Low Ocular Perfusion Pressure Research Articles

Glaucoma: from pathogenic mechanisms to retinal glial cell response to damage

Glaucoma is a neurodegenerative disease of the retina characterized by the irreversible loss of retinal ganglion cells (RGCs) leading to visual loss. Degeneration of RGCs and loss of their axons, as well as damage and remodeling of the lamina cribrosa are the main events in the pathogenesis of glaucoma. Different molecular pathways are involved in RGC death, which are triggered and exacerbated as a consequence of a number of risk factors such as elevated intraocular pressure (IOP), age, ocular biomechanics, or low ocular perfusion pressure. Increased IOP is one of the most important risk factors associated with this pathology and the only one for which treatment is currently available, nevertheless, on many cases the progression of the disease continues, despite IOP control. Thus, the IOP elevation is not the only trigger of glaucomatous damage, showing the evidence that other factors can induce RGCs death in this pathology, would be involved in the advance of glaucomatous neurodegeneration. The underlying mechanisms driving the neurodegenerative process in glaucoma include ischemia/hypoxia, mitochondrial dysfunction, oxidative stress and neuroinflammation. In glaucoma, like as other neurodegenerative disorders, the immune system is involved and immunoregulation is conducted mainly by glial cells, microglia, astrocytes, and Müller cells. The increase in IOP produces the activation of glial cells in the retinal tissue. Chronic activation of glial cells in glaucoma may provoke a proinflammatory state at the retinal level inducing blood retinal barrier disruption and RGCs death. The modulation of the immune response in glaucoma as well as the activation of glial cells constitute an interesting new approach in the treatment of glaucoma.

Risk factors and macular microvascular changes in open angle glaucoma progression: A longitudinal study using OCT‐A

Aims/Purpose: To investigate prospectively macular microvascular changes in patients with glaucoma and identify common characteristics among the progressive eyes.Methods: A 12‐month prospective longitudinal study was performed with 124 open‐angle‐glaucoma‐eyes (GE). Glaucomatous progression was defined as a decrease of ≥5 μm in average or ≥7 μm in a sector of RNFL thickness. OMAG OCT microangiography (Angioplex, HD OCT, Cirrus 5000, Zeiss) was used to analyse the macular region. The statistical analysis was performed using the SPSS version 23.0 statistical package (SPSS Inc., IL).Results: Among the GE group, 22.36% of eyes showed progression, being the decrease of the Complete Region Macular Vessel Density (MVD) and Macular Capillary Perfusion Density (MPD) greater (−1.14 mm/mm2 and −3.18%) compared to non‐progressive eyes (−0.42 mm/mm2 and −1.02%) [p = 0.123 and 0.057], being the temporal and superior sectors for both MVD and MPD, the ones that showed greater differences (−1.44 mm/mm2, −1.11 mm/mm2, −3.6% and −2.95% respectively) [p > 0.05 for all]. Characteristics as elevated intraocular pressure (IOP) (17.29 vs 14.87 mmHg), thinner central corneal thickness (CCT) (521.53 vs 538.65 μm) and lower ocular perfusion pressure (OPP) (45.88 vs 49.21 mmHg) were significantly different in those progressive GE [p < 0′05 for all]. Nevertheless, increased vertical cup to disc ratio (CDV) (0.64 vs 0.63) and minimum ganglion cell layer thickness (GCLM) (58,82 vs 56.51 μm) were not significantly different in progressive GE [p = 0.768 and 0.249].Conclusions: Data showed that when glaucomatous progression took place, stronger vascular changes occurred in the macular area, as greater decrease of MVD and MPD specially in the temporal and superior sectors. In addition, common characteristics as elevated intraocular pressure, thinner central corneal thickness and lower ocular perfusion pressure were identified in progressive GE. Nevertheless, further research with larger population and larger follow‐up is needed to obtain stronger results.

Effect of 24-h blood pressure dysregulations and reduced ocular perfusion pressure in open-angle glaucoma progression.

