MFIOLs increase spectacle independence in pseudophakic patients by correcting presbyopia. TIOLs are a subcategory of MFIOL that work by diffracting light into three separate focal points for distance, intermediate and near [1, 2, 4]. Appropriate patient selection, including exclusion of patients with many forms of irreversible ocular disease, is critical to success. TIOL technology has potential drawbacks, including photic phenomena and decreased contrast sensitivity in mesopic conditions [12, 13]. Psychophysical halometry demonstrates that the double halo pattern produced by TIOL’s tends to elicit fewer visual complaints than the single halo pattern produced by commercially-available BIOL’s . However, clinically significant haloes persist in approximately 40% of patients at a period of 3-6 months after TIOL placement [1, 15, 16] and can be bothersome in 5% of patients . Studies also show that it may require 3 months for neuroadaptation to occur after MFIOL placement [6, 17, 18].
Although a wide variety of MFIOLs are implanted in the UAE, a comprehensive review of the CCAD electronic medical record system for MFIOL exchange of any IOL type revealed that the only MFIOL that required exchange during the study period was the AT LISA TIOL. The AT LISA combines a central 4.3 mm diameter trifocal area with a bifocal diffractive surface between 4.3 to 6 mm. The lens is available in both toric (model 939) and non-toric (model 839) versions, and can come preloaded (MP) or non-preloaded (M). The AT LISA TIOL provides good contrast sensitivity and excellent uncorrected distance, intermediate and near visual outcomes in well-selected patient populations resulting in high rates of spectacle independence and patient satisfaction [1, 15, 18].
With regard to overall MFIOL available to our patients regionally, BIOL’s were the first MFIOL’s widely implanted in the UAE, but these patients represent only a small number of patients with MFIOL’s presenting to our practice. In 2012, the AT LISA was the first TIOL available in the UAE. The Panoptix IQ TIOL (Alcon Laboratories, Inc.) became available later in Fall 2014. As these newer IOL’s emerged, the market shifted from BIOL to TIOL technology, and overall MFIOL implantation numbers are currently estimated to be in the thousands yearly. EDOF IOL’s have more recently become available in UAE, but most were implanted after our designated study period. It’s important to note that our clinic cares for a substantial number of (both) expatriates and local patients who have participated in medical tourism abroad, where a larger variety of MFIOL’s may have been implanted.
In this case series, 5 of 6 eyes presented with > 0.5D of residual refractive cylinder, which has been correlated with patient dissatisfaction after MFIOL placement [19, 20]. Despite correcting refractive error with spectacle correction, none of our patients experienced subjective improvement in vision. We believe this is due to the presence of additional ocular comorbidities in our series of patients.
MFIOL implantation is contraindicated in the setting of ocular comorbidities that could further impact visual quality [5, 21, 22]. There is no evidence to suggest that TIOL’s are any more or less forgiving relative to ocular comorbidities than BIOL’s, as studies have shown equivocal outcomes related to contrast sensitivity outcomes between TIOL’s and BIOL’s [3, 13, 23]. Contraindications to BIOL and TIOL placement include, but are not limited to: corneal disease, untreated dry eye syndrome, abnormal/irregular tomography/topography, mydriasis/miosis, zonular instability/loss, macular disease and optic nerve disease . Chronic or recurrent uveitis is an absolute contraindication for MFIOL placement, given this disease’s potential to negatively impact multiple parts of the ocular system. If there are potentially reversible comorbidities, such as untreated dry eye, map dot fingerprint dystrophy, pterygia or Salzmann nodules, we advise treating those conditions to resolution before consideration of MFIOL placement.
Corneal tomography is advised to check for abnormalities such as irregular astigmatism, increased higher order aberrations (HOA) and increased angle kappa. One of the patients in our series had -0.61 μm of horizontal corneal coma and angle kappa of 0.66 mm, as shown in Figure 1. Following primary cataract surgery, this patient suffered from visually significant haloes that weren’t ameliorated by miotic drops or blue light (470 nm) filtering eyeglasses. It has been reported that coma values > ±0.33 μm are problematic for MFIOL’s, as these patients may experience intolerable photic phenomena . Alternatively, others recommend avoiding MFIOL technology when corneal HOA’s exceed average +2.00 SD of total HOA’s, ± 0.30 μm of coma, ± 0.40 μm of trefoil, ± 0.30 μm of quatrefoil, ± 0.20 μm of fifth-order aberrations, or angle kappa is > 0.4 to 0.5 mm, as these abnormalities may decrease visual quality and increase the incidence of haloes and glare [25–27].
Preoperative dilated fundus examination and retina ocular coherence tomography (OCT) are advised to check for macular disease, as it is estimated that more than a quarter of patients undergoing phacoemulsification may have concurrent macular pathology . Diabetes remains a relative contraindication to bifocal or TIOL technology, and there is no definitive guidance in this regard. We advise avoiding TIOL placement in any patient with diabetic retinopathy, diabetic macular edema and/or historical poor blood sugar control. If there is no evidence of diabetic retinopathy and a history of well-controlled blood sugars with adherence to diet and medication therapy, the surgeon and patient may consider TIOL placement. However, the patient should be informed that IOL exchange might be necessary if diabetic macular disease occurs in the future. One eye in this series had focal interruption in the ellipsoid zone in the fovea, as shown in Figure 2. The patient complained of blurred vision at all distances after TIOL placement. In this particular case, the findings were only evident on retinal OCT, which has been shown to be more sensitive than stereoscopic retinal examination. Nearly 7 to 11% of normal-appearing retinas may harbor subtle macular pathologies that can only be reliably detected on OCT [29, 30]. Although a preoperative screening OCT adds additional cost to cataract workup, it has been shown to be cost-effective by facilitating appropriate IOL selection by the patient and surgeon . For cataract surgeons inexperienced with retinal OCT interpretation, this is one future potentially simple and useful application for artificial intelligence in the classification of normal from abnormal scans.
