February 2019

REFRACTIVE

Presentation spotlight
Revisiting monovision with IOLs


by Stefanie Petrou Binder, MD, EyeWorld Contributing Writer




Monovision with EDOF IOLs
Source: Filomena Ribeiro, MD

 

Surgeon says less anisometropia is the trend for better outcomes

Modern lifestyles demand the flexibility to perform different activities with a high level of comfort. Speaking at the 2018 World Ophthalmology Congress, Filomena Ribeiro, MD, Lisbon, Portugal, deliberated on the rewards of monovision, particularly micro-monovision, in attaining visual goals.
“Ideal presbyopia correction involves continuous, clear, sharp vision, from near to far, in all lighting conditions, without night time dysphotopsias, loss of contrast, or loss of stereopsis,” Dr. Ribeiro explained. “The reality, however, is that all presbyopia solutions have both advantages and disadvantages, as no technology is right for every patient.”

Monovision: What we know

Dr. Ribeiro echoed findings of a 2011 literature review that reported only a small number of clinical studies covering the topic of pseudophakic monovision, despite its common clinical implementation.1
“Pseudophakic monovision is widely practiced but little studied. Much of what we know comes from contact lens literature,” she said. “Monovision patients see clearly by an interocular suppression blur, however, some patients may not be able to suppress the blurred image. The suppression comes with trade-offs in binocular summation, stereopsis, and contrast sensitivity. Neuroadaptation can take 3 weeks or more.”
The amount of anisometropia can strongly influence visual outcomes and patient satisfaction. Increasing anisometropia can improve near acuity but worsen stereopsis. The optimal amount of anisometropia for successful monovision was approximated at 1.5 D, according to a study undertaken in 35 bilaterally pseudophakic patients who received monofocal implants with 1.0 D, 1.5 D, and 2.0 D anisometropia that demonstrated good binocular vision but substantially impaired stereopsis in eyes with 2.0 D of anisometropia.2
The traditional design for full monovision sets the dominant eye for emmetropia and the non-dominant eye at –2.75 D. Evidence from a study that used this approach demonstrated 20/30 or better UDVA and J1 or better UNVA in 140 study patients, with more than 90% patient satisfaction.3
Monovision these days is set to target increasingly less anisometropia. Full monovision involves a high anisometropia of –2.00 to –2.75 D, while mini-monovision is set for an anisometropia of –1.00 to –1.5 D, and micro-monovision is set for less than or equal to 1.00 D. “Although we have very good results in several published papers with full monovision, the evolution is toward micro-monovision. The 2016 ESCRS survey showed that –0.75 D to –1.25 D is the most common choice. The greater the anisometropia, the greater the difficulty of neuroadaptation,” Dr. Ribeiro said.

Rules of thumb

Monovision is cost effective, provides good monocular quality of vision, has less sensitivity to decentration and to capsular opacification/contraction, and represents a better solution if patients develop macular disease or other conditions that reduce contrast sensitivity. On the other hand, it can be associated with a loss of stereopsis, loss of binocular summation, risk of asthenopia, limited intermediate vision, and patients may need spectacles for night driving and prolonged reading.
According to Dr. Ribeiro, requirements for success include lower anisometropia, perfect distance correction in the dominant eye, lower than 50 arc seconds reduction in stereoacuity, and a distance esophoric shift of below 0.6 prism diopters.
“The problem with monovision is the patient selection. It can lead to a variable success rate of between 60% and 80% and needs to be improved. Mini-monovision has a similar success rate as full monovision,” she noted. “Predictors of success are prior experience with the contact lens trial, orthophoria, and weak to moderate ocular dominance. Ocular dominance is difficult to evaluate. Alternate dominance is better because of better interocular suppression, but it must be a weak dominance. The contact lens trial allows the patient to experiment with monovision in real world situations and can help reveal the preferred eye for each distance.”
Crossed pseudophakic monovision for patients with a mild degree of anisometropic pseudophakia may work as well as conventional pseudophakic monovision, however, crossed monovision has more contraindications and should be avoided if the conventional technique can be performed, according to a retrospective comparative study that identified 30 patients who underwent crossed monovision from 7,311 cases of IOL monovision that were reviewed over 14 years. The study author concluded, however, that traditional monovision was still the most reliable method.4
“The issue is still the choice between conventional versus crossed monovision,” Dr. Ribeiro said. “In crossed monovision, the dominant eye is set for near and the nondominant for distance. Pseudophakic crossed monovision can provide good patient satisfaction and spectacle independence. We have had good results with this. Conventional monovision is more popular today, and it may ‘protect’ distance vision and improve intermediate acuity, reducing the patient’s dependence on spectacles.”
Dr. Ribeiro uses an approach in which she modifies monovision with monocularly induced spherical aberrations, which increases the depth of focus and enhances binocular vision through focus visual performance. In the far eye, she corrects the spherical aberration and in the near eye, she either does not correct it or she induces more. This can be combined with EDOF lenses that are more tolerant to residual error than MIOLs. Defocus curves of EDOF lenses for intermediate vision are very good, she said.
“The strategy for monovision with EDOF IOLs is to target emmetropia in the dominant eye,” she explained. “We see the postoperative evaluation, and if we have a good functional status, we replicate it in the second eye. If it needs more near, we can target the second eye for micro-monovision, or for even more near, we can use a bifocal in the second eye. Mix and match defocus curves in our patients are very good,” she said.
“We are fortunate to have many solutions for the correction of presbyopia. Monovision is a satisfactory solution for select patients who cannot afford or may not be suited for MFIOLs. EDOF IOLs are suitable for micro-monovision and mix and match scenarios. The future may bring new IOL designs to further expand our options,” Dr. Ribeiro said.

References

1. Xiao JH, et al. Pseudophakic monovision is an important surgical approach to being spectacle-free. Indian J Ophthalmol. 2011;59:481–5.
2. Hayashi K, et al. Optimal amount of anisometropia for pseudophakic monovision. J Refract Surg. 2011;27:332–8.
3. Greenbaum S. Monovision pseudophakia. J Cataract Refract Surg. 2002;28:1439–43.
4. Zhang F, et al. Crossed versus conventional pseudophakic monovision: patient satisfaction, visual function, and spectacle independence. J Cataract Refract Surg. 2015;41:1845–54.

Editors’ note: Dr. Ribeiro has no financial interests related to her comments.

Contact information

Ribeiro
: filomenajribeiro@gmail.com

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