Midterm 1 Flashcards
(101 cards)
Biomicroscope (Slit lamp)
Primary evaluating tool of the anterior segment of the eye. Two combined systems: Illumination system and observation system.
Slit lamp illumination system: 2 types
With focusable beam with well-defined edges. Filters to enhance view or exam. It works on Vogt (Kohler) illumination principle: produces homogeneous slit beam and prevents disruption of light beam on ocular surface. Haag streit type (vertical illumination system with bulb at top of tower); Zeiss type (round housing unit at middle of instrument with bulb encased, most common at SCO)
Slit lamp observation system
High-resolution microscope with variable magnification, eyepieces and objective lenses.
Slit lamp Magnification System: 3 types
Contains convergent or parallel eyepieces. Many objective lenses create a wide range of magnification levels. Grenough/Flip-type; Galilean rotating barrel (switches mag, ones used in clinic); Zoom.
Slit lamp design
Magnification system, Illumination system, Light intensity, joystick, and lock, power on/off. Chin adjustment (align outer canthus with the line on the slitlamp bar)
Patient Education on Slip lamp
Why are you performing the test: to examine health of the eye. Remind them to keep their forehead against the forehead rest, chin on the chin rest and keep mouth closed
Slit length and width
Continuous, fixed-width and height
Filters on slit lamp
Neutral density, yellow, cobalt blue, red free
Alignment of Microscope and Light, parfocality
The point at which the microscope is focused corresponds to the point on which the light is focused, this coupling effect is called parfocality. This is achieved by the microscope and the illumination system, having a common focal plane and their common axis of rotation also lies in that focal plane.
Slitlamp filters
Diffuser: used for general, nonfocal illumination, used for anterior segment photography. Used to observe large gross areas of eye on low magnification
Cobalt Blue: used in fluorescent exams as exciter filter, terms yellow dye bright green.
Red-free (green): Used to enhance contrast between blood vessels and their surroundings
Neutral density: Allow larger slit widths without increase in brightness
Yellow: Used for increased patient comfort during the exam, optional filter
Variations of normal on Cornea
Arcus Senilis: Cholesterol deposition in the subepithelial/basement membrane area
Limbal Girdle of Vogt: aging bilateral degeneration
Types of beams
Direct focal illumination: Parallelepiped, Specular reflection, Narrow beam/Optic section Sclerotic scatter Direct retroillumination of iris Indirect retroillumination of retina Conical section
Direct focal illumination: Parallelepiped
45-60 degree angle/displacement, 2 mm beam width, Low to moderate magnification, full beam height, low to moderate illumination.
Corneal epithelial scan, lashes, lid margins (meibomian gland orifices), Conjunctiva (bulbar and palpebral), iris, crystalline lens evaluation
Specular reflection
Angle of illumination= angle of reflection, observation and illumination system have same angle with perpendicular axis to each other, the light reflected from the anterior or posterior corneal surface, beam width
Direct illumination: Narrow Beam/Optical section
45-60 degrees, moderate to high illumination, moderate to high magnification, 0.2-0.3 mm narrowest width possible, Full beam height.
Corneal evaluation: corneal edema, thinning, anterior chamber angle estimation (van herick technique), lens evaluation.
van Herick method (anterior chamber evaluation)
Look at the shadow between cornea and iris. Sensitivity: 87%, Specificity: 84%.
Grade 4: width of chamber interval > width of corneal optic section (1:1 ratio, wide open angle)
Grade 3: width of chamber interval is 1/2 the width of corneal optic section (1:1/2 ratio, unlikely to close)
Grade 2: width of chamber interval 1/4 width of corneal optic section (1:1/4 ratio, narrow angle and capable of closing)
Grade 1: width of chamber interval
Sclerotic scatter
Angle 60 degrees, light directed toward limbus, indirect illumination, beam width of 1 mm, bean height: max, illumination: moderate, magnification: low, viewed at or outside slit lamp.
Highlights subtle findings on cornea, View central corneal haze: historically seen with wear of PMMA contact lenses, not prevalent today.
Direct retroillumination of iris
60 degrees, when reflected of iris or lens, keep focus on cornea, beam width 1-2 mm, beam height: match pupil height to maximum, illumination high, mag low to high, similar to direct illumination, look at structure beside the beam, use iris as background
Indirect retroillumination of retina
0-5 degrees, light in click position, beam width 1-2 mm, beam height: match pupil height to maximum, illumination high, mag from low to high, Light reflects off retina while focusing on structure in front of it.
Conical section
Direct illumination, circular or short square beam, focus light between cornea and iris surface, evaluates anterior chamber for cells or flare, dark room (examiner has to dark adapt), illumination high, mag high
Tear meniscus
Beam angle: 45-60 degrees, beam width 1-2 mm parallelepiped, beam height max, illumination low to moderate, mag 10-16x.
Meniscus is less than 0.5 mm= tear deficiency, 0.5-1 mm= normal.
Tonometry settings
Cobalt blue filter, 45-60 degrees displacement of light source, 10-16x mag, widest and highest beam, highest illumination level
Gonioscopy settings
White light, vertical parallelepiped 1-3 mm wide beam, moderate illumination, 0 degree displacement (in click position), magnification moderate.
Non contact fundus exam settings
White light, enhancement filters: yellow, neutral density, red free filter, O degree displacement, parallelepiped of moderate width and height, low to medium illumination level, low mag: 10x.
