A deeper look at the lens
How visual outcomes can be optimised in cataract patients
Gerd Auffarth MD
Despite all the advances in technology and surgical techniques, post-cataract surgery visual issues persist in some patients and must be dealt with honestly and practically while continuously striving to improve outcomes, said speakers during the ‘20/20 in 2020: The Lens’ symposium during the 38th Congress of the ESCRS.
Gerd Auffarth MD, Germany, discussed restoring accommodation with IOLs. The reality is that there are not any real accommodative lens in use currently, but there are some promising developments, including fluid lenses that change curvature; “which is more rewarding than changing the position of the lens as you can achieve a real amount of accommodation with that,” he said.
Looking further into the future, Dr Auffarth said work is ongoing on lenses utilising artificial intelligence (AI) and ‘bionic IOLs’ that looks interesting, but clinical data is awaited, while he also questioned the use of the capsular bag as the standard location for accommodative lenses.
Dr Béatrice Cochener-Lamard MD, France, spoke about the goal of “super vision”, which she explained goes far beyond just visual acuity: “It is not about 20/20 and zero refraction vision but rather good quality vision whatever the surrounding light conditions.”
She stressed the importance of choosing the right lens for the right patient and gathering the necessary data about their visual needs, noting that smartphone and computer usage have increased substantially in recent years.
Beyond the key metric of spectacle independence post-surgery, Prof Cochener-Lamard said it is important to conduct an objective, wide-ranging evaluation when assessing post-op eyes. She outlined a number of useful assessments and questionnaires (eg, contrast sensitivity, reading speed, halometry etc): “There are now a wide range of options to quantify the quality of vision, which have allowed a better understanding of optical aberrations.”
Prof Cochener-Lamard added that ocular surface issues are also an important consideration, with thorough pre-op assessment key to explain risks to the patient and to avoid post-op complications, with presbyopia correction more challenging in this regard than corneal refractive surgery. Indeed, with ageing, risk factors for ocular dryness accumulate, whereas multifocal optics and even EDOF are more sensitive to the degradation of light diffusion and the sensitivity of contrasts that can be induced by an unstable tear film.
Similarly, Giacomo Savini, Italy, warned against overpromising results to patients before surgery, during his talk entitled ‘The Quest for Emmetropia’. About 15% of eyes after surgery will have a prediction error of >0.5D and patients with multifocal lenses should be advised that laser touch-up may be necessary in about 10% of cases to reach emmetropia, he said, so “if this happens then patients will not complain”
There is very little difference among the refractive results based on measurements from the current range of optical biometers: “the prediction error of <0.5D is generally between 80-85%. This is not surprising as all manufacturers follow the measurements of the original IOLMaster to be able to use the ULIB constants,” Dr Savini said. However, the newer optical biometers have other advantages, such as swept source OCT having the ability to penetrate through dense and subcapsular cataracts he noted. Scott MacRae MD, USA, highlighted the success of early studies on novel femtosecond laser-induced refractive index change for IOL touch-ups, which he explained is biocompatible, relatively non-invasive and can treat refractive error, presbyopia and high-order aberrations. “We are very, very excited about this technology and look forward to presenting more information in the future.” Also speaking during this session, Gregorius Luyten MD, the Netherlands, said that positive and negative dysphotopsia can occur in up to 20% of patients following uncomplicated cataract surgery, and “and I think it is important that we acknowledge to the patient that their symptoms are real”. Positive dysphotopsia is more likely to occur with multifocal lenses while negative dysphotopsia occurs immediately after uncomplicated cataract surgery, with normal in-the-bag implantation, he explained. Quoting the recent ESCRS vRESPOND study, Dr Luyten said the root causes of negative dysphotopsia could be due to significant geometrical differences – these patients tend to have a smaller pupil diameter, decentred pupil centres and tilted iris plane than controls. Treatments for persistent pseudophakic dysphotopsia include piggyback IOL implantation and secondary reverse capture, but mostly involve exchanging the IOL, he said. In terms of avoidance, perfect centration of the lens is key, as is putting haptics in the horizontal position, and using larger optics (6.5 or more), Dr Luyten recommended, reiterating that IOL exchange with a larger optic size has up to a 100% success rate. Speaking about correcting astigmatism at the time of cataract surgery, Adi Abulafia MD, Israel, said toric lenses are becoming the standard of care for these patients but the results are not always predictable. He outlined seven key tips to improve toric IOL outcomes including validating data, looking at the corneal topography and optimising the ocular surface; using several measuring devices, taking into account the posterior corneal astigmatism, being alert for unusual corneas; accounting for the corneal surgically induced astigmatism; optimising toric IOL alignment and having a low threshold for performing toric IOL calculations.