1. Articles from Vikas Chopra

    1-24 of 24
    1. Reproducibility and agreement of four anterior segment-optical coherence tomography devices for anterior chamber angle measurements

      Reproducibility and agreement of four anterior segment-optical coherence tomography devices for anterior chamber angle measurements

      Purpose To compare the reproducibility and agreement of anterior chamber angle (ACA) parameters and metrics obtained by four different anterior segment-optical coherence tomography (AS-OCT) devices. Methods In this prospective study, 30 eyes from 15 normal subjects underwent anterior segment angle scanning using the Spectralis, Cirrus, and Optovue spectral domain optical coherence tomography (SD-OCT), as well as the Visante time-domain optical coherence tomography (TD-OCT). For each eye, the scan line was performed perpendicularly on the inferior (270°) angle, and the inferior ACA image was acquired 2 times. Inter-instrument and intra-instrument, as well as inter-observer and intra-observer reproducibility of anterior chamber angle ...

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    2. Identification and Characterization of Imaging Technique Errors and Artifacts using Anterior Segment Optical Coherence Tomography for Irido-Corneal Angle Evaluations in Glaucom

      Identification and Characterization of Imaging Technique Errors and Artifacts using Anterior Segment Optical Coherence Tomography for Irido-Corneal Angle Evaluations in Glaucom

      Purpose Anterior segment optical coherence tomography (ASOCT) platforms provide non-invasive and quantifiable evaluations of anterior chamber angle (ACA) anatomy. Even though these ACA measurements have been validated with high repeatability and reproducibility, we are the first study to describe in detail the technique errors and artifacts that may occur during imaging of the ACA. The purpose of this study was to define the different types and quantify the frequency of imaging technique errors and artifacts that are seen in ACA evaluation of a large cohort of patients with open-angle glaucoma. Design Retrospective cross-sectional design. Subjects Five thousand and eighty-two eyes ...

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    3. Applications of optical coherence tomography in cataract surgery

      Applications of optical coherence tomography in cataract surgery

      Purpose of review The rapid emergence and widespread adoption of optical coherence tomography (OCT) has spurred the development of many ophthalmic applications. Spectral domain OCT provides high-resolution in-vivo images of both anterior and posterior segments of the eye. Innovations in anterior segment OCT (AS-OCT) aim to improve refractive accuracy and reduce surgical risks. This review focuses on the utility of AS-OCT in cataract surgery for preoperative assessment, intraoperative assistance, and postoperative management to improve surgical outcomes. Recent findings Recent advances in AS-OCT for preoperative planning include characterization of dry eye and ocular surface conditions, calculation of intraocular lens (IOL) power ...

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      Mentions: Vikas Chopra
    4. Potential applications of optical coherence tomography angiography in glaucoma

      Potential applications of optical coherence tomography angiography in glaucoma

      Purpose of review Optical coherence tomography angiography (OCTA) is a novel, noninvasive imaging modality that allows assessment of the retinal and choroidal vasculature. The scope of this review is to summarize recent studies using OCTA in glaucoma and highlight potential applications of this new technology in the field of glaucoma . Recent findings OCTA studies have shown that retinal vascular changes may not develop solely as a result of advanced glaucoma damage. OCTA-derived measurements have provided evidence for lower retinal vascular densities at the optic nerve head, peripapillary and macula in preperimetric- glaucoma and early- glaucoma , as well as, in more ...

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      Mentions: UCLA Vikas Chopra
    5. Automated circumferential construction of first-order aqueous humor outflow pathways using spectral-domain optical coherence tomography

      Automated circumferential construction of first-order aqueous humor outflow pathways using spectral-domain optical coherence tomography

      The purpose was to create a three-dimensional (3-D) model of circumferential aqueous humor outflow (AHO) in a living human eye with an automated detection algorithm for Schlemm’s canal (SC) and first-order collector channels (CC) applied to spectral-domain optical coherence tomography (SD-OCT). Anterior segment SD-OCT scans from a subject were acquired circumferentially around the limbus. A Bayesian Ridge method was used to approximate the location of the SC on infrared confocal laser scanning ophthalmoscopic images with a cross multiplication tool developed to initiate SC/CC detection automated through a fuzzy hidden Markov Chain approach. Automatic segmentation of SC and initial ...

