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Purpose: The purpose of this study was to assess density and morphology of cone photoreceptors (PRs) and corresponding retinal sensitivity in ischemic compared to nonischemic retinal capillary areas of diabetic eyes using adaptive optics optical coherence tomography (AO-OCT) and microperimetry (MP)., Methods: In this cross-sectional, observational study five eyes of four patients (2 eyes with proliferative diabetic retinopathy (DR) and 3 eyes moderate nonproliferative DR) were included. PR morphology and density was manually assessed in AO-OCT en face images both at the axial position of the inner-segment outer segment (IS/OS) and cone outer segment tips (COSTs). Retinal sensitivity was determined by fundus-controlled microperimetry in corresponding areas (MP-3, Nidek)., Results: In AO-OCT, areas affected by capillary nonperfusion showed severe alterations of cone PR morphology at IS/OS and COST compared to areas with intact capillary perfusion (84% and 87% vs. 9% and 8% of area affected for IS/OS and COST, respectively). Mean reduction of PR signal density in affected areas compared to those with intact superficial capillary plexus (SCP) and deep capillary plexus (DCP) perfusion of similar eccentricity was -38% at the level of IS/OS (P = 0.01) and -39% at the level of COST (P = 0.01). Mean retinal sensitivity was 10.8 ± 5.4 in areas affected by DCP nonperfusion and 28.2 ± 1.5 outside these areas (P < 0.001)., Conclusions: Cone PR morphology and signal density are severely altered in areas of capillary nonperfusion. These structural changes are accompanied by a severe reduction of retinal sensitivity, indicating the importance of preventing impaired capillary circulation in patients with DR.

Purpose: To visualize and characterize photoreceptor (PR) layers on a subcellular level in healthy and pathologically aged eyes using adaptive-optics optical coherence tomography technology (AO-OCT)., Methods: AO-OCT scanning was performed within a 2° × 2° field of view, focused on the PR layer at different retinal regions in healthy aged eyes (n = 32 eyes/16 subjects; 62- to 85-years old), eyes with early to intermediate AMD (n = 16 eyes/8 subjects, 65- to 83-years old), and eyes with advanced nonneovascular AMD (n = 16 eyes/8 subjects, 61- to 84-years old). Areas of interest were determined by AO-fundus camera, which is part of the AO-OCT system and spectral-domain (SD)-OCT. PR integrity was evaluated in AO-OCT en face and cross-sectional images at the level of inner/outer segment junction (IS/OS) and cone/PR end tips (COST/ETPR)., Results: AO-OCT in healthy eyes showed clearly distinguishable and regular IS/OS and COST patterns and an inverse relation between cone density and eccentricity. In early to intermediate AMD, PR in between drusen showed more irregular patterns (P < 0.001) and slightly lower PR density (P ≤ 0.002). Drusen caused attenuated and distorted signals and a loss of PR mosaic. In advanced AMD, IS/OS and COST patterns were affected to different degrees between surrounding area, junctional zone, and atrophic area (P < 0.001), ranging from reduced PR densities to total signal loss., Conclusions: AO-OCT imaging allows the three-dimensional visualization of different PR layers in patients with AMD and age-matched healthy subjects. Thereby, AO-OCT provides a unique insight into PR morphology and shows potential to fill the gap between conventional OCT and histologic examination of the retina.

