Ocular Images Research Articles

Retinal Vessel Detection and Measurement for Computer-aided Medical Diagnosis

Since blood vessel detection and characteristic measurement for ocular retinal images is a fundamental problem in computer-aided medical diagnosis, automated algorithms/systems for vessel detection and measurement are always demanded. To support computer-aided diagnosis, an integrated approach/solution for vessel detection and diameter measurement is presented and validated. In the proposed approach, a Dempster-Shafer (D-S)-based edge detector is developed to obtain initial vessel edge information and an accurate vascular map for a retinal image. Then, the appropriate path and the centerline of a vessel of interest are identified automatically through graph search. Once the vessel path has been identified, the diameter of the vessel will be measured accordingly by the algorithm in real time. To achieve more accurate edge detection and diameter measurement, mixed Gaussian-matched filters are designed to refine the initial detection and measures. Other important medical indices of retinal vessels can also be calculated accordingly based on detection and measurement results. The efficiency of the proposed algorithm was validated by the retinal images obtained from different public databases. Experimental results show that the vessel detection rate of the algorithm is 100% for large vessels and 89.9% for small vessels, and the error rate on vessel diameter measurement is less than 5%, which are all well within the acceptable range of deviation among the human graders.

Iris Biometrics: Synthesis of Degraded Ocular Images

Iris recognition is a popular technique for recognizing humans. However, as is the case with most biometric traits, it is difficult to collect data that are suitable for use in experiments due to three factors: 1) the substantial amount of data that is required; 2) the time that is spent in the acquisition process; and 3) the security and privacy concerns of potential volunteers. This paper describes a stochastic method for synthesizing ocular data to support experiments on iris recognition. Specifically, synthetic data are intended for use in the most important phases of those experiments: segmentation and signature encoding/matching. The resulting data have an important characteristic: they simulate image acquisition under uncontrolled conditions. We have experimentally confirmed that the proposed strategy can mimic the data degradation factors that usually result from such conditions. Finally, we announce the availability of an online platform for generating degraded synthetic ocular data. This platform is freely accessible worldwide.

Resolution of Slit-Lamp Microscopy Photography Using Various Cameras

To evaluate the resolutions of slit-lamp microscopy photography using various cameras. Evaluation of diagnostic test or technology. Healthy subjects were imaged with these adapted cameras through slit-lamp microscopy. A total of 8 cameras, including 6 custom-mounted slit-lamp cameras and 2 commercial slit-lamp cameras, were tested with standard slit-lamp microscopy devices for imaging of the eye. Various magnifications were used during imaging. A standard resolution test plate was used to test the resolutions at different magnifications. These outcomes were compared with commercial slit-lamp cameras. The main measurements included the display spatial resolutions, image spatial resolutions, and ocular resolutions. The outcome also includes the relationships between resolution and the pixel density of the displays and images. All cameras were successfully adapted to the slit-lamp microscopy, and high-quality ocular images were obtained. Differences in the display spatial resolutions were found among cameras [analysis of variance (ANOVA), P<0.05]. Higher display resolutions were found with cameras using the high-definition multimedia interface (HDMI) compared with others, including cameras in smart phones. The display resolutions of smart phone displays were greater than cameras with video graphics array displays. The display spatial resolutions were found as a function of display pixel density (r>0.95, P<0.05) and magnification (r>0.85, P<0.05). Different image spatial resolutions were found among cameras (ANOVA, P<0.05) as a function of image pixel density (r>0.98, P<0.05) and magnification (r>0.85, P<0.05). The commercial slitlamp with a single lens reflex camera yielded the highest image spatial resolution. However, the ocular resolution through binocular viewing of the slit-lamp microscopy was found to have the highest resolution compared with the display and image spatial resolutions of all of the cameras. Several cameras can be adapted with slit-lamp microscopy for ophthalmic imaging, yielding various display and image spatial resolutions. However, the resolution seemed to not be as good as ocular viewing through the slit-lamp biomicroscope.

