Anatomically, the orbital septum separates the eyelids from the orbital tissues. Superficial infections anterior to the orbital septum can cause an eyelid abscess or preseptal cellulitis, whereas infections posterior to the septum can cause orbital cellulitis.³,⁵ Paranasal sinus disease is the most common cause of orbital cellulitis, whereas the principal underlying cause of preseptal cellulitis or abscess formation is a traumatic disruption of the protective layers of the skin.¹,⁹ Other underlying conditions include acute hordeolum, dacryocystitis, sinus disease, sinus surgery, upper respiratory tract infection, inflammatory skin conditions (eczema, radiation therapy, or psoriasis), lymphedema, a recent history of brow epilation (tweezing, plucking, threading, waxing, or shaving), manual manipulation of eyelid chronic skin lesions, scratching of eyebrow acne lesions, or dental procedures.⁹,¹⁰,¹¹,¹²,¹³,¹⁴

Patients with systemic diseases such as diabetes, cirrhosis, end-stage renal failure, pulmonary diseases, or malignancy or patients who are immunocompromised are at a higher risk for developing an abscess or preseptal cellulitis following a relatively trivial trauma or from a surgical wound.¹⁵ Warmer weather is associated with a higher incidence of cellulitis and abscess formation because colonization of the skin surface is reduced in low temperatures.⁸ Predisposing factors peculiar to methicillin-resistant Staphylococcus aureus (MRSA) infections, which are increasing in frequency in the periorbital region, include recent hospital admission, intravenous drug use, newborn age range (<28 days), young age particularly in those practicing contact sports, male gender, low socioeconomic status, immunosuppression, military service/prison time, steam bath use, recent treatment with antimicrobials, and close contact with health care workers.¹⁶,¹⁷,¹⁸

A periorbital abscess or cellulitis is usually pyogenic (bacterial) in origin. Although relatively rare, a mycotic etiology is occasionally reported.⁴,¹¹,¹³ The most common organisms implicated in patients with preseptal cellulitis are beta-hemolytic streptococci (most commonly group A Streptococcus or Streptococcus pyogenes), or methicillin-resistant Staphylococcus aureus (MRSA), methicillin-sensitive Staphylococcus aureus (MSSA), and coagulase-negative staphylococci (CoNS).⁸,¹² On the other hand, Staphylococcus spp. (MRSA, MSSA, CoNS) are the predominant pathogens encountered in patients with a cutaneous abscess.⁵,⁶,¹²,¹⁹ Other rarer organisms causing periorbital abscesses or cellulitis include Pseudomonas spp., Streptococcus faecalis, Ekinella corrodens, Escherichia coli, and anaerobes.¹³,¹⁵,²⁰,²¹

MRSA infections have been on the rise in the general population in recent years,¹⁰,¹⁶,²²,²³ and in the periocular region, the prevalence of S. aureus strains reported to be resistant to methicillin varies from 3% to 62%.¹⁰,²⁴ The type of injury can give a general idea about the pathogen involved. A
periorbital infection resulting from sinusitis or upper respiratory tract infection is usually caused by Streptococcus species, or less commonly by Haemophilus influenzae. The latter has declined in frequency since the introduction of the H. influenzae type B (Hib) vaccine.¹²,¹⁴,²⁵ On the other hand, a fungal infection may result from an injury that is contaminated with soil.

The pathogenetic events that lead to abscess formation or preseptal cellulitis are straightforward. Large eyelid lacerations may provide a point of entry to the organisms. Similarly, brow shaving, epilation, or scratching of eyelid or eyebrow lesions may cause smaller breaks in the skin that may likewise facilitate the subcutaneous entry of microbes. The source of the organisms is the exogenous or endogenous microflora, including skin commensals, native bacteria living around hair shafts, or the contaminated hands of the patients themselves.¹² When sinusitis is the primary cause of periorbital infection, the infection may have spread from the ethmoid sinuses through the lamina papyracea, the floor of the frontal sinus, the roof of the maxillary antrum, or through hematogenous spread. Although the virulence of a particular organism may be the principal factor thought to play a role in the development of preseptal infections, host immune responses also substantially participate in disease progression.²⁶

