Dear Editors

I am very interested in Drs. Hayashi and Hayashi's article entitled 'Visual function in patients with yellow tinted intraocular lenses compared with vision in patients with non-tinted intraocular lenses' that was published in Br J Ophthalmol 2006; 90:1019-1023. This is a well designed and controlled clinical study with interesting results. I have a few comments on the article to the authors as follows:

1. It is well known that pupil size and IOL tilt or decentration can significantly affect glare test results. Since this article did not report the information for IOL tilt or decentration during follow-up visits and the information for pupil sizes during the glare test, I did not know if the authors addressed these issues in their study.

2. The authors have pointed out that one of the weaknesses of this study was that 'mesopic contrast sensitivity was examined under a higher luminance level (5 cd/m²) than that typically used for mesopic vision testing (≤3 cd/m²)' and 'The second limitation of the study described here is that scotopic contrast sensitivity was not examined'. Previous studies have demonstrated that visual acuity and contrast sensitivity performed under a dim light condition are more sensitive than the results obtained under a bright light condition. A small visual benefit among aspheric IOL, yellow tinted IOL and conventional IOL may be seen under a dim light condition but not a bright light condition.

3. Currently, several manufacturers offer yellow tinted IOLs and the IOL color is not exactly the same. Therefore, the authors should mention how much blue light this IOL can block and discuss if the remaining blue light that is not blocked by the IOL can cause potential retinal toxicity long-term. Furthermore, color vision is always a concern for yellow tinted IOL implantation. This study did not perform color vision testing.

4. The authors stated, in their article, that five patients (13.9%) in the non-tinted IOL group noted cyanopsia at 2 weeks after surgery, while no patient in the yellow tinted IOL group reported this symptom. No patients in either group, however, reported this symptom at 3 months after surgery. Clinically, it is no surprise if a patient complains about bright light or different color images after cataract surgery and IOL implantation. The symptoms will go away gradually. In Drs. Hayashi and Hayashi's article, five patients with cyanopsia at 2 weeks after surgery and the symptom disappeared at 3 months after surgery. Did the patients get used to the color of the images at 3 months after surgery or were the patients not able to distinguish a difference in color at 3 months, because the second eye was operated on? The article did not report the interval of two eye surgeries.

5. Drs. Hayashi and Hayashi stated in their article that 'because in vitro studies showed that short wavelength blue light has photo toxicity for the neural retina and retinal pigment epithelial cells, and that the blue light absorbing IOL could prevent damage to the retinal pigment epithelial cells, the yellow tinted IOL is thought to contribute to the prevention of AMD. Therefore, the use of yellow tinted IOLs is recommended for eyes at high risk to develop AMD'. It is reasonable to predicate clinical outcomes based on in vitro results. It is premature to recommend yellow tinted IOL for prevention of AMD based on the in vitro results, because in vitro results are not always repeatable in clinical trials.

In summary, this study has provided additional scientific data and evidence to support the safety and efficacy of yellow tinted IOL in human eyes. But the beneficial effect of yellow tinted IOL for prevention of AMD is purely based on a theory. Clinically, it is equally difficult to prove or disprove this theory. Therefore, the debates and controversy regarding the beneficial effect of yellow tinted IOL will likely continue for years to come.

Ran Sun, MD

Bausch & Lomb, Inc.,

Rochester, NY, USA