Interocular asymmetry of optic disc size and its relevance to visual field loss in normal-tension glaucoma

Predictors of Glaucomatous Progression in Individuals with Small and Large Optic Discs

PURPOSE

To identify factors associated with glaucomatous progression in individuals with small and large optic discs.

DESIGN

Retrospective review.

SUBJECTS

4505 individuals with glaucoma at UCLA; 233 (59.7%) with small discs, 157 (40.3%) with large discs.

METHODS

Small and large disc sizes were defined by OCT or Heidelberg Retinal Tomography as disc area ≤ 5% (≤ 1.3 mm2) and ≥ 95% (≥ 2.9 mm2), respectively. Medical records were reviewed for demographics, systemic comorbidities, glaucoma type, ocular comorbidities, and ocular surgery. Logistic regression was used to identify predictors of visual field (VF) progression in individuals with small and large discs and predictors of large versus small discs.

MAIN OUTCOME MEASURES

The VF deterioration with mean deviation, pointwise linear regression, and glaucoma rate index (GRI); large vs. small disc.

RESULTS

In individuals with small discs, Asian versus non-Hispanic White ethnicity was associated with increased progression (adjusted odds ratio [aOR] = 4.05; 95% confidence interval [CI] = 1.12-14.59 for GRI). Higher intraocular pressure (IOP) range and peak were associated with increased progression in individuals with both small discs (aOR = 1.12; 95% CI = 1.00-1.27 and aOR = 1.05; 95% CI = 1.00-1.10 per 1 mmHg for range and peak with GRI) and large discs (aOR = 1.35; 95% CI = 1.12-1.66 and aOR = 1.11; 95% CI = 1.03-1.20 per 1 mmHg for range and peak with GRI). Multivariable predictors of having large vs. small discs included vasospastic phenotype (aOR = 2.58; 95% CI = 1.35-5.19) and Black (aOR = 20.46; 95% CI = 8.33-61.84), Hispanic/Latino (aOR = 9.65; 95% CI = 4.14-25.39), Asian (aOR = 4.87; 95% CI = 2.96-8.1), and other (aOR = 2.79; 95% CI = 1.69-4.63) versus non-Hispanic White ethnicity.

CONCLUSIONS

Increased odds of glaucomatous progression were associated with Asian vs. non-Hispanic White ethnicity in glaucoma patients with small optic discs, as well as with increased IOP range and peak in those with small and large discs. Individuals with a vasospastic phenotype and those from racial and ethnic minority backgrounds had increased odds of having large vs. small optic discs. Further characterization of discernible phenotypes would improve disease prognostication and help individualize glaucoma treatment.

FINANCIAL DISCLOSURE(S)

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

Optical Coherence Tomography-Derived Measurements of the Optic Nerve Head Structure of Aboriginal and Torres Strait Islander Children

PRCIS

This study demonstrated significant differences in optic nerve head characteristics in Aboriginal and Torres Strait Islander children compared with non-Indigenous children, which has implications for glaucoma risk and diagnosis in Aboriginal and Torres Strait Islander populations.

PURPOSE

The purpose of this study was to examine the optic nerve head (ONH) characteristics of visually normal Aboriginal and Torres Strait Islander children and non-Indigenous Australian children.

MATERIALS AND METHODS

Spectral domain optical coherence tomography imaging was performed on the right eye of 95 Aboriginal and Torres Strait Islander children and 149 non-Indigenous Australian children (5-18 years). Horizontal and vertical line scans, centered on the ONH, were analyzed to determine the dimensions of the ONH (Bruch membrane opening diameter), optic cup diameter, Bruch membrane opening minimum rim width, and the peripapillary retinal nerve fiber layer thickness.

