Relation between retinal vessel diameter and posterior segment optical coherence tomography variables in middle-aged Caucasians: the Northern Finland Birth Cohort Eye Study.

AIMS: Studying the relationship between retinal vessel diameter (RVD) with (1) macular thickness and volume, (2) retinal nerve fibre layer (RNFL), (3) ganglion cell-inner plexiform layer (GC-IPL) and (4) optic nerve head (ONH) in a population cohort of middle-aged Caucasians. METHODS: We collected data from 3070 individuals. We used a semiautomated computer-assisted programme to measure central retinal arteriolar equivalent and central retinal venular equivalent. Macular and ONH parameters were assessed by optical coherence tomography. RESULTS: Data from 2155 persons were analysed. A larger RVD was associated with a thicker macula and increased macular volume; each SD increase in average macular thickness and volume was associated with a 3.28 µm and a 3.19 µm increase in arteriolar diameter and a 5.10 µm and a 5.08 µm increase in venular diameter, respectively (p<0.001 for all). A larger rim area, greater GC-IPL and RNFL thicknesses were associated with larger RVD; each SD increase in rim area, GC-IPL thickness and RNFL thickness was associated with a 1.21 µm, 2.68 µm and a 3.29 µm increase in arteriolar diameter and a 2.13 µm, 4.02 µm and 5.04 µm increase in venular diameter, respectively (p<0.001 for all). CONCLUSIONS: Increased macular thickness, macular volume, GC-IPL thickness, RNFL thickness and optic nerve rim area were associated with larger RVDs in all subjects. This study clarified the anatomical correlations between both macular and ONH parameters with RVD for middle-aged Caucasians; these can represent a basis for further studies investigating the vascular aetiology of eye diseases.

Posterior Segment Visualization in Eyes With Small-Aperture Intraocular Lens.

PURPOSE: To evaluate the posterior segment visualization in patients with small-aperture intraocular lens (IOL) implantation. METHODS: In this prospective, comparative case series, 15 patients who had unilateral implantation of the small-aperture IOL in their non-dominant eyes were recruited. Their fellow eyes were pseudophakic with a monofocal IOL in 14 patients and phakic in 1 patient. All underwent bilateral posterior segment clinical investigations including fundus photography, threshold perimetry, and optical coherence tomography of the posterior pole including optic nerve head. The results from these investigations were graded by a clinician masked to the laterality and type of IOL. Patient 11 developed postoperative endophthalmitis 4 weeks following cataract surgery with implantation of a small-aperture IOL and underwent pars plana vitrectomy. The intraoperative view of the posterior segment was subjectively evaluated by the retinal surgeon. RESULTS: All 15 patients had successful image captures with all clinical investigative tools with no differences in image quality detected between the images obtained from the monofocal pseudophakic and small-aperture IOL eyes. The small-aperture IOL did not subjectively obstruct the intraoperative view for the retinal surgeon during pars plana vitrectomy. CONCLUSIONS: Standard posterior segment investigations including non-mydriatic fundus photography, optical coherence tomography, and automated perimetry can be safely and effectively performed in eyes with small-aperture IOLs. There is no difference in the image quality. [J Refract Surg. 2019;35(8):538-542.].

In vivo imaging of the fibrillar architecture of the posterior vitreous and its relationship to the premacular bursa, Cloquet's canal, prevascular vitreous fissures, and cisterns.

PURPOSE: To describe the fibrillar architecture of the posterior cortical vitreous and identify variations across eyes of different axial lengths in vivo. METHODS: Sixty-four eyes of 32 subjects were examined with swept-source optical coherence tomography (SS-OCT). Grading of vitreous degeneration, presence of vitreous cisterns/lacunae, posterior hyaloid status, directionality of vitreous fibers and their relations to vitreous spaces, and lamellar reflectivity of the posterior vitreous were assessed. RESULTS: A consistent pattern of fibrillar organization was discovered. Eyewall parallel fibers formed a dense meshwork over the retinal surface and fibers oriented in a perpendicular fashion to this meshwork were found to envelop the various vitreous spaces, intersecting at variable angles of insertion to the eyewall parallel fibers. Lamellar reflectivity suggestive of splitting of the cortical fibrillar meshwork was detected in 27 eyes (42%) with 56% of these eyes demonstrating perpendicularly oriented intersecting fibers. Fifty-six percent of eyes with lamellar reflectivity had an axial length > 25 mm. CONCLUSION: SS-OCT imaging revealed fibrillar organization of the posterior vitreous. Eye wall parallel hyperreflectivity of cortical vitreous was a universal finding. This pattern is suggestive of a splitting of cortical vitreous tissue and may represent a precursor to vitreoschisis. Perpendicular fibers appear to be important constituents of the walls of the various liquid vitreous spaces.

