The regional distribution of diabetic retinopathy lesions may reflect risk factors for progression of the disease

BACKGROUND

Diabetic retinopathy is graded by semi-quantitative assessment of the morphological lesions as seen on fundus photographs. This grading method mainly considers the type and number of retinopathy lesions, implying that the diagnostic value of the regional distribution of retinopathy lesions is largely unknown.

DESIGN AND METHODS

Case control design. The study group consisted of fifteen diabetic patients successively examined in a screening clinic, with retinopathy lesions predominantly around the larger vascular arcades. The control group consisted of fifteen patients pairwise matched with the patients in the study group regarding sex, age, diabetes type, and diabetes duration. The two groups were compared with respect to the distribution of individual retinal lesions (microaneurysms/dot haemorrhages, blot haemorrhages, cotton wool spots, and hard exudates) around the larger vascular arcades and in the macular area, hypertensive vascular abnormalities (crossing phenomena, arteriolar narrowing, arteriolar light reflex), metabolic regulation, and blood pressure.

RESULTS

The patients in the study group had significantly more microaneurysms and haemorrhages around the larger vascular arcades than had the control group, but there was no difference between the vascular changes in the two groups. The study group had significantly higher blood pressure than had the control group, whereas there was no significant difference in metabolic regulation between the two groups.

CONCLUSIONS

The findings suggest the existence of a hypertensive-like retinopathy in diabetic patients with lesions mainly around the larger vascular arcades, but with no increase in hypertensive vascular changes. This pattern is not identified with current semi-quantitative grading methods. Further improvement of clinical decisions made from fundus photographs of diabetic retinopathy requires the development of computerised methods for quantitative assessment of retinal lesions.

Increased elastin expression in astrocytes of the lamina cribrosa in response to elevated intraocular pressure

PURPOSE

To determine whether abnormal elastin synthesis in the glaucomatous optic nerve head and lamina cribrosa is due to elevated intraocular pressure (IOP) or secondary to axonal injury, monkeys with elevated IOP and with optic nerve transection were compared.

METHODS

Unilateral, chronic elevated IOP was induced in 11 rhesus monkeys by laser scarification of the trabecular meshwork. IOP was monitored weekly and maintained within 25 to 45 mm Hg for 7 to 36 weeks. In 6 monkeys, unilateral, optic nerve transection was performed, and monkeys were killed after 4 weeks. Optic nerve damage was assessed by stereoscopic slit-lamp biomicroscopy and fundus photography and by confocal scanning laser ophthalmoscopy. The eyes were enucleated and processed for immunohistochemistry and in situ hybridization and for electron microscopic immunogold detection of elastin. Axonal loss was evaluated in cross sections of the optic nerve stained with phenylenediamine.

RESULTS

Compared with normal contralateral controls, the lamina cribrosa of eyes with elevated IOP exhibited markedly increased elastin and the presence of elastotic aggregates in the extracellular matrix and upregulation of elastin mRNA in the astrocytes. In transected eyes, elastin appeared as fine fibers in the lamina cribrosa, without elastotic aggregates, and without new synthesis or abnormal deposition of elastin. At the transected site, new synthesis of elastin was present in the pia mater but not in astrocytes in the glial scar.

CONCLUSIONS

This study demonstrates that abnormal elastin synthesis in experimental glaucomatous optic neuropathy in the monkey is specific to elevated IOP and not secondary to axonal loss. The mechanisms by which elevated IOP induces enhanced elastin synthesis in laminar astrocytes are unknown but differ from those involved in acute axonal injury such as transection, where inflammation and breakdown of the blood-nerve barrier occur.

Changes in Thy1 gene expression associated with damaged retinal ganglion cells

PURPOSE

The temporal series of molecular events that occur in dying retinal ganglion cells is poorly understood. We have examined the change in expression of a normally-expressed ganglion cell marker gene, Thy1, relative to the kinetics of cell loss caused by acute and chronic damaging stimuli.

METHODS

For acute experiments, mice were subjected to optic nerve crush or intravitreal injections of N-methyl-D-aspartate (NMDA) to induce ganglion cell death. RNase protection analysis was used to quantify Thy1 mRNA levels from total retina RNA and in situ hybridization was used to monitor the pattern of Thy1 positive cells. Changes in Thy1 expression were compared to the time course of cell loss induced by each treatment. To induce elevated intraocular pressure (IOP), the episcleral veins of rats were injected with hypertonic saline, which scleroses Schlemm's Canal and the trabecular meshwork. Elevated IOP was monitored every day for 35 days after which the animals were sacrificed and the retinas harvested for quantitative RT-PCR or fixed for in situ hybridization studies. Evaluation of glaucomatous damage caused by elevated IOP was determined from histological sections of the optic nerves of all rat eyes.

