Module 4: Refraction and Ocular Health Flashcards
-case history
-analysis of visual needs/work
-Visual acuity
-depth percenption
-colour vision
-slit lamp/ophthalmoscope/ DFE
-neurological assessment
-glaucoma screening
-refraction
Exams inculde
-light rays bent/focused
-each eye has different refractive ability
-light bending relies on curve or cornea+ lens
-relies on clarity and density of cornea + lens
-ability of retina to recieve and transmit info
- length of eyeball (axial) changes refraction power
Refraction
-length from cornea to posterior pole
- average length 23-25mm (size of quater)
-light should focus at the fovea
Axial length
-cornea
-aqueous humor
-crystalline lens
-vitreous humour
Refracting system
-normal eye
-image lands right on the fovea
-no correction required
Emmetropia
-abnormal eye
- 3 types (myopia/hyperopia/astig)
Ametropia
-out of focus on the retina
-images land behind the retina
-farsightedness (blurry up close)
-cornea too flat/axial too short
-all babies start off this way
-corrected with convex lens (plus power)
-kids can accommodate/focus through
Hyperopia/Hypermetropia
-magnify objects
-objects seem bigger and closer
-px eyes look bigger
-can make “pincushion” effect(lines caved in)
-can alter depth perception
convex lenses
- light focused infront of retina
-near-sightedness (blurry distance)
-physiologic (steep corneas/long axial)
-requires concave lenses (minus power)
-uncommon at birth
Myopia
-minifying
-objects appear smaller/further away
-px eyes look smaller
-can cause “barrel” distortion (lines look round)
Concave lenses
-parallel light rays equally not focused
-cornea unevenly shaped/unsymmetrical
-football shape
-weeakest curve & strongest curve
Astigmatism
-reduction in ability to accommodate upclose
-ciliary muscles cannot buldge the lens enough
-additional plus power
-contact lenses MF/monovision
Presbyopia
-focussing ability
-muscle tight/contracts = bulges= near
-muscle rest/pulls = flat= distance
Accommodation
at least one diopter diference between OS/OD
Anisometropia
unequal size/image on the retina between OS/OD
Aniseikonia
-breakage of blood vessel
-blood pools/covers white sclera
-resolves in a few weeks
Subconjunctival Haemorrhage
-commonly referred “pink eye”
-bactieral
-viral
-allergy
-tocicity
Conjunctivitis
-progressive disease
-thinning cornea
-conical shape
-induces irregular astigmatism
-treated with rigid CL
-possibly hereditary
Keratoconus
-styes
-infection of glands/eyelids
-whitehead-like
Hordeolum
-clear lens becomes cloudy
-capsule holds transparent lens like enevelope
-lens is size of aspirin
-cloudy = light distorted/blocked out
-vision reduced
-lens continually grows/becomes hard
Cataracts
-natural part of aging
Senile Catartacts
-injury/lens is disturbed
- medications/steroids
-chemicals
-UV
-radiation
-smoking
- eye diseases
-diabetes
Traumatic Cataracts
Congenital cataracts
-babies born with them
-colour vision loss
-hazzing
-dark spots in vision
-needing brighter lighting
-glare at night
-near-sighted
-double vision
-better without glasses
-yellow/white pupil
Signs of cataracts
-slit lamp biomicroscope
-ophthalmoscope
-DFE
Detecting Cataracts
-sunglasses
-vitamins A,C,E,Zinc, Selenium, Magnesium
Cataract prevention
- surgery
-removal of cloudy part
-replacement of lens
Cataract treatment
-opening front of capsule
-pocket of side and back capsule left alone
-insert loop and pull out (still common)
-ultrasonic probe, 3mm incision (phacoemulsification)
Cataract extraction
-3mm incision
-probe vibrates at 40,000 times/second
-breaks up hard/cloudy lens
-suctioned out with vacuum
-femtosecond laser (bladeless)
Phacoemulsification
- if not replaced becomes aphakic
-intraocular lens (IOL) - IOL fits into capsule pocket left behind
- made of plexiglass
-use tiny spring loops to hold in place
-clear vision immediate
Replacing lens
- caspule pocket becomes yellow/cloudy
-fixed with YAG laser capsulotomy
-beams of light energy shot into eye
-quick pulses of laser energy
Secondary clouding
-produced in ciliary tissue
-fliud passes through space between lens&iris
-goes through the pupil
-collects in anterior chamber
-drains into trabecular meshwork
-then released into canal of schlemm
-goes into bloodstream via blood vessels in sclera
Aqueous Humour route
-blocked passage of aqueous humour
-causes IOP pressure to rise
-nerve fibers/ optic nerve damage under pressure
-when destroyed suport tissue sinks back=cupped position
