Variability of Heidelberg Retina Tomograph parameters during exercise

Purpose: The purpose of this study was to determine whether exercise affects the stereometric parameters representing optic nerve head (ONH) topography. Methods: ONH topography, intraocular pressure (IOP) and blood pressure of 30 healthy volunteers were monitored before, during and after dynamic exercise raising systolic blood pressure by a minimum of 30 mmHg. Change in the stereometric ONH parameters was calculated. Results: IOP decreased and blood pressure increased during exercise, resulting in an increase in mean ocular perfusion pressure. Exercise was associated with an increase in variance in 17 of the 18 stereometric ONH parameters. The increase in variance was statistically significant in eight parameters, including rim area, cup/disc area ratio and cup shape measure. There was no statistically significant change in image quality. The absolute change from baseline in rim area, cup area, cup/disc area ratio, rim/disc area ratio and rim volume showed a statistically significant (p < 0.05) correlation with change in mean ocular perfusion pressure. Conclusions: Exercise increases variability in stereometric ONH parameters. To avoid increased variance in the stereometric parameters, ONH imaging should be performed after allowing sufficient time to rest.     

Spectrometric measurements in the anterior eye vasculature of the albino rabbit--a study with the EMPHO I

Intracapillary haemoglobin oxygenation (oxygen saturation) and haemoglobin concentration (corresponding with blood volume) were measured in different regions of the albino rabbit anterior eye segment using the Erlangen micro-lightguide spectrophotometer (EMPHO I). The tip of the microlightguide (active diameter 210 microns, cover diameter 0.5 mm) was placed in the vitreous by a goniometric mounting and controlled by a micromanipulator. After stepwise elevation of intraocular pressure (IOP) the haemoglobin oxygenation decreased slightly in the iris at an IOP-level of 60 mmHg, whereas in the three regions of the ciliary processes and in the peripheral choroid haemoglobin oxygenation did not decrease until values of 80 mmHg were applied. In contrast, haemoglobin concentration decreases when the IOP increases in all regions except in the pars plana where the haemoglobin concentration increased at 40 and 60 mmHg. The most pronounced reactive hyperaemia was found in the major ciliary processes. Quite passive changes of haemoglobin concentration were seen in the peripheral choroid. Effective regulatory mechanisms must exist which result in IOP-independent (20-60 mmHg) haemoglobin oxygenation, whereas pronounced changes in intracapillary haemoglobin concentration were observed. The decay of both parameters at IOP 80 mmHg is indicative of an exhaustion of their regulatory capacity. Epinephrine topically applied onto the conjunctival sac or injected into the common carotid artery led to a short-term decrease of haemoglobin concentration and, later, a hyperaemic response. A short-term haemoglobin deoxygenation was found especially in the major ciliary processes.     

恒河猴慢性高眼压模型视乳头和视神经纤维损伤模式

目的观察恒河猴慢性高眼压模型与开角型青光眼患者的视乳头和视神经纤维损伤模式是否一致。方法实验研究。采用眼科多波长激光仪光凝恒河猴（12眼）的小梁网以破坏小梁网功能使眼压升高，建立恒河猴慢性高眼压模型。术前和术后每周行眼压、眼底照相、视乳头参数和视神经纤维层厚度检测。结果建模的12眼术前眼压为（16．08±2．02）mmHg，中央角膜厚度为（489．17±17．82）μm，眼轴为（20．32±0．84）mm。12只用于诱导建模的恒河猴眼，经3～4次激光光凝，11眼被成功诱导。27周平均眼压为（30．32±14．59）mmHg，眼压波动幅度为（8．19±7．45）mmHg。光学相关断层扫描成像显示整个盘沿面积从（1．67±0．44）mm2减小到（0．43±0．34）mm2。平均视神经纤维从（97．92±6．79）μm减少到（64．46±17．44）μm。结论恒河猴慢性高眼压性模型模拟了人类高眼压／开角型青光眼发病机制和过程，在视杯对高眼压的反应、视杯可逆性缩小、视神经纤维损伤现象等方面一致，是开展高眼压性视乳头和视神经纤维层损伤研究理想的动物模型。     

