Key Points 4 Flashcards
What are the characteristics of the image formed by a prism?
is always deviated towards the apex
In order to truly isolate cone function, it is necessary to present a light stimulus as a flicker-flash at what minimum frequency?
Rods can respond to flickering stimuli with rates up to 20 Hz. Only cones can respond at higher frequencies, with a maximum of approximately 70 Hz.
What were the outcomes of the CIGTS study?
the trabeculectomy group had more visual field and visual acuity loss compared to the medically treated group over the first 3 years, however by years 4 and 5 these differences were not statistically significant
Where is the standard reference plane taken in Heidelberg retinal topography (HRT) of the optic disc?
50 um below the optic nerve head boundary line at the temporal disc edge along the horizontal midline
This location is taken as the standard default reference plane because it corresponds to the centre of the papillomacular bundle of the RNFL. This papillomacular bundle is usually preserved until late in glaucoma, so it would be expected to have a stable thickness over time.
A 35-year-old man presents with severe hypertension and is found to have a unilateral phaeochromocytoma. His father died from metastatic renal-cell carcinoma aged 48 and previously had surgery for a brain tumour.
What is the most likely underlying genetic condition?
Von Hippel-Lindau
Chronic asymptomatic dacryocystitis is most frequently caused by:
Clinically silent dacryocystitis is usually produced by Streptococcus pneumoniae and may present with no clinical symptoms other then occasional epiphora.
What are some causes of bilateral neonatal corneal clouding
mucopolysaccharidoses
congenital hereditary stromal dystrophy
congenital hereditary endothelial dystrophy
What are some causes of unilateral neonatal corneal clouding
corneal dermoids
What is the triad of spasmus nutans?
monocular or dissociated small-amplitude nystagmus
head bobbing
torticollis
Differential diagnoses for spasmus nutans?
chiasmatic gliomas
subacute necrotising encephalomyopathy
A patient has frontal bossing, hearing impairment, optic atrophy and angioid streaks.What is the most likely diagnosis?
Paget’s disease involves excessive and disorganized resorption and formation of bone. Features include: bowing of the tibias, obstruction of cranial foramina (leading to deafness, optic atrophy, ocular motility defects, cranial nerve palsies etc) and bony deformity especially of the skull. It is a known cause of angioid streaks. Treatment is with bisphosphonates.
What is dissociated vertical deviation
simulates a hyperphoria but violates Hering’s law. When covered, the left eye drifts up. When uncovered, the left eye moves down to assume fixation. By Hering’s law, the yoke muscles of the right eye, depressors, should receive equal innervation as the left eye moves down. The right eye should be deviated downward under cover and move up to reassume fixation when the cover is shifted back to the left eye. The dissociation of DVD refers to the violation of Hering’s law with dissociation of yoke muscles.
Which organ system is most likely to develop toxicity from the polyene class of antifungal agents?
Polyenes include amphotericin B and natamycin. Polyenes can cause renal toxicity.
Features of RD vs Retinoschisis
RD
Myope
Superotemporal
Relative scotoma
Present pigment
Corrugated surface
Shifting fluid may be present
No reaction to PRP
Retinoschisis
Hypermetrope
Inferotemporal
Absolute scotoma
Absent pigment
Smooth surface
Absent shifting fluid
Reaction to PRP
Causes of Bull’s eye maculopathy:
cone dystrophy
cone-rod dystrophy
chloroquine or hydroxychloroquine toxicity
ceroid lipofuscinosis
Stargardt’s and fundus flavimaculatus
fenestrated sheen macular dystrophy
parafoveal atrophy of RPE secondary to AMD
central areolar choroidal dystrophy
benign concentric annular macular dystrophy
Juvenile Batten’s disease
fucosidosis
clofazimine maculopathy
Treatment for convergence insufficiency
treated with orthoptic convergence training exercises, for example base out prism therapy and pencil push-up exercises to build up convergence amplitudes. Very few strabismologists, if any, advocate surgery for this problem.
Features of Cavernous Haemangioma
most common adult intra-conal lesion
large blood-filled spaces
not a true neoplasm (not from proliferating clonal cells)
typically middle-age, women
proptosis (usually axial)
reduced vision, diplopia, lid swelling, palpable mass
usually intra-conal (rarely involves orbital apex)
does NOT enlarge with Valsalva (differentiating from varices, AVM, lymphangioma and capillary haemangioma)
pleboliths may be present (these also occur in other slow moving venous malformations such as varices)
imaging: lesions round, homogenous, encapsulated, not involving apex
MRI: hypo-intense on T1, hyperintense on T2 (not unique)
differential: rhabdomyosarcoma, meningioma, neurofibroma, neurilemmoma, haemangiopericytoma (malignant)
treatment: nil if asymptomatic, surgery (lateral orbitotomy) for excision
Where does the cavernous sinus receives blood from
superficial middle cerebral vein
superior ophthalmic veins
inferior ophthalmic veins
sphenoparietal sinus
Advantages of iridotomy created with Argon vs ndYAG laser
require more applications
greater energy
more extensive early oedema and tissue destruction at the margins
more iritis
more pupillary distortion
higher incidence of late closure of the iridotomy
What is Shaken Baby Syndrome
may be associated with retinal haemorrhages and cotton wool spots, which can appear similar to conditions such as central retinal vein occlusion, Purtsher’s retinopathy and Valsalva retinopathy.
The appearance of macroaneurysm with a single focal haemorrhage along a major arterial arcade and surrounding circinate exudation is quite distinct from Shaken baby syndrome.
What are signs of vertebral-basilar insufficiency and what tests would you request?
sudden-onset vomiting, dizziness, and double vision. On examination, she has a concomitant left hypertropia and ataxia.
Cerebral MRI and MRA would be the best tests because the brainstem, cerebellum, and arteries (vertebral, basilar) could be evaluated.
What are the measurments used in the Hirschberg corneal reflection test?
1 mm displacement = approximately 7 degrees = 15 PD
Reflex displaced to:
pupil edge = 2 mm = 15 degrees = 30 PD
midway from pupil to limbus = 4mm = 30 degrees = 60PD
limbus = 6mm = 45 degrees = 90PD
The knee of von Willebrand comprises which contralateral retinal fibers?
infero-nasal retinal fibers that cross in the optic chiasm and course anteriorly into the contralateral optic nerve before running posteriorly
Which best describes the Rizzuti sign:
The Rizzuti sign is a sharply focused conical reflection of light on the nasal cornea from a temporal light source and is seen in keratoconus. It is produced by total internal reflection from the advanced cone.