Dr. Samatha P Shetty, Dr.
Mathew Kurian, Dr. Luci Kaweri, Dr. Rohit Shetty
Introduction:
Subluxatedcataractous lens requiring surgery is a common scenario. In these cases, cataract extraction is followed by IOL implantation in the bag with or without capsular tension rings +/- capsular tension segments, scleral fixation, iris fixation or in rare cases placement in the anterior chamber along with anterior vitrectomy.Though many advances have been made in the surgical treatment of patients with weak or missing zonules, there is certain amount of IOL tilt or decentrationpost surgery, which can result in unhappy patients despite successful surgery(1).This can be attributed to various wavefront aberrations(2). We describe a novel technique to precisely measure the amount of IOL decentration from the visual axis and its effect on HOAs using ray tracing aberrometry
Aim:
To assess the effect of IOL tilt and decentration on visual quality following management of cases with absent or deficient capsular support
Materials & Methods:
31 cases with absent or deficient capsular support treated with either in-the-bag IOL implantation with or without capsular tension ring ±capsular tension segments or scleral fixated IOLs were included. Post-surgery,IOL tilt was measured using anterior segment optical coherence tomography and IOL decentration using Ray tracing aberrometry(iTrace, Tracey Technology)
Results:
Mean pre-operative logMAR best corrected visual acuity was 1.14±0.14 which improved to 0.24±0.68 post operatively.The mean IOL tilt of 0.20±0.21mm correlated with mean post-operative uncorrected visual acuity(p=0.049).19 eyes had decentration over 0.5mm which correlated directly with mean total astigmatism(p=0.05) and inversely with internal spherical aberration(p=0.003), Area under the Curve of the Modulation Transfer Function(p=0.008) and strehl ratio(p=0.023)
Discussion:
Statistical analysis showed that decentration correlated with total astigmatism and inversely correlated with modulation transfer function of internal optics and entire eye, regardless of the mode of IOL fixation. Thus, Irrespective of the type of complication and mode of IOL fixation, decentration of the IOL invariably has impact on quality of vision. Hence complication management should be perfect and IOL with least effect on decentration should be implanted
Conclusion:
Pre-operative IOL selection in subluxated cataracts is crucial in predicting final visual outcome
References:
1.Influence of tilt and decentration of scleral-sutured intraocular lens on ocular higher-order wavefront aberration. T Oshika, G Sugita, K Miyata, T Tokunaga, T Samejima, C Okamoto, Y Ishii. Br J Ophthalmol 2007;91:185–188
2.Influence of intraocular lens tilt and decentration on wavefront aberrations. FutoshiTaketani, ToyoakiMatuura, Eiichi Yukawa, Yoshiaki Hara. J Cataract Refract Surg 2004; 30:2158–2162