RESULTS

The vertical but not horizontal Bruch membrane opening diameter of Aboriginal and Torres Strait Islander children was significantly larger than non-Indigenous children (mean difference: 0.09 mm, P = 0.001). The horizontal (mean difference: 0.12 mm, P = 0.003) and vertical cup diameter (mean difference: 0.16 mm, P < 0.001) were also significantly larger in Aboriginal and Torres Strait Islander children, as were the horizontal and vertical cup-to-disc ratios (both P < 0.01). Aboriginal and Torres Strait Islander children also had a significantly thinner Bruch membrane opening minimum rim width in the superior, nasal, and temporal meridians (all P < 0.001). Peripapillary retinal nerve fiber layer thickness did not differ between groups.

CONCLUSIONS

Differences exist in the ONH structure between Aboriginal and Torres Strait Islander children and non-Indigenous children, which may have implications for the detection and monitoring of ocular disease in this population and highlights the need to extend this research to the adult population.

Childhood-Onset Leber Hereditary Optic Neuropathy-Clinical and Prognostic Insights

PURPOSE

To investigate the clinical and molecular genetic features of childhood-onset Leber hereditary optic neuropathy (LHON) to gain a better understanding of the factors influencing the visual outcome in this atypical form of the disease.

DESIGN

Retrospective cohort study.

METHODS

We retrospectively included 2 cohorts of patients with LHON with onset of visual loss before the age of 12 years from Italy and the United Kingdom. Ophthalmologic evaluation, including best-corrected visual acuity, orthoptic evaluation, slit-lamp biomicroscopy, visual field testing, and optical coherence tomography, was considered. Patients were classified based on both the age of onset and the pattern of visual loss.

RESULTS

A total of 68 patients were stratified based on the age of onset of visual loss: group 1 (<3 years): 14 patients (20.6%); group 2 (≥3 to <9 years): 27 patients (39.7%); and group 3 (≥9 to ≤12 years): 27 patients (39.7%). Patients in group 2 achieved a better visual outcome than those in group 3. Patients in groups 1 and 2 had better mean deviation on visual field testing than those in group 3. The mean ganglion cell layer thickness on optical coherence tomography in group 2 was higher than those in groups 1 and 3. Patients were also categorized based on the pattern of visual loss as follows: Subacute Bilateral: 54 patients (66.7%); Insidious Bilateral: 14 patients (17.3%); Unilateral: 9 patients (11.1%); and Subclinical Bilateral: 4 patients (4.9%).

CONCLUSIONS

Children who lose vision from LHON before the age of 9 years have a better visual prognosis than those who become affected in later years, likely representing a "form frustre" of the disease.

Factors Related to a Right-Left Difference in Visual Field Defect in the Eyes with Untreated Normal Tension Glaucoma

Purpose

To investigate factors related to a right-left difference in visual field defect in untreated normal tension glaucoma (NTG).

Methods

The medical records of 92 patients with untreated NTG were reviewed. Ocular blood flow was evaluated with laser speckle flowgraphy, and the mean blur rate (MBR) at the optic nerve head was analyzed. Relationships between right-left differences in mean deviation (MD), intraocular pressure, MBR, spherical equivalent, central corneal thickness, and mean ocular perfusion pressure were evaluated using Spearman's rank correlation coefficient. Multiple regression analysis was used to detect factors contributing to a right-left difference in MD.

Results

The right-left difference in MD was correlated with differences in intraocular pressure (r = −0.263, P = 0.011), MBR (r = 0.417, P < 0.001), and spherical equivalent (r = 0.213, P = 0.042), but not with central corneal thickness or mean ocular perfusion pressure. Multiple regression analysis showed that a difference in MBR was the only significant contributor to a right-left difference in MD (slope 0.047, 95% confidence interval 0.025–0.069; P < 0.001).

Conclusion

In untreated NTG, a difference in blood flow at the optic nerve head was a significant contributor to a right-left difference in visual field defect.