-dreakdown of messages sent to brain
-leading to blindness
-asymptomatic in early stages
Glaucoma
-over 40 years old
-family history
-near-sighted
-diabetes
-african american
-injuries
Risks of glaucoma
- eye exam
-tonometry
-inspect drainage angles
-check ONH cup - disc ratio
-check peripheral vision
Dectecting glaucoma
- most common type
-gradual clogging of trabecular meshwork
-fluid cannot drain
-reason/cause unknown
-dangerous/slow &no warning
-irreversible
Chronic Primary Open Angle Glaucoma (POAG)
- no ONH changes
- no peripheral changes
- not glaucoma
- at risk to develope glaucoma
Ocular Hypertension
- can’t unclog meshwork
- prescription drops/ pills limits fluid production or increase drainage
-surgery thinning the walls (trabeculectomy)
Glaucoma treatment
- small flap created under top lid
- removes some sclera & meshwork
- moves into anterior chamber
- punctures small hole in iris
-flap stitched closed
-filtering bleb forms and absorbed into blood vessels
TrabeculeCTOMY
- alternate surgery
- uses argon laser (gas) energy
- aimed at meshwork
-clear clogged cannals
-temporary
-excimer laser (UV) new technology
TrabeculoPLASTY
- build-up eye pressure
1)blockage behind iris
-space between iris & lens too small
2)enlarged pupil makes iris bunch up
-no space between iris & cornea
-needs emergency laser surgery - unlikely to return again
Acute Glaucoma
-severe headaches
-nausea
-eye pain
-redness
-distorted vision
-limited action time
Acute Glaucoma symptoms
-uncommon
- babies born defective drainage
- resolved with laser surgery
Congenital Glaucoma
-caused by injuries, drugs, inflammation
- possibly temporary
- medication or surgery treatments
Secondary Glaucoma
- ONH damage with normal IOP
- possibly from hardend arteries that supple OHN
- medication to drop IOP lower
Low-tension Glaucoma
- eye unable to lubricate naturally
- seem too moist/too many tears
- low qaulity tears
- common over 50 years old
- increased by screen time
Dry Eye Diesease
- questionaires DEQ-5/OSDI
-tear meniscus height
-tear break0up time
-blink evaluation
-meibography
Diagnosing Dry Eye
- invasive dry eye test
-uses dyes fluoresence/lissamine green - stains cornea and conjunctiva
- tear break-up time
Meibomian gland expression
- invasive dry eye test
-tests the amount of salt in tears
-checking inflammatory markers - InflammaDry
Osmolarity
1)-tear deficiency or excessive evaporation
-inner muscus layer not covering eye/creates dry patches
-common as we get older
2)- diseases
-medications
-infections
-CL wear
-blepharitis
-environmental (wind/AC/dry)
-arthritis
-Sjogren’s syndrome (mouth too)
Causes of Dry Eye
- irritating condition of eyelids
-infect/plug meibomian glands (sebaceous)
-interrupts oil layer production - sometimes causes by injury
- use lid hygeine (wipes/ABMax/BlephEX) removes plaque in 10 mins. For only 4-6 months
Blepharitis
- Tiredness (end of day)
-Redness
-foreign body/burning
-blurry vision
-excessive tearing
-pulling/pressure behind eyes
-loss of lustre
-corneal deterioration
Symptoms of Dry Eye
- no known cure
1) blink often (18-20 blinks/minute)
2) conserve natural tears (avoid wind & fans/ drink water/humidifier)
-3) artificial tears daytime(use when needing to focus)
-ointment/gel (at night before bed) distorts vision
4) omega 3 (anti-inflammatory/ improve meibomian gland production)
5) Special treatments
-punctal plugs/ laser closure - prescription drops (restasis/Xiidra)
- antiboitics/steroids
-vitamin A
Treatment of Dry Eye
-most common dry eye type
-glands inflammed/clogged
-dont produce enough oil
-glands need to be drained/expressed
-warm compress treatment
- O.D. forceps & squeeze/ thermal pulsation (lipiflow/iLux)
- new options (amniotic membranes/autologous serums)
Meibomian Gland Dysfunction (MGD)
-breakdown of the macula
- 100 times more senstive than rest of retina
- macula contains most cones (detailed/colour vision)
- mono or binocular
- results in completes loss of central vision (peripheral is fine)
-leading cause of vision loss (1/3 over 65years)
- Dry AMD
-Wet AMD
-blisters/birthdefects/ injuries/infection/inflammation
Macular Degeneration (AMD)
- age
-smoking
-female
-UV
-family history
-high blood pressure
-diabetes
-obesity/poor diet
-light eye colour
Risks for AMD
-most common type 90% cases
- tissue becomes thin/stops working
- vision loss via size/#/location of drusen
- vision loss gradual and moderate