ASSOCIATION OF OCT ANGLE RECESS WIDTH WITH IOP RESPONSE AFTER INTRAVITREAL TRIAMCINOLONE INJECTION

A circumferential pretrabecular anatomical structure, the angle recess (AR), can be imaged with anterior segment ocular coherence tomography. AR's utility to predict ocular hypertension after intravitreal triamcinolone injection was assessed. All intravitreal triamcinolone injection recipients from 2002 to 2005 with high-resolution anterior segment ocular coherence tomography images had AR width (between the anteriormost prominence of the iris root and posterior cornea) measured by masked physicians using the caliper function of Stratus ocular coherence tomography. Intraocular pressures (IOPs) from 1 month before to 6 months after the injection were compiled for IOP rise (Δ) and maximal IOP (max), categorized as "minimal" (IOPmax < 21 mmHg and/or IOPΔ ≤ 5 mmHg), "moderate" (IOPmax 21-29 mmHg and/or IOPΔ 6-14 mmHg), or "severe" (IOPmax ≥ 30 mmHg and/or IOPΔ ≥ 15 mmHg). Linear regression and analyses of variance were applied. Twenty-six eyes satisfied the entry criteria, with 11 (42%) eyes demonstrating minimal, 11 (42%) moderate, and 4 (15%) severe IOP responses. The corresponding (mean ± SEM) AR widths were: 326 ± 31.5 μm, 281 ± 22.0 μm, and 138 ± 20.3 μm, respectively. Highly significant AR width differences existed between moderate and severe responders and between minimal and severe responders (both P < 0.004); 5 of 6 patients with IOP ≥ 29 mmHg had AR < 200 μm. These findings indicate that a potentially clinically useful relationship exists between AR width and IOP elevation accompanying intravitreal triamcinolone injection. Anterior segment screening could become a beneficial extension of ocular coherence tomography for retinal practices.

A Novel Approach to the Detection of Macula in Human Retinal Imagery

This paper demonstrates an approach to the rapid detection and extraction of macula from the images of human retina. For the diagnosis of ophthalmic pathologies, digital fundus images are becoming increasingly popular. This fact opens up the possibility of applying digital image processing techniques in ocular fundus images to facilitate and improve diagnosis in different ways. Macula is the major landmark for retinal fundus image registration and is indispensible for the quick understanding of retinal images. For the detection and subsequent extraction of macula, we first perform bit plane decomposition to the preprocessed image. The bit plane 0 and bit plane 1 are found to carry vital information of the location and boundary of macula. Then we locate the exact boundary by means of mathematical morphology. The proposed algorithm is computationally simple and does not require a prior knowledge of other retinal image features like optic disc or vasculature. The algorithm has been evaluated on a subset of MESSIDOR image database with various visual qualities. Robustness with respect to changes in the parameters of the algorithm has been examined.

An Automatic Retinal Optic Disc Segmentation Algorithm using Differential Windowing in the Polar Coordinate Domain

Blindness from glaucoma is irreversible but largely preventable if detected early. Information about optic discs can be used to examine severity of certain diseases in the human retina. A novel optic disc segmentation algorithm in the polar coordinate domain is presented in this paper. Automatic optic disc localisation, left or right eye identification, and optic disc boundary extraction are addressed in this paper. A differential windowing operation in the polar coordinate domain is introduced to extract the optic disc boundary in ocular fundus images. The proposed work provides an accurate method to detect left and right eyes using blood vessel convergence. The method is tested using the available databases and real time images, and the results are reported here. The optic disc localisation and left or right eye identification are obtained with 100% accuracy. The experimental results demonstrate the accuracy of the optic disc boundary extraction.

Ocular Volumetry Using Fast High-Resolution MRI during Visual Fixation

Volumetry may be useful for evaluating treatment response and prognosis of intraocular lesions. Phantom, volunteer, and patient studies were performed to determine whether ocular MR volumetry is reproducible. Half-Fourier single-shot RARE and FSPGR sequences at 1.5T with a 76-mm-diameter surface coil were optimized to obtain still ocular images. Volumetry accuracies of each sequence were compared with simulated subretinal phantom volumes. Ocular volumetry was performed in 15 volunteers twice in 1 week by using contiguous axial images of the globes while the subjects stared at a target, and images were acquired in 2 seconds before the subjects were instructed to blink, with this process repeated as necessary. Imaging, intraobserver, and interobserver reproducibility for volumes of the whole eyeball and anterior chamber were assessed. Ocular volumetry was also performed in 6 patients with intraocular tumors before and after treatment. The phantom study demonstrated that measurement error rates with RARE were significantly lower than with FSPGR (P<.01). The volunteer study demonstrated excellent imaging and intraobserver reproducibility of RARE volumetry for whole eyeballs and anterior chambers (P<.01). Although no interobserver differences were observed in anterior chamber volume measurement (P=.33), there was a significant difference between the 2 observers in eyeball volume measurement (P<.01). Follow-up volumetric data were useful for treatment decisions in all patients. Ocular volumetry from contiguous ultrafast RARE images obtained during visual fixation is feasible in volunteer and patient studies and is superior to FSPGR images.

