Slit Lamp 1&2

Question 1

common indications for a slit lamp examination??

Answer 1

dry eyes
lacrimation, itchiness, grittiness
haloes around lights
contact lens wearer
recent foreign body sensation
increased intraocular pressure (IOP)

Question 2

what are the main components examined during a routine slit lamp examination??

Answer 2

lids
conjunctiva
limbus
cornea
tears
anterior chamber
iris
lens

Question 3

biomicroscopy techniques used with slit lamps?

Answer 3

tonometry
gonioscopy
pachymetry
fundoscopy
lens fitting
lid eversion

Question 4

what are the magnification levels of a biomicroscope and their uses??

Answer 4

• low(6-10x): general examination of eye lids, conjunctiva, cornea & anterior chamber
• medium(16-25x): examination of conreal epithelium, stroma, endothelium, lens surface
• high(25-40x): detailed examination of corneal epithelium, microcysts, dystrohpies, stromal striae, folds, endothelium, polymegathism, blebs

Question 5

diff methods of illumination used in slit lamp examinations??

Answer 5

• diffuse: low mag, wide beam for general eye assessment
• optic section, conical beam& parallel piped for corneal assessment (direct illumination)
  -indirect illumination: view to side of beam for corneal tissue& iris pathology
• retro-illumination: uses iris/fundus to back illuminate the cornea
  -specular reflection: refracted light from corneal surface to assess tear film& endothelium
  sclerotic scatter: halo light to examine corneal opacites
  tangenital illumination: used for iris freckles, tumors & general corneal integrity

Question 6

how is specular reflection used in slit lamp biomicroscopy??

Answer 6

Uses the angle of incidence to reflect light off the corneal surface

Focuses on the area of interest by adjusting the illumination beam

Visible reflection through one eyepiece at a time

Commonly used to assess tear film debris, endothelium, and crystalline lens (orange peel appearance)

Question 7

What is retro-illumination and its use?

Answer 7

Involves using the iris or fundus as a light source to illuminate the cornea

Moderate to high magnification

Highlights structures like microcysts, vacuoles, crystalline lens opacities, and vascularisation

Question 8

How is sclerotic scatter used in slit lamp biomicroscopy?

Answer 8

Illuminates cornea with a narrow slit at the limbus

Total internal reflection produces a halo of light

Used for detecting corneal opacities, scars, edema, or foreign bodies

Question 9

What is Van Herrick’s technique used for?

Answer 9

Measures the depth of the anterior chamber by assessing the cornea-to-chamber angle ratio

Question 10

How does fluorescein assessment work with the slit lamp?

Answer 10

Blue filter is used to highlight fluorescein dye

Yellow filter enhances visualisation of the tear breakup time (TBUT)

Used for evaluating RGP contact lens fitting patterns

Question 11

What are the different types of direct illumination in slit lamp biomicroscopy?

Answer 11

Optic section: Thin beam that illuminates the cornea to assess depth and structure

Conical beam: Circular beam used to detect inflammatory cells in the anterior chamber

Parallel-piped: Broader beam used to evaluate corneal nerve fibers and punctate keratitis

Question 12

What is indirect illumination used for in slit lamp examination?

Answer 12

Allows observation from the side of the light beam

Useful for assessing epithelial vesicles, erosions, and iris pathology

Requires decoupling the observation system from the light beam

Question 13

prior to use of the slit should be focussed for:

Answer 13

the operator’s distance Rx

Question 15

Which slit lamp technique shows the layers of the cornea?

Answer 15

optical section

Question 16

The curvature of the cornea is normally:

Answer 16

flatter in the periphery than in the centre (the cornea is steepest in the centre and becomes flatter towards the periphery which helps focus light effectively onto the retina)

Question 17

What is the approximate diameter of the corneal area measured by keratometry?

Answer 17

3mm

Question 18

Occluding the fellow eye during keratometry is advisable, because:

Answer 18

it improves fixation by the target eye

Question 19

Prior to making a keratometry measurement, the subject is generally advised to:

Answer 19

blink then stare

Question 20

some facts:

Answer 20

keratometry measures the curvature of the central cornea

central corneal curvature is usually between 7.4mm to 8.8mm

the cornea contributes to 2/3 of the eye’s total refractive power(the lens 1/3)

the normal cornea is steeper centrally than peripherally

Question 21

For use in the eye, you should wet a fluorescein strip with:

Answer 21

normal saline

Question 22

What is the favoured illumination technique for evaluating the depth of a foreign body in the
cornea?

Answer 22

optic section

Question 23

Which ocular structure requires the highest slit lamp magnification for optimum viewing?

Answer 23

Corneal endothelium