Objective: To demonstrate optical coherence tomography for high-resolution, noninvasive imaging of the human retina. Optical coherence tomography is a new imaging technique analogous to ultrasound B scan that can provide cross-sectional images of the retina with micrometer-scale resolution. Design: Survey optical coherence tomographic examination of the retina, including the macula and optic nerve head in normal human subjects. Settings Research laboratory. Participants: Convenience sample of normal human subjects. Main Outcome Measures: Correlation of optical coherence retinal tomographs with known normal retinal anatomy. Results: Optical coherence tomographs can discriminate the cross-sectional morphologic features of the fovea and optic disc, the layered structure of the retina, and normal anatomic variations in retinal and retinal nerve fiber layer thicknesses with 10- μm depth resolution. Conclusion: Optical coherence tomography is a potentially useful technique for high depth resolution, cross-sectional examination of the fundus.

Optical Coherence Tomography of the Human Retina

A pilot study of enhanced depth imaging optical coherence tomography of the choroid in normal eyes.

PURPOSE\nTo measure macular choroidal thickness in normal eyes at different points using enhanced depth imaging (EDI) optical coherence tomography (OCT) and to evaluate the association of choroidal thickness and age.\n\n\nDESIGN\nRetrospective, observational case series.\n\n\nMETHODS\nEDI OCT images were obtained in patients without significant retinal or choroidal pathologic features. The images were obtained by positioning a spectral-domain OCT device close enough to the eye to acquire an inverted image. Seven sections were obtained within a 5 x 30-degree area centered at the fovea, with 100 scans averaged for each section. The choroid was measured from the outer border of the retinal pigment epithelium to the inner scleral border at 500-microm intervals of a horizontal section from 3 mm temporal to the fovea to 3 mm nasal to the fovea. Statistical analysis was performed to evaluate variations of choroidal thickness at each location and to correlate choroidal thickness and patient age.\n\n\nRESULTS\nThe mean age of the 30 patients (54 eyes) was 50.4 years (range, 19 to 85 years), and 14 patients (46.7%) were female. The choroid was thickest underneath the fovea (mean, 287 microm; standard deviation, +/- 76 microm). Choroidal thickness decreased rapidly in the nasal direction and averaged 145 microm (+/- 57 microm) at 3 mm nasal to the fovea. Increasing age was correlated significantly with decreasing choroidal thickness at all points measured. Regression analysis suggested that the subfoveal choroidal thickness decreased by 15.6 microm for each decade of life.\n\n\nCONCLUSIONS\nChoroidal thickness seems to vary topographically within the posterior pole. The thickness of the choroid showed a negative correlation with age. The decrease in the thickness of the choroid may play a role in the pathophysiologic features of various age-related ocular conditions.

Enhanced Depth Imaging Optical Coherence Tomography of the Choroid in Normal Eyes

Purpose. To study posterior choroidal thickness and its profile based on location in healthy Japanese subjects and the correlation with axial length, refractive error (RE), and age. Methods. Eighty-six eyes of 43 healthy volunteers with no ophthalmic or systemic symptoms were examined with prototype high-penetration optical coherence tomography using a 1060-nm light source. Eyes with high myopia (exceeding -6 D) or with retinal/choroidal disease were excluded. The spherical equivalent RE was measured by autorefractometry, and the axial length was measured by partial coherence inferometry. Results. Mean choroidal thicknesses were 354 +/- 111 mum at the fovea, 364 +/- 86 mum superiorly, 345 +/- 108 mum inferiorly, 227 +/- 532 mum nasally, and 337 +/- 102 mum temporally. Subfoveal choroidal thickness was significantly greater than nasal (P < 0.01) and temporal (P < 0.05) choroidal thickness; however, there was no significant difference compared with superior (P = 0.20) and inferior (P = 0.17) choroidal thickness. The temporal choroid was significantly (P < 0.01) thicker than the nasal choroid, and the inferior choroid was significantly (P < 0.01) thinner than the superior choroid. There was a significant negative correlation between foveal choroidal thickness and axial length (P < 0.05) but a borderline correlation with the RE (P = 0.086) and age (P = 0.07). Age was the factor that was most associated with the choroidal thickness (F = 20.86; P < 0.001), followed by RE (F = 5.37; P < 0.05); axial length was not a significant factor (F = 1.47; P = 0.22) by stepwise analysis. Conclusions. The profile of choroidal thickness depends on its location. RE, axial length, and especially age are critical for evaluation of choroidal thickness.