RESULTS

After optic nerve crush, Thy1 mRNA levels decreased within 24 h, although the number of expressing cells did not decline until 7 days. Both measures showed a loss of Thy1 well in advance of cell loss, which was detected by 2 weeks after surgery. This change in expression was not dependent on execution of the cell death program since a similar decrease was detected in Bax-/- ganglion cells, which are resistant to cell death induced by optic nerve crush. Thy1 mRNA levels and the number of expressing cells also decreased within 6 h after NMDA injection, in advance of cell loss, which was detected by 24 h. Similarly, elevated intraocular pressure was associated with a decrease in mRNA and expressing cells in a pressure-dependent manner. In moderately hypertensive rat eyes, the number of cells expressing Thy1 decreased before significant cell loss in the retina. Virtually no Thy1-expressing cells were detected in eyes with severe disease.

CONCLUSIONS

Thy1 mRNA abundance and expressing cells, decreased in advance of detectable ganglion cell loss caused by three different modalities of damage. This change is independent of the committed step of cell death.

Role of alpha-2 adrenergic receptors in neuroprotection and glaucoma

The loss of retinal ganglion cells (RGCs) in glaucoma occurs progressively over many years. A neuroprotective drug should enhance survival of RGCs in the presence of chronic stress/injury. Four criteria are proposed for assessing the likely therapeutic utility in human glaucoma of drugs that have demonstrated neuroprotective activity in animal models: 1) A specific receptor target must be in the retina/optic nerve; 2) Activation of the target must trigger pathways that enhance a neuron's resistance to stress/injury and/or suppresses toxic insults; 3) The drug must reach the retina/vitreous at pharmacologic doses; and 4) The neuroprotective activity should be demonstrated in clinical trials. Data are presented that illustrate how the specific and potent alpha-2 agonist, brimonidine, meets these criteria. The alpha-2A receptor was localized in the inner rat retina by immunohistochemistry. Brimonidine reduced the rate of RGC loss in the calibrated rat optic nerve injury model even when dosed 12 and 24 hours before injury, consistent with a long-term enhancement of RGC resistance to stress. Brimonidine was also neuroprotective in the lasered chronic hypertensive rat model, reducing RGC loss over three weeks from 33% to 15%. A clinical trial has been initiated to determine brimonidine's neuroprotective activity in patients with non-arteritic ischemic optic neuropathy.

Factors associated with elevated intraocular pressure in eyes with iris melanoma

AIM

To identify clinical factors associated with secondary elevated intraocular pressure (IOP) in eyes with iris malignant melanoma

METHODS

A retrospective case series of 169 consecutive patients with microscopically confirmed iris malignant melanoma. The main outcome measure was the presence of tumour induced secondary elevated IOP. Cox proportional regression models were used to calculate the relation of clinical features to elevated IOP.

RESULTS

Of 169 patients with microscopically proved iris melanoma, 50 (30%) presented with tumour induced secondary elevated IOP. The mean pressure in those eyes with elevated IOP at diagnosis was 33 mm Hg (median 31 mm Hg, range 23-65 mm Hg). The tumour configuration was nodular in 23 (46%) and diffuse in 27 (54%) with a mean base dimension of 7.4 mm and thickness of 2.0 mm. Invasion of the angle structures by melanoma seeds was visible for a mean of 7 clock hours (median 7, range 0-12 clock hours). The mechanism of elevated IOP was judged to be outflow obstruction from tumour invasion into the trabecular meshwork. There were no cases of neovascular glaucoma. The tumour was ultimately managed with enucleation in 30 patients (60%), local resection (iridectomy, iridocyclectomy, or iridocyclogoniectomy) in 11 (22%), and plaque radiotherapy in five (10%). In four cases (8%), observation of cytologically low grade tumour was the patient's preference. Using multivariate analysis, the clinical factors at initial evaluation associated with tumour induced secondary elevated IOP from iris melanoma included increasing extent of tumour seeding in the anterior chamber angle (p=0.01) and poor visual acuity at presentation (p=0.02).

CONCLUSIONS

Microscopically confirmed iris melanoma demonstrates tumour related elevated IOP in 30% cases at the time of presentation, usually secondary to tumour involvement of the trabecular meshwork obstructing aqueous outflow. Enucleation is necessary in the majority of these patients (60%) as opposed to those cases without elevated intraocular pressure (18%).

