Homocysteine, folates, and the eye

Plasma homocysteine has been identified as a risk factor for arterial disease, retinal artery and vein occlusions, and other common eye diseases. The value of treating an elevated plasma homocysteine with folic acid for preventing further vascular disease has not been proven. Although secondary prevention of coronary artery disease using this approach has been unsuccessful, trials on primary prevention of stroke and loss of cognitive function with folic acid supplementation appear to be successful. Further trial data are awaited. In patients with premature retinovascular disease, the measurement of plasma homocysteine is suggested and reduction of elevated homocysteine with folic acid for secondary prevention of retinal arterial and venous occlusion. Meanwhile, the debate on fortification of flour for primary prevention of neural tube defects, which has already taken place in North America, continues in European countries. Such fortification could have an impact on primary and secondary prevention of vascular disease.Eye (2008) 22, 989-993; doi:10.1038/sj.eye.6703061; published online 7 December 2007.     

Pandemics,climate change,and the eye

Graefe's Archive for Clinical and Experimental Ophthalmology -     

Relative image size, not eye position, determines eye dominance switches

A recent paper examined eye dominance with the eyes in forward and eccentric gaze [Vision Res. 41 (2001) 1743]. When observers were looking to the left, the left eye tended to dominate and when they were looking to the right, the right eye tended to dominate. The authors attributed the switch in eye dominance to extra-retinal signals associated with horizontal eye position. However, when one looks at a near object on the left, the image in the left eye is larger than the one in the right eye, and when one looks to the right, the opposite occurs. Thus, relative image size could also trigger switches in eye dominance. We used a cue-conflict paradigm to determine whether eye position or relative image size is the determinant of eye-dominance switches with changes in gaze angle. When eye position and relative image size were varied independently, there was no consistent effect of eye position. Relative image size appears to be the sole determinant of the switch.     

Dry eye syndrome, tear film, pharmacology of eye drops, and toxicity

Over the past years, the main parameters used for the diagnosis of dry eye have been outlined: there is now substantial effort to bring them into correlation with each other, resulting in easier diagnosis of the diseases that appear to cause dry eye. Although increasing awareness of the plethora of dry eye diseases makes the differential diagnosis and the treatment difficult, the increased availability of optimized artificial tears and tear substitutes, especially viscoelastics, does allow easier relief of the most serious symptoms of dry eye disease. Improved topical treatment, in turn, allows various treatments, such as excimer laser treatment, to be performed, even in dry eyes. This, together with the identification of tear substitutes as a major research target and a better understanding for the psychological tasks of chronic dry eye diseases, offers a good basis toward further improvements.     

Thrombospondin 1, thrombospondin 2 and the eye

Thrombospondin 1 and thrombospondin 2 (TSP1 and TSP2), which comprise the subgroup A thrombospondins, are matricellular proteins. As matricellular proteins, they modulate interactions between cells and the cellular environment, regulate cell adhesion and typically are expressed during tissue formative processes. In general, TSP1 and TSP2 counter angiogenesis (including tumour angiogenesis) and play important but contrasting roles during cutaneous repair. The two proteins are involved in development, including that of the eye, although evidence suggests that they have their greatest impact during tissue production in the adult. In the normal adult eye, they tend to be found at sites of ongoing matrix synthesis or cell-matrix interactions. At these sites, the two proteins possibly influence cellular differentiation and/or basement membrane deposition. TSP1 is also present in the intraocular fluids and drainage pathway, where it may function in maintaining the anti-angiogenic environment and in intraocular pressure control, respectively. TSP1 could also be involved in ocular immune privilege. Unlike in skin wounds, where TSP1 is derived from the blood and is present only in the early phases of repair, ocular tissue damage appears to lead to protacted TSP1 synthesis by local cells. This response might help suppress angiogenesis in the transparent tissues of the eye and so lessen visual axis opacification following injury. However, TSP2, which is also produced by damaged ophthalmic tissue and may be especially important in matrix organisation, seems to augment contraction in anomalous intraocular fibrosis. Elucidating the roles of TSP1 and TSP2 in ocular physiology and pathobiology may lead to improved therapies for neovascular, neoplastic, reparative and other ophthalmic diseases.     

An eye for an eye,a tooth for a tooth

A 77-year-old man presented with the complaint of a painless decrease in vision in both eyes for 1 year. He underwent bilateral cataract surgery without improvement. Neuro-imaging and genetic testing for mitochondrial disease was negative. Examination was consistent with a diagnosis of toxic-nutritional optic neuropathy. On further questioning the patient admitted chronic ingestion of mouthwash 3 times daily in the past 18 months after completion of dental work. After discontinuation of mouthwash ingestion, visual acuity and fields improved. This case shows how chronic ingestion of mouthwash can lead to a bilateral toxic optic neuropathy, even in the absence of other risk factors.     