Ranking Star-Shaped Valued Mappings with Respect to Shape Variability

The study of shapes is a difficult topic, but it is becoming more and more important as computer vision techniques are already crucial in many research fields. Concretely, the variability of shapes is the basis for many criteria of symptom definition in medical diagnosis. This article introduces a stochastic order to address the variability of star-shaped sets. The main properties of the order are analyzed. An example of an application to hypothesis testing in medical diagnosis is also provided. Namely, we study if there are significant differences between healthy and diseased corneal endothelia with respect to cell shapes by means of ocular images.

Clinical applications of high-resolution ocular magnetic resonance imaging

Magnetic resonance imaging (MRI) using fast sequences with subjects staring at a target can provide motion-free ocular images, and small receiver surface coils make it possible to produce ocular images with high spatial resolution. MRI using half-Fourier single-shot rapid acquisition with a relaxation enhancement sequence as a fast T2-weighted imaging yields useful images for the morphologic diagnosis of ocular diseases, and MRI using a fast spoiled gradient-recalled-echo sequence as a T1-weighted imaging yields additional information by the administration of gadolinium-based contrast material for assessing the vascularity of intraocular tumors. These ocular imaging techniques are useful for the evaluation of patients with angle closure glaucoma, congenital abnormality of ocular globes, intraocular tumors and several types of detachments, as well as patients after ocular surgery. In this pictorial essay, we demonstrate the clinical applications of fast high-resolution ocular MRI with fixation of the subjects' visual foci.

Application of Morphological Bit Planes in Retinal Blood Vessel Extraction

The appearance of the retinal blood vessels is an important diagnostic indicator of various clinical disorders of the eye and the body. Retinal blood vessels have been shown to provide evidence in terms of change in diameter, branching angles, or tortuosity, as a result of ophthalmic disease. This paper reports the development for an automated method for segmentation of blood vessels in retinal images. A unique combination of methods for retinal blood vessel skeleton detection and multidirectional morphological bit plane slicing is presented to extract the blood vessels from the color retinal images. The skeleton of main vessels is extracted by the application of directional differential operators and then evaluation of combination of derivative signs and average derivative values. Mathematical morphology has been materialized as a proficient technique for quantifying the retinal vasculature in ocular fundus images. A multidirectional top-hat operator with rotating structuring elements is used to emphasize the vessels in a particular direction, and information is extracted using bit plane slicing. An iterative region growing method is applied to integrate the main skeleton and the images resulting from bit plane slicing of vessel direction-dependent morphological filters. The approach is tested on two publicly available databases DRIVE and STARE. Average accuracy achieved by the proposed method is 0.9423 for both the databases with significant values of sensitivity and specificity also; the algorithm outperforms the second human observer in terms of precision of segmented vessel tree.

Automatic Feature Extraction from Ocular Images

Ocular images processing is an important task in: i) biometrics system based on retina and/or sclera images, and ii) in clinical ophthalmology diagnosis of diseases like various vascular disorders. We presents a general framework for image processing of ocular images with a particular view on feature extraction. The method uses the set of geometrical and texture features and based on the information of the complex vessel structure of the retina and sclera. The feature extraction contains the image preprocessing, locating and segmentation of the region of interest (ROI). The image processing of ROI and the feature extraction are proceeded, and then the feature vector is determined for the human recognition and ophthalmology diagnosis.

Visible Spectrum, Bi-Modal Ocular Biometrics

Most current ocular biometric systems are based on recognition and classification of unique iridial patterns typically captured in near infrared spectrum (NIR). However, eye images in the visible spectrum (e.g. RGB images) also reveal some iridial patterns in addition to the vascularity of the white of the eyes (mostly due to conjunctival and episcleral layers). These vascular patterns have rich and uniquely identifiable information. The combination of the aforementioned modalities provides an opportunity for bi-modal ocular biometrics using only visible spectrum captures. Multimodality improves the performance of biometric systems compared to single mode biometrics. In this work, a bi-modal ocular biometric system is described, where match scores from vasculature of the white of the eye and iris modalities are fused. We report the performance of this enhanced complementary biometric identification using UBIRIS v1 database. The proposed method, for a quality-vetted subset of UBIRIS v1 RGB ocular images, produces an area under receiver operating characteristic curve (AUC) of 0.9954 and an equal error rate (EER) of 0.0452. In comparison, individual modalities yield an AUC of 0.9822 and EER of 0.0759 for iris and an AUC of 0.9623 and an EER of 0.1022 for conjunctival vasculature. The proposed new algorithms may overcome constraints of using NIR imaging for iris and provide a better overall performance using only RGB eye images. We conclude that bi-modal iris–conjunctival fusion can improve the otherwise challenging RGB iris recognition.