Ocular Biometric Diurnal Rhythms in Emmetropic and Myopic Adults.

Purpose: To investigate diurnal variations in anterior and posterior segment biometry and assess differences between emmetropic and myopic adults. Methods: Healthy subjects (n = 42, 23-41 years old) underwent biometry and spectral-domain optical coherence tomography imaging (SD-OCT) every 4 hours for 24 hours. Subjects were in darkness from 11:00 PM to 7:00 AM. Central corneal thickness, corneal power, anterior chamber depth, lens thickness, vitreous chamber depth, and axial length were measured. Thicknesses of the total retina, photoreceptor outer segments + RPE, photoreceptor inner segments, and choroid over a 6-mm annulus were determined. Results: All parameters except anterior chamber depth demonstrated significant diurnal variations, with no refractive error differences. Amplitude of choroid diurnal variation correlated with axial length (P = 0.05). Amplitude of axial length variation (35.71 ± 19.40 µm) was in antiphase to choroid variation (25.65 ± 2.01 µm, P < 0.001). The central 1-mm retina underwent variation of 5.03 ± 0.23 µm with a peak at 12 hours (P < 0.001), whereas photoreceptor outer segment + RPE thickness peaked at 4 hours and inner segment thickness peaked at 16 hours. Diurnal variations in retina and choroid were observed in the 3- and 6-mm annuli. Conclusions: Diurnal rhythms in anterior and posterior segment biometry were observed over 24 hours in adults. Differences in baseline parameters were found between refractive error groups, and choroid diurnal variation correlated with axial length. The retina and choroid exhibited diurnal thickness variations in foveal and parafoveal regions.

Retinal imaging analysis based on vessel detection.

With an increase in the advancement of digital imaging and computing power, computationally intelligent technologies are in high demand to be used in ophthalmology cure and treatment. In current research, Retina Image Analysis (RIA) is developed for optometrist at Eye Care Center in Management and Science University. This research aims to analyze the retina through vessel detection. The RIA assists in the analysis of the retinal images and specialists are served with various options like saving, processing and analyzing retinal images through its advanced interface layout. Additionally, RIA assists in the selection process of vessel segment; processing these vessels by calculating its diameter, standard deviation, length, and displaying detected vessel on the retina. The Agile Unified Process is adopted as the methodology in developing this research. To conclude, Retina Image Analysis might help the optometrist to get better understanding in analyzing the patient's retina. Finally, the Retina Image Analysis procedure is developed using MATLAB (R2011b). Promising results are attained that are comparable in the state of art.

Past, Present, and Future Concepts of the Choroidal Scleral Interface Morphology on Optical Coherence Tomography.

The choroid is the most vascular tissue in the eye and it has been implicated in the pathophysiology of a variety of ocular diseases. A new era of research in the choroid began with the improved ability to visualize this layer and its inner and outer boundaries using spectral domain optical coherence tomography (OCT) with enhanced depth imaging and swept source OCT. The accuracy and precision of qualitative and quan-titative assessments of the choroidal layer support the potential use of OCT-derived choroidal parameters for diagnosis, monitoring of disease progression, planning surgical access, and evaluating treatment response. Although there is increasing interest in measuring choroidal thickness, there is currently no consensus nomenclature to classify choroidal layers and boundaries. Furthermore, the definition and description of the choroidal scleral interface is inconsistent in the literature, contributing to interstudy variation in choroidal thickness measurements. The purpose of this review is to provide an overview of the literature on the definition of choroidal layers and choroidal scleral boundary, review the discrepan-cies, and harmonize the terminology so that a consensus nomenclature can be proposed.

Calculation of posterior chamber intraocular lens (IOL) size and dioptric power for use in pet rabbits undergoing phacoemulsification.

