OKAP Glaucoma Review
By:Yara Catoira-Boyle MD
Introduction to Glaucoma
* What is the definition of glaucoma?
* Group of diseases that have in common a characteristic optic neuropathy associated with visual field loss for which elevated IOP is the primary risk factor
* What are the 3 factors that determine IOP?
* Rate of aqueous production by the CB, resistance to aqueous flow (Juxtacanalicular TM) and the level of EVP
* Of those factors, what is the most common cause of increased IOP?
* Increased resistance to outflow
* What is the prevalence of glaucoma in the general population?
* 1.5-2%
* What the percentage of 1st degree relatives of POAG patients will develop the disease?
* 10-15%
* How many people over 45 y/o are estimated to have glaucoma in the US? What % is bilaterally blind?
* 2.25 million / 4%
* 10 million /2%
* 1 million / 5%
* 5 million /4%
* What is the most common cause of nonreversible blindness in AA in the US?
* Glaucoma (prevalence 3-4X higher than whites)
* What are the leading causes of blindness worldwide?
* Trachoma Cataract glaucoma
* Which one is NOT a risk factor for glaucoma?
* Increased IOP and AA race
* Positive family history
* Advanced age
* Thin central cornea
* Male gender
* DM, myopia, HTN, ischemic vascular disease, arteriosclerosis are all inconclusive
* Which one is correct about the prevalence of Chronic angle closure glaucoma?
* Inuit from Arctic Asians Whites
* Men women
* Myopes hyperopes
* Younger older
* Which one is correct about heredity of glaucoma?
* Prevalence among siblings of pts is 20%
* Lifetime absolute risk at age 89 is 10 x higher for relatives of glaucoma patients
* A single gene is likely to be discovered as the culprit
* The gene responsible for mutations of the TIGR (myocilin) protein is located on chromos 5
A little genetics of glaucoma
* TIGR protein produced by TM cells was id’d in Juvenile glaucoma, and later found to affect up to 3% of OAG
* GLC1A, the gene responsible for TIGR mutations is on chromosome 1
* It seems to be an autossomal dominant inheritance of the polygenic type with late or variable age of onset, incomplete penetrance and substantial environmental influence
IOP and Aqueous Dynamics
* What is correct about the aqueous composition?
* Has less hydrogen and chloride than plasma
* Has deficit of ascorbate
* Has excess bicarbonate
* Contains lysozyme, cAMP, steroid hormones and hyaluronic acid
* Which one is true of rate of aqueous production?
* It has a turnover of 1% per minute
* It increases during sleep
* It increases with age
* It increases during ocular inflammation
* What are the 2 major outflow pathways?
* Pressure-dependent/ TM/ conventional
* Pressure-indepdt/ Uveoscleral/ nonconventio
* What is true about facility of outflow?
* Increases with age
* Not affected by surgery, trauma, medications
* Varies widely in normal eyes, mean 0.22 to 0.28 microL/min/mmHg
* What are the 3 parts of the TM?
* Uveal, corneoscleral and juxtacanalicular
* What is false of the TM anatomy?
* TM is composed of many layers of colagenous tissue covered with endothelium
* TM has pressure-dependent flow
* TM functions as a one way valve
* The aqueous leaves the eye by bulk flow
* Laser trabeculoplasty causes apoptosis of Trabecular cells
* What is false about Schlemm’s canal?
* It is lined by endothelium and transversed by tubules
* It is a multiple channel
* Its average diameter is 370 microns
* The inner wall contains giant vacuoles that have direct communication with the intertrabecular spaces
* When IOP is low, blood may reflux into the canal
* The venous path of aqueous includes episcleral veins, anterior cyliary and superior ophthalmic veins and the cavernous sinus
* What is false about the uveoscleral outflow?
* It refers to any nontrabecular outflow
* Aqueous passes from the AC into the CBM and then into the supraciliary and suprachoroidal spaces
* It is decreased by cycloplegia, adrenergic agents, PG analogs and cyclodyalisis surgery
* It is also decreased by miotics
* It accounts for at least 5-15% of outflow
IOP and Aqueous
* What effect the following medications have on uveoscleral outflow?
