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70 Cards in this Set
- Front
- Back
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Lens anatomy
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1. Lens capsule- BM secreted by the epithelium (type 4 collagen), it is thickest in the periphery near the equator, and thinnest posterior\
2. epithelium- nucleated cell in the anterior lens which end posterior to equator. The epithelial cells divide and elongate becoming lens fibers. lens fiber lose the nucleus as they sink to cortex (Nucleus persisent in Rubella, lowe's, trisomy 13) 3. Cortex - outer newer lens fibers 4 Nucleus - older lens fibers, embryonic and fetal lens nuclei 5. sutures - meeting of the lens fibers in the anterior and posterior lens, Y upright anterior, Y inverted posterior. Zonules: attach from pars plana to anterior and posterior lens capsule |
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Lens features
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has no blood supply or innervation, depends entirely on aqueous humor for metabolic requirements
n= 1.36, lens contributes 15-20D of total 60D (40D from air-cornea interface At birth 6.4mm equatorially and 3.5mm AP. While adults 9mm equatorially and 5mm AP. Lens power at birth 37D, adult 20D |
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Composition of crystaliine lens
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The lens has the highest protein content in body.
1. Water soluble protein a. alpha- largest (35%) b. beta- most abundant (55%) c. gamma- smallest 2. water insoluble- main intrinsic polypeptide, correlates with nuclear brunescence. |
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electrolyte composition of lens
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It is Potassium rich. And Sodium deficient.
Na/K pump, pumps K in and Na out. |
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Lens metabolism
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80% anaerobic, highest metabolic rate in the cortex
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Lens embryology
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day 25-27 optic vesicle forms
day 27 the surface ectoderm and optic vesicle thickens to form lens placode. day 29 lens pit forms, lens placode form the optic pit which becomes the lens vesicle. day 33 lens vesicle completes 7 week- Y sutures form 3 months-zonular fibers develop |
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persistant pupillary membrane
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remnant of tunica vascula lentis, seen as iris strands in pupil
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Lens changes with age
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weight is 3x the at maturity compared to birth (90mcg vs 255mcg)
AP diameter- 3.5 --> 5 equatorial diamenter-6.4 -->9 Increase curvature increase refractive power but offset by a decrease in refractive index Increase absorption of blue, violet, UV wavelength. Lens power at birth 37D --> 20D |
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Cortical cataract
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lens fiber fragments, degenerated protein, liquefaction, can have spokes, vacuoles, can mature to have morgagnian cataract
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Nuclear cataract
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Increase nuclear density, opacification occurs with aging, causes myopia (second sight), distance vision is worst, near less affected
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Post subcapsular cataract
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due to posterior migration of lens epithelium, bladder cell formation (eosinophilic globular cells with nuclei) Swells 5-6x the size. Cause by aging, trauma, steroids, inflammation, ionizing radiaton, RP, atopic dermatitis, werner's syndrome, DM, Rothmond's syndrome,
Glare and decrease vison on bright lights, affect near vision more than distance |
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Anterior subcapsular cataract
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fibrous plaque beneath anterior capsule, secreted by irritated metaplastic anterior epithelial cells secondary to trauma and inflammation
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Polar cataracts
anterior and posterior |
Anterior: small, bilateral and symmetric. Non progresive, 90% idiopathic. have good vision. Due to remnant hyaloid system. Assoc with microphhtalmos and lenticonus. Pathology: fibrous plaque beneath anterior capsule, secreted by irritated epithelial cells
Posterior: Larger, can progress, more visually significant (due to position close to nodal point. If AD (bilateral) If sporatic (bilateral). Assoc with a post capsule defect, tunica vasculosa lentis, post lenticonus, lentiglobus. Pathology: post migration of lens epithelium |
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coronary cataract
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AD, assoc with down's syndrome. has peripheral corneal opacities like a crown. cannot be seen unless pupil dilated, not visually significant
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Cerulian cataract
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blue dots in lens cortex, nonprogressive, not visually significant
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congenital nuclear catarct
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opacities in the embryonic nucleus or embryonic with fetal nuclei. bilateral
