visual Field Defect Location in Patients With Glaucoma.

The current study showed that glaucomatous eyes from patients with central visual field defects presented less negative disc-fovea angle compared with patients with peripheral defects. The purpose of this study was to investigate the relationship between disc-fovea angle and visual field defect location in patients with glaucoma. This was a cross-sectional study including glaucoma patients divided into isolated central and isolated peripheral scotoma groups. The main outcome measure was disc-fovea angle measurement between groups. Secondary outcomes included disc-fovea distance, vertical disc diameter, and fovea vertical deviation. We included 50 glaucoma patients (50 eyes; 27 with central scotoma and 23 with peripheral scotoma). Mean deviation from visual fields was -3.05±1.67 and -2.95±1.49 dB (P=0.829) (central and peripheral scotoma groups, respectively). We found that eyes in the central group had lower values of disc-fovea angle (-5.85±2.67 vs. -7.97±2.26 degrees, P=0.004), shorter disc-fovea distance (4.38±0.70 vs. 4.98±0.78 mm, P=0.006), and shorter fovea vertical deviation (-0.43±0.19 vs. -0.68±0.22 mm, P<0.001) compared with eyes in the peripheral group. This study showed an association between disc-fovea angle and central visual field defects in patients with glaucoma. Our findings suggest that eyes with a less negative disc-fovea angle should undergo a more careful investigation of the central visual field, even at early stages of the disease.

Homonymous hemiatrophy of ganglion cell layer from retrochiasmal lesions in the visual pathway.

To determine the temporal evolution, morphology, and frequency of macular ganglion cell atrophy in patients with retrochiasmal lesions of the visual pathway. In a consecutive retrospective case series, we identified 47 patients with homonymous hemianopia and accessible macular optical coherence tomography scans. We estimated the time of lesion onset and the location of the lesion within the afferent visual pathway. Using semiautomatic layer segmentation, we determined ganglion cell layer thickness in areas projecting to the side of the retrochiasmal lesion and compared it with ganglion cell layer thickness on the healthy side. We found that retrochiasmal lesions at any level may be associated with an atrophy of ganglion cells. This atrophy respects the vertical midline through the fovea and thus the anatomic separation of the nasal and temporal visual field. The vertical line separating the affected from the unaffected side has significantly less tilt as compared with the disc-fovea angle. Lesions of the optic tract are associated with earlier macular ganglion cell atrophy than retrogeniculate lesions. Macular ganglion cell atrophy may be present in cases with normal peripapillary nerve fiber layer analysis and vice versa. Macular ganglion cell layer thickness shows a topographic hemiatrophy in retrochiasmal lesions, which manifests earlier for tract lesions than for retrogeniculate lesions. This additional examination of ganglion cell homonymous hemiatrophy has a higher sensitivity in detecting retrograde transsynaptic degeneration than the analysis of the peripapillary nerve fiber layer alone.

This issue of Acta

This issue of Acta

Effects of the Relative Positioning between the Disc-Fovea Angle and Localized Optic Disc Defects on the 10-2 Visual Field Results in Glaucoma

To investigate the effects of the foveal position relative to the optic disc on the 10-2 visual field (VF) results of glaucoma patients with localized inferotemporal neuroretinal rim defects (ITD). Cross-sectional study. Fifty-seven eyes of 35 open-angle glaucoma (OAG) patients were included and divided into two groups based upon the presence (18 eyes) or not (39 eyes) of ITD. Three different parameters obtained from a spectral domain optic coherence tomography (sdOCT) [disc-fovea angle (DFA), fovea vertical deviation (FVD) from midline, and the angular difference between the ITD border and the DFA (DAD)] were tested for their relationship with four 10-2 VF sectors: superior hemifield, superior edge, nasal edge, and superonasal arcuate. These relationships were tested with regression analyses with linear mixed effects models and random intercepts. Influences of DFA, FVD, and DAD on 10-2 VF sectors. Mean (±SD) values of DFA, FVD, and DAD were respectively: -5.05° ± 4.40°, -1346.6 um ± 1609.0 um, and 43.30° ± 17.33°. After adjustment for multiple comparisons, both FVD and DAD, but not DFA, were significantly associated with the severity of defects on the predefined VF sectors. Larger DAD values (third tertile: 54°-77°) showed higher coefficient estimate for the nasal edge sector sensitivities. The vertical foveal location and its position relative to the ITD was associated with loss of sensitivity at 10-2 VF locations in the superior hemifield. This association was significant but weak and was not seen using other conventional parameters that describe foveal position relative to the optic disc on sdOCT.

