The normal cup-disk ratio

Does Inter-Eye Asymmetry of Disc Area Explain Differences in Onset of Nonarteritic Anterior Ischemic Optic Neuropathy?

BACKGROUND

Nonarteritic anterior ischemic optic neuropathy (NAION) is the most common acute optic neuropathy in individuals over the age of 50 years. It is associated with conventional vascular risk factors and structural vulnerabilities including "disc-at-risk." We aim to ascertain if a correlation exists between optic nerve head size and the onset of NAION.

METHODS

We performed a retrospective chart review of patients with an ICD-10 diagnosis of unilateral or bilateral NAION who underwent optical coherence tomography (OCT) and visual field testing. The primary outcome measure was the disc area as measured on OCT at a follow-up (minimum 6 months after acute vision loss) of the involved (or first involved for bilateral cases) vs fellow eye. The secondary outcome was the cup-to-disc ratio (CDR) of the first vs fellow eye.

RESULTS

Seventy-three patients were included, of which 58 (79%) had unilateral and 15 (21%) had bilateral NAION, with a median follow-up of 23 months. Between the first eye involved and the fellow eye, there were no statistically significant differences in the mean disc area (1.69 ± 0.29 vs 1.71 ± 0.29, P = 0.7). However, average CDR (0.41 ± 0.20 vs 0.28 ± 0.18, P < 0.001) and vertical CDR (0.42 ± 0.20 vs 0.28 ± 0.19, P < 0.0001) were significantly larger in the involved eye.

CONCLUSIONS

Despite no statistically significant differences in the disc area between the affected eye and the fellow eye, CDR was larger in eyes with a history of NAION compared with fellow eyes. Further research is required to elucidate local factors that may increase the risk of NAION in one eye relative to the other.

Circumpapillary OCT-based multi-sector analysis of retinal layer thickness in patients with glaucoma and high myopia

Glaucoma is the leading cause of irreversible blindness worldwide. The diagnosis process for glaucoma involves the measurement of the thickness of retinal layers in order to track its degeneration. The elongated shape of highly myopic eyes can hinder this diagnosis process, since it affects the OCT scanning process, producing deformations that can mimic or mask the degeneration caused by glaucoma. In this work, we present the first comprehensive cross-disease analysis that is focused on the anatomical structures most impacted in glaucoma and high myopia patients, facilitating precise differential diagnosis from those solely afflicted by myopia. To achieve this, a fully automatic approach for the retinal layer segmentation was specifically tailored for the accurate measurement of retinal thickness in both highly myopic and emmetropic eyes. To the best of our knowledge, this is the first approach proposed for the analysis of retinal layers in circumpapillary optical coherence tomography images that takes into account the elongation of the eyes in myopia, thus addressing critical diagnostic needs. The results from this study indicate that the temporal superior (mean difference 11.1μm, p<0.05), nasal inferior (13.1μm, p<0.01) and temporal inferior (13.3μm, p<0.01) sectors of the retinal nerve fibre layer show the most significant reduction in retinal thickness in patients of glaucoma and myopia with regards to patients of myopia.

Long-Term Rate of Optic Disc Rim Loss in Glaucoma Patients Measured From Optic Disc Photographs With a Deep Neural Network

Purpose

This study uses deep neural network-generated rim-to-disc area ratio (RADAR) measurements and the disc damage likelihood scale (DDLS) to measure the rate of optic disc rim loss in a large cohort of glaucoma patients.

Methods

A deep neural network was used to calculate RADAR and DDLS for each optic disc photograph (ODP). Patient demographics, diagnosis, intraocular pressure (IOP), and mean deviation (MD) from perimetry were analyzed as risk factors for faster progression of RADAR. Receiver operating characteristic (ROC) curves were used to compare RADAR and DDLS in their utility to distinguish glaucoma from glaucoma suspect (GS) and for detecting glaucoma progression.

Results

A total of 13,679 ODPs with evidence of glaucomatous optic nerve damage from 4106 eyes of 2407 patients with glaucoma or GS were included. Of these eyes, 3264 (79.5%) had a diagnosis of glaucoma, and 842 (20.5%) eyes were GS. Mean ± SD baseline RADAR of GS and glaucoma were 0.67 ± 0.13 and 0.57 ± 0.18, respectively (P < 0.001). Older age, greater IOP fluctuation, baseline MD, right eye, and diagnosis of secondary open-angle glaucoma were associated with slope of RADAR. The mean baseline DDLS of GS and glaucoma were 3.78 and 4.39, respectively. Both RADAR and DDLS showed a less steep slope in advanced glaucoma. In glaucoma, the change of RADAR and DDLS correlated with the corresponding change in MD. RADAR and DDLS had a similar ability to discriminate glaucoma from GS and detect disease progression. Area under the ROC curve of RADAR and DDLS was 0.658 and 0.648.

Conclusions

Automated calculation of RADAR and DDLS with a neural network can be used to evaluate the extent and long-term rate of optic disc rim loss and is further evidence of long-term nerve fiber loss in treated patients with glaucoma.

Translational Relevance

Our study provides a large clinic-based experience for RADAR and DDLS measurements in GS and glaucoma with a neural network.

Central retinal vessel trunk exit location: An important factor while evaluating the neuroretinal rim

PURPOSE

Optic nerve head (ONH) evaluation plays a key role in differentiating normal from glaucomatous disk. Thinning of the inferior neuroretinal rim (NRR) has been noted in early glaucoma. However, NRR thickness in different quadrants appears to depend on various factors including central retinal vessel trunk exit (CRVT) position. We evaluated ocular parameters that determined the NRR thickness in the different quadrants of normal eyes.

METHODS

Retrospective review of demographic and ocular data from 773 eyes of 388 subjects with normal ONH over one year was undertaken.

RESULTS

Nearly 54% were males, and the mean age was 43.2 years. The CRVT exit was central in 50% (773). The common site for noncentral CRVT was superotemporal (ST) [37%, 141/384] followed by inferotemporal (IT) [35%, 135/384]. With noncentral CRVT, the probability that the inferior, superior, nasal and temporal (ISNT) rule was not followed was 1.42 times ( P < 0.001). The thinnest rim quadrant (TRQ) was mostly ST (69%) irrespective of CRVT location. The TRQ was IT in 40% when CRVT was noncentral and 82% with IT CRVT exit. With noncentral CRVT, round disks favored noncompliance [132 (54.1%), odds ratio (OR) 2.56] with the ISNT rule. The OR of noncompliance with the ISNT rule increases 1.89 times with inferonasal CRVT and 1.22 times with a unit increase in the axial length.

CONCLUSION

TRQ was IT in IT CRVT, and noncompliance with the ISNT rule was observed with large disks, longer axial length, and noncentral CRVT. This implies that despite the ISNT rule being violated these eyes do not have optic nerve pathology and should not be subjected to unnecessary diagnostic tests.

Longitudinal Assessment of Retinal Nerve Fiber Layer and Ganglion Cell Complex Thicknesses in Patients With Large Optic Disc Cups and Normal Intraocular Pressure and Visual Fields

PRCIS

The thicknesses of the circumpapillary retinal nerve fiber layer (cpRNFL) and ganglion cell complex (GCC) did not change during 5 years in physiological large disc cupping.

PURPOSE

We evaluated longitudinal changes in the thicknesses of the cpRNFL and GCC in large disc cupping with a normal intraocular pressure (IOP) (<21 mm Hg) and visual field.

METHODS

This retrospective, consecutive case series study included 269 eyes of 269 patients with large disc cupping and normal IOP. We analyzed patient demographics, IOP, central corneal thickness, vertical cup-to-disc ratios using color fundus photography, the thicknesses of the cpRNFL and GCC using RTVue-100, and mean deviation using visual field examinations.

