Glaucoma is one of the leading causes of blindness worldwide. Primary open-angle glaucoma (POAG) is the most prevalent form of glaucoma and has a particularly devastating impact in blacks. In the ...black American population, POAG prevalence is estimated to be six times as high in certain age groups compared to whites. POAG is more likely to result in irreversible blindness, appears approximately 10 years earlier and progresses more rapidly in blacks than in whites. Racial differences in optic disk parameters have been reported and show that blacks have larger optic disks than whites. This finding is robust and may account for the reported differences in other optic disk parameters. The existence of racial differences in intraocular pressure remains to be demonstrated, as conflicting findings are reported in the literature. Intraocular pressure may actually be underestimated in blacks, perhaps because they have thinner corneas. The prevalence of diabetes and hypertension is higher in blacks than in whites, and although no causal relationship has been established between POAG and each of these systemic diseases, some reports suggest that they often occur together, perhaps through an indirect relationship with intraocular pressure. Compounding the problem, there is evidence that blacks are less responsive to both drug and surgical treatment for POAG. Finally, they often have reduced accessibility to treatment and are less aware of the risks of having POAG. This article provides a comprehensive review of the current knowledge pertaining to POAG in blacks.
To evaluate predictors of atypical birefringence patterns (ABP) observed in scanning laser polarimetry.
A total of 179 eyes from 82 normal subjects and 97 glaucoma patients were included. The retinal ...nerve fibre layer in each eye was imaged sequentially with GDx variable corneal compensation (VCC) and GDx enhanced corneal compensation (ECC) (Carl Zeiss Meditec, Dublin, California). The associations between the typical scan score (TSS) and age, axial length, spherical error, parapapillary atrophy (PPA) and visual-field mean deviation (MD) were evaluated with univariate and multivariate regression analyses.
23.5% (42/179) and 5.0% (9/179) of subjects had ABP (TSS<80) with GDx VCC and GDx ECC, respectively. For both GDx VCC and ECC, the TSS was significantly correlated with age, axial length, spherical error and PPA, but not with visual-field MD. After adjusting the effect of covariates, the axial length/spherical error and PPA were significantly associated with GDx VCC TSS, whereas the axial length/spherical error was the only predictor for GDx ECC TSS. Myopic eyes were more likely to develop ABP in both GDx VCC and ECC.
Axial length or spherical error is a significant predictor for ABP with both GDx VCC and GDx ECC. Caution should be exercised in interpreting the results of scanning laser polarimetry in eyes with a long axial length or myopia.
This is the sixth World Glaucoma Association Consensus. The relationship between ocular blood flow and glaucoma has been discussed for more than a century, and still it uniformly fuels debates at ...glaucoma meetings throughout the world. Clearly, the results of this report will have broad and significant impact on glaucoma research and clinical practice. The global faculty, consisting of leading authorities on the scientific and clinical aspects of ocular blood flow, have met in Fort Lauderdale on May 2, 2009 to discuss the reports and refine the consensus statements.
To determine, using anatomic measurements, whether daily oral dosing with memantine is both safe and effective to reduce the injury associated with experimental glaucoma in primates.
Argon laser ...treatment of the anterior chamber angle was used to induce chronic ocular hypertension (COHT) in the right eyes of 18 macaque monkeys. Nine animals were daily orally dosed with 4 mg/kg memantine while the other nine animals received vehicle only. Measurements of intraocular pressure (IOP) from both eyes of all animals were made at regular intervals. Appearance of the optic nerve head, retinal vessels, and surrounding retina was documented with stereo fundus photographs obtained at multiple time points throughout the study. Measurements of optic nerve head topography were obtained from confocal laser scans made from animals with the highest IOPs at approximately 3, 5, and 10 months after elevation of IOP. At approximately 16 months after IOP elevation, animals were killed and histologic counts of cells in the retinal ganglion cell (RGC) layer were made.
Histologic measurements showed that, for animals with moderate elevation of IOP, memantine treatment was associated with an enhanced survival of RGCs in the inferior retina. Measurements of optic nerve head topography showed less IOP-induced change in memantine-treated animals. This effect was seen in measurements of both the cup and the neuroretinal rim. A comparison of these same histologic and morphologic measurements in normotensive eyes from the two treatment groups showed that memantine treatment was not associated with any significant effects on these eyes.