Age-related change and sex difference over 60s in disc-fovea angle in Japanese population: the Nagahama Study.

To analyse the disc-fovea angle (DFA) by age group and to compare sex differences in each age group in a large cohort population. This community-based cross-sectional cohort study included 9682 eyes of 9682 volunteers (aged 30-75years). We measured the DFA, which is the angle between a horizontal line and a line connecting the fovea with the centroid of an optic disc on fundus photographs of the right eye. We manually marked the fovea and surrounded the optic disc. The centroid of an optic disc and the DFA was automatically calculated using originally developed software. We compared the DFA between age groups in 10-year increments and investigated sex differences of DFA in each age group. Overall mean DFA was 6.32±3.53°. The DFA of older subjects was significantly larger than that of younger subjects (p<0.001). The DFA of women was larger than that of men in their 60s and 70s (p<0.001 for both), but not in subjects in their 30s, 40s and 50s. Larger DFA in women than in men in their 60s and 70s suggests the possibility that age-related excyclo-shift occurs more easily in postmenopausal women compared to men of the same age.

Application of the ISNT rules on retinal nerve fibre layer thickness and neuroretinal rim area in healthy myopic eyes.

We determined the applicability of inferior>superior>nasal>temporal (ISNT) rules on retinal nerve fibre layer (RNFL) thickness and rim area and evaluated the impact of various ocular factors on the performance of the ISNT rules in healthy myopic eyes. A total of 138 eyes from 138 healthy myopic subjects were included in this cross-sectional observational study. The peripapillary RNFL and optic disc in each eye were imaged with Cirrus HD optical coherence tomography (OCT) and Heidelberg Retina Tomograph II (HRT2), respectively. The performance of the inferior>superior (IS), inferior>superior>nasal>temporal (IST) and ISNT rules on RNFL thickness and rim area was determined and compared between low-to-moderate myopia and high myopia. The effects of ocular factors [including axial length, disc area, disc tilt, disc torsion, disc-fovea angle (DFA) and retina artery angle] on the performance of ISNT rules were evaluated with logistic regression analysis. The mean axial length and refractive error were 25.57±1.09mm (range, 22.52-28.77mm) and -5.12±2.30D [range, -9.63 to -0.50dioptres (D)], respectively. Sixty-three per cent of the healthy eyes were compliant with the ISNT rule on rim area, while ISNT rule on RNFL thickness was followed in only 11.6% of the included eyes. For rim area, smaller disc area was significantly associated with increased compliance of the IS rule (odds ratio: 0.46, p=0.039), IST rule (odds ratio: 0.46, p=0.037) and ISNT rule (odds ratio: 0.44, p=0.030). For RNFL thickness, greater DFA was significantly associated with increased compliance of the IS and IST rules (odds ratio: 1.30, p<0.001; odds ratio: 1.19, p=0.006, respectively). In healthy myopic subjects, 88.4% and 37% of eyes did not comply with the ISNT rule on RNFL thickness and rim area, respectively. Due to significant low compliance in healthy eyes, the ISNT rule and its variants have limited potential utility in diagnosing glaucoma in myopic subjects.

The influence of ocular sighting dominance on Fundus torsion in patients with unilateral congenital superior oblique palsy.