Purpose: To prospectively monitor microaneurysms (MAs) in three dimensions using adaptive optics optical coherence tomography (AOOCT)., Methods: Patients with diabetes mellitus and parafoveal MAs were included in this longitudinal study. At baseline, MAs were identified in standard fluorescein angiography (FA) and subsequently imaged with an AOOCT prototype, incorporated into an AO fundus camera (RTX1, Imagine Eyes) device. Imaging was repeated every 3 months in each patient to explore the potential structural change of MAs over time including size, shape, intraretinal position, (intra-) luminal reflectivity, and other qualitative morphologic characteristics., Results: We imaged 18 MAs in seven eyes (two left eyes) of five patients (mean age: 69 ± 7 years) over 18 months. All MAs appeared as saccular in the en face imaging plane at baseline, and no change in shape was observed in any of the MAs during follow-up. Evaluation of the AOOCT volumes revealed dynamic changes of MAs during follow-up including intermittent growth (n = 2), progressive involution (n = 3), total disappearance (n = 2), and MA division (n = 1). Intraluminal hyperreflective material was visualized in 11 out of 18 MAs, which remained stable (n = 3), increased (n = 2), regressed (n = 1), or fluctuated (n = 5). Three MAs without intraluminal spots at baseline progressively developed distinct hyperreflectivities., Conclusions: AOOCT illustrates the structurally dynamic evolution of MAs in vivo in three dimensions. Despite a consistent saccular shape in the en face view, AOOCT volumes revealed a heterogeneous behavior in regard to size and reflective status of MAs over time.

Purpose: To analyze retinal thickness (RT) and choroidal thickness (ChT) changes in patients with unilateral nongranulomatous acute anterior uveitis (AAU) using three-dimensional (3D) 1060-nm optical coherence tomography (OCT)., Methods: Retinal and choroidal thickness maps were statistically analyzed for 24 patients with newly diagnosed unilateral AAU before therapy. A total of 17 patients were followed until resolution of inflammatory activity (twice in the first week, then weekly). Resolution occurred in all subjects within 6 weeks after the initial diagnosis. After resolution, thickness maps were again generated. All patients were imaged by high-speed spectral-domain (SD) 3D 1060-nm OCT over a 10 × 10-mm field of view. The spatial distribution of retinal and choroidal thickness was mapped and analyzed using the Early Treatment Diabetic Retinopathy Study (ETDRS) grid., Results: The choroid was significantly thicker in eyes affected by AAU than in fellow eyes before therapy with a mean thickness difference of 37 ± 11.44 μm (mean ± SD, Bonferroni correction, α = 0.0125). Following therapy, ChT significantly decreased with a mean change of 24 ± 6.9 μm (mean ± SD, Bonferroni correction, α = 0.0125). There was no significant difference in RT between AAU and fellow eyes before therapy or in AAU eyes before and after therapy., Conclusions: Eyes affected by AAU demonstrate an increase in ChT before and a subsequent decrease after therapy while retinal thickness seems unaltered by disease and therapy. ChT might be a useful biomarker in monitoring posterior involvement and response to therapy in patients with AAU.

Purpose: To describe key developments of optical biometry and optical coherence tomography (OCT) for ophthalmic applications made by one of the pioneering research groups., Methods: Partial coherence interferometry (PCI) as the basic ranging technology for modern optical biometry and for OCT was introduced for biomedical applications in the 1980s. Later, Fourier domain (FD) OCT was introduced and demonstrated to provide superior sensitivity as compared to time domain OCT. Further developments comprised ultrahigh-resolution OCT and deep-penetration OCT at wavelengths of approximately 1050 nm. Important functional extensions comprise Doppler OCT/OCT angiography, polarization-sensitive OCT, and adaptive optics OCT., Results: High-precision PCI biometry has found extensive applications in cataract surgery and in research on intraocular lens design. Optical coherence tomography, especially in the second-generation variant of FD OCT, is now indispensable for ocular diagnostics in general and for retinal diagnostics in particular; 1050 nm OCT shows improved penetration into deeper layers like the choroid., Conclusions: The contributions of the Vienna research group helped to establish PCI biometry and FD OCT as the gold standards in their respective fields.