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    6. Effects of diurnal, lighting, and angle-of-incidence variation on anterior segment optical coherence tomography (AS-OCT) angle metrics

      Effects of diurnal, lighting, and angle-of-incidence variation on anterior segment optical coherence tomography (AS-OCT) angle metrics

      Background First reported study to assess the effect of diurnal variation on anterior chamber angle measurements, as well as, to re-test the effects of lighting and angle-of-incidence variation on anterior chamber angle (ACA) measurements acquired by time-domain anterior segment optical coherence tomography (AS-OCT). Methods A total of 30 eyes from 15 healthy, normal subjects underwent anterior chamber imaging using a Visante time-domain AS-OCT according to an IRB-approved protocol. For each eye, the inferior angle was imaged twice in the morning (8 am – 10 am) and then again in the afternoon (3 pm – 5 pm), under light meter-controlled conditions with ambient ...

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    7. Retinal vessel density from optical coherence tomography angiography to differentiate early glaucoma, pre-perimetric glaucoma and normal eyes

      Retinal vessel density from optical coherence tomography angiography to differentiate early glaucoma, pre-perimetric glaucoma and normal eyes

      Purpose To evaluate optic nerve vascular density using swept source optical coherence tomography angiography (OCTA) in patients with early primary open angle glaucoma (POAG), pre-perimetric glaucoma and normal eyes. Methods This is a prospective, observational study including 56 eyes in total and divided into 3 groups; 20 eyes with mild POAG, 20 pre-perimetric glaucoma eyes, and 16 age-matched normal eyes as controls. The optic disc region was imaged by a 1050-nm-wavelength swept-source OCT system (DRI OCT Triton, TOPCON). Vessel density was assessed as the ratio of the area occupied by the vessels in 3 distinct regions: 1) within the optic ...

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    8. Pilot Study of Lamina Cribrosa Intensity Measurements in Glaucoma Using Swept-Source Optical Coherence Tomography

      Pilot Study of Lamina Cribrosa Intensity Measurements in Glaucoma Using Swept-Source Optical Coherence Tomography

      Purpose: To compare the lamina cribrosa (LC) intensity in glaucoma-suspect eyes and eyes with mild to moderate glaucoma using swept-source optical coherence tomography. Methods: Optic disc volume scans were collected using swept-source optical coherence tomography in 19 clinically defined glaucoma-suspect eyes and 29 eyes with mild to moderate glaucoma. LC intensity was measured using Image J software, and the resultant values were normalized using the retinal pigment epithelium and vitreous signal. Results: Mean age was 53.7+/-18.5 years in the glaucoma-suspect eyes and 63.0+/-16.1 years in the eyes with mild to moderate glaucoma (P=0 ...

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    9. Assessment of Anterior Segment Measurements with Swept Source Optical Coherence Tomography before and after Ab Interno Trabeculotomy (Trabectome) Surgery

      Assessment of Anterior Segment Measurements with Swept Source Optical Coherence Tomography before and after Ab Interno Trabeculotomy (Trabectome) Surgery

      Purpose . To compare the changes of anterior segment parameters, assessed by swept source anterior segment optical coherence tomography (AS-OCT) after combined Trabectome-cataract surgery and Trabectome-only surgery in open angle glaucoma patients. Methods . Thirty-eight eyes of 24 patients with open angle glaucoma were scanned with swept source AS-OCT before and 4 weeks after combined Trabectome-cataract or Trabectome-only surgery. Intraocular pressure, number of medications, and AS-OCT parameters, such as angle opening distance at 500 and 750  μ m from the scleral spur (AOD500 and AOD750), trabecular-iris space area at 500 and 750 mm 2 (TISA500, TISA750), angle recess area at 500 and 750 ...