- treated with vitamins/lifestyle
Dry AMD
-small yellowish lesions that accumulate in the retinal layers
Drusen
- less common
- more visually devastating
-abnormal blood vessel growth behind macula causing choroidal neovascular membrans (CNVM)
-blood vessels break>bleed>heal> scar tissue
-new blood vessels in scar tissue>push retina away from wall
-new blood vessels fragile> distorts/damages macula - the longer this continues= more damange
-1/10 moves into both eyes
-treated with injections
Wet AMD
-symptoms may vary
-gradual loss of sharp vision
-distorted vision (shape/size/straight lines)
- gradual colour loss
- dark spot central vision
AMD symptoms
- Amsler grid test (card@ 30 cm> look at dot> wavy lines)
- colour vision test
-fluorescein Angiography Exam(OMD injects in arm>take pictures)
-Fundus Photos
-Digitial Imaging
-DNA testing
Diagnosing AMD
- use UV protection
- have good nutrition (limit fatty food)
- maintain good blood pressure
-don’t smoke - food with vitamin A,E,Zinc,Lutein,Zeaxanthin,Selenium, Omega3
AMD prevention
- diabetes mellitus (inability to produce insulin)
- changes blood vessles that nourish retina
-leakage of fluid/blood > big/disctructive branch vessels - retina cannot recieve/send clear images
-leading cause blindess under age 65 (25% prone)
-length of diabetes is most damaging (15% with under 4 years), (90% with 15 years +)
Diabetic Retinopathy
- non-proliferative
-most common/ least seerious (80% cases) - first stage of blood vessel deterioration
- only 20% progress further
-blood vessels in retina weak/change
-vessels small or big (balloon-like sacs) - burst and leak serum/exudate (fatty material)
- appear as yellow flecks
- leaks cause retina wet & swollen
-bloodstream normally reabsorbs= swelling temporary - can be both peripheral or macular
- only symptom = blurred vision
-typically dont need treatment
-serves cases need laser (focal/grid)
Background Diabetic Retinopathy
- leakage not extensive
- targets only certain spots
- cauterizes tissue>creates healing scar tissue
-scar tissue shuts/stops leak
Focal laser treatment
-too many leakages
-uses grid over the entire surface
- doesnt restore vision
-prevents further damage by drying retina
- may need serveral treatments/ can reopen
Grid laser treatment
- 20% of background progress to this
- leads to blindness when not caught early
-vessels close = no nutrients to areas of retina - happens in peripheral = narrow sight/poor night vision
-creates new blood vessels/very dangerous
-vessels increase rapidly
-bleeding into vitreous cavity/blocking light
-scar tissue>detach retina from choroid
-distort iris> blocks fluid > glaucoma - no pain/symptoms
Proliferative Diabetic Retinopathy
- lasers/ injections
-detroys/inhibits new vessels - panretinal laser photocoagulation (destroys new blood vessels growing), honey comb pattern, sacrifice peripheral vision to save detail and colour
-vitrectomy= last resort (prevents detatchment), suctions out vitreous> removes vessels> replace with air/gases until vitreous returns
Treatment Proliferative DR
- complication of diabetic retinopathy
- leaking = swelling of macula
- blurry vision/gradual loss
-occurs at any stage
-affects 2.5% diabetics - treamtent= focal laser/corticosteriods
Diabetic Macular Edema (DME)
- intact retina is crucial for vision
-1/10,000 effects by RD every year - various causes
- tears lead to detachments
- can also detach without a tear
-vision saved by immediate medical attention
Retinal Tears/Detachments
- age> vitreous shrinks> pulls away>pull retina> tear peripheral> fluid behind retina> detach from wall> no longer sensitive to light= blindness
- can thin and deteriorate= detach on its own
-serious hit/injury - eye surgeries
- increased in ner-sighted (grow oblong=pulling)
-severse internal inflammation
-tumours - diabetes
Causes of RD/Tears
-sudden flashes (response to trauma)
-increased floaters (impurties from tear)
- haze/strands
- sometimes no symptoms until detaching
-detachment= dark growing shadow peripheral (can become permenant without treatment)
Symptoms of RD/tears
-direct ophthalmoscopes = magnified small area of retina
-indirect ophthalmoscope= less magnified but larger area
-DFE
Diagnosing RD/tears
- can be reversed depending on intial damage
- tears easier than detachment
-40% regain vision - up to 6 months to fully heal
1) tears= laser beam/freezing cryoprobe> heat/cold>burn/freeze area>scar tissue>forms bond.
