Supplementary IOLs are available from the following manufacturers: Rayner (Sulcoflex range), 1stQ / Medicontur (AddOn range), Cristalens Industrie (Reverso), and Morcher (XtraFocus pinhole supplementary IOL). Details are summarised in Tables 1 and 2.

Table 1 Currently available sulcus-fixated supplementary IOLsTable 2 Power ranges for currently available sulcus-fixated IOLs

In addition, HumanOptics used to market the Aspira range of supplementary IOLs. These were three-piece silicone IOLs, available as aspheric, toric and multifocal models and achieved good clinical results as reported in a number of studies.[46,47,48,49,50,51,52,53] This range has now been discontinued and is no longer available.

The Morcher XtraFocus is an opaque disc with a pinhole 1.3mm opening, usually applied for the correction of irregular astigmatism due to keratoconus, pellucid marginal degeneration, perforating corneal trauma, other corneal irregularities or following radial keratotomy or PK (penetrating keratoplasty). The small aperture blocks most peripheral aberrated rays and the pinhole effect can extend the depth of focus which may be helpful for the correction of presbyopia.[54, 55] It is included here for completeness.

A low level of complications has been reported for these four IOLs. These include dysphotopsia, transiently raised postoperative intraoperative pressure, and mild cases of pigment dispersion that did not require treatment. No cases of iris chafing, or ILO were reported.

See Table 3 for a summary of all the studies referred to in this section.

Table 3 Published studies of sulcus-fixated IOLsThe Sulcoflex range (Rayner, Worthing, UK)

The Sulcoflex range of supplementary IOLs, see Figure 1 (a to h), has been designed to overcome the disadvantages that arise when conventional capsular bag IOLs are placed in the ciliary sulcus.[16] They are available as monofocal, monofocal-toric and trifocal supplementary IOLs. The bifocal refractive multifocal and multifocal-toric models have been discontinued in most markets.

Fig. 1

The range of Rayner sulcus-fixated supplementary IOLs

The one-piece hydrophilic design withstands the stress of implantation through a small incision, minimising haptic damage.[56] It has been reported that three-piece IOLs are more likely to lose their “memory” after implantation, causing a shift of the IOL optic. Although these results were obtained from IOLs placed in the capsular bag,[72, 73] laboratory studies confirm that one-piece PMMA lenses exhibit better loop memory compared to three-piece.[74, 75]

The posterior concave design of the Sulcoflex is intended to minimise contact between the optical zones of the two IOLs. A study using Scheimpflug photography to measure the distance between a primary and the secondary Sulcoflex IOL demonstrated that there was a good distance which was maintained over the course of the study between the two IOLs which will significantly reduce the risk of ILO.[56]

In the same study, ultrasound biomicrography (UBM) was used to assess the distance between the Sulcoflex IOL and the iris-pupil edge. Pigment dispersion can occur when the optic margin or haptics chafe the iris pigment epithelium. The UBM images confirmed that the ten-degree angulation of the Sulcoflex keeps the optic at a safe distance from the iris,[56] and this is confirmed by clinical experience. The undulating design of the haptics may also contribute to the stability of the IOL, optimising centration and rotational stability.[56]

Optical quality

Łabuz et al (2021) used ray-tracing simulations to assess the effect of the position of an aberration-neutral Sulcoflex IOL on visual performance.[76] The Sulcoflex had a nominal power of 1 to 10 D and was positioned with a capsular IOL of 20 D. The optical performance was tested for misalignment through the area under the modular transfer function (MTFa). There was good tolerance to a 1.0 mm decentration with a loss of MTFa of only 2% for the 10 D Sulcoflex. An extreme 10° tilt would result in a 4% reduction of the MTFa for a 10 D sulcus-fixated IOL, with the impact of off-axis position becoming less noticeable in eye models requiring lower-power supplementary lenses. When misaligned, low-power sulcus-fixated IOLs might retain optical quality more efficiently than a high-power capsular-bag lens, but an extreme tilt has a more detrimental effect on performance than a 1.0 mm decentration.

In an optical bench study, Łabuz et al (2020) compared the MTF and US Air Force (USAF) target images of an aberration-neutral Sulcoflex Trifocal (703F) implanted with an aberration-neutral RayOne Aspheric RAO600C monofocal IOL to that of a capsular bag-fixed aberration-neutral RayOne Trifocal IOL (RAO603F, all from Rayner Intraocular Lenses Ltd).[77] Equivalent results were found for both approaches. The presence of two IOLs rather than one led to a minimal light loss of 1.3% through reflection at additional interfaces, material absorption and light scattering.

