bubble_chart Overview

Serpiginous keratitis is a common acute suppurative corneal ulcer, named for its tendency to spread centrally in a creeping pattern. It often presents with hypopyon, hence also known as hypopyon corneal ulcer.

bubble_chart Etiology

It is mainly caused by highly virulent bacteria. Pathogens include pneumococcus, Staphylococcus aureus, hemolytic or viridans streptococcus, gonococcus, and Bacillus subtilis, among others. The onset is often preceded by a history of corneal surface trauma, such as injuries from tree branches, cotton stalks, or firewood, abrasions from fingernails or eyelashes, or foreign objects like dust or dirt entering the eye. Chronic dacryocystitis is also a contributing factor to infection. Bacteria can be introduced by the injuring object or may already exist in the conjunctival sac.

The disease occurs more frequently in summer and autumn, with higher incidence in rural areas than in cities. It is more common in the elderly and rare in infants, young children, or adolescents, though cases have occasionally been reported in recent years among contact lens wearers.

bubble_chart Clinical Manifestations

Subjective symptoms may include foreign body sensation, stabbing pain, or even a burning sensation. The bulbar conjunctiva shows mixed congestion, and in severe cases, it may be accompanied by edema. The ulcer initially appears at the site of corneal injury after trauma. It begins as a dense grayish-white or yellowish-white infiltrate, roughly the size of a grain of rice or a mung bean, often surrounded by a grayish edematous zone, which is an early-stage manifestation.

If the ulcer is not controlled, it may continue to expand outward, though progression is typically more pronounced toward the central side, resembling a serpentine pattern. Simultaneously, the ulcer can also deepen, forming a stromal ulcer. As necrotic tissue continuously sloughs off, the corneal stroma gradually thins, leading to Descemet's membrane bulging and eventually ulcer perforation.

Severe iridocyclitis is also one of the characteristic features of this condition. Due to the continuous infiltration of bacterial toxins into the anterior chamber, stimulating the iris and ciliary body, early manifestations include anterior chamber turbidity and miosis. Grayish-white or brown powdery deposits may appear on the posterior surface of the cornea, and hypopyon resembling a fingernail shape may form in the lower part of the anterior chamber. As the ulcer enlarges and deepens, the hypopyon gradually increases, sometimes reaching 3–5 mm or even more than half of the anterior chamber.

If the ulcer is controlled in the early stages, it may leave only a small nebula, which, if not within the pupillary area, generally has little impact on vision. However, larger ulcers leave dense leukomas, which may involve either the anterior part of the corneal stroma or the entire layer. These scars are often accompanied by neovascularization, leading to significant visual impairment. In cases of ulcer perforation, an adherent leukoma forms. With large-area perforations, partial or total corneal staphyloma may develop, often resulting in no light perception due to secondary glaucoma. If intraocular infection occurs, it may ultimately lead to phthisis bulbi.

Regardless of the circumstances under which the ulcer heals, in the initial healing stage, the corneal stroma retains infiltration and edema, which take a considerable time to resolve before finally forming a scar.

bubble_chart Diagnosis

The disease is characterized by an acute onset with obvious ocular irritation symptoms, gray-yellow or yellow-white infiltrates or ulcers on the cornea, and early iris membrane inflammation in the anterior chamber. In severe stages, it manifests as yellow-white suppurative ulcers, often expanding to one side, frequently accompanied by hypopyon in the anterior chamber, and abscess formation may occur in the stroma at the base of the ulcer.

bubble_chart Treatment Measures

The development of the ulcer should be promptly controlled. The pathogen of this disease is bacteria, which is sensitive to most antibiotics such as penicillin, streptomycin, neomycin, gentamicin, kanamycin, etc. The preferred route of administration is topical eye drops, while subconjunctival injection also has certain effects, but systemic medication is of little significance.

