ophtha-lens and vitreous Flashcards
Part of lens
Central hard nucleus
Peripheral soft cortex enclosed by a capsule
Crystalline biconvex structure
Lens
Lens is held in position by
Zonular fibers (from ciliary body that fused with capsule at region of equator)
Where does the lens nuclei located?
Equator
Lens has sparse or numerous cells?
Sparsely cellular
Embryological origin of lens
from ectoderm from lens plate of 2 wk old embryo which becomes lens vesicle
Cells of anterior wall of lens vesicle will become
Sub capsular epithelium
Cells of posterior wall of lens vesicle will become
Primary lens fiber (which begins to fill in the cavity of vesicle to constitute the central region “central dark interval”)
Cells of equator of lens vesicle will become
Secondary fibers (which grows to surround embryonic lens)
Optical system of eye
Lens and cornea
When ciliary ms relaxes, zonules become tense, lens thinner = focused beyond retina = HYPEROPIA
When ciliary ms contract, zonules loosen, lens thicker = focused beyond retina = MYOPIA
Lens has passive/active metabolism
Active metabolism as shown by its high protein
Lens has no blood vessels, nutrition is from..
Aqueous thru selective osmosis
Sole source of energy of lens
Carbohydrates
What are the conenzymes found in glycolysis during anaerobic condi
ATP
DPN diphosphoridine nucleotide
Color of lens
Pale yellow
Darkens with old age
At old age.. What metachromatic color has difficulty reaching the retina?
Blue and violet metachromatic
In old age with change in color perception, the Blue color becomes ___
Green
Change in color perception is due to
Accum of metabolizes of aa, tryptophan
Factors that contributes to transparency of lens
Regular parallel arrangement of fibers with the nuclei at periphery
Curvature of surfaces
Refractive capsule
Location of geometric center at middle
(And in addition, smooth, gradual blending of refractive indices-capsule,cortex and nucleus)
Any disturbance such as . . . Will cause lens opacities or cataract
Change in curvature
Insinuation of water between individual fibers
Deposition of substance in capsule
Metab changes in lens is due to
Increase in Na and Ca content or
Decrease in K, glutathione ans as orbit acid content
(Which may lead to cataract)
Cataract is caused by
Metab changes
Permeability disturbance
Changes in aqueous, vitreous and ciliary body
(Other: heredity, racia predisposition, malnutrition, light, heat, radiation and endocrine disturbance)
How does cataract formed in diabetics
Hyperglycemia increases reduced sugar (sorbitol) in aqueous and by osmosis, it withdraw some water from lens.
How does cataract formed in changes in ciliary body
Catalytic changes in ciliary body which is responsible for increased formation of aqueous with the aid of carbonic anhydrase
Congenital absence of lens charac by small eyes (microphthalmic)
Aphakia
Diagnosis of aphakia
Presence of deep anterior chamber
Tremor of iris (iridodenisis)
Absence of purkinje image
Corneal and scleral scar, coloboma of iris and eccentric or irreg pupil may be present
Aphakia
Ophthalmic exam of fudge requires the need of high plus lens, approx..
+10 D
How is accommodation in aphakia
Completely lost
Lens used to focus rays of light in retina
Aphakia bifocal lens
T/f. In Monocular aphakia, wearing spectacles will not restore the binocular vision
True. Because of disparity of image size (anisokonia) between 2 eyes
Disparity of image size between 2 eyes
Anisokonia
Small lens with tendency to be spherical (spherophakia)
Microphakia
Microphakia is asso with
Ectopia lentis
Congenital weakness of zonules
In microphakia, when the pupil is dilated, the edge of Lens is seen all around the circumference of pupil = highly myopic
Microphakia is hereditary, recessive
Indentation or defect of lens equator asso with absence of zonule fibers
Lens coloboma
Spherical protrusion of ant or post portion of lens producing visual impairment
Lentiglobus
Lentiglobus vision is improved by
Refraction or lens extraction
Occurs as asymmetrical defect of zonule so lens is displaced away from the defective zonule fibers (as seen in semi dilated pupil)
Lens dislocation
Deep form of ectopia lentis is
Congenital
Lens dislocation is common in
Arachnodactyly or marfan’s syndrome
Charac by extreme length and thinned of bones, ms weakness and miosis
If lens dislocation is due to trauma, lens is displaces toward…
Inferior (for zonules affected are superior)
If lens dislocation is developmental type, lens is displaced..