Noradrenaline contracts rat retinal arterioles via stimulation of α 1A- and α 1D-adrenoceptors

The aim of this study was to characterize the α 1-adrenoceptor subtype(s) involved in the noradrenaline-induced contraction of retinal arterioles in rats. In vivo ocular fundus images were captured with a digital camera equipped with a special objective lens. By measuring changes in diameter of retinal arterioles in the fundus images, retinal vascular response was assessed. The systemic blood pressure and heart rate in the animals were also continuously recorded. Following blockade of β 1/β 2-adrenoceptors with propranolol, noradrenaline (0.03–3 μg/kg/min, i.v.) decreased the diameter of retinal arterioles and increased the mean blood pressure in a dose-dependent manner. The highest dose (3 μg/kg/min, i.v.) of noradrenaline caused a small increase in heart rate. The α 1A-adrenoceptor antagonist RS100329 (0.1 mg/kg, i.v.) and the α 1D-adrenoceptor antagonist BMY 7378 (1 mg/kg, i.v.) significantly prevented noradrenaline-induced contraction of retinal arterioles and pressor responses whereas the α 1B-adrenoceptor antagonist L-765314 (1 mg/kg, i.v.) did not. The α 1A-adrenoceptor agonist, A 61603 (0.03–0.3 μg/kg/min, i.v.), also caused contractile responses of retinal arterioles and pressor responses. These responses were almost completely prevented by RS100329 (0.1 mg/kg, i.v.), but not by BMY 7378 (1 mg/kg, i.v.). These results suggest that the contractile effects of noradrenaline on retinal arterioles and peripheral resistance vessels are, at least in part, mediated by stimulation of α 1A- and α 1D-adrenoceptors. Furthermore, it is likely that the α 1-adrenoceptor subtype(s) involved in rat vascular responses are similar in both retinal and peripheral circulation.

Role of β3-adrenoceptors in regulation of retinal vascular tone in rats

The aim of this study was to determine the role of β(3)-adrenoceptors in the action of endogenous catecholamines (adrenaline and noradrenaline) on rat retinal arterioles in vivo. Using an original high-resolution digital fundus camera, the rat ocular fundus images were captured. The diameter of retinal arterioles contained in the images was measured. Both systemic blood pressure and heart rate were recorded continuously. Adrenaline (0.3-5.0μg/kg/min, i.v.) increased the diameter of retinal arterioles, mean blood pressure and heart rate in a dose-dependent manner. Under blockade of β(1)/β(2)-adrenoceptors with propranolol (2mg/kg, i.v. bolus followed by 100μg/kg/min infusion), adrenaline decreased the diameter of retinal arterioles. Similar observation was made under treatment with the β(3)-adrenoceptor antagonist L-748337 (50μg/kg, i.v.). The pressor response to adrenaline was enhanced by propranolol, but not by L-748337. The positive chronotropic action of adrenaline was markedly prevented by propranolol, whereas it was unaffected by L-748337. Noradrenaline (0.03-1.0μg/kg/min, i.v.) decreased the diameter of retinal arterioles but increased the mean blood pressure and heart rate. The effects of noradrenaline on retinal arteriolar diameter and blood pressure were unaffected by propranolol or L-748337. The positive chronotropic action of noradrenaline was almost completely abolished by propranolol. These results suggest that β(3)-adrenoceptors play crucial roles in vasodilator responses to adrenaline of retinal arterioles but have minor or no effect on noradrenaline-induced responses. The results also indicate that the functional role of β(3)-adrenoceptors may be more important than that in peripheral resistance vessels.