恒河猴慢性高眼压模型视乳头和视神经纤维损伤模式

目的 观察恒河猴慢性高眼压模型与开角型青光眼患者的视乳头和视神经纤维损伤模式是否一致。方法 实验研究。采用眼科多波长激光仪光凝恒河猴（12眼）的小梁网以破坏小梁网功能使眼压升高,建立恒河猴慢性高眼压模型。术前和术后每周行眼压、眼底照相、视乳头参数和视神经纤维层厚度检测。结果 建模的12眼术前眼压为（16.08±2.02）mmHg,中央角膜厚度为（489.17±17.82）μm,眼轴为（20.32±0.84）mm。12只用于诱导建模的恒河猴眼,经3～4次激光光凝,11眼被成功诱导。27周平均眼压为（30.32±14.59）mmHg,眼压波动幅度为（8.19±7.45）mmHg。光学相关断层扫描成像显示整个盘沿面积从（1.67±0.44）mm2减小到（0.43±0.34）mm2。平均视神经纤维从（97.92±6.79）μm减少到（64.46±17.44）μm。结论 恒河猴慢性高眼压性模型模拟了人类高眼压/开角型青光眼发病机制和过程,在视杯对高眼压的反应、视杯可逆性缩小、视神经纤维损伤现象等方面一致,是开展高眼压性视乳头和视神经纤维层损伤研究理想的动物模型。     

Effects of scleral buckling and encircling procedures on human optic nerve head and retinochoroidal circulation

AIMS: To study the effects of segmental scleral buckling and encircling procedures on tissue circulation in the human optic nerve head (ONH) and choroid and retina. METHODS: Using the laser speckle method, the normalised blur (NB) value, a quantitative index of tissue blood velocity, was measured every 0.125 seconds and averaged over three pulses in the optic nerve head (NB(ONH)) and choroid and retina (NB(ch-ret)) in 10 patients with unilateral rhegmatogenous retinal detachment (mean age 52 (SD 17)). NB(ONH), NB(ch-ret), and intraocular pressure (IOP) in both eyes, and blood pressure (BP) were measured before, and 1, 4, and 12 weeks after the scleral buckling and encircling procedure. RESULTS: NB(ch-ret) on the buckled side was significantly reduced after surgery and smaller than that in the unoperated contralateral eye throughout the study period (ANOVA, p<0.0001). NB(ch-ret) on the unbuckled side, in the foveal area, NB(ONH), IOP, and BP showed no significant change. CONCLUSIONS: It was indicated that the segmental scleral buckling procedure with encircling elements decreased tissue blood velocity in the choroid and retina on the buckled side but caused no significant change on tissue circulation in other areas of the fundus or ONH.     

Effects of nilvadipine, a calcium antagonist, on rabbit ocular circulation and optic nerve head circulation in NTG subjects

PURPOSE: To study the effects of nilvadipine, a Ca2+ antagonist, on tissue circulation in the optic nerve head (ONH), choroid, and retina in rabbits and on the ONH circulation in normal tension glaucoma (NTG) patients. METHODS: Nilvadipine (3.2 microg/kg) or vehicle solution was injected intravenously into urethane-anesthetized rabbits, and the normalized blur value (NB), a quantitative index of in vivo tissue blood velocity, was measured in the choroid and in an area of the ONH and retina free of visible surface vessels before and for 90 minutes after injection, using the laser speckle method. The effects of nilvadipine on the ONH circulation was also studied using the H2 gas clearance method in separate groups of rabbits. Oral nilvadipine (4 mg/d) or placebo was administered to NTG patients in a double-masked manner, and NB in an area of the ONH rim free of visible surface vessels was measured by the same method before and 2, 4, 8, and 12 weeks after administration. RESULTS: The NB obtained from the ONH, choroid, or retina during the experimental period was increased by approximately 10% to 25% in the nilvadipine group compared with the NB in the control group (P < 0.0001, ANOVA), although systemic condition parameters and intraocular pressure (IOP) showed no significant intergroup difference except for a transient decrease in blood pressure in the nilvadipine groups. Blood flow rate in the ONH determined by the H2 gas clearance method also showed an approximately 25% increase in the nilvadipine group. The NB in the ONH of the oral nilvadipine-treated patients was significantly increased, by approximately 20% compared with the placebo-treated patients throughout the follow-up period. No significant intergroup difference was seen in blood pressure, pulse rate, or IOP. CONCLUSIONS: Nilvadipine increased blood velocity and, probably, blood flow in the ONH, choroid, and retina of rabbits. It also increased blood velocity in the ONH of NTG patients.     