Upward
S&s in lens dislocation
Blurring
Iridodenisis
Monocular Diplopia (if lens equator is seen at pupil)
Glaucoma (if ciliary body us irritated)
A gradual and progressive dse charac by Any opacity of lens with visual impairment
Cataract
Most common complaint in cataract
Cloudiness of vision
By presbyope so who’d discovered that they can read small fine prints without aid of their old reading glass
“Second sight”
Second sight is due to
Lenticular myopia form change of index of refraction
Principal objective sign in cataract
Lens opacity
In early nuclear sclerosis in cataract
Iris shadow
What can you see in ophthalmoscope in cataract
At distance may show black spots in fundus reflex against orange-red background
What can u see in ophthalmoscope when the lens is completely opaque
No fundus reflex
Dz procedure to determine the nature and position of the opacities in lens
Biomicroscopy
Type of cataract asso with local eye pathology (corneal infection, uveitis, glaucoma, vitreous hemo, retinal detachment, retinitis pigmentosa and tumors)
Complicated cataract
In complicated cataract, the opacities begins..
Beneath the capsule (as a result of changes in capsular permeability)
Is visual outcome of lens extraction in complicated cataracts can’t be predicted?
Yes
“After-cataract” “membranous cataract”
Secondary cataract
Type of cataract with opaque membrane due to incomplete absorption of lens ff trauma or incomplete surgical removal of lens
Secondary cataract
Type of cataract which is generally bilateral, opacity localized in ant or post pole and lamella may be involved
Hereditary type of developmental cataract
Most common type of hereditary type of developmental cataract
Ant axial embryonal cataract (appearing S&s multiplr fine opacities surrounded by faint halo)
It affects pregnant mothers during first trimester (maternal illness during fetal life)
Rubella (lens is isolated for 3 yrs after birth)
Hypothyroidism is asso with developmental cataract. What is its essential feature?
Low ration of Ca to P in bld
Some contraceptive drug have been found to induce cataract formation, such drug as ..
Thalidomide
Lens begins to lose its transparency with aging process
Senile cataract
Type of senile cataract where in the oldest fibers in center of lens lose their transparency
Nuclear (sclerotic type)
Type of senile cataract where in opacity involves outer layers
Cortical cataract
Type of senile cataract which tends to become hard and shrunken
Nuclear cataract
Type of senile cataract tends to swell and liquefy
Cortical cataract
Systemic cataract may be due to
DM
Hypothyroidism
Management for cataract
Surgical removal
Indication for surgical removal of cataract
Inability to perform usual work with aid of spectacles
Development of secondary glaucoma and uveitis
Binocular vision is attained only with aid of contraindication tact lens or intra ocular lens
Unilateral cataract
In young, surgery should be done ASAP if..
Both eyes have poor vision
Strabismus sets in
Young with cataract are prone to complications
Retinal detachment
Uveitis
Glaucoma
In rubella cataract, surgery is done
After 3 yrs
At what age will the zonule become hard to break, or be broken?
Before 40 y/o, zonule fibers are hard to break
After 20 y/o, zonules may be broken with aid of alpha-chemo trypsin
Method of cataract extraction where capsule breaks
Extracapsular extraction
Method of cataract extraction where lens is removed with capsule intact
Intra capsular extraction (not possible if pt is <20 y/o)
Ant capsule of lens is cut crosswise. The small knife is passed thru small puncture of cornea.
Discission
Extra capsular method procedure where ant capsule is ruptured. Lens subs is stirred by the same point instru used in penetrating cornea
Needling
Extra capsular method procedure done in young, where ant capsule is removed ASAP and the hard nucleus is expressed out. Bigger corneal wound is made.
