Investigations Flashcards
(65 cards)
When an OCT is performed, you find significant pockets in the macula but there is an absence of leakage on FFA. Which of the following is most likely the condition?
X-linked retinoschisis
would cause foveal schisis, where there is spoke-like folds separating cystoid spaces. It could superficially resemble cystoid macular oedema but there is absence of leakage on FFA. These patients may also later get non-specific atrophy, peripheral retinal schisis and/or inner leaf breaks and complications may include vitreous haemorrhage and retinal detachment.
The other conditions listed would leak on FFA.
Central serous chorioretinopathy would show neurosensory retinal detachment and small PED(s) and the architecture of the overlying retinal architecture is typically intact but in severe and chronic cases there may be cystoid degeneration. FFA would demonstrate ≥ 1 points of progressive leakage and pooling, classically in what is described as a “smoke-stack” or “ink-blot” pattern.
If there are signs of disease activity, AMD would show presence of intraretinal and/or subretinal fluid and/or sub-RPE fluid, but the pattern of leakage on FFA would depend on the type of CNV. Types based on location of CNV:
Type 1 'occult' CNV: Sub-RPE; OCT: irregular elevation of the RPE (fibrovascular PED), SRF and IRF; FFA: (1) stippled hyperfluorescence with associated leakage and pooling in first 1-2 minutes, or (2) late leakage of undetermined source (Poorly demarcated speckled hyperfluorescence 5-10 minutes post-injection). Type 2 'classic' CNV: Sub-retinal; OCT: subretinal hyper-reflective material (SHRM) with SRF and/or IRF; FFA: Early lacy pattern of hyper-fluorescence with clear well-demarcated margins in the early phases, followed by mid and late phase of leakage and pooling. Type 3 CNV: Retinal angiomatosis proliferans (RAP). Intraretinal in location with localised intraretinal haemorrhage on examination. Typically extrafoveally due to FAZ in fovea. Distinctive shunt vasculature originating from outer retina potentially communicating with deeper choroidal neovascularisation. Stage 1: intraretinal neovascularisation, stage 2: subretinal neovascularisation, stage 3: chorioretinal anastamosis. OCT: serous or fibrovascular PED with overlying CMO. FFA: Similar to classic CNV but exact appearance may vary depending on its stage of evolution.
statements regarding FFA
Although this question is more likely to appear in FRCOphth Part 1 examination, a similar question has appeared in a past FRCOphth Part 2 written examination.
Indocyanine green has a stronger affinity to protein than fluorescein. Fluorescein is 70-85% bound to plasma albumin while ICG is 98% bound to serum proteins.
Because fluorescein has a wavelength of 520-530nm, it is blocked by RPE which means it is useless in assessing choroidal circulation except for the choriocapillaries during the first 40-60 seconds.
Fluorescein reaches the choroidal circulation first, giving the choroidal flush/hyperfluorescence during the choroidal phase. If a cilioretinal artery is present, this is when it will fill. In conditions such as ocular ischaemic syndrome there may be a delayed choroidal filling time.
Which of these is a test binocular status?
Worth four dot test or Bagolini glasses.
Binocular vision can be graded as:
Simultaneous perception Fusion Stereopsis (able to perceive "three-dimension").
Tests that can be used to assess binocular vision:
Worth four dot test or Bagolini glasses: Assesses simultaneous perception and fusion Prisms to assess range of motor fusion A range of three-dimensional tests to measure stereoacuity - Titmus, TNO, Lang, Frisby Synoptophore
The Maddox rod test is a subjective test that measures heterophorias and heterotropias at near and far fixation distances. A single Maddox rod can be used to measure horizontal, vertical and two Maddox rods can be used to measure torsional deviations (double maddox rod test).
Maddox wing is an instrument that can be used at near to measure size of deviation in strabismus, generally heterophorias, small heterotropias (with normal retinal correspondence) and torsion.
The four prism dioptre base out test is used to detect small central suppression scotoma or foveal suppression.
best characterises ultrasound findings of choroidal melanoma?
low internal reflectivity, echolucent
Choroidal melanoma typically appears to have low internal reflectivity with a high initial spike on A scan and is echo-lucent on B-scan.This is because the tumour cells are relatively homogenous and packed densely so there is minimal reflective surfaces. It is also usually collar or stud shaped due to the breach of Bruch’s membrane.
Choroidal metastases on the other hand tend to have higher reflectivity on A-scan and appear echo-dense on B-scan.
Choroidal haemangioma tends to have high internal reflectivity thanks to the blood in the tumour, increasing the number of reflective surfaces. It is usually dome shape.