RESULTS

The differences in IOP, vertical cup-to-disc ratios, and mean deviation between the baseline and each follow-up visit were not statistically significant. The baseline average and mean average at 60 months follow-up of the cpRNFL thickness were 106.5±8.5 and 105.1±9.3 μm, respectively; differences between the baseline and each follow-up visit were not statistically significant. The baseline average and mean average at 60 months follow-up of the GCC thickness were 82.8±9. and 81.5±9.2 μm, respectively; differences between baseline and each follow-up visit were not statistically significant.

CONCLUSIONS

The thicknesses of the cpRNFL and GCC did not change in well-maintained optic nerve head findings with normal IOP and visual field during a 5-year follow-up period. Optical coherence tomography evaluations of the thicknesses of the cpRNFL and GCC help accurately diagnose physiological optic disc cupping.

Traumatic Optic Neuropathy Aggravated by Orbital Emphysema after Orbital Fracture

Purpose: To report a case of traumatic optic neuropathy aggravated by orbital emphysema after an orbital fracture.Case summary: A 19-year-old man with no specific medical history was referred for a right orbital fracture caused by blunt trauma to the supraorbital rim of the right eye. Computed tomography (CT) showed a right orbital fracture involving the inferomedial wall and inferomedial strut. The corrected visual acuity was 0.4 in the right eye (RE) and 1.0 in the left and the intraocular pressure was 15 and 18 mmHg, respectively. Restriction on downgaze, abduction, and an indefinite relative afferent pupillary defect (RAPD) were observed in the RE. Fundus exam was non-specific other than commotio retinae on the temporal side of the macula in the RE. After 12 hours post trauma, the visual acuity of the RE had decreased to light perception. Definite RAPD was observed with optic disc swelling on the fundus photo and optical coherence tomography. Orbital CT showed air shadows, which were not seen on the initial evaluation, adjacent to the optic disc. We diagnosed traumatic optic neuropathy aggravated by orbital emphysema. High-dose intravenous steroid was given for 3 days. Despite a lateral canthotomy and cantholysis to decompress the right orbit, visual acuity did not improve above counting fingers.Conclusions: Increased intraorbital pressure and congestion caused by orbital emphysema may exacerbate traumatic optic neuropathy. Therefore, close observation is required.

Change of ocular parameters in children with large cup-to-disc ratio and interocular cup-to-disc ratio asymmetry

BACKGROUND

Enlarged optic disc cupping and interocular cup-to-disc ratio (CDR) asymmetry are often important indicators of glaucoma. Clinically, we occasionally encounter children with large CDR and interocular CDR asymmetry during vision screening. This study aimed to report longitudinal change of ocular parameters in children with large cup-to-disc ratio (CDR) and interocular CDR asymmetry.

METHODS

This was a retrospective, observational case series of 160 eyes of 160 children with large CDR who visited a tertiary eye center from January 2010 to June 2016. Average CDR ≥ 0.6 were considered large CDR values, and CDR asymmetry was defined as an interocular difference ratio value greater than 0.2. All included patients showed interocular pressure (IOP) < 21 mmHg at least three ophthalmic examinations conducted at total intervals of at least 30 months.

RESULTS

The mean age of children included in the study was 7.14 ± 2.42 years, with a follow-up period of 54.46 ± 19.82 months. Changes in refractive error and axial length were significantly different between initial and final examination (p < 0.001). However, optic nerve head (ONH) analysis and retinal nerve fiber layer (RNFL) and macular ganglion cell-inner plexiform layer (mGCIPL) thicknesses were not significantly different between initial and final examination. In interocular comparisons of patients with CDR asymmetry, changes of refractive error, axial length, ONH analysis, and RNFL and mGCIPL thickness were not significantly different between the two eyes.

CONCLUSIONS

There were no significant differences in the changes of ONH analysis, and RNFL and mGCIPL thicknesses in children with large CDR, or those with interocular CDR asymmetry over the study period. Our results provide helpful information for the establishment of guidelines for managing children with large CDR and interocular CDR asymmetry.

The Distribution of Vertical Cup-to-Disc Ratio and its Determinants in the Iranian Adult Population

Purpose:

To determine the distribution of vertical cup-to-disc ratio (VCDR) and its relationship with ocular biometric indices.

Methods:

This study was conducted in 4737 individuals aged 45-69 years living in Shahroud who participated in the second phase of Shahroud Eye Cohort Study in 2014. All participants underwent eye examinations including the measurement of visual acuity and refraction, slit-lamp biomicroscopy, retinal examination, and fundoscopy. Normality index was used to describe data distribution, and a multiple beta regression, with adjustment for the effect of cluster sampling, was applied to explore the relationship between VCDR and the study variables.

Results:

The mean [95% confidence interval (CI)] VCDR was 0.297 (0.293-0.301) in all participants; 0.296 (0.291-0.302) in men and 0.297 (0.292-0.302) in women. The highest mean VCDR was seen in the age group 55-59 years (0.299, 95% CI: 0.292-0.307). The 97.5^th percentile was 0.600. According to multiple beta regression analysis, VCDR had a positive association with the female sex (P = 0.028), spherical equivalent (P < 0.001), cigarette smoking (P = 0.020), and axial length (P < 0.001), and had a negative association with hypertension (P = 0.001), best corrected visual acuity (P < 0.001), hyperlipidemia (P = 0.029) and anterior chamber depth (P = 0.001).

Conclusions:

The mean VCDR and the 97.5^th percentile were lower than most other studies. Although ethnicity and race may play a role in this difference, this difference should be considered in clinical decisions in the current population.

Tissue-Engineered Models for Glaucoma Research

Glaucoma is a group of optic neuropathies characterized by the progressive degeneration of retinal ganglion cells (RGCs). Patients with glaucoma generally experience elevations in intraocular pressure (IOP), followed by RGC death, peripheral vision loss and eventually blindness. However, despite the substantial economic and health-related impact of glaucoma-related morbidity worldwide, the surgical and pharmacological management of glaucoma is still limited to maintaining IOP within a normal range. This is in large part because the underlying molecular and biophysical mechanisms by which glaucomatous changes occur are still unclear. In the present review article, we describe current tissue-engineered models of the intraocular space that aim to advance the state of glaucoma research. Specifically, we critically evaluate and compare both 2D and 3D-culture models of the trabecular meshwork and nerve fiber layer, both of which are key players in glaucoma pathophysiology. Finally, we point out the need for novel organ-on-a-chip models of glaucoma that functionally integrate currently available 3D models of the retina and the trabecular outflow pathway.

Differences of megalopapilla and normal sized disk with age-an optical coherence tomography analysis

PURPOSE

To compare the optic disks of children and adults with megalopapilla using optical coherence tomography (OCT).

SUBJECTS AND METHODS

We conducted a case-control study of subjects with megalopapilla and normal sized disks seen between February 2013 and July 2015 at the Hospital da Luz, Lisbon. All subjects and controls were imaged with spectral domain OCT, and optic nerve head (ONH) parameters were evaluated. The main outcome measures were rim area, cup:disk ratio, and cup volume.

RESULTS

A total of 168 eyes of 168 subjects were included: 78 with megalopapilla (39 children/39 adults) and 90 (45/45) with normal sized disks. For the same ONH area, children had a higher rim area (P = 0.000), a smaller cup:disk ratio (P = 0.001), and a smaller cup volume (P = 0.001) than adults. For the same age group, megalopapilla had a larger cup:disk ratio (P = 0.000) and a larger cup volume (P = 0.000) than normal-sized disks.

CONCLUSIONS

In this study cohort, compared to adults with the same disk size, children (with megalopapilla or normal-sized disks) had a larger rim area and smaller cup. These findings suggest that enlargement of the cup of the optic disk and reduction of the rim area can occur through life.

