Peripapillary choroidal circulation in glaucoma

Microstructure of Nonjuxtapapillary Microvasculature Dropout in Healthy Myopic Eyes

Purpose

The purpose of this study was to characterize the microstructure of the nonjuxtapapillary microvasculature dropout (MvD) in healthy myopic eyes.

Methods

This cross-sectional study included 50 eyes (25 eyes with a nonjuxtapapillary MvD and 25 age-matched eyes without any MvD) from a cohort of 126 nonglaucomatous healthy myopic eyes having parapapillary atrophy (PPA) γ-zone. The parapapillary deep-layer microvasculature was evaluated in en-face images obtained using swept-source optical coherence tomography (OCT) angiography (OCTA). A nonjuxtapapillary MvD was defined as an area with focal absence of vascular signals in the distal portion of PPA confined to the nonjuxtapapillary area. Enhanced depth-imaging OCT scanning was performed to assess the parapapillary microstructure.

Results

Nonjuxtapapillary MvD was found in 25 eyes (19.8%). The parapapillary microstructure at the nonjuxtapapillary MvD in 18 eyes was characterized by the misalignment of Bruch's membrane (BM)–retinal pigment epithelium (RPE) complex, which was identified by the absence of BM-RPE complex and the presence of the inner retina and sclera. In seven eyes with a nonjuxtapapillary MvD but without such misaligned BM-RPE complex, RPE atrophy was observed at the location of the nonjuxtapapillary MvD. Eyes with a nonjuxtapapillary MvD had a longer axial length (AXL; P = 0.013) and a wider γ-zone (P < 0.001) than age-matched control eyes without any MvD.

Conclusions

The microstructure at the nonjuxtapapillary MvD in healthy myopic eyes was characterized in approximately 70% of eyes by temporally misaligned BM-RPE complex. Although the clinical importance of the nonjuxtapapillary MvD remains to be determined, it should be differentiated from the parapapillary choroidal MvD observed in glaucoma.

Sectoral changes of the peripapillary choroidal thickness in patients with unilateral branch retinal vein occlusion

AIM

To investigate sectoral changes in the mean peripapillary choroidal thickness (PCT) in patients with unilateral branch retinal vein occlusion (BRVO).

METHODS

This retrospective, interventional study included 41 patients with acute, unilateral BRVO without macular edema. All patients completed at least a 6-month follow-up period. The PCT was measured at eight locations (temporal, superotemporal, superior, superonasal, nasal, inferonasal, inferior, and inferotemporal). In addition to calculating the average of all locations, the peripapillary choroidal area was divided into four sectors: superior (average of superotemporal PCT, superior PCT, and superonasal PCT), temporal, inferior (average of inferotemporal PCT, inferior PCT, and inferonasal PCT), and nasal.

RESULTS

In the BRVO-affected eyes, the mean PCT was 177.7±69.8 µm (range, 70.1-396.0 µm) at baseline and 127.8±54.8 µm (range, 56.4-312.1 µm) at 6mo (P<0.001). In the non-affected contralateral eyes, the mean PCT was 192.5±60.6 µm (range, 61.4-365.0 µm) at baseline and 165.9±61.1 µm (range, 56.8-326.8 µm) at 6mo (P<0.001). In sectoral analysis, the mean PCT in each sector was significantly reduced in over 6mo in the BRVO-affected eyes (all P<0.001). In the non-affected contralateral eyes, the mean PCT was not significantly changed in any sector over the 6-month follow-up period (superior sector, P=0.143; temporal sector, P=0.825; inferior sector, P=0.192; and nasal sector, P=0.599).

CONCLUSION

Sectoral analysis shows that the mean PCTs in all sectors are reduced significantly over 6mo in the BRVO-affected eyes, but not in the non-affected contralateral eyes.

Central Visual Field Damage and Parapapillary Choroidal Microvasculature Dropout in Primary Open-Angle Glaucoma

PURPOSE

To determine whether microvasculature dropout (MvD) in the parapapillary choroid is related to the presence of central visual field defects in primary open-angle glaucoma (POAG).

DESIGN

Cross-sectional observational study.

PARTICIPANTS

Thirty-two POAG patients with an initial parafoveal scotoma (IPFS) within a 10° radius in 1 hemifield and 42 POAG patients with an initial nasal step (INS) within the nasal periphery outside 10° of fixation in 1 hemifield.

