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.

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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

AIM: To estimate the prevalence of glaucoma among people worldwide. METHODS: Available published data on glaucoma prevalence were reviewed to determine the relation of open angle and angle closure glaucoma with age in people of European, African, and Asian origin. A comparison was made with estimated world population data for the year 2000. RESULTS: The number of people with primary glaucoma in the world by the year 2000 is estimated at nearly 66.8 million, with 6.7 million suffering from bilateral blindness. In developed countries, fewer than 50% of those with glaucoma are aware of their disease. In the developing world, the rate of known disease is even lower. CONCLUSIONS: Glaucoma is the second leading cause of vision loss in the world. Improved methods of screening and therapy for glaucoma are urgently needed.

https://bjo.bmj.com/content/bjophthalmol/80/5/389.full.pdf

Number of people with glaucoma worldwide.

Global prevalence of glaucoma and projections of glaucoma burden through 2040: a systematic review and meta-analysis.

Dasatinib inhibits peripapillary scleral myofibroblast differentiation.

Prophylactic Antibiotics after Glaucoma Surgery: Where Is the Evidence?

Purpose To determine how often glaucoma specialists set a target intraocular pressure (IOP) and how they respond when the target is not achieved. Methods We reviewed 250 randomly selected charts of glaucoma patients seen by 5 glaucoma specialists to identify whether a target IOP was specifically set and to detail the plan of action when the target was exceeded. Results A target IOP was present for at least 1 eye in 66% of patients (165/250). Among the patients of 5 physicians, the percentage with a target IOP for both eyes ranged from 90% to 34%. Half of eyes with no target had an explaining feature, whereas the other half did not. The study visit IOP exceeded the target in at least 1 eye in 29% (50/173) of patients. When the target was not met, 66% (33/50) had a notation of action taken, with no significant difference among physicians in whether any action was taken (P=0.64). The significant differences among the 5 physicians in the use of target IOP were potentially associated with patient demographic and clinical features, such as age, race, treatment intensity, and visual field damage, which differed among the 5 practices (all P Conclusions Target IOP was recorded in the large majority of patient charts, but its use varied by physician and patient characteristics. On nearly one third of visits, IOP exceeded the target, indicating the need for active decision-making and management changes.

Adherence With the Use of Target Intraocular Pressure for Glaucoma Patients in a Large University Practice.

Since L-dopa and serotonin have been reported to increase the rate of axonal transport in rat sciatic nerve, we decided to study the effect of these monoamines on rapid orthograde transport in the rattit optic nerve To do this, tritiated leucine was injected into the vitreous of both eyes of 56 albino rabbits, and arrival of radioactive labeled proteins at the superior colliculus was measured at various intervals by liquid scintillation counting Rabbits were studied 24 hr after intraperitoneal injections of (1) Sinemet + L-dopa, (2) Sinemet + 5-hydroxytryptophan, or (3) pargyline There were 14 rabbits in each group compared to 14 controls that received no monoamies In the monoamine-treated groups, transported labeled proteins arrived at the superior colliculus earlier, and an increased amount of radioactivity accumulated during the next several hours The maximum amount of radioactive proteins accumulating in drug-treated animals did not differ significantly from the maximum amount in control animals As judged by autoradiographic densitometry, retinal ganglion cell synthesis was similar in control and drug-treated animals We suspect that the rate of rapid axonal transport is increased by monoamines, although an increased rate of ganglion cell protein synthesis is another possibility

The effect of biogenic monomines on rapid axonal transport in the rabbit optic nerve.

The mechanical behavior of the lamina cribrosa (LC), the connective tissue that supports the retinal ganglion cells (RGCs), plays an important role in the development of glaucoma. We have developed an in-vitro inflation test to measure the three-dimensional displacement and strain fields in the posterior 250 μm of the LC in response to controlled pressurization. Human eyes were obtained from a tissue bank and the posterior sclera mounted in a pressure-controllable fixture. A laser-scanning microscope was used to acquire SHG images of the deforming tissue structure in response to pressure changes, and the fast-iterative digital volume correlation (FIDVC) algorithm developed by Bar Kochba et al. (Experimental Mechanics 55:261–274, 2015) was used to calculate 3D displacement fields from the SHG signal. Strains were calculated by fitting a high order polynomial function to the displacement field and taking the gradient. To compare for regional variation of the strains, the LC was divided about the central retinal artery and vein (CRAV) into the superior, nasal, inferior, and temporal quadrants and further divided into inner, middle, and outer radial regions centered on the CRAV and three equal regions through the thickness. These regions were statistically compared using a univariate repeated anova. We found that displacements and strains in the LC exhibited substantial variation in the plane but not through the thickness. The average shear strains were significantly smaller than the normal strains (p = 0.0006, 45 mmHg). For all eyes, the LC appeared as an elliptical plate. The normal strains were greater along the major axis compared to the minor axis of the LC for all eyes tested (p = 0.03, 45 mmHg). The maximum principal strains were also found to be greater in the middle inferior and temporal regions than in the superior and nasal regions (p = 0.07, 45 mmHg). Eyes exhibited two kinds of radial variation. Three out of six specimens exhibited the stiffest behavior around the CRAV with higher principal strains towards the periphery, while the remainder were more compliant around the CRAV with lower principal strain on the periphery. These regional variations in pressure-derived strains in the LC may help to explain the progression of axonal damage observed in glaucoma.

Harry A. Quigley

Papers

Dasatinib inhibits peripapillary scleral myofibroblast differentiation.

Prophylactic Antibiotics after Glaucoma Surgery: Where Is the Evidence?

Adherence With the Use of Target Intraocular Pressure for Glaucoma Patients in a Large University Practice.

The effect of biogenic monomines on rapid axonal transport in the rabbit optic nerve.

Regional variations in the mechanical strains of the human optic nerve head