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      Mentions: Vikas Chopra
    10. Anterior Chamber Angle Morphometry Measurement Changes to Ambient Illumination Scaling in Visante Time Domain Optical Coherence Tomography

      Anterior Chamber Angle Morphometry Measurement Changes to Ambient Illumination Scaling in Visante Time Domain Optical Coherence Tomography

      Purpose : To test the effect of ambient illumination scaling on the reproducibility and reliability anterior chamber metrics using the Visante time domain optical coherence tomography (TD-OCT) instrument. Materials and methods : The inferior irido-corneal angles of 25 normal, healthy eyes were imaged twice with the Zeiss Visante TD-OCT under five strictly controlled ambient light conditions (foot candles (fc) measured with a light meter at camera/eye interface). Each eye was imaged 10 times totaling 250 assessments. Angle opening distance (AOD500/750), trabecular iris space area (TISA500/750), and scleral spur (SS) angle were graded twice by masked, trained graders at the ...

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    11. Utility of anterior segment swept-source optical coherence tomography for imaging eyes with antecedent ocular trauma

      Utility of anterior segment swept-source optical coherence tomography for imaging eyes with antecedent ocular trauma

      Purpose To evaluate the utility of swept source optical coherence tomography (SS-OCT) for the analysis of anterior segment structures in cases with previous traumatic eye injuries. Observations We report three eyes of three patients with anterior segment traumatic eye injury and highlight the role of SS-OCT in their evaluation and management. This technology enabled us to visualize the structural details of anterior segment of the eye and augment the clinical examination in our patients. Given that it is non-invasive and that there is no contact involved, it may be an ideal imaging modality for traumatic eye injuries for viewing the ...

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      Mentions: UCLA Vikas Chopra
    12. Identification of anterior chamber angle parameters with a portable SD-OCT device compared to a non-portable SD-OCT

      Identification of anterior chamber angle parameters with a portable SD-OCT device compared to a non-portable SD-OCT

      The aim of this study is to compare a portable spectral domain optical coherence tomography (SD-OCT) device with a non-portable SD-OCT for the identification of anterior chamber angle parameters based on location of Schwalbe’s line (SL) and to measure their reproducibility. 99 eyes from 46 normal, healthy participants underwent imaging of the inferior iridocorneal angle with the iVue and Cirrus SD-OCT under well-controlled low-light conditions. SL-angle opening distance (SL-AOD) and SL-trabecular iris space area (SL-TISA) were measured by masked, certified graders at the Doheny Image Reading Center using customized Image J grading software. Inter- and intrainstrument, as well as ...

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    13. Regression Analysis of Optical Coherence Tomography Disc Variables for Glaucoma Diagnosis

      Regression Analysis of Optical Coherence Tomography Disc Variables for Glaucoma Diagnosis

      Purpose: To report diagnostic accuracy of optical coherence tomography (OCT) disc variables using both time-domain (TD) and Fourier-domain (FD) OCT, and to improve the use of OCT disc variable measurements for glaucoma diagnosis through regression analyses that adjust for optic disc size and axial length-based magnification error. Design: Observational, cross-sectional. Participants: In total, 180 normal eyes of 112 participants and 180 eyes of 138 participants with perimetric glaucoma from the Advanced Imaging for Glaucoma Study. Methods: Diagnostic variables evaluated from TD-OCT and FD-OCT were: disc area, rim area, rim volume, optic nerve head volume, vertical cup-to-disc ratio (CDR), and horizontal ...

