Optician's clinical editor, Bill Harvey, and Professor Robert Fletcher (below) look at two books regarding nutrition and the eye
Nutrition and the Eye : A Practical Approach
On seeing that this book was now finally available, my first response was 'at last!' Many patients now ask for advice on nutrition, having read various sources making claims about the influence of nutrition upon eye health.
While some are aware that a good diet is helpful in maintaining some aspects of eye health, too many often misinterpret some of the marketing literature available, and often assume that certain vitamin tablets will 'make my eyes better' or, worse, 'can cure my macular degeneration'.
This comprehensive book takes an objective look at the influence of nutrition upon the eye and the research that has made our understanding of the complex interaction between diet and health. It is well-referenced and, importantly, offers information in a clear and unbiased way.
The sections are colour-coded and sensibly split. All eye care practitioners will find the initial section on nutrition science valuable as it offers a wealth of information on nutrition science, absorption factors, measures of nutrition and a clarification of the often confused terminology used in nutrition-related literature.
The next section offers a very comprehensive review of the various nutritional components, such as carotenoids, lipids and minerals, and how they influence the eye. The section ends with a very clearly written summary of the effects of oxidative stress upon ocular tissues.
After a brief but interesting look at retinitis pigmentosa and two vitamin deficiencies, there is an excellent and extensive section on the ageing eye which is where the book comes into its own. Anyone having read this should be well armed to offer good fact-based advice to a patient interested in better understanding what sort of nutritional influences upon the eye exist. Initially, I was disappointed that there was no related appendix summarising best advice to patient. The book, though, does leave it open for every practitioner to tailor such a fact sheet to their individual practice profile based on the information offered here.
Towards the end, there are two chapters detailing the research projects each author is involved with. As neither study is completed, these whet one's appetite for future findings, serving as a useful indication of research design for students.
I wholeheartedly recommend this text to anyone working in the low vision arena, where issues relating to nutrition and particularly AMD are a constant feature. However, all in practice should find much of value to allow them, not only to advise patients, but to read with greater objectivity some of the claims from various commercial and popular media sources with which they are bombarded.
Nutrition and the Eye - a Practical Approach. Edited by Frank Eperjesi and Stephen Beatty. Elsevier Butterworth-Heinemann. ISBN 0-7506-8816-5, 280pp. £39.99.
Nutrition and the Eye : Basic and Clinical Research
Whether for personal advantage or to give more reliable advice to patients, practitioners must find this new text of considerable interest. Written in English by 10 German and Austrian contributors, developments in basic research and clinical studies are presented.
Certainly many chemical and physiological details will tend to be daunting for non-specialists, yet these detract little from the ease with which the varied applications are described.
Antioxidants, supplements to diet and trace elements are covered in a balanced way, in relation to ocular diseases. Mechanisms of nutrition and preventative actions are featured throughout; for example oxidative stress, the way in which carotenoids might filter blue light from damaging photoreceptors and several studies of experimental cataract are given. Macular pigment contains carotenoids, actually in varied ratios in different parts of the region and has been shown to have possible increases in density as the result of supplements. Foveal and peripheral receptors contain carotenoids, which tend to act as scavenger protectors and/or blue light filters. Extensive reference lists are given, sometimes more than 10 pages, making searches somewhat tedious.
An important feature is the series of tables giving the amount of vitamins in various foods, former and current RDA proposals for vitamins, zinc and selenium. It appears that the content of selenium in Brazil nuts may vary by a factor of 10, according to where they are grown.
While selenium differences can interfere with resistance to viral infections, excess can be toxic and errors in manufacturing tablets have been clinically significant. There are interactions between nutrients such as high amounts of iron given to infants causing reduced copper absorption, high intakes of zinc also being associated with copper deficiency. Differences between animal and human studies tend to cloud some of these issues.
Vitamin E is an important lipid-soluble antioxidant but there is some lack of clear conclusions about the effects of diet and supplementation on cataract and macular degeneration. Nevertheless, data is described as having shown a 'crucial role' in the pathogenesis of AMD and cataract, although lifestyle and environmental factors are considered to be important. There is room for more studies on antioxidants, Vitamin C, E carotenoids (such as luetin and zeaxanthin) and flavonoids.
There is frequent reference to age-related macular degeneration, cancerous conditions, cardiovascular diseases and cataracts. The pros and cons of red wine consumption are touched upon, with some caution, including the regional variations in France which have formed the 'French paradox'.
Cataract is considered in relation to many possible factors, such as smoking or mineral and vitamin deficiencies. The conclusions which appear at the end of each chapter are worthy of particular note; pages 137, 138 and 141 are useful pointers for those who wish to consider the potential usefulness of this book.
There are still dilemmas present in relation to possible attempts to reduce AMD. The chapter on retinal nutrition gives useful points on three theories about AMD, notably 'Oxidative stress', 'Choroidal circulation' and 'Bruch's membrane' approaches; a good summary for teachers and students.
Nutrition and the Eye, Basic and Clinical Research. Editor: Albert J Augustin. ISBN 3-8055-7838-5. 152pp. €111.50