Low ocular perfusion pressure (OPP), which depends on the mean arterial pressure (MAP) and intraocular pressure (IOP), is associated with glaucoma. We studied 24-h MAP dysregulations and OPP in relation to the progression of glaucoma damage. We retrospectively analyzed 155 normal-tension glaucoma (NTG) and 110 primary open-angle glaucoma (POAG) patients aged 18 years old followed at the University Hospital Leuven with repeated visual field tests (n = 7000 measures, including both eyes) who underwent 24-h ambulatory blood pressure monitoring. Twenty-four-hour MAP dysregulations were variability independent of the mean (VIM), and the five lowest dips in MAP readings over 24 h. OPP was the difference between 2/3 of the MAP and IOP. Glaucoma progression was the deterioration of the visual field, expressed as decibel (dB) changes in mean deviation analyzed by applying multivariable linear mixed regression models. The mean age was 68 years (53% were women). High 24-h VIMmap was associated with glaucoma progression in POAG (P < 0.001) independently of the 24-h MAP level. The estimated changes in mean deviation in relation to dip MAP measures ranged from -2.84 dB [95% confidence interval (CI) -4.12 to -1.57] to -2.16 dB (95% CI -3.46 to -0.85) in POAG. Reduced OPP along with high variability and dips in MAP resulted in worse mean deviation deterioration. The progression of glaucoma damage associates with repetitive and extreme dips in MAP caused by high variability in MAP throughout 24 h. This progression exacerbates if 24-h MAP dysregulations occur along with reduced OPP.

Системная гипотония и низкое перфузионное давление как факторы прогрессирования первичной открытоугольной глаукомы

Glaucoma progression is still a relevant issue in up-to-date ophthalmology. An important prerequisite for stabilizing glaucoma is the achievement of the target intraocular pressure (IOP). However, many patients with primary open-angle glaucoma (POAG) continue to suffer vision loss despite IOP reduction. Additional factors are also important for glaucoma progression, e.g., blood pressure (BP) and ocular perfusion pressure (OPP). Multiple published data have shown a decrease in blood flow velocity in the retrobulbar vessels, choroid, retina, and optic nerve in patients with glaucoma. A decrease in OPP is a predictor of insufficient intraocular blood supply. Systemic BP has a strong effect on OPP. Intensive treatment for hypertension significantly reduces BP, decreases OPP, and prevents the progression of glaucomatous optic neuropathy. A new paradigm shift that implies a personalized approach to the choice of diagnostic and treatment strategy for glaucoma is emerging. This paper reviews current published data on the effect of systemic hypotension and low OPP on POAG progression. KEYWORDS: glaucoma, intraocular pressure, blood pressure, hypertension, hypotension, perfusion pressure. FOR CITATION: Мyakonkaya O.S., Sarkisyan A.S., Seleznev A.V., Kuroyedov A.V., Brezhnev A.Yu. Systemic hypotension and low perfusion pressure as risk factors for primary open-angle glaucoma progression. Russian Journal of Clinical Ophthalmology. 2023;23(4):202–206 (in Russ.). DOI: 10.32364/2311-7729-2023-23-4-5.

Evaluation of Ocular Perfusion Pressure in Migraine Patients: A Case-control Study

