[Effects of posterior chamber phakic intraocular lens on axial length measurements].
OBJECTIVE
To study the effects of posterior chamber phakic intraocular lens (IOL) on axial length (AL) measurements and whether a correction factor for later IOL power calculation before cataract surgery is necessary.


METHODS
Twenty-two high myopic patients (39 eyes) with mean spherical equivalent -19.00 +/- 4.03 D received phakic refractive lens (PRL) implantation, and 24 patients (40 eyes) with mean spherical equivalent (-13.10 +/- 2.53) D received implantable Collamer lens (ICL) implantation. Pre-and postoperative AL measurements with the IOLMaster were compared. Results The pre-and postoperative ALs were (30.87 +/- 2.18) mm and (30.94 +/- 2.16) mm, respectively (t = -2.635, P = 0.012) in the PRL group, and (28.35 +/- 1.20) mm and (28.45 +/- 1.22) mm, respectively ( t = -3.97, P < 0.001) in the ICL group. Linear regression analysis showed: in the PRL group, preoperative AL = 1.01 x postoperative AL-0.24 (R2 = 0.99, P < 0.001), or postoperative AL--preoperative AL = 0.24-0.0055 x postoperative AL; in the ICL group, preoperative AL = 0.96 x postoperative AL +1.17 (R2 = 0.99, P < 0.001), or postoperative AL--preoperative AL = 0.0154 x postoperative AL -0.3763. The mean differences between pre-and postoperative ALs in the PRL and, ICL groups were 0.075 mm and 0.054 mm, respectively.


CONCLUSIONS
Based on the SRK formula, a < 0.1 mm AL difference would result in a <0.25 D change in the calculated IOL power, possibly a < 0.20 D change in manifest refraction. Furthermore, for PRL, the longer the AL, the smaller the difference between pre-and postoperative ALs. These differences are so small that it is unnecessary to correct IOL power calculation.
Ayong
A
Yu
Qinmei
Q
Wang
Shuangqian
S
Zhu
Anquan
A
Xue
Yanfeng
Y
Su
Rui
R
Pan
D002387:Cataract Extraction; D005123:Eye / Q000033:anatomy & histology*; D006801:Humans; D019654:Lens Implantation, Intraocular; D007910:Lenses, Intraocular; D016014:Linear Models; D009216:Myopia / Q000628:therapy*; D019990:Perioperative Care; D054120:Phakic Intraocular Lenses; D011184:Postoperative Period; D014787:Vision Tests; D014792:Visual Acuity