[A study on susceptibility of different layers of rabbit retina to ocular hypertension]

OBJECTIVE

To investigate the histological damage and its degrees of different layers of rabbit retina induced by ocular hypertension.

METHODS

The intraocular pressure (IOP) was elevated by intracameral injection of 0.10 - 0.15 ml of 2% methylcellulose in sixteen gray rabbits. The rabbit eyes were enucleated, fixed, and paraffin-embedded. For histological evaluation, the slides were stained with hematoxylin-eosin, examined by light microscopic and computer automatic image analysis.

RESULTS

The quantitative analysis indicated that all of the retinal layers have different degrees of histopathological damage. Among them, the retinal ganglion cells (RGCs) and retinal nerve fiber layer (RNFL) were most severely damaged, with the decrease rate of 74.3% and 61.9%, respectively. The decrease rates of other retinal layers were as follows: the retinal inner layer, 42.4%; the whole sensory layer of the retina, 35.0% and the outer layer, 24.2%. We also found a significant correlation between RGCs loss and RNFL thinning (r = 0.68, P < 0.01), demonstrating a strong correlation between IOP level and RNFL thickness (F = 8.97, P < 0.01).

CONCLUSION

All of the anatomic layers of retina can suffer from degeneration and atrophy at different degrees.

Glucocorticoid induction of the glaucoma gene MYOC in human and monkey trabecular meshwork cells and tissues

PURPOSE

To examine the intracellular and extracellular expression of myocilin in the human and primate trabecular meshwork (TM) in the presence and absence of glucocorticoids.

METHODS

Myocilin expression was examined in cultured human TM cells by Northern blot analysis and myocilin antibody-mediated immunoprecipitation. Myocilin expression was quantified using high-resolution two-dimensional polyacrylamide gel electrophoresis of radiolabeled proteins from human TM cells, TM tissue explants, and perfused human anterior segments cultured with and without dexamethasone (DEX) for 14 to 21 days, as well as TM tissue from pigtailed monkeys treated orally for 1 year with cortisone acetate. Immunofluorescence with anti-myocilin antibodies was used to localize cellular and extracellular expression of myocilin in cultured human TM cells.

RESULTS

Glucocorticoid treatment caused a significant induction of myocilin mRNA, a tetrad of cell-associated proteins, and 8 to 20 secreted proteins (molecular mass [M(r)] 56 and 59 kDa and isoelectric point [pI] 5.2 and 5.3) in some, but not all the cultured human TM cells and explanted tissues. Western immunoblot analysis using anti-myocilin peptide antibodies identified these proteins as encoded by the MYOC gene. There was significant induction of the myocilin proteins in three perfusion-cultured human eyes, in which DEX-induced elevated intraocular pressure developed. Monkeys treated 1 year with cortisol acetate showed steroid glaucoma-like morphologic changes in the TM that correlated with the induction of myocilin in the TM. Immunofluorescence analysis of cultured TM cells localized myocilin intracellularly in discrete perinuclear and cytoplasmic vesicular deposits as well as extracellularly on the cell surface associated with the extracellular matrix. In several DEX-treated TM cell lines, there were significant levels of myocilin secreted into the media. Enzymatic deglycosylation of proteins in the TM media converted the higher molecular weight isoforms of myocilin (approximately 57 kDa) to the lower molecular weight isoforms ( approximately 55 kDa).

CONCLUSIONS

Although the function of myocilin is unknown, induction of these TM proteins was found in eyes in which glucocorticoid-induced ocular hypertension developed. Therefore, myocilin may play an important pathogenic role in ocular hypertension in addition to its role in certain forms of POAG.

Central corneal thickness measurements in patients with normal tension glaucoma, primary open angle glaucoma, pseudoexfoliation glaucoma, or ocular hypertension

BACKGROUND/AIMS

Recent studies have revealed patients with ocular hypertension to have thicker than normal central corneas and those with normal tension glaucoma to have thinner than normal ones, as determined by ultrasonic pachymetry. Since corneal thickness measurements and applanation tonometric estimates of intraocular pressure (IOP) correlate positively, monitoring of the former parameter have served as the basis for adjusting readings pertaining to the latter, with the consequence that many patients have had to be reclassified. With a view to validating these pachymetric studies, the central corneal thickness was determined in patients with normal tension glaucoma, primary open angle glaucoma, pseudoexfoliation glaucoma, or ocular hypertension, as well as that of normal subjects, using optical low coherence reflectometry, which is a new and more precise method than ultrasonic pachymetry.

