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Ophthalmology > Day 6 (2): Slit-Lamp Biomicroscopy > Flashcards

Day 6 (2): Slit-Lamp Biomicroscopy Flashcards

1
Q

What is a Slit Lamp Biomicroscope

A
  • Stereoscopic biomicroscope that emits a focused beam of light with variable height, width, and angle.
  • Gold standard in 3D visualization and measurement of the fine anatomy of the adnexa and anterior segment
  • Using hand-held lenses, posterior segment may be visualized as well
  • Advantages:
    1. excellent image quality
    2. stereoscopic image (depth perception due to binocularity)
    3. adjustable illumination and magnification
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2
Q

Indications for use of the slit-lamp.

A
  • Examination of the anterior eye segment (adnexa to the anterior vitreous): most common indication
  • Contact lens fitting
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3
Q

Other tests that can be performed in tandem with slit lamp examination.

A
  1. Gonioscopy: to visualize iridocorneal angle
  2. Fundoscopy: to visualize posterior segment
  3. Ocular photography
  4. Goldmann applanation tonometry
  5. Laser photocoagulation
  6. Test for ocular surface assessment (Schirmer’s, Fluorescein tests)
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4
Q

Four main parts of a slit-lamp biomicroscope

A
  1. Base
  2. Patient Support Frame
  3. Illumination Arm (on swivel): the slit-lamp part
  4. Viewing Arm (on swivel): the biomicroscope part
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5
Q

What are the parts of the slit lamp base?

A
  1. Adjustable table
  2. Power switch
  3. Intensity rheostat
  4. Locking carriage (for coarse X-Y plane)
  5. Joystick (for fine X-Y, as well as Z)
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6
Q

What are the parts of the patient support frame?

A
  1. Forehead band
  2. Chin rest
  3. Chin height adjustment knob
  4. Patient handles
  5. Canthus height indicator
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7
Q

What are the parts of the Illumination Arm?

A
  1. Light source
  2. Illumination filters
  3. Beam height adjustment
  4. Slit illuminator
  5. Beam width adjustment
  6. Center screw
  • To change slit size and shape, filters/light color and brightness
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8
Q

What are the parts of the Viewing Arm?

A
  1. Oculars/eyepieces with adjustable focus

2. Magnification control knob

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9
Q

Describe the relationship between the illumination arm and the viewing arm.

A
  • COPIVOTAL: mechanically coupled around a central pivot point
  • PARFOCAL: convergence point of the light beam coincides with the focal point of the microscope.
  • ISOCENTRIC: always central regardless of angle
  • Both can swing independently 180 degrees along the horizontal
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10
Q

Two basic models of the slit lamp biomicroscope?

A

Haag-Streit Type

Zeiss Type

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11
Q

Characteristics of a good SLB?

A
  1. Adequate working distance between microscope and eye
  2. Adaptable to different users
  3. Good resolution
  4. Good depth of image
  5. Wide range of magnifications
  6. Wide breath shield
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12
Q

What are the different magnifications available in the SLB?

A
  • Wide range of available magnifications
  • Lower: general assessment and orientation
  • Higher: detailed inspections of areas of interest
  • Methods:
    1. Littmann-Galilean telescope: most common
    2. Zoom Systems: high-end models (7x - 40x)
    3. Changing eyepieces or objective lenses: obsolete
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13
Q

What are the different parameters of the slit light?

A
  1. Width: 0 - 14 mm
    - light source starts out as round and slit can be adjusted to become rectangular
    - graduated for measurements
    - narrow: slices through cornea to determine depth or thickness
    - wide: inspect surfaces
  2. Height: adjustable or fixed
    - graduated for measurements
    - long: structures in anterior to pupil
    - short: passes into pupil to view structures posterior to pupil; assess clarity of anterior chamber (cells and flare)
  3. Orientation: rotate lamp housing
  4. Filters
    - Diffuser
    - Polarizing
    - Red-free
    - Cobalt blue
    - Wratten: for contact lens fitting
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14
Q

What are the different methods of illumination and views that can be done with a SLB?

