Potential role for Ginkgo biloba extract in the treatment of glaucoma

Effect of ginkgo biloba extract on macula and peripapillary perfusion examined using optical coherence tomography angiography

OBJECTIVE

To evaluate the effect of ginkgo biloba extract (GBE) on optical coherence tomography angiography (OCT-A) macula and peripapillary perfusion parameters among patients with treated early-to-moderate primary open-angle glaucoma.

DESIGN

Clinical trial.

PARTICIPANTS

Seventeen patients with early-to-moderate (≥10 dB MD) primary open-angle glaucoma were matched to 17 control patients based on age, sex, and glaucoma status. A total sample size of 34 was determined for effect size 0.5, alpha 0.05, power 0.81, and critical t = 2.03. Normality was confirmed using the Kolmogorov-Smirnov and Shapiro-Wilk tests.

METHODS

The intervention was 120 mg oral GBE twice daily for 4 months. OCT-A scans (15° × 15°) of the macula and peripapillary retina were acquired, two-dimensional projection slab images of the superficial vascular complex were exported, and image analysis was performed. Student's t test was used to compare perfusion density between groups, and between baseline and follow-up for each group. The main outcomes were perfusion density of the superficial vascular complex of the macula and the peripapillary region.

RESULTS

Comparison between baseline and 4 months' supplementation with GBE revealed no significant change in perfusion density in the macular area, 0.32 (0.04) versus 0.30 (0.04); p = 0.17, and was significantly lower in the peripapillary area, 0.44 (0.05) versus 0.42 (0.04); p = 0.02. No differences were observed in the control group.

CONCLUSION

Four-month supplementation with GBE did not result in clinically significant improvement in macula or peripapillary perfusion density in patients with treated early-to-moderate primary open-angle glaucoma. Larger studies are needed to confirm an absence of neuroprotective effects of GBE.

Advances in Neuroprotection in Glaucoma: Pharmacological Strategies and Emerging Technologies

Glaucoma is a major global health concern and the leading cause of irreversible blindness worldwide, characterized by the progressive degeneration of retinal ganglion cells (RGCs) and their axons. This review focuses on the need for neuroprotective strategies in glaucoma management, addressing the limitations of current treatments that primarily target intraocular pressure (IOP) reduction. Despite effective IOP management, many patients continue to experience RGC degeneration, leading to irreversible blindness. This review provides an overview of both pharmacological interventions and emerging technologies aimed at directly protecting RGCs and the optic nerve, independent of IOP reduction. Pharmacological agents such as brimonidine, neurotrophic factors, memantine, Ginkgo biloba extract, citicoline, nicotinamide, insulin, and resveratrol show promise in preclinical and early clinical studies for their neuroprotective properties. Emerging technologies, including stem cell therapy, gene therapy, mitochondrial-targeted therapies, and nanotechnologies, offer innovative approaches for neuroprotection and regeneration of damaged RGCs. While these interventions hold significant potential, further research and clinical trials are necessary to confirm their efficacy and establish their role in clinical practice. This review highlights the multifaceted nature of neuroprotection in glaucoma, aiming to guide future research and clinical practice toward more effective management of glaucoma-induced neurodegeneration.

Herbal and Natural Treatments for the Management of the Glaucoma: An Update

Glaucoma causes the degeneration of the retinal ganglion cells (RGCs) and their axons, inducing a tissue reshaping that affects both the retina and the optic nerve head. Glaucoma care especially focuses on reducing intraocular pressure, a significant risk factor for progressive damage to the optic nerve. The use of natural treatments, such as herbs, vitamins, and minerals, is becoming increasingly popular today. While plants are a rich source of novel biologically active compounds, only a small percentage of them have been phytochemically examined and evaluated for their medicinal potential. It is necessary for eye care professionals to inform their glaucoma patients about the therapy, protection, and efficacy of commonly used herbal medicines, considering the widespread use of herbal medicines. The purpose of this review is to examine evidence related to the most widely used herbal medicines for the management and treatment of glaucoma, to better understand the potential benefits of these natural compounds as supplementary therapy.

Neuroprotection in Glaucoma: Basic Aspects and Clinical Relevance

Glaucoma is a neurodegenerative disease that affects primarily the retinal ganglion cells (RGCs). Increased intraocular pressure (IOP) is one of the major risk factors for glaucoma. The mainstay of current glaucoma therapy is limited to lowering IOP; however, controlling IOP in certain patients can be futile in slowing disease progression. The understanding of potential biomolecular processes that occur in glaucomatous degeneration allows for the development of glaucoma treatments that modulate the death of RGCs. Neuroprotection is the modification of RGCs and the microenvironment of neurons to promote neuron survival and function. Numerous studies have revealed effective neuroprotection modalities in animal models of glaucoma; nevertheless, clinical translation remains a major challenge. In this review, we select the most clinically relevant treatment strategies, summarize preclinical and clinical data as well as recent therapeutic advances in IOP-independent neuroprotection research, and discuss the feasibility and hurdles of each therapeutic approach based on possible pathogenic mechanisms. We also summarize the potential therapeutic mechanisms of various agents in neuroprotection related to glutamate excitotoxicity.

Nutritional supplementation in the prevention and treatment of Glaucoma

Glaucoma is a chronic optic neuropathy that creates a significant burden on public health. Oxidative stress is hypothesised to play a role to glaucoma progression, and its reduction is being analysed as a therapeutic target. Dietary antioxidants play a crucial role in helping provide insight into this hypothesis. We reviewed 71 trials, interventional, I -vivo and I -vitro, including 11 randomised controlled trials, to determine if adjunctive nutritional supplementation could lead to a reduction in oxidative stress and prevent glaucomatous progression. Many laboratory findings show that vitamins and natural compounds contain an abundance of intrinsic antioxidative, neuroprotective and vasoprotective properties that show promise in the treatment and prevention of glaucoma. Although there is encouraging early evidence, most clincial findings are inconclusive. The group of B vitamins appear to have the greatest amount of evidence. Other compounds such as flavonoids, carotenoids, curcumin, saffron, CoQ10, Ggngko Biloba and Resveratrol however warrant further investigation in glaucoma patients. Studies of these antioxidants and other nutrients could create adjunctive or alternative preventative and treatment modalities for glaucoma to those currently available.

Ginkgo Biloba Extract in Ophthalmic and Systemic Disease, With a Focus on Normal-Tension Glaucoma

Glaucoma is a neurodegenerative eye disease that results in retinal ganglion cell loss and ultimately loss of vision. Elevated intraocular pressure (IOP) is the most common known risk factor for retinal ganglion cell damage and visual field loss, and the only modifiable risk factor proven to reduce the development and progression of glaucoma. This has greatly influenced our approach and assessment in terms of diagnosis and treatment. However, as many as ≥50% of patients with progressive vision loss from primary open angle glaucoma without IOP elevation (≤22 mm Hg) have been reported in the United States and Canada; 90% in Japan and 80% in Korea. Extensive research is currently underway to identify the etiology of risk factors for glaucoma other than or in addition to elevated IOP (so-called "normal-tension" glaucoma; NTG) and use this knowledge to expand available treatment options. Currently, Food and Drug Administration-approved medications for glaucoma exclusively target elevated IOP, suggesting the need for additional approaches to treatment options beyond the current scope as the definition of glaucoma changes to encompass cellular and molecular mechanisms. This review focuses on alternative medical approaches, specifically Ginkgo Biloba extract, as a potential treatment option for normal-tension glaucoma.

