The normal optic nerve head

Optical Coherence Tomography Angiography for the Differentiation of Glaucoma from Pituitary Macroadenoma Related Optic Disc Measurements

OBJECTIVE

To determine the potential of optical coherence tomography (OCT) and OCT angiography (OCTA) to distinguish between glaucoma and pituitary macroadenoma by optic disc appearance.

METHODS

This prospective case-control study comprised 31 patients: 23 with glaucoma (18 male, 5 female) and 8 with pituitary macroadenoma and chiasmatic compression (3 male, 5 female). The corresponding mean ages were 72.8 years (range 58-90) and 60.7 years (range 43-73). All participants underwent complete ophthalmological examination, spectral domain OCT and OCTA, and visual field testing. Clinical, imaging, and visual field results were compared between the groups.

RESULTS

On OCT analysis, the glaucoma group had relatively lower peripapillary retinal nerve fiber layer (RNFL) thickness (65.79 ± 15.46, 86.0 ± 11.37, respectively, P = .002) and lower rim area (1.00 ± 0.22 mm2 and 1.2 ± 0.15 mm2, respectively, P = .005). On OCTA, peripapillary vessel density was significantly lower in all quadrants in the glaucoma group. The significance of these between-group differences was maintained when patients were stratified by visual field mean deviation.

CONCLUSIONS

This is the first comparative analysis of optic disc morphology between glaucoma and pituitary macroadenoma using combined OCT and OCTA. The results yielded lower peripapillary RNFL thickness, lower rim area, and lower peripapillary vessel density in the glaucoma group. These parameters may aid in the initial differentiation between these two optic neuropathies.

Optic disc morphometry using spectral domain optical coherence tomography in a Nigerian population

PURPOSE

To assess morphological optic disc dimensions using spectral-domain optical coherence tomography (OCT) in a Nigerian population.

MATERIALS AND METHOD

Good quality SD-OCT scans of the optic disc of 147 eyes of 88 participants were selected, enrolled, and retrospectively reviewed. All subjects had optic nerve head and retinal nerve fibre layer OCT imaging, as well as analysis, done using the Topcon 3D OCT-1 Maestro®. The age, sex, and some OCT-generated optic disc dimensions namely disc area (DA), vertical disc diameter (VDD), horizontal disc diameter (HDD) were retrieved from the database and analyzed.

RESULTS

The mean age of the study subjects was 52.6±20.9 years with a range of 8-90 years; male to female ratio was 1:1.3. The right eye and left eye accounted for 75 and 72 of the 147 scans respectively. The mean DA, VDD, and HDD were 2.54 ± 0.48 mm2, 1926.5 ± 189.6 μm and 1673.9 ± 173.9 μm, respectively. Males had significantly larger DA than females (2.56 ± 0.53 mm2 vs 2.51 ± 0.44 mm2, p = 0.043). The mean DA and VDD of eyes of subjects aged 21-40 years were significantly higher compared to subjects aged 60 years and more (p = 0.008 and 0.001, respectively).

CONCLUSION

The mean optic disc area and diameters are larger than those reported in similar studies involving blacks and other races. The mean disc area reduces with increasing age.

Optic nerve head damage relation to intracranial pressure and corneal properties of eye in glaucoma risk assessment

This work presents results from numerical simulations of optic nerve head's (ONH) biomechanical behavior during exposure to elevated intraocular (IOP) and/or intracranial pressure (ICP) for ocular hypertension conditions. At the same time, a range of geometric and material properties of the eye structure and their interrelation with elevated IOP and ICP values are investigated. These simulations are performed on a generic model of the eye, which allows parametrical modification of geometric and material properties. Our main interest is in measuring ONH's potential damage in ocular hypertension due to intracranial pressure. Simulation results indicate a significant role of ICP in post-laminar neural tissue failure and a possible role of central corneal thickness (CCT) and scleral modulus in clinical assessment and treatment of patients with ocular hypertension (OHT). Specifically, CCT was found to affect ONH at early stages of damage in ocular hypertension conditions, and high scleral modulus seems to result in reduced shear failure in lamina cribrosa in a similar OHT state. These findings suggest that CCT could be a risk factor for glaucoma in OHT patients at initial stage along with cornea stiffness. Graphical abstract Graphical abstract.

A multiscale decomposition approach to detect abnormal vasculature in the optic disc

This paper presents a multiscale method to detect neovascularization in the optic disc (NVD) using fundus images. Our method is applied to a manually selected region of interest (ROI) containing the optic disc. All the vessels in the ROI are segmented by adaptively combining contrast enhancement methods with a vessel segmentation technique. Textural features extracted using multiscale amplitude-modulation frequency-modulation, morphological granulometry, and fractal dimension are used. A linear SVM is used to perform the classification, which is tested by means of 10-fold cross-validation. The performance is evaluated using 300 images achieving an AUC of 0.93 with maximum accuracy of 88%.

Cup-to-disc and arteriole-to-venule ratios in children aged 6-7 and 12-13 years

PURPOSE

Little data exist detailing the normal cup-to-disc (CD) ratios and arteriole-to-venule (A/V) ratios of school age children. In addition, controversy exists in the literature regarding associations between CD and A/V ratios and visual and biometric parameters. The present study investigates the success rates of obtaining useable optic disc images from the portable Nidek Handheld Non-Mydriatic Fundus Camera (NM-200D) from school-age children and describes the distribution of CD ratios and A/V ratios in children aged 6-7 years of age and 12-13 years of age. In addition, the present study explores associations between CD and A/V ratios and a range of visual function and biometric parameters in children.