Comparison of Fundus Biomicroscopy Examination of the Optic Nerve Head with and without Mydriasis

BACKGROUND

Notwithstanding the significant advances in automated imaging techniques in the past 2 decades, subjective evaluation of the optic disc still remains an important part of glaucoma propaedeutic. In places with limited resources and a high demand for ophthalmic care, anatomical evaluation of glaucoma cases often relies solely on slit-lamp-based fundus biomicroscopic examination, which is frequently performed without mydriasis.

OBJECTIVE

The aim of this study was to compare metrics related to fundus biomicroscopy examination of the optic nerve head and peripapillary retinal nerve fiber layer (pRNFL) with and without mydriasis.

MATERIAL AND METHODS

Healthy individuals, patients with early glaucoma, and glaucoma suspects were prospectively enrolled. Patients were examined before and after mydriasis by three glaucoma specialists, who estimated patients' vertical cup-to-disc ratio (CDR) and evaluated the presence of glaucomatous signs: laminar dot sign, disc hemorrhage, disc saucering, disc notching, peripapillary atrophy, localized pRNFL defect, and loss of the ISNT pattern. Main outcome measures were the intra-observer comparison, the inter-observer agreement, and the abilities to identify glaucomatous signs before and after mydriasis.

RESULTS

Thirty patients (60 eyes) were enrolled (mean age, 62.3 ± 11.6 years). Considering the evaluation of the three examiners, the mean vertical CDR increased from 0.41 to 0.44 (p = 0.02), and the median of the coefficient of variation of the measures was reduced from 0.24 to 0.11 (p = 0.01) after mydriasis. Regarding the inter-observer agreement evaluation, the kappa coefficient values ranged from 0.64 to 0.72 before mydriasis and from 0.71 to 0.77 after mydriasis. Dot sign and disc notching were better identified through fundoscopic examination with mydriasis compared to the nonmydriatic examination (p < 0.01).

CONCLUSION

Our results suggest that fundus biomicroscopy should be performed with mydriasis whenever possible, as it yells a better intra- and inter-observer agreement and improves the detection of glaucomatous signs. Moreover, examiners seem to underestimate CDR values without mydriasis. Further investigation is warranted to validate these findings by general ophthalmologists and in different populations.

Prevalence of increased intraocular pressure in patients with Graves' ophthalmopathy and association with ophthalmic signs and symptoms in the north-west of Iran

Introduction

Graves’ ophthalmopathy (GO) is the most common extra-thyroidal manifestation of Graves' disease and is characterized by multiple ocular symptoms such as eyelid retraction, lid lag, proptosis, elevated intraocular pressure (IOP) and ultimately loss of vision. We aimed to investigate the prevalence of increased IOP in Graves' patients and association with ophthalmic signs and symptoms in north-west of Iran.

Materials and methods

This descriptive cross-sectional study recruited 93 patients with GO who were diagnosed based on clinical and laboratory examinations. A complete ocular examination and IOP measurements on forward gaze were performed using Goldman applanation tonometer.

Results

In this study, 93 patients with GO were evaluated from 2016 to 2017. Among these patients, 67 (72.05%) were female and 27 (27.95%) were male. The most common complaints of patients were lid retraction (62.36%), puffy eyelids (58.06%) and proptosis (46.23%), respectively. The duration of disease was 0–24 months in most patients. Most subjects were at grade 3 according to NOSPECS classification. Nine patients (9.6%) had an IOP greater than or equal to 21 mmHg. The mean IOP in subjects was 16.61±3.42 mmHg. The mean IOP in males and smokers was significantly higher than that of females and nonsmokers. The mean IOP increased significantly with a higher grade of disease, duration of disease, age and smoking.

Conclusions

According to the results, females comprised the majority of the study population, while ocular complications were more prevalent among males. The highest IOP was seen in old cases of GO. The most prevalent ocular signs in patients were eyelid retraction and periorbital edema. The least prevalent sign was glaucomatous optic neuropathy. In this study, the prevalence of intra-ocular hypertension was higher than that of the general population, especially in males, old cases with a drug history of antithyroid medication and smokers.

Factors Affecting ISNT Rule Satisfaction in Normal and Glaucomatous Eyes

Purpose

To determine the factors that influence the satisfaction of the ‘ISNT rule’ (neural rim width: inferior ≥ superior ≥ nasal ≥ temporal) in normal and glaucomatous eyes.

Methods

The medical records of patients that visited Boramae Medical Center, Seoul, Korea, were reviewed. Each group of normal and glaucomatous eyes was divided into subgroups based on whether or not they satisfied the ISNT rule. ISNT rule assessment was performed by measuring the rim width with stereoscopic optic disc photographs using ImageJ software. Logistic regression analysis was performed to determine the factors that affect ISNT rule satisfaction.

Results

Seventy-seven normal eyes and 97 glaucomatous eyes were included in the study. The ISNT rule was intact in 59 (76.6%) of the normal eyes and was violated in 71 (73.2%) of the glaucomatous eyes. Logistic regression analysis revealed a significant influence of axial length in violation of the ISNT rule in the normal eye group, while the mean deviation value was a significant factor for violation of the ISNT rule in the glaucomatous eye group.

Conclusions

The ISNT rule should be cautiously applied when evaluating normal eyes with long axial lengths. In addition, the ISNT rule might not be as effective for detecting early glaucoma.

Evaluation of subjects with a moderate cup to disc ratio using optical coherence tomography and Heidelberg retina tomograph 3: impact of the disc area

Aim:

The aim was to evaluate subjects with a moderate cup to disc ratio using optical coherence tomograph (OCT) and Heidelberg retina tomograph (HRT) 3.

Settings and Design:

We included 80 patients with early glaucoma and 80 nonglaucomatous subjects with moderate cup/disc ratio (range of 0.5–0.8) to this cross-sectional study.

Subjects and Methods:

We compared results of color-coded algorithms of HRT 3 (Moorfields regression analysis [MRA] and Glaucoma probability score [GPS]) and OCT. All outputs are classified into three categories: Within normal limits (WNLs), borderline and outside normal limits (ONLs). Diagnostic accuracies of algorithms were determined using the highest sensitivity criteria.

Results:

The sensitivities of global MRA, GPS and OCT were 0.75, 0.925 and 0.725, respectively, in average disc area group and 0.85, 1.0 and 0.425, respectively, in large disc area group. The specificities of global MRA, GPS and OCT were 0.55, 0.15 and 0.85, respectively, in average disc area group and 0.425, 0.025 and 0.80, respectively, in large disc area group. Area under receiver operating characteristic curve (AUROC) of global MRA, GPS and OCT were 0.667, 0.617 and 0.792, respectively, in average disc area group and 0.746, 0.576 and 0.627, respectively, in large disc area group. AUROC of global MRA and OCT combination in the average and large disc area groups were 0.828 and 0.825, respectively.

Conclusions:

In contrast to GPS and OCT algorithms, diagnostic performance of MRA algorithm increased in large disc area group. Combining MRA and OCT algorithms produced satisfactory diagnostic performance in subjects with an average and large disc area.

Characterization of Choroidal Layers in Normal Aging Eyes Using Enface Swept-Source Optical Coherence Tomography

Purpose

To characterize qualitative and quantitative features of the choroid in normal eyes using enface swept-source optical coherence tomography (SS-OCT).

