Our eyes are our windows to the world, intricate and delicate organs that are remarkably well-protected from the outside environment. However, when this natural barrier is breached, either through surgery, injury, or an injection, there is a risk of a rare but devastating condition known as endophthalmitis. This is not a simple surface infection like pink eye; it is a severe inflammation inside the eye, most often caused by an infection. Endophthalmitis is a true ophthalmic emergency. The speed at which it can cause permanent vision loss means that understanding its symptoms and acting without a moment’s delay is absolutely critical to preserving sight.

Endophthalmitis is a serious and potentially sight-threatening inflammation or infection of the inside of the eye, specifically involving the vitreous and/or aqueous humors, the clear, gel-like fluids that fill the eye’s interior. This condition can develop rapidly and requires urgent medical attention to prevent permanent vision loss or even loss of the eye itself.

The condition is typically classified as:

• Exogenous Endophthalmitis: Infection enters the eye from outside, such as after eye surgery (especially cataract surgery), eye trauma, or intravitreal injections.
• Endogenous Endophthalmitis: Infection spreads from within the body, reaching the eye through the bloodstream. This is rare but often associated with systemic infections or compromised immunity.

Endophthalmitis is not common, but when it occurs, it is a true medical emergency. Early recognition and treatment are key to saving vision.

Analogy: Imagine the eye as a sealed glass globe. If bacteria or fungi get inside, they cloud and inflame everything within, like a fish tank that suddenly fills with algae and debris, obscuring all vision and overwhelming the ecosystem.

Endophthalmitis is caused by an invasion of microorganisms, such as bacteria or fungi, into the eye’s interior structures. The specific type of bacteria or fungus responsible often depends on the source of the infection.

Bacterial Infections: Bacteria are the most common cause of endophthalmitis.

• Post-Operative Infections: Following procedures like cataract surgery, the most common culprits are bacteria that are part of the normal flora of the skin and eyelids, such as Staphylococcus epidermidis. While these are typically less aggressive, they can still cause significant damage inside the eye. More virulent bacteria like Staphylococcus aureus or Streptococcus species can cause a much more rapid and destructive infection.
• Post-Traumatic Infections: After a penetrating injury, a wider and often more aggressive range of bacteria can be introduced, including Bacillus cereus, which is known to cause a particularly severe form of endophthalmitis.

Fungal Infections: Fungi are a less common cause but can lead to a chronic, smoldering infection that may be more difficult to diagnose and treat. Candida species are a common cause of endogenous fungal endophthalmitis, especially in hospitalized patients with central lines or weakened immune systems. Aspergillus and Fusarium species are more often associated with post-traumatic infections, particularly if the injury involved soil or plant matter.

Sterile Endophthalmitis: In some instances, severe inflammation can occur without a live, replicating organism. This is known as sterile endophthalmitis. It can be a reaction to the medication being injected into the eye or to other materials, such as retained lens fragments left behind after a complicated cataract surgery.

Clinically, we often see bacterial endophthalmitis following surgery, while fungal cases usually stem from systemic illness or IV drug use.

You can develop endophthalmitis through either external entry (exogenous) or internal spread (endogenous). The majority of cases result from surgical or traumatic breaches of the eye’s protective barrier.

The most common pathways and risk factors for developing endophthalmitis include:

• After Eye Surgery (Post-operative Endophthalmitis): This is the leading cause of exogenous endophthalmitis.
  • Cataract Surgery: While modern cataract surgery is incredibly safe with a very low infection risk (often cited as less than 0.1%), it is the most common cause simply because millions of these procedures are performed worldwide each year.
  • Other Surgeries: Any intraocular surgery carries a risk, including vitrectomy (removal of the vitreous gel), glaucoma surgery (such as a trabeculectomy), and corneal transplants.
• After Intravitreal Injections: This has become an increasingly common cause. These injections, which deliver medication directly into the vitreous cavity, are a standard treatment for chronic conditions like age-related macular degeneration (AMD), diabetic retinopathy, and retinal vein occlusions.
• After a Penetrating Eye Injury (Post-traumatic Endophthalmitis): Any injury that punctures or ruptures the eyeball (an open globe injury) poses a very high risk of introducing bacteria into the eye.
• Endogenous Spread from a Systemic Infection: Individuals with certain health conditions are at higher risk for endogenous endophthalmitis. These risk factors include:
  • Having a systemic infection or sepsis.
  • Intravenous drug use.
  • Having an indwelling catheter or central line.
  • A weakened immune system (immunocompromised).
  • Recent major surgery elsewhere in the body.

Symptoms of endophthalmitis can begin within 24–72 hours after surgery or trauma (acute), or develop gradually over days to weeks (chronic or fungal).

