Midterm 1 Flashcards
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.
Patient positioning issues
Obes or top heavy patients, lower instrument and ask patient to lean forward more. Wheelchair bound patients, watch arm rests, may need assistance with positioning patient.
Binocular indirect ophthalmoscopy
Allows use of both eyes to view fundus yielding stereopsis, light is reflected off retina and converged by condensing lens held in front of patients eye, BIO requires illumination and viewing systems, Bulb/light source is mounted within headset, viewing system of headset is a mirror, oculars, and prisms (prisms allow interpupillary distance to examiner to be set)
View with BIO
Real, arial, inverted and reversed image. Stereoscopic view of fundus, wide field (>40 degrees)
Instrumentation Characteristics
Head mount or spectacle mount (on glasses), Power supply (wired or wireless), digital, ease of use, optics (illumination). Interpupillary distance is optically fixed by the BIO design
Filters on the BIO
Yellow, red-free (green), cobalt blue
BIO condensing lenses
Lower power: +12D to +16D, posterior pole and optic disk evaluation. Medium power: +18D tp +25D. Higher power: +30D to +40D, poor dilation, media opacities. +20D, standard lens, focal length 1/20=0.05m=5cm. Image mag: 2.93x, Field of view= 46 degrees (about 9 disc diameters)
Relationships between lenses
Decrease condensing lens power: increasing mag, decreasing field of view, increasing working distance.
BIO lens characteristics
Aspheric lenses, always hold the most curved surface toward you (position silver ring toward patient), Multi-layered ARC reduces reflections, increases light transmission through the lens.
Clinical indications for pupil dilation
As part of routine examination: older patients, have a higher risk of disease, high risk medications.
Symptomatic patients: +flashes/floaters
Unexplained loss of vision or color perception
Analysis for possibility of retinal disease
Trauma
Post-op cataract patients
Systemic vascular conditions (ex. HTN)
Follow-up on existing retinal disease
Patient education on pupil dilation
Why? To evaluate peripheral fundus (retinal tears/detachments, infections/inflammation, neoplasm, etc.) To evaluate the lens for cataract.
What? Using a lens close to face to magnify the image, bright light to view the retina, if reclining the patient, inform them, do not dim lights too much.
Risk of damage from BIO light
Half-voltage settings: >40 seconds continuously before damage can occur. Retinal disease: lower tolerance to light, less exposure. Possible effect on migraine sufferers/epileptic patients (bright light can precipitate conditions)
Comprehensive medical eye evaluation for adults with no risk factors
65+: every 1-2 years
40-64: Every 2-4 years
30-39: at least twice in these years
20-29: at least once in these years
Definition of at risk adult
Patients with diabetes, hypertension
Family history of ocular disease
Clinical findings that increase their potential risk: working in occupations that are highly demanding visually or are eye hazardous, taking prescription or nonprescription drugs with ocular side effects
Those wearing contact lenses
Those who have had eye surgery
Those with other health concerns or conditions
AOA pediatric recommendations
Birth-24 mos: 6 mos.
2-5yrs: 3 years
6-18 yrs: Before 1st grade and every 2 yrs after.
At risk: as needed before 6, after 6 every years
Definition of at risk child
Prematurity, low birth weight, oxygen at birth, grade 3 or 4 intraventricular hemorrhage, family history of retinoblastoma, congenital cataracts, or metabolic or genetic conditions, infection of mother during pregnancy, difficult or assisted labor, which may be associated with fetal distress or low APGAR scores, high refractive error, strabismus, anisometropia, known or suspected CNS dysfunction
Peripheral retinal landmarks
Nasal Ora Serrata, Temporal Ora Serrata, Vortex vein ampullae, short ciliary nerves, long ciliary nerve, Pars plana, equator
