Measurement of Normal Optic Nerve Head Parameters

The performance of optic disc-macula distance to disc-diameter ratio in qualitative and quantitative assessment of the optic disc size

OBJECTIVES

We aimed to evaluate the performance of the optic disc-macula distance to disc-diameter ratio (DM/DD) in qualitative and quantitative assessment of optic disc size.

METHODS

In 300 apparently normal eyes, we determined the correlation between DM/DD and the planimetric disc area (DA) and evaluated the performance of DM/DD in discriminating between small and large discs. The ability of DM/DD to predict the actual DA was validated in a separate cohort of 200 eyes. The disc size in eyes with glaucoma or related diseases was compared with DA- or DM/DD-based disc size.

RESULTS

The DM/DD and its square of inverse (DD2/DM2) showed excellent non-linear and linear correlations, respectively, with DA (p < 0.001 and p < 0.001, respectively), demonstrating their performance in discriminating between small (<2.04 mm2) and large (>2.94 mm2) disc sizes with an area under the receiver operating characteristic curve of 0.901 and 0.959, respectively. The difference between the predicted DA and planimetric DA was within ±10% in more than 80% of the eyes. Eyes with suspected and normal-tension glaucoma exhibited larger discs (p < 0.01) when evaluated using both DM/DD and DA. The variation in disc-macula distance seemed to be a confounding factor for DM/DD in inferring the precise disc size.

CONCLUSION

DM/DD, which can be easily calculated from various kinds of fundus photographs or images, was an excellent and interchangeable tool for qualitative and quantitative assessment of disc size, which did not require correction for ocular magnification.

Optic disc parameters and associations with early life exposures in over 3000 12-year-old children: findings from the ALSPAC cohort

OBJECTIVES

We aimed to investigate the distribution of small optic discs and large cup-to-disc ratio in children and to examine associations with maternal and environmental factors.

METHODS

Retinal photographs were graded from over 3000 12-year-olds in the Avon Longitudinal Study of Parents and Children. Regression models examined associations between disc parameters and maternal and early-life exposures.

RESULTS

Mean cup-to-disc area ratio (CDAR) for 3288 children was 0.21 (95%CI 0.20,0.21). Discs with CDAR > 0.3 were present in 11%. The odds of CDAR > 0.3 were increased nearly three-fold in underweight children (adjusted odds ratio (aOR) 2.9 (1.1, 7.3) p = 0.03) and 28-fold in severely premature ( < 28 weeks) children (paOR 28 95%CI 4.6,172, p < 0.001) with nearly one in four children affected. Mean cup-to-fovea/disc diameter (CF/DD) for 3327 children was 2.48 (95%CI 2.47,2.50). Small discs (CF/DD > 3) were present in 6% of which a third were bilateral. The odds of a small disc were increased in the offspring of mothers who smoked in pregnancy (aOR 1.7 (1.0,2.8) p = 0.04) and more than doubled in children born with a small head circumference (aOR 2.5 (1.4,4.5) p < 0.001).

CONCLUSIONS

Small optic discs and high cup-to-disc ratio are more frequent than usually supposed at age 12. The odds of CDAR > 0.3 are increased by severe prematurity and pathologically low child BMI. The odds of a small disc are increased by maternal smoking and small head circumference. Optimisation of risk factors in pregnancy and delivery and early childhood nutrition may play an important role in ophthalmic neurodevelopment and thus have a lifelong impact on ocular health.

Optic Disc Hypoplasia Assessment in PAX6 -Related Aniridia

BACKGROUND

This study aims to characterize optic disc hypoplasia in congenital aniridia using ultra-wide-field imaging (UWFI) and nonmydriatic retinal photography (NMRP). We also investigated the relation between optic disc hypoplasia and foveal hypoplasia.

METHODS

This is a retrospective case series of patients diagnosed with PAX6 -related aniridia in a National Referral Center, who underwent UWFI, NMRP, and spectral-domain optical coherence tomography (SD-OCT) . The disc diameter (DD) and the disc-to-fovea distance (DF) were measured. The DD:DF ratio was used to assess the relative size of the optic disc. The analyses were carried with respect to paired age- and sex-matched healthy controls. SD-OCT was used for foveal hypoplasia grading (from 1 to 4) and retinal nerve fiber layer (RNFL) analysis.