Methods

Fifty-two eyes of 26 consecutive normal subjects were prospectively recruited to obtain multiple three-dimensional 12x12mm volumetric scans using a long-wavelength high-speed SS-OCT prototype. A motion-correction algorithm merged multiple SS-OCT volumes to improve signal. Retinal pigment epithelium (RPE) was segmented as the reference and enface images were extracted at varying depths every 4.13μm intervals. Systematic analysis of the choroid at different depths was performed to qualitatively assess the morphology of the choroid and quantify the absolute thicknesses as well as the relative thicknesses of the choroidal vascular layers including the choroidal microvasculature (choriocapillaris, terminal arterioles and venules; CC) and choroidal vessels (CV) with respect to the subfoveal total choroidal thickness (TC). Subjects were divided into two age groups: younger (<40 years) and older (≥40 years).

Results

Mean age of subjects was 41.92 (24-66) years. Enface images at the level of the RPE, CC, CV, and choroidal-scleral interface were used to assess specific qualitative features. In the younger age group, the mean absolute thicknesses were: TC 379.4μm (SD±75.7μm), CC 81.3μm (SD±21.2μm) and CV 298.1μm (SD±63.7μm). In the older group, the mean absolute thicknesses were: TC 305.0μm (SD±50.9μm), CC 56.4μm (SD±12.1μm) and CV 248.6μm (SD±49.7μm). In the younger group, the relative thicknesses of the individual choroidal layers were: CC 21.5% (SD±4.0%) and CV 78.4% (SD±4.0%). In the older group, the relative thicknesses were: CC 18.9% (SD±4.5%) and CV 81.1% (SD±4.5%). The absolute thicknesses were smaller in the older age group for all choroidal layers (TC p=0.006, CC p=0.0003, CV p=0.03) while the relative thickness was smaller only for the CC (p=0.04).

Conclusions

Enface SS-OCT at 1050nm enables a precise qualitative and quantitative characterization of the individual choroidal layers in normal eyes. Only the CC is relatively thinner in the older eyes. In-vivo evaluation of the choroid at variable depths may be potentially valuable in understanding the natural history of age-related posterior segment disease.

Intrasubject Difference in CCT among POAG versus Normal Individuals

PURPOSE

To evaluate intrasubject asymmetry in central corneal thickness (CCT) among patients with primary open-angle glaucoma (POAG) as compared with that of normal subjects and to determine whether the eye with thinner cornea has more severe glaucomatous visual field damage.

METHODS

In this case-control study, CCT of both eyes was measured using an ultrasonic pachymeter (UP-1000; Nidek Technologies, Gamagori, Japan) among POAG patients and normal subjects. The intrasubject difference in CCT was calculated and compared between the study groups; correlations between CCT and intraocular pressure (IOP), vertical cup-to-disc ratio (VCDR), and visual field defects were also evaluated.

RESULTS

A total of 62 patients with bilateral POAG and 56 normal subjects were included. There was no significant difference between the study groups in terms of age, sex, and ocular parameters except for visual acuity, IOP, and VCDR. The POAG patients demonstrated significantly greater intrasubject asymmetry in CCT (8 ± 7 μm vs. 5 ± 3 μm; p = 0.041) and a higher prevalence of significant (>10 μm) intrasubject CCT difference (30.6 vs. 5.4%; p < 0.001) as compared with normal subjects. Although each higher level of glaucomatous damage was associated with 4-μm thinner CCT, the correlation was not statistically significant (95% confidence interval, -8 to 1 μm; p = 0.117; GEE analysis). No significant correlation was observed between CCT and IOP or VCDR (p = 0.302 and 0.137, respectively).

CONCLUSIONS

Patients with POAG demonstrate a larger amount of intrasubject difference in CCT as compared with normal subjects.

Ocular dimensions in relation to auxological data in a sample of Swedish children aged 4-15 years

PURPOSE

The purpose was to characterize normal growth patterns of ocular and optical components and to relate them to auxological data in a sample of Swedish children aged 4-15 years.

METHODS

A prospective cross-sectional study was carried out in 143 Swedish children with a mean age of 9.8 years. Variables including gestational age (GA), weight, length and head circumference (HCF) at birth and at the time of assessment were registered. Visual acuity (VA), cycloplegic refraction and biometric measures were obtained. Palpebral fissure length and inner canthal distance were measured. Optic disc morphology as seen on fundus photographs was analysed.

RESULTS

Children born more mature, with male predilection, were found to have deeper anterior and vitreous chamber depths, longer axial lengths and thinner crystalline lens thickness. No correlations were found between ocular biometric measurements and VA or refraction after adjustment for confounding variables. Inner canthal distance was significantly correlated with birth length (p = 0.03), height, weight, BMI and HCF (p = 0.0008, p = 0.0007, p = 0.037, and p = 0.04, respectively) at time of assessment. Total axial length was found to be significantly correlated with GA (p = 0.0226) and length at assessment in girls (p = 0.0084). Right optic disc and rim areas decreased with increasing age (p = 0.0078 and p = 0.0107, respectively); however, optic disc parameters were not dependent on any other variable.

CONCLUSION

These normative values may serve as a basis for the ocular findings and their relationship to auxological data in Caucasian children aged 4-15 years, as well as for future comparison in patients with paediatric ocular pathologies.

Analysis of neuroretinal rim distribution and vascular pattern in eyes with presumed large physiological cupping: a comparative study

BACKGROUND

To investigate possible differences in neuroretinal rim distribution, vascular pattern, and peripapillary region appearance between eyes with presumed large physiological optic disc cupping (pLPC) and eyes with minimal optic disc excavation.

METHODS

We prospectively enrolled consecutive subjects with pLPC and individuals with minimal excavation (optic disc excavation within normal limits; control group). All eyes had normal visual fields and untreated intraocular pressure (IOP) <21 mmHg. Eyes with pLPC required vertical cup-to-disc ratio (VCDR) ≥ 0.6 and ≥ 30 months of follow-up with no evidence of glaucomatous neuropathy. For controls, VCDR was limited to ≤ 0.5. We compared ocular signs and characteristics related to the neuroretinal rim distribution, vascular pattern, peripapillary region appearance and disc size between groups. Whenever both eyes were eligible, one was randomly selected for analysis.

RESULTS

A total of 74 patients (mean age, 45.6 ± 14.9 years) with pLPC and 45 controls (mean age, 44.8 ± 11.6 years) were enrolled (p = 0.76). Median disc size and VCDR was significantly larger in eyes with pLPC compared to controls (p < 0.01). The proportion of eyes with violation of the ISNT rule, laminar dot sign, nasal shifting of the central vessels, nasal excavation and baring of circumlinear vessel was significantly greater in the eyes with pLPC compared to controls (p < 0.01). There were no significant differences regarding the proportions of eyes with peripapillary atrophy between groups (p < 0.09). Finally, disc size was significantly associated with VCDR (r(2) = 0.47, p < 0.01), with an increase of 0.21 in VCDR for each 1 mm(2) in disc area.

CONCLUSION

Compared to normal controls, eyes with pLPC may present a higher proportion of optic nerve head findings frequently observed in glaucomatous eyes. This seems to be explained in part by the larger discs found in these eyes. We believe care should be taken while classifying them as glaucomatous or not based solely on these characteristics.

The relationship between cup-to-disc ratio and estimated number of retinal ganglion cells

PURPOSE

To investigate the relationship between cup-to-disc ratio (CDR) and estimates of retinal ganglion cell (RGC) number.

METHODS

This cross-sectional study included 156 healthy eyes, 53 glaucoma suspects, and 127 eyes with glaucoma. All eyes had standard automated perimetry (SAP), Cirrus SD-OCT, and stereoscopic optic disc photography within 6 months. CDR was determined from stereoscopic photographs by two or more masked graders. The number of RGCs in each eye was estimated using a published model that combines estimates of RGC number from SAP sensitivity thresholds and SD-OCT retinal nerve fiber layer measurements.

