The Top Ten Indications for Lab and Imaging in Primary Eye Care
James Fanelli, OD, FAAO
CBC - Retinal Hemorrhage
Discussion
Anatomy
RBCs (erythrocytes)- # Red Cells in mL of Venous Blood
Hemoglobin- O2 Carrying Pigment of RBCs
Hematocrit- Column of RBCs in 100 mL of Blood
MCV- Avg. Volume of individual cells in cubic Microns. Hematocrit X 10 divided by RBCs
Retinal NFL or capillary bed
CBC - Retinal Hemorrhage
Discussion
Physiology
RBCs- Carries Hemoglobin
Hemoglobin- Transports O2 to Tissue and CO2 to Lungs
Hematocrit- measure of volume occupied by RBC’s
MCV- individual cell volume elevated to increase O2 transport
CBC - Retinal Hemorrhage
Discussion
Physiology
–individual cellular effects occur at level of capillary bed
–Vitamin B-12
co enzyme utilized in amino acid metabolism
stimulates erythropoiesis
CBC - Retinal Hemorrhage
Discussion
Pathophysiology
Pernicious anemia - precipitated by a gastric condition that interferes with B12 absorption which results
in ineffective erythropoiesis.
Retinal hemorrhage/CWS from tissue hypoxia
Decreased oxygen transport results in fatigue, dyspnea, angina, and syncope.
CBC - Retinal Hemorrhage
Discussion
PEARLS
70-80% of Hematologic Disorders Dx by CBC
B12 Absorption Defect not Dietary Lack
Rare Before Age 35
More Common in Scandinavian, English, and Irish. Rare in Orientals
Treated w/ B12 (cyanocobalamin)
Blood Chemistry- Retinal Emboli
(Assessment)
1. Asymptomatic Cholesterol Retinal Emboli
2. Suspected Diabetic VA Fluctuations
Blood Chemistry- Retinal Emboli
(Plan)
1.& 2.
Executive Profile D
Carotid Doppler
PCP Communication
Educate & Follow q 1 month
Blood Chemistry- Retinal Emboli
Discussion
Pathophysiology
Hypercholesterolemia/Plaque Formation
Arteriosclerosis
Carotid Stenosis
Hyperglycemia
Blood Chemistry- Retinal Emboli
Discussion
PEARLS
Moniter Hgb A1c
Eye w/ MHx Significance
Profile vs. Individual Test
Systemic Risk of Retinal Emboli
Hyperglycemia also Seen w/ Certain Medications(ie. Cortisone) and Trauma
Serology for Granulomatous Disease
Angiotension Converting Enzyme (ACE)
Lysozyme
Skin Test for Anergy (ie. Mumps)
Purified Protein Derivative (PPD)
Anti-Neutrophil Cytoplasmic Antibodies (ANCA)
Granulomatous Disease - Uveitis
Discussion
Pathophysiology
Cells & Flare
Keratic Precipitates
Sarcoidosis
Noncaseating Epithelioid Granulomas
Granulomatous Disease - Uveitis
Discussion
PEARLS
Topical vs. Sub-C/Tenons Injection
ACE Elevated in 60-90% of pts. w/ Systemically Active Sarcoidosis
Also R/O Histo,TB,Hyperthyroid, Cirrhosis & Leprosy w/ Elevated ACE
Granulomas Form Most Commonly in Mediastinal & Peripheral Lymph Nodes, Lungs, Liver, Eyes, &
Skin
Computed Tomography (CT)
Same Physics as Plain Film
Computed Integrated & Image Formation
Soft Tissue Differentiation
Contrast Enhancment Usually Recommended
Indications: Orbital Fx, Foreign Body, Intracranial & Orbit Assessment
Requires Special Views for Orbit
Ordering: Same as Plain Film, w/ or w/o Contrast
CT - Orbital Trauma
Image Results (Plan)
CT Results
Fractured Maxillary Bone w/ Extension into Sinus Cavity
Orbital Emphysema
Continued Plan
Continue 10 Course of Keflex
Follow EOMs
Follow to Resolution
CT - Orbital Trauma
Discussion
PEARLS
Suspect Orbital Infectious Dx if CT Demonstrates Fusiform Muscle Enlargment w/ Blurred Margins
Best Screening Device of Orbit and Sinuses
Treatment Options
Magnetic Resonance Imaging (MRI)
Atomic Orientation and Signal Production by Alternating High Levels of Magnetic Fields
Superior for Soft Tissue Differentiation
Gadolinium Contrast
Special Techniques for Orbits ( Fat Suppression/Surface Coils)
Some Limitations
Ordering: Indicate Area of Question w/ or w/o Contrast, r/o Diagnosis, Special Techniques
MRI - Proptosis w/ Disc Edema
Discussion
PEARLS
Elevated T2 Times Indicate ON EOM Edema
Ability to Document Transformation of Edema to Fibrosis and Fatty Degeneration in Grave’s Dz.
Assists in Surgical Planning
DDx Orbital Pseudotumor w/ Fibrotic Changes due to Lymphoma vs. Leukemic Infiltration
Magnetic Resonance Angiography (MRA)
Non-Invasive Angiogram
Avoids Potential Complications of IV Angiogram
Paramagnetic Contrast not Needed
Generates 3-Dimensional Multi-Plane Scans
Can Detect Aneurysms as Small as 3-4 mm
Indications: AF, OIS, CN Palsies, A-V Mal.
MRA - CN III Palsy
Discussion
PEARLS
Aneurysms Detected in 3-Dimension
Thrombi Show as White Blockages on T1 Images
Tend to Overestimate Degree of Stenosis
“String Sign”
Accuracy Comparable to IV Angiography