Stability and clearance

McIntyre et al (2012), using high frequency ultrasound assessment in cadaver eyes already implanted with an IOL in the capsular bag, demonstrated that the Sulcoflex had good centration and minimal or no tilt. The Sulcoflex IOL could be injected and positioned in the ciliary sulcus, giving a clearance between the two IOLs of 232 to 779 µm, depending on the thickness of the primary IOL. The results showed that the design of the IOL minimised the possibility of interaction with the primary IOL and uveal tissues.[59]

Centration

Prager et al (2017) confirmed the stability of the Sulcoflex in 48 eyes of 43 patients.[61] After a mean follow-up of 25 months the mean decentration of the Sulcoflex IOL was 0.23 ± 0.02 mm. The mean decentration of the capsular bag IOLs was significantly greater at 0.29 ± 0.02 mm relative to the limbus.

Sulcoflex Aspheric 700L (formerly 653L) – aberration neutral monofocal optic

Kahraman and Amon (2010) implanted the Sulcoflex 700L prospectively in 12 eyes of 10 patients requiring correction of residual refractive error.[56] Correction of refractive error was safe and predictable with an improvement in uncorrected distance VA (UDVA) in all cases. There were no signs of pigment dispersion, iris bulging, foreign body giant cell formation, or ILO. There was one case of minor decentration thought to be due possibly to the eye having a large ciliary diameter and weak zonular support.

In another small series, 15 eyes with relatively high residual refractive errors were implanted with the Sulcoflex 700L (13) and the Sulcoflex 653T, now known as the 710T (2).[58] After a mean follow up of 14 months, there was good visual acuity in all patients and predictable refraction. There was no decentration, rotation or tilt in the aspheric lenses.

Venter et al (2014) report a larger study of 80 eyes that had become ametropic following initial multifocal IOL implantation with the Lentis Mplus MF30.[62] Patients with a refractive cylinder of less than 1.0 D were included, and a Sulcoflex Aspheric supplementary IOL ranging from -2.50 to +4.5 D was implanted. At one year, both sphere and cylinder had reduced significantly with 94% of eyes within ±0.50 D of emmetropia, and statistically significant improvements in UDVA and corrected distance visual acuity (CDVA). Implantation of the supplementary IOL did not affect reading performance of the multifocal IOL.

Key points: a monofocal aspheric supplementary IOL in the sulcus can be used to correct a residual refractive error after the implantation of a multifocal IOL in the bag. The Sulcoflex Aspheric 700L supplementary IOL is stable in the eye with minimal tilt, decentration or rotation. This IOL provides good visual acuity and predictable refraction. Studies have found a low level of complications, particularly relating to ILO and iris touch.

Sulcoflex Multifocal 653F (discontinued in most markets)

Khan and Muhtaseb (2011) successfully implanted four bifocal Sulcoflex Multifocal IOLs and one toric, in five eyes of four patients requiring improvement of their original post-operative vision. All patients had significantly improved UDVA and good uncorrected near VA (UNVA).[43]

Schrecker et al (2014) implanted the bifocal refractive Sulcoflex Multifocal 653F IOL in 35 eyes, and the diffractive MS 714 PB Diff in 33 eyes following implantation of an acrylic IOL in the bag.[51] The IOLs were implanted in a single procedure. At 3 months there was no difference between groups in UDVA or CDVA and both performed well in terms of far, intermediate and near visual acuity. Sixteen out of 19 patients were satisfied or very satisfied with their vision, at all distances and in all lighting conditions. There were more photic phenomena reports in the Sulcoflex patient group but these were mostly rated as mild to moderate. The unfolding process for the Sulcoflex was smoother and more controllable.

The Sulcoflex Multifocal was discontinued in most markets following the launch of the Sulcoflex Trifocal 703F in 2018.

Key points: implantation of the bifocal refractive Sulcoflex Multifocal 653F IOL in the sulcus improves intermediate and near visual acuity.

Sulcoflex Toric 710T (formerly 653T) – aberration neutral monofocal toric optic

Falzon and Stewart (2012) report that the Sulcoflex Toric IOL is predictable in adjusting post-operative refractive results and reducing spectacle dependence for distance following surgery.[16] In their retrospective case review of 15 eyes, mostly implanted with the Sulcoflex Toric IOL, all patients were within 1.00 D of attempted correction, and 93% within 0.50 D. Astigmatic error was significantly reduced and there were no significant complications.