Choroidal thickness in healthy Japanese subjects.

PURPOSE. To study the choroidal thickness in healthy subjects by swept-source optical coherence tomography (SS-OCT) at longer wavelength. METHODS. The macular area of 31 eyes (31 healthy volunteers) was studied with an SS-OCT prototype system, which uses a tunable laser as a light source operated at 100,000 Hz A scan repetition rate in the 1-m wavelength region. Three-dimensional volumetric measurement comprised of 512 128 A scans was acquired in 0.8 second. From a series of OCT images, a chroidal thickness map of the macular area was created by manual segmentation. To evaluate interoperator reproducibility, the choroidal thickness in each section from 10 subjects was determined independently by two observers. RESULTS. SS-OCT at the 1-m wavelength region allowed visualization of the fine structure of the choroid as well as that of the retina. Mean choroidal thickness and volume in the macula area were, respectively, 191.5 74.2 m and 5.411 2.097 mm 3 . The mean choroidal thickness of the outer nasal area was significantly thinner than that of all other areas (P 0.05). The measurements by the two independent observers were significantly identical; the intraclass correlation coefficient in mean choroidal thickness was between 0.945 and 0.980 in each area. The macular choroidal thickness was significantly correlated with axial length after adjustment for age (P 0.001), and with age after adjustment for axial length (P 0.001). CONCLUSIONS. SS-OCT system at 1 m provides macular choroidal thickness maps and allows one to evaluate the choroidal thickness more accurately. (Invest Ophthalmol Vis Sci. 2011; 52:4971‐4978) DOI:10.1167/iovs.11-7729

https://www.topcon-medical.it/files/Local_TES/Estudios_clinicos/15Macular_choroidal_thickness_and_volume_in_normal_subjects_measured_by_SS_OCT.pdf

Macular choroidal thickness and volume in normal subjects measured by swept-source optical coherence tomography.

High-resolution ultrasonic imaging of the posterior segment ☆

Broadband ultrasound imaging is capable of achieving superior resolution in clinical applications. An effective and easy way of manufacturing broadband transducers is desired for these applications. In this work, a partial composite in which the piezoelectric plate is mechanically graded with a number of rectangular grooves is introduced. Finite Element Analysis (FEA) demonstrated that the partial composite could easily obtain multiple resonant modes, which resulted in a broadband time-domain response. Experimental tests were carried out to validate the theoretical results. Based upon the FEA designs, several single-element transducers were fabricated using either a non-diced ceramic or a diced partial composite. A superior bandwidth of 92% was achieved by the partial composite transducer when compared to a bandwidth of 56% produced by the non-diced ceramic transducer.

Fabrication of Broadband Graded Transducer Using Piezoelectric Partial Composites

This paper describes the design, fabrication, and experimental results of a novel transducer for measuring intravascular blood flow. The transducer consists of a diffraction-grating transducer, to provide vector Doppler capability, wrapped around a cylinder for mounting on a catheter. The new device appears to be useful for quantitative flow measurements to guide and assess intravascular procedures.∗

Jon Cannata

Papers

High-resolution ultrasonic imaging of the posterior segment ☆

Fabrication of Broadband Graded Transducer Using Piezoelectric Partial Composites

A new device for intravascular blood-flow measurement: The helical diffraction-grating transducer