METHODS

The peripapillary choroidal microvasculature was evaluated on en face images obtained using swept-source OCT angiography. Microvasculature dropout was defined as a focal sectoral capillary dropout with no visible microvascular network identified in the choroidal layer. Factors associated with IPFS, compared with INS, were assessed using logistic regression analyses.

MAIN OUTCOME MEASURES

Factors associated with IPFS rather than INS.

RESULTS

Microvasculature dropout was observed in 25 of 32 eyes (78.1%) in the IPFS group, but in only 1 of 42 eyes (2.4%) in the INS group (P < 0.001). In logistic regression analyses, only MvD was a significant factor influencing the presence of IPFS. Systemic risk factors such as cold extremities (P = 0.026), migraine (P = 0.044), lower mean arterial pressure (P = 0.037), and lower ocular perfusion pressure (P = 0.024) were associated significantly with the presence of MvD.

CONCLUSIONS

The presence of MvD in the parapapillary choroid was a strong predictor for IPFS.

Parapapillary Choroidal Microvasculature Dropout in Glaucoma: A Comparison between Optical Coherence Tomography Angiography and Indocyanine Green Angiography

PURPOSE

To investigate whether the parapapillary choroidal microvasculature dropout (MvD) determined by optical coherence tomography angiography (OCTA) in glaucomatous eyes indicates a true perfusion defect and whether the MvD accurately represents the area of nonperfusion.

DESIGN

Observational case series.

PARTICIPANTS

Thirty primary open-angle glaucoma (POAG) patients with choroidal MvD as determined by OCTA and 13 POAG patients without this dropout.

METHODS

Peripapillary circulation was evaluated using both OCTA and indocyanine green angiography (ICGA). For OCTA, the choroidal microvasculature was evaluated using 4.5×4.5-mm choroid-disc vessel density maps of OCTA images of the optic nerve head. An MvD was identified in OCTA by the presence of a capillary dropout. A filling defect observed in ICGA was defined as a perfusion defect (_ICGPD).

MAIN OUTCOME MEASURES

The topographic correlations between MvD and _ICGPD determined based on their circumferential extent, location, and area.

RESULTS

The _ICGPD was observed as a sectoral filling defect in the 30 POAG patients exhibiting MvD and appeared identical to the MvD in terms of the shape and location. The circumferential extent, location, and area of _ICGPD did not differ from those of the MvD (all P > 0.05). The _ICGPD was not found in any of the eyes not having the MvD.

CONCLUSIONS

A localized MvD observed in the parapapillary choroid using OCTA coincided with the _ICGPD detected by ICGA. These findings indicate that OCTA accurately images impaired parapapillary choroidal circulation.

The blood supply of the optic nerve head and the evaluation of it - myth and reality

Evidence has gradually emerged that there is vascular insufficiency in the optic nerve head (ONH) in both anterior ischemic optic neuropathy (AION) and glaucomatous optic neuropathy (GON); thus both represent ischemic disorders of the ONH. Together these diseases constitute a major cause of blindness or seriously impaired vision in man. Consequently there has recently been great interest in the ONH circulation in health and disease and in how to evaluate it. Many studies of the subject have been published, with conflicting interpretations and claims. The basis of the inconsistent information seems to be confusion on some fundamental issues concerning the ONH circulation itself. The objective of this paper is to differentiate myths and misconceptions from reality about the ONH blood supply; to elucidate the reasons for disagreement on the blood supply of the ONH; and to evaluate the reliability and validity of various methods currently used to measure ONH blood flow.

Optic nerve head circulation after intraocular pressure reduction achieved by trabeculectomy

OBJECTIVE

To study the effects of trabeculectomy and needling revision of poorly functioning blebs on the optic nerve head (ONH) circulation in patients with primary open-angle glaucoma (POAG).

DESIGN

Prospective, nonrandomized, self-controlled trial.

PARTICIPANTS

Nineteen POAG patients (age range, 52 +/- 12 years; mean +/- standard deviation) undergoing trabeculectomy and six POAG patients (age range, 62 +/- 14 years) undergoing needling revision of the bleb.

METHODS

Using the laser speckle method, the normalized blur (NB) value, a quantitative index of blood velocity, was determined every 0.125 seconds and averaged more than three cardiac pulses in the optic nerve head (NB(ONH)).