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.     

Morphological changes in the visual pathway induced by experimental glaucoma in Japanese monkeys

Glaucoma, an optic neuropathy, is the leading cause of world blindness. In this condition, the damage extends from the retina to the visual center in the brain, although the primary region of damage is thought to be the optic nerve head (ONH), with the lateral geniculate nucleus (LGN) being secondarily affected. We investigated time-dependent alterations in the ONH, the optic nerve (ON), and the LGN after intraocular pressure (IOP) elevation in Japanese monkeys (a species more similar to humans than other macaque species). Nine Japanese monkeys, each with an experimental glaucomatous left eye, and two naive monkeys were studied. Ocular-testing sessions (including IOP measurement and fundus photography) were held weekly. Eyes and brains were enucleated at 2-48 weeks after IOP elevation, and alterations in ONs and LGN were evaluated. The IOP of the treated eyes was monitored periodically and found to be elevated continuously throughout the observation period in each monkey. The ONH of the glaucomatous eyes exhibited time-dependent deep cupping and thinning of the rim area from 2 weeks after the IOP elevation. Loss of axons and a decrease in the area of ON were first observed at 4 and 28 weeks, respectively. Neuronal loss was first observed at 2 weeks in layers 1 and 2 of LGN [magnocellular (M)-layer] and at 12 weeks in layers 3-6 of LGN [parvocellular (P)-layer]. Neuronal shrinkage was first observed at 2 weeks in all layers in LGN. These findings indicate that in Japanese monkeys, damage to neurons in LGN can be detected in the early phase (first few weeks) after an IOP elevation, as can damage to ONH.     

Evaluation of inducible nitric oxide synthase in glaucomatous optic neuropathy and pressure-induced optic nerve damage

PURPOSE: To determine whether inducible nitric oxide synthase (NOS-2) is involved in glaucomatous optic neuropathy. METHODS: Chronic elevation of rat intraocular pressure (IOP) leading to optic nerve damage was induced by episcleral injection of hypertonic saline, which caused sclerosis and blockade of aqueous humor outflow pathways. Expression of NOS-2 in the retina and optic nerve head (ONH) was evaluated by immunohistochemistry, gene array analysis, and quantitative PCR (Q-PCR). Immunohistochemistry was also used to assess the NOS-2 level in the ONH from primary open-angle glaucoma (POAG) and nonglaucomatous human eyes. Finally, an NOS-2 inhibitor, aminoguanidine, administered orally in the drinking water, was tested for its effect on optic nerve injury in rats with ocular hypertension. RESULTS: Chronically elevated IOP in the rat produced optic nerve damage that correlated with pressure change (r(2) = 0.77), but did not increase NOS-2 immunoreactivity in the optic nerve, ONH, or ganglion cell layer. Retinal and ONH NOS-2 mRNA levels did not correlate with either IOP level or severity of optic nerve injury. Similarly, there was no difference in NOS-2 immunoreactivity in the optic nerve or ONH between POAG and nonglaucomatous eyes. Furthermore, aminoguanidine treatment did not affect the development of pressure-induced optic neuropathy in the rat. CONCLUSIONS: As demonstrated by several independent methods, glaucomatous optic neuropathy was not associated with a significant change in the expression of NOS-2 in the retina, ONH, or optic nerve.     