* Cycloplegics
* Miotics
* Epinephrine
* Xalatan
* Brimonidine
* Timoptic ....
Clinical Evaluation
* Associate the external adnexae finding with a diagnosis associated with glaucoma
* “ash-leaf” sign
* Plexiform neuroma of upper lid
* Nevus of Ota
* Microdontia or hypodontia
* Port-wine stain (facial cutaneous angioma)
* Yellow or orange papules of skin of head/neck
* EOM restriction, proptosis, pulsating exophthalmos
* What is the type of glaucoma associated with the following corneal signs?
* Krukenberg spindle
* Exfoliating material on anterior chamber
* Keratic precipitates
* “stelate” KP’s
* “beaten bronze” appearance or corneal edema with iris changes
* What is not a possible cause of blood in Schlemm’s canal on gonioscopy
* Compression of episcleral veins with lip of goniolens
* Hypotony
* CC fistula
* Sturge-Weber syndrome
* Dilation of the pupil
* What is false about gonioscopy:
* Normal angle vessels are usually radial along the iris or circumferential on the CB
* Abnormal vessels cross the SS to reach the TM
* The nonpigmented TM is posterior to the pigmented TM
* A C angle indicates that SS is visible
* List potential causes for increased TM pigmentation:
* PDS
* PXF
* Malignant melanoma
* Trauma
* Surgery
* Hyphema
Gonioscopy
* It is false about gonioscopy
* It is necessary to see the angle due to total internal reflection at the tear-air interface (critical angle approximat 46’)
* Koeppe and Barkan lenses are examples of direct gonioscopy, most used in the OR
* Goldmann, Zeiss and Sussman lenses are used for indirect gonioscopy in the office
* Dynamic gonioscopy is done by asking the patient to move his eye
* It is false about gonioscopy
* The order of structures from anterior to posterior is: Schwalbe’s line-nonpigm TM-pigment TM-scleral spur-ciliary body-iris root
* Multiple methods of classification exist
* A Shaffer grade 4 angle is the narrowest
* Spaeth’s classification C40R indicates a normal and open angle
Clinical Evaluation
* What is angle recession and how is it different from cyclodyalisis on gonio:
* Angle recession is a tear between the longitudinal and circular muscles of CB= widened CB band
* Cyclodyalisis is a separation of the CB from the SS= gap between CB and sclera
* What is false of the Optic Nerve:
* Consists of about 1.2-1.5 million RGS axons
* The RGC cell body is in the ganglion cell layer of the retina
* The diameter of the intraocular ONH is about 2.5 mm
* There are 2 types of RGC’s: Magnocellular and Parvocellular...
OAG
* What percentage of patients with OAG have a screening IOP below 22?
* 30-50%
* What is the average corneal thickness by optical and ultrasound measurements?
* 534 optical and 544 ultrasound
* In the AGIS, patients had significantly better outcomes if their IOP was:
* Below 18 at all visits
* Below 18 50% of visits
* Below 14 at all visits
* Below 14 50% of visits....
Secondary OAG
* What is false about PXF?
* The odds of exfoliation glaucoma are 40% in 10 years
* The angle is often narrow with a +4 pigmented TM and a Sampaolesi line inferior
* The hyaline material is found on the lens, pupil margin, CB epithelium, iris PE, iris stroma, iris blood vessels and subconjunctiva
* SLE features include iris TI at pupil margin and iridodonesis or phacodonesis....
Traumatic OAG
* About hyphemas, is false:
* Sicke cell patients may have severe glaucoma from small hyphemas
* Acute IOP elevations may lead to AION or CRAO in patients with sickle cell
* Treatment consists of corticosteroids, cycloplegics, eye shield, limited activity, head elevation
* Aminocaproic acid is advocated since it has very few side effects and decreases rebleed
* Which drug is the best choice to control IOP in a hyphema patient with sickle cell diz?