Histologic measurements of RGC survival as well as tomographic measurements of nerve head topography show that systemic treatment with memantine, a compound which does not lower intraocular pressure, is both safe and effective to reduce changes associated with experimental glaucoma.
The cellular mechanisms mediating intraocular pressure reduction following topical prostaglandin (PG) treatments are poorly understood. To determine if PG treatments might induce altered metabolism ...of extracellular matrix surrounding ciliary muscle cells, confluent human ciliary smooth muscle cell cultures were exposed to PGF
2α, 17-phenyltrinor-PGF2
2α, or 11-deoxy-PGE
1 for one to four days and the distributions of collagen types I, III and IV as well as laminin were determined immunocytochemically. In addition, collagen type 1V and promatrix metalloproteinase III (proMMP-3) content within treated cultures was determined using sandwich ELISAs. Compared with vehicle-treated cultures, there were substantial reductions in the density and branching of the collagen type IV-imnmnoreactive lattice accompanied by thickening of remaining strands in all PG-treated cultures. Similar changes were seen in the distribution of laminin within all PG-treated cultures. Reductions in collagen type III immunoreactivity were seen in cultures treated with either PGF
2α or 17-phenyltrinor-PGF
2α . No changes were observed in collagen type I immunoreactivity. Quantitative analyses revealed increased amounts of collagen type IV in both the culture medium and in extracts of the cell layer in all PG-treated cultures. In addition, there were substantial increases in the concentrations of proMMP-3 in all PG-treated cultures. These results indicate that PGs induce increased turnover and remodeling of ECM adjacent to ciliary muscle cells. Such changes may contribute to increased uveoscleral outflow in vivo following topical PG treatment.
To evaluate optic nerve damage in mice after laser-induced ocular hypertension.
Ocular hypertension was induced unilaterally in 13 NIH Black Swiss mice by laser photocoagulation of the limbus. Over ...the following 12 weeks, intraocular pressure (IOP) was measured at regular intervals by the microneedle method. The optic nerves of these mice and of seven normal untreated mice were then processed conventionally for electron microscopy, and cross sections of the nerve 300 micro m posterior to the globe were collected. Low- and high-magnification images were collected systematically and masked before analysis. For each nerve, cross-sectional area was measured in low-magnification micrographs, and axon and glia numbers were counted in high-magnification micrographs.
In normal untreated mice, the average number of axons was 59,597 +/- 3,112 (mean +/- SD). Variation among these measurements was 5.7% +/- 3.9%. After laser treatment, the duration of high IOP ranged from 2 to 12 weeks (6.2 +/- 3.6 weeks, mean +/- SD). The mean IOP in the treated eyes was 1.3 times greater than the mean IOP in the control eyes (P = 0.0012). The maximum IOP in the treated eyes was 1.6 times greater than that observed in the control eyes (P < 0.0001). The optic nerve cross-sectional area, mean axon density, and total number of axons in the treated eyes were significantly less than in the control eyes (28.5% +/- 23.4%, 57.8% +/- 37.8%, and 63.1% +/- 38.1%, respectively; P < 0.005 for each). The decrease in optic nerve cross-sectional area and the positive integral of elevated IOP and duration of IOP elevation correlated significantly with total axon loss (r(2) = 0.79, P < 0.0001 and r(2) = 0.36, P = 0.040, respectively). The number of astrocytes per cross section of optic nerve was significantly greater in the treated eyes than in the control eyes (P = 0.014).
Laser-induced ocular hypertension in mouse eyes can induce optic nerve axon loss that correlates with the magnitude and duration of elevated IOP.
To investigate the peripapillary region in glaucomatous eyes by indocyanine green angiography.
Indocyanine green angiography of the optic disk and peripapillary region was evaluated by modified ...confocal scanning laser ophthalmoscopy in 22 eyes of 22 patients with glaucoma and in 10 normal eyes of 10 control patients with unilateral choroidal melanoma. The occurrence and extent of indocyanine green angiographic anomalies were correlated with optic disk morphology and the severity of glaucoma.
