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Duke Elder 2020 > Investigations > Flashcards

Investigations Flashcards

1
Q

What is keratometry and what is it used for?

A

Used to investigate the cornea

MEASURES ANTERIOR CORNEAL SURFACE CURVATURE

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2
Q

What is corneal topography used for?

A

MEASURES AND QUANTIFIES CURVATURE OF THE WHOLE CORNEA

USES PLACIDO-DISC SYSTEMS WHICH PROJECT CONCENTRIC RINGS OF LIGHT ON THE ANTERIOR CORNEAL SURFACE

INDICATIONS INCLUDE:

KERATOCONUS

ASTIGMATISM

LASER EYE SURGERY

CONTACT LENS FITTING

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3
Q

What is ultrasonic pachymetry?

A

CAN BE USED TO MEASURE THE CENTRAL CORNEAL THICKNESS (cct) USING ULTRAOSNIC PROBE

NORMAL CCT IS BETWEEN 530-545M um

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4
Q

What ocular coherence tomography?

A

USES NEAR INFRARED WAVES THROUGH THE PUPIL TO THE RETINA

PRODUCES CROSS SECTIONAL + 3d IMAGE OF THE RETINA

INDICATED IN ORDER TO DIAGNOSE AND MONITOR PROGRESSION OF MACULAR AND OPTIC DISEASES

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5
Q

What is fluorescence angiography?

A

SODIUM FLUORESENCE (DYE) ABSORBS A BLUE LIGHT (WAVELENGTH 465-490NM) AND EMITS YELLOW LIGHT (530NM)

INJECTED INTO PERIPHERAL VEIN TO CIRCULATE TO THE EYE

PASSES THROUGH SHORT POSTERIOR CILIARY ARTERY INTO THE CHORIOCAPILLARIS 8-12S POST INJECTION

THEN ENTERS RETINAL CIRCULATION

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6
Q

What are some side effects of fluoresence angiography?

A

URINE DISCOLOURATON

NAUSEA

VASOVAGAL SYNCOPE

ANAPHYLAXIS (RARE)

CONTRAINDICATED IF ALLERGIC TO SHELLFISH

FUNDUS CAMERA WITH COBALT BLUE EXCITATION AND YELLOW GREEN BARRIER USED TO CAPTURE IMAGES OF RETINA DURING PASSAGE OF DYE INTO THE POSTERIOR SEGMENT OF THE EYE

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7
Q

What is cyanine green angiography?

A

ICG IS 98% BOUND TO ALBUMIN IN THE PLASMA

LOW PERMEABILITY WHEN PASSING THROUGH CHOROID

USES NEAR-INFRARED LIGHT

THESE FACTORS ALLOW FOR BETTER VISUALISATION OF CHOROID VASCULATURE

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8
Q

When is cyanine green angiography contraindicated?

A

PREGNANCY AND WITH SEAFOOD / IODINE ALLERGIES

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9
Q

What is fundus autofluoresce?

A

NO USE OF DYE

DETECTS LIPOFUSCIN ALREADY PRESENT WITHIN THE RETINAL EPITHELIUM

CAN BE USED IN BEST DISEASE AND MONITORING GEOGRAPHIC ATROPHY

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10
Q

What are electrodiagnostic tests?

A

TESTS ELECTRICAL ACTIVITY OF THE RETINA IN RESPONSE TO A LIGHT STIMULUS

ELECTRO-OCULOGRAM REFLECTS THE ACTIVITY OF PHOTORECEPTORS AND RPE

RETINAL DISEASES PROXIMAL TO PHOTORECEPTORS GIVE NORMAL EOG READINGS

ERG AND EOG MAY BE USEFUL IN DIAGNOSING CONDITIONS SUCH AS BEST DISEASE AND RETINITIS PIGMENTOSA

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11
Q

What is tonometry (glaucoma)?

A

USED TO MEASURE IOP

MOST WIDELY USED: GOLDMANN APPLANTATION TONOMETRY IS THE MOST WIDELY USED

FOLLOWS IMBERT-FICK LAW TO ESTABLISH THE AMOUNT OF FORCE REQUIRED TO FLATTEN A CORNEAL AREA OF 3.06MM IN DIAMETER (ASSUMING CCT OF 520um

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12
Q

What can cause incorrect measurements in tonometry?

A

EXCESSIVE FLUOROSCEIN: OVERESTIMATION OF IOP

LOW OR HIGH CCT: UNDERESTIMATE / OVERESTIMATES IOP RESPECTIVELY

ASTIGMATISM

CALIBRATION ERRORS

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13
Q

What is gonioscopy?

A

USED TO DETERMINE WHETHER IRIDOCORNEAL ANGLE IS OPEN OR CLOSED

VISUALISATION OF ALL STRUCTURES INDICATES A WIDE OPEN ANGLE

INABILITY TO VISUALISE ANY STRUCTURES INDICATES A CLOSED ANGLE

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14
Q

What are the structures (ant–> pos) seen in gonioscopy?

A

SCHWALBE LINE

NONPIGMENTED TRABECULAR MESHWORK

PIGMENTED TRABECULAR MESHWORK:

  • PIGMENTATION NOT PRESENT AT BIRTH
  • INCREASES WITH AGE, USUALLY DURING PUBERTY

SCLERAL SPUR

-ANTERIOR PROTRUSION OF THE SCLERA THAT
MARKS THE ATTACHMENTS OF THE CILIARY BODY’S
LONGITUDINAL FIBRES

CILIARY BODY

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15
Q

What is perimetry?

