Robert Kromer

Evaluation of Retinal Vessel Morphology in Patients with Parkinson's Disease Using Optical Coherence Tomography.

Purpose The retina has been found affected in Parkinson’s disease (PD). It is unclear if this is due to neurodegeneration of local dopamine-dependent retinal cells, a result of central nervous degeneration including the optic nerve or retinal small vessel disease. This study aimed to detect changes of the retinal vasculature in PD patients compared to controls. Methods We examined 49 PD patients and 49 age- and sex-matched healthy controls by spectral domain optical coherence tomography (SD-OCT) with a circular scan centred at the optic disc. Vessels within the retinal nerve fibre layer were identified by an automated algorithm and thereafter manually labelled as artery or vein. Layer segmentation, vessel lumen and direct surrounding tissue were marked automatically with a grey value and the contrast between both values in relation to the surrounding tissue was calculated. The differences in these grey value ratios among subjects were determined and used as an indicator for differences in vessel morphology. Furthermore, the diameters of the veins and arteries were measured and then compared between the groups. Results The contrast of retinal veins was significantly lower in PD patients compared to controls, which indicates changes in vessel morphology in PD. The contrast of arteries was not significantly different. Disease duration, disease stage according to Hoehn and Yahr or age did not influence the grey value ratios in PD patients. Vessel diameter in either veins or arteries did not differ between subject groups. The contrast of retinal veins contralateral to the clinically predominant and first affected side was significantly lower compared to the ipsilateral side. Conclusion Our data show a potential difference of the retinal vasculature in PD patients compared to controls. Vascular changes in the retina of PD patients might contribute to vision-related complaints in PD.

Optical Coherence Tomography-Based Scattering Properties of Retinal Vessels in Glaucoma Patients

ABSTRACT Purpose: Clinical trials have demonstrated that retinal blood flow deficiencies are present in patients with open-angle glaucoma (OAG). We introduce a method for facilitating retinal vessel analysis: The intensity of the distal shadow of vessels in optical coherence tomography (OCT) caused by the scattered signal is analyzed, compared between healthy subjects and OAG patients and correlated with OCT angiography (OCT-A) flow density. Patients and Methods: We recruited 80 patients with diagnosed OAG (mean age 63.4 ± 13.2 years) and 80 healthy age-matched control subjects for comparison, and 20 patients for the correlation with OCT-A flow density. Patients received perimetry, peripapillary OCT measurements, and selected patients OCT-A of the papillary area. The vessel shadow intensity (VSI) is based on peripapillary OCT scans: the intensity of the distal vessel shadow was automatically compared to its surroundings, separated by arteries and veins. Flow density of the OCT-A scan was calculated by binarization and quantification of the pixel density. Results: The VSI for arteries was in OAG patients with 7.52 ± 2.62 [%] significantly lower compared to healthy subjects (9.03 ± 3.38 [%], p = 0.0029). In veins, the VSI was as well significantly lower for OAG patients (14.9 ± 3.59 [%]) compared to healthy subjects (17.46 ± 4.45 [%], p < 0.0001). Furthermore, in OAG patients there was a significant correlation of mean deviation of the visual field results with the veins’ VSI (p = 0.0006; r = −0,454). There was no significant correlation of scattering properties with OCT-A flow density (p > 0.05). Conclusions: We conclude that the OCT-based analysis of the scattering properties of retinal vessels differs significantly between patients with OAG and healthy subjects. Furthermore, changes in the scattering properties of veins correlated with the stage of the disease in terms of visual field deficits. These properties might complement existing measurements of ocular blood flow including OCT-A flow density.

Predicting Surgical Success in Patients with Idiopathic Epiretinal Membrane Using the Spectral-Domain Optical Coherence Tomography Segmentation Module for Single Retinal Layer Analysis

ABSTRACT Introduction: Idiopathic epiretinal membrane (ERM) is a proliferation of cells formed on the internal surface of the retina and may cause a slow decrease in visual acuity (VA). The aim of this study was to evaluate the individual layers of the retina by optical coherence tomography (OCT) before and after vitrectomy with ERM peeling in order to refine surgical decision-making. Methods: Forty-seven eyes of 45 patients (aged 55–87 years) with ERM were enrolled retrospectively from a tertiary referral center. OCT examination was performed preoperatively and at a mean of 3.2 months postoperatively in all cases. Nine retinal surfaces were subjected to automated all-layer segmentation using the manufacturer’s software and assessed for their correlation with VA. Results: There was a significant correlation between the initial retinal morphology and change in VA postoperatively. Patients who gained at least two lines of VA had a significantly higher total retinal perimacular volume and retinal nerve fiber layer (each p < 0.0001) preoperatively. Conclusion: Patients with high preoperative retinal volumes and therefore increased tractive components seemed to benefit more from surgery than those with low tractive components.

