164 research outputs found
Reply to comment on: Distinct differences in anterior chamber configuration and peripheral aberrations in negative dysphotop
Neuro Imaging Researc
Effect of anatomical differences and intraocular lens design on negative dysphotopsia
Purpose: To assess the effect of ocular anatomy and intraocular lens (IOL) design on negative dysphotopsia (ND).Setting: Department of Ophthalmology, Leiden University Medical Center, Leiden, the Netherlands.Design: Ray-tracing study based on clinical data.Methods: Ray-tracing simulations were performed to assess the effect of anatomical differences and differences in IOL design on the peripheral retinal illumination. To that end, eye models that incorporate clinically measured anatomical differences between eyes of patients with ND and eyes of pseudophakic controls were created. The anatomical differences included pupil size, pupil centration, and iris tilt. The simulations were performed with different IOL designs, including a simple biconvex IOL design and a more complex clinical IOL design with a convex-concave anterior surface. Both IOL designs were analyzed using a clear edge and a frosted edge. As ND is generally considered to be caused by a discontinuity in peripheral retinal illumination, this illumination profile was determined for each eye model and the severity of the discontinuity was compared between eye models.Results: The peripheral retinal illumination consistently showed a more severe discontinuity in illumination with ND-specific anatomy. This difference was the least pronounced, 8%, with the frosted edge clinical IOL and the most pronounced, 18%, with the clear edge biconvex IOL.Conclusions: These results show that small differences in the ocular anatomy or IOL design affect the peripheral retinal illumination. Therewith, they can increase the severity of ND by up to 18%. Copyright (c) 2022 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of ASCRS and ESCRSOphthalmic researc
Dose fractionation effects in primary and metastatic human uveal melanoma cell lines
PURPOSE: To investigate the effects of split-dose irradiation on primary
and metastatic uveal melanoma cell lines, with a clonogenic survival
assay. METHODS: Appropriate cell concentrations of four primary and four
metastatic human uveal melanoma cell lines were cultured for irradiation
with single doses and with two equal fractions separated by 5 hours. After
irradiation, colony formation was allowed for 7 to 21 days. Two cutaneous
melanomas were also tested for comparison. All survival curves were
analyzed using the linear quadratic (LQ) model. Specific parameters for
the intrinsic radiosensitivity (alpha-component, SF2), for the capacity of
repair of DNA damage (beta-component), as well as the alpha/beta ratio
were calculated. RESULTS: After single-dose irradiation a wide range in
the values of the alpha- and beta-component was obtained for both primary
and metastatic uveal melanomas, which resulted in a wide range of
alpha/beta ratios. In contrast, calculations based on split-dose data,
with which the beta-component could be estimated independent of the
alpha-component, indicated that estimates for the capacity of sublethal
DNA damage repair was very similar in all cell lines. This indicated that
intrinsic factors dominated the radiosensitivity of these cell lines.
