Glaucoma Flashcards
How many axons are present in a typical opic?
1 to 1.2 million axons.
What is the best method for examining for the opitc nerve?
A slit lamp examination with a posterior pole lens gives the best magnification and stereoscopic view.
Name the two cell types found within the ganglion cell layer?
M cells (magnocellular) have large diameter axons, synapse in the magnocellular layer of the lateral geniculate body, and are sensitive to changes in dim illumination. P cells (parvocellular) comprise the majority of the ganglion cells, have small diameter axons, synapse in the parvocellular layers of the lateral geniculate body, and are used in color and fine detail.
Name the four layers of the optic nerve and their respective vascular supply.
Nerve fiber layer- Central retinal artery. Prelaminar layer- short posterior ciliary arteries. Laminar layer- short posterior ciliary arteries. Retrolaminar layer- branches of the meningeal arteries and central retinal artery.
How do the short posterior ciliary arteries in the optic nerve differ from those of the choriocapillaris?
The short posterior ciliary arteries in the optic nerve resemble retinal capillaries. They are surrounded by pericytes, have tight junctions, and lack fenestrations.
Why does glaucomatous cupping occur earlier in children than in adults?
The scleral ring surrounding the optic nerve expands with increased IOP in children and infants.
What supplies essential nutrients and removes waste from the lens, cornea, and trabecular meshwork.
The aqueous humor acts as a substitute blood for these avascular tissues.
What percentage of plasma proteins is filtered out by the blood-aqueous barrier in the formation of aqueous humor?
More than 99% of plasma proteins are absent from aqueous. Normal aqueous has a protein content of about 0.02g/100ml, while plasma contains about 7g/100ml.
How far away is the optic nerve head from fixation in the visual field?
10-15°
What retinal layer is most damaged by glaucoma?
Nerve fiber layer.
Patient’s with which type of glaucoma are most likely to have splinter hemorrhages of the optic disc?
Normal-tension glaucoma
What photographic technique best demonstrates early nerve fiber layer thinning?
High contrast black-and-white photography.
What is the initial medical management for ciliary-block (malignant) glaucoma?
Atropine and corticosteroids as well as aqueous suppressants to control IOP as needed.
How does the Schiotz tonometer work?
The IOP is determined by measuring the indention of the cornea by a known weight on a linear scale on the instrument. The value is then converted using a table to IOP in mmHg.
When should digital palpation be used to measure IOP and how accurate is it?
IOP estimation by digital palpation should be reserved fro uncooperative patients only, because its only useful in detecting large differences in IOP between two eyes.
Why is it important to clean tonometers between uses?
Many viruses, including those causing AIDS, EKC, and hepatitis, can be recovered from the tears of infected individuals.
What type of inheritance pattern is seen in juvenile-onset glaucoma?
Juvenile-onset glaucoma has been shown to follow an autosomal dominant inheritance pattern by large pedigree studies, and a genetic marker has been identified on chromosome 1q.
What is the first assessment that should be made when evaluating an automated visual field?
Noting the percentage of fixation losses, false positives, false negatives, and fluctuations should first assess the quality of the test.
What is the average fluctuation seen between points on an automated visual field in normal and abnormal subjects?
The average fluctuation should be less than 2 dB in a normal field, less than 3 dB in cases of early damage, and less than 4 dB in cases of moderate damage.
How is adult-onset primary open angle glaucoma thought to be inherited?
It most closely follows an autosomal recessive pattern.
What is Sampaolesi’s line
Pigment deposited anterior to Schwaldbe’s line, which is seen in pseudoexfoliation syndrome and pigmentary dispersion syndrome.
What type of artifact will be produced if a patient quits responding midway through a Humphrey visual field test?
A cloverleaf-shaped field is a common artifact seen in automated visual field testing.
What effect is seen if a patient’s spectacle correction is not used during automated perimetry?
Generalized depression of visual sensitivity.
What effect does a media opacity, such as cataract, have on the results of automated perimetry?
Media opacities cause a generalized depression of the visual field with a normal pattern standard deviation. Miotic pupils can cause similar artifacts.
The goal of serial visual field testing is to detect progression of glaucomatous damage. What is mandatory for this type of interpretation?
An accurate baseline field.
What is the mechanism of action for the antimetabolites 5-fluorouracil and mitomycin C to increase the success rate of glaucoma filtering surgery?
