Eyeworld

EW REFRACTIVE 34 February 2019 by Stefanie Petrou Binder, MD, EyeWorld Contributing Writer Surgeon says less anisometropia is the trend for better outcomes M odern lifestyles de- mand the flexibility to perform different activ- ities 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 visu- al 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 stud- ies covering the topic of pseudopha- kic 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 im- age. 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 out- comes and patient satisfaction. In- creasing anisometropia can improve near acuity but worsen stereopsis. The optimal amount of anisometro- pia 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-domi- nant 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% pa- tient satisfaction. 3 Monovision these days is set to target increasingly less anisometro- pia. Full monovision involves a high anisometropia of –2.00 to –2.75 D, Revisiting monovision with IOLs 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. "Al- though 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 neuroadap- tation," Dr. Ribeiro said. Rules of thumb Monovision is cost effective, pro- vides good monocular quality of vi- sion, has less sensitivity to decentra- tion and to capsular opacification/ contraction, and represents a better solution if patients develop macu- lar disease or other conditions that reduce contrast sensitivity. On the other hand, it can be associated with a loss of stereopsis, loss of binocu- lar summation, risk of asthenopia, limited intermediate vision, and pa- tients may need spectacles for night driving and prolonged reading. According to Dr. Ribeiro, re- quirements for success include lower anisometropia, perfect distance cor- rection in the dominant eye, lower than 50 arc seconds reduction in ste- reoacuity, and a distance esophoric shift of below 0.6 prism diopters. "The problem with monovi- sion 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 mono- vision," she noted. "Predictors of success are prior experience with the contact lens trial, orthophoria, and weak to moderate ocular domi- nance. 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 al- lows the patient to experiment with monovision in real world situations and can help reveal the preferred eye for each distance." Crossed pseudophakic monovi- sion for patients with a mild degree of anisometropic pseudophakia may work as well as conventional pseudophakic monovision, how- ever, crossed monovision has more contraindications and should be avoided if the conventional tech- nique can be performed, according to a retrospective comparative study that identified 30 patients who un- derwent 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 be- tween conventional versus crossed monovision," Dr. Ribeiro said. "In crossed monovision, the dominant Replicate in second eye Postop evaluation Good functional status Needs more near Dominant eye Target emmetropia Target micro-monovision Postop evaluation Good functional status Needs more near Dominant eye Target emmetropia Monovision with EDOF IOLs Source: Filomena Ribeiro, MD Presentation spotlight

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