Purpose: To analyze choroidal, Sattler's, and Haller's layer thickness maps in age-related macular degeneration (AMD) patients having eyes with bilateral large drusen and pigment changes (intermediate AMD), in patients having intermediate AMD eyes with neovascular fellow eyes (nAMD), and in healthy subjects using three-dimensional (3D) 1060-nm optical coherence tomography (OCT)., Methods: Automatically generated choroidal thickness (ChT), retinal thickness, and Sattler's and Haller's layer thickness maps were statistically analyzed in 67 subjects consisting of intermediate AMD (n = 21), intermediate AMD (n = 22) with fellow nAMD eyes (n = 22), and healthy eyes (n = 24) with no age and axial eye length difference between groups of eyes (P > 0.05, ANOVA). Eyes were imaged by a prototype high-speed (60,000 A-scans/s) spectral-domain 3D 1060-nm OCT over a 36° × 36° field of view., Results: The mean ± SD (μm) subfoveal ChT for healthy subjects and for bilateral intermediate AMD, unilateral intermediate AMD, and their nAMD fellow eyes was 259 ± 95 and 222 ± 98, 149 ± 60, and 171 ± 78, respectively. Choroidal thickness maps demonstrated significant submacular thinning in unilateral intermediate AMD in comparison to healthy and bilateral intermediate AMD eyes (P < 0.001, ANOVA, post hoc P < 0.001 and P < 0.05, respectively). Sattler's and Haller's layers were thinnest in intermediate AMDs that presented with nAMD fellow eyes (Kruskal-Wallis test P < 0.01). For the choroid and its sublayers, there was no difference between the intermediate AMD eyes and their fellow nAMD eyes (paired testing, P < 0.05)., Conclusions: The 3D 1060-nm OCT choroidal imaging visualized significant changes in choroidal, Sattler's, and Haller's layer thickness in relation to the progression of AMD. This may be important for understanding the choroidopathy in the pathophysiology of AMD., (Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.)

Purpose: To map and analyze choroidal thickness (ChT) in AMD patients with reticular pseudodrusen (RPD) using three-dimensional (3D) 1060-nm optical coherence tomography (OCT)., Methods: Fifty eyes from 25 patients with RPD were grouped according to the severity of AMD and the presence of RPD. All patients were imaged by high-speed (60,000 A-scans/s) 3D 1060-nm OCT over a 36 × 36° field of view. Choroidal thickness maps were automatically generated and compared with RPD areas visualized by fundus autofluorescence and infrared imaging. Retinal thickness maps, ChT maps, Haller's and Sattler's layer thickness were statistically analyzed between groups., Results: The mean ± SD (micrometers) subfoveal ChT was 201 ± 88 μm, 145 ± 48 μm, and 271 ± 130 μm for dry AMD with RPD, wet AMD with RPD, and eyes with wet AMD and no RPD, respectively. Choroidal thickness maps demonstrated the most significant choroidal thinning within eyes with wet AMD and RPD. Sattler's and Haller's layer thickness differed across the Early Treatment Diabetic Retinopathy Study grid when compared between eyes with and without RPD. Within eyes with RPD, ChT maps visualized that ChT was thicker below RDP areas than non-RPD areas., Conclusions: The 3D 1060-nm OCT choroidal maps over a large field of view offer noninvasive visualization for demonstrating local thickening correlation with RPD within each eye and overall thinning owing to AMD severity and RPD. This choroidal thinning was most striking in Sattler's layer, suggesting a choroidopathy of this vascular layer.

Purpose: To visualize the precorneal tear film with ultrahigh-resolution spectral domain optical coherence tomography, enabling quantification of tear film thickness in healthy subjects., Methods: A custom-built spectral domain optical coherence tomography system comprising a broadband titanium:sapphire laser operating at 800 nm and a high-speed charge coupled device (CCD) camera with a read-out rate of 47 kHz was used for measurement of precorneal tear film thickness. The system provides a theoretical axial resolution of 1.2 μm in tissue. The signal-to-noise ratio close to the zero delay was measured with 94 dB. A total of 26 healthy subjects were included in this study. Measurement was started immediately after blinking and averaged over a period of 1 second. In a subset of eight healthy subjects, the reproducibility of the approach was studied by measuring the tear film thickness every 10 minutes over 1 hour., Results: The average central tear film thickness of the measured population was 4.79 ± 0.88 μm. Reproducibility was very high, with an intraclass correlation coefficient of 0.97. A breakup of the tear film was observed in one subject after 14 seconds., Conclusions: Our data indicate that the human precorneal tear film can be measured with excellent reproducibility using ultrahigh-resolution optical coherence tomography. This technique may be a valuable tool in the management of dry eye syndrome.

