Optic Disc Area Research Articles

Characteristics of Peripapillary Retinal Nerve Fiber Layer Thickness in Eyes With Myopic Optic Disc Tilt and Rotation

The purpose of the study was to investigate the effects of myopic optic disc tilt and rotation on peripapillary retinal nerve fiber layer (RNFL) thickness characteristics measured by Cirrus HD spectral-domain optical coherence tomography (Cirrus HD OCT). A total of 93 right eyes from 93 healthy young male individuals with myopia underwent ophthalmic examinations, including refractive error, axial length, and optic disc area measurements. The superior/inferior peak locations, RNFL thickness, and horizontal/vertical optic disc tilt were evaluated using the Cirrus HD OCT. The optic disc rotation was assessed by the angle between the long axis of the optic disc and the vertical meridian. The patients were divided into the tilted group and the non-tilted group; the tilted group was further divided into the rotated group and the nonrotated group. The eyes in the tilted group (n=47) had a greater axial length and thicker temporal RNFL and more temporally positioned superior/inferior peak locations than the non-tilted group (n=46) (all P <0.05). Among the eyes in the tilted group, the eyes in the rotated group (n=23) had a thicker temporal RNFL and a more temporally positioned superior peak location than the eyes in the nonrotated group (n=24) (all P <0.05). The eyes with a myopic temporal optic disc tilt and counterclockwise rotation had a thicker temporal RNFL and more temporally positioned superior peak location. The characteristics of the RNFL thickness in eyes with myopic optic disc tilt and rotation should be considered when interpreting the RNFL thickness measured by the Cirrus HD OCT.

Genetic Investigation into the Endophenotypic Status of Central Corneal Thickness and Optic Disc Parameters in Relation to Open-Angle Glaucoma

To ascertain if single nucleotide polymorphisms (SNPs) involved in the determination of central corneal thickness, optic disc area, and vertical cup-to-disc ratio (VCDR) also are associated with open-angle glaucoma (OAG). Retrospective case-control genetic association study. A total of 16 SNPs associated with central corneal thickness, optic disc area, and VCDR were genotyped in 876 OAG cases and 883 normal controls. To determine if the SNPs were also correlated with OAG severity, the cohort was stratified into advanced OAG (n = 326) and nonadvanced OAG (n = 550). Both the cases and controls were of European descent and were recruited from within Australia. Two VCDR SNPs were found to be significantly associated with OAG after correction for multiple testing. The 2 SNPs were rs10483727, found adjacent to the SIX1 gene (P = 6.2 × 10(-06); odds ratio, 1.38; 95% confidence interval, 1.20 to 1.59), and rs1063192, found within the CDKN2B gene (P = 2.2 × 10(-05); odds ratio, 0.74; 95% confidence interval, 0.64 to 0.85). The CDKN2B variant rs1063192 also was found to be associated more strongly with advanced OAG. The findings from this study indicate that variants influencing VCDR are also risk alleles for OAG in our Australian cohort of European descent. The identification of SIX1 and CDKN2B as susceptibility loci will assist in understanding the pathologic mechanisms involved in the development of OAG.

Does Optic Nerve Head Size Variation Affect Circumpapillary Retinal Nerve Fiber Layer Thickness Measurement by Optical Coherence Tomography?