OBJECTIVES: To calculate the size and dioptric power of a posterior chamber intraocular lens (IOL) to achieve emmetropia in adult rabbits and to compare the dioptric power calculation results using a proprietary predictive formula to a retinoscopy-based method. ANIMALS STUDIED: Three wild rabbit cadavers, seven pet rabbits with cataracts and ten healthy pet rabbits. MATERIALS AND METHODS: Implant size was calculated using a capsular tension ring (CTR) (Acrivet® , Berlin, Germany). Published and cadaveric biometric data were used in the predictive formula. An IOL power-escalation study compared the predicted values to the refraction results of one pet rabbit (P1) fitted with a + 41D canine IOL (Acrivet® ) and six pet rabbits (P2-P7) fitted with prototype IOLs (Acrivet® ). Retinoscopy of 10 healthy pet rabbits served as controls. RESULTS: A 13.5 mm CTR fitted in all rabbits and permitted the use of a 13 mm IOL. The predicted IOL power ranged between +24D and +25D. The +41D IOL resulted in a refraction error of +8D. Progressive recalculation through a calibration formula led to the insertion of three +49D IOLs in two pet rabbits and a refraction of +6D to +8D, followed by seven +58D IOLs in four pet rabbits and a refraction median of 0D (range: -1.5D to +1D). CONCLUSIONS: A 13 mm prototype IOL of +58D achieves emmetropia and is of adequate size for rabbits. The combined use of a CTR and retinoscopy is a useful method to calculate the size and refractive power of a new, species-specific, veterinary IOL.

Anterior and posterior segment parameters measured with Fourier domain optical coherence tomography in photopic and scotopic conditions.

PURPOSE: To compare anterior and posterior segment parameters measured with the iVue-100 optical coherence tomography (OCT) in photopic and scotopic conditions. METHODS: Central and peripheral corneal thickness, retinal nerve fiber layer and macula thickness were measured using the iVue-100 OCT in 47 healthy individuals at a higher education institution in photopic (958 lux) and scotopic (0.03 lux) conditions. RESULTS: As the lighting conditions changed from scotopic to photopic, a significant change in pupil size was noted (P < 0.001). However, there was no significant difference in central corneal thickness measurements with this change in surrounding illumination with only the temporal peripheral corneal area showing a significant difference (3.44 µm thinner). No significant differences were found in the retinal nerve fiber layer thickness. A significant decrease in the reading was noted in only the inferior (P = 0.05) and temporal (P = 0.05) inner macula area. CONCLUSION: Change in the ambient lighting conditions does not result in a clinically significant difference in corneal, retinal nerve fiber layer, and macula thickness when measured with the iVue-100 OCT.

Whole eye segment imaging and measurement with dual-channel spectral-domain OCT.

BACKGROUND AND OBJECTIVES: To image and measure whole eye segments using dual-channel spectral-domain optical coherence tomography (SD-OCT) and to compare the results with those from the IOLMaster (Carl Zeiss Meditec, Dublin, CA). PATIENTS AND METHODS: Twenty eyes of 20 volunteers were recruited. Ocular dimensions, including cornea thickness, anterior chamber depth (ACD), lens thickness, anterior lens surface curvature, and axial length (AL), were calculated. The reproducibility of SD-OCT measurements, statistical significance of inter-instrument difference, correlation, and agreement were evaluated. RESULTS: No significant differences were found between independent SD-OCT measurements (P > .05). The ACD and AL measured with IOLMaster were significantly shorter than those from SD-OCT (P < .001). There were high correlations and agreements in ACD (r = 0.994; 95% limits of agreement [LOA], 0.131-0.223 mm) and AL (r = 0.998; 95% LOA, 0.678-0.853 mm) between the two methods. CONCLUSION: Dual-channel SD-OCT was demonstrated to have good repeatability in imaging and measuring whole eye segments. The results had high correlations and agreements with those from the IOLMaster.

The suprachoroidal pathway: a new drug delivery route to the back of the eye.

The development of safe and convenient drug delivery strategies for treatment of posterior segment eye diseases is challenging. Although intravitreal injection has wide acceptance amongst clinicians, its use is associated with serious side-effects. Recently, the suprachoroidal space (SCS) has attracted the attention of ophthalmologists and pharmaceutical formulators as a potential site for drug administration and delivery to the posterior segment of the eye. This review highlights the major constraints of drug delivery to the posterior eye segment, key anatomical and physiological features of the SCS and drug delivery applications of this route with emphasis on microneedles along with future perspectives.

Anterior and posterior corneal curvature: normal values in healthy Iranian population obtained with the Orbscan II.