RESULTS

The mean estimated RGC count was 1,063,809 in healthy eyes; 828,522 in eyes with suspected glaucoma; and 774,200 in early, 468,568 in moderate, and 218,471 in advanced glaucoma. Healthy eyes had a mean vertical CDR of 0.45 ± 0.15 vs. 0.80 ± 0.16 in glaucomatous eyes. There was good correlation between stereophotographic vertical CDR and SD-OCT vertical CDR (R(2) = 0.825; P < 0.001). The relationship between estimated RGCs and vertical CDR was best represented using a third degree polynomial regression model, including age and optic disc area, which accounted for 83.3% of the variation in estimated RGC counts. The nonlinear relationship between RGC estimates and CDRs indicated that eyes with a large CDR would require loss of large RGC numbers for a small increase in CDR.

CONCLUSIONS

The relationship between estimated RGC counts and CDR suggests that assessment of change in CDR is an insensitive method for evaluation of progressive neural losses in glaucoma. Even relatively small changes in CDR may be associated with large losses of RGCs, especially in eyes with large CDRs. (ClinicalTrials.gov numbers, NCT00221923, NCT00221897.).

Longitudinal study of optic cup progression in children

PURPOSE

To determine the normative rate of cup-to-disc-ratio (C:D) progression in children and the effect of prematurity and low birth weight on this rate.

METHOD

In a single pediatric ophthalmology practice, a single examiner evaluated optic cup size by serial ophthalmoscopy over a minimum of 5 years in 92 patients (184 eyes) without intraocular surgery or optic nerve disease. A cross-sectional analysis of C:D was performed per year of age from 0 to 10 years and linear regression was used to compare C:D progression between preterm and term children and between low versus normal birth weight children.

RESULTS

Children exhibited progressive optic cupping. In term children, mean C:D increased by 0.0075 per year. Rate of mean C:D progression was double in children born preterm: 0.0160 (P = .049, comparison to term) per age-year. A similar, nonsignificant trend is observed when comparing low birth weight to normal children (P = .131).

CONCLUSION

Prematurity and low birth weight are associated with increased rate of cupping in children. Clinicians should recognize that C:D progression is not a specific sign of glaucoma in children.

Cup to disc ratio by optical coherence tomography is abnormal in multiple sclerosis

OBJECTIVE

To identify and characterize cup to disc ratio (CDR) and related optic nerve head abnormalities in multiple sclerosis (MS) using spectral domain optical coherence tomography (OCT).

BACKGROUND

While CDR is routinely assessed by ophthalmologists in the evaluation of glaucoma, CDR and related optic nerve head metrics remain largely unexplored in MS.

DESIGN/METHODS

Cirrus-HD (high density) OCT was used to evaluate average CDR, vertical CDR, optic disc area, optic cup volume, and neuro-retinal rim area in 105 MS patients and 88 age-matched healthy individuals. High-contrast (100%) visual acuity, 2.5% low-contrast letter acuity and 1.25% low-contrast letter acuity were assessed in 77 MS patients. Two-sample t-tests were used in the analysis of OCT-derived optic nerve head measures between healthy controls and MS patients. Multivariate regression (accounting for age and gender) was used to assess relationships between optic nerve head measures and visual function.

RESULTS

Average CDR (p=0.007) and vertical CDR (p=0.005) were greater in MS patients compared to healthy controls, while neuro-retinal rim area was decreased in MS patients (p=0.001). CDR increased with retinal nerve fiber layer (RNFL) thinning (r=-0.29, p=0.001). 2.5% low-contrast (p=0.005) and 1.25% low-contrast letter acuity (p=0.03) were lower in MS patients with higher vertical CDR.

CONCLUSIONS/RELEVANCE

CDR (as determined by spectral domain OCT) is abnormal in MS and correlates with visual function. OCT-derived CDR and related optic nerve head metrics may represent an objective measure by which to monitor disease progression, and potentially neuroprotection, in therapeutic MS trials.

Optic nerve heads in pediatric African Americans using retinal tomography

PURPOSE

To characterize optic nerve head (ONH) parameters including symmetry between the eyes in healthy African American children using the Heidelberg retinal tomograph II, and to determine if there are associations between these parameters and age, refractive error, or gender.

METHODS

The ONHs of 146 African American children aged 6 to 17 years without ocular disease were imaged with the Heidelberg retinal tomograph II. Mean values for 11 ONH parameters were determined as was their relationship to age, gender, and refractive error. Interocular symmetry of the parameters was determined.

RESULTS

The mean (+/-standard deviation) disc area, rim area, and cup area were 2.18 +/- 0.57 mm2, 1.63 +/- 0.40 mm2, and 0.52 +/- 0.37 mm2, respectively. The mean linear cup-to-disc (C/D) ratio was 0.45 +/- 0.15, and mean cup depth was 0.22 +/- 0.10 mm. The mean retinal nerve fiber layer thickness was 0.26 +/- 0.07 mm. The ONH parameters were not related to age or refractive error. With the exception of the C/D area ratio and linear C/D ratio, which were greater in boys than in girls, ONH parameters were not related to gender. Most parameters were strongly correlated between the right and left eyes. The average interocular differences in disc area, cup area, rim area, linear C/D ratio, and mean retinal nerve fiber layer thickness were 0.09 +/- 0.31 mm2, 0.04 +/- 0.22 mm2, 0.06 +/- 0.40 mm2, 0.02 +/- 0.11, and 0.00 +/- 0.06 mm2, respectively.

CONCLUSIONS

ONH parameters were not related to age and refractive error, and only C/D area ratio and linear C/D ratio were greater in boys than girls in a clinical sample of African American children. These measures of normative ONH parameters and range of interocular differences may be helpful in clinical pediatric eye care to facilitate identification of African American children with abnormal optic discs.

Quantification of neuroretinal rim loss using digital planimetry in long-term follow-up of normals and patients with ocular hypertension

PURPOSE

The purpose of this study was to investigate if digital planimetry is appropriate for quantification of neuroretinal rim loss in patients with ocular hypertension (OHT) and if there is an age-related neuroretinal rim loss in normals.

PATIENTS AND METHODS

Fifty-six patients with OHT without optic disc change, 13 patients with OHT and conversion to early glaucoma during follow-up and 42 age-matched controls were recruited from the Erlangen Glaucoma Registry. Annually, all patients underwent complete ophthalmologic examination including detailed diagnostic testing concerning glaucoma. Gold standard for morphologic evaluation of the optic nerve head was the semiquantitative 2-dimensional-method described by Jonas. Optic disc images from baseline and after 5 or 10 years follow-up were used for digital planimetry. Optic disc area and cup area were measured using commercial software: Soft Imaging System analysis. The investigator was masked for diagnosis and time point of examination.

RESULTS

Mean neuroretinal rim loss was 0.36% per year in controls, 0.54% per year in patients with OHT without progressive disease, and 0.95% per year in OHT and conversion.

CONCLUSIONS

Neuroretinal rim loss was highest in the group of OHT with conversion to early glaucoma during follow-up. In the control group we detected a very low mean neuroretinal rim loss during 10-year follow-up. In ocular hypertensive patients without progressive disease mean neuroretinal rim loss was approximately twice compared with normals.

Evaluating the optic disc and retinal nerve fiber layer in glaucoma. I: Clinical examination and photographic methods

Glaucoma is a leading cause of blindness worldwide and is characterized in part by specific changes in the optic disc and retinal nerve fiber layer. Currently, subjective clinical examination and fundus photography are the most common ways of detecting structural change in glaucoma and monitoring its progression. In the first part of this two-part article, the authors overview structural changes of the optic disc and retinal nerve fiber layer in glaucoma and describe and evaluate photographic methods for observing these changes. In the second part of this article (this issue), recent developments in computer-based optical imaging techniques that allow objective evaluation of the optic disc and retinal nerve fiber layer are described.

