SHERI ROWEN, MD, NVISION Eye Centers, Newport Beach, CA

New-onset, surgically induced anisemetropia is an extremely difficult adaptation for a 77-year-old posthyperopic patient. We don’t know whether he had been treated for some level of monovision when he underwent LASIK, but that information would be helpful. Since he wants distance, he most likely did not have monovision, or he did have it but didn’t like it. If he wanted to read, most likely he should have been treated to be ~-1.50 to -1.75 max in his nondominant eye since this power is more accepted by the brain than -2.5 D. If he tolerated a -1.5 D outcome or less, he should be able to tolerate a simple lens exchange to achieve that goal. Apparently, the prior surgeon aimed for a -2.5 D outcome, which in my opinion is far too much anisemetropia for most patients to tolerate.

In this instance, I would do a contact lens trial to see if he would like that lower myopic outcome, and if so, I would choose a lens that would deliver that outcome. I would try multiple powers of contact lenses to see which power suited his needs and that he could tolerate in day and night vision. I would send him out as a -1.5 D myope in that eye for a few days, and if he didn’t like that, I would try some other powers. If he is sure he wants distance, I would back calculate for an in-the-bag placement of a lens for distance based on the Barrett True-K formula, and have a backup sulcus lens.

The formula that I would use would be the Barrett True-K for posthyperopic LASIK treatment. It appears that the original surgeon used a postmyopic LASIK formula, which is why the patient came out so myopic. We can see from the topography that he has central steepening from his prior hyperopic LASIK treatment, which confirms the prior hyperopic treatment. Since we know he came out -0.35 D more myopic with the implanted lens, provided we can put a similar lens in the bag without difficulty, we can back calculate for that and choose a lens with up to a +0.5 D hyperopic outcome since that would be the correct lens choice for emmetropia based on the posthyperopic algorithm.

If the patient did not like monovision whatsoever, then I would restore him to distance with a lens exchange using the Barrett True-K formula aiming for slightly hyperopic to account for the additional -0.35 D outcome over predicted power. The light-adjustable lens (LAL, RxSight) would also be an option if he wanted a precise outcome.

I would not treat his eye with either further LASIK or photorefractive keratectomy (PRK) over the flap. Further, LASIK would induce more aberrations to an already treated eye, and we have veered away from PRK due to inconsistent epithelial healing and remodeling. I would not use a piggyback lens in this case, as minus lens edges could cause iris chafing and uveitis-glaucoma-hyphema syndrome. I would consider it if he had had a plus outcome. I would not consider resigning this patient to glasses or contact lenses either. He is 77 and would most likely not like learning to use contacts, and he definitely won’t like the anisemetropia with glasses.

He is only 4 months out of surgery, but we have to be careful of the terminal end bulbs on some IOL platforms, as they become scarred to the capsule with fibrotic tissue early on. Either the lens can be gently viscodissected thoroughly and the haptic rotated out of the bag, or the haptics can be easily cut and left behind and a sulcus lens placed if the bag integrity is questionable or violated. I would use a Bausch + Lomb LI61AO for this purpose and adjust the power of the lens for the different A-constant, usually by 1.5 D less than in-the-bag placement. 

MATTHEW G. FIELD, MD, PhD, Minnesota Eye Consultants, Woodbury, MN

The answer to this question is complicated and involves multiple considerations. First of all, why was the decision made at the initial cataract evaluation to have “true” monovision? For me to offer a patient monovision (distance in one eye and near in the other), I want a documented history of tolerated monovision usage, with LASIK/PRK, contact lenses, or something else.

Assuming the patient liked monovision previously, then the question is whether a -2.875 standard error difference between eyes is too much for the patient to tolerate. Yes, on the IOL calculations, myopic LASIK was selected instead of hyperopic LASIK, and the patient ended up 0.35 D more myopic than expected, but I would not expect 0.35 D more myopia (with a tolerated history of monovision) to be that unbearable. So at this point, I would first send the patient for a contact lens trial, and I would work to determine exactly what the patient is looking for. Perhaps the patient really does not want both set for distance but actually wants minimonovision, with the left eye set for more intermediate (ie, -1.00 to -1.50) to give more of a range of vision without glasses, which is much better tolerated than monovision by most patients.

Once the patient determines what is truly desired, I would have a conversation with them about all of the options, including associated costs. If cost was not a concern, I would prefer PRK on top of the previous LASIK as my first choice and a lens exchange with placement of an LAL as my second choice. The refractive properties of an LAL can be fine tuned after cataract surgery/lens exchange to achieve the desired refraction of the patient, which is particularly helpful in post-LASIK patients in whom the refractive outcomes are less predictable. There is always a concern regarding whether a lens can be successfully exchanged due to scarring/fibrosis of the lens in the bag, so the sooner after cataract surgery that is attempted, the better. If lens exchange was chosen, I would clearly discuss the risk of unsuccessfully exchanging the lens with the patient before proceeding and would be prepared to place a scleral-fixated lens if necessary.

DR. TRATTLER'S APPROACH

Both Dr. Rowen and Dr. Field provided insightful comments. They both recommended a contact lens trial–and they were correct, as this step confirmed that the patient would be happy if his left eye was set for distance (similar to his right eye). While PRK over LASIK flaps is an option for this level of myopia, we decided to proceed with an IOL exchange.

Planning the IOL power is very straightforward when the preop biometry with IOL calculations are available. The preop IOL calculation listed 18.85 as the correct power to end up emmetropic with the same Alcon monofocal IOL. Since we know the patient ended up 0.35 D more myopic than the recommended IOL power from these calculations, we went with the next lowest available lens power (18.5 D) so that we would end up closer to plano. While the LAL can of course be used (as Dr. Field suggested), we opted to use the same brand of monofocal IOL, as the patient was happy with the quality of vision in the fellow eye, and we can easily calculate the correct IOL power using the preoperative biometry. Notably, we did repeat biometry and topography prior to the exchange to confirm that the corneal shape and biometry data points were stable.

The IOL exchange procedure, which was performed about 6 months after the original procedure, was uneventful since the capsular bag was healthy and no ND:Yag had been performed. Viscoelastic was placed under the capsule, and the haptics with terminal bulbs were effectively released with this maneuver. Once the IOL was rotated out of the capsular bag and positioned in the anterior chamber, the new IOL was inserted and placed in the capsular bag to serve as a protective barrier for the posterior capsule. Then, the original IOL was split into 2 parts with micrograspers and intraocular microscissors, and the 2 pieces were removed gently through a 2.5-mm incision. Intracameral moxifloxacin was placed, and no sutures were required.

Dr. Trattler is the Director of Cornea at the Center for Excellence in Eye Care in Miami and serves on the volunteer faculty for Florida International University Wertheim College of Medicine, as well as the South Florida Larkin Hospital Ophthalmology Residency program.