Size of the Optic Nerve Head and Its Relationship with the Thickness of the Macular Ganglion Cell Complex and Peripapillary Retinal Nerve Fiber Layer in Patients with Primary Open Angle Glaucoma

Purpose. To evaluate the relationships among the optic nerve head (ONH) area, macular ganglion cell complex (mGCC) thickness, circumpapillary retinal nerve fiber layer (cpRNFL) thickness, and visual field defects in patients with primary open angle glaucoma (POAG). Methods. This retrospective study included 90 eyes of 90 patients with POAG. The ONH area, rim area, mGCC thickness, and cpRNFL thickness were measured using optical coherence tomography. Mean deviation (MD) was measured using standard automated perimetry. The relationships among clinical factors including age, refraction, the ONH area, the rim area, the mGCC thickness, the cpRNFL thickness, and MD were evaluated using correlation coefficients and multiple regression analyses. Results. The significant correlation of the ONH area with refraction (r = 0.362, P < 0.001), the mGCC thickness (r = 0.225, P = 0.033), and the cpRNFL thickness (r = 0.253, P = 0.016) was found. Multiple regression analysis showed that the ONH area, rim area, and MD were selected as significant contributing factors to explain the mGCC thickness and cpRNFL thickness. No factor was selected to explain MD. Conclusions. The ONH area, in other words, the disc size itself may affect the mGCC thickness and cpRNFL thickness in POAG patients.

Morphological features and important parameters of large optic discs for diagnosing glaucoma

Purpose

To compare the optic disc parameters of glaucomatous eyes to those of non-glaucomatous eyes with large discs.

Methods

We studied 225 consecutive eyes with large optic discs (>2.82 mm2): 91 eyes with glaucoma and 134 eyes without glaucoma. An eye was diagnosed with glaucoma when visual field defects were detected by the Humphrey Field Analyzer. All of the Heidelberg Retina Tomograph II (HRT II) parameters were compared between the non-glaucomatous and glaucomatous eyes. A logistic regression analysis of the HRT II parameters was used to establish a new formula for diagnosing glaucoma, and the sensitivity and specificity of the Moorfields Regression Analysis (MRA) was compared to the findings made by our analyses.

Results

The mean disc area was 3.44±0.50 mm2 in the non-glaucomatous group and 3.40±0.52 mm2 in the glaucoma group. The cup area, cup volume, cup-to-disc area ratio, linear cup/disc ratio, mean cup depth, and the maximum cup depth were significantly larger in glaucomatous eyes than in the non-glaucomatous eyes. The rim area, rim volume, cup shape measurement, mean retinal nerve fiber layer (RNFL) thickness, and RFNL cross-sectional area were significantly smaller in glaucomatous eyes than in non-glaucomatous eyes. The cup-to-disc area ratio, the height variation contour (HVC), and the RNFL cross-sectional area were important parameters for diagnosing the early stage glaucoma, and the cup-to-disc area ratio and cup volume were useful for diagnosing advanced stage glaucoma in eyes with a large optic disc. The new formula had higher sensitivity and specificity for diagnosing glaucoma than MRA.

Conclusions

The cup-to-disc area ratio, HVC, RNFL cross-sectional area, and cup volume were important parameters for diagnosing glaucoma in eyes with a large optic disc. The important disc parameters to diagnose glaucoma depend on the stage of glaucoma in patients with large discs.

Intraocular pressure reduction with topical medications and progression of normal-tension glaucoma: a 12-year mean follow-up study

PURPOSE

To investigate whether the amount of intraocular pressure (IOP) reduction with topical medications is associated with the progression of normal-tension glaucoma (NTG) and to identify risk factors for NTG progression.

METHODS

The medical records of 121 eyes of 121 NTG patients, who were treated with topical medications for more than 7 years, were reviewed. NTG progression was defined by either structural (optic disc or retinal nerve fibre layer) or functional (visual field) deterioration. Patients were divided into tertile groups according to the percentage IOP reduction from baseline, and the cumulative probability of NTG progression between upper and lower tertile group was compared using Kaplan-Meier survival analysis. Multivariate analysis with Cox's proportional hazard model was performed to identify the hazard ratio (HR) of clinical factors for NTG progression.

