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Tear film test
 

Tear film test

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    Tear film test Tear film test Presentation Transcript

    •  MODERATOR:DR.SHWETA WALIA PRESENTER:DR. MONIKA SONI [ 1st YEAR RSO ] UPGRADED DEPARTMENT OF OPHTHALMOLOGY MGMMC & MYH INDORE
    •  The Value of tear fluid in preserving a clear cornea has been understood since ages. Blinking action of lids was essential for spreading the tear & maintaining a moist surface was obvious even in old ages. Presence of precorneal layer of liquid was first demonstrated by: FISCHER [1928]: Reflectography. ROLLET : Described it as the most superficial, sixth layer of cornea.
    • Lipid -secreted by Meibomian glands -situated in upper and lower lid margins Gland of Zeis –situated near base of eye lashes Aqueous- secreted by Lacrimal gland - it consists of an upper orbital &lower palpebral part . orbital part ;situated in fossa for lacrimal gland at the outer part of orbital plate of frontal bone.it is larger about the size & shape of a almond. Palpebral part: it is small & consist of only one or two lobules. Glands of Krause -situated in the conjunctival mucosa near the fornices, approximately 40-42 in upper lid and 6-8 in lower lid
    • Cont…Glands of Wolfring -situated near the upper borderof the superior tarsal plate &lower border of inf. tarsus 2-5 in no.Mucous secreted by Goblet cells –situated in the epithelium ofthe conjunctiva. Crypts of Henle –Invagination of superior peripheral conjunctiva near the superior fornix
    •  Mechanisms  Normal and voluntary eyelid action, with each blink.IACLE Module 1, page 67
    • TearsUpper and lower punctaUpper & lower canaliculi Lacrimal sac Naso-lacrimal duct Nose(valve of hasner)
    •  WOLF[1946]: First describe the structure of tear film. He coined the term “ PRECORNEAL FILM”. He assumed that it consist of three layers: An outer oily layer. An intermediate aqueous layer. An inner mucoid layer.
    •  Derived from secretions of Meibomian, Zeiss & Moll glands, cover the entire free surface of the tear fluid. WOLFF called it “MARGINAL TEAR STRIP” Chemically this layer mainly consists of lipids having low polarity: Wax & Cholesterol esters. High polarity lipids: Tg, FFA & phospholipids are presents in negligible amount. Thickness of this layer is about .1µm
    •  Middle layer :secreted by Lacrimal gland & accessory glands of Krause & Wolfring . Main bulk of tear film constituted by this film ; 95 %→60 %. The film covering the cornea is considerably thinner than over the conjunctiva. This layer is an aqueous solution of low viscosity, containing ions of inorganic salts, glucose, urea, enzymes, protein& glycoproteins. Lysozyme, lactoferrin,TSP &secretory immunoglobulin- A are main protein fraction. Buffering capacity of tear fluid is b/o bicarbonate ions & proteins.
    • Mainly secreted by conjunctival goblet cells, crypts of Henle & the glands of manz. Clear corneal epi. Is a relatively hydrophobic surface. Mucin mixed & spread by action of lids ,gets adsorbed on the cell membrane of epithelial cells & anchored by their microvilli forming a new hydrophilic surface on which aqueous & lipid layer spread spontaneously.It thus play a vital role in stability of tear film. Holly & Lemp consider it as the third layer of tear film
    • Functions of tear film Lipid Layer To prevent evaporation of aqueous layer and maintain tear film thickness As surfactant Aqueous layer Provide atmospheric oxygen to the corneal epithelium Atibacterial activity To wash away debris and noxious stimuli To provide smooth optical surface to the cornea Mucin layer Convert corneal epithelium from a hydrophobic to a hydrophilic surface. adhesion to the corneal surface responsible for maintaining the stability
    •  Tear fluid is clear ,salty ,slightly alkaline & watery.1.Thickness of tear film :average thickness 4-8µm.2.Volume : 7µl[4-13µl].Highest in youth & 10% of youth value by age of 70 yrs.3.Rate of tear secretion: 1.2µl per min. Total 24hr secreting volume:10cu ml.