Introduction: Vascular dysregulation is a common underlying factor between migraine and glaucoma. Fluctuations in Ocular Perfusion Pressure (OPP) can lead to ischaemia and damage to the optic nerve head. It is unclear if the risk of glaucoma in migraine patients is due to low OPP. Aim: To compare the OPP of migraine patients with healthy controls and assess the role of OPP as a risk factor for glaucoma in migraine patients. Materials and Methods: This case-control study was conducted from June 2019 to May 2020 at Yenepoya Medical College Hospital, Mangaluru, Karnataka, India. Adult patients of either gender, aged between 18 and 40 years, diagnosed with migraine, were included in the study. Intraocular Pressure (IOP), blood pressure, and OPP were measured in 94 migraine patients and compared with 94 age-matched controls. Data were analysed using Statistical Package for the Social Sciences (SPSS) version 23.0. Independent t-tests were used for comparison. Adjusted odds ratios were calculated using binary logistic regression, and a p-value &lt;0.05 was considered statistically significant. Results: The mean IOP was 13.27±2.02 mmHg among cases and 13.38±1.87 mmHg among controls. The mean Systolic Blood Pressure (SBP) was 118.91±4.67 mmHg among cases and 116.09±5.18 mmHg among controls. The mean Diastolic Blood Pressure (DBP) was 77.72±4.48 mmHg among cases and 75.77±4.89 mmHg among controls. The mean OPP was 47.69±2.43 mmHg among cases and 46.08±2.46 mmHg among controls. The t-test values showed a statistically significant difference in SBP, DBP, and OPP between the two groups (p-value&lt;0.05). Conclusion: The OPP in migraine patients differed significantly from that of the controls. However, further studies are needed to evaluate the relationship between perfusion pressure abnormalities and the risk of glaucoma in migraine patients.

Macular and peripapillary microvascular changes in open angle glaucoma and ocular hypertension: A longitudinal study using optical coherence tomography angiography (OCT‐A)

AbstractPurpose: To investigate prospectively macular and peripapillary microvascular changes in patients with glaucoma and ocular hypertension.Methods: A 12‐month prospective longitudinal study was performed with 124 open‐angle‐glaucoma‐eyes (GE), 111 ocular‐hypertension‐eyes (OHE) and 98 gender and age matched control‐eyes (CE). Glaucomatous progression was defined as a decrease of ≥5 μm in average or ≥7 μm in a sector of RNFL thickness. OMAG OCT microangiography (Angioplex, HD OCT, Cirrus 5000, Zeiss) was used to analyse optic disc and macular regions. The statistical analysis was performed using Mann–Whitney‐Test with the SPSS version 23.0 statistical package (SPSS Inc., IL).Results: Among OHE and GE groups, 21.7% of eyes showed progression, being the decrease of Peripapillary Flux Index (PFI), Macular Vessel Density (MVD) and Macular Capillary Perfusion Density (MPD) greater (−0.0067; −0.696 mm/mm2 and −1.56%) compared to non‐progressive eyes (+0.0038; 0.527 mm/mm2 and 1.55%) being the nasal and inferior sectors for PFI, and the superior and temporal sectors for both MVD and MPD, the ones that showed greater differences [p = 0.015 and p &lt; 0.001 for the last two]. Furthermore, Peripapillary Perfusion Density (PPD) showed non‐significant greater decrease (−0.347) compared to non‐progressive eyes (−0.324) [p = 0.775]. Characteristics as increased vertical cup to disc ratio (CDV) (0.64 vs. 0.57), elevated intraocular pressure (IOP) (18.25 vs. 15.40 mmHg), thinner central corneal thickness (CCT) (520.18 vs. 541.67 μm) and lower ocular perfusion pressure (OPP) (47.81 vs. 48.95 mmHg) were significantly different in those progressive OHE and GE [p &lt; 0.05 for all]. Nevertheless, minimum ganglion cell layer thickness (GCLM) was only significantly lower in progressive GE (58.51 vs. 73.98 μm) [p = 0.036].Conclusions: Data showed that when glaucomatous progression took place, stronger microvascular changes occurred in the macular and peripapillary areas, as greater decrease of MVD, MPD and PFI, especially in superior and temporal sectors for the macular area, and in nasal and inferior sectors for the peripapillary area. Nevertheless, further research with larger population and larger follow‐up is needed to obtain stronger results.