Optic nerve head parameters of an indigenous population living within Central Australia

PURPOSE

Clinical examination of the optic disc is an essential element in the assessment of its health. Previous work has described normal optic disc appearance among different races. No such description of optic discs exists for indigenous Australians, who are at low risk of developing glaucoma. This study was designed to evaluate optic disc parameters of indigenous Australians.

METHODS

A sample of 208 indigenous Australians were recruited as they presented to remote clinics in Central Australia. Each subject underwent optic disc photography using a Topcon TRC-NW100 digital fundus camera. Optic discs were measured and analysed with Topcon ImageNet 2000 software.

RESULTS

Among other parameters, mean vertical disc diameter and disc area were 2.13 +/- 0.21 mm (mean +/- SD) and 3.13 +/- 0.57 mm2, respectively, for right eyes and 2.14 +/- 0.21 mm and 3.16 +/- 0.58 mm2 for left eyes. When compared with published studies, these parameters were significantly larger than Caucasians, but similar to African individuals.

CONCLUSION

Our results suggest that indigenous Australians have optic discs that are larger than those of Caucasians, but similar to those of Africans who are considered to at a greater risk of glaucoma. Factors other than optic disc area are likely to underlie the higher prevalence of primary open angle glaucoma among African individuals.

Distribution of intraocular pressure in healthy Iranian individuals: the Tehran Eye Study

AIM

To provide data on the distribution of intraocular pressure (IOP) in an Iranian population.

METHODS

Through a population based, cross sectional study, 4565 Tehran citizens were studied in the Tehran Eye Study. The findings from the participants (n = 3834) aged 10 years and older free of glaucoma diagnosis or suspicion who had undergone applanation tonometry examination are presented. All participants received a standardised protocol including applanation tonometry, fundus examination, demographic data, and an interview. IOP measurement was used to evaluate its distribution by age, sex, and some eye parameters.

RESULTS

Mean (SD) IOP was 14.5 (2.6) mm Hg in the total population, 14.4 (2.7) in men, and 14.5 (2.5) in women. Mean (SD) IOP in people > or =40 years was 15.1 (2.9) mm Hg. IOP increased significantly with age and cup:disc ratio except for a fall in old age. This relation was also observed when individuals without diabetes or hypertension history were analysed. IOP increased with darker eye pigmentation except for blue/grey eyes. There was a non-linear increase in IOP from emmetropic to high myopic eyes.

CONCLUSION

Age, iris colour, and cup:disc ratio were related to IOP but not to sex. The distribution of IOP in this study was different from various other studies in different geographical regions and it seems advisable to employ a geographical approach to normal IOP interpretation.

Genotype–phenotype studies in nail-patella syndrome show that LMX1B mutation location is involved in the risk of developing nephropathy

Nail-patella syndrome (NPS) is characterized by developmental defects of dorsal limb structures, nephropathy, and glaucoma and is caused by heterozygous mutations in the LIM homeodomain transcription factor LMX1B. In order to identify possible genotype-phenotype correlations, we performed LMX1B mutation analysis and comprehensive investigations of limb, renal, ocular, and audiological characteristics in 106 subjects from 32 NPS families. Remarkable phenotypic variability at the individual, intrafamilial, and interfamilial level was observed for different NPS manifestations. Quantitative urinanalysis revealed proteinuria in 21.3% of individuals. Microalbuminuria was detected in 21.7% of subjects without overt proteinuria. Interestingly, nephropathy appeared significantly more frequent in females. A significant association was established between the presence of clinically relevant renal involvement in an NPS patient and a positive family history of nephropathy. We identified normal-tension glaucoma (NTG) and sensorineural hearing impairment as new symptoms associated with NPS. Sequencing of LMX1B revealed 18 different mutations, including six novel variants, in 28 families. Individuals with an LMX1B mutation located in the homeodomain showed significantly more frequent and higher values of proteinuria compared to subjects carrying mutations in the LIM domains. No clear genotype-phenotype association was apparent for extrarenal manifestations. This is the first study indicating that family history of nephropathy and mutation location might be important in precipitating individual risks for developing NPS renal disease. We suggest that the NPS phenotype is broader than previously described and that NTG and hearing impairment are part of NPS. Further studies on modifier factors are needed to understand the mechanisms underlying phenotypic heterogeneity.

Optic Nerve Head Topographic Measurements and Retinal Nerve Fiber Layer Thickness in Physiologic Large Cups

PURPOSE

To evaluate the parameters of optic nerve head (ONH) and retinal nerve fiber layer (RNFL) in patients with large cup/disc ratio (CDR) and normal neuroretinal rim configuration who have normal perimetry (physiologic large cups, LC) and to compare these parameters with those of the normal and early glaucoma patients.

METHODS

Using Heidelberg retinal tomography (HRT) and optical coherence tomography (OCT), 30 patients with LC, 29 normal subjects, and 31 early glaucoma patients were examined. One eye from each subject was randomly selected.

RESULTS

Significant differences between LC and glaucomatous eyes (GE) were found in parameters indicating loss of nerve fibers, such as rim area, rim volume, and mean RNFL thickness. However, there was no difference between LC and normal eyes (NE) in RNFL thickness, rim area, and rim volume. LC was able to be defined as a normal central excavation with a large disc and large CDR with a normal rim area.

CONCLUSIONS

HRT ONH parameters and RNFL thickness obtained with OCT may be useful for differentiating between glaucoma and LC eyes.

Clinical features and natural history of the acute idiopathic enlarged blind spot syndrome

OBJECTIVE

To study the clinical pattern and natural history of patients with the symptom of an enlarged blind spot.

DESIGN

A retrospective case series. Twenty-one patients were collected from a neuro-ophthalmologic practice during the period January 14, 1983, to July 1, 1996, and four consecutive patients were added from three vitreoretinal practices during the period April 14, 1986, to June 7, 1999.

PARTICIPANTS

Twenty-six eyes of 25 patients were studied at onset and at repeat visits from 1 year and 7 months to 15 years and 6 months later.

METHODS

The first visit was composed of a complete neuro-ophthalmologic examination with fundus photos and fluorescein angiography in 12 of the 26 eyes. Follow-up examination consisted of an interval history, ophthalmologic examination, visual fields, fundus photographs, fluorescein angiograms in eight eyes, indocyanine green angiograms in seven eyes, and multifocal electroretinograms (mfERG) in both eyes of seven patients.

MAIN OUTCOME MEASURES

The major outcome measures were onset and long-term visual field characteristics, disc and peripapillary features, association with other chorioretinal diseases, and mfERG features.

RESULTS

Twenty-one eyes had clinical features of chorioretinal syndromes, which are usually associated with an enlarged blind spot. Five eyes were examined too late after onset to expect such features. The visual field defect regressed in all but 12 eyes but never to an unequivocally normal-sized blind spot. Four of the 12 had chorioretinal scarring that corresponded to the permanent field defect. Twenty-one of 26 eyes had peripapillary scarring. The peripapillary scarring appeared the same no matter what the associated chorioretinal disease or type or size of field defect was. mfERG testing of seven patients at follow-up revealed first-order and second-order abnormalities long after clinical recovery, abnormalities that were bilateral even when the clinical signs had been unilateral.

CONCLUSIONS

If an eye with an enlarged blind spot is examined within 2 weeks of onset, signs of a chorioretinal disease will usually be present. Beyond that period, signs such as disc congestion, disc staining, peripapillary retinitis, foveal changes, and peripheral retinal spots may not be present. Although the patient usually becomes asymptomatic, the blind spot is slightly and permanently enlarged, and there is usually peripapillary disc scarring. mfERG testing indicates that retinal damage is more widespread, bilateral, and permanent than the visual field and clinical features would indicate. Chorioretinal syndromes that are associated with a temporal field defect have some features in common and others that are distinctive.