To determine the relationship between retinal nerve fiber layer (RNFL) thickness, optic disc size, and image magnification. The cohort consisted of 196 normal eyes of 101 participants in the Advanced Imaging for Glaucoma Study (AIGS), a multicenter, prospective, longitudinal study to develop advanced imaging technologies for glaucoma diagnosis. Scanning laser tomography was used to measure disc size. Optical coherence tomography (OCT) was used to perform circumpapillary RNFL thickness measurements using the standard fixed 3.46-mm nominal scan diameter. A theoretical model of magnification effects was developed to relate RNFL thickness (overall average) with axial length and magnification. Multivariate regression showed no significant correlation between RNFL thickness and optic disc area (95% confidence interval [CI] = -0.9 to 4.1 μm/mm², P = 0.21). Linear regression showed that RNFL thickness depended significantly on axial length (slope = -3.1 μm/mm, 95% CI = -4.9 to -1.3, P = 0.001) and age (slope = -0.3 μm/y, 95% CI = -0.5 to -0.2, P = 0.0002). The slope values agreed closely with the values predicted by the magnification model. There is no significant association between RNFL thickness and optic disc area. Previous publications that showed such an association may have been biased by the effect of axial length on fundus image magnification and, therefore, both measured RNFL thickness and apparent disc area. The true diameter of the circumpapillary OCT scan is larger for a longer eye (more myopic eye), leading to a thinner RNFL measurement. Adjustment of measured RNFL thickness by axial length, in addition to age, may lead to a tighter normative range and improve the detection of RNFL thinning due to glaucoma.

Ganglion cell complex scan in the early prediction of glaucoma

To compare the macular ganglion cell complex (GCC) with peripapillary retinal fiber layer (RNFL) thickness map in glaucoma suspects and patients. Forty participants (20 glaucoma suspects and 20 glaucoma patients) were enrolled. Macular GCC and RNFL thickness maps were performed in both eyes of each participant in the same visit. The sensitivity and specificity of a color code less than 5% (red or yellow) for glaucoma diagnosis were calculated. Standard Automated Perimetry was performed with the Octopus 3.1.1 Dynamic 24-2 program. The statistical analysis was performed with the SPSS 10.1 (SPSS Inc. Chicago, IL, EUA). Results were expressed as mean +/- standard deviation and a p value of 0.05 or less was considered significant. Provide absolute numbers of these findings with their units of measurement. There was a statistically significant difference in average RNFL thickness (p=0.004), superior RNFL thickness (p=0.006), inferior RNFL thickness (p=0.0005) and average GCC (p=0.03) between the suspects and glaucoma patients. There was no difference in optic disc area (p=0.35) and vertical cup/disc ratio (p=0.234) in both groups. While 38% eyes had an abnormal GCC and 13% had an abnormal RNFL thickness in the glaucoma suspect group, 98% had an abnormal GCC and 90% had an abnormal RNFL thickness in the glaucoma group. The ability to diagnose glaucoma with macular GCC thickness is comparable to that with peripapillary RNFL thickness . Macular GCC thickness measurements may be a good alternative or a complementary measurement to RNFL thickness assessment in the clinical evaluation of glaucoma.

Measurement of Optic Disc Size and Rim Area with Spectral-Domain OCT and Scanning Laser Ophthalmoscopy

To compare optic disc and neuroretinal rim area measurements from spectral-domain optical coherence tomography (SD-OCT) to those from confocal scanning laser ophthalmoscopy. Seventy-one eyes from 43 normal subjects or suspected/definite glaucoma patients were prospectively enrolled. All subjects had biometry with the IOLMaster and disc/retinal nerve fiber layer imaging with Cirrus SD-OCT (Optic Disc Cube 200×200) and Heidelberg Retina Tomograph (HRT). Uncorrected disc and rim areas and measurements corrected for eye magnification with Bennett's formula (AL-corrected measurements), along with 30° sectoral rim areas, vertical cup-to-disc ratio (VCDR), and cup volume, were compared between the two devices. The median (range) axial length (AL) was 24.2 mm (22.4-27.7 mm). Mean keratometry-corrected HRT disc area measurements were larger than AL-corrected HRT and SD-OCT measurements (P < 0.001 for both) and the difference was a function of keratometry measurements (K-readings). The AL-corrected HRT disc area and uncorrected/corrected Cirrus disc areas were not significantly different (P > 0.481). HRT rim area was larger than Cirrus measurements (P < 0.001) and the difference decreased with decreasing rim area. HRT VCDR and cup volume were significantly smaller than Cirrus measurements (P < 0.001). The correlations for sectoral rim areas between the two devices were moderate at best (intraclass correlation coefficients = 0.12-0.65). HRT overestimated optic disc area as compared to SD-OCT. A portion of the difference in HRT and SD-OCT disc measurements is due to HRT's magnification correction algorithm. Rim area measurements from HRT were larger than from SD-OCT, likely a result of different definitions for the reference plane and differences in disc area measurements. Disc parameters from the two devices are not interchangeable.