The objective of study was to determine the normative values of anterior and posterior best fit sphere (A-BFS and P-BFS) measured with Orbscan II Topography System. In this cross-sectional study, patients (age range: 18-40 years) referred to the Khatam Eye Hospital (Mashhad, Iran) were put in an observational cross-sectional study. The A-BFS and P-BFS were measured with the Orbscan II. The differences between genders, between right and left eyes, and age-related changes were evaluated. A total of 977 healthy participants consisted of 614 female and 363 male subjects aged 18-35 years participated. The average A-BFS in our study population was recorded as 43.060 ± 1.541 D (median: 43.00 D, mode: 43.10 D, range: 38.80-55.80 D). The average P-BFS in our study population was recorded as 52.702 ± 2.190 D (median: 52.60 D, mode: 53.10 D range: 46.9-62.20 D). The A-BFS and P-BFS were respectively 42.753 ± 1.629 and 52.327 ± 2.376 D in males and 43.242 ± 1.457 and 52.924 ± 2.041 D in females, which were statistically different between the genders (P < 0.001). However, A-BFS and P-BFS were not statistically different between right and left eyes (P = 0.649 and P = 0.688 respectively). In addition, A-BFS and P-BFS were not correlated with the age (r = 0.038, P = 0.096 and r = -0.142, P = 0.178 respectively). Considering 95 % confidence interval, A-BFS less than 43.13 D and greater than 42.99 D and P-BFS less than 52.80 D and greater than 52.60 D would be considered abnormal. Detailed description and analysis of A-BFS and P-BFS with Orbscan demonstrated that the obtained average value of BFS were higher in male than female and did not change with increasing age.

Visualization of the posterior vitreous with dynamic focusing and windowed averaging swept source optical coherence tomography.

PURPOSE: To survey the anatomic structures seen in the posterior vitreous using a newly developed technique, dynamic focusing and windowed averaging swept source optical coherence tomography. DESIGN: A cross-sectional study of subjects without a history of eye disease or posterior vitreous detachment. METHODS: A focused illumination beam was swept through the scan depth during 96 successive B-scans and the corresponding most highly resolved portion of each scan was used to make an averaged composite image. The main outcome measures were the frequency and interconnectedness of anatomic features visualized. RESULTS: There were 44 eyes of 25 subjects, who ranged in age from 23 to 62. An optically empty space was seen above the macula in all eyes, and corresponded to the premacular bursa. Above the optic nerve head was a conical space corresponding to the area of Martegiani. The 2 areas were interconnected in 25 cases (56.8%). Anterior to the premacular bursa was another lacuna, named the supramacular bursa, that was separate from the premacular bursa in horizontal scans centered on the fovea and was found in 38 eyes (86.4%). Both the supramacular and premacular bursae coursed anteriorly and in 21 of the 38 eyes (55.3%) were seen to interconnect. CONCLUSIONS: The anatomic arrangement of the vitreous is consistent in living eyes with no posterior vitreous detachment, and does not correspond precisely to that described from dissection studies of autopsy specimens. The constancy of the specific findings suggests there may be some beneficial effect from the architectural structure of the vitreous that enhances evolutionary fitness.

Computational modeling of drug distribution in the posterior segment of the eye: effects of device variables and positions.

A computational model was developed to simulate drug distribution in the posterior segment of the eye after intravitreal injection and ocular implantation. The effects of important factors in intravitreal injection such as injection time, needle gauge and needle angle on the ocular drug distribution were studied. Also, the influences of the position and the type of implant on the concentration profile in the posterior segment were investigated. Computational Fluid Dynamics (CFD) calculations were conducted to describe the 3D convective-diffusive transport. The geometrical model was constructed based on the human eye dimensions. To simulate intravitreal injection, unlike previous studies which considered the initial shape of the injected drug solution as a sphere or cylinder, the more accurate shape was obtained by level-set method in COMSOL. The results showed that in intravitreal injection the drug concentration profile and its maximum value depended on the injection time, needle gauge and penetration angle of the needle. Considering the actual shape of the injected solution was found necessary to obtain the real concentration profile. In implant insertion, the vitreous cavity received more drugs after intraocular implantation, but this method was more invasive compared to the periocular delivery. Locating the implant in posterior or anterior regions had a significant effect on local drug concentrations. Also, the shape of implant influenced on concentration profile inside the eye. The presented model is useful for optimizing the administration variables to ensure optimum therapeutic benefits. Predicting and quantifying different factors help to reduce the possibility of tissue toxicity and to improve the treatment efficiency.

Megahertz ultra-wide-field swept-source retina optical coherence tomography compared to current existing imaging devices.