RESULTS

Mean manual DD:DF ratio was 0.33 (95% CI: 0.31-0.35) in aniridia patients versus 0.37 (95% CI: 0.36-0.39) in control patients (n = 20, P = 0.005) measured on NMRP and 0.32 (95% CI: 0.30-0.35) in aniridia patients versus 0.37 (95% CI: 0.37-0.39) in control patients (n = 26, P < 0.0001) when assessed on UWFI. Mean semiautomated DD:DF ratio measured on UWFI in aniridia patients was 0.31 (95% CI: 0.29-0.33) versus 0.37 (95% CI: 0.36-0.38) in control patients ( P < 0.0001). Also, a negative correlation was found significant between the grade of foveal hypoplasia and the mean semiautomated DD:DF ratio (r = -0.52, 95% CI: -0.76 to -0.15, P = 0.0067). Finally, a significant negative correlation was found between the peripapillary temporal RNFL thickness and the grade of foveal hypoplasia ( P = 0.0034).

CONCLUSIONS

The DD:DF ratio is significantly reduced in PAX6 -related aniridia patients and correlates with the severity of foveal hypoplasia. This ratio is a valuable tool for optic disc hypoplasia assessment in congenital aniridia, especially when provided semiautomatically by UWFI.

Ophthalmic and Systemic Factors of Acute Nonarteritic Anterior Ischemic Optic Neuropathy in the Quark207 Treatment Trial

PURPOSE

We describe the baseline ophthalmic and cardiovascular risk factors across countries, race, and sex for the Quark207 treatment trial for acute nonarteritic anterior ischemic optic neuropathy (NAION).

DESIGN

Prospective, randomized controlled clinical trial.

PARTICIPANTS

Adults 50 to 80 years of age with acute NAION recruited from 80 sites across 8 countries.

MAIN OUTCOME MEASURES

Ophthalmic features of NAION and cardiovascular risk factors.

METHODS

We evaluated demographics and clinical and ophthalmologic data, including best-corrected visual acuity (BCVA) and average visual field total deviation (TD), in affected eyes and cup-to-disc ratio in fellow eyes at enrollment. We report the prevalence (mean and standard devition, and median and interquartile range [IQR]) of ophthalmic features and cardiovascular risk factors, stratified by country, race, and sex. We corrected for multiple comparisons using Dunn's test with Bonferroni correction for continuous variables and chi-square testing with Holm-Bonferroni correction for categorical variables.

RESULTS

The study enrolled 500 men and 229 women with a median age of 60 and 61 years (P = 0.027), respectively. Participants were predominantly White (n = 570) and Asian (n = 149). The study eye BCVA was 71 characters (IQR, 53-84 characters; approximately 0.4 logarithm of the minimum angle of resolution), and the TD was -16.5 dB (IQR, -22.2 to -12.6 dB) for stimulus III and -15.7 dB (IQR, -20.8 to -10.9 dB) for stimulus V. The vertical and horizontal cup-to-disc ratio was 0.1 (IQR, 0.1-0.3) for unaffected fellow eyes. The prevalence of cardiovascular risk factors varied among countries. The most notable differences were in the baseline comorbidities and ophthalmologic features, which differed between Asian and White races. Men and women differed with respect to a few clinically meaningful features.

CONCLUSIONS

The cardiovascular risk factors in the NAION cohort varied among the 7 countries, race, and sex, but were not typically more prevalent than in the general population. Ophthalmic features, typical of NAION, generally were consistent across countries, race, and sex, except for worse BCVA and TD in China. Men have a frequency of NAION twice that of women. Having a small cup-to-disc ratio in the fellow eye was the most prevalent risk factor across all demographics. This study suggests that factors, not yet identified, may contribute to the development of NAION.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Comparing optic nerve head parameters in two Spanish dog breeds using digital planimetry

