Evaluation of aqueous-deficient and evaporative dry eye cases with confocal microscopy.

INTRODUCTION: Dry eye disease (DED) is an important health problem affecting hundreds of millions of people worldwide. In vivo confocal microscopy (IVCM) is a non-invasive imaging tool that can visualize ocular surface diseases. In this study, we aimed to evaluate corneal structures and inflammatory cells with IVCM in DED patients. MATERIAL AND METHODS: The patients were divided into three subgroups: group 1, consisting of 22 patients with aqueous tear insufficiency; group 2, consisting of 21 patients with evaporative type DED; and group 3, consisting of 20 healthy patients. Imaging was performed with IVCM. The corneal epithelium, nerves, stroma, endothelial and inflammatory cells were compared between groups. RESULTS: There was a significant decrease in corneal epithelial cell density in cases with DED, and there was a significant increase in corneal basal epithelial cell density in the aqueous-deficient type. Keratocyte density was significantly increased in the aqueous-deficient type. A significant decrease in the number and density of sub-basal nerves was found in aqueous-deficient cases, and an increase was found in neural pilling and folding. Dendritic cell density, size, number and area were significantly increased in the aqueous-deficient type. There was also decreased corneal endothelial cell density in DED. CONCLUSION: We evaluated pathological changes in DED on the corneal surface by IVCM. This methodology is valuable in terms of objectively evaluating how the corneal surface is affected in accordance with disease severity and in predicting poor response to treatment.

Quantitative OCT angiography of the retina and choroid in non-ocular sarcoidosis.

OBJECTIVE: The aim of the study was to evaluate retinal and choroidal microvascular morphological changes in non-ocular sarcoidosis (NOS) patients using optical coherence tomography angiography (OCTA) and compare the results to age- and gender-matched healthy individuals. PATIENTS AND METHODS: This study included 37 NOS patients (group 1, 37 right eyes) referred to the Ophthalmology Department between 2019 and 2021, as well as 31 healthy individuals (group 2, 31 right eyes). Non-ocular sarcoidosis was defined as sarcoidosis confirmed by a positive lung X-ray and biopsy without ocular manifestation. All participants underwent a comprehensive ophthalmic examination. The SPECTRALIS® OCT was used for both fundus photography and macular analysis. All OCTA procedures were performed in the Angio Retina mode (6.0x6.0 mm) to assess retinal and choroidal microvascular morphology. RESULTS: Groups 1 and 2 had mean ages of 46.41±12.52 and 47.55±13.81 years, respectively (p=0.482). Group 1 had significantly increased superficial capillary plexus (SCP) and deep capillary plexus (DCP) vessel densities (VDs) in whole (p=0.059, 0.016), parafoveal (p=0.051, 0.015), and perifoveal (p=0.060, 0.010) regions relative to group 2. Group 1 was also associated with increased foveal avascular zone (FAZ) area (p=0.196), FAZ circumference (p=0.262), and foveal VD in 300 µm wide regions surrounding FAZ (p=0.003) relative to group 2. The outer retinal (p=0.712) and choriocapillaris (p=0.684) flows did not differ significantly between the two groups. CONCLUSIONS: Quantitative OCTA analysis revealed a higher tendency for retinal and choroidal microvascular morphological changes in NOS patients, demonstrating the potential of this novel, non-invasive imaging technology, which may provide sensitive and reliable results without using contrast materials.

Consequences of seasonal allergic conjunctivitis on ocular parameters of anterior and posterior segments: An up-to-date imaging approach.

AIMS: To investigate consequences of seasonal allergic conjunctivitis (SAC) on the ocular anterior and posterior segment parameters. MATERIALS AND METHODS: Forty healthy participants (mean age: 25.90 ± 5.7 years, 20 females, 20 males) and 40 patients with SAC (mean age: 26.20 ± 5.7 years, 20 females, 20 males) were included in this prospective study. The anterior segment parameters including central corneal thickness (CCT) and anterior chamber depth (ACD) were measured by Scheimpflug imaging system. Axial length (AL) was measured by optical biometry. The posterior segment parameters, including retinal nerve fiber layer (RNFL), subfoveal choroidal thickness, and central macular thickness were measured by optical coherence tomography. RESULTS: Similar values of the ACD, AL, RNFL as well as central macular thickness between healthy participants and patients with SAC were revealed. Despite the CCT being thinner in SAC, there was no statistically significant difference between the two groups. On the other hand, SAC was found to be associated with an increase in subfoveal choroidal thickness, the condition of which may be attributed to the inflammatory nature of the disease. CONCLUSION: The present study has managed to demonstrate non-significant alterations in the ocular anterior and posterior segment parameters of patients with SAC. Yet, the increase in subfoveal choroidal thickness may be linked to the accompanying inflammation of both the conjunctiva and other ocular tissues, particularly the choroidal layer.