Purpose: To map choroidal (ChT) and retinal thickness (RT) in patients with diabetes type 1 with and without maculopathy and retinopathy in order to compare them with healthy subjects using high speed 3-dimensional (3D) 1060 nm optical coherence tomography (OCT)., Methods: Thirty-three eyes from 33 diabetes type 1 subjects (23-57 years, 15 male) divided into groups of without pathology (NDR) and with pathology (DR; including microaneurysms, exudates, clinically significant macular-oedema and proliferative retinopathy) were compared with 20 healthy axial eye length and age-matched subjects (24-57 years, 9 male), imaged by high speed (60.000 A-scans/s) 3D 1060 nm OCT performed over 36° × 36° field of view. Ocular health status, disease duration, body mass index, haemoglobin-A1c, and blood pressure (bp) measurements were recorded. Subfoveal ChT, and 2D topographic maps between retinal pigment epithelium and the choroidal/scleral-interface, were automatically generated and statistically analyzed., Results: Subfoveal ChT (mean ± SD, μm) for healthy eyes was 388 ± 109; significantly thicker than all diabetic groups, 291 ± 64 for NDR, and 303 ± 82 for DR (ANOVA P < 0.004, Tukey P = 0.01 for NDR and DR). Thinning did not relate to recorded factors (multi-regression analysis, P > 0.05). Compared with healthy eyes and the NDR, the averaged DR ChT-map demonstrated temporal thinning that extended superiorly and temporal-inferiorly (unpaired t-test, P < 0.05). Foveal RT and RT-maps showed no statistically significant difference between groups (mean SD, μm, healthy 212 ± 17, NDR 217 ± 15, DR 216 ± 27, ANOVA P > 0.05)., Conclusions: ChT is decreased in diabetes type 1, independent of the absence of pathology and of diabetic disease duration. In eyes with pathology, 3D 1060 nm OCT averaged maps showed an extension of the thinning area matching retinal lesions and suggesting its involvement on onset or progression of disease.

Purpose: To map choroidal (ChT) and retinal thickness (RT) in healthy subjects and patients with diabetes with and without maculopathy using three dimensional 1060-nm optical coherence tomography (3D-1060nm-OCT)., Methods: Sixty-three eyes from 42 diabetic subjects (41-82 years of age; 11 females) grouped according to a custom scheme using Early Treatment Diabetic Retinopathy Study definitions for pathology within 1 disc-diameter of fovea (without pathology [NDR], microaneurysms [M1], exudates [M2], clinically significant macular edema [CSME]) and 16 eyes from 16 healthy age matched subjects (38-79 years of age; 11 females) were imaged by 3D-1060nm-OCT performed over a 36° × 36° field of view. Axial length, 45° fundus photographs, body mass index, plasma glucose, and blood pressure measurements were recorded. The ChT at the subfoveal location and ChT maps between RPE and the choroidal-scleral interface were generated and statistically analyzed., Results: RT maps show thinning in the NDR group but an increase in thickness with increasing maculopathy in the temporal and central regions (unpaired t-test; P < 0.05). ChT mapping of all diabetic patients revealed central and inferior thinning compared to healthy eyes (unpaired t-test; P < 0.001). Subfoveal ChT (mean ± SD) for healthy eyes was 327 ± 74 μm, which was significantly thicker than all diabetic groups (214 ± 55 μm for NDR, 208 ± 49 μm for M1, 205 ± 54 μm for M2, and 211 ± 76 μm for CSME (ANOVA P < 0.001; Tukey P < 0.001)., Conclusions: 3D-1060nm-OCT has shown that the central choroid is thinner in all type 2 diabetic eyes regardless of disease stage. The choroidal thinning may exceed the magnitude of possible choriocapillaris atrophy. In contrast to the conventional assessment of pathologic thickness change in several locations, thickness maps allow investigation of the choroid over the extent of affected areas.