A Potential Role of Acute Choroidal Expansion in Nonarteritic Anterior Ischemic Optic Neuropathy

PurposeNonarteritic anterior ischemic optic neuropathy (NAION) has been associated with a thickened choroid at the optic nerve head (ONH). Here, we use computational modeling to better understand how choroidal expansion and choroidal geometry influence tissue deformation within the ONH relative to intraocular pressure (IOP) and intracranial pressure (ICP) effects.MethodsUsing a model of the posterior eye that included the sclera, peripapillary sclera, annular ring, pia mater, dura mater, neural tissues, Bruch''s membrane, choroid, and lamina cribrosa, we examined how varying material properties of ocular tissues influenced ONH deformations under physiological and supra-physiological, or “pathological,” conditions. We considered choroidal expansion (c. 35 µL of expansion), elevated IOP (30 mm Hg), and elevated ICP (20 mm Hg), and calculated peak strains in the ONH relative to a baseline condition representing an individual in the upright position.ResultsSupra-physiological choroidal expansion had the largest impact on strains in the prelaminar neural tissue. In addition, compared to a tapered choroid, a “blunt” choroid insertion at the ONH resulted in higher strains. Elevated IOP and ICP caused the highest strains within the lamina cribrosa and retrolaminar neural tissue, respectively.ConclusionsAcute choroidal expansion caused large deformations of the ONH and these deformations were impacted by choroid geometry. These results are consistent with the concept that compartment syndrome due to the choroid geometry and/or expansion at the ONH contributes to NAION. Prolonged deformations due to supra-physiological loading may induce a mechanobiological response or ischemia, highlighting the potential impact of choroidal expansion on biomechanical strains in the ONH.     

Effect of ifenprodil on ocular tissue circulation in rabbits.

Ifenprodil tartrate has long been employed as a cerebral vasodilator with alpha and N-methyl-D-aspartate (NMDA) receptor antagonistic activities. The purpose of this study was to evaluate the effects of ifenprodil on ocular circulation in rabbits. Experiments were performed during the dark phase in Dutch rabbits conditioned to a schedule of alternating 12-hr periods of light and dark. Effects on ocular tissue blood velocity were estimated using the laser speckle method in the iris, posterior choroid, and optic nerve head (ONH). Measurements of tissue blood velocity were performed both after intravenous injection of ifenprodil at a dose of 0.2 mg/kg, 0.1 mg/kg, and the same volume of the vehicle, and after topical instillation of 0.5% ifenprodil (50 microl) twice daily for 1, 3 and 20 days unilaterally in a masked manner. Intraocular pressure (IOP) was also measured during the experimental period. Intravenous administration of ifenprodil caused a significant increase in blood velocity in the ONH, choroid, and iris, but ONH circulation was affected at a lower dose than uveal circulation. In the topical instillation experiment, IOP in the ifenprodil-treated eye was significantly lower, by approximately 2 mmHg, than that in the contralateral eye when the laser speckle measurement was performed. Twice-daily, unilateral 0.5% ifenprodil instillation significantly increased blood velocity in the iris after 3 days and that in the ONH and posterior choroid after 20 days in the treated eye. Topical 0.5% ifenprodil increased blood velocity in the iris, posterior choroid, and ONH after multiple dosings. After systemic administration, ONH circulation appeared to be influenced at a lower dose than was uveal circulation.     

高眼压下视乳头形态和血流改变的顺序研究

目的:探索机械压力导致的高眼压下视乳头形态学改变和视网膜血管密度改变的顺序。方法:前瞻性研究。纳入健康志愿者34例34眼。A组23例,其测试流程包括基线,两段高眼压期(15mmHg和30mmHg分别持续2min)和恢复期。B组11例,其高眼压期为眼压升高15mmHg持续10min。每阶段均采用OCT测量视乳头的布氏膜开口距离(BMO)、视乳头表面深度(ONHSD)和黄斑中心凹下脉络膜厚度(SFCT),并采用OCTA测量血管密度。结果:A组第一次眼压升高后,视乳头血管密度下降[浅层毛细血管丛,从(67.39±7.65)%降至(43.78±5.89)%,P<0.05],BMO距离、ONHSD和黄斑血管密度、SFCT均无改变。在第二次眼压升高后,视乳头及黄斑区的血管密度均下降,BMO距离、ONHSD增加(均P<0.05)。B组眼压升高后,视乳头及黄斑区的血管密度均下降,BMO距离增加,SFCT不变。视乳头的血管密度降低与BMO距离增加没有相关性(r=0.050,P>0.05)。结论:视乳头组织相对于形态学改变,更容易出现血流改变。在眼压升高过程中,视乳头和黄斑区的血流动力学改变特征不同。     