In the 32 eyes of 32 patients, two types of peripapillary defects were identified in the late-phase angiograms. The first was hypofluorescent areas in the peripapillary region and was more common in eyes with glaucoma (P < .02); their occurrence and extent correlated with age (P < .01). In nine of the 17 eyes, alpha (peripheral) zone peripapillary atrophy corresponded with the areas of peripapillary indocyanine green hypofluorescence. The second defect, hypofluorescent halos adjacent to and extending around the full circumference of the optic disk margins, did not correlate with any of the study factors.
Indocyanine green angiography showed areas of hypofluorescence in the peripapillary region in late-phase angiograms in 68% of glaucomatous eyes compared with 20% of control eyes. These hypofluorescent areas might be either the result of blockage of background fluorescence by pigment or caused by an absence of vascular tissue (choriocapillaris).
To determine the relationship between areas of glaucomatous retinal nerve fiber layer thinning identified by optical coherence tomography and areas of decreased visual field sensitivity identified by ...standard automated perimetry in glaucomatous eyes.
Retrospective observational case series.
Forty-three patients with glaucomatous optic neuropathy identified by optic disc stereo photographs and standard automated perimetry mean deviations >−8 dB were included.
Participants were imaged with optical coherence tomography within 6 months of reliable standard automated perimetry testing.
The location and number of optical coherence tomography clock hour retinal nerve fiber layer thickness measures outside normal limits were compared with the location and number of standard automated perimetry visual field zones outside normal limits. Further, the relationship between the deviation from normal optical coherence tomography–measured retinal nerve fiber layer thickness at each clock hour and the average pattern deviation in each visual field zone was examined by using linear regression (
R
2).
The retinal nerve fiber layer areas most frequently outside normal limits were the inferior and inferior temporal regions. The least sensitive visual field zones were in the superior hemifield. Linear regression results (
R
2) showed that deviation from the normal retinal nerve fiber layer thickness at optical coherence tomography clock hour positions 6 o'clock, 7 o'clock, and 8 o'clock (inferior and inferior temporal) was best correlated with standard automated perimetry pattern deviation in visual field zones corresponding to the superior arcuate and nasal step regions (
R
2 range, 0.34–0.57). These associations were much stronger than those between clock hour position 6 o'clock and the visual field zone corresponding to the inferior nasal step region (
R
2 = 0.01).
Localized retinal nerve fiber layer thinning, measured by optical coherence tomography, is topographically related to decreased localized standard automated perimetry sensitivity in glaucoma patients.
PURPOSE:
To quantify and compare, on a point-by-point basis, the long-term variability of standard and short-wavelength automated perimetry in a group of stable glaucoma patients.
METHODS:
From a ...group of 53 glaucoma patients experienced in visual field testing, we identified one eye, randomly chosen, from each of 25 glaucoma patients whose condition was found to be stable, based on both standard and short-wavelength automated perimetry visual field criteria. On each of three visits during a period of up to 3 months, each patient performed one standard and one short-wavelength automated perimetry 24-2 visual field in a random order on a Humphrey visual field analyzer. The long-term variability (also referred to as test-retest variability) was defined as the SD of the three threshold decibel values at each test location. The long-term variability for each test point (mean ± SD) was determined separately for both standard visual fields and short-wavelength automated perimetry.
RESULTS:
With all 52 test locations of the 24-2 field averaged, the global long-term variability, mean (± SD) for standard visual fields and short-wavelength automated perimetry was 2.37 ± 2.03 dB (95% confidence interval, 2.26–2.48 dB) and 2.92 ± 2.03 dB (95% confidence interval, 2.81–3.03 dB), respectively (
P < .0001). In 16 of the 52 visual field locations, long-term variability on short-wavelength automated perimetry was significantly higher than long-term variability on standard visual fields. In addition, the long-term variability increased with greater distance from the point of fixation for both standard visual fields and short-wavelength automated perimetry. The long-term variability decreased closer to fixation, more for standard visual fields than for short-wavelength automated perimetry.
CONCLUSIONS:
In a group of stable glaucoma patients, mean long-term variability was 0.55 dB higher for short-wavelength automated perimetry than for standard visual fields. This needs to be taken into consideration when serial visual fields are evaluated for change.
