A technique called optical coherence tomography (OCT) has been developed for noninvasive cross-sectional imaging in biological systems. OCT uses low-coherence interferometry to produce a two-dimensional image of optical scattering from internal tissue microstructures in a way that is analogous to ultrasonic pulse-echo imaging. OCT has longitudinal and lateral spatial resolutions of a few micrometers and can detect reflected signals as small as approximately 10(-10) of the incident optical power. Tomographic imaging is demonstrated in vitro in the peripapillary area of the retina and in the coronary artery, two clinically relevant examples that are representative of transparent and turbid media, respectively.

/pdf/optical-coherence-tomography-3zqbp7mpwb.pdf

Optical coherence tomography

Aim: To estimate the number of people with open angle (OAG) and angle closure glaucoma (ACG) in 2010 and 2020. Methods: A review of published data with use of prevalence models. Data from population based studies of age specific prevalence of OAG and ACG that satisfied standard definitions were used to construct prevalence models for OAG and ACG by age, sex, and ethnicity, weighting data proportional to sample size of each study. Models were combined with UN world population projections for 2010 and 2020 to derive the estimated number with glaucoma. Results: There will be 60.5 million people with OAG and ACG in 2010, increasing to 79.6 million by 2020, and of these, 74% will have OAG. Women will comprise 55% of OAG, 70% of ACG, and 59% of all glaucoma in 2010. Asians will represent 47% of those with glaucoma and 87% of those with ACG. Bilateral blindness will be present in 4.5 million people with OAG and 3.9 million people with ACG in 2010, rising to 5.9 and 5.3 million people in 2020, respectively. Conclusions: Glaucoma is the second leading cause of blindness worldwide, disproportionately affecting women and Asians.

The number of people with glaucoma worldwide in 2010 and 2020

Optical coherence tomography (OCT) has developed rapidly since its first realisation in medicine and is currently an emerging technology in the diagnosis of skin disease. OCT is an interferometric technique that detects reflected and backscattered light from tissue and is often described as the optical analogue to ultrasound. The inherent safety of the technology allows for in vivo use of OCT in patients. The main strength of OCT is the depth resolution. In dermatology, most OCT research has turned on non-melanoma skin cancer (NMSC) and non-invasive monitoring of morphological changes in a number of skin diseases based on pattern recognition, and studies have found good agreement between OCT images and histopathological architecture. OCT has shown high accuracy in distinguishing lesions from normal skin, which is of great importance in identifying tumour borders or residual neoplastic tissue after therapy. The OCT images provide an advantageous combination of resolution and penetration depth, but specific studies of diagnostic sensitivity and specificity in dermatology are sparse. In order to improve OCT image quality and expand the potential of OCT, technical developments are necessary. It is suggested that the technology will be of particular interest to the routine follow-up of patients undergoing non-invasive therapy of malignant or premalignant keratinocyte tumours. It is speculated that the continued technological development can propel the method to a greater level of dermatological use.

https://link.springer.com/content/pdf/bfm%3A978-3-319-06419-2%2F1.pdf

Optical Coherence Tomography

https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(07)61690-0.pdf

Maternal and child undernutrition: global and regional exposures and health consequences

https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(13)60937-X.pdf

Maternal and child undernutrition and overweight in low-income and middle-income countries

Diabetes and Senile Cataract

Moving from science to public health programs: lessons from vitamin A.

