Comparison of lacrimal gland dimensions and volume in unilateral Ahmed glaucoma valve versus trabeculectomy

PURPOSE

To evaluate radiographic lacrimal gland (LG) volume and dimensions in Ahmed glaucoma valve (AGV)- versus trabeculectomy-treated eyes and contralateral non-treated eyes.

METHODS

In this retrospective cohort study, 1616 medical records acquired between 2010 and 2020 were examined. In AGV-treated (group 1) eyes, there were 19 patients with records sufficient for radiological LG evaluation, and in trabeculectomy-treated (group 2) eyes, there were 18. The hospital workstation software was used to assess high-resolution computed tomography (HRCT) scans conducted under standard protocol using a 128 SL Optima CT 660 scanner. The software (Vitrea™) was used to perform semi-quantitative volumetric measurements. LG dimensions were obtained in the axial and reformatted coronal planes on each side, and four measures were generated using the widest LG tip-to-tip diameters in two planes: coronal length, coronal width (CW), axial length (AL), and axial width.

RESULTS

The time interval between surgery and HRCT imaging was 50.97 ± 26.25 months. Group 1 had significantly lower LG volume than group 2 (594.11 ± 259.45 vs. 933.67 ± 294.09 mm3, P = 0.001). When compared to non-treated eyes, AGV-treated eyes had lower LG volume (P = 0.065) while trabeculectomy-treated eyes had higher LG volume (P = 0.031). Further, group 1 had decreased length and width in both the axial and coronal planes as compared to group 2, with AL and CW being significantly different (P < 0.05).

CONCLUSIONS

AGV and trabeculectomy had varied impacts on LG volume and dimensions despite being conducted in the same quadrant. HRCT appears to be effective in analysing AGV position, which may be related to LG volumetric and dimensional issues.

Misdiagnosis of Orbital Foreign Body as Glaucoma Drainage Device

BACKGROUND

Sight-threatening complications from retained orbital and intraocular foreign bodies are frequently reported in literature. Delays in diagnosis can result in severe complications, including choroidal neovascularization, infection, and irreversible vision loss. Therefore, it is imperative that emergency physicians consider the possibility of orbital and intraocular foreign bodies when evaluating patients with acute facial trauma.

CASE REPORT

A 91-year-old woman with a history of laser-treated glaucoma and cataracts presented to an outside emergency department after a ground-level fall. A maxillofacial noncontrast computed tomography scan showed no facial fractures or hemorrhage, but a 41 mm × 4 mm foreign body within the intraconal compartment of the right orbit was identified. The object was presumed to be an implanted glaucoma drainage device, and the patient was discharged without antibiotics. One day after discharge, the patient developed right periorbital swelling and erythema with increasing purulent discharge and skin thickening, ultimately requiring transfer to our facility for management of complex right orbital cellulitis, orbital compartment syndrome, and surgical foreign body removal. Despite globe exploration and surgical intervention, the patient developed a frozen globe with no light perception in the right eye. Why Should an Emergency Physician Be Aware of This? Subtle ophthalmologic emergencies such as sight-threatening foreign bodies can be challenging to diagnose on imaging, particularly with the advent of implantable ocular technology. When an orbital foreign body is discovered in the context of facial trauma, early ophthalmology consultation should be considered.

Peripheral Retinal Leakage after Intravenous Administration of a Gadolinium-based Contrast Agent: Age Dependence, Temporal and Inferior Predominance and Potential Implications for Eye Homeostasis

PURPOSE

Peripheral retinal leakage (PRL) of contrast medium from the ora serrata (i.e., the peripheral part of the retina) was recently reported in normal eyes using ultra-widefield fluorescein angiography. We occasionally see PRL of gadolinium-based contrast agents (GBCAs) in the vitreous from the temporal and inferior sides of the ora serrata on MR images of subjects without ophthalmic disease. In this study, we retrospectively evaluated these MR images to determine if PRL was associated with aging. We also evaluated whether the initial leakage appeared in the temporal and inferior sides, and whether there was uniform distribution within the vitreous after 24 hours.