A cross-sectional study of association between ocular pressures and different grades of myopia in young adults

Introduction and Aim: My­opia is one of the most common refractive errors causing visual disability worldwide. Uncorrected refractive error poses a public health challenge especially in young adults who have to spend most of their time in literary works. Intra ocular pressure (IOP) is one of the crucial factors intertwined in the pathophysiology of myopia. Ocular perfusion pressure (OPP) determines ocular blood flow. Studies done on association between IOP and refractive errors are contradictory. There is paucity of literature on relationship between OPP and myopia. Hence this original article aimed to assess the association of IOP and OPP changes with myopia and to analyze the relationship between ocular pressures with severity of myopia. Materials and Methods: Hundred normal adults in the age group of 18-24 years of either gender were recruited for the present study. Voluntary written and informed consent was sought from all participants and the refractive power of their eyes was noted. They were categorised into three groups based on the severity of myopia. Controls were the emmetropes. All participants were asked to relax for 5-10 minutes and the resting BP and IOP were recorded using sphygmomanometer and rebound tonometer respectively. OPP was calculated. Results: IOP values were comparatively higher in myopes than emmetropes. A significant reduction in OPP values were observed in moderate myopes. Conclusion: Myopes have a higher IOP suggesting myopia is one of the major risk factor for ocular hypertension. Low OPP values in moderate myopes indicate reduced ocular perfusion, making the progressive myopes highly susceptible to glaucoma.

A review of ocular perfusion pressure and retinal thickness: A case for the role of systemic hypotension in glaucoma

Background: Ocular perfusion pressure (OPP) is defined as blood pressure (BP) minus intraocular pressure (IOP). Low OPP may result in decreased ocular blood flow (OBF) and oxygen to the optic nerve head (ONH) and retina.Aim: To review the role of systemic hypotension and similar conditions in OPP and its influence on retinal nerve fibre layer (RNFL) thickness and the ganglion cell complex (GCC).Method: A literature search was conducted using the following search terms: ‘systemic hypotension’; ‘glaucoma’; ‘retinal nerve fibre layer’; ‘optic nerve’; ‘ocular blood flow’ and ‘ocular perfusion pressure’.Results: The Los Angeles Eye Study and Barbados Eye Study found that decreased OPP and BP increased the risk of glaucoma development by up to six times. Reduced retinal perfusion with resultant thinning of the RNFL in conditions with a similar mechanism, such as obstructive sleep apnoea syndrome, has indicated the importance of reduced OPP in retinal thickness. In the absence of any study directly showing the effect of systemic hypotension on OPP and retinal thickness, a working hypothesis proposes that reduced BP with or without normal-to-raised IOP will reduce OPP. The reduced OPP and OBF in those with systemic hypotension may result in oxidative stress and hypoxia which may then cause retinal ganglion cell death and the resultant retinal thinning.Conclusion: The increased risk of glaucoma development and progression relating to decreased BP and OPP has been proven to be of importance. Monitoring patients with systemic hypotension and evaluating the macula, ONH RNFL and GCC thickness may alert clinicians to possible glaucomatous changes.

The Effect of Ocular Perfusion Pressure on Retinal Thickness in Young People with Presumed Systemic Hypotension.

Low ocular perfusion pressure (OPP) may increase the risk of optic neuropathy. This study investigated the effects of OPP on the ganglion cell complex (GCC) and optic nerve head-retinal nerve fibre layer (ONH-RNFL) thickness in presumed systemic hypotensives (PSH). Fifteen participants with PSH and 14 controls underwent automated sphygmomanometry and Icare tonometry to calculate OPP: mean OPP (MOPP), systolic OPP (SOPP), and diastolic OPP (DOPP). ONH-RNFL and macula GCC thickness were evaluated using the Optovue iVue optical coherence tomographer. Statistical analysis comprised independent t-tests, the Mann–Whitney U test and binary logistic regression analysis. There was no significant difference when comparing ONH-RNFL and macula GCC thickness between both groups. Increased MOPP (OR = 0.51; 95% CI: 0.27–0.97; p = 0.039) and SOPP (OR = 0.79; 95% CI: 0.64–0.98; p = 0.035) were significantly associated with a decreased risk of reductions in GCC total thickness. Increased SOPP (OR = 0.11; 95% CI: 0.01–0.89; p = 0.027) was significantly associated with a decreased risk of reductions in the average ONH-RNFL thickness. The study found no significant retinal thickness changes in PSH’s, in comparison to the controls. The study established that, by increasing MOPP and SOPP, there was a decreased risk of reductions in the total GCC thickness and average ONH-RNFL thickness. Higher SOPP may decrease the possibility of retinal thinning of the GCC and ONH-RNFL. However, higher MOPP may decrease the odds of thinning of the GCC before ONH-RNFL changes.

