Unexpected rotation of the implant is the likely source of refractive surprises between one and three years after implantation of toric implantable contact lens (TICL)

Session Details

Session Title: Phakic IOLs

Session Date/Time: Sunday 23/09/2018 | 08:00-10:00

Paper Time: 09:38

Venue: Room A3, Podium 1

First Author: : S.Patel UK

Co Author(s): :    M. Bohac   A. Biscevic   M. Koncarevic   N. Gabric           

Abstract Details

Purpose:

To determine if any residual astigmatism following correction resulted from A) unexpected angular rotation (often referred to as the angle of error) of the toric implant or B) potential error in the astigmatic power of the implant in cases where postop refractive cylinder was ≥ 0.75DC at 1 to 3 years postop.

Setting:

University Eye Clinic ‘Svjetlost’ Zagreb & ‘Svjetlost’ Split. Croatia

Methods:

Pre-and postoperative refractive data at 1,2&3 years postop were analysed for 196 complication free cases implanted with TICL (EVO+ Visian ICL, Staar Surgical, Nidau, Switzeland). The pre-op refractive error (sphere and cylinder) ranged from -1.00DS to -22.25DS & -0.50DC to -5.50DC. Refraction data were subjected to vector analysis for the final estimation of the angle of error [θ°] representing the difference between the angle of the attempted astigmatic correction (often referred to as the target induced astigmatism or TIA) and the angle of the actual astigmatic correction (often referred to as the surgically induced astigmatism or SIA).

Results:

Key results at 1,2&3 years respectively were a)The number of cases presenting with astigmatism ≥ 0.75DC was: 24 (12.2%), 19 (9.7%) and 17 (8.7%) of the 196 cases. b)θ°(mean±sd) =+5.8° (±18.7), +2.1° (±17.1) & -8.3° (±27.4). Positive values represent clockwise rotation and vice versa. Difference between θ values at 1&3years was significant (p= 0.031). c)There was a significant linear relationship between [I]SIA(y)&TIA(x) power where at 1year y=0.847x-0.272(r=0.819,n=24,p<0.01), 2years y=1.025x+0.195(r=0.879,n=19,p<0.01), 3years y=0.746x-0.555(r=0.774,n=17,p<0.01), [II]sine of SIA angle(y1) &sine of TIA angle(x2) where at 1 year y1=0.564x2+0.128(r=0.673,n=24,p<0.01), 2years y1= 0.483x2+0.153(r=0.484,n=19,p=0.036), 3 years y1=0.774x2-0.144(r=0.614,n=17,p<0.01).

Conclusions:

Approximately 9-12% of cases present with ≥ 0.75DC of astigmatism following correction using TICL. The linear regression equations resulting from our analysis predict, the difference between SIA and TIA powers are mainly less than 0.50DC. The likely source of residual astigmatism is an unexpected rotational misalignment of TICL. On average this misalignment is initially in the clockwise direction and reverses towards anticlockwise between 1 and 3 years postop.

Financial Disclosure:

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