Approach to Corneal Trauma 
David Chenoweth, Christopher Sales, Mark Greiner, Chau Pham, Erin Shriver, Kanwal Matharu 
 
OPEN MANUAL OF SURGERY IN RESOURCE-LIMITED SETTINGS 
www.vumc.org/global-surgical-atlas 
This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License  
 
Background:  
A corneal foreign body is an object adherent 
to or embedded in the cornea, the anterior-most 
portion of the eye. The cornea is one of the most 
densely innervated structures in the body and is 
incredibly sensitive to even microscopic foreign 
bodies. 
Prompt removal of a corneal foreign body is 
important in preventing infection, scarring, or even 
perforation. 
Removal of a corneal foreign body rarely 
requires the use of an operating room, although a 
well-lit clean area with appropriate instrumentation 
is required. 
 
Anatomy:  
The cornea is the transparent part of the eye 
that covers and protects the iris and pupil, allowing 
light to reach the back of the eye. It is an avascular 
tissue that functions as a structural barrier and, in 
conjunction with the tear film, provides the majority 
of the total refractive power of the eye. 
The cornea is essentially a convex oval, 
measuring 11-12 mm in the horizontal meridian and 
9-11 mm in the vertical meridian. It is thickest in the 
periphery, and thinnest at its center. Generally, the 
cornea is 550-560 microns thick in the center. The 
thickness is largely governed by the collagen 
containing stroma of the cornea. 
 
 
Diagram of the eye. The cornea is a convex oval on its anterior 
surface. Detail of the part in the Red box is shown further below. 
Source: Rhcastilhos. and Jmarchn 
https://commons.wikimedia.org/w/index.php?curid=1597930  
 
 
5 layers of the cornea, close-up detail of the Red box in the 
previous picture. See the text below for details. 
 
Histologically, the cornea consists of 5 layers. 
From anterior to posterior: 
1. The corneal epithelium: a non-keratinized 
stratified squamous epithelium with cuboidal 
basal cells. This layer makes up about 1/10th of 
the corneal thickness. It functions to protect the 
surface of the eye from injury and pathogens. 
Approach to Corneal Trauma 
David Chenoweth, Christopher Sales, Mark Greiner, Chau Pham, Erin Shriver, Kanwal Matharu 
 
OPEN MANUAL OF SURGERY IN RESOURCE-LIMITED SETTINGS 
www.vumc.org/global-surgical-atlas 
This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License  
 
2. Bowman’s layer: an anterior limiting lamina for 
the stroma composed of collagen fibrils. 
3. The Stroma: a largely acellular layer composed 
of collagen and fibroblasts. The density of 
intertwined collagen fibrils is greatest at the 
periphery and anterior aspects of the cornea. This 
gradient of density provides the cornea with its 
shape. It also contributes to the mechanical 
weakness of the very posterior stroma, an 
attribute important to note prior to any 
instrumentation involving the stroma.  
4. Descemet’s membrane: A cell-free matrix that 
acts as a posterior limiting lamina for the stroma 
as well as a basement membrane for the 
underlying endothelium. 
5. Endothelium: A single layer of squamous cells 
that actively transports water from the stroma 
into the anterior chamber in order to maintain the 
transparency of the corneal stroma. 
 
 
A slit lamp photo depicting a normal cornea. The curved, sharp 
blue line represents the epithelium and the thick, faded blue line 
highlights the stroma.  
 
Principles:  
Symptoms of a corneal foreign body include 
a foreign body sensation, pain, tearing, light 
sensitivity and vision changes. 
Should a patient’s presentation raise concern 
for a corneal foreign body, it is important to ascertain 
the suspected material as well as the mechanism of 
injury. 
Different materials carry different infection 
and chemical injury risks. Soil and plant material are 
associated with bacterial and fungal infections. Metal 
material, particularly iron, carries the risk of 
oxidative injury to the stroma resulting in a “rust ring” 
if not removed within several hours; however, these 
“rust rings” will typically self-resolve over time or 
can be manually shaved away as the stroma 
regenerates. Infections and rust rings increase the 
risk of permanent corneal scarring. Cement, 
particularly wet cement, can cause alkaline burns 
when it reacts with water in the tear film. Any 
concern for a chemical burn in the eye should prompt 
emergent irrigation. 
The mechanism can be critical in determining 
the risk of globe perforation. Dense materials 
moving at high speed carry a high risk of globe 
perforation. These patients require careful slit-lamp 
examination, and if possible, ultrasound or CT 
imaging. MRI must be avoided if there is suspicion 
of metal involvement.  
After obtaining a history, the patient should 
have a complete 8-point eye exam: best corrected 
vision, measurement of intraocular pressure, pupils, 
extraocular motility and alignment, confrontation 
visual fields, external examination, fundoscopic 
examination, and a thorough slit lamp examination 
including eversion of the eyelids and sweeping of the 
fornixes to reveal any additional foreign bodies.  
A careful slit lamp exam is pertinent to detail 
the location, size, and depth of the foreign body. The 
slit lamp is an instrument consisting of a high-
intensity light source combined with a bimicroscope, 
that is focused to shine a thin sheet of light into the 
eye as the clinician visualizes the structures of the 
anterior and posterior segments. If a slit lamp is 
unavailable, it is reasonable to examine the eye under 
the highest magnification that is available, such as 
surgical loupes or a magnifying glass. 
 