    •  4. Turn over rate:18% per min. 5.Refractive index:1.357. 6.pH of tear:about 7.4[7.3-7.7]. Tear pH is lowest on awakening d/t acid by product of anaerobic condition & increases on eye opening d/t loss of CO2. Age,Sex ,time of examination,+nce of Pterygium & Pinguecula have little effect on ph. inflammatory cond. Of cornea &conjunctiva decreases pH..
    •  Osmotic pressure: 2mmhg[higher than aquous humor 0.1 & lower than plasma 25mmhg]. Optical integrity of the cornea is significantly influenced by tonicity of tear .o.p. significantly changed with reflex stimulation of tears. osmolarity: 300-310 mosm/l [0.9%NaCl aq. Sol.] More osm. of tear more severe is dry eye. Oxygen tension: 40- 160 mmhg.
    •  HORMONAL- 1.androgens are the prime hormones that regulate lipid production 2.Oestrogen & progesterone receptors in conjunctiva &lacrimal gland are essential for normal function of these tissue NEURAL- neural fibers adjacent to the lacrimal gland & goblet cells result in aqueous &mucus secretion
    •  The primary role of tear film is to establish a refractive surface of high quality for the cornea & to ensure the well being of the cornea & conjunctiva. Tear film accomplishes its functions by the highly specialized &well-organized dynamic activities:1. Secretion of tears.2.Formation of tear film.3.Retention & redistribution of tear film .4.Displacement phenomenon.5.Evaporation from the tear film.6.Drying & break up of tear film .7.Dynamic events during blinking.8.Elimination of tear.
    •  Tears are continuously secreted throughout the day by accessary(basal secretion) & main (reflex secretion) lacrimal glands. Concept of “basal tear secretion” is thought to be now obsolate. Even minimal tear secretion in undisturbed eye is thought to be secondary to light or temperature stimulation or both. Afferent pathway of this secretion is formed by Fifth nerve & efferent by parasympathetic(secretomotor) supply of lacrimal gland. 82% of full term newborn secretes tear within 24 hrs and 95% by 1st week Abnormal tearing start only after 4 months- b/o low innervation of cornea
    •  Corneal epithelium is a relatively hydrophobic surface Lemp and holly found that principal constituent of tear mucin responsible for wetting of corneal surface by converting the corneal surface from hydrophobic to hydrophilic one. Sequence of events in formation of tear filma. Lids surfacing cornea with a thin layer of mucusb. On this new surface, aqueous component of tear now spreads spontaneouslyc. Superficial lipid layer spread over the aqueous film contributing to its stability and retarding evaporation between blink
    •  Tear film is retained at a uniform thickness over the corneal surface against a gravitational force – wolff 1954 Outermost layer of the corneal epithelium and mucopolysaccharides play an important role in retaining tear film The fluid in the tear film is stagnant unless it is mixed by blinking and eye movements with the tear fluids in the marginal strip
    •  Surface of the cornea is covered by a film possessing a certain stability compressibility and elasticity which is almost unaffected by gravity This property is responsible for movement of particle in the film when lower lid is displaced upwards.
    • All lipids in the tear film including wax ester andcholesterolester retards the evaporation of thetear Evaporation of the tear film is estimated to be 10% of the production rate(1.2µl/min) Air motion has no effect on the evaporation rate because resistance to evaporation is mainly due to oily layer in tear film
    •  In humans the tear film has a short lived stability Normal tear film breakup time is 15-40 secs,when blinking is prevented the tear film ruptures and dry spot appear.
    •  When eyes open there is relaxation of orbiculris oculi Canaliculi and sac expand, creating negative pressure Draws the tear from the eye into empty sac When eye closes , contraction of pretarsal orbicularis oculi Compression of ampulla and horizontal canaliculi
    •  Simultaneously , contraction of lacrimal part of orbicularis oculi ( horners muscle) Compression of sac , creating positive pressure Tears flows down into the NLD & then into nose.