METHODS

In 127 subjects (9 volunteers, 85 patients with sudden deafness, and 33 patients with a suspicion of endolymphatic hydrops), pre- and post-contrast-enhanced heavily T2-weighted 3D-fluid attenuated inversion recovery (FLAIR) images were obtained. The presence or absence of PRL was subjectively evaluated. For patients with a suspicion of endolymphatic hydrops, 3D-real inversion recovery (IR) images were also obtained at pre-, 10 mins, 4 hours, and 24 hours after intravenous administration (IV) of GBCA. Four circular ROIs were placed in the vitreous humor and the signal intensity was measured.

RESULTS

In the cases with PRL (n = 88) and without PRL (n = 47), the median age was 59 and 47 years, respectively (P = 0.001). At 4 hours after IV-GBCA, the mean signal increase in the inferior temporal ROI was greater than all the other ROIs. At 24 hours after IV-GBCA, no significant difference in signal intensity was observed for the four ROIs.

CONCLUSION

PRL of GBCA is age-dependent and occurs mainly from the inferior temporal side of the ora serrata. The contrast effect was uniformly distributed at 24 hours after IV-GBCA. Future observations in a variety of diseases will determine the clinical significance of these findings.

Imaging of the post-operative orbit and associated complications

Dedicated post-operative radiological evaluation following ophthalmologic procedures is relatively uncommon. However, given the ever-growing ophthalmologic procedural advancements and the increasing utilization of neuroimaging for myriad indications, the orbits are often imaged incidentally in a delayed post-procedural state. Regardless of the clinical scenario, it is important for neuroradiologists and other specialists commonly exposed to orbital imaging to be aware of both expected and abnormal post-operative imaging findings because misinterpreted normal features or unrecognized complications can result in vision-threatening delays in treatment or mismanagement. In this review article, we discuss many common ophthalmologic procedures, their indications, and most likely complications. We also provide illustrative operative photographs and radiological imaging examples. By understanding the surgical intent, recognizing the devices that are commonly used, and developing familiarity with the appearance of post-operative complications, pitfalls in interpretation can be avoided and patient outcomes ultimately improved.

Evaluation of intraocular gas using magnetic resonance imaging after pars plana vitrectomy with gas tamponade for rhegmatogenous retinal detachment

We used magnetic resonance imaging (MRI) to assess how a patient’s posture affects intraocular gas changes and whether the postoperative prone position is required after pars plana vitrectomy (PPV) with gas tamponade for rhegmatogenous retinal detachments (RRDs). Eight patients with RRDs who underwent PPV combined with cataract surgery with gas tamponade were prospectively included. They underwent MRI examination both in the prone and supine positions. We separated the retina into four parts: superior–posterior, superior–anterior, inferior–posterior, and inferior–anterior. We then calculated the gas contact rate as (the length of the retina contacting the gas in each retinal part) divided by (the length of each retinal part) × 100% in both the prone and supine positions. The mean gas contact rate of the superior–anterior part of the retina was significantly higher (P = 0.006) in the supine position than in the prone position. The mean gas contact rate of the inferior–anterior part of the retina was also significantly higher (P = 0.0004) in the supine position than in the prone position. We believe that if all retinal breaks were located anterior to the equator, the supine position may provide better tamponade gas coverage for the breaks than the prone position. Although potential postoperative complications caused by the supine position require careful attention, our result may shorten the duration of postoperative prone position and may decrease the patients’ discomfort after PPV with gas tamponade for RRDs.

