[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Ophthalmology](https://durgical.com/en/ophthalmology/) › [The eye exam](https://durgical.com/en/ophthalmology/areas/exam/) › The slit lamp: what each light shows # The slit lamp: what each light shows - Examination The slit lamp is a microscope with an adjustable slit of light. Changing the width, angle and filter of the light shows each layer of the front of the eye. Updated Nov 5, 2026 **See it in 3D:** [Cornea](https://durgical.com/en/anatomy/cornea/) · [Iris](https://durgical.com/en/anatomy/iris/) · [Lens](https://durgical.com/en/anatomy/lens/) ## Key points - Cells and flare in the anterior chamber = active uveitis. - Cobalt blue filter + fluorescein = epithelial defects. - Van Herick estimates angle depth; gonioscopy shows it. - Hypopyon = pus; hyphema = blood. ## What it is The slit lamp biomicroscope combines a binocular microscope with a light that can be narrowed to a slit and moved around the eye. It shows the lids, conjunctiva, cornea, anterior chamber, iris and lens in three dimensions and at high magnification. With a hand-held lens it also shows the retina and optic disc, and with a contact lens the drainage angle. It is the basic tool of ophthalmology and of many emergency departments. ## Normal values and scales - Anterior chamber cells (white blood cells) and flare (protein) are graded on a standard scale and mean active inflammation. - The peripheral anterior chamber depth compared with corneal thickness (the Van Herick method) estimates whether the angle is narrow. - Pus settled at the bottom of the chamber is a hypopyon; blood is a hyphema. - Gonioscopy (a mirrored contact lens) is needed to see the drainage angle itself. ## How it is done - Adjust the chin rest so the patient's eyes are level with the mark on the frame, and set the eyepieces. - Start with low magnification and a broad, diffuse light to look at the lids, lashes, conjunctiva and cornea. - Narrow the light to a thin slit at an angle (optic section) to see the depth of a corneal lesion and the depth of the anterior chamber. - Shorten the slit to a small, bright beam in a dark room to look for cells and flare in the anterior chamber. - Use the cobalt blue filter after fluorescein to show epithelial defects. - Use retroillumination (light reflected from the iris or fundus) to see corneal and lens opacities. - Hold a high-power lens in front of the eye to see the optic disc and macula. ## How to interpret it - Cells in the anterior chamber confirm uveitis; the general doctor without a slit lamp sees only ciliary flush and a small pupil. - A narrow peripheral chamber warns of angle closure risk before dilating. - A dendritic ulcer stained with fluorescein is herpes simplex keratitis and contraindicates steroids. ## Next step / Initial management - No slit lamp available and a red flag present: refer the same day rather than guess. - Anterior chamber cells or a hypopyon: same-day ophthalmology. - Narrow angle on Van Herick: gonioscopy by ophthalmology before routine dilation where possible. - Learn the basic techniques: in the emergency department the slit lamp is used for foreign bodies, abrasions and the Seidel test. ## Test yourself Think of the answer, then tap the question to see it. ## What do cells and flare in the anterior chamber mean? Active intraocular inflammation (anterior uveitis): white cells and leaked protein in the aqueous. ## What does the Van Herick method estimate? The depth of the peripheral anterior chamber compared with corneal thickness, as a screen for a narrow angle. ## Which filter is used to see corneal staining with fluorescein? The cobalt blue filter. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/ophthalmology/the-slit-lamp-what-each-light-shows/) ## Connections ## See it in 3D 3 The structures of Durgical's 3D anatomy where it is found. - [Cornea](https://durgical.com/en/anatomy/cornea/) - [Iris](https://durgical.com/en/anatomy/iris/) - [Lens](https://durgical.com/en/anatomy/lens/) ## Related 5 - [Fluorescein staining and the Seidel test](https://durgical.com/en/ophthalmology/fluorescein-staining-and-the-seidel-test/) - [Red eye: what is serious and what is not](https://durgical.com/en/ophthalmology/red-eye-what-is-serious-and-what-is-not/) - [The anterior chamber and the drainage angle](https://durgical.com/en/ophthalmology/the-anterior-chamber-and-the-drainage-angle/) - [Corneal and subtarsal foreign bodies](https://durgical.com/en/ophthalmology/corneal-and-subtarsal-foreign-bodies/) - [The uvea: iris, ciliary body and choroid](https://durgical.com/en/ophthalmology/the-uvea-iris-ciliary-body-and-choroid/) ## Related conditions 4 - [Uveitis](https://durgical.com/en/conditions/uveitis/) - [Keratitis and corneal ulcer](https://durgical.com/en/conditions/keratitis-and-corneal-ulcer/) - [Acute angle-closure glaucoma](https://durgical.com/en/conditions/acute-angle-closure-glaucoma/) - [Corneal abrasion and ocular foreign body](https://durgical.com/en/conditions/corneal-abrasion-and-ocular-foreign-body/) ## In Pharmacology 1 - [Fluorescein](https://durgical.com/en/pharmacology/fluorescein/) [← All of ophthalmology](https://durgical.com/en/ophthalmology/) Educational content; not a clinical guideline and no substitute for assessment by a health professional. For sudden visual loss, severe eye pain, a chemical burn or an eye injury, go to an emergency department at once. Sources: [Slit-Lamp Biomicroscope](https://www.ncbi.nlm.nih.gov/books/NBK587440/) (StatPearls Publishing (NCBI Bookshelf), 2023); [Auxiliary Lenses for Slit-Lamp Examination of the Retina](https://www.ncbi.nlm.nih.gov/books/NBK587346/) (StatPearls Publishing (NCBI Bookshelf), 2023). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/ophthalmology/the-slit-lamp-what-each-light-shows/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/ophthalmology/the-slit-lamp-what-each-light-shows/