Purpose. To test whether the interanimal variability in susceptibility to visually induced myopia is genetically determined. Methods. Monocular deprivation of sharp vision (DSV) was induced in outbred White Leghorn chicks aged 4 days. After 4 days' DSV, myopia susceptibility was quantified by the relative changes in axial length and refraction. Chicks in the extreme tails of the distribution of susceptibility to DSV were kept and paired for breeding (high- and low-susceptibility lines). A second round of selection was then performed. The third generation of chicks, derived from the selected parents, was assessed after either monocular DSV (4 or 10 days) or lens wear. Results. After two rounds of selective breeding, the chicks from the high-susceptibility line developed approximately twice as much myopia in response to 4 days' DSV as did those from the low-susceptibility line (P < 0.001). All ocular component dimensions differed significantly (P < 0.001) between the two selected lines, both before treatment and in the responses of the treated eye. When DSV was conducted for 10 days, the relative changes in axial length and refractive error were still significantly different between the high and low lines (P < 0.001). The chicks bred for high or low susceptibility to DSV also showed significantly different responses to minus lens wear, but not to plus lens wear. Additive genetic effects explained ∼50% of the interanimal variability in response to DSV. Conclusions. Genes and environment interact to shape refractive development in chicks.

Purpose: To evaluate the performance and potential clinical role of three-dimensional (3D) 1060-nm OCT by generating choroidal thickness (ChT) maps in patients of different ages with different degrees of ametropia and axial lengths and to investigate the effect of cataract grade on OCT retinal imaging quality., Methods: Axial lengths (ALs) and 45° fundus photographs were acquired from 64 eyes (34 healthy subjects, 19 to 80 years, ametropia +3 to -10 D). 3D 1060-nm OCT was performed over a 36° × 36° field of view with ∼7-μm axial resolution and up to 70 frames/s (512 A-scans/frame). ChT maps between retinal pigment epithelium and the choroidal-scleral interface, were generated and statistically analyzed. A further 30 eyes (19 subjects), with cataracts assessed with the LOCS III scale, were imaged with 3D 1060-nm OCT and 800-nm OCT, and visualization of the posterior segment was compared qualitatively., Results: In 64 eyes, ChT maps displayed a thickness decrease with increasing AL. Subfoveal ChT was 315 ± 106 μm (mean ± SD), negatively correlated with AL (R(2) = -0.47, P < 0.001). Averaged ChT maps of eyes with AL < 23.39 mm showed an increased ChT in an area ∼1500 μm inferior, compared with subfoveal ChT. Eyes with AL > 24.5 mm showed a larger variation and a thicker ChT superiorly than inferiorly. Reduced signal strength in cataractous eyes was found in 65% of the 800-nm OCT images, but in only 10% of the 1060-nm OCT images., Conclusions: The imaging performance of 3D 1060-nm OCT is unique, producing maps that show the variation in ChT over the entire field of view, in relation to axial length. This imaging system has the potential of visualizing a novel clinical diagnostic biomarker. Compared with 800-nm OCT, it provides superior visualization of the posterior pole in cataractous eyes.

Purpose: To demonstrate high-speed, high axial resolution optical coherence tomography (OCT) at 1060 nm with penetration to the sclera. The clinical feasibility of dense, high-speed sampling for higher levels of detail at the macula and optic nerve head is explored with respect to motion artifacts., Methods: A three-dimensional (3D) OCT system making use of a high-speed camera operating at 47,000 depth scans/s was developed. The 1010- to 1080-nm wavelength band leads to 6.7 microm effective axial resolution and enables the acquisition of retinal and choroidal 130 Megavoxel volumes of human subjects within 7 seconds. Motion artifacts were reduced by numeric postprocessing techniques., Results: Drift motion artifacts could be suppressed within fields up to 38 degrees x 38 degrees (approximately 1 cm(2)) using acquisition speeds of up to 74 frames/s at 512 x 512 pixel/frame. This isotropic OCT sampling of the human retina in vivo allowed reconstruction of the retinal microvasculature solely on vessel reflectivity, without the use of contrast agents, and revealed three interconnected capillary meshworks. Simultaneously in the choroid, the structure of the choriocapillaris, Sattler's layer, and Haller's layer were differentiated, and the choroidal-scleral interface was clearly delineated in densely sampled narrow- and wide-angle scans (>38 degrees). At the optic nerve head, the 3D fine structure of the lamina cribrosa and the circle of Zinn-Haller were visualized., Conclusions: OCT almost centered within the 1060-nm water transmission window significantly profits from lower scattering and allows investigation of the retina and choroid at an unprecedented combination of penetration and high speed at high resolution and may provide superior clinical feasibility to commercial 800-nm devices.

