WhitetoWhite

Whitetowhite is most commonly used to refer to White-to-White (WTW), an ophthalmologic measurement of the horizontal diameter of the visible anterior eye, from one limbus to the opposite limbus across the cornea. The term is often written as White-to-White, abbreviated WTW, and may appear in records or databases in various forms, including the concatenated "whitetowhite." The measurement is typically reported in millimeters and reflects the size of the corneal surface that is visible between the sclera.

WTW is used as a practical surrogate in several clinical contexts. It helps guide the sizing of anterior segment devices, such as scleral contact lenses and certain intraocular lenses used in implantable or phakic procedures. It can influence decisions in refractive surgery planning and eye care device selection, where corneal dimensions affect fitting and postoperative outcomes. While WTW correlates with other anterior segment measurements, it is not a direct proxy for sulcus-to-sulcus diameter, which is more relevant for some intraocular lens sizing. Consequently, surgeons may use WTW in conjunction with other metrics and imaging data to ensure appropriate device fit.

Measurement methods vary. Slit-lamp calipers, digital imaging, and optical biometers (for example, optical coherence or keratometry-based systems) all provide WTW values. Differences in instrument, patient blink, eyelid position, and edema can introduce variability. As a result, repeat measurements or device-specific reference ranges are often used to improve accuracy.