Telemedicine screening of glaucoma

OBJECTIVES

Glaucoma is a major cause of blindness. More than 80,000 Americans suffer permanent vision loss from the disease. Widespread screening is fundamental in limiting the incidence of glaucoma-associated blindness. This pilot study explored the use of stereo digital images taken at a primary care center for telemedicine review by an off-site specialist as a means of screening for glaucoma.

MATERIALS AND METHODS

Thirty-two diabetic patients were screened at a family medicine clinic. None had previously been diagnosed with glaucoma. A senior optometry student took stereoscopic digital and 35-mm optic disc photographs with a nonmydriatic retinal camera. The digital images were forwarded to a remote ophthalmologist for review. The conventional color stereo slide pairs of the same eyes were subsequently reviewed for comparison. Agreement on signs of glaucomatous disc changes between the two imaging systems was analyzed.

RESULTS

Twenty-six of 32 eyes' digital and 35-mm photographs were analyzed. Six of 32 eyes (18.8%) could not be compared due to lack of matching 35-mm slides or digital images. Out of 26 eyes, lamina cribosa visibility was undeterminable in 8 eyes' digital images and 3 other eyes' 35-mm slides. Agreement among digital images and 35-mm slides of the remaining eyes was: 100%-vertical elongation, barring of vessels, bayoneting of vessels, and drance hemorrhage; 96.2%-focus notching of rim and rim pallor; 93.3%-lamina cribosa visability; 92. 3%-overpass cupping; 88.5%-focal enlargement; 84.6%-parapapillary halo; 80%-nerve fiber visibility; 65.4%-parapapillary atrophy. Parapapillary halo (p = 0.046) and nerve fiber layer visibility (p = 0.18) were detected on some 35-mm slides but not seen on matching digital views.

CONCLUSION

Evaluations of cup-to-disc ratio (C/D) using both methods were in general agreement. However, some digital images were noted as too dark for assessing fine glaucomatous disc changes. Stereo digital images taken with a nonmydriatic camera by nonophthalmic photographers is a promising alternative for glaucoma screening in primary care settings. Telemedicine offers efficient communications with off-site glaucoma specialists. A larger study population is necessary to determine the overall effectiveness of using stereo digital imagery and teleophthalmology for glaucoma screening.

The normal optic nerve head

BACKGROUND

The normal optic nerve head varies from one person to another, and there is often intraindividual variation as well. Factors such as race and age play an important role in distinguishing what may be considered normal variations in optic nerve head appearance.

METHODS

A literature search and review of the latest studies on the optic nerve head was conducted.

RESULTS

Results of recent studies showed that variations in the average cup-to-disc ratio exist for different races, and with age there is a gradual loss of nerve fibers leading to an overall increase in the cup-to-disc ratio. There is also evidence that congenitally larger optic nerves have larger cup-to-disc ratios and more nerve fibers. Smaller optic nerves, in contrast, have smaller cup-to-disc ratios and fewer nerve fibers. These findings are presented along with sample photographs depicting the normal variations in optic nerve head appearance.

CONCLUSION

Over the past 30 years, technology has allowed for changing views about what may be considered normal in reference to the optic nerve head. This information is valuable to the eye care practitioner in helping to make appropriate patient care management decisions.

Optic disk appearances in primary open-angle glaucoma

Primary open-angle glaucoma almost certainly develops in a multifactorial manner, with interplay between numerous risk factors affecting the disease. These risk factors, in addition to intraocular pressure, include a number of cardiovascular factors. Some of these factors may determine the appearance of the damaged glaucomatous optic nerve head. Patients with four specific optic disk appearances have been investigated, and differences have been identified in their demographic characteristics, prevalence of certain risk factors, the pattern of visual field damage, and circulatory abnormalities in their retrobulbar vessels. The findings provide evidence of the existence of subgroups of primary open-angle glaucoma with correlations between risk factor and type of optic disk. A reliable method by which the different disk appearances could be distinguished in an objective manner would be clinically valuable, and the scanning laser ophthalmoscope has shown potential promise to achieve this. The results of studies relating to various glaucomatous optic disk appearances are presented and discussed.

Effect of aging on optic nerve appearance: a longitudinal study

AIM

To determine whether aging causes detectable changes in the appearance of the optic disc.

METHODS

A retrospective longitudinal study was performed with quantitative and qualitative evaluations of digitised stereoscopic optic disc photographs of 224 eyes of 224 subjects. There were three groups: 100 normal subjects from the Framingham Eye Study, 68 glaucomatous patients followed longitudinally, and 56 normal subjects and glaucoma patients who had separate sets of disc photos taken on the same day. A disc was considered qualitatively worse if two of three experienced observers agreed that it was worse. Quantitative progression was defined as a >10% decrease in rim/disc area ratio measured with computer assisted planimetry.

RESULTS

With quantitative evaluation, normal eyes (mean follow up 13 years) and same day eyes displayed no statistically significant difference in change of rim/disc area ratios (p=0.095), nor in the number of discs that progressed-five of 100 (5%) v two of 56 (4%) respectively. Glaucomatous eyes (mean follow up 9 years) showed a quantitative loss of disc rim in 24 of 68 (35%), and differed significantly from the normal eyes both in the change of rim/disc area ratio (p<0.0005) and number of discs that progressed (p<0.0005). With qualitative evaluation, the number of progressive discs in the glaucomatous eyes (31%) differed significantly (p<0. 0005) from the normal eyes (3%) and the same day eyes (0%).

CONCLUSIONS

Over a period of follow up appropriate for long term outcome studies in glaucoma, there was no quantitatively or qualitatively detectable neuroretinal rim loss in normal aging optic nerves with stereoscopic optic disc photographs.

Vertical cup/disc ratio in relation to optic disc size: its value in the assessment of the glaucoma suspect

AIMS

The vertical cup/disc ratio (CDR) has long been used in the assessment of the glaucoma suspect, though the wide range of CDR values in the normal population limits its use. Cup size is related physiologically to disc size and pathologically to glaucomatous damage. Disc size can be measured at the slit lamp as the vertical disc diameter (DD). The ability of the CDR, in relation to DD, to identify glaucomatous optic discs was investigated.

METHODS

88 normal, 53 early glaucoma, and 59 ocular hypertensive subjects underwent stereoscopic optic disc photography and clinical biometry. Photographs were analysed in a masked fashion by computer assisted planimetry. The relation between vertical cup diameter and DD was explored by linear regression, and expressed in terms of CDR. The upper limit of normal was defined by the 95% prediction intervals of this regression (method 1) and by the upper 97.5 percentile for CDR (method 2). The sensitivity and specificity of CDR to identify an optic disc as glaucomatous was tested with these disc size dependent and disc size independent cut offs in small, medium, and large discs.

RESULTS

The CDR was related to DD by the equation CDR = (-1.31 + (1.194 x DD))/DD. The sensitivity in small, medium, and large discs was 80%, 60%, and 38% respectively for method 1 and 33%, 67%, and 63% respectively for method 2. Specificity was 98.9% (method 1) and 97.7% (method 2).

CONCLUSIONS

The CDR, relative to disc size, is useful clinically, especially to assist in identifying small glaucomatous discs.

Effect of optic disc size or age on evaluation of optic disc variables

AIMS/BACKGROUND

It has been reported that the number of optic nerve fibres decrease with age, and the cup/disc (C/D) ratio increases as the optic disc size increases. Consequently, the normal value of the optic disc variables measured by an optic disc analyser may change according to the optic disc size or age. The effect of individual variations in optic disc size or age on interpretation of optic disc variables was investigated.