Ginkgo biloba L. Leaf Extract Protects HepG2 Cells Against Paraquat-Induced Oxidative DNA Damage

Ginkgo biloba L. leaf extracts and herbal infusions are used worldwide due to the health benefits that are attributed to its use, including anti-neoplastic, anti-aging, neuro-protection, antioxidant and others. The aim of this study was to evaluate the effect of an aqueous Ginkgo biloba extract on HepG2 cell viability, genotoxicity and DNA protection against paraquat-induced oxidative damage. Exposure to paraquat (PQ), over 24 h incubation at 1.0 and 1.5 µM, did not significantly reduce cell viability but induced concentration and time-dependent oxidative DNA damage. Ginkgo biloba leaf extract produced dose-dependent cytotoxicity (IC₅₀ = 540.8 ± 40.5 µg/mL at 24 h exposure), and short incubations (1 h) produced basal and oxidative DNA damage (>750 and 1500 µg/mL, respectively). However, lower concentrations (e.g., 75 µg/mL) of Ginkgo biloba leaf extract were not cytotoxic and reduced basal DNA damage, indicating a protective effect at incubations up to 4 h. On the other hand, longer incubations (24 h) induced oxidative DNA damage. Co-incubation of HepG2 cells for 4 h, with G. biloba leaf extract (75 µg/mL) and PQ (1.0 or 1.5 µM) significantly reduced PQ-induced oxidative DNA damage. In conclusion, the consumption of Ginkgo biloba leaf extract for long periods at high doses/concentrations is potentially toxic; however, low doses protect the cells against basal oxidative damage and against environmentally derived toxicants that induce oxidative DNA damage.

Dietary Antioxidants, Macular Pigment, and Glaucomatous Neurodegeneration: A Review of the Evidence

Primary open-angle glaucoma (POAG) is a leading cause of irreversible blindness worldwide, and the prevalence is projected to increase to 112 million worldwide by 2040. Intraocular pressure is currently the only proven modifiable risk factor to treat POAG, but recent evidence suggests a link between antioxidant levels and risk for prevalent glaucoma. Studies have found that antioxidant levels are lower in the serum and aqueous humor of glaucoma patients. In this review, we provide a brief overview of the evidence linking oxidative stress to glaucomatous pathology, followed by an in-depth discussion of epidemiological studies and clinical trials of antioxidant consumption and glaucomatous visual field loss. Lastly, we highlight a possible role for antioxidant carotenoids lutein and zeaxanthin, which accumulate in the retina to form macular pigment, as evidence has emerged supporting an association between macular pigment levels and age-related eye disease, including glaucoma. We conclude that the evidence base is inconsistent in showing causal links between dietary antioxidants and glaucoma risk, and that prospective studies are needed to further investigate the possible relationship between macular pigment levels and glaucoma risk specifically.

Health Benefits of Polyphenols and Carotenoids in Age-Related Eye Diseases

Oxidative stress and inflammation play a critical role in the initiation and progression of age-related ocular abnormalities as cataract, glaucoma, diabetic retinopathy, and macular degeneration. Therefore, phytochemicals with proven antioxidant and anti-inflammatory activities, such as carotenoids and polyphenols, could be of benefit in these diseases. We searched PubMed and Web of Science databases for original studies investigating the benefits of different carotenoids and polyphenols in age-related ophthalmic diseases. Our results showed that several polyphenols (such as anthocyanins, Ginkgo biloba, quercetin, and resveratrol) and carotenoids (such as lutein, zeaxanthin, and mezoxanthin) have shown significant preventive and therapeutic benefits against the aforementioned conditions. The involved mechanisms in these findings include mitigating the production of reactive oxygen species, inhibiting the tumor necrosis factor-α and vascular endothelial growth factor pathways, suppressing p53-dependent apoptosis, and suppressing the production of inflammatory markers, such as interleukin- (IL-) 8, IL-6, IL-1a, and endothelial leucocyte adhesion molecule-1. Consumption of products containing these phytochemicals may be protective against these diseases; however, adequate human data are lacking. This review discusses the role and mechanisms of polyphenols and carotenoids and their possible synergistic effects on the prevention and treatment of age-related eye diseases that are induced or augmented by oxidative stress and inflammation.

Substances of Interest That Support Glaucoma Therapy

Glaucoma is a multifactorial disease in which pro-apoptotic signals are directed to retinal ganglion cells. During this disease the conventional outflow pathway becomes malfunctioning. Aqueous humour builds up in the anterior chamber, leading to increased intraocular pressure. Both of these events are related to functional impairment. The knowledge of molecular mechanisms allows us to better understand the usefulness of substances that can support anti-glaucoma therapy. The goal of glaucoma therapy is not simply to lower intraocular pressure; it should also be to facilitate the survival of retinal ganglion cells, as these constitute the real target tissue in this disease, in which the visual pathway is progressively compromised. Indeed, an endothelial dysfunction syndrome affecting the endothelial cells of the trabecular meshwork occurs in both normal-tension glaucoma and high-tension glaucoma. Some substances, such as polyunsaturated fatty acids, can counteract the damage due to the molecular mechanisms - whether ischemic, oxidative, inflammatory or other - that underlie the pathogenesis of glaucoma. In this review, we consider some molecules, such as polyphenols, that can contribute, not only theoretically, to neuroprotection but which are also able to counteract the metabolic pathways that lead to glaucomatous damage. Ginkgo biloba extract, for instance, improves the blood supply to peripheral districts, including the optic nerve and retina and exerts a neuro-protective action by inhibiting apoptosis. Polyunsaturated fatty acids can protect the endothelium and polyphenols exert an anti-inflammatory action through the down-regulation of cytokines such as TNF-α and IL-6. All these substances can aid anti-glaucoma therapy by providing metabolic support for the cells involved in glaucomatous injury. Indeed, it is known that the food we eat is able to change our gene expression.

Citicoline and Retinal Ganglion Cells: Effects on Morphology and Function

BACKGROUND

Retinal ganglion cells (RGCs) are the nervous retinal elements which connect the visual receptors to the brain forming the nervous visual system. Functional and/or morphological involvement of RGCs occurs in several ocular and neurological disorders and therefore these cells are targeted in neuroprotective strategies. Cytidine 5-diphosphocholine or Citicoline is an endogenous compound that acts in the biosynthesis of phospholipids of cell membranes and increases neurotransmitters' levels in the Central Nervous System. Experimental studies suggested the neuromodulator effect and the protective role of Citicoline on RGCs. This review aims to present evidence of the effects of Citicoline in experimental models of RGCs degeneration and in human neurodegenerative disorders involving RGCs.

METHODS

All published papers containing experimental or clinical studies about the effects of Citicoline on RGCs morphology and function were reviewed.

