Microvessels of the human optic nerve head: ultrastructural and radioreceptorial changes in eyes with increased IOP

Effect of treatment with carteolol and latanoprost in newly diagnosed primary open-angle glaucoma on peripapillary vessel density

BACKGROUND AND AIM

In a previous follow-up of glaucoma patients taking carteolol or latanoprost, we found a greater progression of visual field changes with the prostaglandin than the betablocker. In the present study we compared the impact of carteolol and latanoprost on peripapillary vessel density in newly diagnosed primary open-angle glaucoma (POAG) patients.

METHODS

The study consisted of two groups of POAG patients. There were 46 patient eyes treated with carteolol (Carteol LP 2%) in the first group and 52 eyes treated with latanoprost (Xalatan 0.005%) in the second. Intraocular pressure (IOP), vessel density (VD) and visual field were assessed in all patients. VD was measured peripapillary by optical coherence tomography angiography (OCTA) with the Avanti RTVue XR in eight segments: Inferior Temporal - IT (1); Temporal Inferior -TI (2); Temporal Superior - TS (3); Superior Temporal - ST (4); Superior Nasal - SN (5); Nasal Superior - NS (6); Nasal Inferior - NI (7) and Inferior Nasal - IN (8). The measurements were compared before and after three months of treatment. The visual field was examined with a fast threshold glaucoma program using a Medmont M 700 instrument from Medmont International Pty Ltd. and only when a diagnosis of POAG was done. The overall defect (OD) was assessed.

RESULTS

Before treatment, there was no difference between groups in either OD or VD. After treatment, there was a decrease in IOP in both groups. In the carteolol-treated group, the mean decrease was 5.8 mmHg and in the latanoprost-treated eyes, the mean decrease was 7 mmHg. The difference was not statistically significant (P=0.133). After treatment with carteolol, there was a statistically significant increase in VD in segments 4, 5 and 6. After latanoprost treatment, VD was statistically significantly improved only in segment 5. A greater increase in VD values was found in eyes treated with carteolol than in eyes treated with latanoprost.

CONCLUSION

Carteolol had a better effect on vessel density than latanoprost.

Comparison of the Effect on Vessel Density and RNFL between Carteolol and Latanoprost

The aim of the study was to compare the treatment of hypertensive glaucoma (HTG) in the early stages with carteolol and latanoprost by assessing the change in vessel density (VD) and retinal nerve fibre layer (RNFL). Methods: The first group with diagnosed HTG consisted of 46 eyes treated with carteolol; the second group consisted of 52 eyes treated with latanoprost. The following examinations were evaluated in all patients: intraocular pressure (IOP), retinal nerve fibre layer (RNFL), vessel density (VD) and visual field examination (glaucoma fast threshold test). The results were compared before treatment and 3 months after treatment. Results: There was no difference in the overall visual field defect (OD) between groups before treatment. After treatment, there was a decrease in IOP in both groups (carteolol-treated group had a mean decrease of 5.8 mmHg and latanoprost-treated eyes had a mean decrease of 7 mmHg). This difference was not statistically significant (p = 0.133). No similar difference was observed for RNFL (p = 0.161). In contrast, the change in the VD parameter was statistically significant between groups (p < 0.05), with a greater difference observed in the carteolol-treated group of eyes. Carteolol had a better effect on the VD.

OCT angiography, RNFL and the visual field at different values of intraocular pressure

The aim of the present study was to investigate the relationship between intraocular pressure (IOP), vessel density (VD), retinal nerve fiber layer (RNFL) parameters and overall defect (OD) of the visual field in eyes where antiglaucoma treatment had not yet been initiated. A total of 61 subjects (122 eyes) who had an IOP of >20 mmHg on several occasions, in at least one eye, in routine outpatient care were included. These were subjects who had never been treated for hypertension glaucoma. The cohort was divided into four subgroups. In the first group, there were 18 eyes with an IOP value of <20 mmHg. In the second group, there were 39 eyes with IOP values of 20-22 mmHg. The third group consisted of 32 eyes with IOP values of 22-24 mmHg and the final group consisted of 33 eyes with IOP values of >24 mmHg. The IOP results were compared with VD, RNFL and OD using Pearson's correlation coefficient to assess the relationship between the selected parameters. RNFL and OD were moderately correlated only in the group of eyes with an IOP value >24 (r=0.48); in the other groups the correlation was very weak. However, changes in visual field were already observed in eyes with IOP 20-22 mmHg (r=-0.27). There was a moderate correlation in eyes with an IOP value >24 mmHg (r=-0.53). The most significant result observed was the relationship between VD and RNFL. In eyes with an IOP value ≤20, a moderate to strong correlation between these parameters was observed. This relationship increased with increasing IOP values up to a very strong correlation in the group with an IOP value >24 mmHg. A moderate to strong dependence between VD and RNFL in eyes with an IOP value ≤20 mmHg was observed, and this dependence was very strongly correlated in the eyes with an IOP value >24 mmHg.