Both of these medications inhibit the proliferation of fibroblasts and mitomycin C also affects the proliferation of vascular endothelial cells. 5-FU is a fluorinated pyrimidine inhibitor of thymidylate synthase and is an S-phase specific agent. Mitomycin C is a cell cycle nonspecific alkylating agent.
A diurnal fluctuation of greater than 10 mmHg suggests what diagnosis?
Glaucoma.
What antioxidant is found at levels 10 to 50 times higher in aqueous than plasma?
Ascorbic acid (Vitamin C)
What enzyme found in the aqueous provides essential antibacterial activity?
Lysozyme.
Low-tension glaucoma patients have been divided into what two groups by some authorities. What are they?
- The senile sclerotic group has a characteristic shallow, pale sloping of the optic nerve rim. 2. The focal ischemic group suffers deep, focal notching in the optic nerve rim.
How do the typical visual field defects of low-tension glaucoma patients differ from those of high-tension glaucoma patients?
They are usually more dense, focal, and closer to fixation.
Does low-tension glaucoma seem to have any race predilection?
Yes, it seems to have a higher prevalence among Japanese patients.
What test should be used clinically to rule out POAG before making a diagnosis of low-tension glaucoma?
Diurnal IOP measurement.
What in a patient’s medical history could explain the optic neuropathy and visual field loss that would otherwise be labeled normal-tension glaucoma?
History of hemorrhagic shock, myocardial infarction, anemia, syphilis, or vasculitis.
What growth modulatory factor shows increased levels in the aqueous when any ocular neovascularization is present?
Vascular endothelial growth factor (VEGF)
How do you perform the dark room prone test?
This test is done in patients with suspiciously narrow angles. IOP is first measured, and then the patient is seated for 30-60 minutes in a darkened room with the head down on a cushioned table. The IOP is again measured in the darkened room. A rise of 6-8 mm Hg or greater or a significant asymmetric rise in IOP accompanied by gonioscopic confirmation of furter angle closure is a positive test, and a laser iridotomy is performed. Placing the patient in a brightly-lit room for 5 minutes after this test and observing a significant lowering of IOP is further confirmation of a positive test.
Why do some glaucoma experts advocate the use of calcium channel blockers in low-tension glaucoma patients?
Calcium channel blockers may increase perfusion to the optic nerve.
What oral osmotic agent should be used to lower the IOP of a diabetic patient with an attack of acute angle closure glaucoma?
Isosorbide.
What neurological complication can result from use of osmotic agents such as mannitol and urea?
Brain shrinkage with traction on vessels and subsequent subarachnoid hemorrhage.
Which part of the ciliary body is responsible for active secretion of aqueous?
Nonpigmented ciliary epithelium.
What are the partial pressures of oxygen and carbon dioxide in the aqueous?
Oxygen: 55 mm Hg. Carbon dioxide: 40-60 mm Hg.
What is the normal pH of aqueous humor?
Normal range is 7.5-7.6.
What is the most prevalent type of adrenergic receptors in the ciliary epithelium?
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A patient presents for exam one day following a trabeculectomy. She is comfortable, the anterior chamber is shallow and the IOP is 2. The bleb is flat and no choroidals are present. What test will make the diagnosis apparent?
Seidel testing. This patient has the classic findings of a wound leak with a low IOP, shallow AC and a flattened filtering bleb.
What does the fibrillar material deposited in the anterior chamber of the eye in pseudoexfoliation syndrome resembles histochemically?
Amyloid.
Which is the only form of primary angle closure glaucoma that is not totally caused by a pupillary block mechanism?
Plateau iris.
Is there a difference in the success rate between limbus-based and fornix-based conjunctival flags?
No. A fornix-based flap is easier to dissect and close but there is an increased risk of leakage at the limbus, especially with the use of adjunctive antimetabolites.
What method is most commonly used to measure the rate of aqueous formation?
Fluorophotometry
What is the mean IOP of the population in general?
The mean IOP is approximately 16 mmHg and there is a standard deviation of 3 mmHg. The distribution is skewed toward the higher values, and this is more apparent in people over 40.
Why does the pattern of deposits on the anterior lens capsule in pseudoexfoliation syndrome resembles a target?
The iris rubs off the material during normal pupillary size changes, leaving a clear zone between areas of central and peripheral deposition.
