Removal of Corneal Foreign Bodies
A corneal foreign body (FB) is an object that is superficially adherent or embedded in the cornea. As the most anterior part of the globe, the cornea is the most exposed to foreign bodies. Some of the common foreign bodies that may be embedded in the cornea include glass, metal, sand, plastic, or wood. The removal of a corneal foreign body is typical performed in an office or emergency room setting. Symptoms include foreign body sensation, pain, tearing, light sensitivity and decreased vision.
Should any foreign body become lodged in the cornea, it is important to obtain a thorough history to prepare for the procedure and provide appropriate patient care. Some questions to ask include: What? When? Where and How? For example, an iron foreign body will start forming a rust ring after four to six hours of being lodged in the cornea. Injuries caused by vegetable matter or soil are more likely to get infected. Knowing the mechanism of the injury is important in eliciting the force with which the FB entered the corneal and determining the need for any additional tests to evaluate for possible ocular perforation and intraocular foreign bodies. Some of those tests include an ocular ultrasound (B scan), thin cut orbital CT scan, and gonioscopy. Patient might need an updated tetanus immunization.
After obtaining detailed history, patient should have their best corrected visual acuity checked, followed by a thorough slit lamp exam. Assess the type and depth of the FB carefully. Deeply embedded FBs may need to be removed in the OR. Fluorescein dye test is beneficial to highlight a FB and any corneal abrasions.  Fornices should be everted to look for any additional FBs.
Extreme caution must be exercised in order to remove corneal FBs safely and in timely fashion to minimize risk of infection, inflammation, scarring, and vision loss.  With time, the foreign body can get pushed deeper and deeper into the cornea, sometimes penetrating all the way through the entire cornea and becoming dislodged internally within the eye. Glass and fiberglass FBs are generally well tolerated in the corneal stroma and can occasionally be monitored if the removal will cause more damage. 
The patient’s ocular surface should be anesthetized with topical anesthetic such as ophthalmic proparacaine hydrochloride 0.5% or tetracaine hydrochloride 0.5% to allow the treatment to be performed without any additional pain or discomfort for the patient. Give the patient a target to fixate at to keep the eyes steady. Upper and lower eyelids can be gently held in place with fingertips to essentially immobilize the eyelids. In most instances, a needle is the best instrument. A 25- or 27-gauge 5/8” needle is a good choice as it provides adequate strength to lift the FB from the corneal surface. 
Looking through a slit lamp, approach the corneal at an oblique or tangential angle to avoid corneal perforation. Engage the FB at its edge and loosen it up. One can use a subtle flicking motion to complete the procedure. With the foreign body loosened up, you can use forceps to gently remove the foreign body from the eye. 
In cases involving a vegetable matter, a long needle-like foreign object, or a foreign body adherent to the corneal surface, jeweler’s forceps might be the preferred tool for the removal. Metallic FB can be removed with a magnetic spud. A moist cotton tipped applicator can be used for removal of superficial foreign bodies. Occasionally, irrigation is used to dislodge multiple small particles.
After removal of a metallic foreign body, there might be a brownish-orange rust ring remaining. It can be lifted with a needle or jeweler’s forceps. The Alger brush is used in most cases to remove the rust ring. The goal is to remove as much of the rust as possible safely without causing too much tissue disruption or corneal perforation.
After removing a FB, re-valuate the cornea for any residual foreign particles, assess the depth of the excavation and extent of the epithelial defect. Perform a final evaluation with fluorescein sodium dye and cobalt blue light.
After removing a foreign body, patients should be placed on broad-spectrum topical ophthalmic antibiotics for one week or until the corneal surface is re-epithelialized. A therapeutic bandage contact lens can be used short-term to reduce discomfort. The lens acts as a barrier and reduces the shear forces of the eyelids against the corneal surface, minimizes the risk of epithelial tearing and promotes healing. A bandage contact lens should be used with caution as it can promote a more infective environment and should be monitored closely. Pressure patch can be used cautiously but is usually not necessary. A short-acting topical cycloplegic drops can be used to alleviate discomfort.
After a FB removal, patient should be typically seen in 24 hours to evaluate the cornea for any developing infections, edema and epithelial defects. The exact follow up and post-procedural care will depend on the nature and depth of the FB. 
- Cao, CE. “Corneal Foreign Body Removal”. Medscape. Nov 7, 2018. https://emedicine.medscape.com/article/82717-overview.
- Murchison, AP. “Corneal Abrasions and Corneal Foreign Bodies”. Merck Manual. Nov 2017.
- Shetler, J and Lighthizer N. “Foreign Body Removal in 12 Steps” Review of Optometry. Jan 15, 2015.
- Primary Care Ophthalmology. "Foreign Body Removal". U Ottawa. https://www.med.uottawa.ca/procedures/slamp/body_removal.htm
- "Corneal Foreign Body". Edward S. Harkness Eye Institute. Columbia University Department of Ophthalmology. https://www.columbiaeye.org/education/digital-reference-of-ophthalmology/