RESULTS

The average follow-up period was 12.2 years, and 56 of 121 eyes (46.3%) showed the NTG progression. Kaplan-Meier analysis revealed that upper tertile group (percentage IOP reduction >22.1%) showed a greater cumulative probability of non-progression than lower tertile group (percentage IOP reduction < 13.3%; p = 0.012). Multivariate Cox's proportional hazard model indicated that percentage reduction of IOP (HR = 0.964; p = 0.007) and the occurrence of disc haemorrhage (HR = 2.410; p = 0.008) were significantly associated with NTG progression.

CONCLUSIONS

The amount of IOP reduction using topical medications was related to NTG progression, and lower percentage reduction in IOP was a consistent risk factor for progression.

Optic disc size and progression of visual field damage in patients with normal-tension glaucoma

Purpose

Our goal was to evaluate the influence of optic disc size on the progression of visual field damage in patients with normal-tension glaucoma (NTG).

Subjects and methods

Eighty-two eyes of 82 NTG patients who had been receiving topical antiglaucoma medications and followed-up for more than 4 years were enrolled in this study. The patients were allocated to two groups, according to the mean size of their optic discs. The data were analyzed using regression analysis, based on the Cox proportional hazard model.

Results

The probability of visual field stability was significantly lower in eyes with large discs than in those with small discs (log rank test, P = 0.007). Progression of visual field damage was significantly associated with the optic disc area (hazard ratio [HR]: 1.812, P = 0.018), occurrence of disc hemorrhage (HR: 2.116, P = 0.028), and intraocular pressure reduction ratio (HR: 0.957, P = 0.014).

Conclusion

The optic disc area correlates with progression of visual field damage in patients with NTG.

Clock-hour laminar displacement and age in primary open-angle glaucoma and normal tension glaucoma

BACKGROUND

To find out the relationship between laminar displacement and age between patients with primary open-angle glaucoma and normal tension glaucoma.

DESIGN

Retrospective study conducted at a tertiary university hospital.

PARTICIPANTS OR SAMPLES

Twenty-six eyes of 26 primary open-angle glaucoma patients and 52 eyes of 52 normal tension glaucoma patients.

METHODS

Patients were scanned with a Stratus optical coherence tomography apparatus to measure the retinal nerve fibre layer thickness and to visualize the cross-sectional laminar displacement of 12 clock-hour segments, 30 degrees each. Depth1 was defined as the longest distance between the retinal pigment epithelium and the anterior laminar cribrosa surface, which represents the amount of laminar displacement.

MAIN OUTCOME MEASURE

Partial correlation coefficients adjusted by mean deviation and intraocular pressure between (i) retinal nerve fibre layer thickness and age, and (ii) Depth1 and age.

RESULTS

In the primary open-angle glaucoma group, strong negative correlations (approximately -0.343 ≈ -0.738) were found between Depth1 and age. Eight of 12 clock-hour segments' correlations were significant after Bonferroni correction (α = 0.0021; 24 comparisons). However, no significant correlations were found between Depth1 and age in the normal tension glaucoma group. When the correlation coefficients were compared between the two groups, eight clock-hour segments showed significant differences after Bonferroni correction.

CONCLUSIONS

The significantly different correlation between laminar displacement and age between primary open-angle glaucoma and normal tension glaucoma patients may suggest a different role of the lamina cribrosa to the disease.

Optic disc analysis with Heidelberg Retina Tomography III in glaucoma with unilateral visual field defects

PURPOSE

To find the optic disc features of asymmetric primary open-angle glaucoma.

METHODS

In this observational case-control study, 52 consecutive open-angle glaucoma patients with unilateral visual field defects participated. In each patient, an optic disc analysis using Heidelberg Retina Tomography III (HRT-III) was performed. Optic disc parameters of HRT-III of eyes with abnormal visual fields were compared with their fellow eyes with normal visual fields.

