Investigating IOLs

September 9, 2012

On the first day, IOLs were the key focus at the ESCRS free paper sessions…

Automated keratometry and aspheric IOL combo successful


A combination of automated keratometry and an aspheric aberration-correcting IOL is successful in treating cataracts, explained Dr Hoffman in the Toric IOL Alignment lecture yesterday.
The investigation included 80 eyes of 58 cataract patients who underwent toric IOL implantation between January 2011 and September 2011. The spherical and cylindrical section of the IOL was calculated using a Lenstar data set and a TMS5 topography that employs a Placido system for the anterior surface and a Scheimpflug system for the posterior surface.
The Lenstar data set included axial length, corneal thickness, internal chamber depth, lens thickness and automated dual zone keratometry. Sphero-cylindrical refraction was based on corneal data predicted by full-aperture ray-tracing procedures. The outcome measures were spherical prediction error (SPE) and cylindrical prediction error (CPE).
Mean distance-corrected visual acuity (DCVA) was 20/23 and mean achieved manifest refraction was +0.01 spherical -0.41 cylindrical. For all patients the mean absolute error was 0.27 D, 0.20 D for eyes with a visual acuity (VA) of 20/20 or better and 0.33 D for eyes with a VA of worse than 20/20.
Mean CPE in eyes with 20/20 vision or better was 0.48, 0.48, 0.47 and 0.43 D in eyes that underwent Lenstar keratometry, TMS5 anterior topography, TMS5 anterior and posterior topography and combined Lenstar and TMS5 data, respectively.
Dr Hoffman commented, "The predominant use of aspheric aberration-correcting IOLs led to the predictive accuracy of spherical and cylindrical refraction, with a better results than reported in previous studies. Keratometry was less likely to produce user errors and dry eyes, whereas topographic data was more likely to be influenced by measuring tolerances and outliers."
Automated ketatometry worked well when combined with Placido and Scheimpflug topography, in conjunction with an aspheric aberration-correcting IOL.

Pupil size affects lens selection


Pupil size must be considered when selecting IOL design for each patient, revealed Dr Gil at the Multifocal IOLs Comparitive Data lecture.
The longitudinal prospective study included 200 patients randomized to receive five different IOLs. The ReSTOR SN6AD1 was implanted in 40 patients, the ReSTOR SN60D3 in 40, ReZoom NXG1 in 40, Tecnis ZMA00 in 40 and the Tecnis ZA9003 in 40 patients.
Monocular corrected and uncorrected distance visual acuity, monocular distance corrected and uncorrected near visual acuity and monocular distance corrected and uncorrected intermediate visual acuity were all assessed three months after IOL implantation. TNO and Titmus tests were used to determine stereoacuity and standardized questionnaires were used to evaluate subjective quality of vision and life.
The results demonstrated the need to measure pupil sizes. For distance focus in patients with small pupils the apodized diffractive IOL designs significantly improved visual acuity, compared to IOLs with spherical aberration correction.
There were no significant difference between the lenses in distance visual acuity, but near acuity was inferior with the ReZoom lens. However, the best intermediate distances were achieved with the ReZoom.
All multifocal lenses had reduced contrast sensitivity, particularly at high spatial frequencies. Patients implanted with monofocal lenses provided a better contrast sensitivity and stereoacuity outcomes. Multifocal lens selection relies on considering the optical characteristics of the lens design.

Multifocal IOL corrects all VAs


Two IOLs are able to correct distance, intermediate and near vision for presbyopia and cataracts, announced Dr Noel Bauer during an earlier lecture.
Dr Bauer introduced his paper, "Visual function after bilateral implantation of presbyopia-correcting multifocal IOLs; Restor vs Mplus", at the Multifocal IOLs Comparitive Data free paper session.
The clinical trial involved 24 cataract patients with less than 1.00 D of corneal astigmatism. Each participant was randomized to receive bilateral implantation of the Oculentis Mplus IOL or the AcrySof IQ ReSTOR multifocal IOL. Refractive and visual outcomes were recorded preoperatively and postoperatively at one and three months.
For the ReSTOR IOL the mean distance-corrected near visual acuity was 0.03 logMAR three months postoperatively, compared to the Mplus IOL group at 0.08 logMAR.
Overall, there was no significant difference in postoperative corrected or uncorrected (binocular) distance, intermediate and near visual acuity postoperatively, and the binocular defocus curves were similar.

Positive results for electronic toric marker


A new electronic toric marker can complete axis marking easily and accurately in cataract surgery, discussed Dr Akahoshi in the Toric IOL Alignment lecture.
Two different electronic toric markers were compared on patients. The electronic reference marker was used to complete the two-step method in conjunction with an intraoperative axis marker. The electronic axis marker completes the procedure in a single action. The sensitivity of the electronic level can be changed in five steps, ranging from the most sensitive point of 0.2 degrees and the most insensitive point from 2.0 degrees.
With the standard marker the surgeon had to stay alert to avoid misalignment and ensure the marker was in the correct position, whereas the electronic toric marker had three modes that indicated the horizontal position of the instrument. If the device is incorrectly positioned then LED lights will flash and an alarm will sound.
The new electronic toric marker reduced, or even eradicated, the chances of misalignment and is easier to use. However, the electronic reference marker is helpful in cases with narrow lids or deep-set eyes.

Manual marker secure and simple


A manual marker is secure, simple to use and efficient for cataracts and corneal astigmatism, proves Dr Shimoda at the Toric IOL Alignment lecture.
Dr Shimoda presented the prospective study, entitled "Refractive results on 418 eyes following implantation of toric lens using manual marker", yesterday. The investigation included 418 eyes with cataract and corneal astigmatism between 1.00 D and 6.00 D.
Axial length and anterior chamber depth were measured with the IOLMaster, the orbscan was used to complete topography and the incision axis and lens axis were recorded. The postoperative measurements were refraction and visual acuity.
Mean residual refractive was -0.32 D and residual cilindric was -0.35 D. The lens had to be repositioned in one patient in order to correct the axis. Another patient required spectacles.As well as being a safe, simple, fast and inexpensive procedure, using a manual marker allows the surgeon to mark the entire 180 degree, incision and lens axis.

Pupil dilation influences IOL position


Degree of pupil dilation influences IOL position, reveals Prof Wolffsohn's study featured in the free abstract session Pupil Management and Phaco Tips.
Professor Wolffsohn presented the findings of his study "Stability of pupil dilation following cataract surgery" during yesterday's lecture. The investigation covered 204 patients across six European sites.
All eyes were dilated using phenylephrine 2.5% and tropicamide 1.0%, with pupils imaging after 30 minutes using a digital slit-lamp biomicroscope at the operative visit and 1-2 days, 7-14 days, 30-60 days and 120-180 days at follow-up.
After cataract surgery a significant inferior shift in pupil centration was observed over time, but there was no change in horizontal centration. IOL centration was stable with respect to the limbus, but was vertically decentrated compared to the pupil.
Pupil width and height were both significantly larger after surgery and the ratio between them was significantly altered.
“This research confirms that when the pupil is pharmacologically dilated for cataract surgery it cannot be used as a satisfactory guide for centration,” concluded Professor Wolffsohn.
“The limbus is a better guide, although the pre-dilation pupil decentration relative to the limbus also needs to be taken into account when positioning an IOL. Such knowledge becomes even more critical when premium IOLs are to be implanted because of their more complex optical designs which can cause a significant reduction in visual quality if they are not perfectly centred. In addition, research is warranted into the development of new surgical IOL implantation techniques and IOL materials and designs that to not impair the dilation response.”