Neuroimaging contrast agents in ophthalmology

Computed tomography estimation of the prevalence of neuro-ophthalmic injuries in head trauma patients seen in a tertiary health facility in Ghana

INTRODUCTION

Prevalence of traumatic brain injury (TBI) is extremely high and potentially associated with severe incapacitating consequences. Literature reports that 90% of road traffic deaths and injuries including TBI occur in low and middle-income countries including Ghana. Computed Tomography (CT) scan is the imaging modality of choice for the initial assessment of the extent of head injury. Some Neuro-ophthalmic injuries (NOI) may sometimes be ambiguous and indistinct although a serious injury with potential damaging consequences. Data on the prevalence of NOI post trauma is non-existent in Ghana to inform policy. The onus therefore lies on the Radiologist who will review the head CT scan to be very meticulous not to miss any NOI if present. We therefore decided to diligently review a large cross-sectional retrospective post trauma head CT scans for occurrence of NOI.

OBJECTIVE

To determine the incidence of NOI secondary to head trauma and the possible loss of vision thereof in a retrospective study using patients' head CT scan data from a tertiary hospital's CT centre in Cape Coast, Ghana.

METHOD

All head CT scans secondary to trauma for the period January 2016 to December 2018, were retrieved and carefully analysed. A total number of 1043 of head CT scan images were analyzed by Consultant Radiologists.

RESULTS

Results showed out of 1043 CT scans reviewed, 742 (71,1%) were males and 301 (28.9%) were females. A total of 609 (58.4%) out of the 1043 patients sustained NOIs of various anatomical types. More Males 398 (65.4%) sustained NOI than females 211 (34.6%). The incidence of NOI was more among the youth as majority 167 (27.4%) of the patients were within the 18-29 years followed by 30-39 years bracket of 148 (24.3%). Fourteen anatomical types of NOI were elicited and further analysis revealed, intra-ocular foreign body to be the highest 107 (17.6%) cases, orbital floor fractures injury was 92 (15.1%) cases, with globe rupture injury and intraocular hemorrhage recording 79 (13.0%) cases each. Optic nerve injury was the least revealing 7 (1.1%) cases. There was a relationship between the gender of patient and the propensity to sustain NOI as males were more disposed to NOI than females. Road traffic accident (RTA) was the main pervasive cause of TBI and this accounted for 71.9% of all cases, followed by fall from height 24%, and the least cause of TBI was ascribed to gunshot injury of 0.33%.

CONCLUSION

Prevalence of NOI is high. Urgent measures must therefore be implemented to reduce the RTA menace in general and to mitigate the associated NOI and possible loss of vision thereof.

Specialized Diagnostic Investigations to Assess Ocular Status in Hypertensive Diseases of Pregnancy

This review describes specialized diagnostic investigations to assess ocular status in hypertensive diseases of pregnancy. Ocular assessment can aid in early detection for prompt multidisciplinary treatment, obstetric intervention and follow-up. The investigations accurately predict the possible causes of blindness in hypertensive diseases of pregnancy. The investigations include fluorescein angiography, ophthalmodynamometry, fluorophotometry, imaging modalities, OCT, ultrasonography, doppler velocimetry and blood chemistry analysis. The review includes a summary of imaging techniques and related recent developments to assess the neuro-ophthalmic aspects of the disease. The imaging modalities have been instrumental in understanding the complex neuropathophysiological mechanisms of eclamptic seizures. The importance of blood chemistry analysis in hypertensive diseases of pregnancy has been emphasized. The investigations have made a significant contribution in improving the standards of antenatal care and reducing maternal and fetal morbidity and mortality.

Neuroimaging in ophthalmology

In the past three decades, there have been countless advances in imaging modalities that have revolutionized evaluation, management, and treatment of neuro-ophthalmic disorders. Non-invasive approaches for early detection and monitoring of treatments have decreased morbidity and mortality. Understanding of basic methods of imaging techniques and choice of imaging modalities in cases encountered in neuro-ophthalmology clinic is critical for proper evaluation of patients. Two main imaging modalities that are often used are computed tomography (CT) and magnetic resonance imaging (MRI). However, variations of these modalities and appropriate location of imaging must be considered in each clinical scenario. In this article, we review and summarize the best neuroimaging studies for specific neuro-ophthalmic indications and the diagnostic radiographic findings for important clinical entities.

Role of imaging in the management of neuro-ophthalmic disorders

Advancements in physics, computers, and imaging science in the last century have seen neuro-imaging evolving from a plain X-ray to computed tomography, magnetic resonance imaging scans, noninvasive angiography, and special sequences such as fat suppression, fluid attenuation recovery and diffusion-weighted imaging. A prompt prescription of an appropriate imaging modality and the most suitable sequence can increase the diagnostic yield, and in many instances, it can be a sight-saving and even a life-saving decision. This article discusses basic principles of neuro-imaging, its common indications, and the appropriate application in an ophthalmology practice.