Retinal degeneration in progressive supranuclear palsy measured by optical coherence tomography and scanning laser polarimetry

This cross-sectional study compared the retinal morphology between patients with progressive supranuclear palsy (PSP) and healthy controls. (The retinal nerve fiber layer (RNFL) around the optic disc and the retina in the macular area of 22 PSP patients and 151 controls were investigated by spectral domain optical coherence tomography (SD-OCT). Additionally, the RNFL and the nerve fiber index (NFI) were measured by scanning laser polarimetry (SLP). Results of RNFL measurements with SD-OCT and SLP were compared to assess diagnostic discriminatory power. Applying OCT, PSP patients showed a smaller RNFL thickness in the inferior nasal and inferior temporal areas. The macular volume and the thickness of the majority of macular sectors were reduced compared to controls. SLP data showed a thinner RNFL thickness and an increase in the NFI in PSP patients. Sensitivity and specificity to discriminate PSP patients from controls were higher applying SLP than SD-OCT. Retinal changes did not correlate with disease duration or severity in any OCT or SLP measurement. PSP seems to be associated with reduced thickness and volume of the macula and reduction of the RNFL, independent of disease duration or severity. Retinal imaging with SD-OCT and SLP might become an additional tool in PSP diagnosis.

An Automated Approach for Localizing Retinal Blood Vessels in Confocal Scanning Laser Ophthalmoscopy Fundus Images

In this work, we present a rules-based method for localizing retinal blood vessels in confocal scanning laser ophthalmoscopy (cSLO) images and evaluate its feasibility. A total of 31 healthy participants (17 female; mean age: 64.0xa0±xa08.2xa0years) were studied using manual and automatic segmentation. High-resolution peripapillary scan acquisition cSLO images were acquired. The automated segmentation method consisted of image pre-processing for gray-level homogenization and blood vessel enhancement (morphological opening operation, Gaussian filter, morphological Top-Hat transformation), binary thresholding (entropy-based thresholding operation), and removal of falsely detected isolated vessel pixels. The proposed algorithm was first tested on the publically available dataset DRIVE, which contains color fundus photographs, and compared to performance results from the literature. Good results were obtained. Monochromatic cSLO images segmented using the proposed method were compared to those manually segmented by two independent observers. For the algorithm, a sensitivity of 0.7542, specificity of 0.8607, and accuracy of 0.8508 were obtained. For the two independent observers, a sensitivity of 0.6579, specificity of 0.9699, and accuracy of 0.9401 were obtained. The results demonstrate that it is possible to localize vessels in monochromatic cSLO images of the retina using a rules-based approach. The performance results are inferior to those obtained using fundus photography, which could be due to the nature of the technology.

The Top 100 Papers of 25 Years of Macular Imaging Using Optical Coherence Tomography

ABSTRACT We analyzed and quantified the 100 most frequently cited papers in macular imaging using optical coherence tomography (OCT). The databases of the Institute for Scientific Information databases utilized for identification of articles in macular imaging using OCT over the last 25 years since the introduction of OCT in ophthalmology. All articles containing “optical coherence tomography” and “retina” without “glaucoma”. The publication dates of the 100 most-cited articles ranged from 1991 to 2015, with the greatest number of articles published in the 2000s, while the total number of citations per article was greatest for articles published in the 1990s. Most studies were conducted in the U.S. and represented Level-IV clinical outcome studies indicating that also small case series or cohort studies could gain attention. The top 5 senior authors contributed to 39 of the 100 selected publications and accrued a total of 66.0% of all citations of those articles.

Association between optical coherence tomography based retinal microvasculature characteristics and myocardial infarction in young men

Incident myocardial infarction (MI) is a leading cause of adult mortality in the United States. However, because MI has a relatively low incidence in the young population, little information exists on the disease in younger adults. Because the retina has the unique quality that its vasculature is readily and noninvasively visible, the retina is frequently studied to evaluate correlations between vessels and cardiovascular diseases. In the current study, we evaluated the retinal microvasculature of patients who had experienced an MI before 50 years of age (nu2009=u200953 subjects) and age- and sex-matched patients who had not experienced an MI (nu2009=u200953 patients). We used circular optical coherence tomography (OCT) scans to image peripapillary venules and arterioles. The diameter of each vessel was measured and the respective arterial-venous ratio (AVR) was calculated. We did not detect any significant differences between MI and control subjects in retinal vessel calibre or AVR.

Bruch’s Membrane Opening Minimum Rim Width Measurement with SD-OCT: A Method to Correct for the Opening Size of Bruch’s Membrane

A precise evaluation of the retinal nerve fiber layer thickness (RNFLT) is key for diagnosing and monitoring glaucoma. The Bruchs membrane opening minimum rim width (BMO-MRW) has been proposed as a reproducible assessment of the optic nerve. The BMO-MRW measures the minimum distance from the BMO to the internal limiting membrane. We propose an approach to correct the BMO-MRW using the BMO size for increased accuracy in interindividual comparisons in future studies. Eighty-one healthy patients received SPECTRALIS spectral domain optical coherence tomography measurements for the peripapillary RNFLT and BMO-MRW. We calculated a BMO size-corrected BMO-MRW using the mean BMO size of our cohort. BMO size was defined using the manufacturer-provided BMO area and manually measured BMO perimeter. We observed that the BMO-MRW correlated highly with the perimeter (r = −0.553, p < 0.0001) and the area of the BMO (r = −0.546, p < 0.0001). Using these parameters, we provided a corrected BMO size-adjusted BMO-MRW which was better correlated with the RNFLT compared to the noncorrected one (z = −3.3495, p = 0.0004). We demonstrated the dependency of the BMO-MRW on ONH size. Furthermore, we showed the superiority of the corrected BMO-MRW using either the manually measured optic nerve head perimeter or the automatically provided ONH for future studies.