PCO3 Exam 1 Outline.pdf

PCO Exam 1 Outline BioMicroscopy: Exam of External and Anterior Structures Anterior & External Evaluation ● Anterior and External evaluations are a MUST for every patient ● The best technique for eval is biomicroscopy but you can also use penlight with practitioner’s naked eye or penlight and binocu...

PCO Exam 1 Outline BioMicroscopy: Exam of External and Anterior Structures Anterior & External Evaluation ● Anterior and External evaluations are a MUST for every patient ● The best technique for eval is biomicroscopy but you can also use penlight with practitioner’s naked eye or penlight and binocular loupe Biomicroscope: ● Consists of ○ Illumination system ○ Observation system ○ And necessary apparatus for support and coordination ● Slit lamp examination (SLE) ○ Anterior and posterior ocular structure examination ■ Can use auxiliary lenses but not required ○ Contact lens examination ○ Treatments or procedures ■ corneal/conjunctival foreign body removal ■ collagen/silicone punctal plugs ■ Debridement ■ Epilation ○ Evaluation procedures ■ Goldmann tono ■ Gonio ■ Fundus biomicroscopy ■ Diagnostic dyes ● Sodium fluorescein ● Lissamine green ● Rose Bengal ● Advantages of biomicroscope ○ Stereoscopic view ○ Varying mags ○ camera/teaching tube adapters ○ Handheld models available ○ Varying illumination ■ Apertures ■ Filters ○ Different models ■ Haag-streit ■ Zeiss ● Biomicroscope design ○ 3 systems ■ Observation system ● oculars/eyepieces ● Mechanical system ○ Patient adjustment ○ Mechanical locks ○ Joystick ○ Etc. ● ● ● Illumination System (Koehler) ○ Filament imaged to objective lens ○ Mechanical slit imaged to patients eye ○ Zeiss type ■ Illumination comes from below ○ Haag-streit ■ Illumination comes from above ● Viewing arm ○ Biomicroscope ○ Adjustable focusing eyepiece ○ Magnification dials ● Illumination arm ○ Slit size ○ Slit shape ○ Filter controls ○ Variable size, shape, and brightness ● Central pivot point (co-pivotal) ○ Biomicroscope and illumination arms both coupled around the central pivot point ○ Parfocality ○ Both arms can independently swing along 180 degrees ● Magnification ○ Galilean changer ■ 3-5 mag changes ○ Other ■ Flip leaver near eyepiece to change illumination Microscope system principle ○ Oculars ■ Use astronomical telescope system ● 2 convex lenses placed one in front of the other and separated by the distance of their focal length ○ Galilean telescope system ■ Used for higher and changeable magnification ● Convex or concave lens used in line ○ Separated by focal length ● Telescope produces inverse image of object ○ Prism is needed to make it erect ■ Porro-Abbe Prism used ● 2 triangular prisms ○ Point of focus ■ The slit (illumination system) & microscope rotate about the point of focus ● Both at same point with same focus ○ AKA parfocality ■ Parfocality: ● When the microscope and light are both focused giving the coupling effect Parfocality ○ Achieved by having a common focal plane and common axis of rotation on the same focal plane ■ Exceptions: ● Sclerotic scatter ● ● ● ● ● ● ● Retroillumination ○ Parfocality is dissociated and slit beam is decentered Mechanical system ○ Adjustment of examiner and patient ○ Illumination & microscope maneuvering ○ Attachment for additional parts ■ Goldmann ■ Hruby ■ Etc Illumination system ○ Adjustable slit ○ Bright ○ Even ○ Fine focus ○ Components ■ Light source ■ Condenser lens system ■ Slit and other diaphragms ■ Filters ■ Projection lenses ■ Reflecting mirrors or prisms REVIEW PICTURES OF SLIT PARTS Click stop ○ Will vary position of reflecting mirror ○ Allows for change in angle of light beam with respect to viewing system Observation system ○ Optical elements give enlarged stereoscopic images ○ Magnification allows for larger WD in front of the patient ■ allows for manipulation ● Foreign body removal ● Auxiliary lenses ● Viewing of deeper structures ○ Magnification changs available ■ 10X ■ 16X ■ 25X ■ 32X ■ 40X Light Source ○ Filters ■ White light ● Used for general viewing purposes ■ Cobalt blue ● Shows fluorescein stained findings in cornea, view TBUT, corneal dystrophies ■ Wratten Yellow Filter ● Enhance contrast when using fluorescein and cobalt blue filter ■ Red free ● Used to enhance view of blood vessels and hemorrhages. ● Helps differentiate between retinal and choroidal lesions ○ Choroidal lesions disappear with red free filter Polarized Heat absorbing ● Used to decrease patient discomfort ■ Neutral density ● Decrease maximum brightness for photosensitive patients ○ Slit width ■ Narrow = slice through cornea ● Determine depth and thickness ■ Wide = inspect surfaces ● Measure lesions/pigmentations/etc ○ Slit height ■ Range from 0-12mm ■ Can change orientation ○ Slit rotation ■ Achieved by rotating lamp housing ● Before performing SLE ○ Clean!!! ■ Forehead band ■ Chinrest ■ Eyepiece (if sharing) ○ Make sure patient and examiner are both sitting comfortably ○ Let patient know what to expect during the SLE ○ Properly position patient ■ Make sure canthus is aligned ○ Provide fixation target ○ Adjust eyepieces ■ Correct PD of examiner ■ Correct for RE of examiner ○ Power on ○ Unlock base screw ○ Room illumination should be dim for better contrast Direct Illumination ● Direct illumination ○ Light beam and microscope focused on the same object ○ Used for: ■ Direct diffuse (wide beam) ● Overall viewing ■ Direct focal ● Parallelepiped ○ Broad view of one plane ● Optical section ○ “Cut through” a tissue for thickness and depth ● Conical beam ■ Specular reflection ■ Tangential illumination ● Diffuse illumination ○ Wide beam ○ Use for general observation of anterior segment ■ ■ ■ Allows for maximum illumination of the eye and adnexa at once Useful for: ■ Lids ■ Lashes ■ Caruncle ■ Bulbar conjunctival ■ Cornea ■ Iris ■ Pupil ■ Skin defects ■ Corneal scars ■ Pigmentations ■ Irregularities of lid/margins ■ Tear debris ■ Etc ○ Procedure: ■ Use wide beam ■ Illumination angle about 45 degrees (as long as its between 30-60 degrees) ■ Low mag (6X-10X) ■ Adjust angle of