A slit lamp allows a clinician (Left) to view details of the eye 
under magnification with a thin sheet of focused light. Source: 
Ralf Roletschek 
https://commons.wikimedia.org/w/index.php?curid=5083599  
 
Fluorescein stain under cobalt blue light is 
useful in highlighting epithelial defects and can aid 
Approach to Corneal Trauma 
David Chenoweth, Christopher Sales, Mark Greiner, Chau Pham, Erin Shriver, Kanwal Matharu 
 
OPEN MANUAL OF SURGERY IN RESOURCE-LIMITED SETTINGS 
www.vumc.org/global-surgical-atlas 
This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License  
 
in the identification of small foreign bodies in both 
the cornea or eyelid. If resources allow, a Seidel test 
should be performed at the time of slit lamp 
examination (see below).  
 
Slit lamp photo demonstrating a metallic corneal foreign body 
(Red arrow).  
 
 
Slit lamp photo demonstrating a corneal epithelial defect (Red 
circle) highlighted with the application of fluorescein dye under 
cobalt blue light.  
 
A Seidel test can reveal occult perforations, 
signifying an open globe. This test is performed by 
applying fluorescein with a strip of filter paper to the 
injury site and observing the area under cobalt blue 
light at a slit lamp. In a positive Seidel test, aqueous 
humor leaking from the injury will dilute the 
normally green stain producing a dark blue stream 
from the site of perforation. These patients frequently 
require surgery in an operating room. See the chapter 
on open globe repair. 
 
Slit lamp photo demonstrating leaking aqueous humor from a 
corneal injury, a positive Seidel test under cobalt blue light.  
 
Decision Making: 
Most corneal foreign bodies are superficial 
and can be removed at the slit lamp with a pair of 
Jeweler’s forceps. Delaying removal can result in 
migration of the foreign body deeper into the stroma 
and can even result in delayed perforation. 
Incomplete removal of foreign bodies causing 
chemical injuries can result in irreversible damage. 
Attempts to remove deeply imbedded foreign 
bodies risks perforation, therefore removal of a 
deeply penetrating foreign body should be performed 
in the operating room. However, it may not be 
necessary to attempt removal of all full thickness or 
intra-ocular foreign bodies. Objects that do not pose 
significant chemical or infectious risk, such as plastic 
or glass, are considered inert. Inert foreign bodies 
may be managed conservatively with serial 
examinations. 
Before attempting removal, the patient’s 
ocular surface should be anesthetized. With the eye 
anesthetized the patient will be asked to fixate on a 
target while the surgeon uses a small needle to lift the 
foreign body from the stroma. Once free of the 
stroma the foreign body can be safely removed with 
a pair of small forceps, a cotton tipped applicator, or 
even a magnet depending on the material of the 
foreign body. This procedure is described in more 
detail in the next chapter.  
Approach to Corneal Trauma 
David Chenoweth, Christopher Sales, Mark Greiner, Chau Pham, Erin Shriver, Kanwal Matharu 
 
OPEN MANUAL OF SURGERY IN RESOURCE-LIMITED SETTINGS 
www.vumc.org/global-surgical-atlas 
This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License  
 
After foreign body removal the cornea should 
be reexamined for any residual foreign material. An 
assessment of the epithelial defect should be made 
including a final Seidel test. 
Patients should receive broad-spectrum 
topical ophthalmic antibiotics for at least one week. 
Typical antibiotics used to cover corneal foreign 
bodies include polymyxin B/trimethoprim drops, or 
a polysporin ointment. In cases of a large epithelial 
defect, the ointment formulation provides additional 
lubrication 
that 
reduces 
discomfort. 
If 
the 
mechanism of injury involves contact lens wear, 
organic matter, or a fingernail, then the patient 
should be placed on a topical fluoroquinolone and 
followed closely for the development of microbial 
keratitis. Topical steroids are typically avoided due 
to increased risk of infection. 
Depending on the size and proximity to the 
center of the cornea, the patient should be evaluated 
within 1 to 7 days to assess the epithelial defect and 
monitor for signs of infection. It is reasonable to 
discontinue antibiotics once the epithelial defect has 
closed. 
Unfortunately, if the foreign body penetrates 
Bowman’s layer, scar formation is likely. If centrally 
located, these scars may affect vision. Otherwise, the 
cornea is resilient, and most patients’ long-term 
vision is unaffected. 
 
All photos used with permission from Eyerounds.org 
except as otherwise indicated: 
https://eyerounds.org/#gsc.tab=0&gsc.q=corneal%
20foreign%20body%20removal&gsc.sort=  
 
David Chenoweth BA,  
Christopher Sales, MD MPH, 
Mark Greiner, MD 
Chau Pham, MD 
Erin Shriver, MD 
Kanwal Matharu MD 
University of Iowa Carver College of Medicine 
Iowa, USA 
 
August 2024 
 