METHODS

34 patients with normal tension glaucoma, 20 with primary open angle glaucoma, 13 with pseudoexfoliation glaucoma, and 12 with ocular hypertension, together with 21 control subjects, were included in this observational, concurrent case-control study. One eye per individual was randomly selected for investigation. IOP was measured by Goldmann applanation tonometry and central corneal thickness by optical low coherence reflectometry.

RESULTS

Central corneal thickness was significantly higher (p < or =0.001) in patients with ocular hypertension than in normal individuals or in subjects with either normal tension glaucoma, primary open angle glaucoma, or pseudoexfoliation glaucoma, there being no significant differences between the latter four groups. Patients with ocular hypertension were also significantly younger (p < or =0.003) than those within any of the three glaucomatous groups.

CONCLUSION

This study confirms that a significant number of patients with ocular hypertension have normal IOPs after the appropriate adjustments have been made for deviations from normal in their central corneal thickness. The accurate measurement of this latter parameter is important not only for individual patient care, in permitting more precise estimations of IOP, but also for clinical studies, in assuring a more reliable classification of subjects.

Induction of heat shock protein 72 protects retinal ganglion cells in a rat glaucoma model

PURPOSE

To investigate whether heat shock protein (Hsp) 72 is induced in retinal ganglion cells (RGCs) in experimental rat glaucoma and whether the induction of Hsp72 by heat stress or zinc (Zn(2+)) administration can increase survival of RGCs in the model.

METHODS

Intraocular pressure (IOP) was elevated unilaterally in Wistar rats with argon laser irradiation of the trabecular meshwork 5 days after intracameral injection of india ink. Immunohistochemical staining for Hsp72 was performed. The rats with elevated IOP were treated with heat stress once a week (six rats) or intraperitoneal injection of zinc (10 mg/kg) every two weeks (six rats). Untreated rats with elevated IOP served as a control group (six rats). Quercetin, an inhibitor of Hsp expression was injected in the rats with heat stress (six rats) and zinc injection (seven rats). Subsequent to 4 weeks of IOP elevation, RGCs were counted.

RESULTS

The IOP increase compared with the contralateral eyes was 48% +/- 4% throughout the study period. Hsp72 was detected only in the eyes with elevated IOP at 1 and 2 days and was weakly detected at 1 week of IOP elevation. A single administration of zinc strongly induced Hsp72 in RGCs of rats with elevated IOP for 2 weeks. Treatment with heat stress or zinc in rats with elevated IOP increased RGC survival after 4 weeks of IOP elevation, compared with the untreated control group (P = 0.004, n = 6). Quercetin reversed the positive effect of heat stress or zinc injection on RGC survival.

CONCLUSIONS

These results demonstrate the possibility of a novel therapeutic approach to glaucoma through an enhanced induction of the endogenous heat shock response.

Experimental ocular acute hypertension-induced chromatinic alterations in astrocytic cells in rat optic nerve

The effects of ocular acute hypertension experimentally induced on the astrocyte cells of rat have been studied. Evaluation was made of the damage to the chromatin of those cells by means of cytochemical (haematoxylin-eosin) analysis and of the state of fragmentation of the DNA by means of the TUNEL technique as well as the protective effect of the peroxide scavenger, troxol, on those events.

[Early glaucomatous changes in neuroretinal rim shape]

PURPOSE

To assess the differences in neuroretinal rim shape in ocular hypertensive patients (normal white-white automated perimetry) with and without perimetric injury in the short wave length automated perimetry (blue-yellow).

MATERIAL AND METHODS

72 eyes from 72 hypertensive ocular patients with normal achromatic automated perimetry examination were included. Forty eyes had normal short wave length automated perimetries while 32 subjects presented an abnormal condition. The neuroretinal rim morphology was quantified by means of a planimetric study from the papillary images obtained with confocal laser scanning.

RESULTS

The subjects with abnormal blue-yellow perimetry showed a decrease in the neuroretinal rim area in the inferior and temporal positions. The differences were significant (p<0.05) at the 9 o'clock position (below the middle line) and almost significant (p<0.10) at the 10 o'clock position.

CONCLUSIONS

There are differences in the neuroretinal rim shape in ocular hypertensive subjects with normal achromatic perimetry according to whether there are abnormalities in the blue-yellow perimetry.