The purpose of our study was to determine whether ocular sighting dominance may influence the ocular torsion in patients with unilateral congenital superior oblique palsy (UCSOP). This retrospective study included 22 UCSOP patients with radiologic evidence of unilateral superior oblique muscle hypoplasia on orbital magnetic resonance imaging and 66 healthy individuals with normal ocular motility as controls. Ocular torsion was assessed both quantitatively and qualitatively using digital fundus photography. The disc-fovea angle (DFA) was measured quantitatively using image software on a computer screen. All fundus photographs were qualitatively graded as normal torsion, extorsion, or intorsion in all subjects, based on the location of the optic disc relative to the fovea, according to the Bixenman and von Noorden's criteria. Ocular sighting dominance was assessed by the hole-in-the-card test and the pointing test. The Mann-Whitney U test and Fisher's exact test were used to determine the association between the ocular sighting dominance and the ocular torsion. The median DFA was significantly larger in the eyes of patients with UCSOP (9.1° in the paretic eyes and 9.3° in the non-paretic eyes) than the eyes of the control group (4.3°, p<0.001 for both). Ocular dominance tests displayed that, among 22 patients, 11 were paretic eye dominant and the other 11 were non-paretic eye dominant. The sighting-dominant eyes demonstrated significantly smaller median DFA than the non-dominant eyes (8.3° and 10.7°, respectively, p=0.033), regardless of which eyes were paretic. Ten eyes of ten patients had extorsion, none had intorsion, and all the eyes of remaining 12 patients had no abnormal torsion, qualitatively. All the eyes showing extorsion in fundus photography were non-dominant eyes, regardless of whether the eyes were paretic or non-paretic. Our findings illuminate the importance of considering ocular sighting dominance for properly assessing ocular torsion in patients with UCSOP. Ocular sighting dominance may have an influence on objective ocular torsion in a way that decreases the torsion in the dominant eye, thereby hindering the abnormal ocular torsion from appearing in that eye.

Horizontal and vertical optic disc rotation. The Beijing Eye Study.

PurposeTo measure the optic disc rotation around the vertical and horizontal disc axis and to evaluate associations with general and ocular parameters.DesignPopulation-based studyMethodsIn the Beijing Eye Study, 3468 participants (mean age:64.6±9.8 years; range:50–93 years) underwent an ophthalmological examination which included spectral-domain optical coherence tomography (OCT) with enhanced depth imaging. Using the OCT images, we determined the amount of the rotation of the optic disc (defined as Bruch´s membrane opening (BMO)) around the vertical axis and horizontal axis.ResultsOptic disc rotation measurements were available for 3037 (87.6%) individuals. In multivariate analysis, larger optic disc rotation around the vertical axis (range:-4.90° to 41.0°) was associated (regression coefficient r:0.27) with high axial myopia (axial length ≥26.5 mm) (P<0.001;standardized regression coefficient beta beta:0.09), longer disc-fovea distance (P = 0.001;beta:0.09) and wider parapapillary beta/gamma zone (P<0.001;beta0.12). Larger optic disc rotation around the horizontal axis (range:-7.10° to 26.4°) was associated (r:0.32) with high axial myopia (P = 0.001;beta:0.08), larger optic disc-fovea angle (P<0.001;beta:0.13), thinner superior nasal retinal nerve fiber layer (RNFL) thickness (P<0.001;beta:-0.19) and thicker inferior nasal RNFL thickness (P<0.001;beta:0.17).ConclusionsVertical optic disc rotation was associated with highly myopic axial elongation, increased disc-fovea distance and development or enlargement of parapapillary, Bruch´s membrane free, gamma zone, while macular Bruch´s membrane length is not affected. Horizontal optic disc rotation was associated with inferior dislocation of the fovea, in addition to a thinner superior nasal RNFL and thicker inferior nasal RNFL. The latter association may be taken into account in the interpretation of RNFL thickness profiles.