There are several published decision trees for managing patients that are intolerant to MFIOL placement [5–7]. The first step is to assess the subjective experience of the patient and to address his/her individual concerns . Many problems can be effectively managed with a variety of minimally invasive treatment modalities specific to the complaint . Second, treat reversible ocular comorbidities. A recent study by Seiler et al  found that residual refractive astigmatism > 0.5D was the most common cause of patient dissatisfaction following placement of a TIOL. 26% of the eyes required subsequent selective wavefront-guided laser in situ keratomileusis to achieve satisfaction. We advise considering laser refractive correction if the patient improves with a trial of refractive correction but does not want to use spectacles or contact lenses. Dry eye syndrome is also a common confounder and we recommend initiating and escalating treatment per an established dry eye management protocol .
For patients experiencing bothersome photic phenomena, inhibition of mydriasis with topical brimonidine tartrate 0.2% on an as-needed basis can help to ameliorate the symptoms . We have anecdotal experience suggesting that blue light filtering eyeglasses (470nm) reduces photic phenomena in some patients. This is consistent with published findings demonstrating that blue-filtering IOL’s may play a role in glare reduction in pseudophakic patients .
Clinically significant PCO is common after TIOL placement . In a multi-center retrospective analysis looking at rates of Nd:YAG laser capsulotomy, investigators found the capsulotomy rates to be 23% following AT LISA placement . Nd:YAG laser capsulotomy should be reserved until other potential problems have been ruled out and addressed, especially if the extent and density of the capsular opacity is disproportionate to the symptoms.
If there are ocular comorbidities that cannot be ameliorated, IOL exchange can be undertaken even years after initial IOL implantation . For biometry prior to IOL exchange, we recommend using the Barrett Rx Exchange formula in cases where pre-phacoemulsification biometric data is available. This formula is derived from both the Barrett Universal II and Barrett Toric Calculator formulae. It calculates spherical power and, if needed, the optimal cylinder power and alignment of the new IOL . Lacking historical data, one should use a 3rd generation IOL formula that does not estimate effective lens position (ELP) based on anterior chamber depth measurement (ACD). One eye in our study underwent calculation with the Holladay 2 formula on the IOL Master in the pseudophakia setting, but the ACD artificially overestimated ELP and resulted in myopic surprise.
IOL exchange can be challenging. The most common intraoperative complications include capsular rupture, vitreous loss and zonular rupture [10, 34]. In this study, surgical complexity was highest in the 2 eyes from the same patient with bilateral intermediate uveitis and severe capsular fibrosis bilaterally. We recommend a bimanual surgical technique along with meticulous viscodissection and/or haptic amputation in cases of severe capsular contraction or fibrosis. In cases of zonular loss and capsular bag instability/decentration, be prepared to implement capsule support and refixation devices combined with scleral-fixation techniques in order to stabilize and re-center the IOL-capsular bag complex. Scleral-fixated capsular tension segments may be preferable to modified CTR’s, as fibrosed capsular bags may not be amenable to placement of a CTR. The IOL scaffold technique has been shown to be safe and effective and can potentially reduce the risk for vitreous loss and posterior capsule rupture . In cases of an open posterior capsule, this technique also prevents posterior dislocation of the IOL optic during transection . Be prepared for anterior vitrectomy if vitreous presents and have a backup 3-piece IOL in case sulcus IOL placement is necessary. Alternatively, in the event that an IOL cannot be safely inserted into the capsular bag or sulcus, a scleral-fixated, iris-fixated, or anterior chamber IOL can be considered.
There are several limitations to this study. First, the AT LISA TIOL was the only MFIOL exchanged in our study. This study was conducted as a single-institution, retrospective chart review, whereas we know MFIOL’s are implanted and presumably exchanged elsewhere in the region. Thus, we are unable to calculate the comparative regional rate or overall incidence of MFIOL exchange within the scope of this study. Second, the sample size in this study is small. Although the improvement in standard mean differences from preoperative to postoperative UDVA, CDVA, MRSE and residual refractive error are quite large, we would need more eyes to demonstrate statistical significance. Third, neither contrast sensitivity assessment nor quality of vision surveys are routinely measured as a part of the clinical workup of patients in our clinic, so this quantitative data is not included in the analysis.
Although we know TIOL’s provide high levels of spectacle independence and patient satisfaction, our experience suggests that patient selection is critical to success, similar to other MFIOL’s. When patients are intolerant to MFIOL technology, particularly in the setting of irreversible ocular comorbidities, our results demonstrate that IOL exchange is an effective and safe surgical option. IOL exchange to a monofocal IOL resulted in subjective improvement in vision by the last follow up appointment in each of our patients.