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capsular cataract
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small opacification of the lens epithelium and anterior lens capsule spare cortex, unlike polar cataracts they do not protrude onto AC. do not affect vision
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Lamellar cataract
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Most common type of congenital.infantile cataract. BL symmetric, appears like a sanddollar. Due to transient toxic exposure during embryogenesis
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Complete cataract
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highly visually significant cataract affecting all layers of the lens
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Membranous cataract
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lens protein resorbed from intact or traumatized lens , allow anterior posterior lens capsule to fuse to a dense white membrane, cause visual disability
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Drug induced cataract
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1. Corticosteroids- PSC, most common via topical steroids
2. Miotics - echthiophate iodide and demcarium bromide, cause anterior subcapsular vacuoles in adults but not children. 3. Phenothaizine, amiodarone- pigmented deposit anterior lens capsule, dose and duration dependant. Busulfan- PSC |
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Infectious causes of intrauterine cataracts
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causes 3% of bilateral cataracts
Think TORCHES Toxoplasmosis Rubella CMV Herpes, Varicella,Mump Syphilis Occurs early in first trimester |
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Traumatic and toxic cataract
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Contusion - stellate lens opacity
Vossious - occurs after blunt injury, pigment from pupil imprinted on the anterior capsule Soemmering's ring - remnant cortex fused between anterior and posterior capsule ocurring after cataract surgery or trauma siderosis lentis: iron depositing in lens epithelium chalcosis lentis: copper deposit in lens epithelium (sunflower cataract) Mercurial lentis:mercury deposits in lens epithelium electrical injury-lens vacuoles in lens periphery Non-ionizing radiation - true exfoliation ionizing radiation- PSC cataract |
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Radiation induced cataracts
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ionizing radiation - punctate opacity posterior capsule, feathery anterior subcapsular opacity.
Infrared: true exfoliation, cortical cortical UV radiation: damage by UV-B cause PSC Microwave: shown to cause cataract in LAB anmials, in humans controverisal |
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DDX Ectopia lentis
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marfan's
homocysteinuria weill marchesani hyperlysiniemia sulfite oxidase deficiency ehlers danlos aniridia trauma congenital glaucoma megalocornea sticker's medulloepithelioma tertiary syphillis rarely PXE |
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Marfan's syndrome
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AD, defect in fibrillin. Cause superotemporal ectopia lentis. Assoc: glaucoma, keratoconus, cornea plana, myopia, salt pepper fundus, RD. Tall, spidery hands, arm span > ht, heart disease, aortic dissection
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homocysteinuria
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AR, deficient cystathionine B synthase, accumulation of homocysteine. deficient cysteine and weak sulfhydryl links cause weak zonule. cause inferonasal lens displacement, myopia, retina degeneraton, RD risk in cataract sx. patients tall, blond, osteoporosis, MR. have hypercoagulability increase risk of thromboembolic event in GA. Diagnosis: nitroprusside test, urine test (high homocysteine), amino acid assay, low folate. treat with Vit B6, restrict methionine, supplement cysteine.
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Weill Marchensani
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AR, short stature, stubby fingers, broad hands, hearing defect, inflexible joints and MR
Ectopia lentis (inferior and anterior), microspherophakia, high lenticular myopia, cataract, microcornea, cause pupil block glaucoma |
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hyperlysenima
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AR, deficiency of lysine dehydrogenase, cause ectopia lentis, microspherophakia
Have growth, motor, mental retardation |
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Sulfite oxidase deficiency
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AR, enzyme defect that cause increase in urinary sulfite
have ectopia lentis, enophthalmos, brushfield spots. can have seizures, MR, frontal bossing |
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ehler's danlos syndrome
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defect in type 3 collagen, ectopia lentis, easy lid eversion, epicanthal folds, myopia, microcornea, blue sclera, keratoconus, angiod streaks
have hyperextensible joints, skin, poor wound hearing, bruise easy |
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Wilson's disease
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AR, have increase copper levels due to decrease in ceruloplasmin. copper is deposited in 1) basal ganglia causing spasticity, dysarthria, tremor, ataxia. 2)liver-cirrhosis 3)eye-copper deposition in peripheral descemets (kayser-fleischer ring), have sunflow cataract.