Split-dose irradiation had little influence on the intrinsic
radiosensitivity (alpha-component), but cell survival increased for all
cell lines. For the two cutaneous melanomas comparable split-dose results
were obtained. CONCLUSIONS: For both primary and metastatic uveal melanoma
cell lines, data from single and fractionated doses indicate large
variations in radiosensitivity, which are mainly dominated by the
intrinsic radiosensitivities. Doses of approximately 8 Gy in five
fractions would be sufficient to eradicate 10(9) cells (approximately 1
cm3) of the most radioresistant tumor cell lines, but this schedule is an
overkill for the radiosensitive tumor cell lines. Based on specific
morphologic and histologic tumor markers, more individualized dose
fractionation schedules could improve the therapeutic ratio for uveal
melanomas
MRI-based 3D retinal shape determination
Objective To establish a good method to determine the retinal shape from MRI using three-dimensional (3D) ellipsoids as well as evaluate its reproducibility.Methods and analysis The left eyes of 31 volunteers were imaged using high-resolution ocular MRI. The 3D MR-images were segmented and ellipsoids were fitted to the resulting contours. The dependency of the resulting ellipsoid parameters on the evaluated fraction of the retinal contour was assessed by fitting ellipsoids to 41 different fractions. Furthermore, the reproducibility of the complete procedure was evaluated in four subjects. Finally, a comparison with conventional two-dimensional (2D) methods was made.Results The mean distance between the fitted ellipsoids and the segmented retinal contour was 0.03 +/- 0.01 mm (mean +/- SD) for the central retina and 0.13 +/- 0.03 mm for the peripheral retina. For the central retina, the resulting ellipsoid radii were 12.9 +/- 0.9, 13.7 +/- 1.5 and 12.2 +/- 1.2 mm along the horizontal, vertical and central axes. For the peripheral retina, these radii decreased to 11.9 +/- 0.6, 11.6 +/- 0.4 and 10.4 +/- 0.7 mm, which was accompanied by a mean 1.8 mm posterior shift of the ellipsoid centre. The reproducibility of the ellipsoid fitting was 0.3 +/- 1.2 mm for the central retina and 0.0 +/- 0.1 mm for the peripheral retina. When 2D methods were used to fit the peripheral retina, the fitted radii differed a mean 0.1 +/- 0.1 mm from the 3D method.Conclusion An accurate and reproducible determination of the 3D retinal shape based on MRI is provided together with 2D alternatives, enabling wider use of this method in the field of ophthalmology.Neuro Imaging Researc
Evaluation of intraocular lens position and retinal shape in negative dysphotopsia using high-resolution magnetic resonance imaging
Purpose: To assess potential relationships of intraocular lens (IOL) position and retinal shape in negative dysphotopsia (ND). Setting: Department of Ophthalmology, Leiden University Medical Center, Leiden, the Netherlands. Design: Case-control study. Methods: High-resolution ocular magnetic resonance imaging (MRI) scans were performed in patients with ND and pseudophakic controls, and subsequently used to determine the displacement and tilt of the in-the-bag IOL about the pupil and iris. In addition, anterior segment tomography was used to assess the iris-IOL distance. Furthermore, the retinal shape was quantified from the MRI scans by fitting an ellipse to the segmented inner boundary of the retina. Both the IOL position and retinal shape were compared between groups to assess their potential role in the etiology of ND. Results: In total, 37 patients with ND and 26 pseudophakic controls were included in the study. The mean displacement and tilt of the IOL were less than 0.1 mm and 0.5 degrees, respectively, in both groups and all directions. The corresponding mean iris-IOL distance was 1.1 mm in both groups. Neither of these values differed statistically significantly between groups (all P values >.6). The retinal shape showed large variations but was not statistically significantly different between the groups in both the left-right (P = .10) and the anterior-posterior (P = .56) directions. Conclusions: In this study, the in-the-bag IOL position and retinal shape did not statistically significantly differ between patients with ND and the general pseudophakic population. Given the large variation in retinal shape between subjects, however, it could still be an important factor in a multifactorial origin of ND.Neuro Imaging Researc
Cellular radiosensitivity of primary and metastatic human uveal melanoma cell lines
PURPOSE: To investigate the radiosensitivity of uveal melanoma cell lines
by a clonogenic survival assay, to improve the efficiency of the radiation
regimen. METHODS: Four primary and four metastatic human uveal melanoma
cell lines were cultured in the presence of conditioned medium. After
single-dose irradiation (0-12 Gy), colonies were allowed to form for 6 to
14 days. Two cutaneous melanomas cell lines were also tested for
comparison. The survival curves were analyzed by the linear quadratic (LQ)
model, and the surviving fraction at a dose of 2 Gy (SF(2)), the SF at 10
Gy (SF(10)), the ratio of initial irreparably damaged DNA
(alpha-coefficient) to the capacity to repair sublethally damaged DNA
(beta-coefficient), and the plating efficiency were calculated. RESULTS:
The melanomas displayed a wide range of initial irreparable DNA damage
(alpha-component), as well as a capacity for repair of sublethal DNA
damage (beta-component), which ultimately resulted in a wide range of
alpha/beta ratios. These findings were similar in both primary and
metastatic melanomas and were comparable with data obtained from two
cutaneous melanomas. CONCLUSIONS: Cell lines obtained from primary and
metastatic human uveal melanomas displayed a wide range of
radiosensitivity, similar to that published for cutaneous melanomas.