illumination to observe whole cornea ■ Use joystick to focus Optic section ○ Used for: ■ Determining depth or elevation of corneal defect or conjunctival defect ○ Useful in: ■ Assessing depth of foreign bodies ■ Location an opacity in a layer ■ Thickness of the conjunctiva or cornea ■ Determining presence of corneal edema, conjunctival chemosis, etc ■ Estimate anterior chamber depth (Van Herick) ○ Procedure: ■ Click stop at 0 degrees ■ Beam angle 45-60 degrees ■ Medium illumination ■ Low mag (6X-16X) ■ Beam width = 0.25mm (almost closed) Corneal Layers seen w optic section 1. Tear Film ■ Beam height = 7-9mm 2. Epithelium 3. Bowman’s Membrane 4. Stroma ■ Once cornea is in focus, scan the cornea 5. Endothelium ■ Increase mag to observe any details ■ For lens eval, use optic section to observe whole lens ■ For crystalline lens eval, use optic section, reduce angular separation of illumination source and place on pupil margin ● Crystalline lens will appear sectioned by layer Lens layers ○ ALL LAYERS MUST BE EVALUATED ○ For anterior of lens = slit lamp closer to examiner ○ For posterior of lens = slit lamp closer to patient A/C depth ○ Van Herick Angle Estimation Technique ○ ● ● ● Angle Grading: Grade 1: the width is less than 1/4 the corneal optic section, extremely narrow & will close w/ full pupillary dilation Grade 2: the width is approximately 1/4 the corneal optic section, narrow & is capable of closure Grade 3: the width is 1/4 to 1/2 the corneal optic section, angle unlikely to close Grade 4: the width is equal or greater than the corneal optic section, wide open ■ Uses to grade depth of angles EVERY PATIENT NEEDS THIS ESPECIALLY IF DILATING ■ Don't want an angle occlusion ● If a patient experiences an angle closure attack, they will not experience it in your office. It will happen after they leave once dilation goes down. Angle closure is an EMERGENCY ○ Technically only allows for nasal and temporal angles NOT superior or inferior ○ Procedure: & Barely done : Limbal Technique if U H ■ Optic section placed near limbus ■ Angle = 60-80 degrees ■ Mag = 16X ■ Short beam height ■ Grade angles from 4-0 (4 being most significantly open and 0 being closed) ■ Use split limbal technique to estimate superior and inferior angles ■ Slit lamp and illumination system at 0 degrees in click stop position ■ Focus optic section on limbal corneal junction (splitting cornea and limbus) ■ Observe arc of light through cornea and iris outside of slit lamp ■ The angular separation at the limbus corneal junction is an estimation of anterior chamber angle depth in degrees Direct illumination ○ Parallelepiped ■ Wider optic section (2mm-4mm) ● Height may vary ■ Provides a 3D view of cornea and crystalline lens ■ Procedure ● Illumination @ 45 degrees (between 30-60) ● Click stop at 0 degrees poster ● Mag 6-10X More VITRFOUS ■ Vitreous eval MOVEMENT ● Cick stop @ 0 degrees ● Beam angle 45-60 degrees ● Beam width 1mm-2mm ● Max beam height ● Focus the posterior lens capsule ● Move the joystick toward the patient and focus the beam behind the lens (vitreous) ○ Ask patient to move the eyes for movement of the anterior vitreous ○ Tangential illumination and oscillation Not used a- lot ■ The oscillatory movement of the slit lamp helps to see minute objects or filaments especially in the aqueous (you wouldn't be able to see these otherwise!). ■ Procedure: Observe more definition of structure ● Angle @ 70-90 ↳ elevative in ins cysts : tumors ● Moderate slit width ● Start with low mag ● Rotate reflecting mirror in an oscillating fashion until the desired lighting is achieved on the target structure ○ Spec reflection evaluate ■ BEST WAY TO mm FIND ENDOTHELIAL CELLS of the correl or epithelial cells on lens ■ Procedure: ○ . ● insman & · . is suspiciou ● ● ● ● ● ● ● ● ● ○ Parallelepiped Angle 60-90 Mag @ 25-40X High illumination Monocular view Place microscope angle at 30-45 degrees and illumination angle at 30-45 degrees from the midline ○ Has to be same for both Obtain a sharp, parallelepiped image of the cornea Advance across the cornea until the dazzle reflection of the filament is seen throughout the biomicroscope ○ Look for light reflex (only seen by 1 eye) ○ Look for the 2 filament images (one gold and one ghost gold) Focus the biomicroscope on the ghostlike image until the orange peel appearance is seen ○ Use high mag Conical beam ■ Use to examine A/C for cells or flare ● Important in inflammation cases ■ Must do before dilation and applanation tonometry ■ Procedure: ● Click stop @ 0 ● Angle @ ~60 ● Width @ conic section or parallelepiped of 1x2mm ● Max illumination ● Completely dark room ● Mag @ 25-40X ● Focus conical beam b/w cornea and anterior lens surface ○ Focus on iris @ pupillary region ○ Pull slit lamp back and ficus in the anterior chamber so light is seen Cells can be seen in the photo above, normally there would be just a black appearance passing through the out of focus cornea and lens forming a conical beam ● Observe the dark zone between the out of focus cornea and lens (normally optically empty and appears totally black). ● Convection currents of AH will move any protein or cells up and through this zone (count the number of cells seen in a minute). ■ Cells: ● WBC escape from dilated vessels ○ They appear as white floating dots because they reflect in the light. ■ Flare: Flare can be seen in the picture above ● Proteins leave dilated vessels ○ Makes the optic zone that should be empty appear gray or milky. Indirect Illumination ○ Sclerotic Scatter ■ Parallelepiped at the limbus to scatter light internally throughout the cornea ■ In the case of Central Corneal Clouding (CCC), it is observed with the naked eye, the angle of oculars is directly opposite from light source ● If (+) CCC, haziness will be seen ■ Procedure: ● MAg @ 6-10X ○ ○ ● Dyes ○ ● Click stop @ 0 ● Angle @ 45-90 ● Width 1-2 mm ● Maximum height ● Medium illumination ● Dark room Indirect Illumination ■ Decentered beam of light is focused in an area adjacent to the target area ● The observed area is not directly