Blue Investigations 2 Flashcards
(15 cards)
What is the AC/A ratio, and what is its normal value?
The AC/A ratio measures the convergence induced by accommodation for every dioptre of accommodation, and its normal value is around 3–5 degree/dioptre.
How is the AC/A ratio measured?
The AC/A ratio can be measured using the gradient method (with a minus or plus lens) or the heterophoria method using the formula: AC/A = IPD + near fixation distance × (near phoria – distance phoria).
What is the significance of a high AC/A ratio in diagnosing IDEX?
A high AC/A ratio in simulated IDEX can mask near exotropia, which can be unmasked by a patch test or a +3.0 D lens.
What imaging methods are used to detect intracranial aneurysms?
Both CT angiogram (CTA) and MR angiogram (MRA) can detect intracranial aneurysms, with CTA being more sensitive in detecting small unruptured aneurysms.
What visual field defect is commonly caused by a pituitary adenoma?
Pituitary adenomas often cause bitemporal hemianopia due to compression of the optic chiasm.
What is the typical imaging finding in patients with pituitary adenomas?
MRI with contrast typically shows a hypodense region on T1 imaging, with homogeneous enhancement on T2, and sometimes a cystic component.
What is septo-optic dysplasia (SOD), and what is its classic triad?
Septo-optic dysplasia (SOD) is a neurological disorder characterized by optic nerve hypoplasia, pituitary hormone abnormalities, and midline brain defects such as agenesis of the septum pellucidum and/or corpus callosum.
What are the diagnostic features of septo-optic dysplasia (SOD)?
A coronal MRI showing the absence of the septum pellucidum is a diagnostic feature of SOD, along with optic nerve hypoplasia and pituitary hormone abnormalities.
How does septo-optic dysplasia (SOD) affect vision?
Around 20–30% of SOD patients experience significant visual impairment, which may present with strabismus, nystagmus, or other visual abnormalities.
What role does multidisciplinary care play in managing septo-optic dysplasia (SOD)?
Multidisciplinary care, including ophthalmologists, endocrinologists, pediatricians, and neurodevelopmental teams, is essential in managing SOD patients.
What is the difference between MRI FLAIR and T2-weighted sequences?
MRI FLAIR sequence is similar to T2-weighted imaging but can suppress signals from cerebrospinal fluid (CSF), highlighting periventricular hyperintense lesions such as multiple sclerosis plaques.
Why is imaging important in a patient with new onset Horner’s syndrome, especially if painful?
Imaging is important because the sympathetic pathway to the iris dilator muscle is long, and any interruption could cause a Horner’s lesion, such as from carotid artery dissection.
What imaging study is recommended for a patient with painful Horner’s syndrome?
The recommended imaging is a study to evaluate the entire sympathetic pathway of the head, neck, and upper chest to T2, followed by an MRA of the head and neck, or alternatively, CT and CTA in an emergency setting.
What is DSG (dacryoscintigraphy), and how is it used in diagnosing epiphora?
DSG involves administering a radioactive tracer to the inferior fornix and imaging the patient while they blink. It helps diagnose functional epiphora due to proximal or distal obstruction of the nasolacrimal drainage system.
How does a dacryocystogram differ from DSG in diagnosing nasolacrimal drainage issues?
In a dacryocystogram, a radio-opaque contrast is injected via the puncta, and the patient is supine. It may mask proximal obstruction, unlike DSG, which can assess both proximal and distal obstructions.