RESULTS

The optic disc area of the eyes with abnormal visual fields (2.35 +/- 0.55 mm(2)) was larger than that of the fellow eyes with normal visual fields (2.25 +/- 0.43 mm(2)) (P = 0.03). Of the eyes with abnormal visual fields, 63.5% had a larger optic disc area than their fellow eyes with normal visual fields. In addition, in the eyes with abnormal visual fields, the cup areas were larger (P = 0.000001-0.02), whereas the rim and retinal nerve fiber layer thicknesses were thinner (P = 0.000002-0.036) than those of the fellow eyes with normal visual fields.

CONCLUSIONS

The optic disc area of eyes with abnormal visual fields was larger than that of their fellow eyes with normal visual fields, suggesting that Chinese open-angle glaucoma patients with larger optic discs might be susceptible to glaucomatous optic damage.

Usefulness of frequency-doubling technology for perimetrically normal eyes of open-angle glaucoma patients with unilateral field loss

PURPOSE

To determine whether frequency-doubling technology (FDT) perimetry detects visual field loss in perimetrically normal eyes of patients with open-angle glaucoma (OAG) and whether these visual field defects subsequently are detected by standard automated perimetry (SAP), and to explore the relating factors of the progression from abnormalities based on FDT to visual field loss based on SAP.

DESIGN

Prospective cohort study.

PARTICIPANTS

Sixty-eight OAG patients with unilateral field loss detected by SAP (Octopus, G2 program; Interzeig, Schlieren, Switzerland).

METHODS

Perimetrically normal eyes of participants were examined with the FDT N-30 threshold program (Humphrey Instruments, Welch-Allyn, Skaneateles, NY). The visual field examination was followed by a series of SAP examinations administered over 3 years.

MAIN OUTCOME MEASURES

The relationship between FDT and subsequent SAP results in perimetrically normal eyes was analyzed. Glaucomatous optic neuropathy (GON), visual field indices, intraocular pressure (IOP), and central corneal thickness (CCT) were compared between converters (eyes with subsequent SAP abnormality) and nonconverters within perimetrically normal eyes with abnormal FDT results. Finally, the SAP test points were matched to the abnormal FDT sectors. The relative risk (RR) of subsequent SAP abnormality corresponding to FDT abnormal sectors was calculated.

RESULTS

Sixty perimetrically normal eyes of 60 participants had complete data and a qualifying follow-up. Baseline FDT results were abnormal in 65%. Of the eyes with abnormal FDT results, 51% developed abnormal SAP results after 4 to 27 months, whereas none of the eyes with normal FDT results developed abnormal SAP results (P<0.05). In perimetrically normal eyes with abnormal FDT results, converters had a greater cup-to-disc ratio, more eyes with GON, larger and deeper cups, and worse FDT mean deviation than nonconverters (P<0.05). The IOP and CCT did not differ between the 2 groups. The RR of subsequent SAP abnormality corresponding to abnormal FDT sectors was 5.38 (95% confidence interval, 3.61-8.04; P<0.05).

CONCLUSIONS

In perimetrically normal eyes of OAG patients, FDT detected visual field loss in almost 2 of every 3 of these eyes and also predicted to some extent future visual field loss on SAP. Severity of glaucomatous neuropathy at baseline was related to conversion of abnormalities on FDT to visual field loss on SAP.

Reproducibility of pattern electroretinogram in glaucoma patients with a range of severity of disease with the new glaucoma paradigm

PURPOSE

To determine the reproducibility of the pattern electroretinogram with the new Pattern Electroretinogram for Glaucoma (PERGLA) recording paradigm in glaucoma patients with a range of severity.

DESIGN

Experimental study.

PARTICIPANTS

Fifty-three glaucoma patients were recruited for the study (mean age +/- standard deviation [SD], 69+/-11 years). Their mean deviation (MD) global indices on static automatic perimetry ranged from 2.16 to -31.36 decibels (mean MD, -9.05).