Effects of increased intraocular pressure on rat retinal ganglion cells

The effects of elevated intraocular pressure (IOP) on the morphology of rat retinal ganglion cells (RGCs) was analyzed in this study. After cauterizing two limbal derived episcleral veins, IOP in experimental eyes was elevated 1.5--1.8 times that of control. RGCs of experimental and control eyes were analyzed after: bilateral tectal injections of Fluoro-Gold, and application of fluorescent dye crystals, 4-Di-10-ASP to the proximal stump of the cut optic nerve, at different time intervals after IOP elevation. The RGCs in control and experimental eyes were evaluated at 4, 6, 8, and 10 weeks by counting, as well as by determining the soma diameter. The dendritic field of three types (I, II, III) of RGCs between control and experimental eyes were also studied at 4,6,10 weeks after IOP elevation. At every time point, the number of cells in experimental eyes were significantly less than those of the control eyes. The average retinal ganglion cell death was 3--4% per week in the eyes with elevated IOP. The soma and dendritic field diameter of the RGCs in the experimental eyes were significantly larger in all cell types. However, types I and III cells expanded their dendritic fields more rapidly than type II cells. Furthermore, dendritic fields of surviving RGCs in experimental eyes occupied about the same extent of the retina as the controls. The increase in soma diameter and expansion of dendritic fields in the remaining RGCs in eyes with elevated IOP suggests the existence of plasticity in adult retina.

Scanning laser ophthalmoscopy of the optic nerve head in exfoliation glaucoma and ocular hypertension with exfoliation syndrome

AIMS

To study the relation between optic nerve head topography (Heidelberg retina tomograph, HRT) and disc area, visual field index mean defect (MD), and intraocular pressure (IOP), and to see whether change in HRT parameters is associated with change in MD in a prospective follow up.

METHODS

80 consecutive patients (69 patients with exfoliation glaucoma and 11 with ocular hypertension combined with exfoliation syndrome) were examined before IOP reducing intervention and prospectively followed every 6 months for 2 years.

RESULTS

At the entry point, multiple regression analysis showed significant linear association between MD and all HRT parameters, when controlling for disc area. Disc area showed significant association with cup area, cup/disc area ratio, rim area, cup volume, and mean RNFL thickness. Six months after intervention IOP had decreased significantly. Reversible changes in cup area, cup/disc area ratio, rim area, cup volume, rim volume, mean cup depth, and maximum cup depth were associated with decrease in IOP. During the follow up period from 6 month to 2 years, IOP did not change significantly, and MD was used as a measure of progression of glaucoma. During this period, only cup shape measure among HRT parameters showed significant association with subsequent change in MD.

CONCLUSION

Disc area should be taken into account when using HRT to compare patients. Any effect of change in IOP should be also taken into account when using HRT in follow up. Cup shape measure is a promising indicator of progression of glaucomatous damage.

Increased corneal thickness in patients with ocular hypertension

BACKGROUND

Central corneal thickness greater than 0.520 mm causes true intraocular pressure to be overestimated when the technique of applanation tonometry is used to measure intraocular pressure.

OBJECTIVE

To compare the corneal thickness measurements of patients enrolled in a study of ocular hypertension with those of age-matched control subjects with normal intraocular pressure.

METHODS

Central corneal pachymetry using an optical pachymeter was performed on each study subject (n = 55) at baseline and in an independent sample of control subjects. A 2 sample, 2-tailed T test was used to compare the 2 populations.

RESULTS

The patients with ocular hypertension had significantly higher mean corneal thickness measurements (mean +/- SD, 0.594 +/- 0.037 mm) than the control group (0.563 +/- 0.027 mm) (P<.001).

CONCLUSION

Corneal thickness may be a confounding factor in the measurement of intraocular pressure, and this may modify the risk for progression to glaucoma in patients with ocular hypertension.

Slope analysis of the optic disc in eyes with ocular hypertension and early normal tension glaucoma by confocal scanning laser ophthalmoscope

AIMS

To determine whether quantitative differences in sector based slope can differentiate between eyes with ocular hypertension with and without glaucomatous disc changes and eyes with normal tension glaucoma with glaucomatous disc changes.

METHODS

Seventy six eyes with ocular hypertension or early glaucomatous disc changes were consecutively categorised into three groups: 22 eyes with ocular hypertension and no glaucomatous disc changes (OHND); 35 with ocular hypertension and glaucomatous disc changes (OHD); and 19 with normal ocular tension and glaucomatous disc changes (NTD). Twenty eyes served as controls. The average total slope angle and sector based slope angle of the cup, total contour area, effective area, neuroretinal rim area, half depth area, cup to disc ratio, contour variation, mean contour depth, average depth, volume below, half depth volume, and contour tilt were evaluated with a confocal scanning laser ophthalmoscope.