A

USED TO DETECT VISUAL FIELD DEFECTS AND IS COMMONLY USED IN GLAUCOMA AND NEURO-OPTHALMIC CONDITIONS

EXAMPLES OF PERIMETRY:

HUMPHREY VISUAL FIELD ANALYSIS

GOLDMANN VISUAL FIELD TESTING

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16
Q

What is included in glaucomatous field defects?

A

NASAL STEP

PARACENTRAL DEPRESSION : MOST COMMONLY SUPERONASALLY

ARCUATE DEFECTS: COMBINATION OF PARACENTRAL DEPRESSIONS

RING SCOTOMA: SUPERIOR + INFERIOR ARCUATE DEFECTS

TUNNEL VISION WITH A TEMPORAL SPARING OF VISUAL FIELD

17
Q

What investigations are used in neuro-Opthalmology and orbit?

A

MRI SCANS:
-ARE PRODUCED BY THE ALIGNMENT OF THE
HYDROGEN ATOMS

-USED TO AID IN DIAGNOSIS OF INTRACRNAIAL
LESIONS AFFECTING VISUAL PATHWAY

COMPUTED TOMOGRAPHY:

-SERIES OF X-RAY BEAMS TO FORMA DETAILED
IMAGE OF THE BODY

  • QUICKER THAN MRI SO MORE VALUABLE IN ACUTE
    SETTINGS

INDICATIONS:

ORBITAL FRACTURES

ORBITAL CELLULITIS

THYROID EYE DISEASE

CEREBRAL HAEMORRHAGES

CT ANGIOGRAPHY IS ALSO IMPORTANT TO
INVESTIGATE FOR SUBARACHNOID HAEMORRHAGE
AND INTRACRANIAL ANEURYSMS

18
Q

What properties do all beams from lasers have?

A

COHERENCY (ALL EMITTED PHOTONS ARE IN THE SAME PHASE)

MONOCHROMACITY (SINGLE WAVELENGTH)

COLLIMATION (NARROW WITH MINIMAL DIVERGENCE)

19
Q

What are the three principal parts of all lasers?

A

SOURCE OF ENERGY: LIGHT OR ELECTRICAL

A MEDIUM: CONTAINING ATOMS OR MOLECULES THAT UNDERGO STIMULATED EMISSION AND IS THE MAJOR DETERMINANT OF WAVELENGTH: 
GAS (ARGON, KRYPTON, CARBON DIOXIDE)  
LIQUID (E.G. DYES)  
SOLID (E.G. NEODYMIUM-DOPED YTTRIUM 
   ALUMINIUM GARNET CRYSTALS

OPTICAL RESONATOR THAT USES MIRRORS TO
AMPLIFY LIGHT

20
Q

Where is melanin found and what wavelengths does it absorb?

A

FOUND MAINLY IN RPE AND CHOROID, ABSORBS MOST OF THE VISIBLE SPECTRUM AND INFRARED WAVELENGTHS

21
Q

Where is xanthophyll found and what wavelengths does it absorb?

A

PRESENT AT THE MACULA. ABSORBS BLUE LIGHT (450-495NM)

22
Q

What wavelengths does haemoglobin absorb?

A

ABSORBS BLUE, GREEN (495-570NM) AND YELLOW LIGHT (570-590NM)

23
Q

What is photovaporization?

A

VAPORIZATION OF WATER FROM TISSUES OCCURS IN TYPES OF LASERS SUCH AS CO2 LASERS AS THEY RAISE TEMPERATURE BEYOND 100 DEGREES

24
Q

What is photocoagulation?

A

ABSOPRTION OF LASER EMISSION BY TISSUES CAUSES A RISE IN TEMPERATURE LEADING TO PROTEIN DENATURATION E.G. PANRETINAL PHOTOCOAGULATION USED IN DIABETES

25
Q

How do photocoagulative lasers work?

A

ARGON BLUE-GREEN – ABSORBED BY MELANIN, HAEMOGLOBIN AND XANTHOPHYLL TF. NOT USED ON MACULA

KRYPTON RED (647NM): ABSORBED BY MELANIN

FREQUENCY DOUBLED Nd:YAG (532NM): ABSORBED BY HAEMOGLOBIN AND MELANIN IN THE RPE AND TRABECULAR MESHWORK

DIODE (810nm): EMITS NEAR-INFRARED RADIATION AND IS ABSORBED BY MELANIN

26
Q

How do photochemical lasers work?

A

WORK BY BREAKING CHEMICAL BONDS THAT HOLD TISSUE TOGETHER USING ULTRAVIOLET LIGHT (PHOTOABLATION) E.G. EXCIMER LASER:

PHOTOREFRACTIVE KERATECTOMY: CORNEAL EPITHELIUM IS FIRST REMOVED THEN ABLATION USED TO RESHAPE THE CORNEA

LASER ASSISTED IN SITU KERATOMILEUSIS (LASIK): CORNEAL FLAP IS CREATED, STROMA IS THEN ABLATED TO RESHAPE CORNEA AND FLAP IS REPLACED

LASER EPITHELIAL KERATOMILEUSIS (LASEK SURGERY) - CORNEAL EPITHELIUM IS PEELED USING 20% ETHANOLD, LASER ABLATION IS PERFORMED AND EPITHLEIUM IS REPLACED

Duke Elder 2020 (9 decks)

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