Translating these data to the clinical setting indicates that a
fractionated dose of 8 to 10 Gy administered in three to four fractions,
as currently delivered in many centers, should be sufficient to eradicate
tumors of approximately 1 cm(3)
Two-year results after combined phacoemulsification and iris-fixated phakic intraocular lens removal
Purpose To describe and present results after a technique for cataract surgery combined with explantation of an iris-fixated phakic intraocular lens (IF-pIOL).Methods The medical records of all patients, who had undergone cataract surgery combined with IF-pIOL explantation and subsequent implantation of a posterior chamber IOL by the Single Incision Technique (SIT), were reviewed. Data collection included preoperative and postoperative corrected distance visual acuity (CDVA), manifest refraction, and endothelial cell density (ECD) up to a follow-up time of 24 months.Results Fifty myopic eyes (34 patients) and 9 hyperopic eyes (6 patients) had undergone a SIT procedure mainly because of cataract (67%). Postoperative CDVA improved in both the myopic eyes to 0.16 +/- 0.37 logMAR, as in the hyperopic eyes to - 0.10 +/- 0.55 logMAR with no eyes having loss of Snellen lines. Mean postoperative spherical equivalent was - 0.34 +/- 0.72 D and - 0.10 +/- 0.55 D, respectively. ECD loss 6 months after surgery was 5% and remained stable thereafter.Conclusion SIT for combined phacoemulsification and IF-pIOL removal yields good visual and refractive results and is a safe procedure in regard to ECD loss. The technique has advantages over the conventional procedure and is easy to perform.Neuro Imaging Researc
A comparison of 3 T and 7 T MRI for the clinical evaluation of uveal melanoma
Background Magnetic resonance imaging (MRI) is increasingly being used in the diagnosis and treatment planning of uveal melanoma (UM), the most common primary intraocular tumor. Initially, 7 T MRI was primarily used, but more recently these techniques have been translated to 3 T, as it is more commonly available. Purpose Compare the diagnostic performance of 3 T and 7 T MRI of UM. Study Type Prospective. Population Twenty-seven UM patients (19% female). Field Strength/Sequence 3 T: T1- and T2-weighted three-dimensional (3D) spin echo (SE) and multi-slice (MS) SE, 7 T: T1-weighted 3D gradient echo (GE), T2-weighted 3D SE and MS SE, 3 T and 7 T GE dynamic contrast-enhanced. T1 weighted images: acquired before and after Gadolinium (Gd) administration. Assessment For all sequences, scan and diagnostic quality was quantified using a 5-point Likert scale. Signal intensities on T1 and T2 relative to choroid and eye muscle respectively were assessed as well as the tumor prominence. Finally, the perfusion time-intensity curves (TICs) were classified as plateau, progressive, or wash-out. Statistical Tests Image quality scores were compared between both field strengths using Wilcoxon signed-rank and McNemar tests. Paired t-tests and Bland-Altman were used for comparing tumor prominences. P < 0.05 was considered statistically significant. Results Image quality was comparable between 3 T and 7 T, for 3DT1, 3DT2, 3DT1Gd (P = 0.86; P = 0.34; P = 0.78, respectively) and measuring tumor dimensions (P = 0.40). 2DT1 and 2DT2 image quality were rated better on 3 T compared to 7 T. Most UM had the same relative signal intensities at 3 T and 7 T on T1 (17/21) and T2 (13/17), and 16/18 diagnostic TICs received the same classification. Tumor prominence measurements were similar between field strengths (95% confidence interval: -0.37 mm to 0.03 mm, P = 0.097). Data Conclusion Diagnostic performance of the evaluated 3 T protocol proved to be as capable as 7 T, with the addition of 3 T being superior in assessing tumor growth into nearby anatomical structures compared to 7 T. Level of Evidence 2 Technical Efficacy Stage 3Neuro Imaging Researc
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