Hideki Nakamura

Correction of Residual Refractive Error in Pseudophakic Eyes with the Use of a Secondary Piggyback Toric Implantable Collamer Lens

PURPOSE To evaluate the feasibility of piggyback insertion with a toric Implantable Collamer Lens (ICL, STAAR Surgical). METHODS This study investigated eight pseudophakic eyes of five patients who underwent piggyback insertion of a toric ICL to correct residual refractive error. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and manifest refractive sphere and astigmatism were measured before and 6 months after surgery. RESULTS Pre- and 6-month postoperative logMAR UDVA were 0.759±0.430 and 0.201±0.458, respectively. All eyes were corrected within ±0.50 diopters (D) of intended spherical equivalent refraction. The manifest refractive astigmatism was within ±0.50 D in five (62.5%) eyes and ±1.00 D in seven (87.5%) eyes. No eyes lost more than one line of CDVA. Pupillary block occurred in one eye on postoperative day 1. CONCLUSIONS Piggyback insertion of a toric ICL appears to be effective and predictable in correcting refractive error in pseudophakic eyes.

Intraocular lens power calculation in cases with posterior keratoconus.

Purpose To compare the calculation errors of intraocular lens (IOL) power in patients with posterior keratoconus and to determine which corneal refractive power is suitable for these calculations. Setting Chukyo Hospital, Nagoya, Japan. Design Retrospective case series. Methods This retrospective chart review was performed to identify eyes diagnosed with posterior keratoconus using anterior segment optical coherence tomography (AS‐OCT). The keratometry (K) values were measured using an autokeratometer and partial coherence interferometry (PCI) (IOLMaster). The AS‐OCT measured the total refractive corneal power and the anterior to posterior corneal curvature (A/P) ratio. Predicted refractive errors were calculated from K values based on the postoperative subjective refractive errors. Results The chart review of 4621 eyes found that 4 eyes of 4 patients (mean age 74.8 years ± 13.0 [SD]) were diagnosed with posterior keratoconus. The total refractive corneal power values were the smallest among all of the corneal refractive powers in all 4 eyes. The preoperative A/P ratio was 1.45 (Case 1), 1.26 (Case 2), 1.25 (Case 3), and 1.44 (Case 4). When the PCI measured K values were applied for the IOL power calculations, all of the eyes became hyperopic with postoperative refractive errors of +1.51 diopters (D) (Case 1), +0.34 D (Case 2), +0.97 D (Case 3), and +1.08 D (Case 4). When the total refractive corneal power values were applied, the errors were +0.10 D (Case 1), −0.18 D (Case 2), −0.61 D (Case 3), and −0.65 D (Case 4). Conclusion The real corneal power values that take both the anterior and posterior corneal curvatures into consideration should be applied for IOL power calculations in cases with posterior keratoconus. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.

Effect of Background Luminance Level on the Assessment of Color Visual Acuity Using Colored Landolt Rings in Young Healthy Subjects

ABSTRACT Purpose: To evaluate the color visual acuity (CVA) of young healthy subjects using colored Landolt rings and the effect of background luminance level on the CVA. Materials and methods: We measured the CVA of 20 young healthy subjects (age: 23.8 ± 3.8 years) with different colors using a computer and a liquid crystal display, with 15 Landolt ring colors (30 cd/m2) with a background luminance of 30 cd/m2, and then 100 cd/m2. We then used different background luminance levels (15–50 cd/m2) using four Landolt ring colors (red, green–yellow, green, and blue–green) to evaluate the effect of the background luminance level on CVA. Results: The CVA significantly differed among the colors with a background luminance of 30 cd/m2 (p < 0.0001). Green–yellow and blue–purple had poor CVA (high LogMAR value; 0.808 ± 0.107 and 0.633 ± 0.150, respectively) with a background luminance of 30 cd/m2 (same luminance as the Landolt rings). There were no significant differences in the CVAs among the colors with a background luminance of 100 cd/m2 (p = 0.5999). There were no significant difference in the CVA between background luminance 30 cd/m2 and other luminance level ranging from 28 to 32 cd/m2 for colors of red, green–yellow, green, and blue–green. Conclusions: The results reveal that the background luminance of Landolt rings affects the CVA. Distinctive CVAs for each color are measured by equalizing the luminance between the Landolt ring and the background. We consider that the poor CVAs of these colors reflect the visual function of S-cone, because GY and BP are included in the confusion locus of tritan axis on the chromaticity diagram. We believe that CVA assessment may be useful for individuals who have known or suspected ocular dysfunction or color vision deficiencies.