Normal values of otolith function tests and age-related changes

Objective:To explore the normal values of otolith function tests and agerelated changes in health volunteers.Method: One hundred and seventyone health volunteers were distributed to seven age groups, all subjects accepted otolith function tests, including fundus photography, static subjective visual vertical(SSVV), cervical vestibular evoked myogenic potential(cVEMP)and ocular vestibular evoked myogenic potential(oVEMP), the fundus photographs was used to measure the discfovea angle(DFA). DFA, SSVV and VEMPs were analyzed and compared among groups. Result: For DFA and SSVV,there were no significant differences either between different ages or between the two eyes in one individual（P>0.05）. For cVEMP, the detection rate declined with age over 60 years old（P<0.01）; the cVEMP threshold increased with every 20 years old(P<0.05); and the cVEMP amplitude decreased with every 10 years old(P<0.05),however, there was an exception that no significant difference was found between 41-50 years old and 51-60 years old groups（P=0.93）;the cVEMP P1 latency prolonged with age over 70 years old（P<0.01）.For oVEMP, the detection rate also declined with age over 60 years old（P<0.01）; the oVEMP threshold was lowest at the age less than 30 years old and the largest threshold was found at the age over 70 years old（P<0.01）; consistently, the oVEMP amplitude was found largest at the age less than 20 years old and lowest at the age over 60 years old(P<0.05).The P1 and N1 latencies were found significantly longer in the group of over 70 years old than other groups（P<0.01）.No significant difference was found between both sides in one individual for oVEMP threshold,amplitude or latency (P>0.05). Conclusion: In health volunteers,there were no obvious aged related changes in DFA and SSVV. However,the detection rate, threshold, amplitude and latency of cVEMP and oVEMP greatly changed with age.

Parapapillary Gamma Zone and Axial Elongation-Associated Optic Disc Rotation: The Beijing Eye Study.

The parapapillary gamma zone has been defined as the parapapillary region without Bruch's membrane. We examined which morphologic parameters are associated with the presence and size of the parapapillary gamma zone. Using fundus photographs and spectral-domain optical coherence tomographic images of the optic nerve head in the population-based Beijing Eye Study, we determined parapapillary gamma zone width, macular Bruch's membrane length, optic disc-fovea distance, the angle of horizontal optic disc rotation, the angle of vertical optic disc rotation, and the ratio of the vertical-to-horizontal disc diameter. The study included 2068 individuals with a mean age of 63.0 ± 9.0 years (range, 50-91 years), and mean axial length was 23.2 ± 1.0 mm (range, 18.96-28.87 mm). In multivariate analysis, larger width of parapapillary gamma zone was associated with more marked vertical optic disc rotation (P < 0.001; standardized correlation coefficient β, 0.15; nonstandardized correlation coefficient B, 0.02; 95% confidence interval [CI], 0.02, 0.03), more marked horizontal optic disc rotation (P = 0.02; β, 0.05; B, 0.01; 95% CI, 0.001, 0.01), longer axial length (P = 0.01; β, 0.07; B, 0.02; 95% CI, 0.01, 0.04), longer horizontal optic disc diameter (P = 0.02; β, 0.05; B, 0.06; 95% CI, 0.01, 0.12), longer disc-fovea distance (P < 0.001; β, 0.25; B, 0.22; 95% CI, 0.18, 0.27), higher degree of fundus tessellation (P = 0.03; β, 0.17; B, 0.04; 95% CI, 0.03, 0.0), and thinner subfoveal choroidal thickness (P < 0.001; β, -0.13; B, 0.000; 95% CI, -0.001, 0.000). Parapapillary gamma zone width was not significantly associated with macular Bruch's membrane length (P = 0.72), disc-fovea angle (P = 0.62), age (P = 0.62), or sex (P = 0.46). The parapapillary gamma zone was associated with an axial elongation-induced rotation of the optic disc mainly around the vertical disc axis, leading to a stretching of the temporal peripapillary scleral flange. Because macular Bruch's membrane length was independent of axial elongation, it leaves the temporal parapapillary region with an uncovered Bruch's membrane (i.e., parapapillary gamma zone develops).