English

BACKGROUND Glaucoma is the second most leading cause of visual loss in the world. Different socio epidemiological parameters like gender, age, socio-economic status, educational status etc. has been directly linked to occurrence of glaucoma in previous studies. Review of the western literature showed that the risk factors associated with glaucoma were high intra ocular pressure (IOP), low blood pressure, low ocular perfusion pressure, narrow anterior chamber angles, thin corneas, pseudoexfoliation, a low body mass index (BMI), and myopia. We need to evaluate the clinical and epidemiological factors affecting primary open angle glaucoma. METHODS Records of patients with a diagnosis of primary open-angle glaucoma (POAG) were studied. All data, addressing demographics (gender, age and skin colour), socioeconomic status, educational status, emotional status and clinical information concerning risk factors for developing glaucoma (family history of glaucoma, hypertension and diabetes mellitus) and any treatment history (e.g., corticosteroid intake) were noted. Findings from visual acuity examination, refraction, detailed anterior segment examination by slit lamp, fundus examination with 90 D, gonioscopy, applanation tonometry, VF examination by automated perimetry and A-scan USG were also carefully taken into account. RESULTS A total 920 patients were enrolled of which 67.94 % were males and 57.6 % were from urban population. 18.7 % cases had positive family history. Most of the patients came from lower and middle-income group (43.48 % and 48.37 % respectively). Cup-disc ratio of majority of eyes was found to be more than 0.30 (97.29 %). Different grades of disc changes and field changes were noted. Cupdisc ratio asymmetry of more than 0.20 was found in 355 (38.59 %) eyes. Paracentral and / or arcuate scotoma was detected in 585 eyes (31.80 %). CONCLUSIONS Understanding the socio-demography and socio-economy helps in early diagnosis and better assessment of the disease severity in POAG. KEYWORDS Glaucoma, POAG, CDR, Visual Fields

Energy Metabolism in the Inner Retina in Health and Glaucoma

Glaucoma, the leading cause of irreversible blindness, is a heterogeneous group of diseases characterized by progressive loss of retinal ganglion cells (RGCs) and their axons and leads to visual loss and blindness. Risk factors for the onset and progression of glaucoma include systemic and ocular factors such as older age, lower ocular perfusion pressure, and intraocular pressure (IOP). Early signs of RGC damage comprise impairment of axonal transport, downregulation of specific genes and metabolic changes. The brain is often cited to be the highest energy-demanding tissue of the human body. The retina is estimated to have equally high demands. RGCs are particularly active in metabolism and vulnerable to energy insufficiency. Understanding the energy metabolism of the inner retina, especially of the RGCs, is pivotal for understanding glaucoma’s pathophysiology. Here we review the key contributors to the high energy demands in the retina and the distinguishing features of energy metabolism of the inner retina. The major features of glaucoma include progressive cell death of retinal ganglions and optic nerve damage. Therefore, this review focuses on the energetic budget of the retinal ganglion cells, optic nerve and the relevant cells that surround them.