METHODS

Fundus images were obtained from 195 6-7 year old children and 227 12-13 year old children participating in a wider study of visual function in childhood (Northern Ireland Childhood Errors of Refraction Study or NICER). ImageJ software was used to obtain CD and A/V ratios from the digital images. Visual function measures and biometric parameters were also available for all participants including; cycloplegic refractive error, vision, corneal curvature, axial length, height and weight.

RESULTS

One hundred and eighty fundus images (92.3%) from the 6-7 year olds and 194 images (85.5%) from the 12-13 year olds children were considered useable. Analysis (one way anova) demonstrated statistically significant differences between CD ratios and A/V ratios between the age groups. Participants aged 12-13 years had larger CD ratios and smaller A/V ratios (mean CD ratio 0.37 ± 0.09, mean A/V ratio 0.75 ± 0.10) than 6-7 year old participants (mean CD ratio 0.30 ± 0.09, mean A/V ratio 0.78 ± 0.12). No significant associations were noted between CD ratios and A/V ratio and any visual, ocular or biometric parameters.

CONCLUSIONS

The present study provides novel normative data on CD and A/V ratios in UK school age children for clinicians in practice.

The optic nerve head in acquired optic neuropathies

Acquired optic neuropathies are a common cause of blindness in adults, and are associated with characteristic morphological changes at the optic nerve head. Accurate and prompt clinical diagnosis, supplemented with imaging where appropriate, is essential to optimize management of the optic neuropathy and to counsel the patient appropriately on its natural history. History taking, optic disc findings, visual field assessment and imaging of the nerve head and surrounding retinal nerve fiber layer are all paramount to achieving the correct diagnosis. This Review highlights the optic nerve head features that are common to the acquired optic neuropathies, and describes the features that can be used to differentiate these various conditions.

A comparison of cup-to-disc ratio measurement in normal subjects using optical coherence tomography image analysis of the optic nerve head and stereo fundus biomicroscopy

PURPOSE

To determine the relationships between morphometric optic nerve head (ONH) characteristics defined using optical coherence tomography (OCT) and clinical judgments of cup-to-disc (CD) ratios.

METHODS

CD ratios were estimated in 20 subjects by two experienced clinicians using stereo fundus biomicroscopy. Sagittal OCT images were obtained in positions defined by clinicians corresponding to the location of their horizontal and vertical CD ratio estimates. To estimate CD ratios using the OCT images, disc width was defined as the separation of the terminations of the retinal pigment epithelium on each side of the image. OCT cup widths were determined using two criteria: the first measured the separation of cup walls halfway down each side and the second estimated the separation 1/3 down each side. Cups that were less than 150 microm deep were defined as flat for the OCT images. Data were analysed using mean and standard deviation of the differences between clinical estimates and imaging techniques as well as using intraclass correlations (ICC).

RESULTS

Between techniques, the range of ICCs for the 1/2 depth criterion was 0.74-0.90 and for the 1/3 criterion was 0.59-0.81. The limits of agreement for the 1/2 criterion were also better than the 1/3 criterion.

CONCLUSION

Accurate measures of CD ratio may be derived from OCT ONH images. Estimates of clinical CD ratios in normal subjects appear to be made using depth judgments closer to 1/2 of the way down the cup than 1/3.

Senescence of human multifocal electroretinogram components: a localized approach

BACKGROUND

Previous studies have shown significant age-related changes in the first-order kernel of multifocal ERG (mfERG) responses. All of these reports were based upon ring averages across the retinal field. This study was carried out to determine age-related changes in the localized response and localized variability in the mfERG parameters: N1P1 amplitude, scalar product and implicit time of P1.

METHODS

MfERG recordings from 70 normal phakic subjects (ages 9-80 years) were analyzed with VERIS 4.8. Scalar product values (for each hexagon based on ring average templates) were obtained and analyzed for age-related changes. Statistical measures such as coefficient of variation (CV) and parameters of a linear regression model were applied. Point-by-point comparisons were made across hemifields.

RESULTS

Each localized response showed a significant aging effect either in scalar product or in N1P1 amplitude. The average decline of the response was approximately 5% per decade, varying from 3.3% (peripherally) to 7.5% (perifoveally). The decline was significantly higher for the superior than for the inferior retina for amplitude parameters, corresponding to larger increases in P1 implicit time. The relative rate of change with age was similar for the nasal and the temporal retina. The average CV for all subjects at all locations was 29.4% (+/-4.1%).

CONCLUSIONS

The localized approach revealed patterns of age-related change that were not apparent in the ring averages. Information about changes in discrete retinal areas with age should make the mfERG more useful in quantitatively monitoring progression of retinal disease.

Absent Relative Afferent Pupillary Defect in an Asymptomatic Case of Lateral Chiasmal Syndrome from Cerebral Aneurysm

INTRODUCTION

This report documents a case of an asymptomatic 34-year-old female who had right eye subtle temporal optic nerve pallor with absent clinically detectable relative afferent pupillary defect.

CASE REPORT

This presentation was secondary to a fusiform paraclinoid aneurysm resulting in lateral chiasmal syndrome. Visual fields demonstrated a nasal depression OD. Neuroimaging studies revealed the presence of a fusiform paraclinoid aneurysm compressing the right optic nerve and optic chiasm. The lesion was treated surgically without additional visual loss nor systemic and neurological complications.

CONCLUSIONS

A clinically detectable relative afferent pupillary defect may be absent in unilateral optic nerve pallor and/or visual field loss and does not preclude the need to attempt to identify an underlying etiology. Neuroradiological examination of orbital and cranial structures is an imperative protocol in the appropriate management of this potential life- and vision-threatening condition.