The optic discs of dogs exhibit considerable size, shape, and colour variations, depending on the degree of myelination. This variability makes the interpretation of lesions difficult, owing to the lack of reference patterns. This study aimed to compare optic nerve head (ONH) parameters determined by digital planimetry (DP) in two pure-bred dogs, Spanish Greyhound (SG) and Spanish Water Dog (SWD). The vertical and horizontal diameters, area, circularity, and the proportion of the ONH at the tapetal or non-tapetal zone (top height and bottom height) were calculated using image treatment software and compared between breeds. Significant between-breed differences were detected for all parameters, with SWD exhibiting greater height, width, area, top height, and lower circularity of the ONH than SG. Linear regression revealed that age significantly influenced mean disc height (R2 = 0.310; p = 0.0001), mean disc width (R2 = 0.280; p = 0.0001), mean disc area (R2 = 0.281; p = 0.0001), and circularity (R2 = 0.243; p = 0.0001). The multiple regression model significantly predicted mean disc height, width, and area [(S) (R2 = 0.715; p = 0.001), (R2 = 0.742; p = 0.001), and (S) (R2 = 0.736; p = 0.001), respectively], based on age and breed. Excellent concordance was observed between the measurements of experienced and novice researchers, and there were no differences between the parameters measured by the researcher and those obtained by the software. Planimetric ONH measurements can be easily performed by novice operators using a portable fundus camera and digital computer software. These results may be of considerable clinical value, but further studies are required because of the great variability of the ONH in dogs.

Morphology of the optic nerve head and factors affecting it in the Northern Finland birth cohort

PURPOSE

To assess topographic characteristics of the optic nerve head (ONH) and retinal nerve fibre layer (RNFL) and study the effect of ocular and physiological factors on them in a middle-aged population.

METHODS

A 1552-person randomised sample from Northern Finland population aged 45-49 was examined. Laser scanning tomography and optical coherency tomography were performed to obtain measurements for ONH and RNFL morphology. Measurements of the RNFL included global thickness and the six zones used in automated structure-function analysis (S-F analysis). Influence of central corneal thickness (CCT), refractive correction, intraocular pressure (IOP), anterior chamber angle, gender, blood pressure, height, weight and body mass index (BMI) on tomographic data was analysed.

RESULTS

The optic disc area had a strong correlation with all other parameters of ONH morphology (R = 0.261 to 0.706) as did spherical equivalent (R = -0.280 to 0.280). The correlations between ONH and RNFL measurements were weaker (R = 0.057 to 0.180). Gender, CCT, anterior chamber angle, blood pressure, height and BMI had statistically significant, yet feeble, correlations with a number of ONH parameters.

CONCLUSION

Other than spherical equivalent, the studied anatomical and physiological attributes had little predictive value on the ONH morphology. The optic disc area itself had a significant effect on other measurements of ONH tomography and should be taken into consideration when the thresholds for normal ONH morphology are calculated.

Evaluation of Optic Nerve Head Parameters and Retinal Nerve Fiber Layer Thickness in Axial Myopia Using SD OCT

Introduction

The purpose of this research was to study the effect of increased axial myopia, in non-glaucomatous eyes, and its correlation with ONH parameters, and RNFL thickness, using Cirrus HD 4000 SD-OCT.

Methods

The myopia group included 86 eyes of 86 patients, while the control group involved 92 eyes of 92 patients, attending the Ophthalmology Outpatient Clinic in Minia University Hospital, between November 2013 and March 2015. ONH parameters and peripapillary RNFL thickness measurement were evaluated by using SD-OCT, selecting the standard optic disc cube 200 × 200.

Results

The mean age of the myopia group was (36.55 ± 9.44), the mean spherical equivalent was (−12.70 ± 3.87 D), and the mean axial length was (27.88 ± 1.92 mm). The control group had mean age of (34.82 ± 8.87), mean spherical equivalent of −0.65 ± 0.41 D, and mean AL of (22.16 ± 0.82). A significant difference was reported between the two groups, regarding disc area (p = 0.01), rim area (p = 0.001), vertical C/D (p = 0.01), average C/D ratio (p = 0.001), average and temporal RNFL thickness (p = 0.0001, p = 0.001, respectively).

Conclusion

A significant difference was found between highly myopic non-glaucomatous eyes and the control group, regarding ONH parameters and RNFL thickness as measured by SD-OCT. As OCT magnification adjusted ONH parameters were larger, global and the temporal RNEL were thicker in the myopia group, those magnification adjusted parameters helped in an accurate evaluation of ONH and RNFL in highly myopic eyes, in order to avoid misdiagnosis of glaucoma in such eyes.

