Logical approach

The complexities of human psychology play a far more important role in the decision-making process concerning key questions of retinal detachment (RD) management than we might imagine, Bill Aylward FRCS, FRCOphth, told delegates attending his Kreissig Lecture at the 15th EURETINA Congress in Nice, France.
In a wide-ranging lecture on “A logical approach to retinal detachment”, Dr Aylward, past president of EURETINA, touched on topics as diverse as scurvy, mathematics, psychology and the flawed nature of current scientific tools in explaining why it is so difficult to resolve some of the more intractable questions surrounding RD.
The questions to which Dr Aylward referred included: ‘Does laser treatment to lattice degeneration reduce the lifetime risk of RD?’; ‘What is the best treatment for rhegmatogenous retinal detachment (RRD)?’; and ‘Does shaving the vitreous base increase the success rate of vitrectomy for RRD?’ 
These questions are not resolved for a variety of reasons, including the subject matter, tools and human and psychological factors, said Dr Aylward, UK.
In terms of scientific tools, Dr Aylward cited a scale of evidence starting with the “gold standard” of randomised controlled trials, followed by cohort studies, case control studies, case series, and expert opinion. 
Taking the example of lattice degeneration and whether laser treatment might reduce the lifetime risk of RD, Dr Aylward said that while this question could be resolved with a randomised clinical trial, in reality it is not so easy.
“We know that the annual incidence of RD is 0.01 per cent, and if we assume that the laser works and cuts the detachment rate by 50 per cent, the number of patients required is over 7,000 in each arm of the trial. And because we are treating young people, we need to wait until they have had their posterior vitreous detachment, so we would need a 40-year follow-up. Clearly this is never going to happen,” he said.

BEST TREATMENT
Turning to the best treatment for RD, Dr Aylward said that while everyone agrees on the mechanisms and surgical principles concerning RD, there is still wide divergence on the best methods to achieve this.
“The biggest determinant is where the surgeon trained – so it will be vitrectomy in the UK or scleral buckle in the USA, and so forth,” he said. 
A study of surgical trends for RD in the UK in 2001 showed vitrectomy growing in popularity, said Dr Aylward, “not for any scientific reason but for a number of practical reasons, specifically facility with the procedure, internal searching and wide-angle viewing systems which appeared to make the surgery easier.”
In 2007, a robust study by Heimann et al comparing scleral buckling versus primary vitrectomy in RRD concluded that there was better vision with buckling in phakic eyes and better primary success with vitrectomy in pseudophakic eyes. 
“Did that make a difference in clinical practice? Well we see in a 2015 survey from Moorfields Eye Hospital that vitrectomy is still far more popular than scleral buckling. So there is a general problem that randomised trials do not always influence practice,” he said.
To illustrate the point, Dr Aylward cited James Lind’s 1753 study on scurvy among sailors – the first ever recorded randomised controlled trial (RCT) – which showed the beneficial effect of citrus fruits in preventing the disease. The Royal Navy ignored Lind’s findings for 42 years, he said.
Dr Aylward said more expertise-based RCTs were needed in the future, as opposed to clinical trials where the same surgeon performs a less preferred surgical option on half the patients. 
Statistics, a discipline which is “difficult and non-intuitive”, should also be treated with caution.

REGISTRIES HELP
Registries help in removing some of the known biases from the data, said Dr Aylward, with advances in technology meaning that prospective collection of detailed clinical data is now possible.
“This deals with known biases, though not unknown ones. The output is not as good as an RCT, but better than nothing,” he said.
Psychology also plays an important role in the decisions that physicians make in terms of treatment, said Dr Aylward. 
“I am glad to say that psychology is now being taught at some medical schools. I think we also need a healthy scepticism about our beliefs and training, and need to apply a little bit more logic to our thinking,” he said.
Dr Aylward cited issues such as confirmation bias – the tendency to search for, interpret, favour and recall information in a way that confirms one’s beliefs or hypothesis – as posing a problem for logical decision-making. Similarly, physicians should be aware of the “sunk cost fallacy” by which future decisions are inappropriately influenced by past investment. 

Bill Aylward: bill@aylwards.co.uk