In choroidal haemorrhage or effusion there are peripheral, dome shaped interfaces. In choroidal effusion, contents are echo-lucent whilst in choroidal haemorrhage the contents are echo-dense.
regard to MRI imaging i
When describing MRI findings, words that refer to signal intensity is usually used. The descriptors commonly used are “hypointense”, “isointense” and “hyperintense”. When a structure is dark, we describe it as “hypointense”. WHen it is similar to a reference structure, it can be described as “isointense”. If an abnormality is brighter than a reference structure, it can be described as “hyperintense”.
can cause a low ESR?
Polycythaemia, where there is an increase in red cell mass is a cause of low ESR. Other causes of low ESR include:
Congestive heart failure Sickle cell anaemia Leukocytosis Cryoglobulinaemia
The other options given are causes of high ESR.
High ESR can occur from any conditions causing inflammation such as rheumatoid arthritis and other autoimmune conditions. Pregnancy causes an elevated ESR.
A 65 year old woman presents with a 2 month history of intermittent double vision worse towards the end of the day. On examination her ocular motility is variable, there is orbicularis oculi weakness and there is fatigue on prolonged upgaze. Which of the following test will likely help with the diagnosis?
This patient has features most consistent with myasthenia gravis (MG). MG should be considered a possibility when there is intermittent diplopia. Methods for investigating for MG include:
ice-pack test serum antibodies - anti-acetylcholine (anti-ACh) receptor antibody present in >95% of patients with generalised myasthenia but only 50% of ocular myasthenia; anti-skeletal muscle is present in 85% of patients with thymoma single fibre electromyography (EMG)
As MG is associated with other autoimmune diseases, e.g. Graves’s disease in 4–10%, thyroid function test may help to detect associated thyroid disease but will not diagnose MG.
Skeletal muscle biopsy assessing for mitochondrial myopathic changes is used to diagnose chronic progressive external ophthalmoplegia (CPEO). Whilst double vision can possibly occur, most CPEO patients do not have double vision due to the symmetric and diffuse nature of the weakness of extraocular muscles.
Subsequent to placing 4 PD base-out prism over a child’s left eye, there is abduction of the right eye and no further movement. There is no movement when the same 4 PD base-out prism is placed over his right eye. Which of the following is correct?
The four prism dioptre base out test is used to detect small central suppression scotoma or foveal suppression. This is also called monofixation syndrome.
When the four prism dioptre prism is placed base out in front of left eye, there should be:
Dextroversion of the left eye. Why? Because rays are deviated towards the base of the prism so the left eye moves to the right re-fixate on fovea. This indicates absence of foveal suppression of the left eye.
Initial dextroversion of the right eye. This is due to Hering’s law.
Subsequent refixation of the right eye to the left to avoid double vision. This indicates absence of foveal suppression of the right eye.
Here, when the prism is placed in front of the left eye, the right eye abducted (dextroversion) due to Hering’s law but there is no re-fixation. This indicates foveal suppression of the right eye.
When the prism is placed in front of the right eye, there is no movement, which confirms that there is likely foveal suppression of the right eye.
Which of the following is the first choice of investigation to diagnose suspected PCV?
ICG
Polypoidal choroidal vasculopathy (PCV) is now thought to be a variant of wet AMD. It is characterised by polypoidal dilatation of the choroidal vasculature with serosanguineous PEDs. Classically described as a condition in African or Asian descent, but it it can occur in Caucasians.
Although FFA is useful in the workup in suspected CNV, ICG should also be performed where there is a suspicion of PCV. Early ICG hyperfluorescence (<5min) from subretinal fluid is one of the diagnostic criteria for PCV in the EVEREST study.
A 60 year old female has a painless unilateral swollen disc and is found to have an inferior altitudinal field defect. What is likely the most appropriate initial investigation?
The question stem suggests a possibility of a diagnosis of non-arteritic anterior ischaemic optic neuropathy however it is GCA until proven otherwise. GCA would first need to be ruled out. In addition to ESR, CRP and FBC should also be performed. Raised levels of ESR, CRP and platelets are supportive of GCA.
High-resolution MR imaging with IV contrast of the superficial cranial and extracranial arteries can be used to investigate GCA but should not be an initial investigation ordered. An MRI could show increased vessel wall thickness and oedema, increased mural enhancement post-contrast and luminal stenosis.
An FFA is not commonly used to investigate GCA these days, but if performed soon after vision loss, it may show delayed choroidal filling.
A B-scan for swollen discs can help with looking for disc drusen, vitreopapillary traction and in cases of papilloedema, distended optic nerve sheath but is unlikely to yield much useful results in this scenario.
