Dr. Jai Gopal Agrawal, A05995
PURPOSE :-
To compare the outcome, the prediction error, the rotational stability and the patients satisfaction in post operative cataract cases using either conventional toric IOL(Alcon modified –L haptic) calculated by Alcon toric calculator with consideration of Anterior corneal astigmatism only, toric IOL(Alcon/Care) calculated by Barrett toric calculator or customized toric IOL(plate haptic type) calculated by Barrett toric calculator.
The Barrett Toric Calculator provides the best toric IOL prediction methods available
METHOD:-
CALCULATION:-
IOL master was used for measurements — K readings, AL, ACD and White to white corneal diameter.
Toric IOL calculations were done by
— Online Alcon toric calculator alone without considering PCA , or with
— Online Barrett toric calculator.
Toric IOL used:- a) Alcon toric IOL(modified –L haptic),
b) Plate haptic type IOL, ordered by us to Care toric IOL manufacturer co. This plate haptic IOLs were based on power calculated by Barrett toric calculator and the calculated cylinder at desired axis is incorporated inside optic of the plate haptic lens, but axis to be positioned were marked at 180 so that the Lens were placed horizontally ( 0 to 180).Plate heptic were ordered to design with antirotational heptic pads, this ensures that there should be no rotation of IOL inside capsular bag.
PATIENTS:-
In this study, we retrospectively evaluate the case records of pts operated between Jan 2012 to Mar 2016 using one of the above mentioned methods for calculation ; while the surgeon and measuring device of corneal astigmatism ( IOL master ) remaining the same in all cases.
We considered those patients who were undergone uneventful cataract surgery, post operative corrected distance visual acuity of 6/9 or better at least 45 days after surgery, post operative measurements with IOL master at least 45 days after surgery (same day as the manifest refraction).
Post operative toric IOL axis alignment measured by Slit lamp.
We excluded those patientts who had previous ocular trauma/surgery, intra operative and post operative complications, contact lens wearers.
Eyes were grouped as “with the rule” (WTR) or “against the rule”(ATR); and targeted versus achieved astigmatic outcomes were compared. In predicted residual astigmatism, mean absolute error, median absolute error and centroid error are calculated for each method (Statestica outcome).
In thirtyfour patients, fortysix eyes were implanted Alcon IOL(modified –L haptic) calculated when role of PCA was not known. In twentyeight patients, twentyseven eyes were implanted toric IOL(modified –L haptic ) calculated by Barrett toric calculator. In fourteen patients, seventeen eyes were implanted customized toric plate haptic IOL based on specially designed above criteria.
Postoperative manifest cylinder was compared to preoperative predicted error by each method. Degree of rotational error and patients satisfaction were measured after three months .
RESULTS:-
Median absolute errors in predicted residual astigmatism were lowest with customised toric IOL with Barrett calculator for both ATR and WTR(Median value varies 0.27D to 0.22D); followed by Alcon IOL (p<.001) and Care IOL (p<.001) with modified L- haptic toric IOL with Barrett calculator for both ATR and WTR(Median value varies 0.47D to 0.41D) . Median value were highest(Median value varies 0.67D to 0.63D) when PCA were not considered i.e. without Barrett calculator.
Rotational stability & issue of axis were analysed by centroid residual astigmatism prediction error (D) +/-SD for WTR and ATR. Customised toric IOL with Barrett calculator had lowest centroid error/ lowest SDs(Centroid +/-SD(D) 0.26@81+/-0.31 to 0.21@17+/-0.35).
All data were analysed by Anova test to test significance with 95% confidance interval, which was significant.
CONCLUSION:-
So during calculation of Toric IOL, it is essential to consider PCA in all cases ; and the most accurate prediction of residual astigmatism was achieved by Barrett toric calculator.Our use of new customised toric IOL using Barrett calculator achieved the best significant rotational stability, accuracy and patient satisfaction as compared to conventional toric IOL.