Trauma terminology and prognostic scoring

The Birmingham Eye Trauma Terminology (BETT) System

Historically, ophthalmic trauma literature was plagued by ambiguous, conflicting terminology. Terms such as "perforating," "penetrating," and "rupture" were frequently used interchangeably, creating clinical confusion and invalidating multicentre research comparisons. In 1996, Kuhn and colleagues formulated the Birmingham Eye Trauma Terminology (BETT), which was subsequently endorsed by major international bodies, including the International Society of Ocular Trauma (ISOT), the American Academy of Ophthalmology (AAO), and the European Board of Ophthalmology (EBO).

BETT establishes an unambiguous, comprehensive mechanical classification based on four fundamental principles:

1. Tissue of Reference: The eyewall is strictly defined as the cornea and sclera. A wound affecting conjunctiva, episclera, or uvea alone without full-thickness eyewall breach is classified as a closed globe injury.
2. Type of Energy / Object: Distinguishes blunt mechanical forces from sharp or projectile mechanisms.
3. Integrity of Eyewall: Categorises the globe as either Closed Globe (no full-thickness breach) or Open Globe (full-thickness breach).
4. Mechanism of Injury: Establishes the directionality of tissue disruption (inside-out vs. outside-in).

Standardized BETT Definitions

• Closed Globe Injury: The eyewall possesses no full-thickness defect. Tissue damage occurs via blunt force deformation, shockwaves, or partial-thickness sharp cuts.

  • Contusion: An injury resulting from blunt force impact. There is no full-thickness eyewall wound. Intraocular damage occurs secondary to sudden anteroposterior globe compression and simultaneous equatorial expansion, or direct energy shockwaves (e.g., traumatic hyphema, iridodialysis, angle recession, cyclodialysis cleft, commotio retinae / Berlin edema, traumatic cataract, choroidal rupture).
  • Lamellar Laceration: A partial-thickness eyewall breach caused by a sharp instrument or shearing projectile. The eyewall is thinned or lacerated, but the remaining lamellae remain intact, preserving intraocular compartmental integrity (e.g., deep corneal stromal laceration not traversing Descemet membrane; partial-thickness scleral scratch).

• Open Globe Injury: A full-thickness defect exists through the cornea, sclera, or corneoscleral junction (limbus).

  • Rupture: A full-thickness eyewall wound produced by the impact of a blunt object. The physical mechanism is inside-out: sudden, severe anteroposterior compression causes an explosive spike in intraocular pressure (IOP) that exceeds the tensile strength of the eyewall. Tissue failure occurs at the thinnest or anatomically weakest sites of the eyewall, which are often distant from the point of impact:
    • The corneoscleral limbus (especially superiorly or superonasally).
    • Sclera immediately posterior to the rectus muscle insertions (where the scleral thickness thins to approximately $0.3\text{ mm}$).
    • Equator of the globe.
    • Sites of prior surgical incisions (e.g., clear corneal cataract wounds, prior keratoplasty grafts, trabeculectomy flaps, radial keratotomy incisions).
  • Laceration: A full-thickness eyewall wound produced by a sharp instrument or high-velocity projectile. The physical mechanism is outside-in: the wounding agent mechanically cuts or shears through the eyewall at the direct point of contact:
    • Penetrating Injury: A single full-thickness entry wound caused by a sharp object or projectile. There is no exit wound.
    • Perforating Injury: Two separate full-thickness wounds—an entrance wound and an exit wound—caused by the same wounding agent or projectile traversing completely through the globe.
    • Intraocular Foreign Body (IOFB): A penetrating injury with retention of the offending metallic, vegetable, plastic, or stone projectile inside the eye.

The Ocular Trauma Score (OTS)

The Ocular Trauma Score (OTS) was developed by Kuhn, Pieramici, and colleagues following analysis of more than 2,500 open and closed globe injuries in the United States and Hungarian Eye Injury Registries. Calculated at the conclusion of initial clinical examination, the OTS provides robust, validated prognostic information regarding the probability of visual recovery at 6 months post-injury, assisting clinicians in setting realistic patient expectations and guiding surgical reconstructive strategies.

Mathematical Calculation of the OTS

The calculation begins with assigning raw points based on the patient's initial presenting best-corrected visual acuity (BCVA). From this baseline, fixed points are subtracted for each of five specific adverse clinical variables:

Categories and Prognostic Interpretation

OTS converts the raw score into five categories: 0–44, 45–65, 66–80, 81–91 and 92–100. Higher categories had better six-month visual outcomes in the derivation cohorts. Presenting acuity is used, with deductions for rupture, endophthalmitis, perforating injury, retinal detachment and RAPD. It is a population prognostic tool, not a promise or a reason to withhold repair. Missing examination data, severe media opacity, paediatric assessment and changing treatment affect application. Explain uncertainty and document each input rather than reproducing invented probability cells.