Nomogram for Femtosecond Nonpenetrating Intrastromal Astigmatic Keratotomy During Femtosecond Laser–Assisted Cataract Surgery

Sunday, April 19, 2015: 8:01 AM
Room 4 (San Diego Convention Center)
Julian D. Stevens, FRCOphth
Alexander C. Day, PhD, FRCOphth
Nicola M. Lau, MBBS, BSc(Hons)

To describe a nomogram for femtosecond laser intrastromal astigmatic keratotomy during femtosecond laser-assisted cataract surgery and outcomes after surgery.

Eighty eyes with corneal astigmatism and mean pre-op cylinder of 1.3 dioptres had femtosecond laser-assisted cataract surgery with concurrent paired femtosecond laser intrastromal astigmatic keratotomy (FSAK), created between 20% to 80% corneal depth and with an 8.0 mm optical zone using a Catalys femtosecond laser. The nomogram takes into account the effect of the primary incision for surgery as well as side-port(s). Using pre and postoperative topography and refractive data at 1 month, a nomogram has been created using regression analysis.  A control group of 51 eyes were analyzed to determine the surgically induced astigmatism of the primary incision and side ports. The nomogram takes into account cylinder magnitude, age and angle of cylinder.

With an earlier versions of the nomogram, the mean vector magnitude was 59% of intended, demonstrating under-correction. The v3 nomogram has been boosted achieving a vector magnitude of 76% of intended. Version 3 of nomogram is freely available at

A nomogram has been created to enhance accuracy of FSAK during femtosecond laser-assisted cataract surgery.