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    14. Effects of Light Variation on Schwalbe's Line-based Anterior Chamber Angle Metrics Measured with Cirrus Spectral Domain Optical Coherence Tomography

      Effects of Light Variation on Schwalbe's Line-based Anterior Chamber Angle Metrics Measured with Cirrus Spectral Domain Optical Coherence Tomography

      Background Evaluate the impact of variations in ambient lighting conditions on the reproducibility/reliability of Schwalbe's Line (SL)-based anterior chamber angle (ACA) metrics using spectral domain optical coherence tomography (SD-OCT). Design Images were taken at Doheny Eye Centers-UCLA clinic, which were randomized, masked, and graded twice by dual reading center graders. Participants 25 normal/healthy participants with open-angles Methods Inferior angles were imaged using Cirrus SD-OCT under five light levels (foot-candles(fc) measured at camera-eye interface with Sper light-meter) with the instrument's Corneal Illumination function set to default level of 50(CIdef) and low 5(CIlow). Each ...

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    15. Predicting Development of Glaucomatous Visual Field Conversion Using Baseline Fourier-Domain Optical Coherence Tomography

      Predicting Development of Glaucomatous Visual Field Conversion Using Baseline Fourier-Domain Optical Coherence Tomography

      Purpose To predict the development of glaucomatous visual field (VF) defects using Fourier-domain optical coherence tomography (FD-OCT) measurements at baseline visit. Design Multi-center longitudinal observational study. Glaucoma suspects and pre-perimetric glaucoma participants in the Advanced Imaging for Glaucoma Study. Methods The optic disc, the peripapillary retinal nerve fiber layer (NFL), and macular ganglion cell complex (GCC) were imaged with FD-OCT VF was assessed every 6 months. Conversion to perimetric glaucoma was defined by VF pattern standard deviation (PSD) or glaucoma hemifield test (GHT) outside normal limits on 3 consecutive tests. Hazard ratios were calculated with the Cox proportional hazard model ...

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    16. Agreement in Quantitative Anterior Chamber Angle Metrics between RTVue and Cirrus Spectral Domain Optical Coherence Tomography

      Agreement in Quantitative Anterior Chamber Angle Metrics between RTVue and Cirrus Spectral Domain Optical Coherence Tomography

      Purpose: To investigate the agreement between two spectral domain optical coherence tomography (SD-OCT) instruments in Schwalbe’s line (SL) based anterior chamber angle parameters and to evaluate their repeatability and reproducibility. Methods: The inferior irido-corneal angle of 114 eyes from 59 participants (29 glaucoma and 30 normal) were scanned twice with the Optovue SD-OCT and Cirrus SD-OCT under controlled low luminance conditions. SL angle opening distance (SL-AOD) and SL trabecular-iris-space area (SL-TISA) were graded by masked certified graders at the Doheny Image Reading Center. Results: The mean SL-AOD/SL-TISA was 623±271µm/ 0.221 ± 0.106 mm2 for the ...

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    17. Reproducibility and Agreement Between 2 Spectral Domain Optical Coherence Tomography Devices for Anterior Chamber Angle Measurements

      Reproducibility and Agreement Between 2 Spectral Domain Optical Coherence Tomography Devices for Anterior Chamber Angle Measurements

      Purpose: To compare anterior chamber angle parameters based on the location of Schwalbe line (SL) from 2 spectral domain optical coherence tomography (SD-OCT) instruments and to measure their reproducibility. Methods: Forty-two eyes from 21 normal, healthy participants underwent imaging of the inferior irido-corneal angle with the Spectralis and Cirrus SD-OCT under tightly controlled low-light conditions. SL-angle opening distance (SL-AOD) and SL-trabecular iris space area (SL-TISA) were measured by masked, certified graders at the Doheny Imaging Reading Center using customized grading software. Interinstrument and intrainstrument, as well as interobserver and intraobserver reproducibility of SL-AOD and SL-TISA measurements were evaluated by intraclass ...