Ocular blood flow study using color doppler imaging: Normative value and its relevance in glaucoma

Aim: The aim was to study the normative pattern of ocular blood flow (OBF) using color Doppler imaging. Materials and Methods: It was a prospective study including healthy volunteers without any ocular pathology. Results: We analyzed ocular blood flow for 25 eyes of consecutive normal patients. Our study had 14 males and 11 females. The standard deviation of the resistive index of Ophthalmic artery, Central retinal artery and short posterior ciliary artery were 0.07, 0.08 and 0.12 respectively. Discussion: Ischemia to the optic nerve and dysfunctional vascular regulation are likely responsible for glaucomatous damage. Ocular hemodynamics, though complex, can be assessed to an extent by many ways. The quantification of blood flow in these vessels can give great lengths of information with regard to the pathological processes behind retinal and optic nerve head diseases such as glaucoma. Lower ocular perfusion pressure, vascular dysregulation, and lower OBF can worsen glaucoma. Conclusion: To our knowledge, there are no South Indian studies showing the normative data.

Primary Open-Angle Glaucoma Preferred Practice Pattern®

BackgroundPrimary open angle glaucoma (POAG) is a chronic, progressive ocular disease causing loss of the optic nerve rim and retinal nerve fiber layer (RNFL) with associated visual field defects. The anterior chamber angle is open, and the disease is generally bilateral. Risk factors for POAG include older age, African race or Latino/Hispanic ethnicity, elevated intraocular pressure (IOP), family history of glaucoma, lower ocular perfusion pressure, type 2 diabetes mellitus, and thin central cornea. It is estimated that 53 million people in the world have POAG in 2020 with a prevalence of 3.0% in the population aged 40 to 80 years. Rationale for TreatmentClinical trials have shown that lowering IOP reduces the risk of developing POAG and slows the progression of the disease. Medical, laser, and incisional surgical approaches exist to effectively lower IOP. Early diagnosis and treatment generally prevent visual disability. Care ProcessThe goals of managing patients with POAG are to control IOP in a target range and to prevent progressive visual field and optic nerve/RNFL damage in order to preserve visual function and quality of life. The initial glaucoma evaluation includes all components of the comprehensive adult medical evaluation focusing on those elements that specifically pertain to the diagnosis and management of POAG. Important diagnostic testing includes central corneal thickness measurement, visual field evaluation, and imaging of the optic nerve head, RNFL and macula. The relative risks and benefits of treatment with medications, laser therapy, or incisional surgery should be discussed with the patient prior to its initiation. The adequacy of treatment is determined during follow-up by regular assessment of the optic nerve appearance and quantitative evaluation with visual field testing and imaging of the optic nerve head, RNFL and macula.

Ocular Perfusion Pressure and the Risk of Open-Angle Glaucoma: Systematic Review and Meta-analysis

Low ocular perfusion pressure (OPP) has been proposed as an important risk factor for glaucoma development and progression, but controversy still exists between studies. Therefore, we conducted a systematic review and meta-analysis to analyze the association between OPP and open-angle glaucoma (OAG). Studies were identified by searching PubMed and EMBASE databases. The pooled absolute and standardised mean difference in OPP between OAG patients and controls were evaluated using the random-effects model. Meta-regression analysis was conducted to investigate the factors associated with OPP difference between OAG patients and controls. A total of 43 studies were identified including 3,009 OAG patients, 369 patients with ocular hypertension, and 29,502 controls. The pooled absolute mean difference in OPP between OAG patients and controls was −2.52 mmHg (95% CI −4.06 to −0.98), meaning significantly lower OPP in OAG patients (P = 0.001). Subgroup analyses showed that OAG patients with baseline IOP > 21 mmHg (P = 0.019) and ocular hypertension patients also had significantly lower OPP than controls (P < 0.001), but such difference in OPP was not significant between OAG patients with baseline IOP of ≤21 mmHg and controls (P = 0.996). In conclusion, although no causal relationship was proven in the present study, our findings suggest that in patients with high baseline IOP, who already have a higher risk of glaucoma, low OPP might be another risk factor.

Intra-Subject Variability and Diurnal Cycle of Ocular Perfusion Pressure as Characterized by Continuous Telemetry in Nonhuman Primates.