Epidemiology as it relates to screening for glaucoma (summary)

Vitamin A deficiency is commonly considered a Third World problem. The article by Vernon et al. (this issue, p 46) reminds us that the condition occurs, albeit infrequently, in affluent western societies. Recognition requires a high level of suspicion, particularly when confronting patients on 'fad' diets', patients with malabsorption states, and especially alcoholics with recalcitrant corneal ulcers2. The problem that vitamin A deficiency poses to the West is only a tiny reflection of the 5 million new cases of xerophthalmia and the quarter million instances of associated corneal destruction and blindness suffered by Third World children each year3. Vernon et al. cite the high risk of subsequent ocular damage to their already deficient subjects. Indeed, sudden decompensation ofborderline vitamin A status can result in rapid corneal necrosis, even before conjunctival xerosis or Bitot's spots appear4. Measles is one of several potent precipitating factors, particularly in Africa5. Recent data suggest that even mild, 'subclinical' deficiency may have important implications for growth, health and survival6. Mortality and infectious morbidity among Indonesian children are more closely correlated with vitamin A status than with general anthropometric measurements7'8. Periodic supplementation with large doses ofvitamin A twice a year9 or daily small-dose supplementation through fortification of a dietary staple'0 both appear to reduce preschool mortality by at least one-third\". Vitamin A treatment reduced case-fatality rates among Tanzanian children hospitalized with severe measles by 50%12. In Indonesia, supplementation increased linear'0 and ponderal'3 growth; while in Indonesia'0 and Latin America'4 it increased serum haemoglobin values. Small daily doses given to otherwise well nourished, healthy Australian children reduced the incidence of recurrent lower respiratory infection by a quarter'5. The mechanism(s) by which vitamin A affects morbidity, mortality, growth and haematopoesis remain uncertain. Vitamin A is necessary for maintenance of mucous-secreting epithelial linings of a wide variety of organs. Deranged metaplasia no doubt interferes with their normal barrier function. Animal experiments in particular suggest roles for vitamin A in the regulation ofboth cell-mediated and humoral immunity'6. Whether the role of vitamin A on growth and haematopoesis is direct, or secondary to its effect on infection, is uncertain. The significance of even marginal, 'subclinical' deficiency has important implications for the management of cystic fibrosis and related disorders. While one should be observant for signs and symptoms of frank deficiency, proper care will ensure these never occur in the first place; by the time they do, the individual may already have suffered potentially lethal consequences. Daily supplementation with 5000-10 000 i.u. is often inadequate for maintaining normal vitamin A stores in patients with cystic fibrosis. The average daily intake ofAmericans lies within this range. Daily oral supplements of 25 000 to 50 000 i.u. vitamin A are often required. The optimal daily supplement needs to be titrated through periodic assessment. Serum retinol, as reliably determined by high performance liquid chromatography (HPLC), provides a useful index. As long as levels run well within the normal range (40-70 #g/dl [ 1.4-2.5 ismol/I] ) the absence of even subclinical deficiency is reasonably assured. In some instances of severe lipid malabsorption, periodic intramuscular injections ofwatermiscible vitamin A may be necessary. Oil miscible vitamin A, as was used in Vernon's first case, is poorly absorbed from the injection site and should therefore be avoided. Chronic, severe malabsorption of vitamin A, as sometimes encountered in cystic fibrosis, is one ofthe very few instances in which injectable vitamin A is required. The vast majority of vitamin A deficient children, including Third World children with severe malnutrition, diarrhoea and keratomalacia, respond as rapidly and successfully to oral as to injectable preparations'7. Oral therapy is obviously far cheaper and safer.

https://journals.sagepub.com/doi/pdf/10.1177/014107688908200101

Vitamin A deficiency today: conjunctival xerosis in cystic fibrosis.

Eyes or patients? Traps for the unwary in the statistical analysis of ophthalmological studies: by R.G. Newcombe and G.R. Duff. Br J. Ophthalmol 71:645–646, 1987

Alfred Sommer

Papers

Diabetes and Senile Cataract

Moving from science to public health programs: lessons from vitamin A.

Epidemiology as it relates to screening for glaucoma (summary)

Vitamin A deficiency today: conjunctival xerosis in cystic fibrosis.

Eyes or patients? Traps for the unwary in the statistical analysis of ophthalmological studies: by R.G. Newcombe and G.R. Duff. Br J. Ophthalmol 71:645–646, 1987