Math5 (Atoh7) gene dosage limits retinal ganglion cell genesis

The basic helix-loop-helix factor Math5 (Atoh7) is critical for the determination of retinal ganglion cell (RGC) fate in mice. Recently, genome-wide association studies have identified the ATOH7 locus as a major determinant of variation in the human optic disc area, which is directly correlated with the RGC number. These studies suggest that the level of Math5 expression may determine the ultimate number of RGCs. To test this hypothesis, we systematically compared optic nerve area and RGC axon number in C57BL/6J congenic Math5+/- and +/+ mice at young adult and neonatal ages by transmission electron microscopy. Optic disc area and RGC abundance were not significantly different in adults, but heterozygotes had thinner optic nerves and 25-30% fewer RGCs at birth than wild-type littermates (P<0.05). Our results suggest that Math5 dosage is important for the genesis, but not the ultimate number, of RGCs. Our findings highlight the importance of ganglion cell culling as a compensatory mechanism for retinal homeostasis, and support a quantitative role for Math5 in RGC specification.

Optic Disc Imaging with Spectral-Domain Optical Coherence Tomography: Variability and Agreement Study with Heidelberg Retinal Tomograph

To evaluate the agreement of optic disc measurements obtained with the Cirrus high-density optical coherence tomography (HD-OCT) and the Heidelberg retina tomograph (HRT) and compare the intervisit, test-retest variability between the instruments. Prospective, cross-sectional study. Two hundred seven subjects (109 glaucoma and 98 normal subjects). One eye from each individual was selected randomly for optic disc imaging by the Cirrus HD-OCT and the HRT. Areas of the optic disc and the cup, cup volume, vertical cup-to-disc ratio and cup-to-disc area ratio were compared between the instruments. The OCT measurements were corrected for ocular magnification using the Littman's formula. The measurement agreement was evaluated with the Bland-Altman plots. The intervisit test-retest variability was examined in 17 randomly selected glaucoma patients who underwent optic disc imaging weekly for 8 consecutive weeks. The intraclass correlation coefficients (ICC) and the reproducibility coefficients of the optic disc parameters were computed. Measurement agreement, reproducibility coefficients, and ICCs of optic disc parameters. The OCT measured smaller optic disc and rim areas and greater cup volume, vertical cup-to-disc ratio and cup-to-disc area ratio than the HRT did (all with P<0.001). There were proportional biases in the Bland-Altman plots between OCT and HRT optic disc measurements except for rim area and cup-to-disc area ratio. The 95% limits of agreement of rim area ranged between -0.28 and 0.88 mm(2) before, and between -0.22 and 0.92 mm(2) after correction for ocular magnification. Both OCT and HRT showed high test-retest reproducibility with ICCs ≥ 0.921. Although the reproducibility coefficient of OCT rim area (0.093 mm(2); 95% confidence interval [CI], 0.081-0.105 mm(2)) was significantly smaller than that of the HRT (0.186 mm(2); 95% CI, 0.163-0.210 mm(2); P = .018), there were no differences in the ICCs between the instruments. Optic disc assessment by spectral-domain OCT and confocal scanning laser ophthalmoscopy demonstrates poor agreement but similarly low test-retest variability. The source of their disagreement and its effects on the detection of progression require further study.

