Key points 18 Flashcards
Which treatment modality is the most controversial in the management of keratoconus:
Photorefractive keratectomy (PRK) with the excimer laser has been used by some groups to treat patients with keratoconus to help reduce corneal surface irregularities and improve vision. However, it remains a relatively contraindicated (and therefore controversial) treatment because laser ablation with PRK can further weaken the cornea, which is already thinned in keratoconus, thus potentially leading to progression of the disease
A 28-year-old highly myopic woman presents with a macular-on inferior retinal detachment encroaching on the inferior arcade. There is no Weiss ring detected. A retinal tear is noted inferiorly.
What is the most appropriate management?
Scleral buckling is preferred for young phakic patients without PVD. The disadvantage of vitrectomy in this setting is the inevitable formation of a cataract and subsequent loss of accommodation when this is removed. There is also a risk with vitrectomy of inducing further tears when the PVD is induced surgically; and the inescapable risks of intra-operative surgery such as endophthalmitis, which is not present in an external procedure such as buckling.
What are the complications of scleral buckling?
explant infection
explant extrusion
strabismus
refractive error
anterior segment ischaemia
angle closure glaucoma
When is the patch test done to differentiate pseudo divergence excess from true divergence excess?
difference of greater than 10 PD between near and distance.
Where is the osteotomy site during DCR?
level of the middle turbinate. The site is most often within 10 mm of the cribriform plate.
Which immunoglobulin has NOT been detected in tear samples?
All major immunoglobulin classes except IgD have been detected in human tears. IgA (secretory immunoglobulin) is the primary immunoglobulin in tears.
The Endophthalmitis Vitrectomy Study (EVS) reported which one of the following findings regarding intravenous antibiotics?
The EVS study clearly demonstrated that neither amikacin nor ceftazidime offered any therapeutic advantage in acute post-cataract bacterial endophthalmitis
Hutchison’s triad refers to which signs?
interstitial keratitis
notched teeth (shown in image above)
sensorineural deafness
An asymptomatic patient presents via their opticans, who have detected a pale, yellow-white area of the fundus adjacent to the optic disc. On ultrasound imaging, there is an area of thickening corresponding to the pale area of the fundus, with high surface reflectivity and complete loss of signal behind the lesion.
What is the most likely diagnosis?
A choroidal osteoma is characterised by:
benign ossifying tumour
mature bone replacing choroid
often para-papillary
yellow-white or orange-red fundus colouration
overlying RPE degeneration
well-defined margins
high surface reflectivity on ultrasoud with acoustic shadowing (pseudo-optic nerve)
How long are the different segments of the optic nerve?
intraocular: 1mm
intraorbital: 30mm
intracanalicular: 6mm
intracranial: 10mm
According to the Royal College of Ophthalmologists screening guidelines, a patient on vigabatrin should have:
baseline VF with perimetry extending to at least 45 degrees (static suprathreshold or kinetic)
6 monthly visual fields as above for 5 years followed by annual screening
What is the approximate prevalence of glaucoma in the population over the age of 40?
between 1-2% of the adult population over 40 years.
Which features helps to differentiate congenital hereditary endothelial dystrophy from congenital hereditary stromal dystrophy:
In congenital hereditary stromal dystrophy, the cloudy stroma is of normal thickness, and the epithelium is normal. In congenital heriditary endothelial dystrophy (CHED), there is epithelial oedema and a thickened stroma. In both conditions, IOP is usually normal.
As a diagnostic test polymerase chain reaction suffers MOST from which limitation:
PCR is fast, fully automated and highly reproducible. However, because it amplifies DNA material to such a scale, it suffers from high false-positives due to contamination.
What did the CIGTS study assess?
compared the effects of medical treatment to early filtration surgery in newly diagnosed open angle glaucoma.
What were the CIGTS study findings?
IOP was significantly decreased in both the medically and surgically treated groups, with the surgery group having a larger decrease. However, in the surgery group, the need for subsequent cataract surgery was significantly higher, and patients were more likely to lose visual acuity and visual field during the first few years of follow-up. After 4 years, patients in both groups were similar in visual acuity and visual field. Patient’s health-related quality of life questionaires were comparable in both treatment arms.
Indications for the removal of an orbital meningioma include
severe loss of vision
rapid tumour growth (especially in a child)
intracranial extension
A 35-year-old man presents with a 2-day history of blurred left vision. Examination reveals haemorrhagic changes emanating from the left optic disc with exudation towards the macula. There is peripapillary atrophy and pigmentary change. An FFA confirms juxtapapillary choroidal neovascularisation.
Where might this patient have lived?
The presentation is most in keeping with presumed ocular histoplasmosis syndrome (POHS), which is most prevalent in the Ohio-Mississippi river valley.
Astrocytic hamartomas are MOST likely to feature in which phakomatosis:
Retinal astrocytic hamartomas may be encountered in both von Ricklinghausen disease and Bourneville’s syndrome (tuberous sclerosis).
What is the rate of blebitis in trabeculectomy with antimetabolite augmentation?
The rate of blebitis following trabeculectomy with anti-metabolite augmentation is approximately 5%. The rate of endophthalmitis is less than 1%.
Which of the retrochiasmal locations can induce a monocular visual field defect?
The only retro-chiasmal lesion of the visual pathway to produce a monocular field defect is a lesion of the anterior visual cortex in the occipital lobe.
What is the best treatment option for a localized orbital lymphoproliferative lesion?
Surgical excision is not recommended, and neither are systemic corticosteroids. Radiation is the treatment of choice for these lesions.
What are features of De Morsier’s syndrome?
optic nerve hyoplasia
pituitary gland dysfunction
absence of the septum pellucidum
which laser is best for retinal photocoagulation in the setting of dense cataract or vitreous haemorrhage?
Red light penetrates cataract and vitreous hemorrhage better than lights of other wavelengths. KRYPTON RED
A patient with Stickler’s syndrome is most likely to develop which pre-senile cataract:
Hereditary fundus dystrophies such as RP, Leber’s congenital amaurosis, gyrate atrophy and Sickler’s syndrome may be associated with posterior subcapsular lens opacities.
Angiographically silent choroid can be seen in:
A silent or dark choroid on fluorescein angiography is typical of Stargardt’s disease, due to the accumulation of lipofuscin which blocks the underlying choroidal fluorescence. A dark choroid may also occur in patients with systemic argyrosis who are receiving systemic silver.
What is the minimal residual corneal stromal bed thickness that is considered safe for LASIK refractive surgery?
250 um thickness of the residual corneal stromal bed is the benchmark used for safe LASIK surgery, though this remains an area of contention.