    •  Tear break up time  Conj. Scrapping• Schirmer test  CIC phenol red thread test  Ph Tear lysozyme assay  Tear evaporation rate Tear lactoferrin assay  Tear fern test Flouresene test  Flurophotometry Rose bengal staining  Tear osmolarity  Tearscope
    • 1.Tear film breakup time - It is abnormal in aqueous tear deficiency and meibomian gland disorder. 2% flouorescein is instilled in lower fornix, and ask pt. to blink several times. Tear film is examined at the slit lamp with a broad beam using the cobalt blue filter. After an intrval, black spot or lines appears in the fluorescein stained film-dry areas
    •  TBUT is the interval b/w the last blink and the appearance of the first randomly distributed dry spot. Normal TBUT: 15 to 45 seconds. No significant relation between age,sex,corneal sensation,palpebral fissure width,IOP,humidity or temp. with TBUT found. A significant decreae in TBUT-on holding lids aparts. TBUT decreaded significantly after use of BENZALKONIUM CHLORIDE & TOPICAL BETA BLOCKER,CIGARETTE SMOKE. TBUT <10 sec is abnormal.
    • 2. Schirmer’s test - For tear quantity Done with a strip of filter paper measuring 5 by 35 mm -Type-I –Done by placing the strip on lower fornix at the junction of outer 1/3 and inner 2/3 for 5 mins.More than 15mm of wetting in 5 min.-normal.Whatman filter paper 41 now standered. -gives the value for basic and reflex secretion of tears*Basal secretion test– conjunctiva is anaesthetized before performing the test
    • -Type-II - to know basal secretion of tears -Done by stimulating unanaesthetised nasal mucosa by cotton tip, and note the wetting aft 2 min. -This is seldom used Normal wetting is 15mm <5mm indicates severe KCS
    •  Type III- -To know the reflex secretion -ask the pt. to look directly in sun -no diagnostic value, and is potentially dangerous.
    •  Modification of Schirmers test-# Jones multiplied the distance of wetting of standard strip placed for 1 min by a factor of 3 &found it to correlate with a 5 minute reading#A modified schirmer test in which the standard strip intended to be placed for 5 min was moved to a different place if there was no wetting aft 1st 2 min, has been reported to obviate false positive results.
    • 3.Phenol Red thread test –obviate the disadvantage of schirmer ‘s test by eliminating the need for anesthesia. more efficient than filter paper. fine dye impregnated 75mm cotton thread is placed at the point of 1/3 distance from lateral canthus with eye in primary gaze for 15 sec.,alkalinity changes its colour to bright orange from tear contact. 10mm or less indicate dry eye..
    • Tear lysozyme assay - Most often tear lysozyme decreases before dry eyes are clinically evident. So it is of great diagnostic &prognostic value. Not popular4.Lactoferrin radial inmmuno diffusion assay –major protein secreted by lacrimal glands.performed using readily available kits -it is more sensitive &specific than any other test. -In milder cases, should be combined with schirmers test. Amt.of this molecule is closely resembles to tear production.Tear lactoferrin decreased in sjogren synfrome.
    • 5.Flourescein clearance Test5micro lt. of flouorescein on the ocular surface& measuring the residual dye in shirmer strip at interval of 1,10,20&30 mins. {under blue light using florophotometry} in normal eyes the values will have fallen to zero after 20mins.delay clearance is observed in dry eye.6. Tear osmolarity -normal value 302±6.3 mOsm/l -in KCS osmolarity increases(330 to 340 mOsm/l) -It is measured with 0.2 micro lt of tears, by measuring freezing point depression. - it is very specific diagnostic test for KCS
    • 7.Conjunctival scraping - stains with giemsa stain -in dry eyes it shows numerous goblet cells with pink cytoplasm and nucleus on one side of cell.
    • 8.Conjunctival impression cytology - It is a substitute for conjunctival biopsy. It is simple, easy, reliable, accurate, low cost, non invasive technique which can be repeated as often as required. Abnormal pattern precedes the ocular signs of xerophthalmia.
    •  It is to identifying the pathological changes occurring in conjunctiva i.e. squamous metaplasia. Technique- 1.samples are collected on Millipore cellulose acetate paper strips (3×10mm size with a diagonal edge). 2.Paper is applied near the limbus on the bulbar conjunctiva inferonasally and inferotemporaly. 3.kept for 3-5 sec , then removed with peeling motion by using glass rod and forcep.