Which investigation is likely to be most useful in cases of hemifacial spasm?
mri brain + orbit
Hemifacial spasms can either be primary or secondary. It is characterised by unilateral involuntary spasms of the facial musculature. Primary hemifacial spasm is when there is compression of the facial nerve when it exits from the brainstem. The most common mechanism is said to be compression from dolichoectasia of an artery, and the artery that is most commonly implicated is the anterior inferior cerebellar artery (AICA). Other arteries that can be implicated are posterior inferior cerebellar artery (PICA) and vertebral artery.
Secondary causes of hemifacial spasms include atherosclerosis, aneurysms, arteriovenous malformations, peripheral facial nerve trauma, parotid gland tumours and cerebellopontine angle tumours, brainstem strokes, demyelinating lesions and Bell’s palsy.
The main aim of a scan for hemifacial spasm would be to identify if there is a point at which the facial nerve is being compressed by a vascular structure. The combination of high-resolution 3D T2-weighted imaging with 3D time-of-flight angiography and 3D T1-weighted gadolinium-enhanced sequences is said to be the standard for investigation for any neurovascular conflict.
Out of the options, an MRI orbit and brain would capture the posterior fossa which is important, and captures the entire course of the facial nerve. The MRI of the internal acoustic meatus would miss a proportion of the facial nerve’s trajectory.
Frisby stereotest
The Frisby test is a test of stereoacuity. The test presents real objects, therefore a test of natural vision. There are three transparent plates of different thicknesses presented to the patient one at a time, and each have different sizes of disparity cues to measure the level of stereoacuity.
Each plate has four squares with a random pattern. Within each square, there is a circle of pattern elements lying in depth relative to its surround. This is achieved by the circle and its surround printed on opposite sides of the plate.
No special glasses are required.
The plate should be held a few centimetres above the clear background provided by the fold-down flap of the storage box to avoid introducing monocular cues. However one can deliberately introduce monocular parallax cues when checking test understanding prior to testing. This is done by resting the plate on a corner about 5cm from a clear background then twisting it to & fro with slow rotary movements. Understanding of the patient is confirmed when the patient sees the circle.
The Frisby stereotest can be used to test for stereopsis, even if reduced vision or amblyopia is present due of the coarse texture elements included in the pattern.
Which of the following causes a dark choroid on FFA?
Argyrosis is rare cutaneous discoloration caused by silver.
Ocular involvement, including corneal and conjunctival discoloration, have been previously reported. Choroidal blockage with a dark choroid on FFA have been observed for cases of argyrosis.
Which of the following is true regarding the equipment in the picture above?
This is a picture of a Maddox wing. It is used to measure:
heterophorias (latent deviation) small heterotropias (manifest deviation) when normal retinal correspondence is present
It can only be performed at near and cannot be used when there is abnormal retinal correspondence or suppression. It cannot distinguish between latent and manifest deviation.
It can measure horizontal and vertical deviation, as well as any torsional deviations which is one of its advantages.
In a Worth 4 dot test the patient sees 3 green lights, what does this mean?
RE supression
The Worth Four Dot test or Worth Four Light test assesses binocular vision and can test for diplopia, suppression and anomalous retinal correspondence (ARC). The test is normally carried out with refractive correction and at 33cm or 6m. The red lens usually covers the right eye, green covers the left eye. A light or wall-mounted target is shone towards the patient showing 4 dots in a diamond configuration. The patient is asked what they see.
cause a raised erythrocyte sedimentation rate (ESR)?
Conditions which raise ESR:
Infection
Pregnancy
Inflammatory disorders
Conditions which reduce ESR
Sickle cell
Polycythaemia vera
Leukocytosis
Low plasma protein
Corticosteroid use
Hereditary spherocytosis
A similar question has appeared in a past FRCOphth Part 2 examination.
This is a RAF near point rule (RNPR), also known as Royal Air Force (RAF). It is a tool used to measure:
Near point of convergence (NPC)
Near point of accommodation (NPA)
Provide therapeutic orthoptic exercises
The RAF rule has a number of scales:
A centimeter scale (2cm increments)
A equivalent dioptric power scale
Expected age scale
Convergence scale: a scale indicating positions of normal and abnormal convergence
We will not be going into detail on how the RAF rule is used here. But a few points to note:
The centimeter and convergence scales are used to assess NPC
The centimeter, dioptric power and age scale are used to assess NPA (not NPC)
Both objective and subjective NPC is assessed. The objective break point (when examiner notices one eye diverges) and subjective break point (patient reporting single target) are measured.
Measurement of NPA is done with full refractive correction, initially on each eye separately, subsequently both eyes simultaneously
A suspected subdural haematoma is best assessed using CT head first as it can be done quicker. An MRI can be done later on to assess the size and its effect on brain tissue once the patient is stabilised.