State of the Art in Stereoscopic and Autostereoscopic Displays

Underlying principles of stereoscopic direct-view displays, binocular head-mounted displays, and autostereoscopic direct-view displays are explained and some early work as well as the state of the art in those technologies are reviewed. Stereoscopic displays require eyewear and can be categorized based on the multiplexing scheme as: 1) color multiplexed (old technology but there are some recent developments; low-quality due to color reproduction and crosstalk issues; simple and does not require additional electronics hardware); 2) polarization multiplexed (requires polarized light output and polarization-based passive eyewear; high-resolution and high-quality displays available); and 3) time multiplexed (requires faster display hardware and active glasses synchronized with the display; high-resolution commercial products available). Binocular head-mounted displays can readily provide 3-D, virtual images, immersive experience, and more possibilities for interactive displays. However, the bulk of the optics, matching of the left and right ocular images and obtaining a large field of view make the designs quite challenging. Some of the recent developments using unconventional optical relays allow for thin form factors and open up new possibilities. Autostereoscopic displays are very attractive as they do not require any eyewear. There are many possibilities in this category including: two-view (the simplest implementations are with a parallax barrier or a lenticular screen), multiview, head tracked (requires active optics to redirect the rays to a moving viewer), and super multiview (potentially can solve the accommodation-convergence mismatch problem). Earlier 3-D booms did not last long mainly due to the unavailability of enabling technologies and the content. Current developments in the hardware technologies provide a renewed interest in 3-D displays both from the consumers and the display manufacturers, which is evidenced by the recent commercial products and new research results in this field.

7.1 T MRI to Assess the Anterior Segment of the Eye

Visualization of the anterior segment and biometric evaluation of the entire crystalline lens pose significant challenges for imaging techniques because of tissue-induced distortion artifacts. The present study was conducted to demonstrate the advantages of high-resolution magnetic resonance imaging (micro-MRI) for visualizing the anterior segment. High-resolution MR ocular images were acquired on an ultra-high-field MR unit using a two-channel coil with four coil elements and T(2)-weighted turbo spin echo sequences ex vivo in pig, rabbit, monkey, and human donor eyes and in vivo in rabbits. Tissue heating, reproducibility, and signal-to-noise ratio were investigated in vivo. Monkey eye lens thickness (LT) was also measured using A-scan ultrasonography (US). Anterior segment details of phakic eyes were obtained ex vivo (pig, rabbit, monkey, and human donor eyes) with pixel matrix size 512 × 512 (in-plane resolution 80 × 80 μm) and in vivo (rabbit eyes) with pixel matrix size 320 × 320 (in-plane resolution 125 × 125 μm). Complete quantification of lens dimensions as they correlate with the sulcus-sulcus and angle-angle plane can be performed. In LT determinations in monkey eyes, no significant difference was detected between micro-MRI and A-scan US (P > 0.05, Mann-Whitney U test). Biometric analysis of one pseudophakic monkey eye confirmed the absence of relevant distortion artifacts. Micro-MRI allows ex vivo and in vivo visualization and quantification of the spatial arrangement of the anterior eye segment. Imaging of the retroiridian region, including the entire crystalline lens, overcomes a number of major limitations in the quantitative evaluation of the anterior segment.

Studying hypertension in ocular fundus images using Hausdorff dispersion ordering

Retinal arterial and vein diameters are altered in individuals at risk of cardiovascular events mainly due to high blood pressure. The measurement of retinal vessel diameters has been proved to reflect individuals' vascular health. Dispersion of such measures which are obtained by means of ocular fundus images is a major factor not usually considered in clinical research. In this paper, a method to evaluate if different levels of clinically relevant covariables induce greater dispersion in retinal arterial and vein diameters is proposed. A multivariate dispersion ordering, the Hausdorff dispersion order, is used to compare the level of dispersion in such diameters for different groups of patients. Our statistical conclusions show that dispersion is higher in individuals with long-standing hypertension and in those who need two or more drugs to control hypertension. Hereby, dispersion is increased in the most severely ill persons. However, a greater level of smoking seems to be associated with a lesser dispersion. Dispersion of the vessel diameters must be taken into account in the image analysis of retinal vessel diameters because the comparison between homogeneous groups will produce highly accurate results in medical research.

Role of calcium-activated potassium channels in acetylcholine-induced vasodilation of rat retinal arterioles in vivo