MAIN OUTCOME MEASURES

The NB(ONH) and intraocular pressure (IOP) in both eyes, and blood pressure (BP) and pulse rate (PR) were measured before and 2 days and 1, 4, and 8 weeks after trabeculectomy, and also before and 10 and 40 min after needling procedures.

RESULTS

Intraocular pressure in the operated eye was significantly decreased after trabeculectomy or needling procedures, and the ocular perfusion pressure was significantly increased by a maximum of 38%. The IOP in the unoperated eye, BP, and PR did not significantly change. The NB(ONH) did not significantly change in either the operated or unoperated eye.

CONCLUSIONS

Trabeculectomy and needling procedures induced little change in the ONH circulation.

Diagnosis and pathogenesis of glaucomatous optic neuropathy: morphological aspects

Glaucomatous optic neuropathy is classified by morphologic changes in the intrapapillary and parapapillary region of the optic nerve head and the retinal nerve fibre layer. These changes can be evaluated using descriptive optic nerve head variables which are the size and shape of the optic disc; size, shape and pallor of the neuroretinal rim; size of the optic cup in relation to the area of the disc; configuration and depth of the optic cup; cup-to-disc diameter ratio and cup-to-disc area ratio; position of the exit of the central retinal vessel trunk on the lamina cribrosa surface; presence and location of splinter-shaped haemorrhages; occurrence, size, configuration and location of parapapillary chorioretinal atrophy; diffuse and/or focal decrease of the diameter of the retinal arterioles; and visibility of the retinal nerve fibre layer. Assessment of these variables is useful for the early detection of glaucomatous optic nerve damage, to follow-up patients with glaucoma, to differentiate various types of the chronic open-angle glaucomas, and to get hints for the pathogenesis of glaucomatous optic nerve fibre loss.

Optic disk morphology in experimental central retinal artery occlusion in rhesus monkeys

PURPOSE

To evaluate longitudinally the optic disk morphology of nonglaucomatous optic nerve damage secondary to retinal nerve fiber damage, using experimental central retinal artery occlusion in rhesus monkey eyes as a model.

METHODS

This prospective study included 24 eyes of 16 monkeys. In eight eyes of eight animals, central retinal artery occlusion was produced by clamping the central retinal artery in the retrobulbar space. Occlusion was verified by fluorescein fundus angiography. The same eyes at baseline as well as the eight contralateral healthy eyes and eight monkey eyes with experimental high-pressure glaucoma served as control groups. Serially taken optic disk photographs were morphometrically evaluated.

RESULTS

The area and shape of the neuroretinal rim and alpha zone and beta zone of parapapillary chorioretinal atrophy of eyes after central retinal artery occlusion did not vary significantly (P > .30) from the same eyes before central retinal artery occlusion nor from the normal contralateral eyes. In the glaucomatous eyes, the neuroretinal rim was significantly (P < .001) smaller and parapapillary atrophy significantly (P = .01) larger than in the eyes after central retinal artery occlusion.

CONCLUSIONS

Experimental central retinal artery occlusion, in contrast to glaucoma, does not markedly change the size and shape of parapapillary atrophy and neuroretinal rim; this confirms previous clinical studies. Thus, assessment of parapapillary atrophy and neuroretinal rim may be helpful to differentiate between glaucomatous optic neuropathy and nonglaucomatous optic neuropathy secondary to retinal nerve fiber damage. Parapapillary atrophy is independent of decreased retinal blood perfusion and development of nonglaucomatous optic nerve atrophy following experimental central retinal artery occlusion.

Effect of acute intraocular pressure changes on short posterior ciliary artery haemodynamics

BACKGROUND/AIMS

Vascular insufficiency due to abnormal autoregulation has been proposed as a major factor in the development of glaucoma. The anterior optic nerve is primarily perfused by the short posterior ciliary arteries. The autoregulatory capacity of these vessels in response to acutely elevated intraocular pressure (IOP) was examined in normal human subjects.

METHODS

Colour Doppler imaging was performed on the short posterior ciliary arteries of 10 normal subjects at baseline and during four incremental IOP elevations. Using a scleral suction cup placed temporally, IOP was elevated to approximately 25, 30, 40, and 50 mm Hg. Additional measurements were performed immediately after pressure release. Systolic and diastolic flow velocities were measured and Pourcelot's resistivity index was calculated.

RESULTS

Systolic and diastolic flow velocities decreased linearly with each incremental increase in IOP (p < 0.001). Pourcelot's resistivity index increased linearly with each incremental increase in IOP (p < 0.001). Changes in end diastolic velocity, peak systolic velocity, and Pourcelot's resistivity index were linearly related to changes in IOP.