The effect of intravitreal dexamethasone implant on central foveal thickness and choroidal thickness in retinal vein occlusion.

AIM: To investigate the effect of intravitreal dexamethasone implant on central foveal thickness and choroidal thickness in retinal vein occlusion. MATERIALS AND METHODS: Clinical records and optical coherence tomography (OCT) scans of 41 naïve patients with retinal vein occlusion (RVO), who were initially treated with intravitreal dexamethasone (DEX) implant between 2016 and 2017 at Kocatepe University Faculty of Medicine, Department of Ophthalmology were investigated. Collected data included age and sex of the patients, crystalline lens status, baseline and final intraocular pressure, and OCT parameters including central foveal thickness and choroidal thickness. RESULTS: Twenty-two (53.7%) female and 19 (46.3%) male patients were enrolled in the study. There were 30 phakic and 11 pseudophakic patients. The intraocular pressure increased significantly from 15.19 mmHg to 17.8 mmHg (P = 0.005), and cataract extraction was performed in two patients who developed cataract after the treatment. There was a significant decrease in the central foveal thickness from 556 µm to 288 µm (P < 0.001). In addition, although there was no statistically significant change in choroidal thickness in the patients with branched retinal vein occlusion (P = 0.423), the patients with central retinal vein occlusion had statistically significant decrease in choroidal thickness measurements (P = 0.049). CONCLUSION: Therapeutic effect of the DEX implant not only influences retinal layer. Its influence may also extend further to the choroid layer, thereby leading to decrease in the choroidal thickness. Our results were mostly similar to the results of studies in literature which investigated the effects of the DEX implant therapy on the choroidal thickness of the patients with RVO.

Investigation of sequential properties of snoring episodes for obstructive sleep apnoea identification.

In this paper, 'snore regularity' is studied in terms of the variations of snoring sound episode durations, separations and average powers in simple snorers and in obstructive sleep apnoea (OSA) patients. The goal was to explore the possibility of distinguishing among simple snorers and OSA patients using only sleep sound recordings of individuals and to ultimately eliminate the need for spending a whole night in the clinic for polysomnographic recording. Sequences that contain snoring episode durations (SED), snoring episode separations (SES) and average snoring episode powers (SEP) were constructed from snoring sound recordings of 30 individuals (18 simple snorers and 12 OSA patients) who were also under polysomnographic recording in Gülhane Military Medical Academy Sleep Studies Laboratory (GMMA-SSL), Ankara, Turkey. Snore regularity is quantified in terms of mean, standard deviation and coefficient of variation values for the SED, SES and SEP sequences. In all three of these sequences, OSA patients' data displayed a higher variation than those of simple snorers. To exclude the effects of slow variations in the base-line of these sequences, new sequences that contain the coefficient of variation of the sample values in a 'short' signal frame, i.e., short time coefficient of variation (STCV) sequences, were defined. The mean, the standard deviation and the coefficient of variation values calculated from the STCV sequences displayed a stronger potential to distinguish among simple snorers and OSA patients than those obtained from the SED, SES and SEP sequences themselves. Spider charts were used to jointly visualize the three parameters, i.e., the mean, the standard deviation and the coefficient of variation values of the SED, SES and SEP sequences, and the corresponding STCV sequences as two-dimensional plots. Our observations showed that the statistical parameters obtained from the SED and SES sequences, and the corresponding STCV sequences, possessed a strong potential to distinguish among simple snorers and OSA patients, both marginally, i.e., when the parameters are examined individually, and jointly. The parameters obtained from the SEP sequences and the corresponding STCV sequences, on the other hand, did not have a strong discrimination capability. However, the joint behaviour of these parameters showed some potential to distinguish among simple snorers and OSA patients.

An efficient method for snore/nonsnore classification of sleep sounds.