BACKGROUND: To investigate the image quality of wide-angle cross-sectional and reconstructed fundus images based on ultra-megahertz swept-source Fourier domain mode locking (FDML) OCT compared to current generation diagnostic devices. METHODS: A 1,050 nm swept-source FDML OCT system was constructed running at 1.68 MHz A-scan rate covering approximately 70° field of view. Twelve normal eyes were imaged with the device applying an isotropically dense sampling protocol (1,900 × 1,900 A-scans) with a fill factor of 100 %. Obtained OCT scan image quality was compared with two commercial OCT systems (Heidelberg Spectralis and Stratus OCT) of the same 12 eyes. Reconstructed en-face fundus images from the same FDML-OCT data set were compared to color fundus, infrared and ultra-wide-field scanning laser images (SLO). RESULTS: Comparison of cross-sectional scans showed a high overall image quality of the 15× averaged FDML images at 1.68 MHz [overall quality grading score: 8.42 ± 0.52, range 0 (bad)-10 (excellent)] comparable to current spectral-domain OCTs (overall quality grading score: 8.83 ± 0.39, p = 0.731). On FDML OCT, a dense 3D data set was obtained covering also the central and mid-peripheral retina. The reconstructed FDML OCT en-face fundus images had high image quality comparable to scanning laser ophthalmoscope (SLO) as judged from retinal structures such as vessels and optic disc. Overall grading score was 8.36 ± 0.51 for FDML OCT vs 8.27 ± 0.65 for SLO (p = 0.717). CONCLUSIONS: Ultra-wide-field megahertz 3D FDML OCT at 1.68 MHz is feasible, and provides cross-sectional image quality comparable to current spectral-domain OCT devices. In addition, reconstructed en-face visualization of fundus images result in a wide-field view with high image quality as compared to currently available fundus imaging devices. The improvement of >30× in imaging speed over commercial spectral-domain OCT technology enables high-density scan protocols leading to a data set for high quality cross-sectional and en-face images of the posterior segment.

Proposed lexicon for anatomic landmarks in normal posterior segment spectral-domain optical coherence tomography: the IN•OCT consensus.

PURPOSE: To develop a consensus nomenclature for the classification of retinal and choroidal layers and bands visible on spectral-domain optical coherence tomography (SD-OCT) images of a normal eye. DESIGN: An international panel with expertise in retinal imaging (International Nomenclature for Optical Coherence Tomography [IN • OCT] Panel) was assembled to define a consensus for OCT imaging terminology. PARTICIPANTS: A panel of retina specialists. METHODS: A set of 3 B-scan images from a normal eye was circulated to the panel before the meeting for independent assignment of nomenclature to anatomic landmarks in the vitreous, retina, and choroid. The outputs were scrutinized, tabulated, and used as the starting point for discussions at a roundtable panel meeting. The history of anatomic landmark designations over time was reviewed for the various cellular layers of the ocular structures that are visible by SD-OCT. A process of open discussion and negotiation was undertaken until a unanimous consensus name was adopted for each feature. MAIN OUTCOME MEASURES: Definitions of normal eye features showed by SD-OCT. RESULTS: Definitions for various layers changed frequently in the literature and were often inconsistent with retinal anatomy and histology. The panel introduced the term "zone" for OCT features that seem to localize to a particular anatomic region that lacks definitely proven evidence for a specific reflective structure. Such zones include the myoid, ellipsoid, and the interdigitation zones. CONCLUSIONS: A nomenclature system for normal anatomic landmarks seen on SD-OCT outputs has been proposed and adopted by the IN • OCT Panel. The panel recommends this standardized nomenclature for use in future publications. The proposed harmonizing of terminology serves as a basis for future OCT research studies.

The premacular bursa's shape revealed in vivo by swept-source optical coherence tomography.

