Take-home message: The number of presbyopia correcting options has increased along with the size of the presbyopic market. Clear lens exchange (CLE) is becoming a popular option as a result of the latest generation of intraocular lenses that have been shown to offer spectacle independence to a high proportion of patients. In this article, Mr Chitkara presents the 1-year results of his small study evaluating CLE with implantation of the Diffractiva-aA lens.
By Mr Deepak Chitkara, MBChB, DO, FRCOphth
As the size of the presbyopic market has increased, so too has the number of options for correcting presbyopia. However, clear lens exchange (CLE) is becoming increasingly popular mainly due to the advent of the latest generation of bi-, tri- or multifocal intraocular lenses (MIOL), which have been shown to provide an independence from spectacles to a high percentage of patients.
Unlike other procedures, such as laser eye surgery, the great advantage of CLE is that the results are permanent. The ability to see is enhanced with both eyes working together unlike monovision where one eye is focused for distance and one eye is used for reading. Patients therefore can have a more natural vision.
MIOLs: Not suited to everyone
Still, if MIOLs are great options for the majority of our patients, they are not suitable for everyone. Poor multifocal candidates are those who are unable to accept some potential visual compromise in exchange for an improved quality of life. It is also not an option for patients with ocular pathologies that may limit their vision such as corneal scarring or dystrophies, age related macular degeneration (AMD), and other retinal pathologies.
Low to moderate astigmatism is not an issue any longer with the recent development of toric MIOLs. Higher levels of astigmatism will require full correction either with toric IOLs as a piggyback lens and/or subsequently with laser corneal refractive surgery.
Many available options
Nowadays, there are so many presbyopia-correcting IOL models available on the European market that we can select the lens model that is the best choice for a patient. One of the models I have been routinely using since 2012 is the multifocal Diffractiva-aA from HumanOptics (Erlangen, Germany). This recently marketed single-piece hydrophilic acrylic lens (Figure 1) has a diffractive aspheric aberration-free anterior surface with a +3.5 D near addition, which ensures good functional near vision in a comfortable reading distance of approximately 40 cm.
The diffractive structure of the MIOL is constituted of 9 diffractive circular steps; the first 3 steps are of the same height and there is a gradual decrease in the 6 remaining step heights, creating a smooth transition to distance-dominant vision as the pupil enlarges. Moreover the implant has a 360-degree square edge on the posterior surface acting as an epithelial cell barrier for PCO prevention.
One-year visual outcomes
In a small study conducted at the Viewpoint Vision clinic in St Helens (UK), we have analysed the 1-year visual outcomes of 40 consecutive patients (80 eyes). All patients underwent CLE with immediate sequential bilateral clear lens surgery with implantation of the Diffractiva-aA lens to correct their refractive error and reduce dependence on glasses. Exclusion criteria included corneal astigmatism greater than 1.50 D, pupil deformation, iris abnormalities and any ocular pathology that would affect visual acuity or increase operative risks.
The mean age of our patients was 56.9 years (range 41 to 79). The preoperative refractive spherical error ranged from –8.00 to 6.25 D combined with a mean cylinder of –0.38 ± 0.34 D. The average lens power was 20.8 ± 4.5 D (range 12.0 to 30.0 D). One patient had previous myopic LASIK and one patient had forme fruste keratoconus. Target refraction was emmetropia or slight myopia.
No intra- or postoperative complications occurred and no explantations were required over the follow-up period. Looking at the one-year results, the Diffractiva-aA delivered excellent visual outcomes for our patients, with a mean postoperative monocular uncorrected distance visual acuity (UDVA) of 0.01 ± 0.10 logMAR (20/25) compared to 0.67 ± 0.44 logMAR (20/94) preoperatively (P<0.0001; paired t-test). Mean binocular UDVA was -0.04 ± 0.06 logMAR postoperatively (20/18) with 100% of patients achieving 20/25 or better including 92.1% having 20/20 or better.
The procedure was also effective at restoring near vision. Mean monocular uncorrected near visual acuity (UNVA) was 0.08±0.08 LogMAR (20/24); 100% of eyes could read J3 or better, 97.5% were J2 or better and 77.5% were J1 or better. Binocularly, UNVA improved slightly.
The importance of intermediate vision
While distance and near vision remains important, the majority of presbyopic patients cite the need for intermediate vision as a priority for their work. Therefore, the subjective appreciation of patient intermediate vision, the level of spectacle independence and overall satisfaction with the procedure were assessed with a questionnaire.
All patients reported to function comfortably without glasses for near-vision and intermediate-vision activities such as computer work, playing cards, playing the violin, cooking etc. For distance-vision activities, only one patient reported to have some difficulties although his uncorrected distance visual acuity was 20/20. Nevertheless, he was satisfied with the procedure. When asked about spectacle independence, 93% of patients reported never needed glasses and only 7% of patients chose the response ‘very rarely’ or ‘sometimes’ for spectacle use (Figure 2).
Minimal photic phenomena
Regarding subjective photic phenomena, most patients (79%) did not experience or were not disturbed by halos at night. Glare around headlights were absent or not disturbing in 90% of the cases. Only 2 patients had some difficulties to cope with glare and halos. These dysphotopsic effects, albeit undesirable, did not prevent the lens from providing a high level of satisfaction to my patients.
This is an excellent outcome knowing that patients undergoing Clear lens surgery for Refractive correction are usually more demanding regarding the quality of vision than cataract patients.
Highly satisfied patients
Beside a thorough patient selection, the most important key to postoperative success with MIOL implantation is honest patient information and education about the advantages and limits of the procedure. We caution all potential candidates that they might require a secondary procedure to correct any residual refractive or astigmatic error to obtain the best and final visual outcome. Additionally I inform all patients about the possibility of halos and glare under nighttime conditions and the need for spectacles for some tasks after surgery. As a result, we avoid patient dissatisfaction due to unrealistic expectations.
Our clinical outcomes indicate that the Diffractiva-aA MIOL is effective at providing good quality of vision resulting in highly satisfied spectacle independent patients.
Mr Deepak Chitkara, MBChB, DO, FRCOphth
Mr Chitkara is consultant ophthalmic surgeon, specialist in refractive surgery, founder and director of Viewpoint Vision Services Ltd at St Helen’s and Knowsley Hospitals NHS Trust.
Mr Chitkara has no financial interests in the subject matter.