    • 4.specimens are dropped into fixative sol. (ethyl alcohol, formaldehyde,and glacial acetic acid in 20:1:1 volume ratio )5.stained with PAS and HEMATOXYLIN or PAS & MODIFIED PAPANICOLAOU’S stain.6.Examined under light microscope & staged according to the degree of squamous metaplasia, the finding on conjunctival impression cytology have been graded according to the severity of dry eye state from 0 to 5 as follows
    • Stage 0: normal cellular structureStage 1: early loss of goblet cells withoutkeratinisationStage 2: total loss of goblet cells with slightenlargement of epithelial cellsStage 3: early and mild keratinisationStage 4: moderate keratinisationStage 5: advanced keratinisation
    • - Marginal tear strip characteristics : Marginal tear strip or tear meniscus is a continuous, full and slightly concave meniscus formed by the tears between the eyelid margin and the inferior bulbar conjunctiva- A height of 0.5mm of tear strip is considered a normal Scanty, discontinuous or absent tear strip is animportant sign of dry eye.
    • 10.pH ( hydrogen ion concentration)- Normal range 7.3 – 7.7- KCS patient exhibits slight alkaline shift in pH which was statistically insignificant11.Tear evaporation rate- Rolando and refojo devised a tear evaporimeter- Significant increased rate of evaporation is found in conditions like KCS, SJS, ocular pemphigoid and meibomitis- The instrument complex for routine diagnosis serve as a noninvasive diagnostic and research tool.
    •  TEAR FERN TEST -1.tears when dried on slide shows ferning.2.classified in the 4 group:A. Uniform arborisation and numerous branching are seen. little or no space between ferns.B. Branching is less and there is abundent space between ferns.C. Ferns are thicker and smaller with little branching and very large spaces between them.D. No ferning but amorphous patter is seen.
    • 3.Pattern A is normal while D suggests severe disease. Pattern C and D are associated with lack of lactoferrin and lysozymes in tears, prone to frequent infections.
    •  Fluophotometrey is considered a laboratory or research technique rather than a clinical technique Measuring the thickness of the tear film Assessing the tear fluid turn-over in normal and contact lens- wearing conditions Assessing the the permeability of the cornea in general and its component layers in particular in The normal eye The diseased eye the dystrophic eye The contact lens wearing eye Determination of corneal pH
    •  It uses a cold light source to minimize any drying of the tear film during the examination. It can be used directly in front of the eye or in conjunction with a slit-lamp biomicroscope to gain more magnification. Evaluation of the interference patterns of the anterior surface of the tear film lipid layer facilitates the diagnosis of the cause of dry eye symptoms, as well as screening patients for contact lens wear. It also allows the measurement of the non- invasive break-up time.
    •  FLUORESCEIN STAINING – Recorcinolphthalein with MW 376.27,orange red hygroscopic poweder producing intense green fluorescent colour at pH>5. large molecule unable to traverse normal corneal epithelium tight junctions . Shows area of denuded corneal epithelium and Punctate staining of cornea
    •  Pattern of srain; interpalpebral staining of cornea & conj. Is common in aquous tear deficiency sup. Conj. Staining –sup. Limbic keratoconjuctivitis Inf.corneal &conj. ;blepheritis & exposure keratitis.
    •  ROSE BENGAL STANING- Derivative of flouorescein- Affinity for dead and devitalized epithelial cells that have a lost or altered mucous layer- 1%sol. Or a moistened impregnated strip Stains damaged conj. And corneal epithelium, mucus threads and filaments as readily visible red color .
    • - bijsterveld found the dye to be very useful in diagnosis of KCS- He suggested a grading system of rose bengal staining in which palpebral aperture was divided into 3 areas, nasal and temporal conjunctiva and the cornea.- A score of 0 for absent,1 for just present, 2 for moderate staining and 3 for gross staining.- Total score of 3.5 of 9 considered abnormal
    • False-positive staining may occur inconditions such as chronicconjunctivitis, acute chemicalconjunctivitis secondary to hair spray useand drugs such as tetracaine andcocaine, exposure keratitis, superficialpunctate keratitis secondary to toxic oridiopathic phenomena, and foreign bodiesin the conjunctiva.