The hallmark signs and symptoms that demand immediate attention are:

• Severe and Worsening Eye Pain: This is not mild discomfort; it is often a deep, aching, and persistent pain.
• Significant and Progressive Vision Loss: Vision may become very blurry, hazy, or cloudy, often described as looking through a fog that gets thicker over hours or days. Floaters may increase dramatically.
• Marked Redness of the Eye: The white of the eye (sclera) can become profoundly red and inflamed.
• Swollen Eyelids: The eyelids may become puffy, red, and difficult to open.
• Hypopyon: This is a classic sign where a visible layer of white material (a collection of white blood cells, or pus) accumulates in the front chamber of the eye, often seen as a fluid level in the lower part of the colored iris.
• Increased Sensitivity to Light (Photophobia): Bright lights can be extremely uncomfortable or painful.
• Headache: The severe eye pain can sometimes be accompanied by a headache on the same side.

This point cannot be overstressed: Endophthalmitis is a true ophthalmic emergency where every hour matters. The inflammatory process can destroy the retina’s delicate photoreceptor cells with astonishing speed.

You must contact your ophthalmologist or go to the nearest hospital with emergency eye services IMMEDIATELY if you experience the symptoms of endophthalmitis, particularly if you have recently had:

• Any form of eye surgery (especially within the last week or two).
• A drug injection in your eye.
• An injury to your eye.

Do not “wait to see if it gets better overnight.” The prognosis for your vision is directly tied to how quickly you receive treatment. Any delay can be the difference between recovering some sight and suffering irreversible blindness in the affected eye.

Diagnosis

Prompt and accurate diagnosis is vital. If a doctor suspects endophthalmitis, they will act quickly to confirm the diagnosis and start treatment, often before lab results return.

Here are the steps commonly used to diagnose endophthalmitis:

1. Eye Examination: A thorough exam using a slit lamp and an indirect ophthalmoscope will be performed to assess the level of inflammation and check the health of the retina.
2. Ultrasound (B-scan): If the inflammation is so severe that the doctor cannot see into the back of the eye, a B-scan ultrasound will be used to create an image of the retina and check for damage like a retinal detachment.
3. Vitreous or Aqueous Tap: To confirm the diagnosis and identify the specific organism, the ophthalmologist will perform a “tap.” A very fine needle is used to carefully draw a small fluid sample from either the front chamber (aqueous tap) or the main cavity (vitreous tap) of the eye. This sample is immediately sent to the laboratory for culture to grow and identify the bacteria or fungus.

Treatment

Treatment must begin immediately, often on the same day as the diagnosis and usually before the lab results are available.

• Intravitreal Injections: The mainstay of treatment is the injection of potent antibiotics (and sometimes antifungal medication) directly into the vitreous cavity of the eye. This “tap and inject” procedure delivers a high concentration of the drug directly to the site of the infection.
• Steroids: Steroids, either injected into the eye, taken as eye drops, or orally, are often used to control the severe inflammation and limit collateral damage to the eye’s structures.
• Pars Plana Vitrectomy (PPV): For very severe cases of endophthalmitis, a surgical procedure called a vitrectomy may be recommended. During a vitrectomy, the retina surgeon removes the infected vitreous gel and inflammatory debris from the eye and replaces it with a sterile, balanced salt solution. This has the advantage of physically removing a large load of the infectious organisms and improving the clarity of the eye, but it is a more invasive procedure reserved for more serious presentations.

The visual outcome depends on the virulence of the infecting organism, the health of the eye before the infection, and, most importantly, the time that elapsed between the onset of symptoms and the start of aggressive treatment.

Endophthalmitis stands as one of the most serious and urgent conditions in all of ophthalmology. It is a rare but devastating complication of eye surgery, injections, and trauma, capable of causing profound and permanent vision loss in a matter of days. The key to fighting this aggressive intraocular infection is knowledge and speed. Recognizing the cardinal symptoms, severe pain, decreasing vision, and a red eye, and understanding that these are not normal postoperative signs is paramount. The prognosis for vision is a race against time. Never hesitate to contact your eye doctor immediately with any concerns after a procedure.

American Academy of Ophthalmology (AAO). (2023). Endophthalmitis. Retrieved from https://eyewiki.aao.org/Endophthalmitis

Mayo Clinic. (2023). Eye Infections: Endophthalmitis. https://www.mayoclinic.org

Callegan, M. C., Engelbert, M., Parke, D. W., Jett, B. D., & Gilmore, M. S. (2002). Bacterial endophthalmitis: Epidemiology, therapeutics, and bacterium–host interactions. Clinical Microbiology Reviews, 15(1), 111–124. https://doi.org/10.1128/CMR.15.1.111-124.2002

Ali, M. J., & Hegde, V. (2023). Endophthalmitis. In StatPearls. StatPearls Publishing. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK559079/