RESULTS

In rodent retinal cultures and animal models, Citicoline induces antiapoptotic effects, increases the dopamine retinal level, and counteracts retinal nerve fibers layer thinning. Human studies in neurodegenerative visual pathologies such as glaucoma or non-arteritic ischemic neuropathy showed a reduction of the RGCs impairment after Citicoline administration. By reducing the RGCs' dysfunction, a better neural conduction along the post-retinal visual pathways with an improvement of the visual field defects was observed.

CONCLUSION

Citicoline, with a solid history of experimental and clinical studies, could be considered a very promising molecule for neuroprotective strategies in those pathologies (i.e. Glaucoma) in which morpho-functional changes of RGCc occurs.

Traditional medicinal plants used for respiratory disorders in Pakistan: a review of the ethno-medicinal and pharmacological evidence

Respiratory disorders are a common cause of malady and demise in Pakistan due to its remoteness, cold and harsh climatic conditions as well as scarce health care facilities. The people rely upon the indigenous plant resources to cure various respiratory disorders. The primary objective of this review was to assemble all available ethno-medicinal data of plants used for respiratory disorders in Pakistan. Pharmacological activity of these plants (based upon published scientific research), distribution, diversity, use, preparation methods, economical value, conservation status and various available herbal products of some plants have also been explored. This study scrutinized various electronic databases for the literature on medicinal plants used in Pakistan to treat respiratory disorders. A total of 384 species belonging to 85 families used to treat respiratory disorders in Pakistan has been documented. Cough was the disorder treated by the highest number of species (214) followed by asthma (150), cold (57) and bronchitis (56). Most of the plants belongs to Asteraceae (32) and Solanaceae family (32) followed by moraceae (17), Poaceae (13), and Amaranthaceae (13) with their habit mostly of herb (219) followed by Shrub (112) and tree (69). Traditional healers in the region mostly prepare ethno medicinal recipes from leaves (24%) and roots (11%) in the form of decoction. Among the reported conservation status of 51 plant species, 5 were endangered, 1 critically endangered, 11 vulnerable, 14 rare, 16 least concern, 3 infrequent and 1 near threatened. We found only 53 plants on which pharmacological studies were conducted and 17 plants being used in herbal products available commercially for respiratory disorders. We showed the diversity and importance of medicinal plants used to treat respiratory disorders in the traditional health care system of Pakistan. As such disorders are still causing several deaths each year, it is of the utmost importance to conduct phytochemical and pharmacological studies on the most promising species. It is also crucial to increase access to traditional medicine, especially in rural areas. Threatened species need special attention for traditional herbal medicine to be exploited sustainably.

Phytochemical Properties and Heavy Metal Contents of Commonly Consumed Alcoholic Beverages Flavouredwith Herbal Extract in Nigeria

There is proliferation of alcoholic beverages flavoured with herbal-extracts that are perceived to have medicinal values. Information on the phytochemical and heavy metal contents of these products is scarce. This study assessed the phytochemical properties and heavy metal contents of herbal-extract flavoured alcoholic beverages in major motor parks in Ibadan, Nigeria. The phytochemical properties of the beverages were determined in triplicate using standard methods, while the heavy metal contents were assessed while using atomic absorption spectrophotometry. Data were analyzed using descriptive statistics, and means were compared using ANOVA at p < 0.05.The pH range of the beverages was 3.28–6.57 and the alcohol content was 34.0–51.5%. Detected major phytochemicals and concentration ranges were phytic acid (0.72–2.37 mg/g), alkaloids (0.42–4.11 mg/g), flavonoids (0.22–3.64 mg rutin equivalents/g), total phenols (1.13–3.66 mg gallic acid equivalents/g), anthraquinones (0.74–1.93 mg/g),and triterpenoids (0.74–1.93 mg/g). The heavy metal contents were Pb (2.13–4.70 mg/L), Cd (0.06–0.07 mg/L), Co (0.12–0.23 mg/L), Zn (0.14–0.40 mg/L), and Fe (0.72–4.22 mg/L); only Pb and Cd were above the World Health Organization (WHO) limits of 0.01 mg/L and 0.03 mg/L in water, respectively. The herbal-extract flavoured alcoholic beverages contain beneficial phytochemicals and traces of heavy metals. Safety awareness of these products for improved consumers’ health would be of public health importance.

Therapeutic potential of valproic acid in advanced glaucoma: A pilot study

Purpose

Oral valproic acid (VPA) used as an anticonvulsant has been shown to improve contrast threshold sensitivities in patients receiving it on long-term. This study aimed to evaluate the efficacy of oral VPA in improving visual function in eyes with advanced stage glaucoma.

Methods

In this prospective randomized study, 31 patients (n = 31 eyes) with advanced stage glaucoma (with an intraocular pressure <16 mmHg) in at least one eye received oral VPA 500 mg once a day for 3 months and 33 patients (n = 33 eyes) continued on glaucoma therapy. Patients were followed up at 3 and 12 months (to evaluate the legacy effect of the drug). Blood VPA concentrations were measured at 3 months. Following parameters were assessed at baseline, 3 months and 12 months: log of the minimum angle of resolution (LogMAR) visual acuity, mean deviation on visual fields, and multifocal electroretinogram (ERG).

Results

Median LogMar visual acuity in the VPA group improved from 0.3 at baseline to 0.18 and 0.18 at 3 and 12 months, respectively (P < 0.01). In comparison, the median visual acuity in control group at baseline was 0.18 and showed neither worsening nor improvement over 3 and 12 months (P = 0.56). The improvement in VPA group was significant compared to the control group (P < 0.01; Wilcoxon Signed-rank test). An improvement in one line was experienced in 11 out of 31 eyes in the VPA group compared to 1 out of 33 eyes among controls (P = 0.003). No significant improvement was noted in the mean deviation, and the multifocal ERG (Latency and amplitudes) in the VPA-treated patients. The average blood VPA concentration measured at 3 months of therapy was 26 ± 8.9 μg/ml (range 8-55 μg/ml) which is much lower than that achieved during anticonvulsant therapy. None of the patients complained of any adverse effects that required stopping VPA therapy.

Conclusion

A 3 months oral VPA therapy results in some improvement in visual acuity in a subgroup of eyes with advanced glaucoma and the effect was seen to persist 9 months after the drug was stopped.

Rational Basis for Nutraceuticals in the Treatment of Glaucoma

BACKGROUND

Glaucoma, the second leading cause of blindness worldwide, is a chronic optic neuropathy characterized by progressive retinal ganglion cell (RGC) axons degeneration and death. Primary open-angle glaucoma (OAG), the most common type, is often associated with increased intraocular pressure (IOP), however other factors have been recognized to partecipate to the patogenesis of the optic neuropathy. IOP-independent mechanisms that contribute to the glaucoma-related neurodegeneration include oxidative stress, excitotoxicity, neuroinflammation, and impaired ocular blood flow. The involvement of several and diverse factors is one of the reasons for the progression of glaucoma observed even under efficient IOP control with the currently available drugs.

METHODS

Current research and online content related to the potential of nutritional supplements for limiting retinal damage and improving RGC survival is reviewed.