INTERVENTION

All patients had pattern electroretinogram recordings done 5 times by the same operator, on 5 different days with the standardized PERGLA paradigm.

MAIN OUTCOME MEASURES

Pattern electroretinogram amplitude (microvolts), phase (pi radians), response variability (coefficient of variation [CV] = SD/mean x 100) of amplitude and phase of 2 partial averages that build up the pattern electroretinogram waveform, interocular asymmetry in amplitude and phase (in terms of the CV generated by the pattern electroretinogram software), signal-to-noise (S/N) ratio, SDs, CV, and intraclass correlation coefficient (ICC). All analyses were done on one eye of each subject, except when interocular asymmetry was studied.

RESULTS

The CVs of intrasession variabilities in amplitude and phase were 12.08% and 2.20%, respectively, and those of intersession variabilities were 20.82% and 4.17%. The pattern electroretinogram produced intersession ICCs in amplitude and phase of 0.791 and 0.765, respectively. These ICCs were significantly higher than the ICCs for pattern electroretinogram interocular asymmetry in amplitude and phase (0.659 [P<0.05] and 0.571 [P<0.05], respectively). On average, the pattern electroretinogram S/N ratio in glaucomatous patients was about 5:1.

CONCLUSIONS

The reproducibility of PERGLA in glaucomatous patients is sufficiently good for it to be considered a useful complementary clinical tool. Being more reproducible, direct measures of amplitude and phase should be more useful in monitoring progression than interocular asymmetry comparisons.

Intereye spatial relationship of abnormal neuroretinal rim locations in glaucoma patients from the diagnostic innovations in glaucoma study

PURPOSE

To determine the spatial relationship in neuroretinal rim parameter values between eyes in ocular hypertensives, glaucoma suspects, and glaucoma patients.

DESIGN

Observational-cross-sectional study.

METHODS

A total of 334 eyes of 167 patients were included. All patients underwent confocal scanning laser ophthalmoscopy imaging in both eyes. Intereye concordance ratio of abnormal rim sectors as classified by the Moorfield regression analysis (MRA) was calculated as the ratio of matching abnormal rim areas to the total number of abnormal rim areas. The amount of agreement was calculated for each sector separately.

RESULTS

Of the right (left) eyes, 39 (39) eyes were classified "borderline" (BL) by MRA, 62 (65) eyes were "within normal limits" (WNL), and 66 (63) eyes "outside normal limits" (ONL). A total of 78 patients had a normal overall MRA result in both eyes (BL = WNL). Of the 89 patients with a defect in at least one sector, mean intereye concordance was 0.28 +/- 0.04 (BL = WNL). When considering BL as ONL, concordance increased to 0.43 +/- 0.03. The lowest intereye agreement in rim abnormality was found in the temporal-inferior sector with 29.0% (Kappa +/- SE [standard error], 0.25 +/- 0.09, BL = WNL) matching. The highest agreement was found in the nasal- inferior sector with 47% (Kappa +/- SE, 0.53 +/- 0.1, BL = WNL) matching.

CONCLUSIONS

There is a moderate intereye agreement in abnormal neuroretinal rim locations in eyes of ocular hypertensives, glaucoma suspects, and glaucoma patients. Longitudinal studies are needed to elucidate the agreement over time and to better understand the morphological pattern of progression between eyes in glaucoma.

Optic disk size and glaucoma

Assessment of optic disk size is an important, but often overlooked, component of the diagnostic evaluation for glaucoma. Measured values of optic disk size vary with the measurement technique utilized. Available methods for disk size measurement and their respective strengths and limitations will be discussed. Further, actual disk size varies with race and possibly other demographic characteristics. Disk size is also associated with variation of specific anatomical structures of the optic nerve head and the retinal nerve fiber layer. These disk size- dependent variations may influence the susceptibility to glaucoma or the likelihood of glaucoma diagnosis. This manuscript reviews the published evidence relating to disk size and glaucoma.