RESULTS

The earliest changes in eyes with OHND or OHD started in the slope at the nasal inferior sector (p<0.05), followed by the superior and temporal superior sectors (p<0.05). The mean slopes in eyes with NTD and OHD were steeper than in controls (p<0.05). Statistically significant differences were found between controls and disease groups in the half depth area, mean contour depth, and half depth volume. The cup to disc ratios in eyes with OHD and NTD were greater than in eyes with OHND; the volume below was greater in eyes with NTD than in eyes with OHND and OHD.

CONCLUSIONS

The steep slope in the nasal inferior section is the first indicator of glaucomatous nerve defects in many eyes. The half depth parameters, half depth area, and half depth volume may be useful for distinguishing ocular hypertension with and without glaucomatous disc changes.

Association of ocular pressure and optic disc cup volume with red blood cell sodium-potassium ATPase inhibition

PURPOSE

To determine if there were significant differences between the number of red blood cell ouabain binding sites in normals and untreated ocular hypertensives plus one open-angle glaucoma patient.

METHODS

We measured the binding of (3)H ouabain to erythrocyte membranes of 23 normals, 25 ocular hypertensives and one open-angle glaucoma. We also measured the levels of plasma cortisol and digoxin in these subjects. Characteristics of cupping of the optic disc and thickness of the retinal nerve fiber layer, as well as area of optic disc pallor of these subjects were measured by stereophotogrammetry and by computerized image analysis from single and stereo photographs.

RESULTS

The number of (3)H ouabain binding sites was observed to be significantly less in the ocular hypertensives and one glaucoma compared to the normals (p = 0.0009). In multi-variate analyses, to determine what other factors affected this difference, there was a significant negative association with mean intraocular pressure (p = 0.003) (average of both eyes) and total cup volume (average of both eyes) (p = 0.005), diagnosis of ocular hypertension and glaucoma (p = 0.0005) and male gender (p = 0.019). There was a significant positive association with plasma cortisol levels (p = 0.048), and diastolic blood pressure (p = 0.037).

CONCLUSIONS

The number of (3)H ouabain binding sites in red blood cells decreases significantly with increasing ocular pressure and increasing cup volume indicating the possible presence of an increased systemic endogenous digoxin-like inhibitor and/or difference in the isozymes of Na(+), K(+)-ATPase which may be associated with increased levels of plasma cortisol in ocular hypertensives and glaucomas.

[Corneal thickness and intraocular pressure in cases with ocular hypertension and glaucoma]

OBJECTIVE

To investigate the relationship between central corneal thickness (CCT) and intraocular pressure (IOP) in patients with ocular hypertension (OH), normal tension glaucoma (NTG), primary open angle glaucoma (POAG) and normal subjects and the importance of CCT in the diagnosis of glaucoma.

METHODS

The CCT was measured in 79 cases with NTG, 61 POAG, 73 OH and 50 normal subjects with an ultrasonic pachymeter. One eye in one subject randomly selected was used for inter-group comparison. The maximum IOP measured by Goldmann applanation tonometer without ocular hypotensive therapy during the follow-up was corrected with CCT by using Ehlers' method.

RESULTS

The CCT of OH subjects (582 +/- 32) microm was significantly thicker than that of other groups (P < 0.001), while no differences were seen in CCT among normal, NTG and POAG groups, the thickness being (552 +/- 36) microm, (548 +/- 33) microm and (550 +/- 33) microm respectively. The corrected maximum pressure was significantly lower than that in the untreated ones in all the groups, and <or= 21 mm Hg in 100%, 97%, 55% and 50% of the eyes in the normal, NTG, OH and POAG subjects, respectively. In the normal subjects, the CCT was positively correlated with the IOP (r = 0.423, P = 0.004).

CONCLUSIONS

There is a large variation in CCT of normal subjects, which is significantly positively correlated with IOP. The CCT is significantly thicker in OH subjects, which should be considered as an important variable in follow-up. No significant differences in CCT are shown among NTG, POAG and normal groups. It is suggested that CCT has little influence on the diagnosis of NTG and POAG.

[Central corneal thickness in normal eyes, patients with ocular hypertension, normal-pressure and open-angle glaucomas--a clinical study]

BACKGROUND

The relation between Goldmann applanation tonometry and central corneal thickness (CCT) was investigated in several studies during the last thirty years. It was the aim of the present study to evaluate CCT in normals, patients with ocular hypertension, low-tension, and open-angle glaucomas.