Imaging for neuro-ophthalmic and orbital disease - a review

A literature review was performed by content experts in neuro-ophthalmology and neuroradiology using a systematic English-language Medline search (1994-2008) limited to articles with relevance to neuro-ophthalmic and orbital imaging. The information covered in this review includes: (i) the basic mechanics, indications and contraindications for cranial and orbital computed tomography and magnetic resonance (MR) imaging; (ii) the utility and indications for intravenous contrast, (iii) the use of specific MR sequences; (iv) the techniques and ophthalmic indications for computed tomography/MR angiography and venography; and (v) the techniques and indications for functional MR imaging, positron emission tomography scanning and single photon emission computed tomography. Throughout the review accurate and timely communication with the neuroradiologist regarding the clinical findings and suspected location of lesions is emphasized so as to optimize the ordering and interpretation of imaging studies for the ophthalmologist.

Effect of posterior capsular opacification removal on automated perimetry

PURPOSE

Although posterior capsular opacification (PCO) is a common phenomenon in a considerable number of ophthalmologic patients, no prospective controlled trials assessing its influence on automated perimetry exist. This technique continues as a standard in the diagnosis of glaucoma and neuro-ophthalmological diseases. The aim of the present report is to investigate the effect of PCO on automated visual field examination.

METHODS

A total of 26 PCO affected eyes of 26 patients had Humphrey SITA standard (program 24-2) immediately before, and between 1 and 8 weeks after Neodymium : YAG capsulotomy. The effect of learning associated with repeated testing was controlled with automated perimetry before enrollment and visual fields of the fellow eye. Best-corrected visual acuity (BCVA), intraocular pressure (IOP), and global perimetric pre- and post-laser indices were compared using the Student's t-test for paired samples. Correlation and linear regression analyses were also performed.

RESULTS

BCVA and mean deviation (MD) improved following capsulotomy. Pattern standard deviation (PSD), an indicator of localized defects in the field, also improved significantly when PCO was solved. Moreover, a strong association among BCVA, MD, and PSD was shown both prior to and after capsulotomy.

CONCLUSION

PCO is a heterogeneous mean opacity. This polymorphism may alter visual field results, and may even simulate the perimetric behaviour of other pathologies such as glaucoma. Consequently, the presence of PCO should be considered in the interpretation of any automated perimetry in pseudophakic patients. In addition, the values obtained before capsulotomy may partially predict the values obtained after capsulotomy.

A water-soluble triiodo amino acid and its dendrimer conjugate for computerized tomography (CT) imaging

Prolonging the circulation of an imaging agent is vital for making it suitable for blood pool (vascular) imaging. Medical applications of vascular imaging include cardiovascular disease, abnormal capillary permeability, and tumor neovascularity. As low molecular weight computerized tomography (CT) enhancement agents are characterized by inconveniently fast clearance, macromolecular compounds (both natural and synthetic) have gained a wide recognition for possessing better characteristics for performing blood imaging tasks. Herein, the syntheses and characterization of a new water-soluble triiodo amino acid, 3-[(N,N-dimethylaminoacetyl) amino]-?-ethyl-2,4,6-triiodobenzenepropanoic acid (DMAA-IPA) and its Starburst PAMAM generation 4.0 dendrimer conjugate, G-4-(DMAA-IPA)37 are described. The applicability of G-4-(DMAA-IPA)37 as a potential macromolecular angiographic CT contrast agent is discussed. The linear relationship between organically bound iodine concentration and CT Hounsfield units has been established thus allowing for quantification uses of CT imaging as well.

Imaging for neuro-ophthalmic and orbital disease

PURPOSE

To provide an update on imaging of the brain and orbit for ophthalmologists.

DESIGN

Literature review.

METHODS

A systematic English-language medline search and summary of recent literature on imaging of brain and orbit was performed.

RESULTS

Computed tomography and magnetic resonance (MR) scanning are the mainstays for the evaluation of most disorders involving the brain and orbit. Computed tomography angiography and magnetic resonance angiography are relatively newer applications that are useful for the evaluation of arterial and venous disorders. Special sequences such as fat suppression and fluid attenuation inversion recovery are useful techniques for specific ophthalmic indications. Diffusion weighted imaging and perfusion-weighted imaging are improving the evaluation of acute stroke. Functional MRI, positron emission tomography scanning and single photon emission computed tomography may provide useful information regarding brain or tumor metabolism. Magnetic resonance spectroscopy has expanded our knowledge of brain function. Newer imaging studies have improved our diagnostic abilities on many fronts, including new sequences, new applications of imaging studies, and functional imaging of brain.

CONCLUSION

New imaging techniques for brain and orbit have an increased potential for improving diagnostic yield. Accurate and timely communication with the neuroradiologist can optimize the prescription and interpretation of imaging in ophthalmology.