Ocular axial length and corneal refraction in children with mucopolysaccharidosis (MPS I‐Hurler)

To assess corneal refraction and axial length in children with mucopolysaccharidosis I-Hurler (MPS I-H), treated early with stem cell transplantation (SCT), in order to establish possible causes of hyperopia. Clinical ophthalmological follow-up included keratometry and measurements of axial length. Five patients, with SCT performed before 23 months of age, were examined. Median age was 8.2 years (range 5.2-10.5). Best-corrected decimal visual acuity was ≥ 0.5 (≥ 20/40 Snellen fraction) in seven of 10 eyes. High hyperopia, ranging from +4.0 to +9.0 spherical equivalents, was noted in all 10 eyes. Mild to moderate corneal opacities occurred in all 10 eyes. Optic disc areas, borders and cuppings were normal in all 10 eyes. No patient had glaucoma. Keratometry could be performed in five patients and demonstrated low values in the group ranging from 38.24 to 41.56 Diopters (D) right eye to 38.24-41.94 D left eye, which was significantly lower than the age matching reference material (p < 0.05). Axial lengths, available in five patients, ranged between 20.68 to 21.57 mm right eye and 20.52 to 21.38 mm left eye, which also was lower than the age matching reference material (p < 0.05). Reduced axial length together with reduced corneal refraction is suggested to be causative to the hyperopia in patients with MPS I Hurler. Detection of refractive errors and prescription of eye glasses are important to avoid amblyopia.

Acquired Optic Nerve and Peripapillary Pits in Pathologic Myopia

To examine the incidence and characteristics of pit-like structures around the optic disc and myopic conus in eyes with high myopia. Prospective, observational case series. We evaluated 198 eyes of 119 patients with pathologic myopia (spherical equivalent >-8 diopters [D]). We also evaluated 32 eyes of 32 subjects with emmetropia (refractive error ≤±3 D) as controls. The papillary and peripapillary areas were examined with a prototype swept-source optical coherence tomography (OCT) system with a center wavelength of 1050 nm. We studied the structural characteristics of pit-like changes. The incidence and characteristics of the optic nerve (ON) pits in eyes with high myopia. Pit-like clefts were found at the outer border of the ON or within the adjacent scleral crescent in 32 of 198 highly myopic eyes (16.2%) but in none of the emmetropic eyes. The eyes with these pits were more myopic, had significantly longer axial lengths, and had significantly larger optic discs than the highly myopic eyes without pits. The pits were located in the optic disc area (optic disc pits) in 11 of 32 eyes and in the area of the conus outside the optic disc (conus pits) in 22 of 32 eyes. One eye had both optic disc pits and conus pits. The optic disc pits existed in the superior or inferior border of the optic disc. All but 1 eye with conus pits had a type IX staphyloma, and the location of the conus pits were present nasal to the scleral ridge or outside the ridge temporal to the nerve. The optic disc pits were associated with discontinuities of the lamina cribrosa, whereas the conus pits appeared to develop from a scleral stretch-associated schisis or to emissary openings for the short posterior ciliary arteries in the sclera. The nerve fiber tissue overlying the pits was discontinuous at the site of the pits. Optic nerve pits are common in highly myopic eyes. The ON pits are barely visible ophthalmoscopically but can be demonstrated by using swept-source OCT.

Correlations Between Digital Planimetry and Optical Coherence Tomography, Confocal Scanning Laser Ophthalmoscopy in Assessment of Optic Disc Parameters