RESULTS

Recent studies have suggested a link between dietary factors and glaucoma risk. Particularly, some nutrients have proven capable of lowering IOP, increase circulation to the optic nerve, modulate excitotoxicity and promote RGC survival. However, the lack of clinical trials limit their current therapeutic use. The appropriate use of nutraceuticals that may be able to modify the risk of glaucoma may provide insight into glaucoma pathogenesis and decrease the need for, and therefore the side effects from, conventional therapies.

CONCLUSION

The effects of nutrients with anti-oxidant and neuroprotective properties are of great interest and nutraceuticals may offer some therapeutic potential although a further rigorous evaluation of nutraceuticals in the treatment of glaucoma is needed to determine their safety and efficacy.

Pharmacokinetic and ocular microdialysis study of oral ginkgo biloba extract in rabbits by UPLC-MS/MS determination

Objectives

The purpose of this work was to determine and investigate the absorption of ginkgo terpenoids (GT) in plasma and aqueous humour after oral administration of ginkgo biloba extract (GBE) by UPLC-MS/MS method.

Methods

The UPLC-MS/MS determination of GT employed the multiple reaction monitoring mode using an electrospray negative ionization. The rabbits were orally administered the suspension of GBE at a dose of 500 mg/kg. Serial plasma and dialysate samples were collected at the corresponding time and then analysed by UPLC-MS/MS.

Key findings

In plasma, the mean AUC from 0 to 48 h was 14.12, 12.59, 23.75, 1.51 h μg/ml for GLJ and 5.34 h μg/ml for GLA, GLB, GLC, GLJ and BLL, respectively. In aqueous humour, the five ginkgo terpenoids have been detected. Compared with the other four GT, BLL has better absorption in the eyes.

Conclusions

A selective and reproducible UPLC-MS/MS method was developed and validated to determine and investigate the absorption of ginkgo terpenoids in plasma and aqueous humour of rabbits after oral administration of GBE. The main five ginkgo terpenoids could be absorbed into eyes.

Neuroprotection in Glaucoma

Glaucoma is a degenerative optic neuropathy characterized by retinal ganglion cell (RGC) loss and visual field defects. It is known that in some glaucoma patients, death of RGCs continues despite intraocular pressure (IOP) reduction. Neuroprotection in the field of glaucoma is defined as any treatment, independent of IOP reduction, which prevents RGC death. Glutamate antagonists, ginkgo biloba extract, neurotrophic factors, antioxidants, calcium channel blockers, brimonidine, glaucoma medications with blood regulatory effect and nitric oxide synthase inhibitors are among compounds with possible neuroprotective activity in preclinical studies. A few agents (such as brimonidine or memantine) with neuroprotective effects in experimental studies have advanced to clinical trials; however the results of clinical trials for these agents have not been conclusive. Nevertheless, lack of compelling clinical evidence has not prevented the off-label use of some of these compounds in glaucoma practice. Stem cell transplantation has been reported to halt experimental neurodegenerative disease processes in the absence of cell replacement. It has been hypothesized that transplantation of some types of stem cells activates multiple neuroprotective pathways via secretion of various factors. The advantage of this approach is a prolonged and targeted effect. Important concerns in this field include the secretion of unwanted harmful mediators, graft survival issues and tumorigenesis. Neuroprotection in glaucoma, pharmacologically or by stem cell transplantation, is an interesting subject waiting for broad and multidisciplinary collaborative studies to better clarify its role in clinical practice.

[Current aspects on the management of normal tension glaucoma]

In a considerable proportion of glaucoma patients (25-50 %) the intraocular pressure (IOP) is not elevated higher than 22 mmHg at first diagnosis and during subsequent follow-up controls. Although the IOP level remains in the low range < 22 mmHg, progression of glaucoma can still occur. A multitude of different factors are assumed to be involved in glaucoma progression, such as very low nocturnal diastolic blood pressure values, a low mean ocular perfusion pressure, extensive fluctuations in perfusion (e.g. in cases of vascular dysregulation), an increased vulnerability of the optic nerve support structures, an increased translaminar pressure gradient and various underlying systemic diseases. The most important evidence-based aspect of treatment in normal tension glaucoma is pharmaceutical or surgical reduction of the IOP by 30 % or more in comparison to the initial pressure level. Vascular and neuroprotective concepts of treatment for normal tension glaucoma have been strongly advocated and the object of experimental and clinical studies. As yet a clear clinical benefit has not been proven by large prospective randomized studies.

Natural compounds and retinal ganglion cell neuroprotection

Glaucoma, the second leading cause of blindness in the world, is a chronic optic neuropathy often associated with increased intraocular pressure and characterized by progressive retinal ganglion cell (RGC) axons degeneration and death leading to typical optic nerve head damage and distinctive visual field defects. Although the pathogenesis of glaucoma is still largely unknown, it is hypothesized that RCGs become damaged through various insults/mechanisms, including ischemia, oxidative stress, excitotoxicity, defective axonal transport, trophic factor withdrawal, and neuroinflammation. In this review, we summarize the potential benefits of several natural compounds for RGCs neuroprotection.

Preserving neural retina through re-emerging herbal interventions

Eye related diseases such as glaucoma, diabetic retinopathy, cataract, conjunctivitis are very common worldwide. With the current scenario India will be among the top five countries in the number of glaucoma cases. Limited discovery of successful drugs for the treatment of such diseases led scientists to look towards the use of conventional sources for treatment. Herbal extracts from Ayurveda have remained an important part of treatment regime in many parts of world even today. For this reason, local herbs possessing curative properties are still being used by local inhabitants due to its anti-inflammatory and antioxidant properties. Because retinal damage involves alterations in oxidative enzymes, blood flow changes and increase in apoptotic signals, herbal extracts are being tested for their ability to moderate antioxidant machinery and trigger neuroprotective pathways. The present review summarizes some of such herbal extracts which have been tested for their neuroprotective role in eye related diseases. The active components that exert neuroprotective effects have also been discussed along with possible mechanisms of action.

Effect of Ginkgo biloba extract on visual field progression in normal tension glaucoma

PURPOSE

To evaluate the long-term effect of Ginkgo biloba extract (GBE) on progression of visual field (VF) defects in patients with normal tension glaucoma (NTG).

METHODS

Forty-two eyes of 42 patients with treated NTG who received 80 mg GBE 2 times daily and who had at least 5 VF tests using the Humphrey Visual Field Analyzer for more than a 4-year period before and after GBE treatment were evaluated in this retrospective study. We evaluated the change of progression rate using mean deviation (MD), pattern standard deviation (PSD), and visual field index (VFI) after GBE treatment. The time course of mean total deviation in 10 zones corresponding to the glaucoma hemifield test was analyzed using a linear mixed effects model with unequal random effect variances.

RESULTS

The mean follow-up period was 12.3 years. The posttherapeutic intraocular pressures before and after GBE treatment were not significantly different (P=0.509 paired t test). Before GBE treatment, the regression coefficients (RCs) of MD, PSD, and VFI change were -0.619 dB/y, 0.626 dB/y, and -2.153%/y, respectively. After GBE treatment, the RCs of MD, PSD, and VFI change improved significantly to -0.379 dB/y, 0.342 dB/y, and -1.212%/y (P <0.001), respectively. In zone 1, the RC of mean total deviation change was significantly increased after GBE administration (P <0.005).