Oxygen saturation in optic nerve head structures by hyperspectral image analysis

PURPOSE: A method is presented for the calculation and visualization of percent blood oxygen saturation from specific tissue structures in hyperspectral images of the optic nerve head (ONH). METHODS: Trans-pupillary images of the primate optic nerve head and overlying retinal blood vessels were obtained with a hyperspectral imaging (HSI) system attached to a fundus camera. Images were recorded during normal blood flow and after partially interrupting flow to the ONH and retinal circulation by elevation of the intraocular pressure (IOP) from 10 mmHg to 55 mmHg in steps. Percent oxygen saturation was calculated from groups of pixels associated with separate tissue structures, using a linear least-squares curve fit of the recorded hemoglobin spectrum to reference spectra obtained from fully oxygenated and deoxygenated red cell suspensions. Color maps of saturation were obtained from a new algorithm that enables comparison of oxygen saturation from large vessels and tissue areas in hyperspectral images. RESULTS: Percent saturation in retinal vessels and from the average over ONH structures (IOP = 10 mmHg) was (mean +/- SE): artery 81.8 +/- 0.4%, vein 42.6 +/- 0.9%, average ONH 68.3 +/- 0.4%. Raising IOP from 10 mmHg to 55 mmHg for 5 min caused blood oxygen saturation to decrease (mean +/- SE): artery 46.1 +/- 6.2%, vein 36.1 +/- 1.6%, average ONH 41.9 +/- 1.6%. The temporal cup showed the highest saturation at low and high IOP (77.3 +/- 1.0% and 60.1 +/- 4.0%) and the least reduction in saturation at high IOP (22.3%) compared with that of the average ONH (38.6%). A linear relationship was found between saturation indices obtained from the algorithm and percent saturation values obtained by spectral curve fits to calibrated red cell samples. CONCLUSIONS: Percent oxygen saturation was determined from hyperspectral images of the ONH tissue and retinal vessels overlying the ONH at normal and elevated IOP. Pressure elevation was shown to reduce blood oxygen saturation in vessels and ONH structures, with the smallest reduction in the ONH observed in the temporal cup. IOP-induced saturation changes were visualized in color maps using an algorithm that follows saturation-dependent changes in the blood spectrum and blood volume differences across tissue. Reduced arterial saturation at high IOP may have resulted from a flow-dependent mechanism.     

Effects of caffeine on microcirculation of the human ocular fundus

PURPOSE: To determine the effect of caffeine on microcirculation in the human ocular fundus. METHODS: The microcirculation in the ocular fundus of 10 healthy volunteers (10 eyes) was studied using a laser speckle tissue circulation analyzer. Caffeine or placebo (100 mg) was administered orally in a double-masked manner. Square blur rate (SBR), a quantitative index of blood flow velocity, was measured in a temporal site of the optic nerve head (ONH) free of surface vessels and in a middle site of the choroid-retina between the ONH and macula. Intraocular pressure (IOP), blood pressure (BP), pulse rate (PR), and central critical fusion frequency (CFF) were also measured. These parameters were measured before and for 2 hours after administration. The area under curve (AUC) of SBR was calculated for each area. Ocular perfusion pressure (OPP) was also calculated from BP and IOP. RESULTS: The time-course of change in SBR value showed much individual difference. Caffeine decreased the AUC of SBR in the ONH (P =.0218) as well as in the choroid-retina (P =.0469) significantly. IOP, mean BP, PR, OPP, and central CFF did not change significantly. CONCLUSIONS: These results suggest that caffeine may increase blood vessel resistance and decrease blood flow in the human ONH and choroid-retina.     