In routine clinical practice, laser methods for the evaluation of optic disc parameters are expensive and not accessible for all ophthalmologists; therefore, there is a need for less expensive technique. The aim of this study was to assess correlations between the parameters of the optic disc measured by digital planimetry (DP), optical coherence tomography (OCT), and confocal scanning laser ophthalmoscopy (CSLO) in healthy and glaucoma patients with the normal biometric parameters of the eye. This case-control study enrolled 40 patients with glaucoma and 32 healthy patients with the normal biometric parameters of the eye. All subjects underwent full ophthalmologic examination, digital color optic disc photography, OCT, and CSLO at the same visit. The optic disc was morphometrically analyzed by DP, OCT, and CSLO. Seven optic disc parameters were evaluated. In the glaucoma group, the optic disc and cup areas (r=0.7-0.8, P<0.001) and cup-to-optic disc and rim-to-optic disc area ratios (r=0.7, P<0.001) measured by DP were strongly correlated with those measured by OCT and CSLO, while the horizontal and vertical cup-to-optic disc diameter ratios were found to be moderately correlated (r=0.6-0.7, P<0.001). In healthy patients, the optic disc and cup areas were strongly correlated (r=0.7-8.0, P<0.001). Significant differences in all optic disc parameters, except for the optic disc area, measured by DP, OCT, and CSLO were found between glaucoma and healthy patients. Strong correlations between the parameters of the optic disc measured by DP, OCT, and CSLO were found. There were significant differences in the parameters between healthy and glaucoma eyes measured using DP; therefore, this technique may be used for diagnosis, management, and screening of glaucoma.

Comparison of optic disc parameters using spectral domain cirrus high‐definition optical coherence tomography and confocal scanning laser ophthalmoscopy in normal eyes

To compare Cirrus HD - optical coherence tomography (HD-OCT) with confocal scanning laser ophthalmoscopy (HRT 3) for analysis of optic disc parameters in healthy eyes. In 126 subjects, cup volume (CV), vertical cup/disc ratio (CDR), neuroretinal rim area (NRA), cup area (CA) and optic disc area (ODA) were measured with the Cirrus HD-OCT and HRT 3. These optic disc parameters were chosen for statistical analysis because they can be analysed in both OCT and HRT 3 and they are widely used parameters for glaucoma assessment. Mean values and significances of paired t-tests for OCT and HRT were for CV: 0.099 ± 0.11 versus 0.082 ± 0.10 (p < 0.001), CA: 0.42 ± 0.31 versus 0.39 ± 0.31 (p < 0.001), CDR: 0.36 ± 0.17 versus 0.27 ± 0.21 (p < 0.001). NRA and ODA were not significantly different between instruments. The Pearson coefficients were 0.905 (CV), 0.824 (CA), 0.734 (CDR), 0.295 (NRA) and 0.378 (ODA). To our interpretation, the delineation of the optic disc border is error-prone with both instruments and all parameters directly depending on it are thus poorly correlated. However, the determination of the optic disc excavation (CV and CA) appears comparable taking into account a small systematic difference between instruments.

Effect of Race, Age, and Axial Length on Optic Nerve Head Parameters and Retinal Nerve Fiber Layer Thickness Measured by Cirrus HD-OCT

To determine the effect of race, demographic, and ocular variables on optic nerve head and retinal nerve fiber layer (RNFL) thickness measurements using spectral-domain optical coherence tomography. In a cross-sectional observational study, 284 normal subjects aged 18 to 84 years were evaluated at 7 sites using Cirrus HD-OCT. Disc area, rim area, average cup-disc ratio, vertical cup-disc ratio, cup volume, and average, temporal, superior, nasal, and inferior RNFL thicknesses were calculated. The main outcome measures were associations between Cirrus HD-OCT optic nerve head and RNFL measurements and age, sex, and race. The 284 subjects self-identified as being of European (122), Chinese (63), African (51), or Hispanic (35) descent. After adjusting for the effect of age, there was a statistically significant difference among racial groups for all optic nerve head and RNFL parameters (all P≤.005) except rim area (P=.22). Rim area, average cup-disc ratio, vertical cup-disc ratio, and cup volume were moderately associated with disc area (r(2)=0.15, 0.33, 0.33, and 0.37, respectively). After a linear adjustment for disc area, there was no statistically significant difference among racial groups for any optic nerve head parameter. Individuals of European descent had thinner RNFL measurements except in the temporal quadrant. There are racial differences in optic disc area, average cup-disc ratio, vertical cup-disc ratio, cup volume, and RNFL thickness as measured by Cirrus HD-OCT. These differences should be considered when using Cirrus HD-OCT to assess for glaucomatous damage in differing population groups.