Purpose: To demonstrate a new generation of three-dimensional (3-D) ultrahigh-resolution optical coherence tomography (UHR OCT) technology for visualization of macular diseases., Methods: One hundred forty eyes with a distinct disease in each of the posterior pole compartments were examined with 3-D UHR OCT. 3-D imaging was performed with a high axial resolution of 3 mum with a compact, commercially available, ultra-broad-bandwidth (160 nm) titanium:sapphire laser at a video rate of up to 25 B-scans/s. Each tomogram consisted of 1024 x 1024 pixels, resulting in 25 megavoxels/s., Results: 3-D UHR OCT offers high-precision 3-D visualization of macular diseases at all structural levels. The UHR modality allows identification of the contour of the hyaloid membrane, tractive forces of epiretinal membranes, and changes within the inner limiting membrane. The system provides quality 3-D images of the topographic dynamics of traction lines from the retinal surface down to the level of the photoreceptor segments. Intraretinal diseases are identified by their specific location in different layers of the neurosensory ultrastructure. Photoreceptor inner and outer segments are clearly delineated in configuration and size, with a characteristic peak in the subfoveal area. The microarchitecture of choroidal neovascularization is distinctly imaged, related leakage can be identified, and the volume can be quantified., Conclusions: High-speed UHR OCT offers unprecedented, realistic, 3-D imaging of ocular diseases at all epi-, intra- and subretinal levels. A complete 3-D data set of the macular layers allows a comprehensive analysis of focal and diffuse diseases, as well as identification of dynamic pathomechanisms.

Purpose: To assess photoreceptor morphology in patients with Stargardt's disease and fundus flavimaculatus using ultrahigh-resolution optical coherence tomography (UHR-OCT) and correlate it with visual acuity (VA)., Methods: This was a prospective observational case series. Fourteen patients with Stargardt's disease (nine women, five men; average age, 39 years; range, 27-53) were examined. A clinically viable UHR-OCT system employing a new, compact titanium sapphire laser was used, enabling a 3-microm axial resolution in the retina. All patients received a full ophthalmic examination, including fluorescein angiography. Outcome was judged by central transverse photoreceptor loss, central foveal thickness, VA, central atrophy according to fluorescein angiography, and fundus autofluorescence., Results: UHR-OCT was capable of visualizing and quantifying regions of central transverse photoreceptor (PR) loss. All Stargardt patients with central atrophy had a complete loss of the central photoreceptor layer in the foveal region (mean transverse photoreceptor loss, 4390 +/- 2270 microm; range, 530-9240 microm). Patients without clinically evident central atrophy had an intact photoreceptor layer centrally, but had small, focal parafoveal defects. A correlation was detected between VA and transverse PR loss (Spearman rho=-0.60, P=0.03), which was confirmed on logistic regression analysis (R2=0.49, P=0.0001). Central foveal thickness was reduced in patients with Stargardt's disease (85 +/- 40 microm; range, 58-280 microm). The correlation was statistically significant with VA (Spearman rho=0.43, P=0.04), but not with transverse PR loss (Spearman rho=-0.23, P >>0.05). Linear regression analysis showed a statistically significant association of central foveal thickness with VA (R2=0.51, P=0.0001), but not with transverse PR loss (P >>0.05). The extent of atrophy seen in fluorescein angiography correlated with VA and transverse PR loss (Spearman rho=-0.51, P=0.007; Spearman rho=0.77, P=0.0001). Similar correlations were found with the maximum transverse diameter of fundus autofluorescence (Spearman rho=-0.72, P=0.008; Spearman rho=0.77, P=0.003)., Conclusions: Ultrahigh-resolution OCT demonstrates excellent visualization of intraretinal morphology and enables quantification of the photoreceptor layer. Thus, for the first time, an in vivo visualization and quantification of transverse, central photoreceptor loss and correlation with visual function is possible. Lower VA corresponds to a greater transverse photoreceptor loss, which also correlates with the extent of changes seen in fluorescein angiography and in fundus autofluorescence. Furthermore, reduced retinal thickness (i.e., atrophy of retinal layers) does not correlate with the transverse extent of PR loss. Thus, it seems that although there may be progressive atrophy of intraretinal layers, an intact photoreceptor layer leads to better VA. UHR-OCT may present a viable alternative to the assessment of central visual function, due to the easy, objective, and noninvasive data acquisition. Therefore, UHR-OCT could be of future use in judging patients' prognoses in Stargardt's disease.

