Abstract
Purpose :
Standard clinical tests measure the threshold visual acuity at multiple testing distances. However, this metric does not completely describe or predict the reading performance. Reading performance has been routinely assessed by measuring reading speed with standard reading cards. The goal of this study was to describe and compare the acuity reserve, a potential predictor of reading performance in a sample of subjects implanted with monofocal and multifocal intraocular lenses (IOL).
Methods :
Post-hoc analyses of defocus curve data from two clinical trials (study 1: comparative study of a single-piece diffractive trifocal IOL (TFNT00, N=129) vs a standard monofocal IOL (SN60AT, N=111); study 2: comparative study of single-piece diffractive trifocal IOLs (TFNT00, N=93 and 839MP, N=86). Acuity reserve was calculated for each subject using two methods; Method 1 (M1): Acuity demand curve for two print sizes at 40 cm - 20/55 (0.44 logMAR) and 20/32 (0.20 logMAR) corresponding to the average font size of a text message on cellphones (Bababekova et al. 2011) and product labels (Xu et al. 2019) respectively were calculated. Acuity reserve was calculated as the vertical difference of the subject’s defocus curve and the acuity demand curve at 66 cm (-1.50 D) and 40 cm (-2.50 D). In method 2 (M2), acuity reserve was calculated as the vertical difference of the subject’s defocus curve and a standard threshold print size (0.20 logMAR) at the two viewing distances, 66 and 40 cm.
Results :
For intermediate distance (66 cm), the median acuity reserve (logMAR) to resolve 20/55 print from the two methods, M1 (M2) was: TFNT00: 0.21 (0.44), SN60AT: 0.02 (0.24), TFNT00: 0.20 (0.42), 839MP: 0.16 (0.38). For near (40 cm), the median acuity reserve (logMAR) for the 20/55 print from M1 (M2) were: TFNT00: 0.42 (0.42), SN60AT: 0.02 (0.02), TFNT00: 0.41 (0.41), 839MP: 0.38 (0.37) demonstrating sufficient reserve to read text on cellphones. For small prints (20/32), the median acuity reserve (logMAR) from M1 (M2) were: TFNT00: 0.18 (0.19), SN60AT: <0.0 (<0.0), TFNT00: 0.18 (0.18), 839MP: 0.14 (0.14).
Conclusions :
The results demonstrate better acuity reserve with the TFNT00 than the 839MP trifocal IOL for intermediate and near viewing. The acuity reserve of more than 4 lines and 1.5 lines for the 20/55 and 20/32 prints may allow fluent reading (Lovie-Kitchin et al. 1993) of text on cellphones and product labels with multifocal IOLs.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.