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.
In which condition are corneal deposits separated from each other by cloudy cornea?
Macular dystrophy is characterised by:
autosomal recessive inheritance
defect in the synthesis of keratan sulfate
mucopolysaccharide deposits accumulate throughout the cornea
cloudy intervening cornea
periphery of cornea is involved
severe reduction of vision
deposits stain with colloidal iron and alcian blue
The parents of a child with unilateral retinoblastoma would like to know the probability of having another child with retinoblastoma. Both parents are healthy.
What would you advise?
If a patient has unilateral retinoblastoma and the parents are healthy, the risk of the parents having another child with retinoblastoma is 1%. The risk of the patient having a child with retinoblastoma is 8%.
A patient presents with progressive reduction of visual acuity over 6 months. There is photosensitivity and nyctalopia. Fundus examination shows attenuated arterioles, optic disc pallor and mild RPE changes. There is no inflammation. The ERG is severely attenuated under photopic and scotopic conditions.
What is the most likely underlying cause for this presentation?
The presentation is most in keeping with cancer-associated retinopathy. CAR is most commonly associated with small cell lung cancer, followed by gynaecological and breast cancer.
Examples of conditions with defects in mitochondrial DNA
Leber’s hereditary optic neuropathy
Kearn-Sayer’s syndrome
Leigh disease
Which IL does cyclosporin inhibit?
IL2
Causes of choroidal folds
idiopathic
orbital disease: e.g. retrobulbar tumours and TED
choroidal tumours
posterior scleritis
chronic papilloedema
scleral buckling
A 14-year-old girl is struggling to read homework and complains of poor central vision. Her acuities are 6/24 bilaterally. The first year ophthalmology trainee reports no abnormalities on dilated fundus examination.
What is the most likely diagnosis?
The age of presentation and normal fundus appearance suggest Stargardt’s disease.
Features of Stargardt’s disease?
most common inherited macular dystrophy
autosomal recessive
presents in first 2 decades
bilateral reduced vision
fundus may appear normal
early: mottling of RPE; pisciform flecks at the level of the RPE at the posterior pole
later: aggregation of flecks to form an atrophic patch and bull’s eye appearance
FFA: dark or ‘silent choroid’ due to blockage of the background choroidal fluorescence by deposition of lipofuscin
visual prognosis is generally poor with vision stablising to 6/60
Following unsuccessful probing of a congenitally impatent nasolacrimal system in a 13-month-old girl, the next therapeutic step would be:
If probing of a congenitally impatent nasolacrimal system is unsuccessful, silicone tube intubation should be considered and is effective in 85% of the cases.
When should DCR be delayed until (age wise)?
DCR should be delayed until 3 years of age for long-standing success.
Which visual phenomenon is most likely to accompany see-saw nystagmus?
See-saw nystagmus is a feature of chiasmal syndrome; which can also cause post-fixation blindness. Formed visual hallucinations are caused by temporal lobe lesions, while unformed hallucinations are caused by lesions of the occipital lobe.
A 23-year-old man who underwent LASIK surgery 6-months ago for myopia suffers blunt ocular trauma with a football. On examination, there is a dislocated right corneal flap with rolled edges.
What is the most appropriate treatment?
Prompt diagnosis and surgical treatment by flap repositioning under the slit lamp or surgical microscope (typically without sutures) usually restores anatomical integrity and visual acuity
A patient presents with right esotropia. To estimate the deviation, the examiner chooses to use the Krimsky method.
To do this most reliably he should:
The Krimsky test is essentially the Hirschberg test, but with prisms to quantify the deviation. Prisms can be placed over one or both eyes. However, since observation of the corneal light reflex through a prism may be difficult, it is recommended to place the prism over the fixating eye until the corneal light reflex from the non-fixing eye appears central.
A patient with retinitis pigmentosa is found to have acanthocytosis on her blood film. This finding is most consistent with:
Bassen-Kornzweig syndrome is caused by a deficiency in beta-lipoprotein resulting from intestinal malabsorption. Inheritence is AR, with signs including:
pigmentary retinopathy
spinocerebellar ataxia
ptosis
CPEO
The blood film shows acanthocytosis. Treatment is with vitamin E
What are some causes of a shallow anterior chamber with high IOP post-trabeculectomy
Pupillary block: this is due to a non-patent peripheral iridotomy with iris bombe. The bleb is flat and Siedl’s is negative
Aqueous misdirection: this is due to aqueous being directed posteriorly into the vitreous. The AC is shallow, the IOP high, the bleb flat and Seidel negative. However, the iridotomy in this case is patent with no iris bombe.
A shallow anterior chamber with low IOP post-trabeculectomy can be the result of:
Scleral flap leak: the bleb is well formed and Seidel test negative
Conjunctival bleb leak: the bleb is flat and Seidel test positive
Astrocytic hamartomas of the retina or optic nerve head may be seen in:
Astrocytic hamartomas can be associated with tuberous sclerosis or neurofibromatosis, or they can be sporadic. They are located in the nerve fiber layer of the retina or occasionally the optic disc.
A patient has a 75% full thickness defect of the left lower lid following Moh’s excision of a BCC. Which surgical method would be the most appropriate for reconstruction?
Hughes bridge flap