Purpose: To compare ultrahigh-resolution optical coherence tomography (OCT) cross-sectional images of the pig retina with histology, to evaluate the potential of ultrahigh-resolution OCT for enhanced visualization of intra- and subretinal structures., Methods: Ultrahigh-resolution OCT images were acquired with 1.4- micro m axial x 3- micro m transverse resolution from in vitro posterior eyecup preparations of the domestic pig. Frozen sections were obtained in precise alignment with OCT tomograms, by using major blood vessels as orientation markers and were counterstained with cresyl violet or unstained and examined by differential interference contrast microscopy. Micrographs from histologic sections were linearly scaled to correct for tissue shrinkage and compared with OCT tomograms., Results: In the proximal retina, ultrahigh-resolution OCT signal bands directly corresponded to the main retinal layers. For the wavelength region used ( approximately 800 nm), axodendritic layers (nerve fiber layer, inner and outer plexiform layers) were more reflective than cell body layers (ganglion cell layer, inner nuclear layer, outer nuclear layer). In the distal retina, substructures of the photoreceptor layer such as the interface between inner and outer segments were visualized, and the retinal pigment epithelium, the choriocapillaris, and superficial choroid layers were resolved. In addition, the time sequence of a retinal detachment event was monitored by ultrahigh-resolution OCT., Conclusions: In vitro ophthalmic ultrahigh-resolution OCT imaging reveals retinal morphology with unprecedented detail. The specific assignment of OCT signal patterns to retinal substructures provides a basis for improved interpretation of in vivo ophthalmic OCT tomograms of high clinical relevance.

Purpose: The pathophysiology and pathogenesis of myopia are still a matter of controversy. Exaggerated longitudinal eye growth is assumed to play an important role in the development of myopia. A significant correlation between refraction and amount of near-work has been reported. However, current knowledge of changes of axial eye length with accommodation is limited because clinical ultrasound biometry does not provide the precision and resolution required to thoroughly investigate these phenomena., Methods: Partial coherence interferometry (PCI), a noninvasive biometric technique, uses laser light with short coherence length in combination with interferometry to achieve precision in the micrometer to submicrometer range and resolution of 10 microm. In the present study this technique was used to investigate axial eye length changes in 11 emmetropic and 12 myopic eyes during monocular fixation at the far and near point. In 7 subjects, the contralateral eye has also been measured to investigate interocular differences in eye elongation., Results: All investigated eyes elongated during accommodation. This elongation was more pronounced in emmetropes than in myopes (P < 0.001). Mean accommodation-induced eye elongations of 12.7 microm (range, 8.6-19.2 microm) and 5.2 microm (range, 2.1-9.5 microm), corresponding to a dioptric change of approximately -0.036 D and -0.015 D, were obtained for emmetropes and myopes. No significant difference in accommodative amplitudes between groups (5.1 +/- 1.2 D [range, 3.8-7.1 D] versus 4.1 +/- 2.0 D [range, 1.0-7.1 D]; P = 0.14) was detected. No significant interocular difference in accommodation-induced eye elongation was revealed (P = 0.86). Also, a mean backward movement of the posterior lens pole of 38 microm (range, 9-107 microm) was observed in both study groups., Conclusions: The detected eye elongation can be explained by the accommodation-induced contraction of the ciliary muscle, which results in forward and inward pulling of the choroid, thus decreasing the circumference of the sclera, and leads to an elongation of the axial eye length. Finally, it was demonstrated that PCI, in contrast to clinical ultrasound, is capable of characterizing eye length changes during accommodation in humans.

