Blue Investigations 1 Flashcards
(26 cards)
What is Vogt-Koyanagi-Harada (VKH) disease, and what are its phases?
VKH is a bilateral granulomatous uveitis disorder with phases: prodrome, acute, convalescent, and recurrent, associated with systemic manifestations like headache, meningism, tinnitus, poliosis, and vitiligo.
What differentiates VKH from posterior scleritis on ultrasound B-scan?
VKH shows absence of the T-sign on ultrasound B-scan, unlike posterior scleritis, which has sub-Tenon’s fluid causing the T-sign.
How does lymphoma compare to VKH in diagnosis?
Lymphoma is a masquerade disease but can be excluded by cerebrospinal fluid (CSF) findings and systemic features, unlike VKH which has specific systemic features like poliosis and vitiligo.
What distinguishes sympathetic ophthalmia from VKH?
Sympathetic ophthalmia is a bilateral granulomatous disorder not associated with systemic disease, and it requires a history of trauma or intraocular surgery for diagnosis, unlike VKH.
What are the features of classic and predominantly classic CNVM?
Classic CNVMs show early bright or lacy hyperfluorescence followed by late leakage, and predominantly classic lesions have at least 50% of the lesion formed by classic CNV.
How are occult CNVM membranes classified and what do they show on FFA?
Occult CNVM membranes are classified as fibrovascular PEDs or late leakage of undetermined origin, showing stippled or irregular hyperfluorescence followed by leakage in later stages of the angiogram.
Where are classic and occult CNVM membranes located?
Classic CNVM membranes are in the subretinal space (type 2), while occult membranes are located in the subretinal pigment epithelium (type 1).
What does NICE recommend for tuberculosis testing?
NICE guidelines recommend Mantoux skin testing and G-IFN (Quantiferon®) blood test, which measures T-cell release of G-IFN upon exposure to M. tuberculosis antigens.
How does G-IFN testing compare to Mantoux testing?
G-IFN testing is not influenced by prior BCG vaccination, while Mantoux testing is, and it is used to indicate prior exposure, not active disease.
Can G-IFN distinguish between active and latent tuberculosis?
No, G-IFN cannot distinguish between active and latent tuberculosis; it only indicates prior exposure and remains positive even after a full course of antituberculous therapy.
What are the stages of fluorescein angiography (FFA) progression?
FFA progresses through choroidal flush, arterial, arteriovenous, venous, and late re-circulation stages.
What is the arm-eye time in fluorescein angiography (FFA), and what does a delay indicate?
The arm-eye time is 10–12 seconds, and a delay can reflect cardiovascular disease, such as carotid disease, and is seen in ocular ischemic syndrome.
What OCT feature is indicative of hydroxychloroquine maculopathy?
The ‘flying saucer’ sign, with preservation of central foveal outer retinal structures and perifoveal thinning, is indicative of hydroxychloroquine maculopathy.
What is the primary use of blood agar in microbiology culture?
Blood agar is used for growing most bacteria and fungi.
What is the main purpose of brain heart infusion agar?
Brain heart infusion agar is used for growing streptococci and meningococci.
What does Sabouraud dextrose agar culture?
Sabouraud dextrose agar is used for culturing fungi.
How does ultrasound frequency affect image resolution and penetration?
Higher frequency and shorter wavelength are associated with higher resolution but poorer penetration, with UBM using 50–100 MHz and B-scan using 8–10 MHz.
What does fundus autofluorescence (FAF) indicate?
Hyper-FAF indicates dysfunctional retinal pigment epithelium, while hypo-FAF indicates optic disc abnormalities such as in adult vitelliform.
Why is indocyanine green (ICG) considered a relative contraindication in pregnancy?
ICG is considered a relative contraindication in pregnancy due to the lack of safety data, and it is also contraindicated in patients with iodine allergy.
What is the wavelength of light used in anterior segment OCT compared to posterior segment OCT?
Anterior segment OCT uses 1310 nm, while posterior segment OCT uses 800 nm.
What effect does silicone oil have on axial length measurement in ultrasound?
Silicone oil slows ultrasound, potentially causing an artifactually longer axial length if the correct setting is not used.
What is the role of visual evoked potential (VEP) testing?
VEP records the electrical response from the visual cortex and is used to detect optic nerve demyelination, chiasmal dysfunction, and non-organic visual loss.
How does Orbscan differ from Pentacam in corneal imaging?
Orbscan uses slit-scanning and Placido disc technology, while Pentacam uses a rotating Scheimpflug camera and a monochromatic slit-light source.
What is the advantage of the Lees screen test over the Hess screen test?
The Lees screen test does not require normal colour vision and uses opalescent glass screens, making it suitable for patients with abnormal retinal correspondence.