Genome-wide association studies in the hunt for genes causing primary open-angle glaucoma: a review

Genome-wide association studies are a powerful tool for the identification of genetic risk factors for complex disease. This methodology has been successfully applied to primary open-angle glaucoma through the analysis of primary open-angle glaucoma (POAG) as well as specific subgroups of patients including those with normal tension glaucoma and advanced glaucoma. In addition, the analysis of quantitative traits important in POAG, including optic disc area and vertical cup-to-disc ratio has also identified genes important in POAG development. This review explores findings of genome-wide association studies for POAG and related traits.

Comparison of scanning laser ophthalmoscopy and high-definition optical coherence tomography measurements of optic disc parameters

ObjectiveTo investigate the agreement between scanning laser ophthalmoscopy (Heidelberg retinal tomograph 3; HRT-3) and high-definition optical coherence tomography (HD–OCT) for measurements of optic nerve head (ONH) parameters.MethodsAs part of a...

Paracentral retinal holes occurring after macular surgery: incidence, clinical features, and evolution

To describe the incidence, clinical features, and evolution of paracentral retinal holes occurring after macular surgery. A retrospective non-randomized study of 909 patients operated on for either a macular hole (MH, n = 400 patients) or an epiretinal membrane (ERM, n = 509 patients) between 2004 and 2009. Six patients (0.6%) developed a paracentral macular hole after surgery. Their clinical, auto-fluorescence, and optical coherence tomography (OCT) characteristics as well as their visual outcomes were studied. The mean age of patients was 70years. Paracentral holes occurred approximately 5weeks after surgery (with a range of 2-12weeks). All patients were asymptomatic. Five patients underwent ILM peeling during initial surgery. Paracentral retinal holes were located superiorly to the fovea in three cases and temporally in the other three cases. Mean pre-operative BCVA was 20/200 and mean post-operative BCVA was 20/40. The eye where the eccentric MHs were closest to the fovea (inferior to 1 optic disc area) had the poorest final visual acuity. Autofluorescence imaging showed a bright fluorescence in paramacular holes. On OCT images, they were shown to be flat full-thickness holes. No treatment was attempted. No rhegmatogenous complications or choroidal neovascularization occurred in any of the patients. Mean follow-up was 2years. In summary, paracentral MHs are uncommon complications which can occur at the site where ILM peeling has been initiated or completed. Except for the closest holes to fovea, they have good visual prognosis and do not require any treatment underlining the importance of initiating the ILM peeling as far as possible from the fovea.

Optic disc measurements in full term infants

BackgroundThe objectives of this study were to measure optic disc size in full term infants and to determine whether this value is influenced by sex or birth weight.MethodsRetinal images from...

Retinal Nerve Fiber Layer Imaging with Spectral-Domain Optical Coherence Tomography: A Prospective Analysis of Age-Related Loss