PATIENTS AND METHODS

CCT was measured in 135 normal eyes, 137 with ocular hypertension, 65 with low-tension, and 94 with primary and secondary open-angle glaucomas using the AL-11000-pachymeter (Tomey). The results were compared using the unpaired t-test.

RESULTS

CCT was significantly higher in the patients with ocular hypertension (586 +/- 43 microns) than in the normal group (566 +/- 37 microns, p < 0.0001), in low-tension glaucomas (555 +/- 46 microns, p < 0.0001), and in open-angle glaucomas (558 +/- 31 microns, p < 0.0001). The latter three groups did not differ significantly. There was no significant correlation between CCT and age, the actually measured IOP, the highest IOP in the patient's history, or the spherical equivalent.

CONCLUSIONS

Only patients with ocular hypertension showed a significant difference in CCT compared with normals. Pachymetry thus should be conducted in those patients to avoid overestimation of the IOP by applanation tonometry. In most of the patients with low-tension and open-angle glaucomas however, CCT regarded without other parameters (e.g. corneal or scleral rigidity) plays a minor role in detection of elevated IOP according to the results of this study.

Occurrence of cholinergic nerve fibers in the human uveoscleral tissue

We have studied the cholinergic nerve fibers (CNF) of human uveoscleral tissue in normal and pathological conditions (intraocular pressure: (IOP) of various degrees ) and have performed a quantitative image analysis of CNF with the aim of studying an hypothetical association between IOP and the uveoscleral level of cholinergic neurotransmitter in nerve fiber of the enucleated human eyes. Eleven patients, previously enrolled in our medical protocols are affected by an increase of IOP of various degrees, were subjected to surgical enucleation of one eyeball for traumatic or neoplastic reasons and were the donors of samples of the uveoscleral tissue for CNF demonstration. The samples were also submitted to quantitative image analysis. An enzymatic activity, Acetylcholinesterase (AChe), is present in nerve fibers that innervate the human uveoscleral tissue. The AChe-positive nerve fibers represent about 7.2% of the observed area in normal conditions, while in patients with elevated IOP AChe activity is about 20.3% of the total observed area. The increase of AChe activity in our experiments, all performed under the same conditions, and therefore, with comparable results, may be related with the increase of IOP.

The combined effect of brain-derived neurotrophic factor and a free radical scavenger in experimental glaucoma

PURPOSE. Brain-derived neurotrophic factor (BDNF) had a limited effect on the survival of retinal ganglion cells (RGCs) in rats' eyes with elevated intraocular pressure (IOP). The combined treatment of BDNF and a nonspecific free radical scavenger N-tert-butyl-(2-sulfophenyal)-nitrone (S-PBN) was investigated on the RGCs in hypertensive eyes of rats.

METHODS

Adult Wistar rats were separated into five groups: BDNF (0.5 microg) + S-PBN; BDNF (1. 0 microg) + S-PBN; BDNF (1.0 microg); S-PBN; and phosphate-buffered saline. Right eyes served as normal controls (n = 10). RGCs were labeled with 5% Fluoro Gold; injected into the superior colliculus. Three days after intratectal injection, the episcleral veins of the left eyes were cauterized. Intravitreal injection of BDNF was performed on days 5, 13, 21, and 29 after IOP elevation. S-PBN was injected intraperitoneally (100 mg/kg body wt) every 12 hours starting 30 minutes after cauterization.

RESULTS

The survival of RGCs using BDNF treatment alone in moderately hypertensive eyes and systemic administration of S-PBN alone did not significantly rescue the RGCs. However, the combination of BDNF and S-PBN increased the survival of RGCs to 90.1%.

CONCLUSIONS

Trophic factors and antioxidants have synergistic effects on rescuing RGCs from death in eyes with elevated IOP. Further studies of different combined treatment therapies may provide avenues to save RGCs from death in eyes with elevated IOP.

Measurement of a novel optic disc topographic parameter, "spikiness", in glaucoma

BACKGROUND

Structural changes in the lamina cribrosa have been implicated in the pathogenesis of glaucomatous optic atrophy, but not observed. This paper presents a novel parameter of topographic variability within the optic disc, termed "spikiness", which may reflect glaucoma-related changes in the lamina.

METHODS

Four age-matched groups of normal patients (n=12, mean age 64.8 years) and patients with ocular hypertension (n=14, mean age 63.1), primary open-angle glaucoma (n=11, mean age 70) and low-tension glaucoma (n=15, mean age 66.3) were recruited. Images of normal and glaucomatous eyes from the Heidelberg Retina Tomograph were imported into ERDAS image processing software where the spikiness data (30 consecutive mean surface height values across the base of the optic cup in both the vertical and horizontal meridians) were extracted in a format that facilitated further statistical analysis.