Progressive ganglion cell loss and optic nerve degeneration in DBA/2J mice is variable and asymmetric

Background

Glaucoma is a chronic neurodegenerative disease of the retina, characterized by the degeneration of axons in the optic nerve and retinal ganglion cell apoptosis. DBA/2J inbred mice develop chronic hereditary glaucoma and are an important model system to study the molecular mechanisms underlying this disease and novel therapeutic interventions designed to attenuate the loss of retinal ganglion cells. Although the genetics of this disease in these mice are well characterized, the etiology of its progression, particularly with respect to retinal degeneration, is not. We have used two separate labeling techniques, post-mortem DiI labeling of axons and ganglion cell-specific expression of the βGeo reporter gene, to evaluate the time course of optic nerve degeneration and ganglion cell loss, respectively, in aging mice.

Results

Optic nerve degeneration, characterized by axon loss and gliosis is first apparent in mice between 8 and 9 months of age. Degeneration appears to follow a retrograde course with axons dying from their proximal ends toward the globe. Although nerve damage is typically bilateral, the progression of disease is asymmetric between the eyes of individual mice. Some nerves also exhibit focal preservation of tracts of axons generally in the nasal peripheral region. Ganglion cell loss, as a function of the loss of βGeo expression, is evident in some mice between 8 and 10 months of age and is prevalent in the majority of mice older than 10.5 months. Most eyes display a uniform loss of ganglion cells throughout the retina, but many younger mice exhibit focal loss of cells in sectors extending from the optic nerve head to the retinal periphery. Similar to what we observe in the optic nerves, ganglion cell loss is often asymmetric between the eyes of the same animal.

Conclusion

A comparison of the data collected from the two cohorts of mice used for this study suggests that the initial site of damage in this disease is to the axons in the optic nerve, followed by the subsequent death of the ganglion cell soma.

Pattern electroretinogram abnormality and glaucoma

PURPOSE

To determine the existence of retinal ganglion cell dysfunction and associated risk factors in glaucoma suspects with increased optic disc cupping and normal visual field.

DESIGN

Cross-sectional, observational study.

PARTICIPANTS

Two hundred glaucoma suspect (GS) patients were identified based on optic disc abnormalities (vertical cup-to-disc ratios [C/D]>0.5; vertical C/D asymmetry >or= 0.2; disc hemorrhages; notching) in association with known glaucoma risk factors (positive family history, African American descent, increased intraocular pressure [IOP]), but normal visual fields. Forty-two patients had early manifest glaucoma (EMG). Sixteen normal black subjects were added to update previous pattern electroretinogram (PERG) normative data and to establish a normal control (NC) group with a racial breakdown comparable with that of the study groups.

METHODS

Pattern electroretinograms were recorded simultaneously from both eyes using skin electrodes and automated analysis; visual fields were monitored with standard white-on-white automated perimetry (SAP) central 24-2 program; vertical C/D was evaluated by an independent reader from stereo disc photographs; and univariate and multivariate statistical analysis between PERG and other outcome measures was evaluated.

MAIN OUTCOME MEASURES

Pattern electroretinogram amplitude (microV), phase (pi rad), and interocular asymmetry in amplitude and phase (%); and SAP mean deviation (MD; decibels), vertical C/D, age (years), IOP (mmHg), and race (black vs. nonblack).

RESULTS

The PERG results were abnormal in at least 1 of the outcome measures in 52% of GS patients and 69% of EMG patients. The PERG amplitude was correlated weakly with both MD (P<0.01) and vertical C/D (P = 0.05). The correlation between PERG amplitude and MD and C/D was stronger (P<0.001) for interocular differences rather than absolute measures. Interocular PERG amplitude asymmetry increased with severity of disease (EMG>GS>NC; P<0.01). The PERG amplitude decline with age was steeper in patients with a more negative MD (P<0.01) and in patients with a more negative MD and a larger vertical C/D (P = 0.06). Black race (but not family history) was associated with lower PERG amplitude (P = 0.005) in GS and EMG patients, but not in normal controls (P = 0.44).

