Abstract
Purpose :
In the use of toric intraocular lens (TIOL), the axial position has been determined from the predicted postoperative corneal astigmatism. Whereas, preferable uncorrected visual acuity is obtained when the astigmatism sufficiently reduced or with the rule (WTR) astigmatisms of 1.0D or less, which indicates that there would be acceptable ranges in the axial position. This study was aimed to investigate acceptable range and examine the effect in TIOL astigmatism corrections.
Methods :
Postoperative visual acuity was least degraded when residual astigmatism satisfied a certain condition, such as the astigmatism would be close to zero (less than 0.5D) or WTR of 0.75D or less. Residual astigmatisms on the cornea were calculated with a predicted postoperative corneal astigmatism and cylindrical power of TIOLs by alternating the axial positions. Then, axial positions in which the residual astigmatisms satisfied the condition defined, were chosen for obtaining the acceptable range. For 22 eyes implanted with t-IOLs, the axis positions, keratometric astigmatism and uncorrected visual acuity (UCVA) were measured 1month postoperatively. UDVAs when the axis positions within the acceptable range or not were compared for 2 levels of misalignments: 5 degree or less and over 5 degrees.
Results :
The axis misalignment ranged in 1 to 18 degree (mean: 6.0 degree). In 11 eyes with the axis misalignment of 5 degree or less. there was an eye outside of acceptable range which resulted in degraded UDVA. On the other hand, significant difference was not found when the misalignments were over 5 degrees.
Conclusions :
This preliminary evaluation demonstrated that the acceptable ranges of the axial positions could predict the unpreferable UCVA cases, while further evaluations using sufficient samples is necessary to verifying the effectiveness. The use of the acceptable range preoperatively would allow more flexible and practical implantations of TIOL.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.