CONCLUSIONS

GBE administration slowed the progression of VF damage in patients with NTG, especially in zone 1 corresponding to the superior central field.

Oxidative stress and its downstream signaling in aging eyes

BACKGROUND

Oxidative stress (OS) and its biomarkers are the biochemical end point of the imbalance between reactive oxygen species (ROS) production and the ability of the antioxidant (AOX) biological systems to fight against oxidative injury.

OBJECTIVE

We reviewed the role of OS and its downstream signaling in aging eyes.

METHODS

A search of the literature and current knowledge on the physiological and pathological mechanisms of OS were revisited in relation to the eyes and the aging process. Most prevalent ocular diseases have been analyzed herein in relation to OS and nutraceutic supplements, such as dry-eye disorders, glaucoma, age-related macular degeneration, and diabetic retinopathy.

RESULTS

Clinical, biochemical, and molecular data from anterior and posterior eye segment diseases point to OS as the common pathogenic mechanism in the majority of these ocular disorders, many of which are pathologies causing visual impairment, blindness, and subsequent loss of life quality. Studies with nutraceutic supplements in aging eye-related pathologies have also been reviewed.

CONCLUSION

OS, nutritional status, and nutraceutic supplements have to be considered within the standards of care of older ophthalmologic patients. OS biomarkers and surrogate end points may help in managing the aging population with ocular diseases.

Effect of ginkgo extract on eye microcirculation in patients with diabetes

The prevalence of Diabetes mellitus has increased around the world in the last decade. Anyone with diabetes is at risk of diabetic eye complications. The aim of the study was to compare effects of standardized Ginkgo biloba (Ginkgo biloba L.) dry extract (Ex.Gb) with the placebo on the microcirculation lesions of the eye in randomized double-blind placebo-controlled trial. 44 patients with type 2 diabetes mellitus were randomized to Ex.Gb 160 mg per day or placebo, and were followed up for nine months. Dose of Ex.Gb was increased to 240 mg in next nine months. Total Antioxidant Status (TAS) of plasma was measured using the Trolox equivalent antioxidant capacity assay. Ophthalmologic examination was performed by the biomicroscopic method. Vascular, intravascular and perivascular alterations were evaluated, and total conjunctival index was calculated. Though the values of the total conjunctival index and its constituent decreased (P<0.05) during the study in Ex.Gb group, there were no significant differences between these parameters as compared with placebo group. Evaluation of plasma TAS showed gradually increment, although insignificant and very small, in Ex.Gb group. The significance of Ex.Gb on development of the alterations of eye microcirculation, especially in elder patients needs to be explored further.

Oxidative stress and potential applications of free radical scavengers in glaucoma

Glaucoma is the leading cause of irreversible blindness in industrialized countries and comprises a group of diseases characterized by progressive optic nerve degeneration. Glaucoma is commonly associated with elevated intraocular pressure due to impaired outflow of aqueous humor resulting from abnormalities within the drainage system of the anterior chamber angle (open-angle glaucoma) or impaired access of aqueous humor to the drainage system (angle-closure glaucoma). Oxidative injury and altered antioxidant defense mechanisms in glaucoma appear to play a role in the pathophysiology of glaucomatous neurodegeneration that is characterized by death of retinal ganglion cells. Oxidative protein modifications occurring in glaucoma serve as immunostimulatory signals and alter neurosupportive and immunoregulatory functions of glial cells. Initiation of the apoptotic cascade observed in glaucomatous retinopathy can involve oxidant mechanisms and different agents have been shown to be neuroprotective. This review focuses on the molecular mechanisms of oxidant injury and summarizes studies that have investigated novel free radical scavengers in the treatment of glaucomatous neurodegeneration.

Ginkgo biloba extract and bilberry anthocyanins improve visual function in patients with normal tension glaucoma

Ginkgo biloba extract (GBE) and anthocyanins are considered beneficial for various vascular diseases. This study was performed to evaluate the effect of GBE and anthocyanins on visual function in patients with normal tension glaucoma (NTG) based on the vascular theory of mechanisms of glaucomatous optic nerve damage. Retrospective analysis was carried out by a chart review of 332 subjects (209 men and 123 women) who were treated with anthocyanins (n=132), GBE (n=103), or no medication (control, n=97). Humphrey Visual Field (HVF) test, logarithm of the minimal angle of resolution best-corrected visual acuity (logMAR BCVA), intraocular pressure, blood pressure, and fasting blood glucose were determined before and after treatment. Complete ocular and systemic examinations were performed. The mean follow-up duration was 23.82±9.84 (range, 12-59) months; the mean anthocyanin treatment duration was 24.32±10.43 (range, 6-53) months, and the mean GBE treatment duration was 23.81±10.36 months (range, 6-59) months. After anthocyanin treatment, the mean BCVA for all eyes improved from 0.16 (±0.34) to 0.11 (±0.18) logMAR units (P=.008), and HVF mean deviation improved from -6.44 (±7.05) to -5.34 (±6.42) (P=.001). After GBE treatment, HVF mean deviation improved from -5.25 (±6.13) to -4.31 (±5.60) (P=.002). A generalized linear model demonstrated that the final BCVA was not affected by demographic differences among the groups. These results suggest that anthocyanins and GBE may be helpful in improving visual function in some individuals with NTG.

Antioxidant activity and protecting health effects of common medicinal plants

Medicinal plants are traditionally used in folk medicine as natural healing remedies with therapeutic effects such as prevention of cardiovascular diseases, inflammation disorders, or reducing the risk of cancer. In addition, pharmacological industry utilizes medicinal plants due to the presence of active chemical substances as agents for drug synthesis. They are valuable also for food and cosmetic industry as additives, due to their preservative effects because of the presence of antioxidants and antimicrobial constituents. To commonly used medicinal plants with antioxidant activity known worldwide belong plants from several families, especially Lamiaceae (rosemary, sage, oregano, marjoram, basil, thyme, mints, balm), Apiaceae (cumin, fennel, caraway), and Zingiberaceae (turmeric, ginger). The antioxidant properties of medicinal plants depend on the plant, its variety, environmental conditions, climatic and seasonal variations, geographical regions of growth, degree of ripeness, growing practices, and many other factors such as postharvest treatment and processing. In addition, composition and concentration of present antioxidants, such as phenolic compounds, are related to antioxidant effect. For appropriate determination of antioxidant capacity, the extraction technique, its conditions, solvent used, and particular assay methodology are important.

Short-term effects of Ginkgo biloba extract on peripapillary retinal blood flow in normal tension glaucoma

Purpose

Based on the vascular theory of glaucoma pathogenesis, we wanted to evaluate the effect of Ginkgo biloba extract (GBE) on peripapillary blood flow in patients with normal tension glaucoma (NTG).

Methods

Thirty patients with NTG were randomly placed in the GBE-treated or control groups. The GBE-treated group received 80 mg GBE orally, twice a day for four weeks, and the control group received a placebo twice a day for four weeks. Complete ocular examinations including visual field, Heidelberg retina flowmeter, and systemic examinations were performed on the first study day and on the day treatment was completed.