Optic Nerve Head Development in Healthy Infants and Children Using Handheld Spectral-Domain Optical Coherence Tomography

Purpose

To determine feasibility of optic nerve head (ONH) imaging and to characterize ONH development in full-term infants without sedation using handheld spectral-domain optical coherence tomography (SD OCT).

Design

Prospective cross-sectional study.

Participants

Three hundred fifty-two children aged between 1 day and 13 years.

Methods

All participants were imaged using handheld SD OCT without sedation during a single scan session. The percentage of successful scans was calculated. Interexaminer reproducibility and differences between right and left eyes were assessed using intraclass correlation coefficients (ICCs). Images were analyzed using ImageJ software. The developmental trajectories over time for ONH parameters were calculated using fractional polynomial modelling.

Main Outcome Measures

Disc and cup diameter (expressed as distance in micrometers and visual angle in degrees), cup depth, Bruch's membrane opening–minimum rim width (BMO-MRW), retinal thickness, and retinal nerve fiber layer (RNFL; 1700 μm and 6° from the disc center).

Results

On average, 70% of participants were imaged successfully. Interexaminer reliability was excellent (ICC, >0.89) for diametric and retinal thickness parameters. Right and left eyes were similar for diametric measurements (ICC, >0.79), but more variable for nasal BMO-MRW, RNFL, and retinal thickness. The mean disc and cup diameter increase by 30% and 40%, respectively, between birth and 13 years of age when expressed as a distance measure, but remained constant (at 5°–5.5° and 2°, respectively) when expressed as a visual angle with reference to the eye nodal point. The peripapillary temporal RNFL demonstrated a marked initial decrease of nearly 35% between birth and approximately 18 months of age. This was followed by a slow increase up to 12 years of age when measured at 1700 μm from the disc center, although there was little change when measured at 6° from the disc center.

Conclusions

We demonstrated feasibility of handheld SD OCT imaging of the ONH in full-term infants and children without anaesthesia or sedation. This is the first in vivo handheld SD OCT study to describe the development of ONH parameters during the critical early years of visual maturation. Our results provide a normative database for use in routine practice and further studies of ONH pathologic features.

The range of peripapillary retinal nerve fibre layer and optic disc parameters in children aged up to but not including 18 years of age, as measured by optical coherence tomography: protocol for a systematic review

BACKGROUND

The parameters of the optic disc and peripapillary retinal nerve fibre layer (pRNFL) in children may vary with disease processes that contribute to visual impairment and blindness and so could be useful as an objective measure in at-risk children. There is no standardised reference for the normal parameters of the optic disc and pRNFL in children; however, there are a large number of small individual studies that have been undertaken to look at these measures.

METHODS

A systematic review of current literature on the range of pRNFL and optic disc parameters in children aged less than 18 years will be performed. Studies will be considered for review if they report numerical data on optic disc and pRNFL parameters, measured using optical coherence tomography. Outcome measures will include mean pRNFL thickness and cup-disc ratio. The bibliographic databases Medline, CINAHL, EMBASE, Scopus and Web of Science will be systematically searched from 1991. Screening of search results will be conducted by two authors working independently, as will extraction of primary and secondary outcome data. Ten per cent of all other data extraction will be checked by a second author. Results will be compiled and presented in evidence tables. Where possible and appropriate, study-specific estimates will be combined to obtain an overall summary estimate of pRNFL thickness and cup-disc ratio across studies and results will be presented by age of population. Subgroup analyses will be undertaken for children of different ethnicities.

DISCUSSION

This review aims to provide an overview of the parameters of the optic disc and pRNFL in children of different ages in order to identify gaps in knowledge and to improve understanding of what might be considered within/outside the range of normality. The findings will be presented in peer-reviewed journals and will be presented at conferences.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42016033068.

Retinal Nerve Fiber Layer Measures and Cognitive Function in the EPIC-Norfolk Cohort Study

PURPOSE

We examined the relationship between retinal nerve fiber layer (RNFL) thickness and cognitive function in a population of older British adults.

