Over the last two decades, cataract surgery has made great strides resulting in safe techniques, short rehabilitation times and patient expectation of spectacle independency. However, in spite of achievements in improving intraocular lens (IOL) design and more precise biometry techniques, deviation from the target refraction and posterior capsular opacification (PCO) remain, in my view, the most frequent problems and complications in cataract surgery.

Postoperative refraction deviations may develop through the postoperative axial movement of the optic, tilt and/or decentration of the IOL.^1-3 These movements reflect the interplay between postoperative fibrotic reaction of the capsular bag and mechanical resilience of the IOL in withstanding contracting forces. It has been shown that a higher rate of IOL tilt and decentration occurs more often in high ammetropic eyes. A possible explanation for this phenomenon may be that the use of the same IOL size for all IOL powers increases the capsular tension in hyperopic eyes with a smaller capsular bag, which leads to extended axial movement of the IOL.^4-7 In addition, in myopic eyes with a larger capsular bag, the use of the same IOL size could lead to an insufficient capsular tension, resulting in asymmetric IOL fixation, capsular folds and an increased likelihood of PCO. In spite of these findings, possibly due to manufacturing reasons, it has been my experience that only IOLs with a constant overall diameter for each IOL power within the range have been commercially available – up to now.

An IOL with a difference?

The Quatrix IOL (Corneal/Croma, Austria) is a hydrophilic acrylic sharp edged single-piece preloaded IOL with a long-lasting PCO-inhibiting effect . This IOL has been modified to become the Quatrix Evolutive IOL. The total lens diameter varies linearly from 10.8 to 10.3 mm according to increased IOL power, ranging from 10 to 30 D. The haptics have been trimmed in length, whereas the optic diameter with 6 mm remains constant over all dioptre powers.

At the last ESCRS congress in Berlin we presented the results of our bilateral prospective, randomized, patient and examiner-masked study. This was conducted at the Department of Ophthalmology at the Medical University of Vienna in Austria.⁸ The aim of the study was to assess whether the modifications of the Quatrix IOL to the Quatrix Evolutive IOL have any influence on the IOL axial position, centration and incidence of PCO.

Implantation and follow-up

Figure 1: IOL in preloaded cartridge/injector device before and after folding.

Forty patients with bilateral cataract were included and randomly selected to receive a Quatrix Evolutive IOL in one eye and a Quatrix IOL in the other eye. Implantation of this preloaded IOL is shown in Figure 1. Fitting of the IOL was assessed intraoperatively, after irrigation and aspiration of the viscoelastic substance had been accomplished, with a subjective grading of the IOL rotational properties (ranging from 1 = very easy to 4 = difficult rotation).

Figure 2: Standardized digital retroillumination photographs of the two IOLs.

Follow-up examinations were made at one hour, one week, one, three and six months after surgery. We measured best spectacle corrected distance visual acuity (BSCVA) and carried out a detailed examination at the slit-lamp and anterior chamber depth (ACD) using a Visante OCT (Zeiss, Germany). Additionally, digital retroillumination photographs were taken at each examination (Figure 2).

Capsular bag interaction and IOL centration

As regards IOL capsular bag fitting, we found more dependency of IOL rotation in relation to axial length or IOL-diopters for the Quatrix Evolutive IOL than for the standard Quatrix IOL. With regard to capsular bag interaction and IOL centration both IOLs showed a good clinical performance and there was no significant difference found between the IOL types. Both IOLs showed a minimal axial movement forwards within the first week and a same movement backwards after one month postoperatively, which was probably caused by the IOL design with haptic to optic angulation of six degrees. Another typical finding was the anterior and posterior distance of the IOL optic to the capsule with both IOLs.

To conclude, our study showed that the use of an IOL with variable total diameter leads to improved fitting of IOL to capsular bag size, which in turn may reduce an incidence of IOL movement causing refractive surprises or even decentration/tilt in high ammetropic eyes. However, further follow-up will show if lower incidence of PCO will occur with this lens style in the future.

References

1. V. De Groot et al., J Cataract Refract Surg, 1997. 23(8): p. 1247-53.

2. C. Vass et al., J Cataract Refract Surg. 1999 Oct;25(10):1376-81.

3. C. Koeppl et al., J Cataract Refract Surg. 2005 Feb;31(2):348-53.

4. S. Ohmi & K. Uenoyama J Cataract Refract Surg. 1993 May;19(3):348-51.

5. K. Hayashi K et al., Ophthalmology. 2007 May;114(5):969-75.

6. M. Tehrani et al., J Cataract Refract Surg. 2003 Nov;29(11):2127-34.

7. P. Sourdille, et al Ophthalmographe Nr.29: 9-11.

8. M. Georgopoulos et al., Impact of haptic size on intraocular lens position. Presented at the 26th ESCRS, Berlin, Sept 13-17, 2008.