Whether periorbital infections are caused by a local major or minor traumatic event, hematogenous dissemination through sepsis, or direct inoculation in sinusitis patients, the subsequent pathogenic events are the same. Local tissue cells are destroyed by bacterial enzymes and toxins, which in turn trigger an inflammatory response by attracting large numbers of white blood cells. Regional blood flow and vascular permeability are increased under the influence of released cytokines, causing erythema and tissue edema.²¹

Patients usually present with a painful mass that is tender to touch. Although they may experience fever and generalized malaise, systemic symptoms may be absent. Because many cases of preseptal cellulitis and abscess are associated with human behavior, patients should specifically be asked about a history of trauma (skin abrasion, penetrating wound, an insect bite, brow epilation, or scratching a long-standing eyelid or brow skin lesion).¹² The clinician should not shy away from asking male patients about cosmetic brow hair removal as it is no longer a female-only practice.¹² In general, S. aureus, particularly MRSA infections, usually present with pain that is out of proportion to the clinical picture.²⁷ When an abscess or cellulitis develops following trauma, the inflammation is temporary (3-4 days) and spatially related to the original trauma.¹⁰ For instance, following epilation of the eyebrow hairs, the abscess that develops is usually located temporally because this is where females tend to pluck their hairs.¹⁰

An eyelid abscess is a localized suppurative collection of pus that may or may not be pointing. The presenting features include an acute onset of eyelid edema, erythema, a fluctuant mass with surrounding cellulitis and warm skin, and conjunctival chemosis (Figure 44.1). Tenderness usually is maximum over the abscess, which may feel like a fluid-filled cavity upon palpation. Patients with preseptal cellulitis typically present with a diffusely red, swollen, and tender eyelid without a single focus of pointing pus, although on closer inspection a single point of a suppurative collection of pus may be observed. The skin findings in preseptal cellulitis are similar to the classic signs of cellulitis elsewhere in the body: dolor (pain), calor (heat), rubor (erythema), and tumor (swelling), in addition to mechanical ptosis if the upper eyelid is involved (Figure 44.2).⁸

The diagnosis of cellulitis and abscess essentially is a clinical one based on history and physical examination alone,⁸ but radiology (computed tomography [CT]) may be needed if an orbital extension (orbital cellulitis) is suspected. Indications for performing a CT scan include swinging pyrexia that lasts for 36 hours, failure to improve within 24 to 36 hours of antibiotic treatment, or if examination of the eye is impossible because of massive edema.¹³ A blood sample may be taken for a complete blood count, urea, electrolytes, and possibly blood culture. However, this laboratory workup is not routinely required to establish the diagnosis of abscess or cellulitis or to direct future therapy.¹³ Prior identification of the causative organism with a conjunctival swab, skin swab, or even a sinus aspirate may be irrelevant, and waiting for the results of a culture and sensitivity test may be harmful because some of these infections may require immediate medical or surgical intervention. Furthermore, in most patients, conjunctival or skin swabs either will yield negative results, or when they are positive, the concentration of the bacterial load is often low and inaccurate. The results of some swab cultures may be polymicrobial owing to colonization with skin commensals that may not even be involved in the etiology of the underlying preseptal cellulitis or abscess.⁸,¹³ Moreover, in a typical clinical scenario, by the time these patients present to the oculoplastic service, they usually already have been preloaded with antibiotics.⁸ Alternatively, the immune system could have already reduced the number of viable bacteria or a very small number of bacteria may be responsible for a robust inflammatory response due to bacterial toxins and other inflammatory mediators. These inflammatory mediators may contribute more to the pathogenesis of cellulitis than the bacterial load itself.⁶,⁸,¹³,¹⁴ A blood culture may be more accurate, but in some studies, the yield was as low as 2%, and it is not indicated as part of the management except in infants <3 months of age.⁶,¹³

A patient presenting with an acute inflammatory condition involving the periorbital region can prove to be a diagnostic challenge. A misdiagnosis may result in subsequent mismanagement that may prove disastrous.²⁸ Although the diagnosis of an eyelid abscess may be difficult to miss, any condition
that simulates the four cardinal signs of cellulitis (dolor, calor, rubor, and tumor) may be confused with preseptal cellulitis.⁸ There are many mimics of preseptal cellulitis (pseudocellulitis) in the periorbital region, and these are summarized below.