Purpose: To demonstrate the feasibility of measuring the anterior structures of the human eye by partial coherence interferometry and to determine its precision for eyes under normal and cycloplegic conditions., Methods: The dual-beam version of partial coherence interferometry, a recently developed noninvasive optical ranging technique, enables high resolution measurements of several intraocular distances with unprecedented precision. A modified, more sensitive scanning version of this technique was used to assess the central and peripheral corneal thickness, the anterior chamber depth, and the lens thickness of 20 healthy, emmetropic to moderately myopic eyes. Furthermore the anterior structures of three eyes were measured under cycloplegia (1% cyclopentolate) to investigate the influence on the precision of this technique after suppression of residual accommodations., Results: The mean geometric precision (standard deviation) of the measurement of the central corneal thickness was 0.29 micron (range, 0.22 micron to 0.38 micron) and 0.43 micron (range, 0.27 micron to 0.56 micron) for the peripheral corneal thickness at a distance 2 mm from its apex. The precision for measuring the anterior chamber depth and the lens thickness for fixation at infinity was 8.7 microns (range, 3.9 microns to 16.8 microns) and 8.9 microns (rang, 2.9 microns to 14.4 microns) for noncycloplegic eyes and 1.9 microns (range, 1.7 microns to 2 microns) and 1.4 microns (range, 0.7 micron to 1.8 microns) for cycloplegic eyes, respectively., Conclusions: The dual-beam partial coherence interferometry enables fast, noninvasive, submicrometer precision biometry of the anterior segment of the eye. The precision of determining the anterior chamber depth and the lens thickness is more than one order of magnitude better than that of the currently used ultrasound and optical techniques, and it can be improved by a factor of 5 by using cycloplegia.

Purpose: To examine the applicability of the recently developed laser Doppler interferometry technique for measuring the axial length of cataract eyes in a realistic clinical situation. To determine the performance of the instrument as a function of cataract grade. To compare the results to those of ultrasound methods., Methods: A total of 196 cataract eyes of 100 patients were examined. The axial eye length was determined by laser Doppler interferometry and by two different ultrasound techniques, the applanation technique and the immersion technique. The cataract grade was determined by a commercial instrument that measures backscattered light., Results: Laser Doppler interferometry worked very well except in the cases of the highest cataract grades (4% of the eyes of this study were not measurable because of a too-high lens density). Only 3.5% of the other eyes were not measurable because of fixation problems of the patients. The precision of laser Doppler interferometry is not influenced by the cataract grade (except the highest grade). The standard deviation of the geometric eye length is approximately 20 microns. Linear regression analysis revealed a very good correlation of laser Doppler interferometry and ultrasonic measurements, but a systematic difference was found. The eye lengths measured by laser Doppler interferometry were about 0.18 mm longer than those measured by the immersion technique and about 0.47 mm longer than those measured by the applanation technique., Conclusion: These differences are attributed to the laser Doppler interferometry results including the retinal thickness and indentation of the cornea by the applanation technique. The main advantages of the laser Doppler interferometry technique are high precision, high accuracy, and more comfort for the patient because it is a noncontact method, anesthesia is unnecessary, and the risk of corneal infection is avoided.

The laser Doppler interferometry (LDI) technique, which was recently developed for axial eye length measurement, has been modified to measure the corneal thickness of the human eye in vivo. High accuracy is achieved. The standard deviation of the technique is about 7 microns, and improvement by a factor of 5 is possible. First comparisons with a usual slit lamp pachometer show a general agreement but a systematic difference of about 20 microns. Possible reasons for this discrepancy are discussed. Finally, the new method is compared to standard optical and ultrasound pachometry from a theoretical point of view, and advantages and drawbacks of the various techniques are discussed.