Results

After GBE treatment, the mean blood flow, volume, and velocity increased at almost all points, and there was a statistically significant increase in blood flow at almost all points, in comparison to the placebo. Blood volume significantly increased only in the superior nasal and superior temporal neuroretinal rim areas. GBE also significantly increased blood velocity in areas of the inferior temporal neuroretinal rim and superior temporal peripapillary area.

Conclusions

GBE administration appears to have desirable effect on ocular blood flow in NTG patients.

Recent advances in pharmacotherapy of glaucoma

Glaucoma is a slow progressive degeneration of the retinal ganglion cells (RGCs) and the optic nerve axons, leading to irreversible blindness if left undiagnosed and untreated. Although increased intraocular pressure is a major risk factor of glaucoma, other factors include increased glutamate levels, alterations in nitric oxide (NO) metabolism, vascular alterations and oxidative damage caused by reactive oxygen species. Glaucoma is the second leading cause of blindness globally, accounting for 12.3% of the total blindness. Glaucoma has been broadly classified as primary or secondary open-angle or angle-closure glaucoma. The primary goal in management of glaucoma is to prevent the risk factor, especially elevated intraocular pressure (IOP), using medications, laser therapy or conventional surgery. The first-line treatment of glaucoma usually begins with the use of a topical selective or nonselective blocker or a prostaglandin analog. Second-line drugs of choice include alpha-agonists and topical carbonic anhydrase inhibitors. Cholinergic agonists are considered third-line treatment options. When a single therapy is not sufficient to lower the IOP, a combination therapy is indicated. To enhance the patient compliance, drug delivery systems like electronic devices, ocular inserts, tansdermal and mechanical drug delivery systems have been developed. Use of viscoelastic agents in ophthalmic formulations, emulsions and soluble ophthalmic drug inserts (SODI) enhance patience compliance and ocular drug delivery in patients in long-term glaucoma therapy. For patients who do not respond to antiglaucoma medications, laser trabeculoplasty and incisional surgery are recommended. Several nutrients and botanicals hold promise for the treatment of glaucoma, but most studies are preliminary, and larger, controlled studies are required. Future directions for the development of a novel therapy glaucoma may target glutamate inhibition, NMDA receptor blockade, exogenously applied neurotrophins, open channel blockers, antioxidants, protease inhibitors and gene therapy.

Melatonin as a therapeutic tool in ophthalmology: implications for glaucoma and uveitis

Several lines of evidence support the view that increased free radical generation and altered nitric oxide (NO) metabolism play a role in the pathogenesis of highly prevalent ocular diseases, such as glaucoma and uveitis. Data are discussed indicating that melatonin, being an efficient antioxidant that displays antinitridergic properties, has a promising role in the treatment of these ocular dysfunctions. Melatonin synthesis occurs in the eye of most species, and melatonin receptors are localized in different ocular structures. In view of the fact that melatonin lacks significant adverse collateral effects even at high doses, the application of melatonin could potentially protect ocular tissues by effectively scavenging free radicals and excessive amounts of NO generated in the glaucomatous or uveitic eye.

The effect of ginkgo biloba on the rat retinal ganglion cell survival in the optic nerve crush model

PURPOSE

To investigate the effect of ginkgo biloba on the retinal ganglion cell survival in a rat optic nerve crush model.

METHODS

Twenty-four Sprague-Dawley rats were divided randomly into a study group of 12 animals receiving intraperitoneal injections of ginkgo biloba and a control group of 12 animals receiving intraperitoneal saline injections. All injections were performed 1 hr before the optic nerve crush and daily afterwards. For each animal, the right optic nerve was crushed closely behind the globe for 60 seconds using a microclip with 40 g power. The left optic nerve was kept intact. At 23 days after the optic nerve crush, the retinal ganglion cells were labelled retrogradely by injecting 3% fluorogold into both sides of the superior colliculus of the brain. At 4 weeks after the optic nerve crush, the animals were killed. Photographs taken from retinal flat mounts were assessed for the number and density of the retinal ganglion cells.

RESULTS

The survival rate, defined as the ratio of the retinal ganglion cell density in the right eye with the optic nerve crush divided by the retinal ganglion cell density in left eye without an optic nerve trauma, was significantly (p=0.035) higher in the study group with ginkgo biloba than in the control group (60.0+/-6.0% versus 53.5+/-8.0%).

CONCLUSION

The results suggest that intraperitoneal injections of a ginkgo biloba extract given prior to and daily after an experimental and standardized optic nerve crush in rats were associated with a higher survival rate of retinal ganglion cells.

Development of novel drugs for ocular diseases: possibilities for individualized therapy

In clinical ophthalmology, new and old drug regimens are available for the treatment of major eye diseases, including potentially blinding conditions, such as glaucoma, and various macular diseases. In glaucoma, therapeutic treatment mainly deals with control of intraocular pressure at low levels but the clinical courses of patients can be very variable. Very often, specific drug combinations and dosages have to be formulated for individual glaucoma patients. In neovascular age-related macular degeneration, choroidal neovascularization can lead to progressive and irreversible visual impairment if not treated early. In recent years, clinical trials using photodynamic therapy with verteporfin and various anti-VEGF antibodies, such as ranibizumab and bevacizumab, have enhanced the treatment outcomes of neovascular age-related macular degeneration. In diabetic macular edema, intravitreal triamcinolone acetonide and anti-VEGF therapy are effective in some patients. Again, responses to treatment are not uniform in all macular patients. Traditional herbal medicine has long been known to play a role in the practice of personalized formulations in Asia. Potential preventive and therapeutic effects have been claimed in individual eye patients. Meanwhile, advanced technologies in molecular biology have led to identification of genes associated with many eye diseases and development of the concept of individual medicine, in which the genotype of a person can be used as a basis for disease prediction or prophylactic treatments. Moreover, pharmacogenomic studies have demonstrated the association of various genotypes or haplotypes with responses to drug therapies, providing hope for tailormade personalized treatments. The combination of genotypic information with clinical features for the prescription of treatment modes in eye diseases is under vigorous research.

Targeted preventive measures and advanced approaches in personalised treatment of glaucoma neuropathy

Glaucoma is a major cause of vision loss worldwide with nearly 8 million people bilaterally blind from the disease. This number is estimated to increase over the next 10 years. The key to preventing blindness from glaucoma is effective diagnosis and treatment. The classical glaucoma treatment focuses on intraocular pressure (IOP) reduction. Better knowledge of the pathogenesis has opened up additional therapeutical approaches often called non-IOP lowering treatment. Whilst most of these new avenues of treatment are still in the experimental phase, others are already used by some physicians. These new therapeutic approaches allow a more personalised patient treatment. Non-IOP lowering treatment includes improvements of ocular blood flow, particularly blood flow regulation. This can be achieved by improving the regulation of ocular blood flow (improving autoregulation) by drugs such as carbonic anhydrase inhibitors, magnesium or calcium channel blockers. It can also be improved by decreasing blood pressure over-dips. Blood pressure can be increased by an increase in salt intake or in rare cases by treatment with fludrocortisone. Experimentally, glaucomatous optic neuropathy can be prevented by inhibition of astrocyte activation, either by blockage of epidermal growth factor receptor or by counteracting Endothelin. Glaucomatous optic neuropathy can also be prevented by nitric oxide-2 synthase inhibition. Suppression of matrix metalloproteinase-9 inhibits apoptosis of retinal ganglion cells and tissue remodelling. Upregulation of heat shock proteins protects the retinal ganglion cells and the optic nerve head. Reduction of oxidative stress especially at the level of mitochondria also seems to be protective. This can be achieved by gingko, dark chocolate, polyphenolic flavonoids occurring in tea, coffee or red wine and anthocyanosides found in bilberries as well as by ubiquinone and melatonin. This review describes the individual mechanisms which may be targeted by non-IOP lowering treatment based on our pathogenic scheme.