The cytological,immunocytochemical and molecular genetic analysis in diagnosis of the neoplasms of the eye,eye adnexa and orbit

The fine needle aspiration biopsy was performed in 91 patients including 57 cases of retrobulbar tumors done under CT control. All aspirates were cytologically examined. In 21 cases immunocytochemical examination was performed in order to distinguish poorly differentiated neoplasms. In 19 cases malignant lymphoma was distinguished from pseudolymphoma. Cytological diagnosis was confirmed by histopathological examination in 77 cases /84%/. One result was false positive, 3-false negative. The value of immunocytochemical methods in differential diagnosis of poorly differentiated neoplasms was stressed.     

暗环境下低中度近视优势眼与非优势眼及双眼对比度视力的对照研究

目的比较暗环境下低中度近视优势眼与非优势眼、双眼对比度视力的差异。方法随机选择拟行准分子激光手术的低中度近视患者47例(94只眼),综合验光仪主觉验光,卡洞法确定优势眼,应用多功能视力检查仪分别测量优势眼、非优势眼和双眼在暗环境暗背景条件下,对比度分别为100%、25%、10%和5%的最佳对比度视力。对所有受试者以及区分低中度近视的优势眼、非优势眼及双眼各对比度视力的差异进行统计学分析。结果所有受试者以及区分低中度近视的双眼对比度视力在对比度为25%、10%、5%均优于优势眼和非优势眼(P<0.05),在对比度为100%时,双眼对比度视力与优势眼差异无统计学意义(P>0.05),但优于非优势眼(P<0.05)。随着对比度的下降,单、双眼的对比度视力亦随之下降。结论在暗环境屈光矫正条件下,高对比度时优势眼的对比度视力优于非优势眼,但低对比度时双眼优于优势眼和非优势眼。     

The kidney, cancer, and the eye: current concepts

Herein, we review the associations between the kidney, renal cancers, and the eye. Renal cancers have been reported to metastasize to the eye and the orbit. As these tumors can be confused with other amelanotic or vascular tumors, a high index of suspicion is required for early detection and management of the primary tumor. We discuss the physiology of metastases, clinical features and management of metastatic disease. A variety of ocular anomalies have been associated with renal disease. Wilms tumor, a renal tumor of childhood, can present with aniridia, which may be the first clue leading to the diagnosis of the primary tumor. Paraneoplastic syndromes are common manifestations of renal cancers and can present as retinopathies and neuro-ophthalmic disorders. Multiple cancer syndromes involve both the eye and the kidney. For example, the diagnosis of von Hippel retinal tumors can lead to a systemic evaluation and discovery of associated visceral tumors. The prognosis, screening, and counseling of such patients is discussed. Newer systemic treatments available for renal tumors, such as interferon alfa, may lead to ocular side effects including retinopathy. These patients require periodic ophthalmic examinations. This review demonstrates the essential role of the ophthalmologist, for early diagnosis and treatment that can help reduce the morbidity and mortality associated with kidney tumors and renal-associated disease.     

Autophagy in the eye: Development,degeneration, and aging

Autophagy is a catabolic pathway that promotes the degradation and recycling of cellular components. Proteins, lipids, and even whole organelles are engulfed in autophagosomes and delivered to the lysosome for elimination. In response to stress, autophagy mediates the degradation of cell components, which are recycled to generate the nutrients and building blocks required to sustain cellular homeostasis. Moreover, it plays an important role in cellular quality control, particularly in neurons, in which the total burden of altered proteins and damaged organelles cannot be reduced by redistribution to daughter cells through cell division. Research has only begun to examine the role of autophagy in the visual system. The retina, a light-sensitive tissue, detects and transmits electrical impulses through the optic nerve to the visual cortex in the brain. Both the retina and the eye are exposed to a variety of environmental insults and stressors, including genetic mutations and age-associated alterations that impair their function. Here, we review the main studies that have sought to explain autophagy's importance in visual function. We describe the role of autophagy in retinal development and cell differentiation, and discuss the implications of autophagy dysregulation both in physiological aging and in important diseases such as age-associated macular degeneration and glaucoma. We also address the putative role of autophagy in promoting photoreceptor survival and discuss how selective autophagy could provide alternative means of protecting retinal cells. The findings reviewed here underscore the important role of autophagy in maintaining proper retinal function and highlight novel therapeutic approaches for blindness and other diseases of the eye.