illuminated ■ This is useful for low contrast lesions or sutures (like corneal infiltrates or scar deposits) ■ Procedure ● Width 2-4mm ● Mag 10-16X Retro-Illumination ■ Parallelepiped bounces unfocused light on one structure to back illuminate another structure ■ There are 2 types of illumination ● Direct ○ Procedure: ■ Angle @ 0 ■ Used for crystalline lens and iris ■ Med-high illumination ■ Mag 10-16X ○ You have to retro illuminate the crystalline lens to grade cortical or posterior subcapsular cataracts using LOCS II. ● Indirect ○ Used for corneal evaluation ○ Allows for observation of corneal deposits on corneal epithelium & invading blood vessels Sodium Fluorescein (NaFl) Staining ■ Used to asses: ● Cornea ● TBUT ● Rigid CL fitting ● Epithelial defects in cornea or conjunctiva ■ Must use cobalt blue filter to assess ■ Will stain cornea and conjunctiva any time there is something off with the epithelium (pooling where the defect is located) ■ It is nonspecific ● A stain will appear if there is ANYTHING affecting the integrity of the epithelium ■ If there is something wrong with the corneal epithelium then negative staining (dark areas where tears separate quickly and not staining the tissue) will occur. ● Examples: ○ Map-dot dystrophy ○ Microcystic edema ○ Semi-healed abrasions ■ Xanthine dye ○ Rose Bengal ■ Pink staining of damage epithelial cells ■ You do not need a filter to observe this stain ■ Useful in keratoconjunctivitis sicca (KCS) or herpetic lesions ■ Creates A LOT of irritation and stinging ■ Xanthine dye ○ Lissamine Green ■ Not a xanthine dye ■ Is a phenyl methane dye ■ Stains membrane-damaged or devitalized cells ■ Dye localized in the cell nucleus ■ Safe and more comfortable than Rose Bengal Biomicroscope Anterior Segment Evaluation ● Process: ○ You must do slit lamp eval on EVERY pt ○ If you follow the same sequence every time you perform biomicroscopy you will ensure you observed and evaluated all structures ○ Each structure has a specific technique and illumination used during the evaluation ○ RECOMMENDED SEQUENCE: ■ Lids/Lashes ■ Tear Film ■ Conjunctiva, Sclera, Episclera ■ Cornea ■ A/C Angle ■ A/C* ■ Iris ■ Crystalline Lens* ■ Anterior Vitreous* ● Lids & Lashes ○ Instruct pt to close their eyes ○ Starting on the temporal canthus scan upper and lid & lashes ■ Diffuse illumination ■ Illumination arm @ 30 deg ■ Mag @ 6-10X ○ Ask pt to open eyes and scan nasal to temporal across lower lid & lashes ○ What you should observe: ■ Tear meniscus ■ Lid apposition ■ Meibomian Glands ■ Abnormalities/deviations within/amongst lashes ■ Collarettes or scales in lashes ■ Inflammation or infections ■ Tear prism ■ Telangiectasia ■ Globe apposition ■ makeup/tattoos (including permanent makeup) ■ Ectropion or entropion ■ Trichiasis or distichiasis ○ How to record findings: ● ● ■ Healthy (if everything is healthy) ■ If something is not healthy report significant findings Conjunctiva, Sclera, & Episclera ○ Ask pt to look up and inform them that you will be touching their lower lid/face ■ Wide parallelepiped ■ Illumination arm @ 30 deg ■ Mag @ 6-10X ○ Index finger must be close to lower lid margin in order to evert lower lid ○ Scan lower palpebral and bulbar conjunctiva and evaluate inferior punctum ○ Ask pt to look down and inspect superior bulbar conjunctiva by elevating upper lid with you finger ■ Make sure to tell the patient you will be touching their upper lid/face again ○ Inspect nasal and temporal bulbar conjunctiva by asking pt to look left and right ○ Evert upper lid ■ Tell pt you will be everting their lid ○ Inspect superior palpebral conjunctiva ○ What you should observe: ■ Elevations or depressions in conjunctiva ■ Discoloration ■ Openness of punctum ■ Inferior punctal regurgitations ■ Papillae or follicles ■ Injections or hyperemia ● Grading for judging injection types ○ Ciliary = Limbus ○ Episcleral = Sectorial ○ Conjunctival = Diffuse ● There is also a visual grading scale for hyperemia ○ How to record: ■ Healthy (if everything is healthy) ■ If something is not healthy, report abnormal findings ● Examples: ○ Pinguiculas ○ Concretions ○ Melanosis/ Nevus ○ Axenfeld Loops ○ Senile Scleral Plaque Cornea ○ Is evaluated temporal to nasal ■ Narrow parallelepiped ● Illumination are @ 30 deg ● Mag @ 16X ■ Optic Section ● Illumination arm @ 30-45 deg ● Mag @ 16X ○ Lid must be elevated to evaluate superior cornea ○ All corneal layers must be evaluated ■ Layer eval = optic section ■ Surface eval = parallelepiped ■ ■ ■ ■ ■ Corneal edema and scarring = scleral scatter Pigmentation = indirect retro illumination Keratic Precipitates = indirect retro illumination Corneal nerves = indirect retro illumination Vascularization = indirect retro illumination- Come should Not have vessels Corneal Neovascularization ● May find neovascularization ○ Neovascularization: blood filled vascularizations commonly due to CL overuse recent or longstanding ○ Ghost: Empty of blood vascularizations as a result of past corneal insult of inflammation ● ■ Endothelium eval = specular reflection ○ How to record: ■ Clear for all layers ■ If not, report abnormalities ● Corneal scars ○ White in color ○ Diagnostic of previous corneal damage/ulcer/abrasion/foreign body ● Corneal striate ○ White in color ○ Usually vertical ○ Threadlike twisting lines ○ Found in Descemet’s membrane & posterior stroma ● Corneal nerves : best seen wy indelt Illumination ○ White in color ○ Threadlike structures that bifurcate ○ Can be located anywhere in the cornea ○ Epithelial pigmentation ■ Krukenberg's Spindle ● Diagnosis of iris atrophy & pigmentary glaucoma ○ Transillumination should be performed if seen ● Could cause angle closure due to clogging which would raise IOP ● Anterior Chamber Depth ○ Use Van Herrick to estimate the A/C depth ■ Optic section ● Illumination arm @ 60-80 deg ● Meg @ 16X ● Beam height shortened ○ Every pt needs A/C assessed ESPECIALLY if dilation will follow ○ This is precautionary to prevent angle closure attacks ○ Only allows estimation of temporal and nasal angles preform