In a study of ten eyes, Ferreira et al (2015) implanted the Sulcoflex Toric IOL to correct residual astigmatism.[31] Patients had received an IOL in the capsular bag at least 6 months previously, and the refractive error was stable. Good visual results were obtained in all patients: refractive error was significantly reduced and visual acuity improved. There was a statistically significant reduction in ocular aberrometry values and improved photopic contrast sensitivity. This study also provides evidence for the stability of this supplementary sulcus-fixated toric IOL. At 6 months, mean axis misalignment was 3.0 ± 2.45°. As one degree of rotation can lead to a loss of up to 3.3% of cylinder power,[78] this is considered an excellent result by the authors. In difficult cases, where the IOL persists in rotating, as in, for example, cases of irregular sulcus anatomy, the Sulcoflex Toric can be rotated or fixed with transscleral sutures.[79]

McLintock (2019) carried out a retrospective chart review of the Sulcoflex Toric implanted in 51 eyes, including 19 with a history of corneal grafts, with at least 3 months follow-up.[60] Mean UDVA improved significantly but more so in eyes without corneal grafts. Most patients achieved SE within ±0.5 D of target and cylinder. Sixty-two percent required re-positioning, following this, mean rotation was 6.17°.

Key points: residual astigmatism can easily be corrected with the supplementary Sulcoflex Toric IOL. Studies demonstrated good stability, leading to minimal misalignment and loss of cylinder power. The intervention is particularly useful for patients not suitable for corneal refractive surgery.

Sulcoflex Trifocal 703F – aberration neutral trifocal optic

Kahraman et al (2021), evaluated 40 eyes of 20 patients implanted with a monofocal IOL in the capsular bag and a supplementary diffractive Sulcoflex Trifocal IOL (703F).[57] All patients required an improvement in their visual acuity and had a desire for spectacle independence. At 6 months, visual acuity was good at all distances and all patients reported full spectacle independence. The IOL provided good levels of functional visual acuity over a wide range of defocus values (-3.00 to +0.50 D). Photic phenomena occurred in some patients but were not disturbing. Mean patient satisfaction was 9.21/10. No adverse events were reported for any patients and there was no rotation or tilt. All implanted supplementary IOLs had a base power of 0.00 D, near addition of +3.50 D and intermediate addition of +1.75 D.

In patients scheduled for cataract surgery or refractive lens exchange, Baur et al (2022) carried out combined implantation of the Sulcoflex Trifocal 703F IOL in 25 patients (48 eyes) with implantation of various IOLs in the capsular bag to achieve reversible trifocality.[45] At 3 months, they reported excellent results for far, intermediate and near vision which are comparable to results reported for capsular bag-fixated trifocal lenses. Monocular defocus curve testing found a visual acuity of 0.2 logMAR or better from +0.75 to −3.5 D. There was one case of decentration which required suturing. All patients who completed the assessment reported halos and more than two-thirds of patients reported glare.

In a case report concerning an 18 year old patient with bilateral hereditary hyperferritinaemia-cataract syndrome, a monofocal IOL was implanted in the capsular bag to achieve emmetropia, and a supplementary trifocal IOL in the ciliary sulcus.[80] The supplementary trifocal IOL can easily be removed at a later stage if necessary. A similar procedure was carried out on a young cataract patient with bilateral central posterior shell opacity.[81]

Key points: The Sulcoflex Trifocal IOL was stable in the eye and provided good levels of functional visual acuity over a range of distances. As is often the case with trifocal IOLs, photic phenomena were experienced by many patients but were generally not disturbing.

The AddOn range (1stQ GmbH, Mannheim, Germany)

The AddOn range of IOLs are single piece devices composed of hydrophilic acrylic. They have four square-shaped haptics and a large optic designed to avoid pupillary capture along with round edges to minimise iris chafing, see Figure 2.[67]

Fig. 2

They are available as monofocal-spherical, monofocal-toric, multifocal (bifocal diffractive), multifocal-toric and trifocal, with different power additions including low add, or extended depth of focus versions. The term “AddOn” has sometimes been used loosely in the published literature to mean any supplementary IOL, so caution is needed in interpreting studies to ensure that the IOL is part of the 1stQ range.