Why is a relatively shallow anterior chamber a common finding in patients with pseudoexfoliation syndrome?
Forward movement of the lens-irs diaphragm sometimes occurs secondary to the zonular weakness tah accompanies the disorder.
What is the mechanism of action of latanoprost?
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Acutely, how would the IOP change with a 4 mmHg rise in episcleral venous pressure?
The IOP would also rise 4 mmHg. There is a 1:1 change in IOP with acute changes in episcleral venous pressure. This does not hold true for chronic conditions.
What is the approximate turnover time of aqueous humor?
About 1% of the aqueous is replaced every minute, so turnover time is approximately 100 minutes.
What happens to outflow facility as a person ages?
Outflow facility decreases as age increases.
What are two complications of cataract surgery seen frequently in patients with pseudoexfoliation syndrome?
Zonular dehiscence and vitreous loss.
What region of the world has the highest prevalence of pseudoexfoliation syndrome?
Pseudoexfoliation syndrome is responsible for up to 50% of open-angle glaucoma in Scandinavian countries.
When may releasable sutures be removed from a trabeculectomy?
Releasable sutures usually are pulled at any time between 1 and 21 days. This time may be extended with the use of adjunctive antimetabolite therapy and an effect may be seen up to one year postoperatively according to some reports.
What causes the iris transillumination defects seen in pigment dispersion syndrome?
It is thought that zonular contact with the iris pigment epithelium is responsible for the release of pigment.
What type of drug is brimonidine?
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How does alcohol use affect IOP?
Consumption of alcohol decreases IOP for a short time.
How does the risk of developing glaucoma change over time in an eye with angle recession?
The risk of developing glaucoma drops off substantially after a few years.
What is the treatment of choice for angle recession glaucoma?
Aqueous suppressants.
How many times more common is glaucoma among blacks as compared to whites?
The prevalence of glaucoma is 3 to 6 times higher in blacks than in whites.
In what way is glaucoma associated with cyclodialysis clefts?
An abrupt increase in IOP may occur as the cleft closes. When a cleft is open, hypotony is more likely because of increased uveoscleral outflow.
What type of eyes is associated with anatomically narrow angles?
Small, hyperopic eyes, e.g. nanophthalmos.
Why has some experts advocated laser peripheral iridotomy (LPI) for patients with pigmentary glaucoma?
To relieve the posterior bowing commonly seen in the peripheral iris of these patients and subsequently decrease contact between the iris pigment epithelium and zonules, LPI has been advocated by some, but its efficacy has not yet been established.
What physiologic mechanisms are responsible for aqueous humor production, and which mechanism produces most of the aqueous?
Diffusion, ultrafiltration, and active secretion produce aqueous. It is widely believed that most of the aqueous is produced by active secretion, which involvesa Na-K ATPase active transport pump.
Compare the concentrations of sodium, potassium, magnesium, calcium, and lactate in plasma and aqueous?
The concentration of sodium, potassium, and magnesium in aqueous is similar to plasma, while calcium is about half that found in plasma. Lactate concentrations in aqueous is higher than in plasma.
What happens to IOP as a patient lies down?
IOP is usually higher when lying down as compared to sitting upright.
How does phacolytic glaucoma occur?
It occurs when denatured lens proteins from a hypermature cataract leak through an intact lens capsule, causing an inflammatory reaction in the anterior chamber. Macrophages engorged with lens proteins, fill the anterior chamber and clog the trabecular meshwork, causing a rise in intraocular pressure.
What effect does cannabis have on IOP?
Cannabis use decreases IOP, although it has no established clinical use in this regard.
Does caffeine affect IOP?
Yes, caffeine sometimes causes a transient rise in IOP.
What is the difference between choroidal detachments and retinal detachments with regards to their anterior extent on B-scan ultrasonography?
Choroidal detachments can extend to the scleral spur, while retinal detachements end at the ora serrata.
What types of glaucoma are nanophthalmic eyes prone to?
Angle closure glaucoma.
What group of patients is at increased risk for developing glaucoma following a hyphema?
Patients with any of the sickle cell hemoglobinopathies are at increased risk because sickled red blood cells are more likely to clog the trabecular meshwork.
What medication should be avoided in sickle cell patients with a hyphema?
Carbonic anhydrase inhibitors are thought to increase sickling in the anterior chamber.
Name two conditions that can produce elevated episcleral venous pressure and dilated episcleral vessels.