Wrong answers:
A titanium orbital implant is MRI safe.
MS is best assessed using MRI
T-1 weighted without gadolinium may show dark areas (hypointensities) thought to indicate areas of permanent nerve damage
T-1 weighted with gadolinium may show bright areas (enhancing lesions) that indicate areas of active inflammation
T-2 weighted shows overall disease burden (old) or lesion load (new)
Fluid attenuated inversion recovery (FLAIR) shows MS activity by reducing interference from the spinal fluid
Suspected brain tumour is best visualised using MRI rather than CT.
Which of the following will most likely appear black on a T2 weighted MRI?
MRI STIR is best for assessing muscle swelling. CT head is most useful to assess body structures during planning of orbital surgery.
Extras
Intensity: T1: Fat > white matter > gray matter > CSF T2: CSF > gray matter > white matter > fat FLAIR: Fat> gray matter > white matter > CSF STIR: CSF = gray matter > white matter > fat
Which of the following is most likely to cause a binasal visual field constriction?
Vigabitrin is an irreversible GABA transaminase inhibitor that can cause a concentric peripheral field loss with temporal and macular sparing.
Chlorpromazine may cause corneal crystal deposition, and pigmentation of eyelids and conjunctiva.
Isoniazid may cause optic neuropathy.
Which of the following will most likely appear black on T1 weighted MRI?
CSF
MRI STIR is best for assessing muscle swelling. CT head is most useful to assess body structures during planning of orbital surgery.
Extras
Intensity:
T1: Fat > white matter > gray matter > CSF
T2: CSF > gray matter > white matter > fat
FLAIR: Fat> gray matter > white matter > CSF
STIR: CSF = gray matter > white matter > fat
investigation for a patient with chronic progressive external ophthalmoplegia (CPEO)?
Echocardiogram
An ECHO is appropriate to rule out cardiac pathology seen in Kearns-Sayre syndrome, a variant of CPEO.
Chronic progressive external ophthalmoplegia (CPEO)
Mitochondrial DNA mutation (maternally inherited) Bilateral ptosis, reduced smooth pursuits/saccades/reflex eye movements Weakness of orbicularis oculi and facial muscles
Variants
Kearns-Sayre syndrome: CPEO, pigmentary retinopathy, heart block MELAS syndrome: mitochondrial encephalopathy, lactic acidosis, stroke-like, hemianopia, cortical blindness
Investigations
ECG
Consider skeletal muscle biopsy
Ragged red fibres with peripheral concentration of mitochondria
Bloods
MRI
Treatment
Neurology consult Geneticist Cardiologist Ptosis repair
cause of an elevated angiotensin converting enzyme level?
Hypothyroidism can cause a lower than normal angiotensin-converting enzyme (ACE) level.
ACE plays a role in regulation of blood pressure, catalysing the conversion of Angiotensin I to Angiotensin II and inactivates bradykinin.
ACE level testing is mainly used for monitoring of patients diagnosed with sarcoidosis as there can be increased production of ACE by sarcoidal granulomas. However it lacks sensitivity and specificity, so should not be used as a diagnostic test for sarcoidosis. It is also influenced by ACE gene polymorphisms.
Higher than normal ACE levels can signify sarcoidosis, but may also be seen in other disorders:
Diabetes Alcoholic liver disease Hyperthyroidism Myocardial infarction
Higher than normal ACE levels may also be a normal variant.
Lower than normal ACE levels can be seen in:
Hypothyroidism Multiple myeloma Lung cancer Lymphoma
Note that various sources may quote that the same condition causes both higher and lower than normal levels but we have found references reporting the above.
Reference(s):
NHS South Tees Hospital NHS Foundation Trust. Angiotensin converting enzyme (ACE). Retrieved 5 January 2024, from https://www.southtees.nhs.uk/services/pathology/tests/angiotensin-converting-enzyme-ace/ Borowsky SA, Lieberman J, Strome S, Sastre A. Elevation of Serum Angiotensin-Converting Enzyme Level: Occurrence in Alcoholic Liver Disease. Archives of Internal Medicine 1982; 142(5): 893-895. Smallridge RC, Rogers J, Verma PS. Serum angiotensin-converting enzyme. Alterations in hyperthyroidism, hypothyroidism, and subacute thyroiditis. Jama 1983; 250(18): 2489-2493.
re Hess charts
Hess charts requires normal retinal correspondence and central fixation.
Eyes are dissociated by either complementary colours (Hess chart) or mirror (Lees screen).
Hess charts is not useful in all cases of strabismus, only in incomitant ones.