When administering topical eye drops, attention should be paid to the concentration of the drug and the frequency of administration. Currently, the concentrations of eye drops prepared in our hospital are: penicillin 40,000 units/mL (a skin allergy test is required before use), streptomycin, neomycin, and kanamycin at 5%, and gentamicin at 8,000 units/mL.

The administration method involves giving 2-3 drops every 5-10 minutes for the first 4 hours of treatment, then switching to every half hour. After the ulcer is controlled, the frequency of administration can be further reduced. When applying the drops, the head should be in a supine position to allow the medicinal solution to remain in the conjunctival sac as much as possible.

In recent years, the conventional medication for treating this disease in our hospital has been 5% streptomycin eye drops. According to the above administration method, clinical observations of over 500 cases have achieved satisfactory results, with ulcer healing times ranging from 1 to 3 weeks.

For cases where the ulcer has already perforated or is about to perforate, 5% streptomycin ointment and 1% atropine ointment can be applied to the conjunctival sac, followed by pressure bandaging once daily. This has shown significant effects in controlling infection and preventing or managing perforation.

Subconjunctival injection can also control the progression of inflammation. The drugs and doses are: penicillin 50,000–100,000 units (an allergy test is required), streptomycin 0.2–0.3 g, neomycin 40 mg, and gentamicin 20,000–40,000 units, all administered once daily, generally for 3–9 injections.

This disease often involves an iritis reaction, so the pupil must be fully dilated with atropine.

bubble_chart Differentiation

In the early stage of ulcer disease, it should be differentiated from simple or Pseudomonas aeruginosa keratitis. When the ulcer progresses to a severe stage, it is often easily confused with Pseudomonas aeruginosa or fungal corneal ulcer. The distinguishing points are shown in Table 10-1.

Table 10-1 Differential Diagnosis of Several Bacterial Corneal Ulcers

Ulcer Name		Simple Corneal Ulcer	Pseudomonas Aeruginosa Corneal Ulcer	Serpiginous Corneal Ulcer	Fungal Corneal Ulcer
Onset		Slow, not prone to enlargement	Sudden, rapid progression	Relatively sudden, faster progression	Subacute, slower progression
Predisposing Factors		Often none	Foreign body removal, rice grain injury	Minor trauma, chronic dacryocystitis	Rice grain injury, plant branch abrasion
Incubation Period		Unclear	Half a day to one day	1–2 days	2–4 days
Discharge		None	Purulent, copious	Purulent, less	Watery or mucopurulent, scant
Symptoms		Mild	Severe	Severe	Varies in severity
Ulcer Condition	Color	Grayish-white	Early grayish-yellow, larger ulcers yellowish-white	Mostly grayish-yellow, yellowish-white in severe cases	Early white or grayish-white, mostly yellowish-white in severe cases
	Shape	Small round, about 1–2 mm in diameter	Early annular, circular in severe cases	Irregularly circular	Early irregular, mostly irregularly circular in severe cases
	Density	Grade I infiltration and edema	Early central transparency, uniform infiltration density in severe cases	Central ulcer infiltration often denser	Inconsistent infiltration density
	Surface	Flat or slightly raised	Slightly raised center, glossy and sticky surface	Slightly raised center, glossy surface	Mostly raised surface, dry sensation
Hypopyon		None	Mostly present, yellowish-white	Mostly present, pale yellow	Often present, viscous
Membrane capsule bacterial culture		No growth or growth of weakly virulent bacteria	Possible growth of Pseudomonas aeruginosa	Possible growth of Staphylococcus or Streptococcus	No growth or occasional growth of miscellaneous bacteria
Secretions smear		Generally negative	Often Gram-negative bacilli can be found	Often Gram-positive cocci can be found	Generally negative
Scraping for fungi		Not found	Not found	Not found	Fungal hyphae may be found
Fungal culture		No growth	No growth	No growth	Possible fungal growth
Treatment		Low-concentration antibiotics	Antibiotics effective	Antibiotics effective	Antifungal drugs effective