Effects of lomerizine, a calcium channel antagonist, on retinal and optic nerve head circulation in rabbits and humans

PURPOSE: To investigate the effects of lomerizine, a Ca2+ antagonist, on the ocular tissue circulation in rabbits and on the circulation in the optic nerve head (ONH) and choroid in healthy volunteers. METHODS: Lomerizine (0.1 [n=10] or 0.3 [n=11] mg/kg) or vehicle solution (n=11) was injected intravenously in urethane-anesthetized rabbits, and blood flow in the retina, choroid, and iris-ciliary body was measured by the microsphere method and that in the ONH by the H2 gas-clearance method (0.1 [n=6] or 0.3 [n=9] mg/kg or vehicle, n=6). Oral 5 mg lomerizine or placebo was administered to volunteers (n=8) in a crossover study, and in areas of the fovea and ONH, the normalized blur (NB), a quantitative index of blood velocity, was measured, together with blood pressure, heart rate, and intraocular pressure (IOP), before and 1.5, 3, 6, and 9 hours after administration. RESULTS: Blood flow in the rabbit retina increased significantly in the lomerizine-treated group, but blood flow changed little in the choroid or iris-ciliary body. Blood flow in the rabbit ONH also showed a significant increase in the lomerizine-treated group. In human studies, the NB obtained from the ONH during the experimental period showed a small but significant increase in the lomerizine-treated group compared with the placebo-treated group, but no significant intergroup difference was detected in the NB obtained from the fovea or in blood pressure, heart rate, or IOP. CONCLUSIONS: Lomerizine increases blood velocity, and probably blood flow, in the ONH and retina in rabbits, and it also increases blood velocity in the ONH in healthy humans, without significantly altering blood pressure or heart rate.     

Effect of acute increases in intraocular pressure on intravascular optic nerve head oxygen tension in cats.

A newly developed phosphorescence imaging technique was used to generate two-dimensional maps of intravascular oxygen tension (PO2) in the optic nerve head (ONH) and retina of the cat to study the effects of acute moderate increases in intraocular pressure (IOP) on the ONH and retinal PO2. Both the ONH and retinal PO2 were remarkably well maintained as the IOP increased; hypoxia developed only after the blood flow to the eye was stopped. Because ONH hypoxia was not observed during IOP elevation, a lack of oxygen may not be a major cause of glaucomatous damage, although the effects of chronically elevated IOP on the PO2 remain to be evaluated. Because this imaging technique was noninvasive and required only a small bolus injection of a nontoxic oxygen probe, the authors anticipate that it will find significant application in the study of many ocular vascular diseases and glaucoma.     

Effect of topical amosulalol on tissue circulation in the optic nerve head.

The effect of topical 0.1% amosulalol on tissue circulation in the albino rabbit optic nerve head (ONH) was investigated using a laser speckle tissue circulation analyzer. Amosulalol was administered into one eye twice daily for 20 days, and vehicle was administered into the other eye in a masked, randomized manner. Intraocular pressure (IOP) was measured every 5 days. The normalized blur value (NB), a quantitative index of tissue blood flow velocity in the ONH, was measured before treatment and 2 hours after the last instillation on day 20. The IOP was also measured at 5-day intervals. Amosulalol decreased IOP by approximately 2 mmHg in the treated eyes (P < 0.01). There was no significant difference in NB between eyes before the first instillation, whereas NB was significantly greater (by approximately 16%) in the amosulalol-treated eye than in the control eye after completion of instillations (P < 0.01). The difference between NB after completion of instillations and that before the first instillation was significantly greater in the ONH of the amosulalol-treated eye than in the contralateral control eye (P < 0.01). Twice-daily instillation of 0.1% amosulalol for 20 days induced a significant increase in tissue blood velocity in the ipsilateral ONH in albino rabbits.     