The association between self-reported glaucoma and ginkgo biloba use

PURPOSE

To assess the association between Ginkgo biloba extract (GBE) use and glaucoma.

METHODS

Self-reported data on the past 12 months of GBE use and the presence of glaucoma were obtained from the 2002 National Health Interview Survey, a nationally-representative population-based sample. Crude and adjusted associations between GBE use and glaucoma were estimated.

RESULTS

Those who reported having glaucoma were 26% less likely to report GBE use; however, this was not statistically significant. After adjustment for potentially confounding demographic and medical characteristics, there was no difference in GBE use among those who did and did not report having glaucoma.

CONCLUSIONS

The results of this study fail to support a significant relationship between GBE use over the past 12 months and having glaucoma, though this finding requires replication in a prospective study. Moreover, whether GBE is efficacious in treating glaucoma patients remains an issue for future research.

Is there more to glaucoma treatment than lowering IOP?

Classic glaucoma treatment focuses on intraocular pressure (IOP) reduction. Better knowledge of the pathogenesis of the disease has opened up new therapeutical approaches. Whereas most of these new avenues of treatment are still in the experimental phase, others, such as magnesium, gingko, salt and fludrocortisone, are already used by some physicians. Blood pressure dips can be avoided by intake of salt or fludrocortisone. Vascular regulation can be improved locally by carbonic anhydrase inhibitors, and systemically with magnesium or with low doses of calcium channel blockers. Experimentally, glaucomatous optic neuropathy can be prevented by inhibition of astrocyte activation, either by blockage of epidermal growth factor receptor or by counteracting endothelin. Glaucomatous optic neuropathy can also be prevented by nitric oxide-2 synthase inhibition. Inhibition of matrix metalloproteinase-9 inhibits apoptosis of retinal ganglion cells and tissue remodeling. Upregulation of heat shock proteins protects the retinal ganglion cells and the optic nerve head. Reduction of oxidative stress especially at the level of mitochondria also seems to be protective. This can be achieved by gingko; dark chocolate; polyphenolic flavonoids occurring in tea, coffee, or red wine; anthocyanosides found in bilberries; as well as by ubiquinone and melatonin.

Oxidative stress and glaucoma: injury in the anterior segment of the eye

The perturbation of the pro-oxidant/antioxidant balance can lead to increased oxidative damage, especially when the first line of antioxidant defense weakens with age. Chronic changes in the composition of factors present in aqueous or vitreous humor may induce alterations both in trabecular cells and in cells of the optic nerve head. Free radicals and reactive oxygen species are able to affect the cellularity of the human trabecular meshwork (HTM). These findings suggest that intraocular pressure increase, which characterizes most glaucomas, is related to oxidative and degenerative processes affecting the HTM and, more specifically, its endothelial cells. This supports the theory that glaucomatous damage is the pathophysiological consequence of oxidative stress. Glaucomatous subjects might have a genetic predisposition, rendering them more susceptible to reactive oxygen species-induced damage. It is likely that specific genetic factors contribute to both the elevation of IOP and susceptibility of the optic nerve/retinal ganglion cells (RGCs) to degeneration. Thus, oxidative stress plays a fundamental role during the arising of glaucoma-associated lesions, first in the HTM and then, when the balance between nitric oxide and endothelins is broken, in neuronal cell. Vascular damage and hypoxia, often associated with glaucoma, lead to apoptosis of RGCs and may also contribute to the induction of oxidative damage to the HTM. On the whole, these findings support the hypothesis that oxidative damage is an important step in the pathogenesis of primary open-angle glaucoma and might be a relevant target for both prevention and therapy.

A novel perspective on natural therapeutic approaches in glaucoma therapy

Glaucoma is becoming recognised as a condition for which not only elevated intraocular pressure (IOP), but also non-pressure-dependent risk factors, are responsible. Better knowledge of the pathogenesis has opened up new therapeutic approaches that are often referred to as non-IOP-lowering treatment. These new avenues of treatment, some of which are still under investigation, include agents that can improve vascular regulation and blood flow to the eye and reduce oxidative stress. Vascular regulation can be improved systemically with magnesium. Dark chocolate and omega-3-fatty acids can also improve blood flow regulation. Oxidative stress at mitochondrial level can be reduced by gingko. Polyphenolic flavonoids (tea, coffee and red wine), anthocyanosides, ubiquinone and melatonin have antioxidant properties, and heat-shock proteins can be induced naturally by the use of sauna baths. Future intensive studies on the effect of these compounds may open up a new therapeutic era in glaucoma.

Electrophysiological Analysis of the Effects of Ginkgo Biloba on Visual Processing in Older Healthy Adults

Several studies have tested the efficacy of ginkgo biloba using compromised visual systems and have found improvement in vision. We measured functional changes in the visual system of older, healthy adults to see if ginkgo extract EGb 761 would increase performance in the normal visual system. Two electrophysiological measures were taken during baseline, placebo, and treatment conditions: visual evoked potentials were used to assess changes in low-level functioning of the visual pathways, and P300 recognition responses were measured to assess higher order processing. No significant effect was found in the lower level visual pathways. However, when using regression analysis across age to assess higher order functioning, an improvement was found. The results suggest that the higher order processing stages, which may be influenced by cognition, decline more rapidly than do lower level processing stages in healthy adults as a function of age, and that the use of ginkgo biloba extract may improve the functioning of this system.

The potential impact of the use of homeopathic and herbal remedies on monitoring the safety of prescription products

The purpose of this paper is to explore the possibility that adverse reactions and drug interactions arising from the use of homeopathic and herbal medicines could lead to confusion when adverse reactions to conventional medicines are reported. An extensive literature review was conducted on the occurrence of adverse reactions and drug interactions following the use of homeopathic or herbal remedies, and the potential for these to confound adverse event reporting to conventional medicines considered. The survey demonstrates the potential for herbal remedies and homeopathic products, to produce adverse drug reactions or drug interactions, and shows the scope for potential for confusion with those arising from conventional medicines. There is a need for greater awareness that adverse reactions apparently due to a conventional medicine, might in reality be due to a herbal medicine or a drug interaction between a herbal medicine and a conventional drug, particularly when a health professional is unaware of the extent of a patient's self-medication with alternative therapies.

