Refractive Segmental Multifocal IOLs – A New Experience

Refractive Segmental Multifocal Intraocular Lenses (IOL’s) were introduced to Australia about five years ago. They have been fast gaining acceptance from many eye surgeons and cataract patients who are seeking a lifestyle lens that is more suited to an ‘intermediate’ world. Refractive Segmental Multifocal IOL’s have also minimised many of the problems associated with earlier diffractive multifocal IOL designs, such as glare, halos¹ and decreased contrast sensitivity.²

Unlike diffractive multifocal IOL’s, which incorporate concentric annular zones, designs like Oculentis refractive IOL’s (Figure 1) incorporate a distance and near segment which are blended to create an extended depth of focus (EDOF). This provides a smooth transition from distance to near. The rotationally asymmetric design of the Oculentis multifocal utilises the ‘Simultaneous Vision Principle’, hence the near segment can be rotated to any axial position without affecting the EDOF vision (Figure 2).

Figure 2: Simultaneous EDOF vision (MF20)

IOL ‘simultaneous vision’ requires neuro-adaptation

Patients who have had refractive multifocal IOL’s implanted will become increasingly more common for optometrists in coming years. Many of these patients may require glasses, especially for reading small print at near. This makes it important for optometrists to know how to refract
them and provide advice to patients as well as support to their eye surgeon pre and post operatively.

IOL ‘simultaneous vision’ requires neuro-adaptation which can happen quickly or slowly over weeks or months,³ depending on the patient. As is the case with multifocal glasses and contact lenses, patient selection and counselling are the key to success.

Oculentis multifocal IOL’s come in spherical and toric form and are available in three add powers (Table 1). The near range of focus is influenced by the aspheric, EDOF design of the IOL, the patient’s corneal spherical aberration and the position of the IOL in the eye.

Post Op Auto Refraction and Subjective Refraction

Auto Refraction
Optically, Oculentis MF IOLs can be thought of as being like a half distance lens and a half reading lens.

This means that if a post-op cataract patient has a perfect result for distance of plano and a near add of +1.50, the auto-refractor will detect about 50 per cent of light as plano and 50 per cent as +1.50. This will average out at +0.75D which predicts -0.75D of spherical refraction. This is an artefact.

Some auto-refractors may not measure a result. The results may vary with pupil size, lid position and IOL position relative to the pupil.

Subjective Refraction

With an Oculentis MF IOL there will be two possible end points for each patient.

The clinician must take care to ensure that the recorded result is achieved with the patient using the distance foci.

The following steps will assist in ensuring the correct end point is achieved:

1. Start the refraction with a lens equivalent to the near add more than the expected auto-refraction (for example, in the case of an MF15, if the expected auto-refraction is – 0.25, then start with +1.25).
2. Refine sphere and cylinder as you would usually do, keeping in mind the need to ‘push the plus’ and only give extra minus if the patient can read additional lines or letters.
3. If a minus result is achieved for distance, check the reading vision with the distance Rx in place. If the patient genuinely has a myopic result for distance then the patient should be able to use the near add at the expected working distance to read.
4. If the patient accepts a minus Rx for distance, but can no longer read with this in place, it is likely that you have refracted with the patient using the near foci.
5. If the patient has good unaided reading vision and refracts up with minus for distance, but then can’t read without a near add, consider lid position. If the upper lid is obscuring the upper (distance) segment of the IOL it may be forcing the patient to use the near foci.
6. In evaluating cases of refractive surprise, perform a wide dilation to confirm that both haptics are in the capsular bag and that the lens is well centred without tilt.
7. If you are prescribing single vision reading glasses for prolonged tasks or to boost reading vision, then consider adding to the distance foci (see Case Study below).

Case Study

MF20 Distance Rx Plano, patient reads N6, but still struggles with small print at 33cm, especially at night.

Option 1: Prescribe Add +1.00D (patient will use near foci giving total plus of approx. +2.50D).

Option 2: Prescribe Add +2.00D
(When the patient has their reading Rx on they will use the distance foci for near giving total plus of approx. +2.00D and have an extra near of +3.50D if they require).

Emmanuel Calligeros B.Optom. UNSW is a qualified optometrist who owned a practice in the inner city Sydney suburb of Newtown for 34 years. He was clinical supervisor and tutor at the School of Optometry UNSW for 24 years. Mr. Calligeros is engaged as a Clinical Specialist –Ophthalmic Surgical with Device Technologies Australia.

References
1. Patrick Versace, MD. Photic Phenomena of Different Multifocal IOL Designs. Supplement to Cataract & Refractive Surgery Today Europe, Jan. 2015.
2. Detlev R.H. Breyer, MD et al. LENTIS Mplus and LENTIS Mplus Toric. Supplement to Cataract & Refractive Surgery Today Europe, Jan. 2012.
3. Christopher Kent, Senior Editor, Review of Ophthalmology. Multifocal Neuroadaptation: Can Training Help The Brain? 19 March, 2010.