Lamina cribrosa vessel and collagen beam networks are distinct

Our goal was to analyze the spatial interrelation between vascular and collagen networks in the lamina cribrosa (LC). Specifically, we quantified the percentages of collagen beams with/without vessels and of vessels inside/outside of collagen beams. To do this, the vasculature of six normal monkey eyes was labeled by perfusion post-mortem. After enucleation, coronal cryosections through the LC were imaged using fluorescence and polarized light microscopy to visualize the blood vessels and collagen beams, respectively. The images were registered to form 3D volumes. Beams and vessels were segmented, and their spatial interrelationship was quantified in 3D. We found that 22% of the beams contained a vessel (range 14%-32%), and 21% of vessels were outside beams (13%-36%). Stated differently, 78% of beams did not contain a vessel (68%-86%), and 79% of vessels were inside a beam (64%-87%). Individual monkeys differed significantly in the fraction of vessels outside beams (p < 0.01 by linear mixed effect analysis), but not in the fraction of beams with vessels (p > 0.05). There were no significant differences between contralateral eyes in the percent of beams with vessels and of vessels outside beams (p > 0.05). Our results show that the vascular and collagenous networks of the LC in monkey are clearly distinct, and the historical notions that each LC beam contains a vessel and all vessels are within beams are inaccurate. We postulate that vessels outside beams may be relatively more vulnerable to mechanical compression by elevated IOP than are vessels shielded inside of beams.

Association between Genetic Polymorphisms of the Beta Adrenergic Receptor and Diurnal Intraocular Pressure in Chinese Volunteers and Glaucoma Patients

PURPOSE

To evaluate the relationship between genetic polymorphisms of the beta adrenergic receptor (ADR) and diurnal intraocular pressure (IOP) in Chinese healthy volunteers, normal tension glaucoma (NTG) patients, and primary open-angle glaucoma (POAG) patients.

METHODS

Fifty healthy volunteers (control group), 55 untreated NTG patients, and 55 untreated POAG patients were recruited. IOP of both eyes was measured at 3-hour intervals from 0600 to 2400 hours. For control group, IOP data from the eye with better mean deviation (MD) of visual field was used for statistical analysis. For glaucoma patients, IOP data from the eye with a greater visual field defect was used for statistical analysis. Genetic polymorphisms of ADR were determined by direct DNA sequencing. The relationship between IOP and genetic polymorphisms was statistically analyzed.

RESULTS

R16G (A/G), L84L (G/A), and R175R (C/A) in β2-ADR showed significantly different allele in the three groups (p = 0.005, p = 0.045, and p = 0.045, respectively). For the POAG group, C/C of R389G (C/G) in β1-ADR had a significantly lower diurnal mean IOP (p < 0.001), peak IOP (p = 0.010), trough IOP (p < 0.001), and larger IOP range (p = 0.047) than G carriers; C/C of R389G (C/G) in β1-ADR and G carriers had parallel diurnal IOP curves but significantly different diurnal IOP levels (p = 0.001); C/C of Q27E (C/G) in β2-ADR had a significantly higher diurnal mean IOP (p = 0.045) than G carriers; G/G of L84L (G/A) in β2-ADR had a significantly higher diurnal mean IOP (p = 0.044) than A carriers; C/C of R175R (C/A) in β2-ADR had a significantly higher diurnal mean IOP (p = 0.044) than A carriers; T/T of W64R (T/C) in β3-ADR had a significantly smaller IOP range (p = 0.001) than C carriers.

CONCLUSION

Certain polymorphisms of β2-ADR showed significantly different genotype frequencies in healthy volunteers untreated NTG patients, and POAG patients. Polymorphisms of the β-ADR gene may alter the untreated IOP level of POAG patients.

Morphological and morphometric changes in rat optic nerve microvessels in a glaucoma experimental model

AIM

To study the morphological and morphometric changes produced in the capillaries of the optic nerve (ON) head and initial portion after the experimental increase in intraocular pressure (IOP).

MATERIAL AND METHODS

Wistar rats underwent cauterization of three episcleral veins, which produced an immediate increase in the IOP, and was maintained for 3 months. Sagittal sections of the eyeball were studied with immunohistochemical techniques, using a primary antibody to GLUT-1. The GLUT-1 positive capillaries were counted, and measurements were made of the area, perimeter and mean diameter.

RESULTS

Microscopic examination of sections of the ON of control rats revealed a lower density and larger caliber of capillaries in the prelaminar region as compared with the other regions of the ON (P<.05). Comparison between the control and the experimental groups showed a reduction in capillary density (except in the prelaminar region) and a smaller size in all the areas of the ON studied, but less evident in the initial portion (P<.05).

CONCLUSIONS

The increase in IOP was associated with significant qualitative and quantitative changes in the capillaries of the laminar and poslaminar regions of the ON head. These changes appear to return towards parameters compatible with normality in the initial portion of the ON, an area where the vascular collapse was less evident. These findings might explain the significant reduction in ocular blood flow seen in patients with primary open-angle glaucoma.