Effect of caffeine on microcirculation of human ocular fundus]

PURPOSE: To determine the effect of caffeine on the microcirculation in the human ocular fundus. SUBJECTS AND METHODS: The microcirculation of the ocular fundus in 10 eyes of 10 healthy volunteers was studied using a laser speckle tissue circulation analyser. 100 mg of caffeine or placebo was given orally in a double-blind test. Square blur rate(SBR), a quantitative index of blood flow velocity, was measured in the temporal site of the optic nerve head(ONH) free of surface vessels and in the middle site of the choroid-retina between the ONH and the macula. Intraocular pressure(IOP), blood pressure(BP), pulse rate(PR), and central critical fusion frequency(CFF) were also measured. These parameters were measured before and for 2 hours after administration. The area under curve(AUC), of the SBR was calculated for each area. Ocular perfusion pressure(OPP) was also obtained from blood pressure and intraocular pressure. RESULTS: The time-course change of SBR value showed much individual difference. Caffeine decreased the AUC of the SBR in the ONH as well as in the choroid-retina significantly. IOP, mean BP, PR, OPP and central CFF did not change significantly. CONCLUSIONS: These results suggest that caffeine may increase blood vessel resistance and decrease blood flow in the ONH and choroid-retina in humans.     

Optic nerve head morphology in young patients after antiglaucomatous filtering surgery

Purpose: To compare the optic nerve head appearance in glaucomatous eyes before and after marked reduction of intraocular pressure (IOP). Methods: The hospital‐based observational case‐series study included selected glaucoma patients for whom optic disc photographs taken before and 1 week to 5 months after surgical reduction of IOP were morphometrically examined. Results: The study included 23 eyes of 16 patients (mean age: 28.7 ± 6.0 years). Mean preoperative IOP was 31.6 ± 7.7 mmHg (22–52 mmHg), and mean IOP drop was 21.5 ± 8.4 mmHg (11–45 mmHg). The horizontal disc diameter decreased significantly (p < 0.001) after surgery, while the vertical disc diameter did not change markedly (p = 0.54). The width of the neuroretinal rim increased significantly in all disc quadrants (all p‐values ≤ 0.01), optic cup depth decreased (p < 0.001), and reflectivity of the inner retinal surface increased significantly (p < 0.001). Some eyes showed a pronounced reduction in beta zone of parapapillary atrophy parallel to an increase in horizontal disc diameter, and some eyes showed an enlargement of beta zone parallel to a reduction in horizontal disc diameter. Conclusions: After marked reduction of high IOP, some eyes of young adult patients with glaucoma can show a horizontal shrinkage of the optic nerve head, in addition to a partial restoration of the neuroretinal rim and a flattening of the optic cup. In addition, beta zone of parapapillary atrophy can decrease or increase, complementarily to changes in the horizontal disc diameter. These findings may be of interest for the biomechanics of the optic nerve head and the precision of imaging techniques.     

First-line therapy with latanoprost 0.005% results in improved ocular circulation in newly diagnosed primary open-angle glaucoma patients: a prospective, 6-month, open-label study

PURPOSE: To evaluate the effect of latanoprost 0.005% on the optic nerve head (ONH) and retinal circulation of newly diagnosed and previously untreated primary open-angle glaucoma (POAG) patients.METHODS: Twenty-two newly diagnosed and previously untreated POAG patients (mean age+/-SD: 68.38+/-11.92 years) were included in this longitudinal open-label study. Patients were treated with latanoprost 0.005% once a day. Intraocular pressure (IOP), systemic blood pressure (BP), mean ocular perfusion pressure (MOPP), and ocular perfusion parameters 'volume', 'velocity', and 'flow' measured at the optic nerve head (ONH) and retina by means of Heidelberg Retina Flowmeter system were evaluated during a 6-month follow-up period.RESULTS: Treatment with latanoprost 0.005% resulted in a significant decrease in IOP (P<0.0001) and increase in MOPP (P<0.0001). After correcting for changes in MOPP, the blood velocity measured at the ONH level was significantly higher after 6 months of treatment than at baseline (P=0.0310). In addition, blood volume and flow measured at the peripapillary retina level improved after 3 and 6 months of treatment (P=0.0170; P=0.0260, and P=0.0170; P=0.0240 respectively).CONCLUSION: Previously untreated POAG patients exhibit reduced IOP, increased MOPP and improved ocular perfusion at the ONH and retina levels when treated with Latanoprost 0.005%. These effects could be beneficial for glaucoma patients suffering from ocular vascular dysregulation.