* IV Diamox
* Iopidine
* Manitol
* Pilocarpine
* Timolol
OAG
* Regarding secondary glaucomas, which one is false?
* UGH syndrome can happen secondary to erosion of IOL haptic into the iris or CB
* UGH presents with chronic inflammation, iris NV, recurrent hyphemas
* Schwartz-Matsuo syndrome refers to elevated IOP after RD due to photoreceptor outer segmemts blocking of TM
* PKP related glaucomas can be of open or closed angle mechanism
* About 50% of people will have some elevation of IOP with the use of topical steroids
ACG
* About ACG epidemiology, what is incorrect?
* 10% of the 67 million cases of glaucoma worldwide are of ACG
* Predominant form of glaucoma in East Asia
* PACG is responsible for 91% of the bilateral blindness in China
* About the mechanisms of ACG, the incorrect is:
* Pupillary block is the most common cause of angle closure, including primary AC
* NVG is a type of ACG without pupillary block
* Marfan’s synd and Homocystinuria can lead to pupillary block by lens dislocation
* In Aniridia, Glaucoma is of open type since pupillary block can’t happen due to lack of iris
Primary ACG
* About the risk factors for ACG, the wrong one is:
* The prevalence varies with race: AA whites Japanese East asians Inuits
* White pts tend to have acute AC, while AA and asians have chronic asymptomatic diz
* Shallow AC, thick lens, short AL, small corneal diameter and radius increase risk
* Ages 30-50 are the highest risk
* More common in women and hyperopes
Acute PACG
* What is false about Acute PACG?
* Mild attacks can be broken with Pilocarpine 1-2%, but should avoid stronger miotics
* At IOP 40-50 the pupillary sphincter is too ischemic to respond to miotics and should use aqueous supressants, diamox or manitol
* The chance of acute attack in the fellow eye is 40-80% in 1 year
* High IOP during an acute attack may lead to ischemic nerve damage or retinal vascular occlusion
ACG
* What is false of iris and ACG?
* Both mydriasis and miosis can cause acute angle closure in a predisposed eye with shallow AC
* Miotics relax the lens zonules allowing it to sit forward in the AC, decreasing irido-lenticular touch
* Systemic medications including allergy, cold medicines, antidepressants, anticholinergics and topamax carry warning against glaucoma
* Peripheral iridectomy is indicated in patients with critically narrow angles, PAS, h/o previous attack, AC depth 2.0mm, +family history, +provocative test...
Childhood Glaucoma
* Mark the false :
* Primary congenital is the same as infantile glaucoma
* Glaucoma recognized after age 3 is termed Juvenile Glaucoma
* Glaucoma may present with buphthalmos if the IOP elevation starts after age 3
* Developmental glaucoma refers also to secondary glaucomas associated with inflammatory, neoplastic, hamartomatous, metabolic or congenital ocular or systemic anomalies
* Mark the false
* Congenital glaucoma is usually primary(50-70%)
* It is a rare disease (1:10,000 births)
* 60% are diagnosed in the first 6 months, 80% by one year
* 65% are female and bilateral in 70%
* Axenfeld-Rieger syndrome and aniridia are conditions associated with infantile glaucoma...
Medical therapy of glaucoma
* About beta blockers, which one is false:
* Betaxolol is selective for Beta 1 receptors
* They reduce aqueous production by 20-50%
* Are very additive to epinephrine
* Metipranolol was reported to cause iritis
* Effect starts within one hour and may last 4 weeks
* Tachyphylaxis and short term scape are seen
* Are contra-indicated in myasthenia gravis
Surgical Therapy
* What is false about surgical therapy of OAG?
* Usually undertaken when medical therapy fails
* LTP may be considered as a initial step in therapy since it decreases IOP by 20-25%
* The GLT showed that LTP patients did better than medication patients
* LTP is particularly effective in XFG and PG....
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