Considerations On The Calculation Of Multifocal Duet Implantation In A Monovision Scenario For The Correction Of Presbyopia – A Case Example

We report a case in which the patient wanted a reversible multifocal lens implantation due to dysphotopsia considerations, with the additional wish to still be spectacle independent in case of revision. We decided to implant a monovision with monofocal intraocular lenses in the capsular bag and multifocal additive sulcus lenses to convert the monovision into an emmetropic target refraction on both eyes. The aim of this case report is, besides describing the casuistry, a detailed description of our thoughts and procedure for calculating the additive sulcus lens in this case of duet implantation and the resulting still unknown later postoperative anterior chamber depth and postoperative subjective refraction.

Tertiary Care Center (IROC Zürich)

We offer several observations from this case that may be useful to other clinicians. First, we used the additive trifocal IOLs in a patient that demonstrated good tolerance of monovision before cataract surgery. However, the patient specifically desired the option to reverse the procedure if intractable pseudophakic photic symptoms occurred. Second, while our patient tolerated the procedure well in the short term, our surgical strategy also offers late-term advantages should the patient desire reversibility for objective or subjective reasons. For example, the sulcus trifocals can be safely removed in the future with iatrogenic disturbance of the capsule-zonule complex, leaving the patient with a good range of vision through monovision. 

Furthermore, we provided a detailed explanation of how we calculated the powers for all IOLs used, which may further guide clinicians in refining their surgical approaches. The interesting thing is the combination of a monovision calculation for in the bag IOLs, and the calculation for additive sulcus IOLs implanted at the same time and therefore without the abilty to use the measured subjective refraction and anterior chamber depth. Notably, our case is limited to a single patient with short-term results. Future studies are needed to validate our observations.

We report our case of TDI with guidance on IOL power calculations to treat presbyopia with underlying monovision correction. We propose TDI with monovision can be advantageous in treating this patient population by offering the potential of later removing the additive IOL while preserving some form of spectacle independency. Using an axial lens position prediction approach to predict the postoperative anterior chamber depth combined with a formula for additive sulcus IOLs and the target refraction of new generation IOL power calculation formulae can be used to predict the additive sulcus IOL power in case of a duet implantation.