PurposeTo characterize ocular perfusion pressure (OPP) fluctuations with continuous telemetry over 24-hour periods across multiple days in nonhuman primates (NHPs) to test the hypotheses that OPP differs among NHPs and that the diurnal cycle of OPP is characterized by low OPP during sleep.MethodsWe have developed and validated two implantable radiotelemetry systems that allow continuous measurement of intraocular pressure (IOP), arterial blood pressure (BP), and OPP up to 500 Hz. OPP was measured unilaterally in 12 male NHPs for periods of 38 to 412 days. IOP transducers were calibrated directly via anterior chamber manometry, and OPP was calculated continuously as central retinal artery BP minus IOP. OPP data were corrected for signal drift between calibrations and averaged hourly.ResultsOPP varied widely among animals, with daily averages ranging from ∼47 to 65 mm Hg. In eight of 12 NHPs, OPP was significantly lower during sleep compared to waking hours. In three animals, the diurnal cycle was reversed and OPP was significantly higher during sleep (P < 0.05), and one NHP showed no diurnal cycle. Day-to-day OPP variability within NHPs was the largest source of overall OPP variability, even larger than the differences between NHPs. Average daily OPP showed an unexplained ∼32-day cyclic pattern in most NHPs.ConclusionsAverage OPP varied widely and exhibited differing diurnal cycles in NHPs, a finding that matches those of prior patient studies and indicates that OPP studies in the NHP model are appropriate. Infrequent snapshot measurements of either IOP or BP are insufficient to capture true IOP, BP, and OPP and their fluctuations.

Circadian Rhythm and Glaucoma: What do We Know?

The current understanding of circadian regulation disorders and their involvement in glaucoma pathophysiology are poorly understood, yet they may have a substantial impact on the onset and progression of glaucoma. Herein, we review and summarize all the available literature on circadian rhythm disorder and glaucoma to uncover the impact on glaucoma risk, and we highlight future research and potential novel targets for glaucoma management. A review of the relevant literature was performed through PubMed through August 1, 2019. Within a normal circadian rhythm, intraocular pressure (IOP) peaks at night, whereas blood pressure (BP) troughs at night. High nocturnal IOP coupled with low nocturnal systemic BP results in low ocular perfusion pressure and potential for unobserved damage to retinal tissues and the optic nerve. Circadian-related melatonin and sleep disorders also result in changes in IOP and ocular perfusion pressure that lead to the progression of glaucoma. In addition, impaired perception of light input due to glaucoma can subsequently lead to abnormal serum levels of melatonin, resulting in circadian rhythm misalignment. This disruption of the circadian rhythm also contributes to sleep and mood disorders, common in individuals with glaucoma. As regards treatment, glaucoma medications that lower nocturnal IOP without influencing nocturnal BP or diminishing circadian variation seem most effective. Glaucoma progression is influenced by multiple physiological factors regulated by the circadian rhythm. Progression of the disease may also cause physiological changes that lead to circadian-related issues. Further research is warranted on the diurnal cycle, melatonin-mediated processes, and their influence on glaucoma management.

Relationship between optical perfusion pressure and systemic blood pressure on glaucoma: Case-control study.