The vascular endothelium plays an important role in regulating retinal blood flow via actions of several vasodilators, including nitric oxide (NO), prostaglandin I₂, and an endothelium-derived hyperpolarizing factor (EDHF). Our previous in vivo studies demonstrated that acetylcholine (ACh) dilates the rat retinal arteriole partly through NO- and prostaglandin-independent pathway, possibly the EDHF-mediated pathway, but the underlying mechanism(s) remains to be elucidated. It has been suggested that activation of Ca²+-activated K+ (K(Ca)) channels contributes to the EDHF-mediated responses; therefore, the roles of K(Ca) channels in ACh-induced vasodilation of retinal arterioles were examined in rats. The retinal vascular responses were assessed by determining changes in diameters of retinal arterioles in ocular fundus images that were captured with an original fundus camera system. Intravitreal injection of charybdotoxin, an inhibitor of intermediate- and large-conductance K(Ca) (I/BK(Ca)) channels, or iberiotoxin, an inhibitor of large-conductance K(Ca) (BK(Ca)) channels, significantly reduced the ACh-induced vasodilation of retinal arterioles, whereas neither apamin, an inhibitor of small-conductance K(Ca) (SK(Ca)) channels, nor TRAM-34, an inhibitor of intermediate-conductance K(Ca) (IK(Ca)) channels, altered the response. The vasodilator response to ACh observed under the combined blockade of NO synthase and cyclooxygenase with N(G)-nitro-L-arginine methyl ester plus indomethacin was also diminished by iberiotoxin. Iberiotoxin did not affect the NO donor NOR3-induced vasodilation of retinal arterioles, whereas it significantly reduced the BK(Ca) channel opener BMS-191011-induced responses. These results suggest that activation of BK(Ca) channels is involved in the EDHF-mediated component of the vasodilator response to ACh in the rat retinal arterioles in vivo.

Ultrasound Biomicroscopic Configurations of the Anterior Ocular Segment in a Population-Based Study: The Kumejima Study

To characterize quantitatively the configuration of the anterior ocular segment with ultrasound biomicroscopy (UBM) in a population-based setting. Cross-sectional study. Ten percent of 4632 residents aged > or =40 years of Kumejima, an island off southwest Japan, were randomly selected. We performed UBM under light and dark conditions in the 4 quadrants of the right eyes. The anatomic landmarks on the anterior ocular segment UBM images were identified by 1 examiner to quantify the peripheral anterior chamber depth (ACD), location of the ciliary body, and iris thickness. Angle-opening distance at 250 and 500 microm from the scleral spur (AOD250, AOD500), trabecular-iris angle (TIA), trabecular-ciliary process distance (TCPD), thickness of the iris (ID), trabecular-anterior iris surface angle (TAIA), trabecular-posterior iris surface angle (TPIA), trabecular-ciliary angle (TCA), and thickness of iris measured at 1000, 2000, and 3000 microm (IT1000, IT2000 and IT3000). The AOD500 averaged 0.267+/-0.138 (mean +/- standard deviation) and 0.202+/-0.116 mm under light and dark conditions, respectively; TIA 22.2+/-10.0 and 17.0+/-8.9 degrees; TCPD 0.755+/-0.165 and 0.748+/-0.152 mm; and ID 0.412+/-0.053 and 0.457+/-0.062 mm. The peripheral ACD was deepest temporally, then nasally, then inferiorly, and then superiorly (P<0.05, post hoc test). The position of the ciliary body was deepest nasally, then temporally, then inferiorly, and then superiorly (P<0.05). Iris thickness did not differ significantly among the quadrants. Older subjects had a shallower peripheral ACD, more anteriorly located ciliary body, and thinner iris (analysis of covariance, P<0.015). The peripheral ACD was deeper and the ciliary body was located more deeply in men than women (P<0.05), although no intergender differences in iris thickness were seen (P>0.1). Hyperopia, short axial length, and shallow central ACD were significantly correlated with shallower peripheral ACD, anteriorly located ciliary body, and thinner iris (P<0.05). Elevated intraocular pressure was associated with a shallow peripheral ACD (P< or =0.043). There are significant associations of the peripheral ACD, location of the ciliary body, and iris thickness with age, gender, refractive error, axial length, and intraocular pressure.

Automated study of ocular thermal images: Comprehensive analysis of corneal health with different age group subjects and validation

Thermography using infrared (IR) imaging is a non-invasive imaging technique widely used in medical and engineering arena nowadays. This technique is capable of detecting temperature changes in the vascular tissues, and plays an important role in the study of ocular surface temperature and ocular diseases. In this study the performance of an automated algorithm which acquires corneal surface temperature was studied for normal IR thermograms of different age groups. The automated algorithm consists of algorithms intelligently localizing cornea and removing eye lashes, reading in temperature values within the localized cornea without any human intervention for further analysis. Its performance was compared against the results of manual corneal delineation. Our studies showed that the automated algorithm performed as good as the tedious and laborious manual method with the calculated average corneal temperature of 34.01 ± 0.64 ° C (automated) and 33.99 ± 0.63 ° C for manual method.