A
  1. Direct Illumination
  2. Indirect Illumination
  3. Retro-Illumination (Iris or Fundus)
  4. Sclerotic Scatter
  5. Specular View (Specular Microscopy)
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15
Q

What is Direct Illumination?

A
  • Both light source and microscope are pointed at the object of interest
  • Slit width determines the parts of the eye visualized
  • Classified according to the width of the slit:
    1. Diffuse Beam: general inspection of the eye
    2. Wide Beam: broad view of the surface
    3. Parallelepiped Beam
  • Wide: broad view of the surface
  • Narrow: balanced view of surface with depth
    4. Optical Section: cut section for thickness and depth
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16
Q

What is the importance of the angle between the viewing arm and the illumination arm?

A
  • Graduated scale is located at the pivot point of the two arms
  • As the angle between the two arms increases, depth is better assessed and less of the surface is seen.
  • 5 degrees: surface only
  • 45 degrees: balanced view (surface + depth)
  • 85 degrees: depth/thickness only

Wider angles

  • visualize deeper layers without interference from reflection of anterior layers
  • assess depth or thickness
  • assess texture or smoothness or corneal surface
  • wider the beam = greater the angle needed to see posterior layers
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17
Q

What is the Diffuse beam or Wide beam used for?

A
  • General inspection of the eye and adnexa
  • Color assessment of the iris
  • Contact lens fitting
  • Disadvantage: brightness is poorly tolerated
  • Settings:
    1. Wide slit
    2. Diffusing filter
    3. Angle: 30-50 degrees
    4. Magnification: 6-10X
18
Q

What is the Parallelepiped beam used for?

A
  • Default method for corneal inspection
  • Block of tissue is displayed in 3D showing a balanced view with both surface characteristics and depth
  • Settings:
    1. Slit: 2 mm
    2. Angle: 30-50 degrees
    4. Magnification: 10-25X
19
Q

What is the Optical Section used for?

A
  • Detailed assessment of depth and thickness
  • Surface characteristics not in view
  • Settings:
    1. High illumination in a dark room
    2. Narrowest slit: 0.1 - 0.2 mm
    3. Angle: largest possible (80-90 degrees)
    4. Magnification: 10-25X
  • Structures seen:
    1. Corneal layers
    2. Anterior chamber
    3. Iris
20
Q

What is Indirect Illumination?

A
  • Target structure is illuminated indirectly by reflections or scattered light from an object to which the light source is directed to
  • Light is internally reflected within the cornea or reflected by surrounding tissues
  • Similar to how the light given off by the moon is just a reflection of the light from the sun
  • Indications:
    1. Subtle findings: obscured by intense illumination
    2. Opacities: scatter light so best viewed against a dark background
  • Settings: BRIGHT object, DARK background
    1. Medium slit: 2 - 4 mm
    2. Angle: medium to wide (30 - 50 degrees)
    3. Magnification: medium to high if subtle
21
Q

What is Retro-Illumination?

A

Appearance: DARK object, BRIGHT background
- best for assessing keratic precipitates on the posterior surface of the cornea

Iris Retro-Illumination: illuminates cornea

  1. Narrow to moderate width and LONG slit
  2. Angle: wide (80 - 90 degrees)
    - if high magnification warranted: may need to remove parfocality by decoupling viewing and illumination arms
  3. Magnification: depending on target object size

Fundus Retro-Illumination: illuminates cornea and lens

  • pupil dilation is warranted
    1. Narrow to moderate width and SHORT slit (to fit into pupil)
    2. Angle: narrow (0 - 10 degrees) because target is pupil
    3. Magnification: moderate
22
Q

What is Sclerotic Scatter view?

