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Blended vision an option for improving vision at all distances in pseudophakic patients
A ‘mini-monovision’ approach with bilaterally implanted Softec HD IOLs demonstrated positive results.
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Modern cataract surgery has evolved from just cataract removal and IOL implantation into a refractive procedure. Most visual conditions, including myopia, hyperopia, presbyopia and astigmatism, can now be corrected through cataract surgery.
Multifocal and accommodating lenses have their advantages but also have their own contraindications. These disadvantages include the out-of-pocket cost of the IOL, the postoperative patient complaints of glare, especially for night driving, and decreased contrast sensitivity (multifocal IOLs) or less than desired up-close vision (accommodating IOLs).
The full monovision approach targeting the nondominant eye for –2 D to –2.5 D also has its own advantages and disadvantages. It may offer freedom from spectacles at distance and near, but the intermediate range is less than optimal. Some patients find difficulty tolerating the intended anisometropia. Based on the defocus test performed in our office, we found most patients comfortably accept a difference of 1 D to 1.5 D between their eyes.
Cynthia Matossian
An approach described as “mini-monovision,” or blended vision, using the Softec HD IOL (Lenstec), a bi-equiconvex monofocal IOL, can provide a successful option by improving distance, intermediate and near vision in pseudophakic patients with an intended target of –0.75 D or less between the two eyes. These patients can achieve excellent uncorrected distance vision, very good uncorrected intermediate vision and adequate uncorrected near vision. Each of the patients in my study expressed a desire for greater spectacle independence but either could not afford the advanced technology IOLs or was not a candidate for a multifocal or an accommodating IOL. This approach provided an alternative for this group of patients.
In a retrospective study, we examined the uncorrected visual outcomes at distance, intermediate and near of 46 patients. The patients ranged in age from 59 to 86 years. Each subject underwent cataract surgery with the implantation of the Softec HD IOL in each eye. Limbal relaxing incisions were performed at the time of surgery to correct preoperative cylinder that ranged between 0.51 D to 1.5 D. The dominant eye was targeted for emmetropia, and the nondominant eye was targeted between –0.5 D to –0.75 D.
The patients were tested 1 month postoperatively for uncorrected distance vision at 20 ft, intermediate vision at 32 in and near vision at 16 in using ETDRS cards. Monocular and binocular testing for all three distances was performed and analyzed.
Study results
The postoperative spherical equivalents were compared to preoperative targets (Figure 1).
Source: Matossian C
Monocular results were calculated for distance, intermediate and near (Figure 2). It should be noted that the uncorrected intermediate vision was equal to or even slightly better than uncorrected distance vision because this data reflected the analysis of dominant eyes aimed at emmetropia and nondominant eyes aimed at –0.5 D to –0.75 D. The intermediate vision was measured at 32 in, a convenient working distance for computers and other electronic devices commonly used today.
Source: Matossian C
Because all visual acuities were measured with the Snellen system, they first had to be converted to logMAR in preparation for the mean visual acuity analysis. They were then converted back into Snellen visual acuity to obtain the following mean visual acuities:
- Distance mean visual acuity: 20/20
- Intermediate mean visual acuity: 20/20
- Near mean visual acuity: 20/30 (J3)
Binocular results were impressive and showed the benefit of the blended vision mini-monovision approach (Figure 3).
Source: Matossian C
The previously mentioned mean visual acuities were achieved using the blended vision approach with a bi-equiconvex monofocal IOL.
To ensure that there were no other factors influencing our results, we analyzed pupil size and postoperative astigmatism. No statistically significant correlations were seen between pupil size and the uncorrected visual acuities for near, intermediate and distance vision.
Similarly, no statistically significant differences were seen between the types of astigmatism and the uncorrected visual acuities for near, intermediate and distance vision.
Conclusions
The availability of this bi-equiconvex monofocal IOL in 0.25 D increments, as well as a possible pseudo-accommodative characteristic that requires further research and testing, enabled the achievement of the targeted postoperative results.
The Softec HD provides excellent distance, very good intermediate and adequate near vision outcomes when implanted bilaterally using the blended vision, or mini-monovision, approach with less dependency on spectacles.