Effect of glaucoma on the retinal glutamate/glutamine cycle activity

Glutamate-induced excitotoxicity has been proposed to mediate the death of retinal ganglion cells in glaucoma. The metabolic dependence of glutamatergic neurons upon glia via the glutamate/glutamine cycle to provide the precursor for neurotransmitter glutamate is well established. Thus, the aim of the present work was to study the retinal glutamate/glutamine activity in eyes with hypertension induced by intracameral injections of hyaluronic acid (HA). For this purpose, weekly injections of HA were performed unilaterally in the rat anterior chamber, whereas the contralateral eye was injected with saline solution. At 3 or 10 weeks of treatment, glutamate and glutamine uptake and release were assessed using [3H]-glutamate and [3H]-glutamine as radioligands, respectively. In addition, glutamine synthetase activity was assessed by a spectrophotometric assay, whereas glutaminase activity was measured through the conversion of [3H]-glutamine to [3H]-glutamate. At 3 weeks of treatment with HA, a significant decrease (P<0.01) in glutamate uptake and glutamine synthetase activity was observed. Glutamine uptake and release, as well as glutaminase activity, were significantly increased (P<0.01) in eyes injected with HA for 3 weeks compared with vehicle-injected eyes, whereas [3H]-glutamate release did not change in hypertensive eyes. Only the changes in glutamine synthetase activity persisted at 10 weeks of treatment with HA. These results indicate a significant alteration in the retinal glutamate/glutamine cycle activity in hypertensive eyes. Since these changes preceded both functional and histological alterations induced by ocular hypertension, these results support the involvement of glutamate in glaucomatous neuropathy.

Cellular and molecular events in corneal wound healing: significance of lipid signalling

Alterations in the normal healing process after corneal injury can produce undesirable outcomes that range from corneal haze to ulceration and perforation. Lipids play important roles in the complex inflammatory processes that occur after corneal wounding. While some lipid mediators, such as the lipoxygenase derivatives of arachidonic acid, 12-hydroxyeicosatetraenoic acid (12[S]-HETE and 15[S]-HETE), act as second messengers to promote cell proliferation and are possibly involved in the synthesis of other molecules that suppress inflammation, others, such as platelet-activating factor (PAF), exert their actions through specific receptors, play key roles during sustained corneal inflammation (as might occur with chemical burns), and contribute to tissue destruction and neovascularization. PAF is also a strong inducer of selective metalloproteinases (MMPs) that degrade the extracellular matrix. The use of a new PAF antagonist has shown great promise for the treatment of diffuse lamellar keratitis (DLK) and alkali-burned corneas.

The effects of antiglaucoma and systemic medications on ocular blood flow

Based on the body of evidence implicating ocular blood flow disturbances in the pathogenesis of glaucoma, there is great interest in the investigation of the effects of antiglaucoma drugs and systemic medications on the various ocular vascular beds. The primary aim of this article was to review the current data available on the effects of antiglaucoma drugs and systemic medications on ocular blood flow. We performed a literature search in November 2002, which consisted of a textword search in MEDLINE for the years 1968-2002. The results of this review suggest that there is a severe lack of well-designed long-term studies investigating the effects of antiglaucoma and systemic medications on ocular blood flow in glaucomatous patients. However, among the 136 articles dealing with the effect of antiglaucoma drugs on ocular blood flow, only 36 (26.5%) investigated the effects of medications on glaucoma patients. Among these 36 articles, only 3 (8.3%) were long-term studies, and only 16 (44.4%) were double-masked, randomized, prospective trials. Among the 33 articles describing the effects of systemic medications on ocular blood flow, only 11 (33.3%) investigated glaucoma patients, of which only one (9.1%) was a double-masked, randomized, prospective trial. Based on this preliminary data, we would intimate that few antiglaucoma medications have the potential to directly improve ocular blood flow. Unoprostone appears to have a reproducible antiendothelin-1 effect, betaxolol may exert a calcium-channel blocker action, apraclonidine consistently leads to anterior segment vasoconstriction, and carbonic anhydrase inhibitors seem to accelerate the retinal circulation. Longitudinal, prospective, randomized trials are needed to investigate the effects of vasoactive substances with no hypotensive effect on the progression of glaucoma.

Effect of Ginkgo biloba extract on preexisting visual field damage in normal tension glaucoma

OBJECTIVE

To evaluate the effect of Ginkgo biloba extract (GBE) on preexisting visual field damage in patients with normal tension glaucoma (NTG).

DESIGN

Prospective, randomized, placebo-controlled, double-masked cross-over trial.

PARTICIPANTS

Twenty-seven patients with bilateral visual field damage resulting from NTG.

INTERVENTION

Patients received 40 mg GBE, administered orally, three times daily for 4 weeks, followed by a wash-out period of 8 weeks, then 4 weeks of placebo treatment (identical capsules filled with 40 mg fructose). Other patients underwent the same regimen, but took the placebo first and the GBE last. Visual field tests, performed at baseline and at the end of each phase of the study, were evaluated for changes.

MAIN OUTCOME MEASURES

Change in visual field and any ocular or systemic complications.

RESULTS

After GBE treatment, a significant improvement in visual fields indices was recorded: mean deviation (MD) at baseline versus MD after GBE treatment, 11.40 +/- 3.27 dB versus 8.78 +/- 2.56 dB (t = 8.86, P = 0.0001, chi-square test); corrected pattern standard deviation (CPSD) at baseline versus CPSD after GBE treatment, 10.93 +/- 2.12 dB versus 8.13 +/- 2.12 dB (t = 9.89, P = 0.0001, chi-square test). No significant changes were found in intraocular pressure, blood pressure, or heart rate after placebo or GBE treatment. Any ocular and systemic side effects were recorded for the duration of the trial.

CONCLUSIONS

Ginkgo biloba extract administration appears to improve preexisting visual field damage in some patients with NTG.

Vasospasm, its role in the pathogenesis of diseases with particular reference to the eye

Vasospasm can have many different causes and can occur in a variety of diseases, including infectious, autoimmune, and ophthalmic diseases, as well as in otherwise healthy subjects. We distinguish between the primary vasospastic syndrome and secondary vasospasm. The term "vasospastic syndrome" summarizes the symptoms of patients having such a diathesis as responding with spasm to stimuli like cold or emotional stress. Secondary vasospasm can occur in a number of autoimmune diseases, such as multiple sclerosis, lupus erythematosus, antiphospholipid syndrome, rheumatoid polyarthritis, giant cell arteritis, Behcet's disease, Buerger's disease and preeclampsia, and also in infectious diseases such as AIDS. Other potential causes for vasospasm are hemorrhages, homocysteinemia, head injury, acute intermittent porphyria, sickle cell disease, anorexia nervosa, Susac syndrome, mitochondriopathies, tumors, colitis ulcerosa, Crohn's disease, arteriosclerosis and drugs. Patients with primary vasospastic syndrome tend to suffer from cold hands, low blood pressure, and even migraine and silent myocardial ischemia. Valuable diagnostic tools for vasospastic diathesis are nailfold capillary microscopy and angiography, but probably the best indicator is an increased plasma level of endothelin-1. The eye is frequently involved in the vasospastic syndrome, and ocular manifestations of vasospasm include alteration of conjunctival vessels, corneal edema, retinal arterial and venous occlusions, choroidal ischemia, amaurosis fugax, AION, and glaucoma. Since the clinical impact of vascular dysregulation has only really been appreciated in the last few years, there has been little research in the according therapeutic field. The role of calcium channel blockers, magnesium, endothelin and glutamate antagonists, and gene therapy are discussed.