507 nm. In comparison, a UV blocking colorless IOL transmits only 4% more light at this wavelength. It is also important to note that the normal human crystalline lens at any age transmits significantly less light at and near 507 nm than does the AcrySof® Natural IOL and therefore, patients implanted with the AcrySof® Natural IOL should have enhanced scoptopic vision. It would be counterintuitive to believe that scotopic vision would be diminished instead of being enhanced.

A study presented at the ASCRS Annual Meeting in 2005 evaluated the detection thresholds for a Goldmann size V target at wavelengths of 410, 450, 500 nm using a modified Humphrey Field Analyzer in patients, with and without yellow clips that approximated the filtering ability of the AcrySof® Natural IOL [43]. Each test was carried out with a single wavelength of light. The results showed decreased ability to perceive objects when only 410 or 450 nm light was present, but no significant decrease in perception ability at 500 nm. This decrease was more significant in patients with ARMD. The results are exactly what would be expected, based on the light transmission spectrum of these IOLs. However, the study fails to provide insight into mesopic or scotopic vision as it does not represent mesopic or scotopic conditions. In the real life environment, there is always a spectrum of light present, not just one wavelength. This is also true of mesopic and scotopic conditions, where there is more 500 nm and longer wavelength light than 410 or 450 nm. (Fig. 8.52)

In 2008, Drs Turner and Mainster questioned the effect of blue light filtering IOLs on the circadian

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Fig. 8.52 Spectral light distribution in air under mesopic (M) and scotopic (S) conditions [44]

rhythm and perhaps, as a result, on the sleep patterns of the patients receiving these IOLs [45]. However, no peer reviewed literature could be found to corroborate their concerns. Indeed, until today, only one study seems to disprove these claims. Patel and Dacey examined the relative effectiveness of photoentrainment of the circadian rhythm by a blue light-filtering tinted intraocular lens (AcrySof Natural SN60), an UV-only filtering IOL (AcrySof SA60), compared to human lenses in four age groups. They found that with the most recently published action spectra for circadian photoentrainment, blue light filtering IOLs were significantly more effective for photoentrainment of the circadian action rhythm than with previously cited action spectra. These results suggest that the effectiveness of the blue light filtering SN60 IOLs placed in 60to 85-year-old patients would be within +6 to −13% of that in 30to 39-year-olds, and that both SN60 and SA60 IOLs should be effective for melatonin suppression under average household illumination [46]. Separately, in a recent clinical study, Landers et al. evaluated sleep patterns in 31 patients implanted with UV-only blocking IOLs and compared them to the sleep patterns of 18 patients receiving UV and blue light filtering IOLs [47]. They found no significant difference in sleep patterns between these two groups and concluded that the blue light filtering IOLs had no deleterious effect on circadian rhythm or sleep patterns.

Summary

Clinical studies demonstrate no clinically significant difference between colorless, UV-blocking IOLs and blue light filtering IOLs in terms of visual acuity, contrast sensitivity, color vision, night vision, circadian rhythm or sleep patterns.

8.3.4.5 Clinical Experience

Having implanted many thousand AcrySof® Natural IOLs, I have had the opportunity to gain insight to the quality of vision provided by this unique IOL. The visual results in my patients have been excellent without any complaints of color perception or night vision problems. I have implanted blue light filtering IOL in the fellow eye of many patients previously implanted with colorless UV-filtering IOLs. When asked to compare the color of a white tissue paper, 70% do not see a