To investigate age-related changes of the retinal nerve fiber layer (RNFL) imaged by a spectral-domain optical coherence tomography (OCT). Prospective, cross-sectional, and longitudinal studies. One hundred normal individuals were recruited for cross-sectional analysis, 35 of whom were randomly selected for longitudinal analysis. The circumpapillary average and quadrant RNFL thicknesses were measured by the Cirrus HD-OCT. In the longitudinal study, participants were followed at 4-month intervals for a mean of 30 months (range, 24-41 months) for RNFL and visual field measurements. Cross-sectional RNFL data were analyzed with multiple linear regression models with adjustment of spherical error, optic disc area, and signal strength. Longitudinal RNFL measurements were analyzed with linear mixed models with fixed coefficients on follow-up duration, baseline RNFL thickness, spherical error, optic disc area, and signal strength. Factors influencing the rate of change of RNFL measurements were analyzed in the interaction terms with "duration" in the linear mixed models. Rates of change of average and quadrant RNFL thicknesses. In the cross-sectional analysis, significant negative correlations were found between age and average (-0.33 μm/year; P = 0.011), inferior (-0.45 μm/year; P = 0.037), and temporal (-0.31 μm/year; P = 0.046) RNFL thicknesses. In the longitudinal analysis, the mean rates of change of average, superior, and inferior RNFL thicknesses were -0.52 (95% confidence interval [CI], -0.86 to -0.17), -1.35 (95% CI, -2.05 to -0.65) and -1.25 μm/year (95% CI, -1.78 to -0.71), respectively, after adjusting for baseline RNFL thickness, spherical error, disc area, and signal strength. There was no detectable RNFL reduction in the nasal and temporal quadrants. The only significant factor influencing the rates of change of RNFL measurements was the baseline RNFL thickness. A greater baseline RNFL thickness was associated with a faster rate of change. Progressive, age-related decline of RNFL thickness can be detected with longitudinal OCT imaging. Rate estimates derived from trend analysis for detection of glaucomatous RNFL progression should be interpreted with reference to the normal ranges of age-related reduction, particularly when the baseline RNFL measurement is large.

Quality of Nonmydriatic Digital Fundus Photography Obtained by Nurse Practitioners in the Emergency Department: The FOTO-ED Study

Nonmydriatic fundus photography by non-ophthalmic-trained personnel has recently been shown to be a potential alternative to direct ophthalmoscopy in the emergency department (ED). We evaluated the reliability of a novel quality rating scale and applied this scale to nonmydriatic fundus photographs taken during routine ED patient encounters to determine factors associated with diminished photograph quality. Prospective, cross-sectional study. We included 350 patients enrolled in the Fundus photography versus Ophthalmoscopy Trials Outcomes in the Emergency Department study who were photographed by nurse practitioners after <30 minutes of training followed by supervision. Photographs of both eyes were graded for quality on 2 occasions by 2 neuro-ophthalmologists. Four regions were independently evaluated for quality: Optic disc, macula, and superior and inferior vascular arcades. Quality as a function of the number of photographs taken was evaluated by Kaplan-Meier analysis. Mixed effects ordinal logistic regression was used to evaluate for predictors of image quality while accounting for the repeated measures design. Overall photographic quality (1-5 scale; 5 best). We evaluated 1734 photographs. Inter- and intraobserver agreements between neuro-ophthalmologists were very good (weighted kappa, 0.84-0.87). Quality of the optic disc area was better than those of other retinal areas (P<0.002). Kaplan-Meier analysis showed that if a high-quality photograph of an eye was not obtained by the third attempt, it was unlikely that one would be obtained at all. A 10-second increase in the interphotograph interval before a total of 40 seconds increased the odds of a 1-unit higher quality rating by 1.81 times (95% confidence interval [CI], 1.68-1.98), and a 10-year increase in age decreased the odds by 0.76 times (95% CI, 0.69-0.85). Black patients had 0.42 times (95% CI, 0.28-0.63) the odds of a 1-unit higher quality rating compared with whites. Our 5-point scale is a reliable measure of nonmydriatic photograph quality. The region of interest, interphotograph interval, and patient age and race are significant predictors of image quality for nonmydriatic photographs taken by nurse practitioners in the ED. Addressing these factors may have a direct impact on the successful implementation of nonmydriatic fundus photography into the ED.