MRI safety and devices: An update and expert consensus

The use of magnetic resonance imaging (MRI) is increasing globally, and MRI safety issues regarding medical devices, which are constantly being developed or upgraded, represent an ongoing challenge for MRI personnel. To assist the MRI community, a panel of 10 radiologists with expertise in MRI safety from nine high-volume academic centers formed, with the objective of providing clarity on some of the MRI safety issues for the 10 most frequently questioned devices. Ten device categories were identified. The panel reviewed the literature, including key MRI safety issues regarding screening and adverse event reports, in addition to the manufacturer's Instructions For Use. Using a Delphi-inspired method, 36 practical recommendations were generated with 100% consensus that can aid the clinical MRI community. Level of Evidence: 5 Technical Efficacy Stage: 5 J. Magn. Reson. Imaging 2020;51:657-674.

Evaluation of select biocompatible markers for labelling peripheral nerves on 11.7 T MRI

BACKGROUND

Peripheral nerve injury is often followed by a highly variable recovery process with respect to both rapidity and efficacy. Identifying post-nerve injury phenomena is key to assessing the merit and timing of surgery as well as to tracking nerve recovery postoperatively. Diffusion Tensor Imaging (DTI) has been investigated in the clinical and research settings as a noninvasive technique to both assess and monitor each patient's unique case of peripheral nerve damage.

NEW METHOD

We identify a MRI-suitable marker for tracking the exact site of either nerve injury or coaptation following surgical repair to aid with DTI analysis.

RESULTS

Due to artefact and disruption of tractography, silver wire and microvascular clips were not suitable markers. AxoGuard®, 4-0 vicryl suture, and 10-0 polyamide suture, although detectable, did not produce a signal easily distinguished from post-surgical changes. Silicone was easily identifiable and stable in both the acute and delayed time points, exhibited negligible impact on DTI parameters, and possessed geometry to prevent nerve strangulation.

COMPARISON WITH EXISTING METHOD

Prior studies have not assessed the efficacy of other markers nor have they assessed silicone for potential artefact with DTI parameter analysis. Furthermore, this work demonstrates the reliability and compatibility of silicone in the delayed postoperative time period and includes its unique imaging appearance on high-resolution 11.7 MRI.

CONCLUSION

Semi-cylindrical silicone tubing can be used as a safe, reliable, and readily available radiological marker to visualize and monitor a region of interest on a rodent's peripheral nerve for aiding assessments with diffusion tensor imaging.

Lacrimal Gland Changes on Orbital Imaging after Glaucoma Drainage Implant Surgery

PURPOSE

This study evaluates the radiographic appearance of lacrimal gland tissue after placement of a glaucoma drainage implant (GDI) to characterize the impact of the device on the gland's imaging patterns.

METHODS

We performed retrospective chart review of departmental records at two urban academic medical centers, which were systematically searched using procedure codes to identify adult glaucoma patients who underwent unilateral superotemporal GDI from January 1995 to December 2015. Radiology records were cross-checked to identify the subset of patients who underwent postoperative orbital CT or MRI. Chart review collected data on glaucoma diagnosis, management, examination findings, and clinical complaints. Imaging studies were reviewed for orbital changes using qualitative assessment of the radiographic appearances and computer-guided calculations to quantify asymmetries.

RESULTS

A review of all eye operations in the inclusion period identified 315 patients with GDI, 13 of whom were eligible for inclusion. Elapsed time from device placement to imaging averaged 41.9 months, and the average clinical follow-up was 56.4 months. Radiographic lacrimal gland changes were appreciable in 69% (9 of 13) of patients, most commonly with posterior displacement and flattening of the gland (7 of 13). ImageJ analysis revealed significantly smaller lacrimal glands in orbits with GDI (P = 0.04). No clear correlation was found between gland changes and clinical dry eye symptoms.

CONCLUSION

GDI placement was associated with radiographically-appreciable lacrimal gland changes in two-thirds of patients, with changes occurring in a predictable pattern of lacrimal gland flattening, posteriorization, and volume loss. Radiographic changes correlated with clinical symptoms in few patients.