gorio ○ How to record: -> Anything below I is occured augh ■ Grade between 0-4 (0 being closed and 4 being wide open) ■ If healthy, record deep and quiet along with angle grade ● Iris ○ Complete evaluation of the iris is necessary ■ Wide parallelepiped , ● ● Illumination arm @ 30-45 deg ● Mag @ 16X ○ To evaluate superior potion, you must elevate the eyelid ○ Observe: ■ Neovascularization ■ Iris nevi ■ Elevations ■ Atrophy ■ Transillumination ■ Pupillary margin reaction reflex ■ Etc ○ Use direct illumination and retro illumination for complete evaluation ○ How to record: ■ Healthy (if all structures are healthy) Crystalline Lens ○ Focus through pt pupil ■ Narrow parallelepiped ● Illumination arm @ 10-20 deg ● Mag @ 16X ○ Evaluate nasal and temporal ○ All layers must be evaluated ■ Anterior capsule ■ Anterior cortex ■ Nucleus ■ Posterior cortex ■ Posterior capsule ○ After posterior capsule, anterior vitreous is visible (temporal to nasal) ○ How to record: ■ Record the layer when recording opacities ■ If healthy, record: Clear Recording Examples Tonometry Introduction ● Tono measures tension in the eye ○ IOP ○ Combined resistance to deformity ● Uses for Tono: ○ All routine exams ○ Glaucoma Dx & management ○ Trauma ○ Uveitis ○ Medication side effects ● NOT USED ○ Direct manometry tonometry is ONLY used in research ■ It is SUPER invasive Digital Tono (Palpation) ● Uses fingers (digitalis) to estimate IOP ● This was the standard of care in the 19th and 20th century ● Procedure: ○ Use BOTH index fingers ○ Place over superior eyelid ○ Apply pressure with one finger while the other feels for stiffness or softness of the eyeball ● How to record: ○ Soft ○ Moderate ○ Hard ○ Tender to touch ○ Hard to touch ● Advantages ○ Quick and easy ○ No equipment needed ○ No anesthesia ● Disadvantages ○ Not a proper measurement (estimation) ○ Depends on examiner ○ Easy to over- or underestimate Tono By Indentation (Schiotz) ● You need a specific equipment kit ○ Includes ■ Plunger ■ Weights ● 2.5g, 5.5g, 7.5g, 10.5g ● Plunger is used to indent cornea ● IOP determined by how much indentation is produced by a certain weight ● This is less accurate than applanation tono ● Procedure: ○ Test tonometer using spherical mold in the equipment box and a 5.5g weight ○ Make sure the tonometer is correctly calibrated ■ Pointer should immediately mark 0 ○ Clean plunger and disc and wipe dry ○ Ask patient to assume a supine position with head support ■ Patient should not be elevating their own head ● Could increase IOP ○ Stand behind pt and make sure your hands are level with the pt head ○ Install topical anesthetic ○ Give pt a fixation point and instruct them to not move ■ You can tell the pt to hold their arm above their head and use their finger as a fixation point if there is not one on the ceiling ○ With your thumb and index finger, hold the pt eyelid open without putting pressure on the globe ■ Put pressure on the orbital bones not the globe ● Pressure on globe will raise IOP giving you an inaccurate reading ○ With the other hand, hold tonometer between your thumb and index finger and place the plunger on the pt central cornea ○ Allow disc to gently lower onto the cornea and note the reading ○ If the reading is less than 2, you need to add weight ■ 5.5g increase to 7.5g ■ Can indicate increased IOP ○ Repeat the procedure with the new weight ○ After the new reading is obtained, use the conversion table to determine the IOP with the weight that was used Tono by Applanation (Contact) ● Goldmann Applanation Tonometry (GAT) ○ First introduced in the 1950s by Goldmann ■ Became the “Gold” standard of tonometry ○ This is based on Imbert-Fick Law ■ “External pressure on a sphere equals the sphere's internal pressure multiplied by the area impacted by the external force (applanated)” -EyePatient.net ■ “The pressure in a sphere filled with fluid and surrounded by an infinitely thin and flexible membrane is measured by the counter-pressure which just flattens the membrane to a plane.” -Acevedo’s Slides ○ GAT measures IOP by force required to applanate a certain area of the central cornea ■ Required area of applanation = 3.06mm ○ Pressure inside an ideal sphere (P) is equal to force (F) necessary to flatten the sphere’s surface, divided by the area (A) that was flattened ■ P=F/A so F=(P)(A) ■ Pressure (P) can be determined if the force (F) is fixed or if the area (A) is fixed ■ One issue is that the cornea is NOT a perfect shape and is not infinitely thin and perfectly elastic thus being a variable to the Imbert-Fick Law ● Since there is this variable, some further considerations had to be considered ○ Surface tension force → caused by tear film ○ Bending resistance of the cornea → resistance to flattening (rigidity) ● The law was thus modified based on these considerations ○ ! + # = (')()) + * or ' = ■ ■ ■ ■ ■ !"#$% & F = force T = capillary attraction of tear meniscus (surface tension) P = pressure A = area C = corneal rigidity ■ ■ ■ ■ ■ GAT uses a biprism tip mounted on the tono head and positioned against the cornea The gradually increased force causes the cone of the biprism to applanate the central cornea until the required area of applanation is required (3.06mm) ● We technically are just adjusting the florentine ring to have an area of 3.06mm ● If applanation area is larger than 3.06mm: ○ Force inside globe is less than pressure being applied ● If applanation area is smaller than 3.06mm: ○ Force inside the globe is more than pressure being applied The pressure is read from the pressure application mechanism This is recorded and considered equal to IOP Procedure: ● Educate your patient on what you're about to do ○ “I am going to check the pressure in your eye” ○ You don't have to tell them the tono tip will touch their eye unless they specifically ask ■ If you tell them that the tono tip will be in their eye they may get nervous or experience anxiety which could cause them to flinch giving you a hard time to get the correct/accurate reading ● Dim room illumination ● Adjust pt and slit lamp ○ Disinfect slit lamp before pt places head on it ● Evaluate cornea ● Anesthetize cornea ○ Use Proparacaine 0.5% 1 gtt OU & 1 gtt NaFl OU ■ Will take about 13-15 seconds to take effect ● Patient may tell you their lid feels heavy or droopy ■ Effect will last for 15 minutes ○ Can also use Fluress ■ Combo of Benoxinate Hydrochloride 4mg (0.4%) and NaFl 2.5mg (0.25%) ○ Contraindicated if pt is allergic to Novacaine ● Disinfect equipment ○ Slit lamp ■ Wipe slit lamp with alcohol wipe ○ Tono tip ■ Hydrogen Peroxide (H2O2) 3% ● This can ruin the probes ○ If you do not dry the probe properly you can case the patient a corneal burn ○ Rinse probe really well ■ Opticide disinfecting solution ● Does not damage probe ● Place probe in Opticide for 3 minutes ● Rinse really well ■ Isopropyl alcohol 70% ● Can destroy probes ● Not as effective for cleaning ○ Specifically Hep B and Hep C ● Rinse and tap dry DO NOT dry with regular paper towels ● Can scratch probe ■ DO dry with kim wipe ● Tap dry Place probe on tonometer Align the white line on the probe carrier with the 180 deg marker ○ If pt has astigmatism over 3D, align red line with minus cyl axis Instruct pt to keep their head on the head rest & chin on the chin rest and do not move Give pt fixation target ○ One target for OD (EX: Dr. left ear) ○ One target for OS (EX: Dr. right ear) Before moving slit lamp, ask pt to blink a few times and then keep their eyes wide open ○ Pt should not blink during tono Set the drum on 1 ○ 1 = 10mmHg ○ Set to 10mmHg because average IOP is between 10-21 Place light source temporally to the probe ○ About 60-65 deg The view of probe and mires are only seen with one eye Position tono arm so that the applanation prism is aligned in front of left ocular ○ Tonometer must click Use wide, diffuse, high illumination with a cobalt blue filter and mag between 10X-16X ○ Light source should come temporally Direct probe with slit lamp toward pt cornea ○ Place your hands on the base of the slit lamp to carefully move the slit lamp closer to the patient ■ Make sure the joystick is positioned back toward the doctor ■ Move the slit as close as you can to the cornea without touching it and without looking through the oculars at first (roughly 1-3 mm before the pt cornea) ■ DO NOT make any sudden or rough movements ● Can abraise the cornea ■ Make sure the probe is centralized ■ Make sure there are no lashes or lids touching the biprism of the tono tip ● If lashes or lids are in the way you need to open the pt lid without applying pressure to the globe ○ Can use cotton tip application are apply pressure to the orbital roof ○ Look through the oculars ■ DO NOT move the slit lamp yet ○ Find ghost mires ■ Make sure they are equal in size and shape ● If they are not equal, follow the larger one until they are equal and centered ■ ● ● ● ● ● ● ● ● ● ● ● ■ ○ ○ ○ ○ ○ ■ ■ ■ Using ghost mires is the safest way to prevent disruption of the corneal epithelium After ghost mires are equal and centered, move slit lamp closer to cornea using the joystick Once you touch the cornea, the fluorescein mires will appear If aligned, applanate until the mires meet on the inner ring of both mires DO NOT move the slit lamp too far forward!!!! ■ Will cause an abrasion The mires should ideally measure 0.25mm - 0.30mm ■ Too thick = overshoot reading ■ Too thin = undershoot reading Errors in GAT: ● Amount of fluorescein ○ Not enough will cause mires to be too thin ○ Too much can flood the mires (too thick) ● Valsalva maneuver ○ When pressure in your head is increased as a result of a separate event ■ EX: throwing up ● Eye movements ● Eyelids ● Deformity in eyeball or cornea ● Surface attraction of the probe ● High astigmatism ○ >3D ● Successive measurements ● CL epithelial edema ○ Cornea thicker than normal ■ Thick cornea → more force to applanate → overestimation ■ Thin cornea → less force to applanate → underestimation ■ The average thickness is estimated at 550 um ● There is a conversion table available ○ Based on thickness, IOP reading is adjusted ● Increased venous pressure ● Inter-observer variability ● Accuracy of GAT calibration ● Increased pressure on the globe induced by the examiner ● Eyelashes between cornea and biprism GAT facts ● MUST be performed before dilation/cycloplegia ● Standard care for glaucoma pts ○ Not diagnostic of glaucoma ○ Ocular HTN ■ IOP over 21mmHg w/o optic nerve head damage or visual field defects ● Finalize pt refraction BEFORE GAT ○ Anesthesia may cause blurry vision which can result in an inaccurate Rx Helpful hints when performing GAT ● ● ● ● ■ ■ Pearls ● If fluorescein is pulsating, its due to venous pulsation w/im the eye and cardiac cycle ○ Take several measurements and average them Make sure pt is not too far away or breathing too heavily In contact lens wearers: ○ Pt should NOT reinsert CL for at least 1 hour after GAT ■ Will stain yellow permanently ● Must throw CL out if it gets stained ○ DO NOT insert a RGP or SCL right away ■ Anesthesia will cause the pts cornea to be numb so they won't feel pain if RGP/SCL is put in wrong and can cause a 2ndary corneal abrasion In astigmatic patients: ○ IOP is underestimated by 1 mmHg for every 4DC of WTR astigmatism ○ IOP is overestimated by 1 mmHg for over 3DC of ATR astigmatism ○ To help this, prism should be aligned with flattest K reading ■ EXAM QUESTION: If pt K reading is 42.00@040/46.00@130, where would you align the red line? ● ANSWER: Align to 040 mark Eyelashes between cornea and probe will cause inaccurate readings and may leave SPK ● After tono, examine cornea to make sure no keratitis or abrasions ○ Evaluate with cobalt blue filter and NaFl ● If SPK, treat with artificial tears, preservative free ● Make sure no corneal edema ○ If you didn't rinse the probe enough edema will be present ● If pt has ant. seg. conditions, NCT is preferred over GAT IOP facts ● IOP varies over 24 hrs by about 3 mmHg - 5 mmHg ○ Called diurnal fluctuations ○ Highest readings will be in the AM ■ ALWAYS record time IOP was taken ● For glaucoma pts or pts suspective of