Abstract
This study compared the optical axial length (AL) obtained by composite and segmental methods using swept-source optical coherence tomography (SS-OCT) devices, and demonstrated its effects on the post-operative refractive errors (RE) one month after cataract surgery. Conventional AL measured with the composite method used the mean refractive index. The segmented-AL method used individual refractive indices for each ocular medium. The composite AL (24.52 ± 2.03 mm) was significantly longer (P < 0.001) than the segmented AL (24.49 ± 1.97 mm) among a total of 374 eyes of 374 patients. Bland–Altman analysis revealed a negative proportional bias for the differences between composite and segmented ALs. Although there was no significant difference in the RE obtained by the composite and segmental methods (0.42 ± 0.38 D vs 0.41 ± 0.36 D, respectively, P = 0.35), subgroup analysis of extremely long eyes implanted with a low power intraocular lens indicated that predicted RE was significantly smaller with the segmental method (0.45 ± 0.86 D) than that with the composite method (0.80 ± 0.86 D, P < 0.001). Segmented AL with SS-OCT is more accurate than composite AL in eyes with extremely long AL and can improve post-operative hyperopic shifts in such eyes.
Highlights
This study compared the optical axial length (AL) obtained by composite and segmental methods using swept-source optical coherence tomography (SS-OCT) devices, and demonstrated its effects on the post-operative refractive errors (RE) one month after cataract surgery
These differences arose from changes in technology and measurement compatibility with intraocular lens (IOL) power calculation formulas
Since the segmental method with the ultrasound immersion technique is more accurate than the composite method with the ultrasound contact technique, we speculated that the optical measurements with the segmental method would be more precise than the conventional ones with the composite method
Summary
This study compared the optical axial length (AL) obtained by composite and segmental methods using swept-source optical coherence tomography (SS-OCT) devices, and demonstrated its effects on the post-operative refractive errors (RE) one month after cataract surgery. A second generation anterior segment swept-source optical coherence tomography (AS-OCT) was recently developed[10,11,12]. This novel, but commercially-available, AS-OCT system has an improved scan rate, depth capacity, and density assessment, allowing for sharper images of the anterior and posterior surfaces of the cornea, crystalline lens, and IOL. A newly introduced optical biometer that is based on swept-source optical coherence tomography (SS-OCT) has been shown to generate repeatable and reproducible measurements[13,14,15,16]
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