CONCLUSION

The normal healthy eye is not able to autoregulate to maintain PCA blood flow velocities in response to acute large elevations in IOP.

Trabeculectomy is associated with retrobulbar hemodynamic changes. A color Doppler analysis

PURPOSE

To determine whether color Doppler hemodynamic changes occur in the retrobulbar circulation after trabeculectomy.

METHODS

The authors prospectively enrolled 20 patients undergoing trabeculectomy and performed color Doppler imaging of both eyes before surgery and then at approximately 2-, 5-, and 14-week intervals after surgery. The systolic maximum velocity, mean velocity, end-diastolic velocity, and vascular resistance (resistance index) of the central retinal artery, nasal and temporal short posterior ciliary arteries, and ophthalmic arteries were determined. Statistical comparison of the preoperative and postoperative measures were performed on both the operative and nonoperative eye using the paired Student's t test.

RESULTS

A statistically significant increase was observed in the mean and end-diastolic velocity and a significant decrease in the vascular resistance of the central retinal artery and both short posterior ciliary arteries at nearly all postoperative intervals (25 of 27 preoperative and postoperative comparisons; P < 0.05) The ophthalmic artery, while showing an increased velocity at all intervals, only attained a statistically significant increase in one of three postoperative intervals for mean velocity and two of three intervals for end-diastolic velocity (P < 0.05). There were no notable changes in resistance. The nonoperative eye did not show a statistically significant change in velocity or in resistance in the central retinal artery or either nasal or temporal short posterior ciliary artery at any interval (0 of 27 preoperative and postoperative comparisons for mean velocity, end-diastolic velocity, and resistance index.)

CONCLUSION

Sustained increases in mean velocity and end-diastolic velocity and decreases in resistance index were observed in the central retinal artery and the short posterior arteries with clinically attainable reductions in intraocular pressure after trabeculectomy in patients with chronic glaucoma. These findings are consistent with, but not diagnostic of, increased blood flow through these vessels.

Uveal damage in secondary glaucoma. A morphometric study

In a morphometric study, we investigated histopathologic changes in the ciliary body and retinal pigment epithelium in eyes with secondary glaucoma. Eyes with malignant melanoma served as controls. The mean thicknesses of the ciliary muscle and inner connective-tissue layer of the pars plicata were significantly lower (P less than 0.001) in glaucomatous than in melanomatous eyes, as was the mean width of the stromata of ciliary processes (P less than 0.001). With increasing age, the ciliary muscle in melanomatous eyes became significantly thinner (P less than 0.001). The width of the stroma at the base of the ciliary process was significantly correlated with the thickness of the inner connective-tissue layer of the pars plicata in both groups of eyes (P less than 0.001). The mean number of ciliary processes was significantly lower in glaucomatous than in melanomatous eyes (P less than 0.001), as was the mean height of pigment epithelial cells in the midperipheral retina P less than 0.05). The present study revealed quantitative glaucomatous tissue changes in the ciliary body and retinal pigment epithelium.

Fluorescein angiography of the choroid in health and disease

Fluorescein angiography of the normal fundus reveals the segmental nature of the choroidal vascular bed. Despite the presence of anatomically demonstrable anastomoses, a segmental distribution is present in vivo up to the choriocapillaris level. Choroidal vascular diseases manifest by localized of diffuse delayed or incomplete filling of the choroid and by the involvement of the overlying retinal pigment epithelium. In the acute phase of choroidal arterial occlusive disease, ophthalmoscopy reveals localized or diffuse edema. Fluorescein angiography of such cases initially shows a delayed perfusion of the involved area followed later on by fluorescein leakage. This late diffusion of the dye is probably related to alterations of the retinal pigment epithelial barrier. The extent of the lesion after resolution of the edema mainly depends on the site and the extent of the occlusion, on the development of collaterals and possibly on the involvement of the choroidal venous circulation. Ophthalmoscopy and fluorescein angiography will reveal localized or diffuse pigmentary changes, sometimes of quite characteristic aspect. This may be associated with local destruction of the choriocapillaris, although normalization of choroidal blood flow may also be observed. Chronic choroidal vascular insufficiency is a possible cause for choroidal sclerosis. Chronic choroidal ischemia is also a possible explanation for peripheral pigmentary changes seen in the elderly.

