Sli Lampst Flashcards
Slit lamp used to do what
grading, fluoroscein staining and lid eversion: assess bulbar hyperaemia, limbal hyperaemia, palpebral redness, lid redness and lid roughness. Assess adnexa, external eye, and meibomian glands. Ocular safety.
Baseline measurements to evaluate change. Contact lens fit. Medico-legal.
Diffuse what and uses
diffuser filter to improve px comfort, low magnification wide angle beam. Illumination is spread evenly over anterior surface= external eye and adnexa
General eye and adnexa, nasal to temporal side eyelid
USES- lashes bulbar conjunctiva iris pupil and then contact lens if in place. And then lower lid and lashes.
Direct focal illumination 3 types and uses
Direct focal illumination- 3 types: optic section, parallelpiped, conic beam
Optic section- low to high mag, thin beam, 60 degrees angle
USES for depth of AC, localise nerve fibres, blood vessels, infiltrates and cataracts
Parallelpiped- we can track a nerve for eg
low to high mag, broad beam, angle 45-60 degrees, USES view cornea, nerve fibres, punctate keratitis.
Conical beam- medium mag, very small circular beam, 45-60 angle, dark room pupil acts as dark background, USES to view inflammatory cells and flare in AC. So tyndall effect.
Indirect and retro
Indirect- looking to side of beam as direct beam may bleach defects from view decoupled
can view limbal vessels and corneal tissue changes and
epithelial vehicles, epithelial erosions, iris pathology, iris sphincter
Retro- Start coupled and get into focus then decouple.
Moderately wide beam and medium to high mag
Uses the iris or fundus to retro illuminate the cornea, so the area of interest is illuminated by light behind the structure
Useful to view structures that would be bleached by direct.
USES– microcysts (exhibit reversed illumination) vacuoles (lack of oxygen to cornea) crystalline lens opacities eg cataracts, contact lens deposits and vascularisation.
Sclerotic scatter
illumination slit is 1-1.5mm located on limbus, low magnification, can be direct or indirect, decoupled, thin beam.
On limbus, leads to total internal reflection, if any opacities or swelling then total internal reflection lost. Observation system decoupled and focussed on cornea, halo in darkened room.
USES- corneal opacities, corneal oedema or foreign bodies, scars etc
Specular reflection
angle of incidence= angle of illumination so both systems must be at the same angle to each other, medium to high mag, reduce angle for deeper structures. Coupled
We get purkinje images= reflections from each structure of eye:
Purkinje image 1- the front surface of the tear film and tears can be seen moving just to the side of the bright reflection after a blink
Purkinje 2- the endothelium. Mosaic hexagonal cells under 40 times mag in the dimmer reflection
Purkinje 3- Front surface of the lens. Dimpled appearance can be seen with quite a narrow angle between observation and illumination system. Orange peel effect in old people and normal people like a golf ball.
Move illumination until image seen, focus on area of interest and swing illumination beam until specular reflection achieved- coupled technique
Only visible through one eyepiece at a time angle cannot be matched to both observation systems, reduce angle= deeper structures
USES- tear film debris and flow tear film break up time, endothelium under high mag, crystalline lens orange peel texture in old people seen when angle reduced.
Tangential
coupled, low mag, narrow beam, wide angle perpendicular to iris so illumination structures almost at right angles to structures of interest.
Observation system focused on structure of interest. So parallel to iris and observed along the visual axis.
Highlight tumours, raised lesions, difficult to support head right, naevi
USES- iris freckles, tumours, general integrity of cornea and iris
exam q
Exam questions- list the biomicroscopy illumination techniques and a condition they are optimal for (11 marks)
diffuse- overview
direct- optic section for depth, parallelpiped for corneal nerves in keratoconus, conic beam for uveitis
indirect- retro for microcysts or vacuoles and sclerotic scatter for oedema
specular reflection- 1 for tear film deficiency, 2 for endothelial blebs, 3 for lens pigmentation
Tangential- iris tumours
Indications for a slit lamp examination
Conjunctival injection
Lacrimation or itchiness or grittiness
Dry eyes
Haloes around lights
Narrow anterior angle
Recent foreign body sensation
Contact lens wearer
Unexplained visual acuity loss
Lens opacities
Irregular pupil margins
Increased iop