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    18. Comparison of Physiologic versus Pharmacologic Mydriasis on Anterior Chamber Angle Measurements Using Spectral Domain Optical Coherence Tomography

      Comparison of Physiologic versus Pharmacologic Mydriasis on Anterior Chamber Angle Measurements Using Spectral Domain Optical Coherence Tomography

      Purpose. To compare the effects of physiologic versus pharmacologic pupil dilation on anterior chamber angle (ACA) measurements obtained with spectral domain optical coherence tomography (SD-OCT). Methods. Forty eyes from 20 healthy, phakic individuals with open angles underwent anterior segment OCT imaging under 3 pupillary states: (1) pupil constricted under standard room lighting, (2) physiologic mydriasis in a darkened room, and (3) postpharmacologic mydriasis. Inferior angle Schwalbe’s line-angle opening distance (SL-AOD) and SL-trabecular-iris-space area (SL-TISA) were computed for each eye and pupillary condition by masked, certified Reading Center graders using customized grading software. Results. SL-AOD and SL-TISA under pupillary constriction ...

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    19. Effect of Angle of Incidence on Anterior Chamber Angle Metrics From Optical Coherence Tomography

      Effect of Angle of Incidence on Anterior Chamber Angle Metrics From Optical Coherence Tomography

      Purpose: To evaluate the local variability of anterior chamber angle (ACA) metrics obtained by time domain (TD) and spectral domain (SD) optical coherence tomography (OCT). Materials and Methods: Anterior-segment OCT imaging was performed on 30 normal eyes using Visante TD-OCT and 40 normal eyes using Cirrus SD-OCT. For Visante OCT, a single 16-mm line scan of the inferior angle with 3 slightly different rotations of 265, 270, and 275 degrees was performed. For Cirrus OCT, a 5-line raster of the inferior angle was performed, centering the third scan line at the 6 o'clock position, with 0.25 mm between ...

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    20. Reproducibility of Anterior Segment Angle Metrics Measurements Derived From Cirrus Spectral Domain Optical Coherence Tomography

      Reproducibility of Anterior Segment Angle Metrics Measurements Derived From Cirrus Spectral Domain Optical Coherence Tomography

      Purpose: To investigate the reproducibility of anterior segment angle (ACA) metrics measurements in normal subjects on Cirrus spectral domain optical coherence tomography (SD-OCT). Methods: 40 eyes from 20 healthy, normal subjects underwent anterior segment imaging using a Cirrus SD-OCT. For each eye, 2 acquisitions of 5-line raster scans were performed perpendicularly on the inferior (270 degrees) angle. The Schwalbe's line-angle opening distance (SL-AOD) and Schwalbe's line-trabecular-iris space area (SL-TISA) measurements were performed by masked certified reading center graders using customized grading software. Intra-acquisition, intergrader, and intragrader reproducibility of SL-AOD and SL-TISA measurements were evaluated by intraclass correlation coefficients ...

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    21. Reproducibility of Angle Metrics Using the Time-Domain Anterior Segment Optical Coherence Tomography: Intra-Observer and Inter-Observer Variability

      Reproducibility of Angle Metrics Using the Time-Domain Anterior Segment Optical Coherence Tomography: Intra-Observer and Inter-Observer Variability

      Purpose : To evaluate the reproducibility of anterior chamber angle measurements obtained by the Zeiss Visante anterior segment optical coherence tomography (AS-OCT). Methods : Twenty eyes from 20 normal subjects with open anterior chamber angles were studied. The anterior chamber angle was imaged using the Visante AS-OCT. The angle-opening distance (AOD 500, AOD 750), trabercular iris space area (TISA 500, TISA 750) and scleral spur angle (SS angle) at the inferior angle location were measured. All the subjects underwent imaging in a darkened room (1 foot candles measured at the eye). Images were graded in a masked fashion by certified Doheny Image ...