CONCLUSIONS

The correlation between PERG abnormality and known risk factors for glaucoma indicates that PERG has a predictive potential for the development or progression of the disease, or both.

Major determinants of optic nerve head topographic characteristics in a normal Turkish population

AIM

To determine the factors affecting the topographic characteristics of the optic nerve head in a normal Turkish population.

METHODS

A cross-sectional study was performed on the optic nerve head of the right eyes of 613 healthy subjects of both sexes aged 11-77 years using a confocal scanning laser ophthalmoscope. The study population was divided into three groups (<20 years, 20-50 years, and>50 years) to evaluate age-related changes in the optic nerve head topography. A total of 15 variables were determined. Statistical analysis was performed using Student's t-test, anova, Tukey HSD test, linear regression analysis and Pearson's correlation coefficient.

RESULTS

Four eyes were excluded from the study due to poor image quality. There were 307 female subjects and 302 male subjects. The mean age of the subjects was 42.1 +/- 15.1 years. The mean optic disc areas were 1.99 +/- 0.45 mm2 and 1.97 +/- 0.41 mm2 for male and female subjects, respectively. The disc area of the subjects ranged between 1.01 and 4.19 mm2. Disc area was found to be associated with all of the optic nerve head variables studied, and was also found to be significantly increased with advancing age (P < 0.05). The only variable that showed a sex-related difference was neuroretinal rim volume, which was found to be higher in female subjects in all cases.

CONCLUSION

Optic disc area was found to be the main determinant of the optic nerve head topography in a normal population. Optic disc area was found to be significantly increased with ageing in a normal population. These acquired changes to the optic disc could suggest stretching of the scleral ring, which may highlight the role of advancing age on the pathogenesis of glaucomatous optic neuropathy.

The optic nerve head in normal-tension glaucoma

There is controversy over the definition, appearance, and characteristics of the optic nerve head in normal-tension glaucoma (NTG). Optic disk size is greater in eyes with NTG than in those with primary open-angle glaucoma. However, in an intraindividual bilateral comparison, the eye with the larger optic disk showed neither more marked nor less pronounced glaucomatous optic nerve damage. Optic disk hemorrhage and peripapillary atrophy have been reported to be more frequent in patients with NTG. Nonuse of calcium channel blockers, peripapillary atrophy, and disk hemorrhage were statistically significantly associated with visual field loss progression in NTG. However, there is a possibility that a high IOP may stop disk hemorrhage relatively early. Histopathologic optic nerve head changes correlated with the clinical appearance of the optic nerve head, which is comparable in NTG and primary open-angle glaucoma. However, as novel findings, serum antibodies to retinal proteins and retinal immunoglobulin deposition in the ganglion cells were observed, and the level of serum autoantibodies to optic nerve head glycosaminoglycans was higher in patients with NTG than in patients with primary open-angle glaucoma.

Intraocular pressure as a risk factor for visual field loss in pseudoexfoliative and in primary open-angle glaucoma

OBJECTIVE

To analyze the relationship between intraocular pressure (IOP) and visual field loss in patients with primary open-angle glaucoma (POAG) and in those with pseudoexfoliative glaucoma (PEXG).

DESIGN

A cross-sectional, observational study.

PARTICIPANTS

Thirty-one patients with PEXG and 31 patients with POAG that was newly diagnosed were included in this study.

MAIN OUTCOME MEASURES

The authors recorded the untreated IOP and the amount of the visual field loss, at presentation, in both study groups.

RESULTS

The authors found a significant relationship between IOP and visual field mean deviation (MD) index (P = 0.0001, r = 0.68) in PEXG but not in POAG eyes (P = 0.7).

CONCLUSION

The authors found that untreated IOP levels can explain the amount of visual field loss, as measured by the MD index, much better in patients with PEXG than in comparable patients with POAG. Thus, vulnerability of the optic nerve head to increased IOP appears to be different in these two diagnostic categories.