The effects of visual field changes and ocular hypertension on the visual evoked potential

The effects of visual field changes and ocular hypertension on visual evoked potentials were investigated by photopic ERG and by luminance and pattern-reversal EPs on 116 glaucomatous and on 7 normal eyes. The problem was approached by way of four investigations: Firstly, which nerve structures are affected by glaucoma and how do visual field defects caused by glaucoma influence the EP? The results show a functional diminution of all intraocular nerve structures in which the prelaminary part of the optic nerve is most affected. The EPs, especially the pattern-reversal EPs, are markedly diminished if the visual field defects extend inside the 10 degree boundary. Differences in the visual field defects of both eyes and the course of the sickness can be well observed by the EPs. Secondly, which preoperative prognosis for visual acuity produced by the EP can be given to patients who have a dense cataract in addition to glaucoma? A postoperative improvement of the visual acuity can be expected if the L-EPs are within the standard deviation. If the EP is distinctly diminished and does not increase with increasing stimulus intensity, then there is no hope for an improvement of the visual acuity after the operation. Thirdly, does a decrease of intraocular pressure in chronic and acute glaucoma influence the EP? In acute glaucoma with pressure levels of 50 mmHg or more, and sometimes in chronic glaucoma with pressure levels of about 30 mmHg, an increase of the amplitude of the EP and an improvement of the visual field could be noticed after pressure regulation. Fourthly, what is the behaviour of the EP in normal and glaucomatous eyes at experimentally elevated intraocular pressure? The amplitudes of the ERG components show a gradual decrease in normal as well as in glaucomatous eyes when intraocular pressure is increased and are maintained when intraocular pressure reaches systolic ophthalmic blood pressure. On the other hand, the EPs show a strong decrease in amplitude when intraocular pressure exceeds the mean ophthalmic blood pressure, particularly in the case of glaucomatous eyes.

[The electroretinogram and the visual evoked potential in normal and glaucomatous eyes (author's transl)]

The functional changes of the intraocular nerve structures caused by glaucoma were examined electro-ophthalmologically. The OPs, the photopic and scotopic ERG to examine the receptor and bipolar layers, as well as the EPs, elicited by luminance and pattern-reversal stimuli, for evaluation of the signal conduction in the optic nerve, were recorded. The problem was approached by way of three investigations: first was the question of which nerve structures are affected by glaucoma and exactly how the loss of visual field due to glaucoma can be determined. For this reason, 55 glaucomatous eyes with regulated intraocular pressure and different visual field losses were examined. The results show a functional diminution of all intraocular nerve structures in which the prelaminary part of the optic nerve is most affected. Differences in the visual field loss of both eyes can be well determined by the EPs. Second, the electro-ophthalmologic behavior in seven normal and eight pressure-regulated glaucomatous eyes was studied by gradually elevated intraocular pressure in order to obtain better insight into the functional pathology of glaucoma. The elevation of intraocular pressure was performed with a Müller spring dynamometer in five steps, depending on the ophthalmic blood pressure. The pressure behavior of the ERG components and the EPs is different. The amplitudes of the ERG components show a gradual decrease in normal as well as in glaucomatous eyes when intraocular pressure is increased, and are maintained when intraocular pressure reaches ophthalmic blood pressure. On the other hand, the EPs show a strong decrease in amplitude when intraocular pressure exceeds the mean ophthalmic blood pressure, particularly in the case of glaucomatous eyes. This behavior can be explained by a high pressure sensitivity of the preliminary part of the optic nerve, even greater in glaucomatous eyes. Third, the influence of pressure decrease on the electrical response was examined in glaucomatous eyes with chronic and acute pressure increase before and after pressure regulation. A mean pressure decrease of 37-13.6 mm Hg in ten eyes with chronic pressure increase led to no change in electrical responses other than a phase shift on the pattern-reversal EPs. In five cases with acute pressure increase, an amplitude increase on the luminance EPs was noticed after pressure regulation, with unchanged systemic blood pressure and almost unchanged ERG components. However, in one case an amplitude decrease on luminance EPs and ERG components was found with simultaneous blood pressure decrease. The increase of the amplitudes of the luminance EPs and the phase shifts of the pattern-reversal EPs can be explained as the functional improvement of the prelaminary part of the optic nerve caused by pressure decrease due to improved blood circulation in the prelaminary part of the optic nerve...