A Formula to Predict Spectral Domain Optical Coherence Tomography (OCT) Retinal Nerve Fiber Layer Measurements Based on Time Domain OCT Measurements

PurposeTo establish and validate a formula to predict spectral domain (SD)-optical coherence tomography (OCT) retinal nerve fiber layer (RNFL) thickness from time domain (TD)-OCT RNFL measurements and other factors.MethodsSD-OCT and TD-OCT scans were obtained on the same day from healthy participants and patients with glaucoma. Univariate and multivariate linear regression relationships were analyzed to convert average Stratus TD-OCT measurements to average Cirrus SD-OCT measurements. Additional baseline characteristics included age, sex, intraocular pressure, central corneal thickness, spherical equivalent, anterior chamber depth, optic disc area, visual field (VF) mean deviation, and pattern standard deviation. The formula was generated using a training set of 220 patients and then evaluated on a validation dataset of 105 patients.ResultsThe training set included 71 healthy participants and 149 patients with glaucoma. The validation set included 27 healthy participants and 78 patients with glaucoma. Univariate analysis determined that TD-OCT RNFL thickness, age, optic disc area, VF mean deviation, and pattern standard deviation were significantly associated with SD-OCT RNFL thickness. Multivariate regression analysis using available variables yielded the following equation: SD-OCT RNFL = 0.746 × TD-OCT RNFL + 17.104 (determination coefficient [R2] = 0.879). In the validation sample, the multiple regression model explained 85.6% of the variance in the SD-OCT RNFL thickness.ConclusionsThe proposed formula based on TD-OCT RNFL thickness may be useful in predicting SD-OCT RNFL thickness. Other factors associated with SD-OCT RNFL thickness, such as age, disc area, and mean deviation, did not contribute to the accuracy of the final equation.

Letter to the Editor: Quantitative Analysis of Optic Disc Color

Dear Editor, I read with great interest the article by Kim et al. [1] regarding the use of ImageJ to quantitatively analyze the color of optic discs. The authors proposed three points to measure the intensity per pixel area after grayscale conversion, namely nasal rim (NR), brightest cupping center (BCC), and inferior retinal vein (IRV). They found good inter-observer correlation with this method, along with an age-related decrease of BCC pixel intensity. However, the authors did not mention either the disc area or the characteristics of the subjects enrolled in the study. The optic disc area has a high inter-individual variability: large discs have a larger neuroretinal rim area, an increased total area of lamina cribrosa (LC) pores, and a higher ratio of interpore connective tissue area to total LC area [2]. Therefore, in large discs, it might be difficult to determine a representative region denoting BCC if significant pores of different color are located at the very center of the disc. In small discs, on the contrary, a minimal number of or no cups would make the measurement of BCC inaccurate or impossible. Both Varma et al. [3] and Kashiwagi et al. [4] pointed out there were no age-related differences in disc configuration 3,4. When the proportion of small : normal : large disc sizes in Kim's sample was not constant with age, there was a deviation of disc size in particular age group(s), indirectly reducing the accuracy of the correlation of BCC intensity with age. Also, objective measurements of lens status, color, and opalescence were not performed other than a brief mention of best-corrected visual acuity greater than 20 / 25 in all subjects. In patients suffering from nucleosclerotic cataract, the visual acuity can be much preserved with a disproportionate loss of transparency. Media opacities are likely to be present to some extent in some of the older subjects, which is a major confounding factor. This should prompt the use of a more objective lens assessment system such as Lens Opacity Classification System III or Scheimpflug images to adjust the obtained parameters 5. The ImageJ software enables a particular area of an image to be highlighted and a histogram of intensity to be calculated. Grewal et al. [5] employed this method to study different parts of a nuclear cataract and to determine correlations among several visual functions 5. Its importance, in our context, is highlighted in analyzing optic neuropathies with sectoral pallor, such as ischemic optic neuropathy, 'bow-tie' atrophy from chiasmal compression, and pathological temporal pallor in nutritional optic neuropathy. The contrast of 'intensity' between different areas of a disc might be enhanced in borderline cases, which helps with diagnosis. Serial measurements can serve as a tool to longitudinally monitor patients. Alternatively, the whole neuroretinal rim or cup can be highlighted to provide a more generalized quantitative analysis of the region of interest.