A

Principle: total internal reflection of light through the cornea
Target: lesions in the corneal stroma

  1. Intense illumination
  2. Arms are decoupled:
    - Viewing Arm: center of cornea
    - Illumination Arm: 45 degrees from center directed into the limbus
  3. Magnification: depending on target object size
23
Q

What is Specular Reflection or Specular Microscopy?

A

Assessment of the corneal endothelium

  • Cell density
  • Cell size variation (polymegathism)
  • Cell shape variation (pleomorphism)

Settings:

  1. Medium slit
  2. Angle: wide (80 - 90 degrees)
  3. Magnification: high
24
Q

What slit width and length is used to view anterior chamber reactions (cells and flare)?

A

Narrow and short slit

25
Q

What are the steps in proper positioning of the patient when doing SLB?

A
  1. Thoroughly clean with alcohol the forehead band, chin rest and handles.
  2. Position base table so pt can sit upright comfortably:
    - Forehead against the band: ensures eye is within the focal range of the slit lamp
    - Chin against the rest
    - Hands grasping the handles
    - Must be maintained throughout the exam so ensure both patient and examiner are comfortable.
  3. Adjust own chair to reach eyepieces. If with large height difference, may adjust patient’s chair.
  4. Adjust eyepieces to fit own interpupillary distance.
  5. If wearing corrective lenses or do not require correction, twist eyepieces to plano. Otherwise, enter prescription in the eyepiece.
  6. Turn the chin height adjustment knob until lateral canthus is aligned with the canthal indicator.
  7. If limitations make standard slit lamp positioning difficult, handheld slit lamp can be used.
26
Q

Reminders to the operator when conducting the SLB.

A

Dominant hand: joystick and carriage
Non-dominant hand: slit width adjustment knob
- allows for fast adjustment of the slit beam width and arms angle by swiveling the illumination arm

Convention: examine RIGHT eye first

27
Q

Steps in proper focusing of the SLB.

A
  1. Unlock the carriage and turn on the power switch.
  2. Course focusing:
    - aim light beam toward a point on the skin such as the nose or cheek
    - avoid directing beam into the pupil (uncomfortable)
    - slowly slide the carriage forward toward the patient
  3. As illuminated area comes into focus, maintain the joystick in an upright position to preserve the full range of fine back-and-forth control.
  4. Adjust vertical position of beam and field of view:
    - upward: turn joystick clockwise
    - downward: turn joystick counterclockwise
28
Q

How to adjust the illumination arm of the SLB?

A
  1. Illumination arm sits on a swivel
    - beam can be directed from any direction in the horizontal plane 90° nasal and temporal to the microscope focal point.
  2. Light intensity
    - adjust rheostat or intensity steps in the power switch
    - provide just enough light for examination
    - high intensity: uncomfortable esp. if pupils dilated
    - neutral density filter: to reduce light intensity
  3. Beam width:
    - turn knob at the base of the illumination arm
    - assess depth and thickness of cornea, AC and lens
    - evaluating opacifications in these media
  4. Beam height:
    - turn knob on the light source near the top of the lamp
  5. Beam orientation:
    - adjusted through 12 clock-hours by turning the light source relative to the illuminator arm
  6. Taking measurements using beam height and width:
    - graduated so the dimensions of the beam can be read off the knobs in millimeters
  7. Filters:
    - switch is above the knob that controls beam height
    - red-free (green): visualization of blood
    - cobalt-blue: visualization of fluorescein
    - neutral-density: for fundoscopy
    - diffuser: swung up in front of the slit beam mirror for unfocused illumination and wide-field examination of the adnexa, ocular surface and ocular photography
29
Q

How is the SLB magnification adjusted?

A
  • Control knob: near the eyepieces
  • Stepwise magnification: between 6X and 40X.
  • Low power (6 - 10X): wide field for general exam
  • High power (10 - 40X): detailed examination of pathologic features identified at low power
30
Q

Reminders in doing decoupling/decentering of the illumination arm and viewing arm.

