Vitamin metabolism and therapy in ophthalmology

Visual loss and optic nerve head swelling in thiamine deficiency without prolonged dietary deficiency

Visual loss due to optic neuropathy is a rare manifestation of thiamine deficiency. We report a case of a 39-year-old woman with a body mass index (BMI) of 29 kg/m(2) who developed visual loss and bilateral optic nerve head swelling after a short, self-limited gastrointestinal illness. She was disoriented and inattentive and had absent ankle jerk reflexes, diminished sensation in both legs below the knees, and marked truncal ataxia. Magnetic resonance imaging (MRI) showed increased T2-signal in the medial thalami and mammillary bodies. The serum thiamine level was 8 nmol/L (normal 8-30). The diagnosis of thiamine deficiency was made, and the patient's vision and neurologic symptoms improved significantly with intramuscular thiamine treatment. Thiamine deficiency can occur in the absence of an obvious predisposing factor such as alcoholism or low body weight. The clinician must be aware of the factors that govern vitamin availability and maintain a high index of suspicion to make the diagnosis in such cases.

Nutrition and the eye

The topic "nutrition and the eye" cannot adequately be covered in a single review article; indeed, dozens of books and hundreds of articles have been written on the subject. This review concentrates on three areas in which specific nutrients are known or theorized to have a major impact on vision and the visual system: vitamin A deficiency; antioxidants and their proposed role in the prevention of age-related cataract and macular degeneration; and nutritional optic neuropathies, including those of the recent Cuban epidemic. In addition, this article touches on nutritional treatments that have been suggested for several less common eye diseases and, finally, considers several less prevalent conditions in which deficiency of or excess exposure to a particular nutrient has been associated with ocular pathology.

Ophthalmologic effects of bowel disease

Ocular findings in diseases affecting primarily the digestive tract are relatively rare; however, it is important for the physician to recognize these relationships, appropriately uncover symptoms related to the eye disease, and have the patient evaluated by an ophthalmologist if indicated. In addition, ocular inflammation may be the first indication of bowel disease (e.g., uveitis in Crohn's disease). This article describes the associations between ocular diseases and gastrointestinal diseases and their causes, signs, symptoms, prognosis, and treatment.

Nutrition supplements and the eye

PURPOSE

A review of the role of vitamins, minerals, carotenoids and essential fatty acids in relation to eye health. The mode of action may be directly on the eye or by promoting bodily health on which the eye depends.

RESULTS

The lens and retina suffer oxidative damage and the anti-oxidant vitamins A, C and E are implicated as protective. Studies in man give indifferent support to the role of nutrition in the development of cataract. In the elderly, vitamin intake may be inadequate, so that a vitamin supplement may be reasonable. Zinc has a role in retinal metabolism and may be beneficial in macular degeneration. Selenium has an anti-oxidant role. Other minerals including copper have a less defined role. Carotenoids are concentrated at the macula and have an anti-oxidant role. A reduced risk of macular degeneration is found in relation to a high serum level. The essential fatty acid, gamma-linolenic acid (GLA), is useful in Sjögren's syndrome and may help in other dry eye conditions. Omega-3 fatty acids are important in retinal development and have a role in preventing cardiovascular disease.

CONCLUSION

All persons should be encouraged to maintain healthy nutrition. Middle-aged and elderly patients may benefit from a supplement. An intake in excess of the recommended daily intake may be beneficial, but this is not proven. Further clinical trials are indicated to define the advisability of vitamin, mineral and other supplements. Dosages for recommended intake and for supplements are given.

Adenosine triphosphate deficiency: a genre of optic neuropathy

PURPOSE

To offer clinical evidence that deficiency of vitamin B12 may adversely affect the neuronal function of patients who also have the 14,484 mitochondrial DNA mutation associated with Leber's hereditary optic neuropathy (LHON).

METHODS

A case of a 27-year-old man with vitamin B12 deficiency and the 14,484 mitochondrial DNA mutation is presented and the literature on causes of some metabolic optic neuropathies reviewed.

RESULTS

Visual loss and neurologic symptoms of vitamin B12 deficiency occurred together, at a time when the level of vitamin B12 was subnormal. Vision and other sensory functions began to improve within 2 months of vitamin therapy, and normal vision eventually was restored.

CONCLUSIONS

The relatively prompt improvement and the eventual complete recovery of vision following vitamin replacement therapy suggest that the subnormal level of vitamin B12 precipitated visual loss. Given the clinical similarities of subnormal vitamin B12, LHON, and nutritional/tobacco amblyopia, deficiency of adenosine triphosphate might be a unifying etiology for several types of optic neuropathy. This energy hypothesis provides a theoretical basis for the enigmatic phenomena of centrocecal scotomata and recovery of visual function after prolonged blindness.

Causes of low vision and blindness in south western Saudi Arabia. A hospital-based study

The authors studied 1,681 consecutive patients who attended their ophthalmic outpatient clinics over a period of 12 months to determine the patients' visual acuity status and the causes of any visual loss. Using the World Health Organization criteria for definition of visual acuity status, 1004 (59.7%) patients had normal vision. Four hundred and thirty-one (25.6%) patients had low vision or visual impairment and 246 (14.6%) patients were blind. Twenty-eight (1.9%) patients had no light perception in both eyes. Cataract, both in isolation and co-existing with other ocular pathology, was the major cause of both low vision and blindness (58.5% and 81.7%, respectively). A concerted attack on cataract alone will markedly reduce blindness and low vision in this region.