Vector planning delivers superior outcomes for myopic astigmatism
Excimer laser treatments using vector planning resulted in less corneal astigmatism, less refractive cylinder, and better unaided visual acuity postoperatively than treatments using manifest refractive treatment parameters alone, according to Noel Alpins, MD.
Reviewed by Noel Alpins, MD
In eyes with myopic astigmatism undergoing LASIK, use of an ablation plan based on vector planning instead of the manifest refraction results in better astigmatic and visual outcomes, said Noel Alpins, MD.
“More than 60% of LASIK procedures involve correction of astigmatism, and commonly there is a difference between the astigmatic parameters measured on the cornea and the refraction,” said Dr. Alpins, medical director, NewVision Clinics, Melbourne, Australia.
Vector planning
Benefits of vector planning were demonstrated in a prospective study including 160 consecutive eyes. Eyes were eligible for inclusion if they had an ocular residual astigmatism (ORA, vectorial difference between corneal and refractive astigmatism expressed in diopters and degrees) >0.75 D and corrected distance visual acuity of 20/25 or better.
All procedures were performed by Maria Clara Arbelaez, MD, at the Muscat Eye Laser Clinic, Muscat, Oman, using the same excimer laser (Amaris Total-Tech, Schwind) and femtosecond laser for flap creation (LDV, Ziemer). The first 80 eyes were treated using vector planning, and in the second half of the series, LASIK was performed using the manifest refraction alone (“conventional LASIK”).
Treatment parameters for vector planning were calculated using the ASSORT program v5.50 (ASSORT PTY) and were designed with a 60% emphasis placed on the refractive astigmatism and a 40% emphasis placed on the corneal astigmatism. The 40/60 emphasis is based on previous studies that showed this to be the “sweet spot.”
An emphasis anywhere between 50/50 and 30/70 is considered to be optimum, Dr. Alpins noted.
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