Posted: Tuesday, July 16, 2013

With multifocal intraocular lens near vision adds ranging from +2.5 to +4.0 D now available, the question arises: how much is enough? The answer depends on several factors, including reading habits and even language, Hiroko Bissen-Miyajima MD, Tokyo, Japan, told the American Society of Cataract and Refractive Surgery Symposium. She suggests reading the literature first, but listening to patients is critical to sorting out which lens is best for whom.

Different power, different vision

Dr Bissen-Miyajima, who is a consultant for Hoya, has long experience implanting a variety of multifocal lenses with different add powers. To illustrate the differences, she presented a clinical study she and colleagues at the Tokyo Dental College Suidobashi Hospital did comparing +4.0, +3.0 and +2.5 D add versions of the diffractive Alcon ReSTOR single-piece acrylic lens. In Europe, the lenses were introduced in 2005, 2008 and 2012, respectively. All versions delivered 1.0 or 20/20 visual acuity at distance, with the +4.0 delivering the best near visual acuity but the worst intermediate vision, and the +2.5 the best intermediate and worst near vision. Less than five per cent of patients implanted with the +4.0 required reading glasses for small print, compared with more than 50 per cent implanted with the +2.5 needing reading glasses, Dr Bissen-Miyajima reported.

So, if the +4.0 lens provides the best near vision and highest possibility of spectacle independence, why is the trend in new lenses towards lower near add power? “Because patients require good distance vision. The trade-off for a higher near add is reduced distance vision quality, with lower contrast sensitivity and more glare and haloes. While the +2.5 D add provided the best quality distance vision of the three, it was not as good as a monofocal, leaving some patients complaining of ‘waxy’ vision,” Dr Bissen-Miyajima explained.

An adequate add

Dr Bissen-Miyajima counselled discussing with patients the trade-offs between more add power and distance vision quality before surgery. Reading habits and even the language in which patients read are important, she noted. For example, Japanese people tend to read at a distance closer to 30cm than 40cm, and Japanese characters are more detailed, requiring better visual acuity to read than Roman alphabet used in English and most other European languages, Dr Bissen-Miyajima noted. As a result, many Japanese prefer a +4.0 add. On the other hand, her husband reads closer to 50cm and mostly in English, so a +3.0 is fine for reading and provides better intermediate and distance vision. +3.0 is the most commonly implanted power in the US, she said. Those receiving +2.5 lenses should be informed they will likely need reading glasses for small print.

A patient’s strong desire for multifocal lenses may even overcome typical clinical parameters for using them, Dr Bissen- Miyajima added. She normally would not implant a multifocal in a one-eyed patient. But she did implant one in the left eye of a 97-year-old man with 0.1 or 20/200 in his right eye due to optic nerve atrophy following intracapsular cataract surgery 30 years before. He achieved 0.9 or about 20/22 at distance and 0.7 or about 20/30 after surgery – and was thrilled. “He had a strong wish for modern technology,” Dr Bissen-Miyajima said. “The final answer is: One size does not fit all.”