Stability

Reiter et al (2017) implanted the 1stQ AddOn supplementary IOL into the ciliary sulcus of 12 cadaver eyes that had previously been implanted with a range of capsular bag IOLs. Assessment with anterior segment optical coherence tomography (AS-OCT) found the AddOn to be well centred in all eyes. Four cases of tilt were seen: three with mild tilt due to pre-existing zonular dehiscence, and one due to a localized area of Soemmering’s ring formation. Mean distance between the two IOLs was 0.68 mm (0.34 to 1.24). Overall the IOL demonstrated proper fixation and centration.[67]

AddOn Spherical / Toric IOL

Gundersen et al (2017) carried out a chart review of 46 eyes implanted with the supplementary spherical or toric AddOn IOL and a variety of primary IOLs. Following implantation of the supplementary IOL, there was a statistically significant improvement in UCVA of about 2 lines, with no change in BCVA and a significant reduction in the absolute magnitude of the residual spherical equivalent refractive error. In the ten cases with a toric secondary IOL, there was a statistically significant reduction in astigmatism. The IOL provides a viable surgical option to correct residual refractive error after primary IOL implantation and performance was unrelated to the identity of the primary IOL.[64]

Gundersen et al (2020) evaluated eighteen eyes with secondary implantation of the AddOn toric supplementary IOL at least one month after surgery. Mean residual refractive astigmatism was significantly reduced. All patients had very good visual acuity. There was little change in orientation since implantation with mean absolute lens rotation of ≤5°: 89% of eyes had a lens rotation of ≤10° and only two eyes had a lens rotation of more than 10°.[65] The authors concluded that lens rotation was minimal.

Key points: the 1stQ AddOn spherical IOL improves visual acuity and reduces residual SE while the toric model can significantly reduce astigmatism.

AddOn Progressive 677MY (Trifocal IOL)

Palomino-Bautista et al (2020) implanted the 1stQ AddOn trifocal supplementary IOL in 18 eyes of 11 pseudophakic patients requiring improved spectacle independence.[42] All patients had previously undergone uncomplicated implantation of monofocal capsular bag IOLs. Of interest is that the mean time after implantation of the primary IOL was 11.4 years. After surgery, 83.3% of eyes had spherical refractions within ±0.5 D of emmetropia and 100% of eyes had spherical equivalent refractions within ±1.0 D of target refraction. Visual acuity and defocus curves confirmed the trifocal nature of the IOL which was superior in intermediate and near ranges compared to a trifocal capsular bag IOL. All patients achieved spectacle independence at all distances. All AddOn IOLs were well positioned in the ciliary sulcus. The authors conclude that the supplementary trifocal AddOn IOL is a safe, efficient and stable solution for achieving spectacle independence in pseudophakic patients.

Albayrak et al (2021) implanted the AddOn trifocal supplementary IOL in a prospective study involving 28 eyes of 18 patients who had been implanted with a primary IOL in the previous year.[63] Mean UNVA improved significantly and results for intermediate VA were good. Twenty-five eyes had a residual SE within 1.0 D of target refraction. Contrast sensitivity was unaffected. All patients had better visual function and quality scores compared to pre-operative values, with the highest improvement being seen in near vision.

Harrisberg et al (2023) carried out a retrospective analysis of patients implanted with a trifocal AddOn (A4DW0M) secondary to implantation of a toric or non-toric monofocal in the bag, comparing the results to those obtained from a single capsular bag multifocal.[66] They concluded that the IOL was effective and safe in correcting distance and near vision and increasing spectacle-independence. There were no significant differences between the groups in any parameter.

Khoramnia et al (2023) performed a laboratory analysis of a trifocal AddOn (A4DW0M) in a polypseudophakic model with a monofocal lens compared to a trifocal IOL (B1EWYN) in the capsular bag.[82] The MTF Strehl ratio was measured, and the USAF-target images were assessed. The polypseudophakic system yielded a better optical quality at far focus, while the standard trifocal provided improved imaging at near distances. The differences arose from different diffractive patterns between the two models; however, visual inspection of the resolution chart did not reveal noticeable image-quality loss confirming the equivalence of the two approaches.

Key points: the AddOn Progressive trifocal IOL from 1stQ provides predictable and stable refraction, good visual acuity at all distances and a high rate of spectacle independence.

Reverso (Cristalens International SAS, Lannion, France)

The Reverso multifocal IOL (see Figure 3) was implanted in a primary procedure along with a capsular bag IOL, into the eyes of 27 patients undergoing cataract surgery, and seeking presbyopia correction.

Fig. 3

The Cristalens Reverso® IOLs

[68] At one year, there was improvement in uncorrected distance and near vision, a high level of patient satisfaction and a low level of complications.

XtraFocus pinhole IOL (Morcher GmbH)

The XtraFocus pinhole IOL offers a different approach to correction of residual refractive errors but tends to be used in eyes with high corneal aberration, irregular astigmatism, or large or irregular pupils.