A

Center screw

  • for adjustment of the convergence point of the light beam independent of the microscopic focal point.
  • results in decentering or decoupling: loss of the parfocality between illumination and viewing arms
  • undesirable for most exams and avoided
  • can be useful to improve retroillumination or accentuate sclerotic scatter
31
Q

Quick guide in doing slit lamp examination

A
  1. Plug-in slit lamp
  2. Clean forehead, chin rest and handles
  3. Bring table into position in front of the patient
  4. Adjust chin height to position eyes at the level of the black indicator line (canthal indicator) with head resting on forehead band
  5. Instruct patient to hold the handlebars
  6. Set oculars at “0/plano” and adjust interpupillary distance like binoculars
  7. Unlock the carriage
  8. Course focusing: move entire carriage forward and backward at the base
  9. Fine focusing: move joystick into position
    - clockwise: to raise
    - counterclockwise: to lower
  10. Turn power switch on
  11. Adjust beam width and intensity
  12. Apply correct filter:
    - white light/neutral density: general exam
    - cobalt-blue: fluorescein exam
  13. Adjust the beam height
  14. Adjust beam angle:
    - swivel illumination arm while grasping width knob
  15. Once done, lock the carriage in place and turn off power switch
32
Q

Quick guide in anterior segment examination.

A
  • Done systematically in 8 stages:
  1. External Structures and Adnexa
  2. Lids and Lashes
  3. Conjunctiva and Sclera
  4. Cornea
  5. Anterior Chamber
  6. Iris and Pupil
  7. Lens
  8. Anterior Vitreous
33
Q

Examination of external structures and adnexa.

A
  1. Gross examination of the eyes and orbit
    - asymmetry in the eyes or adnexa
    - masses or ulcerations: basal or squamous cell CA
  2. Slit-Lamp Exam:
    - Illumination: Low
    - Magnification: Low
    - Thickness: Moderate
    - Angle: viewing arm oriented directly in front of the patient while illumination arm at 30-60° angle
    - Examine periorbital structures:
    + inflammation/erythema/irritation
    + lesions
34
Q

Examination of the lids and lashes.

A
  1. Lid apposition:
    - examine closed and opened
    - look for:
    + lagophthalmos
    + ectropion
    + entropion
    + blepharitis
    + signs of trauma
  2. Eyelid margin
    - inferior margin: reflected using cotton-tipped applicator to visualize follicles, punctum, and meibomian glands
    - edema
    - hordeolum
    - chalazion
    - masses
  3. Eyelashes
    - trichiasis
    - signs of blepharitis: scurf, collarettes
35
Q

Examination of conjunctiva and sclera.

A

Conjunctiva: both bulbar and palpebral conjunctiva

  • Upper fornix: reflect the tarsal plate by instructing the patient to look down, applying traction to several lashes to pull the upper lid away from the eye, and simultaneously pressing down on the tarsal plate with a cotton-tipped applicator while drawing the eyelid up
  • Lower fornix: retract lower lid and ask pt to look up
  • irritation/injection/erythema
  • foreign bodies or retained debris
  • masses

Sclera

  • color
  • injection
  • ciliary flush: violaceous injection more prominent around the limbus suggesting anterior uveitis.
36
Q

Examination of the cornea.

A

Settings:

  • Illumination: Moderate
  • Magnification: Low (general exam), High (detailed)
  • Thickness: Narrow
  • Angle: viewing arm in front of the patient while illumination arm at 70-90° angle
  • Produces an optical cross section of the cornea
General Exam:
- Slow sweep of the illumination arm from temporal to nasal with fine adjustment of joystick backward until beam reaches the vertical meridian and then forward again to maintain focus. 
\+ irregularities in thickness
\+ transparency
\+ presence of pathology
  • Location of pathology: based on their proximity to the illumination source, with SUPERFICIAL layers CLOSEST to the light source
    + Mucous strands (DED): ocular surface, closest to light source in optical section.
    + Keratic precipitates: endothelium; farthest from light source

Detailed Exam:

  • direct observation of characteristics of the pathology
  • high magnification + oblique angle: determine cross-sectional location of pathology
37
Q

Examination of the anterior chamber.

