Retina 2007 (page 3)
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Blue blocking benefits?
Moving away from the treatment of AMD and on to potential causes: the blue light debate has continued to raise eyebrows and stir emotions this year. Specifically, the debate continues around whether intraocular lenses (IOLs) that block blue light are beneficial because they protect the retina from damaging blue light. Alternatively, might they present a risk because, some feel, that blue light is essential for retina health?
There is still uncertainty over whether or not blue light is a catalyst for AMD progression. Questions also remain unanswered regarding the effect of blue blocking IOLs on scotopic vision and, more importantly, their potential disturbing effects on the diurnal rhythms that are necessary for good health. No experiment to date has demonstrated the efficacy of blue light blocking IOLs in protecting against retinal damage; it may never be irrefutably proven either. The fact is that the prevalence of AMD is on the increase and steps are consistently being taken to protect the retina from known and suspected environmental AMD risk factors, such as smoking, light and diet. Whether or not blue light blocking IOLs will fit into a surgeon's AMD prevention toolkit still remains to be seen. At present, it appears that those surgeons opting to implant these lenses are doing so out of preference and personal belief rather than as a result of conclusive evidence.
"…we need some rationale
for using them. Maybe a
retrospective analysis will help to clear
some uncertainty surrounding the utility
of these lenses"
"I have implanted many blue filtering lenses without any significant side effects," remarked Professor Augustin. "I do, however, acknowledge that we need to see some rationale for using them. Maybe a retrospective analysis will help to clear some uncertainty surrounding the utility of these lenses," he added.
It is Professor Augustin's belief that blue light blocking lenses do not adversely affect colour vision, night vision or contrast sensitivity. Nor, in his opinion, do the lenses alter sleep patterns. "The amount of light reaching the retina during blue filtering lens implantation is still sufficient for all physiological functions," he said.
According to Professor Rizzo, these lenses should be considered as a reasonable option, particularly in eyes at high risk of macular degeneration development. "In my experience, I have seen no evidence to suggest that these lenses induce an inflammatory reaction or alter visual function. I usually implant blue light filtering foldable IOLs during combination cataract and vitrectomy surgery for macular disease. I would stress that fundus visualization with these lenses, even when dealing with vital dyes, is excellent," he added.
Dr Stefansson concedes that balancing the beneficial effects of blue light on the retina with the harmful effects is very difficult. "Blue and UV light have been shown to be damaging in laboratory studies, but the clinical significance is less certain. The data for light-induced cataract is pretty clear, but AMD less so. There is a way to get around this problem, and that is by using colour spectacles that protect against UV and blue light. Those people who are high-risk AMD candidates, should also increase their intake of zinc and vitamins," he advised.
Surgery: minimal invasion equals minimal destruction
The trend to go smaller with surgical instruments and techniques affects virtually every healthcare discipline. Vitreoretinal surgery is certainly no different, and recently the procedure has undergone a series of revisions, allowing for smaller incisions that potentially enhance patient comfort and do not require sutures. Indeed, minimally invasive vitrectomy surgery (MIVS) has been heralded as one of the most significant, recent, developments in the field.
"My expectations have been
completely fulfilled by MIVS. In fact, I
can manage the majority of my cases
now using 23- and 25-gauge
surgery. The performance of the new
23-gauge cutters is outstanding"
"I am convinced that MIVS is one of the most exciting options that has been made available to us in recent years. It is advantageous for patients, in that it allows a faster recovery and less postoperative discomfort," enthused Professor Rizzo.
"I fully agree that both MIVS and the combination of anti-cytokine therapy with vitrectomy has improved our surgical options," added Professor Augustin.
Professor Rizzo also noted that the addition of anti-VEGF therapy as a preoperative adjunct to pars plana vitrectomy (PPV) also improves the prognosis in complicated cases.
20G, 23G or 25G? That is the question
In terms of instrumentation, today's surgeon can now opt for the larger 20-gauge systems, which require sutures, and 23- and 25-gauge systems, which do not. Certainly, making the procedure sutureless marked a significant step forward in the practice of vitreoretinal surgery. Indeed, it was believed that the new, lean 25-gauge instruments, which allowed the creation of self-sealing incisions, answered the wishes of vitreoretinal surgeons. Certainly, these instruments remain useful, however, more and more surgeons have begun to approach them with caution because of difficulties and complications that have emerged since their introduction onto the market.
Ironically, the very slim design of 25-gauge instruments has contributed to its steady downfall. Specifically, the thinner design of the instruments has resulted in increased flexibility and bending, making surgery more difficult to perform. Furthermore, a study published in 2004 in the American Journal of Ophthalmology actually reported a case of a 25-gauge vitrectomy cutter snapping off during surgery.2
In response to these concerns, the intermediate-size 23-gauge instruments were launched, thus allowing surgeons to still enjoy the benefits of MIVS, whilst addressing any problems they may have encountered either with the larger 20-gauge or the smaller 25-gauge instruments.
"I employ 23- and 25-gauge MIVS as standard in my surgery and have even extended my use of 23-gauge instruments to complex vitrectomy cases requiring silicone oil endotamponade," explained Professor Rizzo. "I have limited my use of 20-gauge surgery to extremely complicated cases only, for example, when dealing with cases of anterior proliferative vitreoretinopathy (PVR), which have membranes that are so thick and adherent to the retina, that they require bimanual dissection. Only 20-gauge tools at present have the cut and aspiration efficiency suitable for their removal," added Professor Rizzo.
Professor Augustin is also equally impressed with the 23-gauge systems. "We introduced 23-gauge MIVS earlier this year. We now use this system in 90% of our vitrectomy procedures," he enthused. "As with Professor Rizzo, we do still use 20-gauge instruments in silicone oil cases and very complicated surgeries," Professor Augustin advised.
Concerns over the risk of endophthalmitis with both the 23- and 25-gauge procedures have been raised, because sutureless incisions provide a temporary window for opportunistic pathogens. In spite of this, MIVS has taken the place as the vitrectomy procedure of choice in the majority of surgeries.
"I was not happy with 25-gauge
instruments, largely because of the
flexibility of them. I was also
unimpressed by the fluidics and I
think it is far too risky for beginners
to perform 25-gauge surgery"
"My expectations have been completely fulfilled by MIVS. In fact, I can manage the majority of my cases now using 23- and 25-gauge surgery. The performance of the new 23-gauge cutters is outstanding. Because the opening of the cutter is on the end of the tip, we are able to work in very close proximity to the retina. Moreover, MIVS fluidics are safer," said Professor Rizzo.
According to Professor Rizzo, he has been particularly impressed by the speed in which he can now perform surgery, particularly because there is less need for tool exchange. "Combination surgery can also be performed easily and safely with MIVS. In addition, I can manage lens dislocation in the vitreous chamber by performing 25-gauge vitrectomy, injecting perfluorocarbon liquid (PFCL), lifting the lens in the anterior chamber and removing it by performing phacoemulsification through a clear corneal tunnel," he added. He also referred to the 25-gauge xenon chandelier fibre light, which has allowed him to perform the bimanual technique during MIVS with greater ease.
Professor Augustin countered, "I was not happy with 25-gauge instruments, largely because of the flexibility of them. I was also unimpressed by the fluidics and I think it is far too risky for beginners to perform 25-gauge surgery." He added, "I am, however, really happy with 23-gauge surgery; I now perform the majority of my surgeries with these instruments."