RESULTS

Significant differences in topographic variability (spikiness) existed in the vertical (F=3.64, P=0.01) but not the horizontal meridian (F=1.25, P=0.3) through the optic disc. Spikiness was inversely related to Humphrey mean deviation (P<0.05), and cup-disc ratio (P<0.004) and was directly related to nerve fibre layer thickness (P<0.005). Of particular interest was the finding that the spikiness measure was the only optic disc parameter to significantly discriminate low tension glaucoma from primary open angle glaucoma.

CONCLUSION

A new measure of surface variability (topography) at the floor of the optic cup has been described. The new index of spikiness may represent a measurement of lamina cribrosa fragility which has been implicated, but not previously estimated, in glaucomatous eyes.

Retinal ganglion cells recognized by serum autoantibody against gamma-enolase found in glaucoma patients

PURPOSE

To study pathologic roles of the presence of serum autoantibodies against retinal ganglion cells in patients with glaucoma.

METHODS

Serum autoantibody reactions were detected by Western blot analysis using retinal soluble fractions in 79 patients with glaucoma (normal-tension glaucoma [NTG], 23 cases; primary open-angle glaucoma [POAG], 56 cases) and 60 age-matched healthy subjects. Clinical characteristics including visual acuity, visual field, intraocular pressure (IOP), and optic disc features were compared between the serum autoantibody-positive and -negative patients. The retinal autoantigen recognized by patients' sera was identified by a combination of in-gel digestion and Edman sequencing.

RESULTS

Western blot analysis revealed that serum autoantibody against retinal 50-kDa antigen was recognized in 20 out of 79 glaucoma patients (25.3%; 14 POAG and 6 NTG patients) and 60 age-matched control subjects (11.7%), respectively. Immunocytochemistry revealed that labeling of the ganglion cell layer (GCL) by IgG from glaucoma patients (POAG: 13/56, 23.2%; NTG: 6/23, 26%) existed at a significantly higher rate than that by IgG from control subjects (2/60, 3.3%; P < 0.05). In POAG, maximum IOP in the serum antibody positive-patients was significantly lower than that in the antibody-negative patients (P < 0.05). However, no statistical differences were observed in visual field loss, disc cupping, and other clinical factors between the antibody-positive and -negative groups in POAG and NTG. In-gel digestion of the 50-kDa band in two-dimensional polyacrylamide gels and Edman sequence analysis of the high-performance liquid chromatography-purified peptides identified the 50-kDa protein as gamma-enolase. Injection of the 50-kDa IgG from glaucoma patients or anti-gamma-enolase serum into the vitreous cavity of Lewis rats caused reduction of the b-wave of the electroretinogram and TdT-dUTP terminal nick-end labeling (TUNEL)-positive staining within the GCL.

CONCLUSIONS

In the current study, serum autoantibody against 50-kDa protein identified as gamma-enolase in 25% of glaucoma patients.

Repair in the rabbit outflow system

An in vivo study was conducted to study repair processes in the injured rabbit outflow system. A uniform injury was produced by raising intraocular pressure (IOP) manometrically to 70 mmHg for 1 h. The recovery process, which was followed clinically for 8 weeks and morphologically for 6 weeks, led to the re-establishment of normal meshwork architecture within this period. The morphological studies included light microscopy, autoradiography and electron microscopy. The initial lesion consisted of large deficits in the meshwork with breakdown of cell-to-cell connections, loss of extracellular materials and disruption of the vessels of the aqueous plexus. There was a significant lowering of IOP in the first week of recovery, which thereafter climbed back to normal. Also in the first week the meshwork became infiltrated with inflammatory cells which cleared by 4 weeks. There was some meshwork cell death by either necrosis or apoptosis. The majority of meshwork cells became activated within the first few days and remained activated for at least the first 2 weeks. Tritiated proline incorporation was maximal between 1 and 2 weeks. Tritiated thymidine labelling was seen throughout, but only after the inflammation subsided was it clear that meshwork cells in all regions of the meshwork were proliferating. Our study provided no evidence that normal meshwork cells have a basal proliferative turnover level. Our injury model involved complete repair of the outflow tissues and that required meshwork cells to become activated, mobilise, undertake synthetic activity and proliferate. This is the first example, other than argon laser trabeculoplasty, where meshwork cells in vivo have been induced to divide. Possible therapeutic implications for glaucoma are discussed.