METHODS

Participants of the European Prospective Investigation of Cancer (EPIC) Norfolk cohort study underwent ophthalmic and cognitive assessment. Measurements of RNFL thickness were made using the Heidelberg Retina Tomograph (HRT). Cognitive testing included a short form of the Mini-Mental State Examination (SF-MMSE), an animal naming task, a letter cancellation task, the Hopkins Verbal Learning Test (HVLT), the National Adult Reading Test (NART), and the Paired Associates Learning Test. Multivariable linear regression models were used to assess associations of RNFL thickness with cognitive test scores, adjusted for age, sex, education level, social class, visual acuity, axial length, and history of cataract surgery.

RESULTS

Data were available from 5563 participants with a mean age of 67 years. A thicker HRT-derived RNFL thickness was associated with better scores for the SF-MMSE (0.06; 95% confidence interval [CI], [0.02, 0.10], P = 0.005), HVLT (0.16, 95% CI [0.03, 0.29]; P = 0.014), and NART (-0.24, 95% CI [-0.46, -0.02], P = 0.035). The associations of RNFL thickness with SF-MMSE and HVLT remained significant following further adjustment for NART.

CONCLUSIONS

We found a significant association between HRT-derived RNFL thickness and scores from cognitive tests assessing global function, recognition, learning, episodic memory, and premorbid intelligence. However, the associations were weak and not currently of predictive value. Further research is required to confirm and clarify the nature of these associations, and identify biological mechanisms.

Influence of automated disc margin determination on Stratus OCT optic nerve head measurements

Purpose

To analyze the influence of manual correction of the automatically determined edge of the optic nerve head (ONH) in optic disc measurements in cases in which the optical coherence tomography did not identify the disc limits correctly.

Methods

The study included 127 eyes from 127 consecutive patients with glaucoma, suspects, and healthy individuals. In a retrospective analysis, eyes that underwent testing with the Stratus OCT (software version 4.0, Carl Zeiss Meditec, Dublin, CA, USA) Fast Optic Disc protocol were evaluated. Forty-seven eyes in which either the manual assignment was not necessary or the signal strength was below six were excluded. After image acquisition and processing, one expert examiner manually corrected the determination of the edge of the ONH, identified as the end of the retinal pigment epithelium/choriocapillaris complex. Disc area, cup area, rim area, and cup/disc area ratio results were compared before and after the optic disc margin manually corrected determination. Paired t-test was performed to evaluate the differences, and Bland–Altman plots were used to display the relationships between measurements.

Results

Eighty eyes from 80 individuals were included in the analyses. No statistically signifiant difference (P=.538) was found when analyzing results obtained with automated and manual determination of rim area (mean ± standard deviation; 1.30±0.45 mm² and 1.29±0.39 mm², respectively). Cup area (1.39±0.58 mm² and 1.31±0.55 mm², respectively), cup/disc area ratio (0.50±0.16 mm² and 0.49±0.15 mm², respectively), and disc area results (2.69±0.55 mm² and 2.60±0.51 mm², respectively) were significantly different.

Conclusion

The Stratus OCT ONH Report results were little influenced when optic disc limits were manually determined. Therefore the standard automated Stratus OCT disc margin assignment is adequate, and manual correction is not necessary.

Imaging of retinal ganglion cells in glaucoma: pitfalls and challenges

Imaging has gained a key role in modern glaucoma management. Traditionally, interest was directed toward the appearance of the optic nerve head and the retinal nerve fiber layer. With the improvement of the resolution of optical coherence tomography, the ganglion cell complex has also become routinely accessible in the clinic. Further advances have been made in understanding the structure-function relationship in glaucoma. Nevertheless, direct imaging of the retinal ganglion cells in glaucoma would be advantageous. With the currently used techniques, this goal cannot be achieved, because the transversal resolution is limited by aberrations of the eye. The use of adaptive optics has significantly improved transversal resolution, and the imaging of several cell types including cones and astrocytes has become possible. Imaging of retinal ganglion cells, however, still remains a problem, because of the transparency of these cells. However, the visualization of retinal ganglion cells and their dendrites has been achieved in animal models. Furthermore, attempts have been made to visualize the apoptosis of retinal ganglion cells in vivo. Implementation of these techniques in clinical practice will probably improve glaucoma care and facilitate the development of neuroprotective strategies.