Reply: Intraocular lens power calculation in phacovitrectomy patients
I would like to respond to Partwardhan's constructive comments. First, Partwardhan recommends the use of fourth-generation IOL formulas such as Holladay II and Haigis to calculate a patient's specific ELP. I agree with the comments and may consider using these formulas in future IOL calculations for combined surgery. However, further studies comparing the various formulas would be required to prove their validity in this specific group of patients. To our knowledge, other authors1,2 reporting the refractive outcomes after combined surgery have used the SRK/T formula as a standard.
Second, Partwardhan commented on the postoperative myopic shift in our group of patients and recommended preoperative and postoperative biometry to determine whether the gas bubble had displaced the capsular bag forward. I evaluated the postoperative posterior vitreous length (PVL) in 18 of the study patients (unpublished data). The PVL showed a mean increase of 3.19 mm (from 15.83 mm preoperatively to 19.02 mm postoperatively). However, after adjusting the axial length (axial length measured in the aphakic mode and adjustment for central thickness of the IOL and sound velocity in the specific pseudophakic lens), the findings were inconclusive. Of 18 patients, 11 showed a mean decrease of 0.45 mm in the postoperative axial length compared with the preoperative value. The remaining 7 patients were noted to have increased by a mean of 0.43 mm. As the study is small and retrospective, I would like to report the above findings conservatively.
In conclusion, I hope that a future prospective randomized control trial may be able to provide answers to the issues discussed above and provide guidance for the management of patients having combined surgery.
1. Suzuki Y, Sakuraba T, Mizutani H, et al. Postoperative refractive errors after simultaneous vitrectomy and cataract surgery. Ophthalmic Surg Lasers. 2000;31:271-275.
© 2008 by Lippincott Williams & Wilkins, Inc.
2. Jeoung JW, Chung H, Yu HG. Factors influencing refractive outcomes after combined phacoemulsification and pars plana vitrectomy: results of a prospective study. J Cataract Refract Surg. 2007;33:108-114.