2) RD= A)remove fluid behind retina> press wall inward with pressure pad/silicone band> laser makes scar tissue (cryoprobe/radio freq diathermy)>bond tissue.
B)seperated far back/shrunk/puckered= vitreous broken up>suctioned out> air/gas replace (vitrectomy)
RD/tear treatments
- eye vision problems related to near work via computer
-50-90% of computer users
-22% have musculoskeletal disorders - greater risk in presbyopes (PAL = tilting head back/leaning foward= neck issues)
- presbyopia happening younger via computer use
Computer Vision Syndrome (CVS)
- eyestrain
- blurred vision
- headaches
- dry/irritated eyes
- light sensitivity
- double vision (diplopia)
- poor ergonomics
Computer Vision Syndrome symptoms
- condition of the px eyes
- visual ergonmics
- SV reading for low add px
-advanced presbyope =intermedaite/near bifocal
-PAL is good for intermittent computer use - best is task/computer lens (occupational lens)
- boost/antifatigue/bump add +0.50-0.75
- 20-20-20 rule
- adjust your chair (90 degrees/ floor to knee 2”-4”)
-set up your workspace (leg room 25”/ monitor height 26”)
-monitor/keyboard (16-30” from eyes/tilt away 10-20 degrees)
-Lighting (match room brightness 20-70 candles)
CVS treatment
- previously used to correct myopia
- reduced curvature of cornea
- tiny cuts with diamond blade
- temprorally relaxes peripheral cornea > allowing slight buldge out
Radial Keratotomy
- newest = wavefront analysis (no aberrations with pupil dilation)
- custom corneal ablation (removal of tissue)
Laser surgery
- excimer laser
- removes corneal tissue = curve change
- UV rays without heat= breaking molecule bonds
- computer controls energy required
- at depth of 10% corneal thickness
- takes 1 minute
-px wears CL lens/ drops 2-3 days post-op - stroma does not regenerate= permentant results
- 3 months for deeper layers to stablize
- mild to moderate myopia and thinner corneas
Photo-refractive keraectomy (PRK)
- epithelium/bowmans peeled back with flap
-excimer laser same as PRK - flap put back
- less healing involved
- faster clear vision
- moderate-severe myopia & astig
-less post-op haze/pain - newest form = sub-bowmans keratomileusis (SBK)> flap with cold laser = thinner/smaller flap
Laser in-situ keratomileusis (LASIK)
- Intracorneal rings “phakic IOL” (behind cornea) for low myopia
-Thermokeratoplasty (TKP)= heat to periphery>cornea steepens> reducing hyperopia
-Conductive keratoplasty (CK) newer = controlled release radio-freq
-Refractive/Clear Lens Exchange (RLE) = some process cataract surgery
-Implantable Contact Lens (ICL)= small CL inside eye
-KAMRA Inlay= small ring/pinhole into ONE eye
Other Refractive Surgeries
- 1/10 risk of undiagnosed vision problems
-1/30 amblyopia (lazy eye)
-1/3 refractive error
-1/100 eye disease
Children
- Amblyopia (lazy eye)
- congenital strabimus (eye turn)
-Anisometropia (uneven refractive error)
-high or oblique astig
-retinopathy of prematurity - congenital cataracts
- congenital glaucoma
- retinoblastoma (cancer)
-Nystagmus
-Coloboma (hole in iris/retina) - dislocated cyrstalline lens
-blindness
Childhood disorders
- first exam at 6 months (sooner if concerns)
- 80% hyperopic> intermittent strabismus
-common blocked tear ducts
Infants/Toddlers (birth-2 years)
- next exam at 3 years old (better idea of refraction)
- test depth perception/ colour vision
Pre-School (3-5 years)
-annual exams
- farsightedness stabilizes at age 7/8
-myopia can increase
- delayed learing could be visual
School age (6-18 years)
- Chemicals
- sudden loss of vission/veil
-penetrated injury
-forceful trauma/blow
-sudden halos/red, eye/brow pain - sudden eye pain
-foreign body
-sudden flashing lights/floaters - sudden droopy lid
- sudden red eye/crusting
Emergencies
- blurred vision gradual
-CL wearer discomfort - lost/broken CL in eye
Urgent issues