A new method to detect snoring episodes in sleep sound recordings is proposed. Sleep sound segments (i.e., 'sound episodes' or simply 'episodes') are classified as snores and nonsnores according to their subband energy distributions. The similarity of inter- and intra-individual spectral energy distributions motivated the representation of the feature vectors in a lower dimensional space. Episodes have been efficiently represented in two dimensions using principal component analysis, and classified as snores or nonsnores. The sound recordings were obtained from individuals who are suspected of OSAS pathology while they were connected to the polysomnography in Gülhane Military Medical Academy Sleep Studies Laboratory (GMMA-SSL), Ankara, Turkey. The data from 30 subjects (18 simple snorers and 12 OSA patients) with different apnoea/hypopnea indices were classified using the proposed algorithm. The system was tested by using the manual annotations of an ENT specialist as a reference. The accuracy for simple snorers was found to be 97.3% when the system was trained using only simple snorers' data. It drops to 90.2% when the training data contain both simple snorers' and OSA patients' data. (Both of these results were obtained by using training and testing sets of different individuals.) In the case of snore episode detection with OSA patients the accuracy is 86.8%. All these results can be considered as acceptable values to use the system for clinical purposes including the diagnosis and treatment of OSAS. The method proposed here has been used to develop a tool for the ENT clinic of GMMA-SSL that provides information for objective evaluation of sleep sounds.

Selective brain cooling seems to be a mechanism leading to human craniofacial diversity observed in different geographical regions.

Selective brain cooling (SBC) can occur in hyperthermic humans despite the fact that humans have no carotid rete, a vascular structure that facilitates countercurrent heat exchange located at the base of the skull in some mammals. Emissary and angular veins, upper respiratory tract, tympanic cavity and cerebrospinal fluid are major components of SBC system in humans. The efficiency of SBC is increased by evaporation of sweat on the head and by ventilation through the nose, but it is surprising to find out that mammals do not display SBC during exercise hyperthermia. What is the explanation then for the SBC at high body temperatures? Our hypothesis is that selective brain cooling protects the brain from thermal damage in a long-standing manner by allowing adaptive mechanisms to change the craniofacial morphology appropriate for different environmental conditions. Since the brain can only be as big that can cool, it is not surprising to find a lower (below 1300 cm(3)) cranial volume in Australian Aborigines with respect to the one (over 1450 cm(3)) in Eskimos. In addition to lower brain volume, other craniofacial features such as thick everted lips, broader nasal cavity and bigger paranasal sinuses that provide more evaporating surfaces seem to be anatomical variations developed in time for an effective SBC in hot climates. It was reported previously that these biological adaptations result from the tissues of neural crest origin. Among the crest derivatives, leptomeninges (pia and arachnoid mater), skeletal and connective tissues of the face and much of the skull seem to be structures upon which environment operates to produce more convenient craniofacial morphology for an effective SBC. In conclusion, selective brain cooling seems to be a mechanism leading to adaptive craniofacial diversity observed in different geographical regions. Thus, SBC is necessary for long-term biological adaptation, not for protecting the brain from acute thermal damage.

Multiresolutional modification of speech signals for listeners with hearing impairment.

A new method, the multiresolutional modification algorithm (MMA), which modifies speech signals in frequency and time domains, is proposed for listeners with hearing impairment and early clinical results are reported. Unlike other methods, this algorithm modifies the wavelet coefficients of the speech signal in order to obtain a modified version of the original signal instead of modifying the speech waveform itself. The speech signal is first divided into subbands using an 11-level quadrature mirror filter (QMF) bank. These subbands are then modified using the modification algorithm. Finally, the inverse Wavelet transform is applied to these modified subband coefficients in order to reconstruct a modified version of the input signal. The efficacy of the MMA was evaluated using subjects with hearing impairment and subjects with no such impairment. Listening tests showed that the proposed algorithm increases the quality and intelligibility of the modified speech over the well-known modification algorithms.

A new dynamic renal phantom and its application to scintigraphic studies for pixel basis functional radionuclide imaging.

Various phantoms have been proposed in order to simulate the physical structures of human organs, such as those used in computerized brain tomography. Studying the functional behaviour of kidney by means of functional imaging techniques suffers from a lack of dynamic renal phantom for simulation. In this study a new dynamic renal phantom (DRP) is proposed and the first test results are reported which demonstrate the significance of deconvolution analysis in scintigraphy. The main idea in the construction of our DRP involves the filtration of chemical substances from the blood by flowing it through coiled tubes surrounded by semipermeable membranes. The DRP tests are performed with Technetium-99m (Tc-99m). The semipermeable membrane in the DRP passes Tc-99m, salts and small molecules but not blood cells and large protein molecules. The proposed DRP is tested using pixel basis renal functional radionuclide imaging techniques and promising results are obtained.