Full and continuous depth of focus achieved with complementary lens system
A paired multifocal intraocular lens combination, with one lens favouring near vision and the other intermediate, intended to binocularly complement each other across a wide range of focal distances while achieving the intended goal of continuous vision, demonstrated little difference between the lenses at intermediate vision, Sheraz Daya MD said at the ASCRS Virtual Meeting 2020.
In a prospective study designed to test the patented “continuous phase” technology and the complementarity of the Artis Symbiose (Cristalens) lens system, Dr Daya implanted the intermediate, or Mid, lens into the dominant eye and the near, or Plus, lens into the non-dominant eye of 50 patients. The continuous phase technology is designed to smooth the defocus curve of diffractive lenses by correcting for phase inversions that can blur images.
All lenses were implanted through a 1.8mm scleral incision using a Victus (Bausch + Lomb) femtosecond laser. Astigmatism greater than 0.75D or more was managed with limbal-relaxing incisions, said Dr Daya, of the Centre for Sight, London, UK.
At six weeks after surgery, monocular and binocular defocus were evaluated along with contrast sensitivity. In Mid eyes, 92% were within 0.5D of target and 94% within 1.00D. In Plus eyes, 91% were within 0.5 D and 98% within 1.00D. Two percent lost two lines due to cystoid macular oedema in bilaterally and this recovered with resolution. Forty-five percent of Plus eyes and 21% of mid eyes gained one or more lines vision. Predictability was good in both cohorts, Dr Daya reported.
Uncorrected distance vision was good in both eyes, and better with both eyes open. The Plus lens performed better visually at near and intermediate range, with 52% v 45% at 20/20 near monocularly, and 62% v 57% 20/20 at intermediate. For contrast sensitivity, the Mid performed slightly better at most frequencies, Dr Daya said. However, this might be a result of better neuroadaptation due to implanting the Mid lens in the dominant eye.
In 14 patients able to participate, defocus curves showed slightly better vision at all distances for the Plus lens. The defocus curves of both lenses were stable with no dips. No patient complained about reduced intermediate vision, though two complained of lack of near vision with the Mid lens. Patients adapted rapidly to the lenses, Dr Daya said.
“Performance of both Mid and Plus lenses was good, there was no comparable loss of intermediate between the Mid and Plus lenses. There is no clear evidence the lenses complement each other and perhaps patients will do better with Plus lenses in both eyes. We have now commenced a study of bilateral Plus lenses and shall compare outcomes to this cohort,” Dr Daya concluded.
Sheraz Daya sdaya@CentreforSight.com