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    22. Applications of optical coherence tomography in cataract surgery

      Applications of optical coherence tomography in cataract surgery

      Purpose of review: The rapid emergence and widespread adoption of optical coherence tomography (OCT) has spurred the development of many ophthalmic applications. Spectral domain OCT provides high-resolution in-vivo images of both anterior and posterior segments of the eye. Innovations in anterior segment OCT (AS-OCT) aim to improve refractive accuracy and reduce surgical risks. This review focuses on the utility of AS-OCT in cataract surgery for preoperative assessment, intraoperative assistance, and postoperative management to improve surgical outcomes. Recent findings: Recent advances in AS-OCT for preoperative planning include characterization of dry eye and ocular surface conditions, calculation of intraocular lens (IOL) power ...

      Read Full Article
    23. Does optic nerve head size variation affect circumpapillary retinal nerve fiber layer thickness measurement by optical coherence tomography?

      Does optic nerve head size variation affect circumpapillary retinal nerve fiber layer thickness measurement by optical coherence tomography?

      Purpose: To determine the relationship between retinal nerve fiber layer (RNFL) thickness, optic disc size and image magnification. Methods: The cohort consisted of 196 normal eyes of 101 participants in the Advanced Imaging for Glaucoma Study (AIGS), a multi-center, prospective, longitudinal study to develop advanced imaging technologies for glaucoma diagnosis. Scanning laser tomography (HRT II) was used to measure disc size. Optical coherence tomography (Stratus) was used to perform circumpapillary RNFL thickness measurements using the standard fixed 3.46 mm nominal scan diameter. A theoretical model of magnification effects was developed to relate RNFL thickness (overall average) with axial length ...

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    24. Detection of Macular Ganglion Cell Loss in Glaucoma by Fourier-Domain Optical Coherence Tomography

      Detection of Macular Ganglion Cell Loss in Glaucoma by Fourier-Domain Optical Coherence Tomography
      Purpose: To map ganglion cell complex (GCC) thickness with high-speed Fourier-domain optical coherence tomography (FD-OCT) and compute novel macular parameters for glaucoma diagnosis.Design: Observational, cross-sectional study.Participants: One hundred seventy-eight participants in the Advanced Imaging for Glaucoma Study, divided into 3 groups: 65 persons in the normal group, 78 in the perimetric glaucoma group (PG), and 52 in the preperimetric glaucoma group (PPG).Methods: The RTVue FD-OCT system was used to map the macula over a 7×6 mm region. The macular OCT images were exported for automatic segmentation using software we developed. The program measured macular retinal (MR ...
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    1-24 of 24
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    1. (24 articles) Vikas Chopra
    2. (14 articles) UCLA
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    Detection of Macular Ganglion Cell Loss in Glaucoma by Fourier-Domain Optical Coherence Tomography Does optic nerve head size variation affect circumpapillary retinal nerve fiber layer thickness measurement by optical coherence tomography? Applications of optical coherence tomography in cataract surgery Reproducibility of Angle Metrics Using the Time-Domain Anterior Segment Optical Coherence Tomography: Intra-Observer and Inter-Observer Variability Reproducibility of Anterior Segment Angle Metrics Measurements Derived From Cirrus Spectral Domain Optical Coherence Tomography Effect of Angle of Incidence on Anterior Chamber Angle Metrics From Optical Coherence Tomography Reproducibility and Agreement Between 2 Spectral Domain Optical Coherence Tomography Devices for Anterior Chamber Angle Measurements Agreement in Quantitative Anterior Chamber Angle Metrics between RTVue and Cirrus Spectral Domain Optical Coherence Tomography Predicting Development of Glaucomatous Visual Field Conversion Using Baseline Fourier-Domain Optical Coherence Tomography Pilot Study of Lamina Cribrosa Intensity Measurements in Glaucoma Using Swept-Source Optical Coherence Tomography Carotid Disease and Retinal Optical Coherence Tomography Angiography Parameters in Type 2 Diabetes: The Fremantle Diabetes Study Phase II Retinal Vascular Density on Optical Coherence Tomography Angiography and Age-related Central and Peripheral Hearing Loss in a Southern Italian Older Population