AIM:To investigate the relationship between blood pressure (BP), ocular perfusion pressure (OPP), intraocular pressure (IOP) and open angle glaucoma (OAG) in Primary Open Angle Glaucoma (POAG) patients and normal population.DESIGN:Cross-sectional observation study.MATERIALS AND METHODS:Hospital-based, case control cross-sectional study conducted on 150 patients, of which 75 people were included in the control group and 75 people in the glaucoma group. The diagnosis of cases was based on disc evaluation, gonioscopy, perimetry and applanation tonometry. Systolic and diastolic blood pressure (SBP and DBP) was measured with a Mercury Sphygmomanometer. Mean ocular perfusion pressure (MOPP) = ⅔ (mean arterial pressure − IOP), where mean arterial pressure (MAP) = DBP + ⅓ (SBP − DBP), systolic perfusion pressure (SPP) = SBP – IOP and diastolic perfusion pressure (DPP) = DBP − IOP was calculated.RESULTS:DBP, OPP, SPP and DPP showed positive association with POAG. There is positive correlation between IOP and SBP, DBP and there is a negative correlation between IOP, OPP, SPP and DPP. Lower OPP was strongly associated with an increased risk for POAG, with a relative risk of 6.27 and the odds ratio of 0.075 for those with OPP less than 50 mmHg. Similarly, a low DPP less than 55 mmHg were also associated with increased risk for POAG with relative risk of 5.3 and the odds ratio of 0.020.CONCLUSION:Low MOPP and low DPP show strong association with increased prevalence of POAG and are independent risk factors for OAG.

The impact of laparoscopic surgery in Trendelenburg position on intraocular pressure

Background Patients′ intraocular pressure (IOP) significantly increase during laparoscopic surgery in Trendelenburg position, and the resulting intraoperative intraocular hypertension may be related to postoperative visual loss (POVL). Objective To review the impact of laparoscopic surgery in Trendelenburg position on IOP to let the practitioners aware of the association between intraocular hypertension and POVL. Content One of the major causes for POVL is ischemia in optic nerve following reduction of ocular perfusion pressure (OPP) because of the increase of IOP. Animal studies prove that persistently increased IOP leads to damages in the retina. Patients often receive the laparoscopic surgery in Trendelenburg position, and low OPP and high IOP are commonly seen in this situation. In addition to the body position, the increase of IOP can also be a consequence of hypercapnia following CO2 inflation in the abdominal cavity, and may be affected by anesthetics, duration of the surgery, blood pressure, obesity and gender, etc. Several procedures have been performed to alleviate the increase of IOP, such as, intermittent shift the Trendelenburg position into supine position and intraoperative pharmacological intervention. Trend POVL is rarely seen in laparoscopic surgery, but severely compromises patient′s life quality if happens. Cautions should be taken to carefully monitor IOP in the patients with risk factors for POVL during laparoscopic surgery in the Trendelenburg position. Key words: Intraocular pressure; Laparoscopic surgery; Trendelenburg position

A comparative analysis of the postural and diurnal ocular perfusion pressure of young healthy individuals of different ethnicities

Purpose: Ocular perfusion pressure (OPP) regulates the flow of blood to the optic nerve and is determined by the interaction between intraocular pressure (IOP) and blood pressure (BP). Low OPP increases the incidence of primary open-angle glaucoma (POAG). The aim is to compare the diurnal (i.e. morning vs. afternoon) and postural (i.e. seated vs. supine) OPP in healthy individuals from different ethnicities aged between 18 and 30 years. Methodology: Averaged IOP and BP measurements were obtained with an ICare rebound tonometer and an automated sphygmomanometer, respectively. Measurements were taken in the morning and afternoon, in the supine and seated positions in healthy young adults: Africans ( n = 10), white people ( n = 10), mixed-race people ( n = 10) and Indians ( n = 10). Results: The whole sample ( N = 40) displayed a statistically significant reduction in postural and diurnal OPP both in the supine position and in the morning, respectively. A comparative analysis revealed that Africans displayed statistically significant reduction in OPP when compared to other ethnicities. Discussion: A change in posture to the supine position has a greater impact on the reduction of OPP when compared to diurnal changes. Africans displayed clinically significant reduction in OPP which may increase the incidence of POAG in this ethnicity at an early age. Conclusion: Our findings question whether OPP should be considered as a biomarker in the dark-skinned individuals. An evaluation of BP and IOP in the supine position is recommended for all patients to obtain more conclusive readings.

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

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). Cross-sectional observational study. 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. 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. Factors associated with IPFS rather than INS. 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. The presence of MvD in the parapapillary choroid was a strong predictor for IPFS.