Capsulectomy
Aka linear extraction because of linear corneal incision
Capsulectomy
Extra capsular method procedure where special app is that can be introduced anterior and post to lens with their rotating sharp edge slowly tearing the lens capsule and subs into small bits then aspired out
Lensectomy
Extra capsular method procedure where it uses special type of app used to dislocate anteriorly, fragments it by ultra vibration and finally aspirated the resulting small particles out
Phacoemulsification
Extra capsular method procedure that utilizes probe frozen -20 C
Cryoextraction
Extra capsular method procedure which uses lens capsule forces
Forcep extraction
Extra capsular method procedure which uses metal suction tip
Phakoeresis
Gel-like subs and constitutes the main bilk of eyeball
Vitreous
Volume of vitreous
4ml
The gel-like consistency, of oddity and viscosity of vitreous is due to
Due to a double fibrillation network system of collagen-like protein and hyaluronic acid which is suspended in large amt of water
Vitreous has the firmest attachment to the pars plana and retinal periphery
Vitreous base
Vitreous base extends __ mm anterior to ______
And from posterior to _____.
2mm anterior to Ora serrata on pars plana
And from posterior to Ora serrata on peripheral retina
Vitreous is also attached to (but less firmly )
Optic disk margin
Macula
Post peripheral surface of lens
Post peripheral surface of lens is called
Hyaloidocapsular ligament of Weigert
Anterior condensation of peripheral vitreous forms
Anterior hyaline membrane
Potential space between Lens and anterior hyaloid
Space of Berger
The cortical or outer layer of vitreous contains Small no of cells called..
Hyalocytes
Source of hyaluronic acid and has phagocytic effect
Hyalocytes
Embryological origin of primary vitreous
Protoplasmic processes of the lens vesicles and inner layer of optic cup
Mesenchymal cells enter the region of optic cup to contribute to ..
Primary vitreous
Formed by 9th wk by activity of vitreous and retinal cells
Secondary vitreous
Forms bulk of postnatal vitreous
Secondary vitreous
As the secondary vitreous increases in vol, the primary vitreous is forced forward to central position, the site of ?
Cloquet’s Canal
Produce by margin of growing optic cup which later becomes suspension ligament of lens
Tertiary vitreous
3 main symptom on pathology of vitreous
Positive scotoma
Photopsia
Impairment of vision
Flashing spots in field of vision
Positive scotoma
Light flashes esp on movement of eyeball
Photopsia
It is due to cast on retina by opacities floating in vitreous
Positive scotoma
It is due to much traction and/or prsessure in retina by partially detached vitreous body
Photopsia
It is due to opaque particles in vitreous
Impairment of vision
What can u see in ophthalmoscope in pathological vitreous
Scattered floater or opacities may appear black against red fundus reflex
IFN pa cities are more numerous and extensive, the fundus reflex is
Lost
Partial or complete failure of embryonic hyaloid vascular system to regress which produces white pupil in small eye
Persisted hyperplastic primary vitreous
Lost of gel-like consistency or conversion of vitreous into liquid
Vitreous liquefaction (syneresis)
Gel-like conversion of colloidal struc of vitreous (which occur on aged, myopic, in trauma and inflammation)
Vitreous liquefaction (syneresis)
This occurs when vitreous liquefaction results to separation of surrounding tissue (esp retina)
Vitreous detachment
Most common symptom in vitreous detachment
Photopsia or floater
Is vision not threatened in vitreous detachment?
Yes. Unless asso with retinal tears, detachment or vitreous hemorrhage
Vigorous opacities is caused by
Inflammatory cells (post uveitis, endophthalmitis)
RBC (vitreous hemo)
Saponified Ca soaps (asteroid hyalitis)
Cholesterol crystals (synchisis scintillans)
Tumor cells (RB)
Foreign bodies ff pentrating injury
Symptom of vitreous opacities
Seeing spots in field of vision to actual diminution of vision of varying degree
Caused by fine aggregates of vitreous protein due to age or myopia
Musca volitantes
Seen as floater spots darting ms and out of field of vision (esp when gazes is focused in an illuminated background)
Musca volitantes
Condensation of fibrillation struc of vitreous or actual fibroblastic or glial proliferation from vascular elements. Pigments epith cells is also the source
Vitreous band and membrane
Vitreous band is commonly seen in
Diabetic retinopathy or ff long standing vitreous hemorrhage
Thru corneal incision and aphakic pupil
Open vitrectomy
Vitrectomy Thru pars plana
Closed vitrectomy
