Intraoperative aberrometry-based aphakia refraction in patients with cataract: status and options

Abstract

AimTo explore the application of intraoperative wavefront aberrometry (IWA) for aphakia-based biometry using three existing formulae derived from autorefractive retinoscopy and introducing new improved formulae. Methods In 74 patients undergoing cataract surgery, three repeated measurements of aphakic spherical equivalent (SE) were taken. All measurements were objectively graded for their quality and evaluated with the 'limits of agreement' approach. ORs were calculated and analysis of variance was applied. The intraocular lens (IOL) power that would have given the target refraction was back-calculated from manifest refraction at 3 months postoperatively. Regression analysis was performed to generate two aphakic SE-based formulae for predicting this IOL. The accuracy of the formulae was determined by comparing them to conventional biometry and published aphakia formulae. Results In 32 eyes, three consecutive aphakic measurements were successful. Objective parameters of IWA map quality significantly impacted measurement variability ( p<0.05). The limits of agreement of repeated aphakic SE readings were +0.66 dioptre (D) and −0.69 D. Intraoperative biometry by our formula resulted in 25% and 53% of all cases ±0.50D and ±1.00 D within SE target, respectively. A second formula that took axial length (AL) into account resulted in improved ratios of 41% and 70%, respectively. Conclusions A reliable application of IWA to calculate IOL power during routine cataract surgery may not be feasible given the high rate of measurement failures and the large variations of the readings. To enable reliable IOL calculation from IWA, measurement precision must be improved and aphakic IOL formulae need to be finetuned.

Preoperative measurement vs intraoperative aberrometry for the selection of intraocular lens sphere power in normal eyes

“…In contrast to these results with Talbot–Moiré interferometry, Huelle et al10 found that Hartmann–Shack IA was less reliable than Preop measurements, noting difficulty in obtaining reliable measurements and high variability in readings. The number of unsuccessful attempts to incorporate IA into the cataract surgery procedure was not recorded in this study.…”

Emerging Technology in Refractive Cataract Surgery

“…The agreement of repeated aphakic SE readings ranged from −0.69 diopters to +0.66 diopters. The authors concluded that measurement precision is limiting reliability of intraoperative aberrometry and application to routine cataract surgery [ 21 ]. However, it may be useful in guiding limbal relaxing incision enhancements and has resulted in the need for fewer subsequent laser enhancements [ 22 ].…”

Cataract refractive surgery

“…35 Factors such as wound formation, hydration, and maintaining minimal eye movement or squeezing while not applying too much pressure from the eye fixating device can affect measurements. 34,35,38,39 The surgeon must guard against manipulation of the ocular structures during measurement, as altered intraocular pressure and anterior chamber depth that is not physiologically normal will not properly represent the optics of the eye during its stable post-operative state. 38,39 Observing and taking into account these factors will reduce individual variability, which can be a concern with the device.…”

“…34,35,38,39 The surgeon must guard against manipulation of the ocular structures during measurement, as altered intraocular pressure and anterior chamber depth that is not physiologically normal will not properly represent the optics of the eye during its stable post-operative state. 38,39 Observing and taking into account these factors will reduce individual variability, which can be a concern with the device. 34,38,39 Intraoperative aberrometry provides additional data to the surgeon about the refractive status of the eye when the crystalline lens has been removed and when the IOL has been implanted.…”

“…38,39 Observing and taking into account these factors will reduce individual variability, which can be a concern with the device. 34,38,39 Intraoperative aberrometry provides additional data to the surgeon about the refractive status of the eye when the crystalline lens has been removed and when the IOL has been implanted. It is intended to reduce variability in the refractive outcome after surgery.…”