METHODS

Topographic optic disc variables of 104 normal Asian adults of both sexes aged 40 to 68 were measured using a confocal scanning laser ophthalmoscope (TopSS, Laser Diagnostic Technologies, Inc). Fourteen variables were evaluated according to the optic disc size or age. Statistical analysis was done by regression analysis.

RESULTS

With an increase in optic disc size, the increase in cup shape, effective area, 1/2 depth area, C/D ratio, neuroretinal rim area, volume above, volume below, and 1/2 depth volume were statistically significant (p < 0.05). However, contour variation, mean contour depth, average depth, maximum depth, average slope, and maximum slope were not affected (p > 0.1). Age did not have any significant influence on optic disc variables (p > 0.1).

CONCLUSION

Optic disc size, but not age, should be considered in the interpretation of optic disc variables.

Aging changes of the optic nerve head in relation to open angle glaucoma

AIMS

To determine the age related changes in optic nerve head structure in a group of normal subjects and assess the significance of any changes in relation to those found in open angle glaucoma.

METHODS

A group of 88 white volunteers and friends and spouses of patients with a normal visual field and normal intraocular pressure was studied. Two different imaging and measurement devices were used (computer assisted planimetry and scanning laser ophthalmoscopy), and the results from each were compared. Measurements were made of the optic disc, optic cup, and neuroretinal rim areas, and the vertical optic disc diameter and cup/disc diameter ratio.

RESULTS

Neuroretinal rim area declined at the rate of between 0.28% and 0.39% per year. Vertical optic cup diameter and optic cup area increased with age. The mean cup/disc diameter ratio increased by about 0.1 between the ages of 30 and 70 years.

CONCLUSIONS

Age related changes are significant and measurable, and should be taken into account when assessing the glaucoma suspect, and when estimating the rate of progression of glaucomatous optic neuropathy in patients with established disease.

Relationship between cup-disc ratio and optic disc diameter: the Blue Mountains Eye Study

PURPOSE

To determine the effects of optic disc size on vertical cup-disc ratio in subjects free of glaucoma and other optic nerve disease.

METHODS

Data were collected from 3654 people, 49 years of age of older, living in the Blue Mountains, west of Sydney (NSW, Australia). Examinations performed included subjective refraction and Zeiss colour stereo optic disc photographs. Eye and camera magnification effects were corrected.

RESULTS

Mean vertical disc diameter was 1.51 mm (95% confidence interval (CI) 1.504-1.516 mm) and the mean vertical cup-disc ratio was 0.43 (95% CI 0.425-0.435). Both parameters were distributed unimodally. The cup-disc ratio was strongly associated with disc diameter. Controlling for other variables, cup-disc ratio increased 0.270 (95% CI 0.250-0.290) per mm increase in disc diameter.

CONCLUSIONS

Vertical optic disc diameter and cup-disc ratio are distributed near normally in older Australians. Optic discs with larger vertical diameters have considerably greater vertical cup-disc ratios.

Interocular differences in optic disc configuration in the unilateral exfoliation syndrome

Thirty-seven patients with normal visual fields and open angles in both eyes, and lens exfoliation in only one eye, were examined for intraocular pressure, and optic disc topography was determined from stereophotographs of the fundi with the computerized three-dimensional image analyzer. The rim-to-disc radius ratios at intervals of 30 degrees were obtained with the instrument. The mean intraocular pressure of the exfoliative eyes (17.5 +/- 2.9 mmHg) was significantly higher than that of the nonexfoliative eyes (15.9 +/- 2.8 mmHg). In the exfoliative eyes, the mean rim-to-disc radius ratio at the inferior-temporal was significantly smaller, and the higher the intraocular pressure of the exfoliative eye in comparison with that of the nonexfoliative eye, the smaller were the rim-to-disc radius ratios at the inferior-temporal and inferior radii. In the exfoliative eyes, pressure-dependent changes are observable in the inferior and inferior-temporal areas of the optic disc prior to visual field loss.

Hyperopia as a risk factor for nonarteritic anterior ischemic optic neuropathy

The most convincing morphologic component in the pathogenesis of nonarteritic anterior ischemic optic neuropathy is the anatomically small and crowded optic nerve head. Because the appearance of the optic disk is presumed to be related to underlying refractive error, we sought to determine if a particular refractive error places patients at additional risk for, or affords protection from, nonarteritic anterior ischemic optic neuropathy. We compared refractive errors of 50 patients with nonarteritic anterior ischemic optic neuropathy to an age-matched and eye-matched control population. The mean refractive error (in spherical equivalents) for the nonarteritic anterior ischemic optic neuropathy group was +0.26 diopter (SD +/- 2.08); the mean refractive error for controls was -0.86 diopter (SD +/- 2.91) (P = .027). Our results suggest that patients who have nonarteritic anterior ischemic optic neuropathy are less myopic than a control population. Whether it is myopia that protects from, or hyperopia that predisposes to nonarteritic anterior optic neuropathy, our results imply another anatomically based factor that characterizes eyes that develop nonarteritic anterior ischemic optic neuropathy. Those eyes tend to be minimally hyperopic.

The neuroretinal rim in descending optic atrophy

We studied seven human eyes in which the changes of the neuroretinal rim areas following complete loss of all axons could be measured planimetrically. The mean diminution of the neuroretinal rim area was 40% (range from 26-72%). The optic nerve pathology causing the loss of axons was in the posterior portion of the nerve and the optic disc was therefore not directly disturbed by the injuries. It appears that less than half of the neuroretinal rim is occupied by nerve fibers.

Age-related decline of disc rim area in visually normal subjects

Optic disc parameters and axial lengths were measured in 81 visually normal young and elderly white adults (young [n = 41]: 27.2 +/- 5.7 years versus elderly [n = 40]: 68.8 +/- 8.4 years) using Rodenstock Optic Disc Analyzer and A-scan sonography. Axial lengths correlated positively with optic disc parameters (Spearman correlation analysis: rim area: P = 0.042, disc area: P = 0.052, and cup volume: P = 0.010). Older subjects had a shorter axial length (23.09 +/- 1.02 mm) and smaller disc rim area (1.171 +/- 0.338 mm2) than younger subjects (23.60 +/- 1.15 mm and 1.325 +/- 0.314 mm2; Mann-Whitney U test: P = 0.011 and P = 0.013, respectively). While both axial length and disc rim area declined with age (0.011 mm and 0.003 mm2 per year; Spearman correlation analysis: P = 0.032 and P = 0.020, respectively), the cup-to-disc and rim area-to-disc area ratios appeared to remain relatively constant throughout adult life. The age-related decline of disc rim area is consistent with histologic evidence of age-related decline of ganglion cell axons. The rim area-to-disc area ratio seems less affected by age, and is thus a better parameter to isolate age-related change from disease-related change of optic nerve in a longitudinal follow-up of diseases involving the optic nerve head.

Intraocular pressure-dependent dynamic changes of optic disc cupping in adult glaucoma patients

The authors performed a study of intraocular pressure-dependent changes in optic disc cupping in 17 adults with chronic open-angle glaucoma. Analyses with the Rodenstock Optic Nerve Head Analyzer were performed at baseline low intraocular pressure during therapy, after elevation of intraocular pressure (from therapeutic failure or noncompliance), and after reduction of intraocular pressure with successful therapy. Optic disc cupping increased significantly upon short-term increase of intraocular pressure from baseline of 20.4 +/- 2.5 mmHg to 31.1 +/- 5.9 mmHg. Optic disc cupping reverted to baseline after persistent intraocular pressure reduction to 19.3 +/- 4.8 mmHg. These data demonstrate intraocular pressure-dependent dynamic changes of optic disc cupping in patients with demonstrable glaucomatous optic nerve damage. They underscore the detrimental effect of elevated intraocular pressure and the beneficial effect of intraocular pressure reduction on optic disc cup changes.