Treat with penicillamine, oral zinc. kayser fleisher ring resolves with treatment |
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Hallerman-Streiff syndrome -
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hypoplasia of the mandiple with birdlike face. one of few syndromes with glaucoma and cataract.
have microphakia, microcornea, glaucoma, cataract, can have a spontaneous rupture of the lens capsule. immune response to lens protein resembles phacoanaphylactic uveitis |
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Werner's syndrome
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Syndrome of premature aging. have scleroderma like skin, causes bilateral cataract
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Down's syndrome
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trisomy 21
assoc with snowflake cataract keratoconus |
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myotonic dystrophy
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AD, myotonia, of peripheral muscles, worsen with cold, excitement, fatique.
Have christmas tree cataract, pigmentary retinopathy, ptosis, lid lag, light near dissociation, miotic pupils, ocular hypotony. Other- myopia, testicular atrophy, frontal baldness, cardiac abnormalitity, facial weakness, insulin resistance, MR -cataract are NOT present at birth, usually asymptomatic from cataracts |
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alport's syndrome
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x-linked, triad of anterior lentiglobus, deafness, hemorrhagic nephropathy, renal failure.
have conj calcium crystal, corneal endothelial pigment, juvenile arcus, spherophakia, anterior polar cataract, pigmentary retinopathy, optic nerve drusen diagnosis: renal or skin biopsy. Lacks alpha 5 type 4 collagen in glomerular and epidermal BM |
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cataract surgery medical indications
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phacomorphic glaucoma
phacolytic phacoanaphylaxis Dense cataract unable to treat retincal condition. |
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IOL Calculations
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SRK:
IOL= A - 2.5(AL) - .9(avg Ks) Long: >26.5 SRK-T Med long: 24.5-26.5 Holliday Normal: 22-24.5 Holliday, SRT, hoffer-q short: hoffer-q |
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A scan errors
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.1mm error = .3D error
the shorter the axial length the more the error. Myopia: 1.75error/mm emmetropia: 2.35error/mm hyperopia: 3.75error/mm |
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A-scan concepts
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1. Ultrasound waves travel faster through lens (1640m/s) than aqueous or vitreous (1532m/s) than silicone oil (1140m/s)
2. immersion techniques more accurate than contact 3. silicone oil cause hyperopic refraction. Adjust IOL power by adding 3-3.5D |
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Viscoelastics in eye post cataract surgery, how long would it take for IOP spike?
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4 hours -/+ 1
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Scleral incision for correction of astigmatism
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6.0mm = 1.5 +/- .5
3.5mm = .5 +/- .3 |
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Placing scleral suture in sutured IOL, how far should needle pass posterior to the limbus
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0.75mm
avoid the 3 and 9 oclock it can damage the long ciliary artery and nerves |
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Cystoid macular edema following cataract extraction
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more common with ICCE than ECCE. 50% angiographically for ICCE vs 15% for ECCE.
FA: shows late leakage, petalloid hyperfluorecense, late staining of optic nerve differentiates the post op CME with other types of CME. treat with topical steroids and NSAID |
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alpha chymotrypsin
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enzyme used in intracapsular cataract extraction to lyse zonules prior to cryoextraction of lens.
The zonular fragments can cause blockage at the TM causing pressure spike. Not available in US, alpha chymotrypsin itself doesn't cause glaucoma |
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Use of NSAID in preop cataract surgery
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maintains intraop pupil dilation, inhibits prostaglandin release, a cause of intraop miosis
also inhibits platelet aggregation and wound helaing, increase chance of post op bleeding |
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Contact A-scan
-spikes and their correspondance |
6 spikes:
1. ant cornea 2. post cornea 3. ant lens 4. post lens 5. retina 6. sclera |
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-causes of falsely long AL
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1. post staphloma
2. measuring sclera instead of retina 3. wrong velocty (too fast) 4. fluid between the probe and cornea 5. wrong gate position |
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-causes of falsely short AL
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1. excess indentation cornea w/ probe
2. non-perpendicular measure 3. choriodal thickening 4. vitreous opacity 5. slow velocty 6. wrong gate |
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laser inferometer
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helium neon laser beam split and projected to the retina, produces interference fringes, the spacing of fringes can be varied.