A

Settings:

  • Width: Narrow (1 mm)
  • Height: Short (3 mm)

Findings:

  • Normal: clear and transparent
  • Pathologic: any reflective material
  1. Hyphema: blood in the AC (esp. dependent portion)
    - Trauma
    - Neovascularization of iris
  2. Microhyphema: individual RBC in AC
    - Red-free filter: black spots against red reflex
  3. Hypopyon: purulent material in AC (dependent area)
    - Infection or inflammation
  4. Cells and Flare in AC
    - Inflammation, especially anterior uveitis,
    - Cell: individual leukocytes floating in AH
    - Flare: proteinaceous material turning AH turbid and hazy and making beam more visible
    - Instruct pt to rapidly saccade L and R several times to agitate the AH, making findings more apparent.

AC Depth:

  • painful red eye: AACG suspect
  • physiologically narrow angle: glaucoma predisposition

Van Herick technique
- Beam toward corneal periphery (angle: 60°)
- Note distance from the inner corneal surface to iris:
+ < 1/4 of corneal thickness: shallow
+ Peripheral contact: adhesion between the iris root and the cornea = angle closure
- Done prior to installation of dilating drops to avoid precipitating acute angle closure

38
Q

Examination of the iris and pupil.

A

Direct Illumination: iris surface and pupillary margin

  • irregularities in pigmentation
  • raised lesions
  • asymmetry
  1. Pupillary Ruff
    - small amount of hyperpigmented iris at the pupil margin in myosis
    - normal finding
  2. Rubeosis Iridis
    - neovascularization of the iris
    - irregular vessels first appear at pupil margin/iris root
    - indication of advanced ocular disease

Retroillumination

  • short, narrow beam shone directly THROUGH the pupil and reflected off the retina
  • transillumination defects: loss of pigmentation in the posterior iris due to inflammation or trauma

Ocular Albinism: diffuse transillumination of the iris

39
Q

Examination of the lens.

A
  • Best examined with pupils dilated
  • Location and transparency may be ascertained even without dilation
  • Parts: distinguished in optical sections using a narrow beam
    1. Capsule: outermost
    2. Cortex:
    3. Nucleus: innermost

Systemic Connective Tissues Disease

  • Marfan syndrome
  • Bilateral dislocation of the lens in the absence of significant trauma due to weakness of the zonules

Cataracts
- provides information on the anatomical location of opacities indicative of etiology

  1. Anterior Capsular
    - advanced age
    - diabetes
    - acute angle closure glaucoma
    + Glaukomflecken: grayish opaque spots on the anterior cortex
  2. Cortical
  3. Nuclear Sclerosis
    - most common cause of age-related cataract
    - progressive discoloration (hazy-white to yellow to brown) with increasing density
  4. Posterior Subcapsular
    - retroillumination against the retinal reflex
    - corticosteroid use
    - prior uveitis

Pseudophakia: presence of prosthetic IOL

  • check for proper placement in the visual axis
  • subluxation
40
Q

Examination of anterior vitreous.

A
  • A restricted region of the vitreous immediately behind the lens
  • Cell and flare: inflammatory infiltrates from iridocyclitis
  • “Tobacco dust” pigmented cells: do dilated fundoscopic exam to assess peripheral retina
    + retinal tear
    + retinal detachment
    + vitreous hemorrhage
41
Q

How to do fluorescein tests?

A

Fluorescein

  • adheres to the basement membrane of epithelium
  • cobalt blue filter: emits yellow light
  • via drops or impregnated strips

Pathologies:

  1. Corneal abrasions from trauma
  2. Ulcerations (infectious)
  3. Dendritic lesions (herpes keratitis)

Ophthalmology (44 decks)

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