Stereoacuity and Multifocal Intraocular Lenses – A Systematic Review

Author: Bohac M, Jagic M, Biscevic A, Lukacevic S, Mravicic I, Suic SP, Dekaris I.

Geographical coverage: Not reported

Sector: Cataract surgery

Sub-sector: Intraocular lenses

Equity focus: Not reported

Study population: Patients with cataract

Review type: Effectiveness review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background

Stereopsis, the perception of depth through binocular disparity, is a sophisticated binocular function fundamental to human vision and essential for tasks requiring precise hand-eye coordination, such as using tools or working on a computer. Accurate measurement of stereoacuity is important in both clinical and research settings, yet traditional tests may lack the sensitivity to detect subtle changes and can be influenced by factors such as contrast, target design, and patient-specific variables. Although widely used, some tests may yield inconsistent results due to differing methodologies. While multiple tests are available, variability in their accuracy and sensitivity remains a challenge. Therefore, a deeper understanding of the neural and developmental aspects of stereopsis is vital to refine assessment tools and improve diagnostic accuracy.

Objective

To review the results of testing binocular vision in patients with multifocal intraocular lenses implanted in cataract surgery.

Main findings

The review found that only a limited number of studies directly assessed stereoacuity in patients with multifocal intraocular lenses (MIOLs), despite widespread interest in how these lenses affect visual quality. Several studies reported that patients with monofocal intraocular lenses, when tested with near correction, had statistically better stereoacuity than those with multifocal lenses. Among the multifocal types, refractive MIOLs generally performed better than diffractive designs, particularly when measured using the TNO test, which is more sensitive and lacks monocular cues.

Results varied depending on the stereoacuity test used. The Titmus test consistently yielded better stereoacuity scores across all lens types compared to the TNO test, which often showed poorer outcomes, especially in patients with diffractive MIOLs. This discrepancy highlights the influence of test design on outcome interpretation. Despite these differences, most studies agreed that stereoacuity remained within normal ranges following bilateral MIOL implantation.

The review also noted that unilateral MIOL implantation tended to compromise stereoacuity, suggesting that bilateral implantation is preferable for maintaining binocular depth perception. Additionally, “mix and match” approaches, implanting different types of MIOLs in each eye, showed some promise in improving near stereoacuity and reading performance, though outcomes were variable.

Finally, the authors explored physiological explanations for stereoacuity preservation, such as optical properties of MIOLs and neural adaptation. Overall, while MIOLs may reduce stereoacuity compared to monofocal lenses, especially when tested with more dissociative methods, they do not significantly impair binocular function when both eyes are implanted.

Methodology

The searches were conducted in PubMed, Scopus, Web of Science, and Google Scholar to identify relevant publications. No further details on inclusion/exclusion criteria, screening, data extraction, or quality assessment procedures were explicitly described in the methods section. The findings were synthesised narratively.

Applicability/external validity

The review did not explicitly discuss the applicability or external validity of its findings. However, it discussed variability in stereoacuity tests used, multifocal IOL designs, patient selection, and postoperative conditions, which may affect the generalisability of the findings of this review.

Geographic focus

The review did not report inclusion or exclusion criteria or search strategy, nor did it report the geographical distribution of the included studies.

Summary of quality assessment

Overall, there is low confidence in the review’s conclusion. Although the authors refer to the article as a systematic review, it does not adhere to the methodological standards required for a systematic literature review. Apart from listing the databases searched, no details are provided regarding the search strategy, inclusion or exclusion criteria, or counts of included and excluded studies. The review also lacks transparency about the number of reviewers involved in screening or data extraction and does not report any assessment of risk of bias. As such, it does not meet the accepted criteria to be considered a true systematic review.