Tests retinal function but the narrowest of fringes dicerned. Does not work well with dense cataract since laser will not pass throught lens to allow accurate results |
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Blue light entopscopy
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focus on blue light background, WBC coursing through perifoveal capillaries produce shadow. If patient can see then denotes macular function
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decentration of IOL
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causes:
1. asymmetric haptic placement 2. insufficient zonular or capsule support 3. presence of irregular fibrosis of the post capsule cause diplopia or polyopia due to prismatic effect. sunset syndrome: inferior displacement due to zonular dialysis, capsule tear, asymmetric haptic placement sunrise syndrome-superior dispalcement IOL due to asymetric haptic placement. can try pilocarpine, IOL repositioning, exchange |
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non-absrobable and absorbable sutures
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non-absorbable
- silk - nylon - polyester - prolene absorabable - gut -vircyl -monocryl -PDS |
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honan balloon
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device used pre cataract surgery to help reduce intraocular pressure after retrobulbar anesthesia.
help decrease risk of expulsive choriodal hemorrhage risk of CRAO, bradycardia (oculocardiac reflex) |
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atkinson akinesia
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anesthesia os sup branch of facial nerve.
adv. is lower face and mouth is spared. injection along the inf aspect of zygomatic bone and arch |
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O'Brien akinesia
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block of proximal trunck of facial nerve in front of ear. locate via locating the condyloid process of the mandible. performed by placing finger over the tragus and have pt open and close the mouth
inject into location but do not inject to joint |
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nadbath anesthesia
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facial nerve block
palpate space between ramus of mandible and mastoid process, inject local will ipselateral facial paralysis complication: since jugular foramen located medial to stylomastoid forament (pharyngeal n.) vagus n, spinal accesory n. inadvertant block cause difficult swallowing, speech, respiratoy arrest. |
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cataract surgery and hyphema
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swan syndrome- hyphema occur usually after cataract surgery, resulting from fine neovascularization of the incision
2. when incision is posterior 3. mechanical trauma from IOL haptic |
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corneal ulceration and melting after cataract surgery
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occurs most common in patients with KCS and RA
melting weeks after uncomplicated cataract surgery due to collagenase release form inflammatory cells |
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Epithelial downgrowth
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surface epithelium grows through wound into the eye covering the anterior segment
can occur in any intraocular surgery. increase risk in complicated surgery, assoc with hemorrhage, inflammation, vitreous loss, incarcerated tissue. epithelium: 1. can cover epithelium --> corneal edema 2. can cover angle --> glaucoma pathology: multilayer non keratizined squamous epithelium PAS stains goblet cells. diagnosis:argon laser to iris surface cause white burn. treat with excision of epithelial membrane with cryo of remaining corneal membrane |
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mechanism of lens accomodation
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ciliary muscle contracts, diameter of the muscle ring reduced, relaxes the tension on the zonular fibers, which allows the lens to become more spherical
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Lens pump leak theory
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K actively pumped tino anterior lens via epithelium. In post lens K diffuse out while Na diffuses in with the gradient.
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Lens coloboma
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a wedge shape defect or indentation of the lens periphery that occurs as an isolated anomaly or due to lack of ciliary body or zonular development. Typically located inferiorly and associated with uveal colobomas. cortical lens poacification can appear
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Decrease risk in cataract with intake of food rich in?
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leutin
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Clear corneal incisions are assciated with a increase risk of?
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endophthalmitis, mechanism not well demostrated. Theories: poor contructed wounds, wound burn, and transient reduction of post op IOP can result in poor wound apposition increasing risk of infection
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Goal of anterior vitrectomy in cataract surgery
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traction is a problem when there is vitreous loss in cataract surgery. Goal is to remove all vitreous anterior to the posterior capsule ensuring decrease risk of traction, best chance to decrease post op CME
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What measure has been most effective in decreasing post op endophthalmitis in cataract surgery?
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Use of topical 5% Povidine-Iodine soluiton at time of surgery
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Posterior infusion syndrome
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a intraoperative cataract surgery complication, in which fluid is misdirected into the vitreous cavity when performing hydrodissection, resulting in forward displacement of lens
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What is the best means to predict endothelial cell function? speclar microscopy? pachymetry
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The measuring of pachymetry in the early morning is a better predictor of post op enthothelial cell function than specular microscopy
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