In highly hyperopic eyes and nanophthalmic eyes the required IOL power can be very high, sometimes in excess of +40 diopters. For these patients, we can special order IOLs up to +40 D in the USA and even higher in other countries. We all agree that if the patient needs a +44 D IOL power for a plano outcome, the best option is to implant a special order +44 D IOL. But in the USA, when that is not an option, what are the options?
The three main options in the USA are:
- Primary Piggyback IOL implantation at the time of the cataract surgery
- implant the maximum +40 D IOL into the bag and then come back later for a secondary piggyback IOL to be placed in the sulcus
- implant the maximum +40 D IOL into the bag and then have the patient return to spectacles or contact lenses for the remainder of the refractive power
Option 1: Primary Piggyback IOL
In the video below, we have guest surgeon Dr. Michael Patterson showing option 1: he implants a three-piece acrylic IOL (Alcon MA50BM with 6.5mm optic) into the capsular bag, then he places a three-piece silicone IOL (Bausch & Lomb Li61 with 6.0mm optic) with the haptics in the sulcus and the optic captured behind the capsulorhexis. Dr. Patterson used the Holladay 2 software to calculate the split of the total dioptric power between the two IOLs (totaling +44 D) and he achieved an accurate post-op outcome.
When we remove the 4 mm thick crystalline lens, there is certainly room in the capsular bag for two IOLs since they are much thinner. What we want to avoid, however, is inter-lenticular proliferation of cells leading to opacification. This inter-lenticular opacification is not easily treated with a YAG laser and a intra-ocular procedure to remove these cells may be needed. To minimize this risk, surgeons often will put in IOLs of different materials (one acrylic, one silicone) and then achieve a degree of optic separation by implanting the piggyback lens partially or fully in the sulcus.
Option 2: One IOL in the bag now then future piggyback IOL in the sulcus
In terms of a refractive outcome, this option is likely the most accurate. We can implant the maximum power IOL available in the capsular bag at the time of cataract surgery, in this case +40.0 D and then let the eye heal. After achieving refractive stability about one month later, the power of the piggyback IOL is calculated. This is based on the actual refraction of the eye and it is much more accurate than standard IOL calculations which are based on keratometry and axial length.
I learned a very good approximation of piggyback IOL power from Dr. Sam Masket which is based on the refraction:
- for hyperopic refractions multiply the Rx by 1.5 to get the piggyback IOL power
- for myopic refractions multiply the Rx by 1.2 to get the piggyback IOL power
More exact calculations can be done, however at the low levels of correction where we use piggyback IOLs (typically less than 10 D), it does not make a difference.
In the case presented below, the patient received a +40 D single-piece acrylic IOL in the capsular bag at the time of cataract surgery. Then after a month of healing, she ended up with a refraction of +5.50 -0.25 x 90, which is a spherical equivalent of +5.37, which is multiplied by 1.5 to give a planned piggyback IOL power of +8.0 D. A second surgery was done to place the +8.0 D piggyback IOL. The surgeon selected a three-piece acrylic IOL which was placed in the sulcus. The patient achieved a plano outcome and excellent vision, but soon developed problems. The sharp edge of the acrylic piggyback IOL scrape the back surface of the iris causing 360 degrees of posterior iris pigment loss which was seen on transillumination. This led to UGH syndrome: Uveitis, Glaucoma, Hyphema. The piggyback IOL was explanted surgically and the patient went back to wearing glasses and contact lenses for the +5.37 diopters of residual prescription.
Option 3: Maximum IOL power with cataract surgery then spectacles/contact lenses
This is my favorite option because it is the safest with the fewest potential side effects. However, it does not fully correct the refraction to a plano outcome. As ophthalmologists we have a perfectionist mindset of trying to get every eye, no matter how extreme, to a post-op target of plano. In the case shown below, this patient has a truly nanophthalmic eye with only an 8 mm corneal diameter (horizontal white-to-white) and an 18 mm axial length. There was even a degree of pre-existing bilateral ametropic amblyopia and history of prior accommodative esotropia. The patient was extremely hyperopic and wore +10.0 distance glasses (or +11.5 contact lenses) and the ideal IOL power was calculated to be +44.0 D, which we do not have as an FDA-approved option in the US.
When I did her cataract surgery, I implanted the maximum lens power available, the Alcon Acrysof SA60AT +40.0 into the capsular bag. After healing she ended up with a refraction of +2.75 for best distance vision. This means that the ideal IOL power for her would have been a total of +40.0 + (1.5 * 2.75) = +44 D which is what we calculated as the ideal IOL power. Upon viewing with the slit lamp, I felt that there was not enough space to place the piggy back IOL of +4 D into the sulcus.
While I felt some disappointment in not being able to deliver that perfect plano outcome to her, the patient was absolutely thrilled since she went from using +10.0 distance glasses to +2.75 and the cataract and astigmatism were addressed too!
Ultimately, there is no perfect answer — it is up to the surgeon’s judgment and the patient’s wishes.
click below to see the video of Dr Michael Patterson’s primary piggyback IOL case:
p.s. This is our 100th post on CataractCoach.com — thank you for the support and readership!
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