Ocular Diagnostics

Question 1

the main objective of survey radiography of the skull in a patient with orbital disease is to:

assess the bony components of the orbit for lysis, proliferation or trauma
look for extension of the disease process through the cribiform plate
detect soft tissue pathology, including mass lesions
Evaluate the patency of the lacrimal duct

Answer 1

assess the bony components of the orbit for lysis, proliferation or trauma

Question 2

the lacrimal duct in the dog:

extends to the first 1st premolar, medial to the maxillary recess and medial to the maxillary molars
extends the length of the nasal cavity, lateral to the maxillary recess and lateral to the maxillary premolars and canine
extends to the level of the 1st premolar, lateral to the maxillary recess and lateral to the maxillary molars
extends the length of the nasal cavity, medial to the maxillary recess and medial to the maxillary premolars and canines

Answer 2

extends the length of the nasal cavity, medial to the maxillary recess and medial to the maxillary premolars and canines

Question 3

when using diagnostic ultrasound, high frequency sound provides:

good depth of penetration, low spatial resolution
limited depth of penetration, high spatial resolution
good depth of penetration, high spatial resolution
limited depth of penetration, low spatial resolution

Answer 3

limited depth of penetration, high spatial resolution

Question 4

which one of the following statements regarding multi-detector CT is most accurate?

CT has a limited ability to display air-filled structures and bone
use of contrast media and bolus tracking allows evaluation of blood vessels and vascular structures
patient positioning for CT is critical
CT is the advanced imaging modality of choice for evaluation of the intra-calvarial structures

Answer 4

use of contrast media and bolus tracking allows evaluation of blood vessels and vascular structures

Question 5

which one of the following statements most correctly describes the benefit of MRI for imaging a patient with orbital disease:

MRI is the modality of choice for assessment of bony structures
MRI scans can be completed quickly and are generally possible in conscious patients
MRI images can be reformatted into different planes without significant drop in image quality
MRI allows accurate assessment of intra-calvarial structures

Answer 5

MRI allows accurate assessment of intra-calvarial structures

Question 6

what frequency of ultrasound probe will give the best anatomic detail of the globe?

Answer 6

10-15MHz

Question 7

what is the best tube to transport fluid for cytological analysis to the lab?

Answer 7

EDTA

Question 8

sample of blood from a fasted dog is macroscopically lipaemic. This appearance is most likely to indicate what on serum biochemistry?

Answer 8

elevated triglycerides

Question 9

which one of the following statements is most accurate about fructosamine?

fructosamine generally remains elevated even in well stabilised diabetics
fructosamine gives an indication of the glycemic state over the previous 1-3 weeks
fructosamine levels cannot distinguish between persistent hyperglycaemia and transient hyperglycaemia due to stress
fructosamine gives an indication of the glycaemia state over the previous 1-3 days

Answer 9

fructosamine gives an indication of the glycemic state over the previous 1-3 weeks

Question 10

you have taken a conjunctival swab and wish to submit for bacterial culture. What is the best way to send the swab?

Answer 10

amies transport medium

Question 11

Which one of the following is most accurate about PCR:

• quantitative real time PCR allows estimation of clinical significance
• DNA must be intact for conventional PCR methodology to work
• PCR is only useful for the detection of bacterial infection
• Positive results on PCR are clinically significant

Answer 11

quantitative real time PCR allows estimation of clinical significance

Question 12

the sensitivity of a test is define as…

Answer 12

true positives/(true positives + false negatives) x 100

the ability of a test to correctly identify patients with a disease

A highly sensitive test will almost always detect animals with the disease but there may be a few false negatives.

Question 13

Which one of the following responses would classically be expected in the first few days of a disease?

• elevated IgM
• Elevated IgG
• Elevated IgM and IgG
• no change in the first few days

Answer 13

elevated IgM

Question 14

What cells might you expect on cytology from a dog with suspected pannus?

Answer 14

a mixture of neutrophils, macrophages and lymphoid cells

Question 15

what is one of the commonest causes of chronic DIC in small animal practice?

Answer 15

lung worm

Question 16

give 6 advantages of radiography in ophthalmology

Answer 16

readily accessible
relatively cheap
familiarity with use
shows orbital bony change
shows other areas of the head
thoracic and abdominal metastasis check

Question 17

give 5 limitations of radiography in ophthalmology

Answer 17

1. usually requires GA or heavy sedation
2. time consuming
3. superimposition of structures and conformational variability little to no information about soft tissues or precise extent of lesions involving bone.
4. No value for eye itself
   5 .contrast studies are technically demanding

Question 18

give 7 advantages of ultrasonography in ophthalmology

Answer 18

Often available
Relatively cheap
Quick to perform
Can usually be performed in conscious patients
Versatile – many ocular and orbital indications
Permits ultrasound-guided techniques (e.g. biopsy)
Abdominal metastasis check possible

Question 19

give 6 disadvantages of ultrasonography in ophthalmology

Answer 19

Operator-dependent; requires practice and skill
High-quality transducers required
Diffuse pathology may be hard to recognize (compared with focal lesions)
may be non-specific (e.g. intraocular neoplasia and blood clots can look the same)
Images are confined to globe and orbit and do not show other areas of the head
Static saved images are often less useful than those of other imaging techniques
(although, when available, the ability to save dynamic sequences may be
advantageous)

Question 20

give 8 advantages of MRI in ophthalmology

Answer 20

Superb soft tissue definition and contrast with considerable information about bone; ready differentiation between fluid and soft tissue
Slice images can be obtained in any plane, yielding three-dimensional (3D) information and abolishing superimposition
• Provides information about the nature of the tissues
(e.g. fluid, fat)
Accurate patient positioning is not crucial
Shows other areas of the head and the brain in excellent detail
Contrast studies are easily performed and provide excellent information about the vascularity of tissues
Allows 3D treatment planning for surgery or
radiotherapy
Usually the technique of choice for orbital disease

Question 21

give 9 disadvantages of MRI in ophthalmology

Answer 21

1. May not be readily accessible to practitioners
2. Requires GA and MRI-compatible anaesthetic equipment
   3 .Expensive
3. Time-consuming, especially with low field magnets
4. Difficult to design set protocols due to variability of lesions
5. Can be challenging to interpret
6. Non-diagnostic or even contraindicated in the presence of ferrous metallic foreign
   bodies; may be non-diagnostic with certain ocular or orbital prostheses
7. Does not provide metastasis check
8. Guided biopsy requires specialist equipment

Question 22

give 9 advantages of CT in ophthalmology

Answer 22

Superb bony detail and provides fair soft tissue information (superior to radiography)
Quicker than MRI and radiography and thus safer for trauma patients
Can be performed under sedation and general anaesthesia is not necessarily required
Slice images can be obtained, primarily in the
transverse plane
Contrast studies are easily performed
Allows 3D treatment planning for surgery or
radiotherapy; reconstructed 3D images are very helpful for evaluation of bone
Shows other areas of the head, beyond the orbit
Guided biopsy may be possible
Metastasis check possible and more sensitive than radiography

Question 23

give 10 disadvantages of CT in ophthalmology

Answer 23

May not be readily accessible
Usually requires heavy sedation or general anaesthesia
Expensive
Exposure to higher doses of ionizing radiation than with radiography means that
personnel should not usually be present in the CT room during the study
Accurate patient positioning is necessary as images are only acquired transverse to
the gantry
Images reconstructed in other planes are inferior
Inferior to MRI for information on the soft tissues, including the brain
Diffuse inflammation may be hard to detect
Streak artefacts arise with metallic foreign bodies
Can be challenging to interpret