OBJECTIVE: To resolve the controversy surrounding the shape and relationship of posterior vitreous spaces by characterizing the connections between the premacular bursa, the area of Martegiani, and Cloquet's canal. DESIGN: Comprehensive posterior vitreous maps were created using swept-source optical coherence tomography (SS OCT) in a cross-sectional study. PARTICIPANTS: The posterior vitreous of 102 eyes of 51 volunteers 21 to 54 years of age without ocular pathologic features was imaged using SS OCT. METHODS: The DRI OCT-1 Atlantis 3D SS OCT (Topcon Medical Systems, Oakland, NJ) was used to acquire scans of the posterior vitreous over an 18×18-mm area. MAIN OUTCOME MEASURES: Posterior vitreous spaces and their relationships were identified. RESULTS: The premacular bursa was identified in all 102 eyes and was found to extend superiorly beyond our scanning ability at a variable angle. No discernible superior borders could be identified. Instead, a connection of the bursa with the preoptic area of Martegiani or its extension, Cloquet's canal, was found in 101 of 102 eyes. This connection occurred at a variable distance from the optic nerve, where it formed a flat and broad superior channel. The skyward direction of this channel was found to be gravity dependent in all 14 eyes of the 7 subjects examined in various head positions. Although SS OCT was able to identify vitreous degeneration, the above changes were present in 28 eyes even without any discernible vitreous degeneration. CONCLUSIONS: The premacular bursa, also called the posterior precortical vitreous pocket, was found to continue superiorly beyond the posterior pole without a detectable border. The bursa fused broadly with the extension of the preoptic area of Martegiani, namely Cloquet's canal, or the hyaloidal tract of Eisner. These findings suggest that there is a direct anteroposterior connection between the retrolental and premacular and preoptic spaces already existent in the eyes of young adults before the occurrence of vitreous degeneration. This observation may have important implications with respect to the movement of intrinsic and extrinsic mediators between the anterior and posterior segments.

New profiles of posterior pole retinal thickness map in healthy Korean eyes measured by spectral-domain optical coherence tomography.

PURPOSE: To analyze posterior pole retinal thickness using the new Spectralis HRA + OCT protocol and compare two commercially available spectral-domain optical coherence tomography instruments (Spectralis HRA + OCT and Cirrus HD-OCT) in young healthy eyes. METHODS: Retinal thickness in 178 young healthy eyes was measured using the volume scan mode and Posterior Pole Asymmetry Analysis of the Spectralis HRA + OCT and the macular cube 512 × 128 protocol of the Cirrus HD-OCT. Topologic differences in posterior pole retinal thickness between the two spectral-domain optical coherence tomographies were compared, and the relationship between retinal thickness and age or refractive error/axial length was assessed. RESULTS: Mean retinal thickness measurements in all 9 Early Treatment Diabetic Retinopathy Study Report areas were significantly greater with the Spectralis HRA + OCT than with the Cirrus HD-OCT (P < 0.001). Retinal thickness measured with the new Spectralis HRA + OCT protocol positively correlated with refractive error (P < 0.05) and negatively correlated with axial length (P < 0.05), mainly in the temporal areas. As axial length increased and refractive error decreased, retinal thickness decreased significantly at the outer temporal areas compared with the nasal areas (P < 0.05). Foveal thickness measured with the Spectralis HRA + OCT correlated significantly with refractive error (r = -0.151; P = 0.022) and axial length (r = 0.352; P < 0.001). CONCLUSION: Posterior pole retinal thickness measurements in young healthy eyes should provide more detailed standard values for diagnosing and managing retinal disease.

Use of a combined slit-lamp SD-OCT to obtain anterior and posterior segment images in selected animal species.

OBJECTIVE: To obtain images of anterior and posterior segments of the eye using a slit-lamp (SL)/spectral domain (SD) optical coherence tomography (OCT) integrated system designed for the human eye, in the cat, dog, minipig and monkey. ANIMALS STUDIED: One healthy adult monkey, one healthy adult minipig, one healthy adult dog, one healthy adult cat, and three cats and four dogs affected by corneal or retinal diseases. PROCEDURE: A SL SCAN-1 SD-OCT, which is a slit-lamp SL-D7 that contains an integrated OCT module and a fundus viewer, was used to generate OCT images (512-2048), while simultaneously taking 'en-face' slit-lamp images (efSL). OCT images were obtained under sedation or anesthesia. These images were compared to histological retinal sections obtained from a monkey, a minipig, a dog, and a cat. RESULTS: 'en-face' slit-lamp images and OCT images of the ocular tissues were obtained allowing for the identification of different corneal and retinal layers in all animal species. Measurements of the total retinal thickness (TRT) from the inner limiting membrane to the retinal pigment epithelium were performed in various regions throughout the retina. Reduction in TRT was consistent with clinical features of retinal degeneration identified in dogs and cats. CONCLUSION: This noninvasive procedure is useful for both experimental and clinical assessments of ocular tissue damage. Images of anterior and posterior segments are readily obtained under routine clinical conditions. Future studies are warranted to establish normal OCT data in our patients with this new instrument.