Commentary- Intraoperative aberrometry-assisted refractive optimization of SFIOL

Scleral-fixated intraocular lenses (SFIOL) are a viable surgical option to correct aphakia in the absence of adequate capsular bag or rim support. Sutureless fibrin glue-assisted SFIOLs are preferred over sutured SFIOLs owing to more predictable refractive outcomes, less IOL tilt and astigmatism, and the absence of suture-related complications.[1,2] However, refractive outcomes are still suboptimal as compared to in-the-bag IOL implantation.[1,3] The three critical factors determining the IOL power are axial length, keratometry, and effective lens position. While the measurements of axial length and keratometry are fairly reliable, an accurate estimation of the final postoperative effective lens position is the major confounding factor governing the refractive outcomes after implantation of SFIOLs.[4] Anterior or posterior shift of the IOL optic will result in a postoperative myopic or hyperopic shift, respectively. The second major determinant leading to suboptimal refractive outcomes after SFIOL is the IOL tilt, which leads to induction of significant astigmatism and higher-order aberrations, with a deterioration in the visual acuity as well as quality.[4,5] The authors report the use of intraoperative aberrometry to optimize the refractive outcomes after SFIOL implantation.[6] They offer a unique perspective to enhance refractive outcomes in a well-established surgical technique; however, the study raises several interesting questions as well. The final IOL position with SFIOL may be variable based on the position of the sclerotomy incisions and the length of haptics exteriorized. Excessive exteriorization of the haptics will result in an anterior displacement of the IOL optic and a subsequent myopic shift. Intraoperative aberrometry can provide a real-time guide regarding the amount of haptics to be exteriorized and can help optimize the magnitude of residual refractive error to target near emmetropia. In addition, an inequality in the magnitude of haptic exteriorization on both sides can induce IOL tilt, which again can be objectively corrected by using intraoperative aberrometry as a guide. The authors performed aberrometry at a sustained IOP of 30 mmHg by using a continuous fluid infusion via the pars plana route. Consistent intraocular pressure is essential to achieve accurate readings on intraoperative aberrometry.[7] However, IOL position may further change postoperatively when the physiological IOP is established in the absence of a continuous infusion. This induces a corresponding refractive shift as well. A suture is placed before obtaining aberrometry readings, which again induces corneal curvature changes and impacts the measured astigmatism. These confounding factors must be taken into account before relying on aberrometry readings to enhance refractive accuracy. In addition, the cost of acquiring intraoperative aberrometry devices may limit its widespread applicability. Limited manipulations may be performed with regard to the length of haptic exteriorization in SFIOL, and the impact of this limited manipulation on IOL position and tilt has not been objectively quantified. It may be interesting to assess the magnitude of anteroposterior displacement and IOL tilt induced by manipulating the haptics by using intraoperative imaging devices such as optical coherence tomography or ultrasound biomicroscopy. To conclude, intraoperative aberrometry may be a useful adjunct to fine-tune the anatomical and refractive outcomes while implanting an SFIOL. Various confounding factors must be taken into account, relating to the variations in the surgical technique itself, site of sclerotomy incisions, and anatomical variations in terms of white-to-white diameter. Measurements obtained using intraoperative aberrometry may also be influenced by the intraocular pressure and presence of sutures. A correlation between the changes observed on intraoperative aberrometry and the actual anatomical changes in terms of IOL position can help further establish the efficacy and utility of this technique.