Histopathologic Findings of Linear Scleroderma Displaying Focal Trichiasis Secondary to Tarsal Thinning

Linear scleroderma en coup de sabre with ophthalmic findings has been previously described in the literature on numerous occasions. A 57-year-old woman presented with focal trichiasis secondary to tarsal thinning, adjacent to a linear brow and forehead deformity consistent with linear scleroderma en coup de sabre. Cases of linear scleroderma en coup de sabre involving the eyelids have been reported, most often with madarosis, ptosis, or skin atrophy; however, to the authors' knowledge, this is the first reported case of linear scleroderma associated with trichiasis and involvement of the deeper eyelid tissues, particularly the tarsus.

FDG-PET/CT Focal Uptake on an Ocular Prosthesis

We present a case of an unexpected focally increased radiotracer uptake in an artificial eye in an FDG-PET/CT scan that was performed on a woman with a history of choroidal melanoma. It is crucial to know the type of prosthesis used and the timing of replacement for a correct interpretation of the findings. Recently, an FDG PET/CT was proposed to monitor the vascularity of the prosthesis instead of gadolinium MRI or of Tc bone scintigraphy.

Magnetic Resonance Imaging Characteristics of a Baerveldt Glaucoma Implant

PURPOSE

Evaluate for normative postoperative magnetic resonance imaging (MRI) characteristics of a Baerveldt Glaucoma Implant (BGI).

DESIGN

Prospective case series.

PARTICIPANTS

Seven subjects with uncontrolled glaucoma requiring a primary superotemporal BGI.

METHODS

Subjects prospectively underwent sequential MRI orbital scans without contrast at 0 to 2 weeks, 6 to 8 weeks, and 4 to 6 months after implantation of a BGI model 103-250. Masked to the postoperative time course, a radiologist measured bleb and implant characteristics.

MAIN OUTCOME MEASURES

Linear measurements of the maximum bleb height at the anterior, middle, and posterior sections of the endplate were measured. Intraocular pressure (IOP) was correlated to bleb height.

RESULTS

On axial T2-weighted images, the height of fluid below and above the BGI endplate increased from the initial to the final MRI images: 0.49 mm to 1.83 mm and 0.57 mm to 1.08 mm (middle 1/3), respectively. On coronal T2-weighted images, fluid below and above the BGI endplate increased from 0.47 mm to 1.53 mm and 0.49 mm to 1.38 mm, respectively. Maximum inverse correlation between bleb height and IOP was observed at the 6 to 8 week coronal T2 images (r=-0.963, P=0.002).

CONCLUSIONS

Fluid collections and endplate characteristics are easily visualized with MRI. Dynamic changes occur over the early postoperative time course. Bleb height is inversely correlated to IOP at 6 to 8 weeks, but disappears at 4 to 6 months.

Imaging characteristics of the postoperative globe: a pictorial essay

Recognizing imaging characteristics after ophthalmic surgery is necessary for radiologists to prevent misdiagnosis. We review typical appearances of intraorbital implanted devices and materials on CT and MRI with demonstration of the common surgical procedures. EX-PRESS glaucoma filtration devices appear as punctate areas of metal attenuation on CT and are typically placed at the corneoscleral junction. The imaging manifestations after cataract extraction are absence of the native lens of ovoid mass and the intraocular lens with high attenuation on CT and low signal intensity on MRI. The treatment of retinal detachment is achieved with intraocular tamponade or scleral buckling. In intraocular tamponade, the eye is filled with a bubble of gas or silicone oil. Gas results in air attenuation on CT and low signal intensity on MRI in the vitreous cavity. Silicone oil is hyperattenuating on CT and has variable intensity on MRI. In scleral buckling, the eye wall is indented with silicone buckling elements that show high or low attenuation on CT and low T1- and T2-weighted intensity on MRI. Degraded hydrogel buckling elements appear as swollen masses showing low attenuation on CT and high T2-weighted intensity on MRI.