    •  Lissamine green staining:- Dark green water soluble substance- Norn first employed the dye for vital staining of the cornea and conjunctiva- He employed 1% soln and found that lissamine green has vital staining properties almost identical with that of rose bengal- It is less irritating as compared to rose bengal
    •  Dry Eye is a multifactorial disease of the tears & ocular surface that results in symptoms of the discomfort, visual disturbance, & tear film instability with potential damage to the ocular surface
    • Dry eye Aqueous deficient evaporativeSjögren syndrome dry eye Non-Sjögren syndrome dry eye Intrinsic Extrinsic Mebiomian oil Primary Lacrimal deficiency Vitamin-A deficiency deficiency Lacrimal duct Disorder of lid Topical drugs Secondary obstruction aperture preservatives Reflex block Low blink rate Contact lens wear Systemic drug Occular surface disease e.g.- allergy
    •  Increased discomfort after periods of reading, watching TV, or working on a computer. The symptoms of dry eye syndrome include persistent Dryness Redness Scratching Irritation Burning Often people with this condition may experience a feeling that something is in the eye.
    • Though dry eyes cannot be cured, there are a number of steps that can be taken to treat them. Treatments for dry eyes may include: Artificial tear drops and ointments Temporary punctal occlusion Permanent punctal occlusion Other medications Surgery Natural remedies
    •  Almost all are of aqueous substitutes.n0 mucus substitutes .paraffin is only approx.to the action of tear lipids. Drops & gels; cellulose derivatives [0.25-1% methyl cellulose.& hypermellose] Carbomers :adhere to the ocular surface & so are long lasting. Polyvinyl alcohol: increase the persistence of tear film Sodium hyluronate: promotes conj.& corneal healing
    •  Acetylcysteine [5%] drops may help in dispersing the mucus threads & decreasing the tear viscocity.
    •  Low dose of topical steroids : very effective in acute exacerbation. Topical cyclosporines[0.05-0.1%]: very effective drug .reduces t-cell mediated inflammation ,resulting in increase no. of goblet cells & reversal of squamous metaplasia. Systemic tetracyclines: may controls associated blepheritis & reduces inflammatory mediators .
    •  Useful in reversing the cellular changes in conj.of dry eye.[squamous metaplasia]
    •  Temporary punctal occlusion. Sometimes it is necessary to close the ducts that drain tears out of the eye. This is first done via a painless test where a collagen plug that will dissolve over a few days is inserted into the tear drain of the lower eyelid to determine whether permanent plugs can provide an adequate supply of tears. Initially the inferior punctal occlusion done. Permanent punctal occlusion. If temporary plugging of the tear drains works well, then silicone plugs (punctal occlusion) may be used. The plugs will hold tears around the eyes as long as they are in place.
    •  Low water content HEMA lenses : moderately dry eyes Silicone rubber lenses: no water & transmits oxygen .very effective in protecting cornea in extreame tear fillm deficiency,although deposition of debris on surface of lens may blur the vision. Occlusive gas permeable lenses: provides a reservoir of saline over the cornea.
    •  Reduction of room temprature Room humidifiers tarsorrhaphy
    •  Botulinum toxin injection :may control s the blepherospasm in severe dry eye  Zidovudine: may be beneficial in primary sjogren syndrome.  Submendibular gland transplantation; for extreme degrees of dry eye
    •  Vitamin A: cod liver oil, liver, carrots, sweet potatoes, butternut squash. Lutein and zeaxanthin: spinach, kale, collard greens. Vitamin C: strawberries, broccoli, oranges, Bioflavonoids: citrus fruits, cherries, grapes, plums. Vitamin E: sunflower seeds, almonds, hazelnuts. Selenium: brazil nuts, yeast, seafood. Zinc: oysters, hamburgers, wheat, nuts Fatty acids: cold-water fish
    •  Omega-3 Flaxseed Oil Vitamin A (Beta Carotene) Hyaluronic Acid N-Acetyl-L Cysteine Evening Primrose Oil Glucosamine and Chondroitin Sulfate
    • Thank you