glaucoma: ○ Take diurnal curve ■ Several measurements ○ Spikes with variations greater than 5 mmHg are considered suspicious ● IOP differences higher than 4 mmHg between the eyes is considered suspicious ○ Look more into why the pressures are so different ■ Could be: ● Glaucoma ● Retinal detachments ● Uveitis-iritis ● Poor technique ● Poor calibration ● After LASIK and PRK ○ IOPs are underestimated ■ About 10 microns of tissue removed PER DIOPTER of RE ■ How to record: ● Method, eye, pressure, time ○ EX: GAT: OD 13 mmHg, OS 11 mmHg @ 3:30pm Perkins Tono ● Basically Goldmann but handheld ○ Still applanation tono Combined Systems Principle ● Electronic Indentation Tono ○ Two types ■ MacKay-Marg ■ Tonopen ○ Electronic device that converts the eyes pressure into electronic pulse signals and calculates it to mmHg ○ Useful for kids, veterinary, and non-cooperative pts ● MacKay-Marg ○ Combination of applanation and indentation processes ○ Introduced in 1959 by MacKay and Marg ○ Has an applanation area of 3.06mm ■ Obtained by the footplate ○ Force of applanation is identified with a notch in the electrical waveform ○ IOP can be calculated since area is known ○ Less dependent on corneal factors ■ Works well in irregular or scarred corneas ● Tonopen ○ Same principle as MacKay-Marg but smaller, handheld, and battery powered ○ Useful for screenings, bedridden pts, or OR ■ Can be used through a bandage SCL if it cannot be removed ○ Uses disposable latex covers ■ Changed between every pt ■ Make sure pt doesn’t have latex allergy ○ Takes an average of 4-10 readings and gives a statistic indicator of reliability Pascal Dynamic Tono (DCT) ● Uses contour matching not applanation ○ This eliminated all errors associated with applanation ● Uses a mini piezoresistive pressure sensor embedded within the tono tip that is contour matched to the shape of the cornea ● Tono tip rests on cornea with constant appositional force of 1g ○ Probe force is variable ● When sensor detects a change in pressure, electrical resistance is altered and the DCT computer calculated IOP from that change ● Measures ocular systolic and diastolic pressure ○ Ocular pulsatile activity ■ Ocular pressure amplitude Ocular Response Analyzer (ORA) ● Non-contact tonometer ● Gives IOP values independent of biomechanical corneal properties ● Uses jet of air lasting about 10 msec ○ Older ones applanate about 1-3 msec ● ORA records on both onward and backward applanation ○ Difference b/w those two values is Corneal Hysteresis which is a direct measurement of corneal biomechanical properties ● Corneal Hysteresis (CH) ○ Provides info about the viscous properties of the cornea ○ Corneal Resistance Factor provides info on eleatic properties ○ Viscoelasticity = effect of corneal thickness rigidity ■ The ability to absorb and dissipate energy ○ Can be indicative of disease ■ Keratoconus ■ Fuch’s Corneal Dystrophy ■ Glaucoma ○ Mean CH value between 10.24 - 10.7 Non-Contact Tono (NCT) ● Was invented in 1970 because optometrists were not allowed to use anesthetics ● It is an air blast to the cornea ● The deformity from the air blast is measured by photoelectric cells ● Good for pts allergic to anesthesia, have corneal damage, or during screenings ● Systems of NCT ○ Alignment system ■ Aligns the pt ○ Optoelectronic applanation system ■ Transmitter: directs collimated beam of light tat corneal apex ■ Receiver and detector: accepts ONLY parallel coaxial rays of light reflected from the cornea ■ Timer: measure internal reference to the point of peak of light intensity ○ Pneumatic system ■ Generated airpuff against the cornea Transpalpebral Tono ● Applies pressure on the eyelid until retinal phosphenes are experienced ● The pressure applied is proportional to IOP ● Useful in kids, special needs pts, bedridden pts, and at home IOP monitoring ● Limitations: ○ Scleral rigidity ○ Thickness of eyelids ○ Tone of orbicularis muscle ○ Potential intra-palpebral scarring Rebound tono: ICare ● Initially used by vets ○ Avoids anesthesia of heavy sedation ○ Uses two coils coaxial to a probe shaft that bounces back a magnetized probe off the cornea and detects deceleration of probe caused by the eye ○ Voltage produced proportional to the probe speed ○ All variables are linked to probes movement ■ The inverse of deceleration speed seems to correlate with IOP ○ The probe is a tiny 1.8 mm diameter plastic ball on a stainless steel wire held in place by an electromagnetic field in a hand held battery powered unit ○ When the button on the back is pushed, a spring drive the plastic ball forward rapidly ○ When probe hits the cornea the ball and wire decelerate ■ Higher IOP = more rapid deceleration ○ ○ ○ ○ ○ ○ ■ Lower IOP = slower deceleration Speed is measured internally and a chip calculates IOP No anesthesia needed Least contact time with eye when compared to all tono methods Probes are disposable ■ Change between patients Pt must be sitting straight Accuracy may be an issues especially if the IOP reading is being used for long term management Gonioscopy Functions of AH ● Helps to maintain eye shape and structure ○ Constant volume of AH helps maintain IOP ● Carries O2 and nutrients to the posterior cornea and lens ● Carries waste products from lens to cornea ● AH is a low viscosity fluid ○ Secreted from plasma components by ciliary body into posterior chamber of the eye ○ Following this, the AH travels to ant chamber and drains into the systemic cardiovascular circulation ● Rate of secretion & drainage: about 20uL/min ● Normal IOP 10-21mmHg ○ Avg 15 mmHg Aqueous Humor ● Produced by NPE of ciliary body ○ Travels to the post chamber ● Passes through pupil and then gets circulated into ant chamber ○ 90% drained through trabecular meshwork ■ Conventional route ○ 10% drained through uveo-scleral pathway into subchoroidal space and channeled by the venous circulation of CB ■ Unconventional route Factors influencing IOP ● Production of AH is generally sable ○ Can decrease due to medication, hypoxia (low O2), hypothermia (low temp), etc ○ Inc IOP caused