Slit lamp
🔬 Slit Lamp Examination – “The Microscope of the Eye”
🔍 Definition
A slit lamp is a binocular microscope with an adjustable high-intensity light source that projects a thin beam (slit) onto the eye. It’s used to examine the anterior and posterior segments of the eye under magnification.
🧰 Components of the Slit Lamp
| Part | Function |
|---|---|
| Binocular microscope | Magnified stereoscopic view of the eye |
| Slit light source | Adjustable beam size, width, angle, color |
| Joystick & base | For precise positioning |
| Filters | Cobalt blue, red-free, neutral density, etc. |
| Chin rest & headband | To stabilize the patient’s head |
🧪 Structures Examined
🔹 Anterior Segment
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Lids & lashes
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Conjunctiva
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Cornea (clarity, scars, ulcers, edema)
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Anterior chamber (depth, cells/flare for uveitis)
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Iris (color, nodules, tears)
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Lens (clarity, cataracts)
🔹 With special lenses (e.g., 90D, 78D, gonio lens):
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Posterior segment: Optic nerve, macula, retina, vessels
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Angle of anterior chamber (Gonioscopy)
✨ Slit Beam Techniques
| Technique | Use |
|---|---|
| Diffuse illumination | General overview of external eye structures |
| Direct focal illumination | To view specific structures like cornea, lens |
| Retroillumination | Detect opacities by shining light behind them |
| Sclerotic scatter | To highlight corneal edema or clouding |
| Specular reflection | View corneal endothelium |
🔬 Fluorescein Dye Use
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Highlights corneal epithelial defects (abrasions, ulcers)
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Visualized under cobalt blue filter
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Assesses:
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Tear film breakup time
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Contact lens fit
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Seidel test for aqueous leakage
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🧠 What Can Be Diagnosed with a Slit Lamp?
| Condition | Finding on Slit Lamp |
|---|---|
| Conjunctivitis | Redness, discharge |
| Corneal ulcer/abrasion | Fluorescein-stained defect, infiltration |
| Cataract | Lens opacities |
| Uveitis | Cells & flare in anterior chamber |
| Glaucoma | Narrow angle (Gonioscopy), optic nerve cupping |
| Foreign body | Visible on cornea/conjunctiva |
| Dry eye | Tear film instability |
| Herpetic keratitis | Dendritic ulcer with fluorescein |
👁️🗨️ Advantages of Slit Lamp Exam
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High magnification
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Layer-by-layer visualization
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3D depth perception
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Essential for accurate anterior segment diagnosis
🎯 Summary Table
| Feature | Slit Lamp Function |
|---|---|
| Magnification | Yes (up to ~40x) |
| Stereoscopic view | Yes (binocular) |
| Anterior segment | Detailed visualization |
| Posterior segment | Requires special lenses |
| Fluorescein compatibility | Yes, with cobalt blue filter |
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