Intraocular lens power calculation by measuring axial length with partial optical coherence and ultrasonic biometry

Abstract

RESUMO Objetivo: Comparar os resultados refracionais obtidos em pacientes submetidos à cirurgia de catarata com cálculo da lente intraocular realizado por meio de biometria ultrassônica de imersão (US) ou por interferometria de coerência parcial (ICP ABSTRACTPurpose: To compare the achieved refractive outcomes of patients undergoing cataract surgery with intraocular lens (IOL) power calculation performed by conventional immersion ultrasound (US) or partial coherence interferometry (PCI). Methods: Prospective, comparative case series. Patients undergoing cataract surgery were randomly divided in two groups with regard to the IOL power calculation method. Group 1 had calculations performed by PCI (IOL Master; Carl Zeiss Meditec), while US was used in Group 2 (Ultrascan; Alcon), using the Holladay 1 formula. Differences between target and achieved refractions were then compared. Results: The study comprised 120 eyes from 79 patients. Biometry with PCI was used in 50 eyes of 33 patients, and US was used in 70 eyes of 46 patients. Mean age of patients in the PCI Group was 69.8 ± 13.1 years (range 11 -85) and 70.0 ± 9.3 (45 -86) in the US Group (P=0.7165). Mean axial length measured by PCI was 23.22 ± 1.00 mm (range 21.01 -25.45) and that by US was 23.22 ± 1.06 mm (20.05 -25.78) (P=0.9110). Mean absolute error in the PCI group was 0.15 ± 0.33 D (range -0.65 -0.9) and that in the US group was 0.26 ± 0.48 D (-1.05 -1.76). All eyes in the PCI group and 94.3% of those in the US group were within 1.00 D of the planned refraction. Conclusion: Although both PCI and US yielded good prediction in IOL power calculation, the PCI group tended to show better accuracy and improved refractive outcome.

<p>Comparison of Biometry Measurements Using Standard Partial Coherence Interferometry versus New Scheimpflug Tomography with Integrated Axial Length Capability</p>

“…The IOL Master 500 uses the principle of partial coherence interferometry, and its successor, the IOL Master 700, incorporates optical coherence tomography. 14,15 Both devices produce similar results, but the latter has been shown to have higher accuracy for posterior subcapsular and dense cataracts. 7 The IOL Master projects six light spots onto the cornea in a hexagonal pattern to assess anterior corneal curvature and performs measurements using a 2.3-mm radius.…”

Ophthalmic ultrasound of dogs with different skull conformations

“…The correlation with refractive error is larger for axial length than for any other component (Mutti et al, 2007;Fontes et al, 2011). Considering the increasing number of cataract surgeries with intraocular lens placement performed daily in veterinary facilities, it becomes important to know the axial length measurements for different skull conformations.…”

Optimising biometry for best outcomes in cataract surgery

“…16,17 If immersion ultrasound was adopted as the second-line investigation for eyes in which optical biometry fails, then outcomes could be improved from 82.5% within ± 1 D of target 10 to between 85.7 and 94.3%. 18,19 The impact of such improvement on the patient population as a whole is dependent upon the proportion requiring ultrasound biometry; assuming a rate of 10% then between 0.3 and 1.2% more eyes overall could achieve within ± 1 D of target as a result of this change in practice.…”