The XtraFocus IOL is composed of black hydrophobic acrylic which blocks visible light but is transparent to infrared light to permit retinal examination. The central section is 6 mm in diameter including the occlusive section, with a concave‑convex design and no refractive power, see Figure 4.

Fig. 4

The Morcher XtraFocus pinhole supplementary IOL

In the middle is a central opening of 1.3 mm, and the IOL has an overall diameter of 13.5 mm. The haptics are rounded, polished and undulating and are 250 μm thick to avoid uveal tissue injury and are angulated at 14° to prevent iris chafing and pigment dispersion. The XtraFocus received the CE mark in 2016 and is commercially available in several countries.[54]

Applications

In patients with clear central corneas, the Xtrafocus can neutralise high amounts of corneal aberration and extend the depth of field for presbyopia correction. Patients with significant dysphotopsia from multifocal IOLs or severe glare and light sensitivity from irregular or large pupils may also benefit.[54] The device is helpful in pseudophakic patients with irregular astigmatism causing significant visual impairment,[70] and can also be beneficial in patients with large iris defects.[71]

Secondary indications are near or intermediate vision enhancement in pseudophakes with monofocal IOLs, and dysphotopsia reduction in eyes with multifocal IOLs.[69]

Clinical studies

There are a limited number of clinical reports for the XtraFocus. Trindade et al (2017) implanted the XtraFocus to correct irregular corneal astigmatism in 21 patients with significant visual impairment due to keratoconus, radial keratotomy or penetrating keratoplasty, traumatic corneal laceration, post‑LASIK ectasia, and eccentric excimer laser ablation. There was marked improvement in visual function and high patient satisfaction following surgery.[70]

Ho et al (2022) implanted the XtraFocus in 11 patients with irregular corneal astigmatism, or with iris trauma. The device was implanted at the same time as a capsular bag IOL, but all XtraFocus IOLs were implanted in the sulcus. The procedure was effective at improving vision or reducing glare but two patients had to have the device explanted because of severe glare.[69]

The XtraFocus was implanted in 32 eyes of 16 patients with irregular corneal astigmatism and BCVA worse than 20/50 in both eyes. Patients had undergone surgery either for clear lens exchange or due to cataract. The IOL was found to be safe, and effective, bringing about significant improvement in visual acuity.[71] Note: in just over half of the cases, both primary and supplementary IOLs were implanted in the capsular bag. The results for the two procedures are not reported separately.

A publication in 2020 reported a retrospective study of 60 eyes implanted with the device to treat irregular corneal astigmatism.[83] However, in this study, the device was implanted in the capsular bag alongside a variety of other IOLs so will not be considered here. The authors state that this IOL is less stable in the sulcus compared to placement in the capsular bag.

To summarise, IOLs designed for use in the ciliary sulcus have been specifically designed to overcome the disadvantages that arise when conventional capsular bag IOLs are used in this way.

Important features of the Sulcoflex range are a posterior concave design to minimise contact between the optical zones of the two IOLs and sufficient angulation of the haptics to keep the optic at a safe distance from the iris. The AddOn range employs a different design with four square-shaped haptics and a large optic intended to avoid pupillary capture. Rounded edges on the haptics are a common feature of both IOLs to minimise iris chafing. The XtraFocus supplementary IOL is a pinhole device intended for the correction of irregular residual astigmatism and other more specialist applications.

Both main IOL ranges have demonstrated proper fixation and centration, and one study confirmed better centration of the Sulcoflex platform in the ciliary sulcus compared to IOLs implanted in the capsular bag. However, there is insufficient published data on the Reverso IOL to reach a conclusion on stability, and one study on the XtraFocus suggested it was less stable in the sulcus.

The Sulcoflex monofocal aspheric supplementary IOL can be used to correct residual refractive errors after implantation of other IOLs in the bag, providing good visual acuity and predictable refraction. The bifocal refractive Sulcoflex Multifocal 653F IOL improves intermediate and near visual acuity, while the Sulcoflex Trifocal IOL provides good levels of functional visual acuity over a range of distances. Photic phenomena are experienced by many patients but in both cases the procedure is easily reversible if the patient cannot adjust. Residual astigmatism can easily be corrected with the supplementary Sulcoflex Toric IOL which has demonstrated good stability, leading to minimal misalignment and loss of cylinder power.

The 1stQ AddOn spherical IOL improves visual acuity and reduces residual SE while the toric model significantly reduces astigmatism. The AddOn Progressive trifocal IOL provides predictable and stable refraction, good visual acuity at all distances and a high rate of spectacle independence.