Sturge-Weber syndrome and arteriovenous fistulas.
An infant with congenital glaucoma has cloudy corneas. What is the surgical treatment of choice?
Trabeculotomy, since this does not require a clear cornea to be performed.
What position must the patient be in when you perform Koeppe gonioscopy?
The patient must be supine.
When is Koeppe gonioscopy most commonly used?
During examination under anesthesia and when performing goniotomy.
What are the lenses changes following an attack of angle closure glaucoma called?
Glaukomflecken
What is the explanation for the increased risk of choroidal and exudative detachments when performing surgery on nanophthalmic eyes?
Nanophthalmic eyes are small with thick sclera, which impedes vortex vein drainage.
Describe the normal diurnal variation of IOP.
Over a 24-hour period, IOP varies 2-6 mmHg in the normal population.
What is the difference between a cyclodialysis and an angle recession?
A cyclodialysis is a separation of the ciliary body from the scleral spur, while an angle recession is a separation of the longitudinal and circular muscles of the ciliary body.
Two weeks after filtering surgery, a glaucoma patient presents with an IOP of 40 mmHg, a low lying bleb and a deep anterior chamber. What is the cause for the high pressure in this patient?
Gonioscopy will probably show blockage of the sclerostomy. YAG laser therapy may reopen it.
Which miotic agent has both indirect and direct cholinergic activity?
Carbachol, which is an acetylcholine analog and a competitive inhibitor for acetylcholinesterase.
What are the major risk factors for spikes in intraocular pressure after argon laser trabeculoplasty?
Posterior laser burns, dense trabecular pigment, and poor outflow facility.
What phacomatoses are associated with congenital glaucoma?
Sturge-Weber syndrome and neurofibromatosis type I (NF-1).
What angle structure is the peripheral termination of Descemet’s membrane?
Schwalbe’s line
What portion of the trabecular meshwork is adjacent to Schlemm’s canal?
The trabecular meshwork has three portions: uveal, corneoscleral, and juxtacanalicular. The juxtacanalicular meshwork lies adjacent to Schlemm’s canal.
A diabetic patient presents with acutely elevated IOP following a vitreous hemorrhage. She appears to have a small hypopyon. What is the name for this secondary glaucoma and what is the pseudohypopyon composed of?
Ghost cell glaucoma may present with a pseudohypopyon that is actually composed of degenerated red blood cells or erythroclast. These decomposing cells can mechanically block aqueous outflow.
What is the most likely cause for a shallow anterior chamber with a low intraocular pressure and a flat bleb in the immediate postoperative period following a trabeculectomy for primary open angle glaucoma?
Bleb leak
What is the main advantage of using dipivefrin over topical epinephrine?
Dipivefrin is a prodrug of epinephrine that must first enter the cornea to be activated by esterases within the stroma; hence systemic side effects are reduced.
Name three techniques that the patient can do to improve the absorption of ocular medications.
- Digital nasolacrimal compression. 2. Close the eye for 5 minutes after instillation of drops. 3. Wait 10 minutes in between the administration of different drops.
How can systemic sulfonamides produce glaucoma?
Systemic sulfonamides can cause idiosyncratic choroidal detachments and precipitate angle closure glaucoma.
Is a posterior embryotoxon typically associated with primary infantile glaucoma?
A prominent, anteriorly displaced Schwalbe’s line or posterior embryotoxon can be seen in Axenfeld-Rieger syndrome but is not typically seen in primary infantile glaucoma.
What is the most common reason for long-term visual loss in primary infantile glaucoma?
Amblyopia.
A glaucoma patient taking betaxolol, pilocarpine, acetazolamide, and dipivefrin is scheduled to undergo cataract surgery. Which of his medications should be discontinued temporarily?
Pilocarpine and adrenergic agonists such as dipivefrin can weaken the blood-aqueous barrier and worsen inflammation. They should therefore be discontinued prior to surgery if possible.
A patient with open angle glaucoma is started on carteolol eye drops to his right eye. What can you expect to see occur in the left eye after two weeks of therapy?
There will often be a reduction of intraocular pressure in the contralateral eye with unilateral use of a topical beta-blockers, although less than in the treated eye.
What are the main sources of blood supply to the anterior optic nerve?
Posterior ciliary arteries via the peripapillary choroid or the short posterior ciliary arteries.
