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

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.

Objective: To measure the active remodeling of the lamina cribrosa (LC) years after IOP lowering by suturelysis. Design: Cohort study. Participants: Glaucoma patients were imaged 20 minutes after laser suturelysis following trabeculectomy surgery and at their follow-up appointment 1-4 years later (16 image pairs; 15 persons). Intervention: Non-invasive optical coherence tomography (OCT) imaging of the eye. Main Outcomes: Deformation calculated by correlating OCT scans of the LC immediately after IOP lowering by suturelysis and those acquired years later (defined as follow-up strain). Results: Mean LC follow-up strain in the anteroposterior direction (Ezz) was 14.0 {+/-} 21.3% (mean, standard deviation, p=0.03), while the LC anterior border moved 60.9 {+/-} 54.6 m into the eye (p=0.0006) on long-term, maintained IOP lowering. Ezz at follow-up was 14 times larger than the direct Ezz response to IOP lowering by suturelysis. There was a significant association between larger LC anterior movement and greater Ezz (p=0.004) at follow-up. Thinner retinal nerve fiber layer (RNFL) at suturelysis was associated with greater follow-up Ezz (p=0.04). Worsening visual field indexes during follow-up were associated with greater LC widening (positive remodeling E{theta}{theta}, p=0.02). Eyes with a greater counterclockwise twist (positive E{theta}z) at suturelysis had greater reversal clockwise twist at follow-up (negative remodeling E{theta}z, p=0.007). Conclusion: Follow-up strains and LC border position changes measured years after IOP lowering are far larger than the immediate strain response and LC border movement response to IOP lowering and indicate dramatic remodeling of the LC anatomical structure caused by IOP lowering and glaucoma progression. The remodeling includes a substantial increase in LC thickness and movement into the eye. Eyes with greater direct strain response to IOP-lowering strains, greater glaucoma damage at suturelysis, and greater worsening of visual field at follow-up experienced greater remodeling.

/pdf/long-term-remodeling-response-in-the-lamina-cribrosa-years-3iy1ocol.pdf

Harry A. Quigley

Papers

Long-Term Remodeling Response in the Lamina Cribrosa Years after IOP Lowering by Suturelysis after Trabeculectomy

Adult metachromatic leukodystrophy

Disk Cupping in Childhood Glaucoma: Reply

Determining mean intraocular pressure.

Identifying Glaucoma in Primary Care Offices.