DEC 09, 2019
Cataract/Anterior Segment, Refractive Mgmt/Intervention, Retina/Vitreous
This retrospective study examined factors impacting refractive outcomes after combined phacoemulsification and pars plana vitrectomy (phacovitrectomy).
Researchers identified 76 patients who underwent cataract surgery (n=34), phacovitrectomy without gas tamponade (n=20) and phacovitrectomy with gas tamponade (n=22). They used swept-source anterior segment OCT to measure parameters of the anterior chamber and lens. Refraction was measured postoperatively at 1 week and 1 month.
The mean median absolute error and refractive prediction error were greater in the phacovitrectomy with gas tamponade group than the other 2 groups (0.47 D and -0.82 D, respectively). The refractive prediction error indicated a greater myopic shift in eyes receiving gas tamponade. Forward movement of the IOL position correlated with a greater refractive predictive error at 1 month (P<0.001).
Eyes receiving gas tamponade also had a shallower postoperative aqueous depth at 1 month, even after gas resolution. Although the IOL position at 1 week and 1 month moved significantly forward with gas tamponade (both P<0.001), the degree of IOL tilt was only significantly larger at 1 week (P=0.004). There were no differences in IOL decentration among the 3 groups.
This study was limited by its retrospective design, a relatively small sample size and a short study period. Minor differences in the extent of vitreous base shaving in each patient may have potentially influenced the zonular laxity, thereby affecting the position of the IOL.
This study demonstrates the importance of keeping in mind the possibility of a myopic shift in eyes undergoing phacovitrectomy. The current study shows that gas pushes the IOL forward for at least 1 week after vitrectomy, causing it to tilt and move forward—resulting in a shallow aqueous depth. As the gas spontaneously decreases over time, the pushing power of the gas weakens but the IOL does not return to the same position as eyes that did not received a gas tamponade. The postoperative aqueous depth was shallower and the IOL was fixed in a forward position even after gas resolution, leading to the postoperative myopic shift.