by decreased outflow of AH ○ Outflow resistance increases by: ■ Age ■ Pupillary block ■ TM block ○ Outflow resistance decreases by: ■ Accommodation ■ Medications ● Miotics ● Prostaglandins ● Adrenaline ○ Rate of AH formation ■ Uveitis ● CB affected ● Less AH produced ● Increase IOP by persistent inflammation (cells in TM) ● Acidosis and hyperosmolarity ○ Causes decreased AH production ● Decline in BP ○ Due to less plasma ● Decreases by retina, choroid or ciliary body detachments, medications, and general anesthesia ○ Medications to lower IOP: ■ Beta-Adrenergic Antagonist ■ ■ ■ Alpha-Adrenergic Agonist Carbonic Anhydrase Inhibitors (CAI) Prostaglandin Analogue ● First line of treatment unless inflammation is present Gonioscopy ● Used to observe and evaluate the ant chamber angle ○ Gives info about type of glaucoma ■ Open or closed angle ● Other ways to asses ant chamber: ○ High frequency ultrasound biomicroscopy ○ Ant segment optical coherence tomography ● When to perform gonio: ○ Narrow or suspicious angles in Van Herrick ○ Events of ocular ischemia ■ RVO, RAO, DM, Ocular Ischemic Syndrome ○ Pigmentation in corneal endothelium ■ Pigment Dispersion Syndrome (PDS) ○ Glaucoma evaluation ○ Chronic inflammations ■ Acute or recurrent uveitis ○ Trauma ■ Blunt trauma ■ Foreign body ■ Fresh hyphema or perforated globe ● Angle structure ○ Iris ■ Blood vessels are located in stromal layer with radial orientation ● Frequently visible on lightly pigmented iris ■ Insert into face of the CB, posterior to the SS ○ Ciliary body(CB) ■ Functions: ● AH production and regulation ● Accommodation ● Blood aqueous barrier ■ Muscle fibers: ● Circular for accommodation ● Longitudinal pull to open the TM and Schlemm’s Canal ○ Scleral spur (SS) ■ Site of attachment for longitudinal muscle fibers for the CB ● Pulls on spur and opens TM ■ Beige colors but yellows with age ○ Trabecular Meshwork (TM) ■ 60-90% of AH flow ■ Anterior TM usually non-pigmented ■ Posterior TM becomes more pigmented with time ○ Schlemm’s Canal ■ Located at the base of scleral sulcus ● Not visible ■ Drains into venous system ● Can close under pressure Schwalbe’s Line (SL) ■ Transition zone between TM and corneal endothelium ■ Transition from scleral curvature to steeper corneal curvature ■ Flat in most eyes but can form rigid ■ Pigment in SL ● This is called Sampolesi’s Line ○ Iris Process ■ Uveal extension from iris to TM and insert close to SS but can extend to SL ■ Usually fine ● Extends into posterior TM ■ Does not inhibit iris movement ■ Can be broken in angle recession ○ Sampolesi’s Line ■ A settling of pigment on or anterior to SL ● Important to investigate for pseudoexfoliation Syndrome ○ Pseudoexfoliative Glaucoma ○ Posterior Embryotoxon ■ Prominent anterior SL ■ Normal variant present in about 30% of population ■ Can be associated with Axenfeld-Rieger’s Syndrome ○ Blood in Schlemm’s Canal ■ Can be seen due to compression of episcleral veins with a larger diameter rigid CL ● If too much pressure is applied ■ Could be due to low IOP an high episcleral venous pressure ● Ocular hypotony ● Excessive gonioscopic pressure ● Sturge Weber Syndrome ● Carotid Venous Fistula ○ Angle vessels ■ Normal radial orientation in iris with normal caliber ■ Visible in light irises ■ NVI are fine vessels and often cross SS ■ Prominent iris vessels ● Generally an important sign of a significant vascular disease progression ● Very important to rule out: ○ Posterior pole conditions ■ CRVO ■ BRVO ■ PDR ○ Can lead to NVG ● Anatomy of an open angle ○ CB ○ SS ○ Posterior TM / anterior TM ○ Schwalbe’s Line ○ Cornea Gonio indications ● Any pt with VH less than 2 ○ ● Glaucoma ○ Open or closed ○ Primary or secondary ● Glaucoma syndromes ● Glaucoma suspects ● Predispositions to NVI and NVA ● Hx of eye trauma ● Iris lesions ● Angle neoplasia ● Synechia ● Uveitis ● Contraindication ○ In presence of corneal penetrating injuries ○ Hyphema Optical principles ● The ant chamber cannot be visualized due to the internal reflection of an intact cornea ● The refractive index of a gonio lens is similar to that of the cornea ○ This can eliminate reflection by replacing the film-air interface with a tear-film gonio lens surface Gonio lens ● Direct and indirect view gonioscopes ○ Direct view types: ■ Koeppe ■ Hoskins-Barkan ■ Swan-Jacobs ○ Direct view optics: ■ Light from the angle exits the eye nearly perpendicular to the lens/air interface ■ Light rays from the angle are viewed directly without reflection inside the lens ■ Does not require slit lamp ■ The pt is in a supine position under general anesthesia ■ Useful for infantile glaucoma surgeries or MIGS ○ Indirect view types: ■ Goldmann 4 ● Has 4 thumbnail mirrors ● Observes iridocorneal angle ● Comes with and without a flange ○ Back of lens = corneal curvature ● Tears can serve as a fluid bridge ● Mirrors are at a 64 deg angle ○ You don't need to rotate as much ■ Goldmann 3 (we use this one for NBEO) ● Composed of 3 different mirror ● Image of fundus is erect and virtual ● Indirect view of the angle ● Only the “thumbnail” mirror is used to observe ant change angle ○ The other mirrors are used for retinal evaluation ● CL diameter can be between 13 mm - 20 mm ● Lens “anatomy” ○ Central lens (view 1): upright view of 30 deg of the post pole ○ Equatorial mirror (view 2): visualization from 30 deg to the equator ○ ○ ■ ■ ● ● ■ Largest ■ Oblong/trapezoid shape Peripheral mirror (view 3): visualization b/w equator and ora serrata ■ Mid sized ■ Square shaped Gonioscopy/Semilunar mirror (view 4): visualizing extreme retinal periphery and pars plana ■ “thumbnail” ■ Smallest ■ Dome shaped Goldmann 1 Zeiss goniolens ● AKA indentation gonioscopy ● Smallest area of corneal contact ● Angle can be deepened with pressure ● Helps distinguish b/w synechiae and appositional closure ● ○ Indirect view optics: ■ The lens contains mirror(s) that reflect light rays from the angle and exit at a less critical angle ■ Provides mirror image of opposite angle ■ Need slit lamp Procedure: ○ Disinfect ■ Opticide for 3 min & rinse really well ■ DO NOT use alcohol ■ CAN use 1:10 bleach ■ CAN use soap and water ○ Fill concave surface with celluvisc or goniosol ■ NO bubbles ○ Install anesthetic ○ Adjust pt with the slit lamp ■ Adjust oculars ■ Adjust chair/chinrest/oculars/etc ■ Low mag ■ No filters ■ Medium parallelepiped ■ Illumination arm at 0 deg ○ Hold lens with your thumb and index finger ■ “Thumbnail” mirror should be in the 12 o'clock position ○ With opposite hand, hold upper lid onto the roof of the orbit ○ Pull down lower lid as well ○ Insert lower edge of lens into the lower cul-de-sac ○ Rock lens toward pt eye ○ Have pt slowly look straight toward the examiner ○ DO NOT push lens forward against pt cornea Observation and evaluation: ○ Start with inferior angle ■ ● Remember everything is opposite so your lens will be placed superiorly but you will be getting a view of the inferior angle ■ Usually the most pigmented ● Why? ○ ~gravity~ ○ While looking outside of the oculars place vertical slit beam in gonio mirror at 12 o’clock position ■ Focus angle structures ■ Increase mag to enhance view once structures have been identified ● If you can't identify the structure, narrow the bean and inc angle of illumination to 20 deg ● You should be able to then identify Schwalbe’s Line ○ 2 focal lines along the corneal dome which merge into one line at SL ○ If there is glare you can move illumination arm by 5-10 deg ○ Rotate the mirror to view all angles ■ Better to use one hand to rotate ■ 4 mirror lens doesn't need rotation for S,N,I,T but does need a little bit for oblique angles ○ Orient beam horizontally for nasal and temporal ○ Orient beam vertically for superior and inferior ○ Evaluate 360 deg of the angle ○ Ask pt to look toward mirror to “open” angle ○ Removal: ■ Ask pt to look up or toward their nose ■ Switch hands that you are holding the lens with ■ While holding the lens, put pressure on the inferior temporal part of the lower lid ● Sclera should indent thus breaking the suction ● NEVER pull lens from cornea ○ If you cannot get it out, rinse with saline solution around the lens and try again ○ If that fails, call the clinician, but keep calm ■ Clean the gonio lens and rinse pt eye How to record: ○ Draw a large X ■ Each compartment represents a quadrant of the angle ○ Record most posterior angle structure observed in each quadrant ○ Record pigmentation of TB in each quadrant ■ Scale from 0 - +4 ● No pigment - super dense pigment ○ Grade the angle ■ Scheie Grading System (1957) ● Roman numerals describe the degree of angle closure ○ Wide open: all structures visible ○ Grade I: Iris root visible ○ Grade II: CB obscured ○ Grade III: Posterior trabeculum obscured ○ Grade IV: only SL visible ■ Shaffer System (1960) ● Estimate angle width of peripheral iris insertion at TM ○ Grade 4: wide open (45-35 deg) ○ Grade 3: wide open (35-20 deg) ■ ■ ○ Grade 2: narrow (20 deg) ○ Grade 1: extremely narrow (<10 deg) ○ Slit: narrowed to slit (0 deg) Becker (1972) ● Combines examiners estimation of A/C angle’s width with the height of iris insertion Spaeth Grading System (1971) ● Uses 3 separate descriptors ○ Iris insertion:most posterior structure visible ○ Angular approach of the iris: from 0-10 deg ○ Peripheral iris contour: iris contour ● See Spaeth Grading Table in notes Iris Configuration ● Document as steep/convex, regular/flat, or concave ● Iris should appear slightly convex or flat ● Hyperopes may show a higher degree of convexity ● Concave structure may be seen in patients with pigment dispersion syndrome or if the pt is a myope ● Plateau iris may appear as an open A/C but in the gonio lens drapes over the CB making the iris look like a sine wave or double hump ○ This is PCAG ○ The CB obstructs the TM ○ More common in younger pts ○ Treatment: ■ Laser peripheral iridotomy ● Iris Bombe causes a pupillary block ○ The center of A/C is relatively deep and midperiphery is bowed forward Pathological findings in Gonio ● Peripheral anterior synechiae (PAS) ○ Adhesion of the iris to the TM ○ Seen in: ■ Primary Angle Closure Glaucoma (PACG) ■ Chronic Anterior Uveitis ■ Iridocorneal Endothelial Syndrome (ICE) ● Neovascularization Peripheral Anterior Synechiae ○ Seen in ■ NVG ■ Fuch’s Heterochromic Cyclitis ● Asymmetry in iris color ○ Typically with mild iritis in the eye with the lighter colored eyes ○ Patients can have fine vessels crossing to the TM that are susceptible to rupture with trauma and produces hyphema ■ Chronic Uveitis ■ Sturge Weber Syndrome ■ Posterior Pole Vascular Conditions ● DM ● CVO ● OIS ● Radiation ■ Common causes: Neovascularization ● ● ● ● Proliferative Diabetic Retinopathy CRVO Ocular Ischemia Hyperpigmentation ○ Pigmentary Dispersion Syndrome (PDS) ○ Pseudoexfoliation Syndrome ○ Pseudophakic Pigmentary Dispersion ○ Anterior Uveitis ○ Iris Melanoma ○ Nevus of Ota ○ Blunt Trauma ○ AACG ○ Post-YAG Iridotomy ● Trauma ○ Angle recession ■ Rupture of CB face ● Results in tear b/w the longitudinal and circular muscle fibers of CB ■ Common manifestation of blunt ocular trauma ○ Iridodialysis ■ Tear in root of iris ○ Trabecular Dialysis ○ TM Damage ■ Tear of the anterior TM creating a flap hinged in the SS Cyclodialysis with fresh hemorrhage ○ Cyclodialysis ■ Separation of CB from SS ○ Foreign Body (FB) ● Blood in Schlemm’s Canal ○ Seen in: ■ Cavernous Carotid Fistula (CCF) ■ Sturge-Weber Syndrome ■ Superior Vena Cava Obstruction ■ Physiological Variant ○ May present as normal reflux into Schlemm’s Canal and may be seen during routine gonio ○ More commonly blood in the canal is seen under conditions of elevated episcleral venous pressure ■ Always correlated with dilated episcleral vessels ○ Hypotony may also cause blood to reflux into the canal Pearls ● Gonio must always be performed if a VH angle is less than or equal to grade 2 ● Having very deep angles (more than 4) is also suspicious and should warrant gonio ○ Van Herick Grading ■ Grade 4: angle is wide open ■ Grade 3: angle is narrow ■ Grade 2: angle is dangerously narrow ■ Grade 1: very dangerously narrow or closed