Enhanced Stereopsis of Rotationally Asymmetric Multifocal Intraocular Lens With + 1.5 Diopters Near Addition.

Abstract

To the Editor: Stereopsis is the highest level of binocular vision and contributes to the determination of depth and distance in solid object recognition. Currently, multi-focal intraocular lenses (IOLs) with various added powers are selected based on patient preferences and lifestyles. The European Society of Cataract and Refractive Surgery (ESCRS) Functional Vision Working Group report1 emphasized the importance of the postoperative functionality of near and intermediate vision, which are necessary for everyday activities. Conventional multifocal IOLs with 2 distinct foci provide patients with good far and near vision, but unsatisfactory intermediate vision. The use of low-addition multifocal IOLs (low-add IOLs) can improve intermediate vision.2 Herein, we discussed the stereopsis from far to near in patients implanted with low-add IOLs. Twenty-one patients bilaterally implanted with the low-add IOL (Lentis Comfort LS-313MF15 IOL, Santen Pharmaceutical) (69.7 ± 5.2 years, Low-add group) and 22 with the aspheric monofocal IOL (Tecnis ZCB00 V, Johnson & Johnson Surgical Vision) (69.7 ± 5.2 years, Monofocal group) were examined. All surgeries were performed using a standard technique of sutureless phacoemulsification under topical anesthesia by the same experienced surgeon. The low-add IOL was a foldable plate-haptic, rotationally asymmetric, refractive multifocal IOL, combining an aspheric distance vision zone and a sector-shaped near vision zone with an add power of + 1.5 diopters (D) on the lens plane, that was positioned inferiorly. Inclusion criteria were: 1) having postoperative distance-corrected visual acuity (DCVA) of Snellen 20/25 or better in both eyes, 2) refraction difference of < 2.0 D between both eyes, and 3) without manifest strabismus. DCVA and stereoacuity were measured at far (5 m, 2 m), intermediate (1 m, 70 cm, 50 cm), and near (30 cm) using a Binoptometer 4 P (Oculus Optikgeräte GmbH) at 2 months postoperatively. Significantly better distance-corrected intermediate visual acuity, and distance-corrected near visual acuity were attained in the Low-add group than in the Monofocal group (P < 0.001 for 50 cm and 70 cm; P < 0.01 for 30 cm and 1 m) (Supplemental Digital Content Fig. 1A, http://links.lww.com/APJO/A122) Stereoacuity at 30 cm and 50 cm was significantly better in the Low-add group than in the Monofocal group (Supplemental Digital Content Fig. 1B, http://links.lww.com/APJO/A122). The rates of normal range3 (≤ 100 seconds of arc for 5 m, 2 m, 1 m, 70 cm, 50 cm, and 30 cm) were 85%, 77%, 81%, 58%, 53%, and 24% in the Low-add group, while they were 82%, 64%, 59%, 37%, 18%, and 0% in the Monofocal group. The rates of normal range at 30 cm (P = 0.002) and 50 cm (P = 0.017) in the Low-add group were significantly higher than those in the Monofocal group. Consistent with a previous study,4 a low-add IOL provided good postoperative far and intermediate visual acuity. Unlike the double-peak curve pattern observed with conventional far/near bifocal IOLs, the DCVA showed a gradual decrease from far to near. The Titmus stereoscopic test is the most common test measured at a standardized distance (40 cm) as near ster-eoacuity. The current study measured ster-eoacuity under binocular natural viewing conditions at several distances to assess stereopsis similar to those experienced in everyday life. In the Monofocal group, the DCVA and the rates of the normal range of stereoacuity decreased with a shorter target distance. At a distance of 30 cm, no patient showed a normal range of stereoacuity. The effects of optical blur on stereopsis5 have been reported and are comparable to the results in the Monofocal group. In contrast, a normal range of stereoacuity was attained for 1 m to 5 m in approximately 80% of patients in the Low-add group. The Cat-quest-9SF QoL questionnaire6 for assessing intermediate vision1 should have been utilized; however, its validated Japanese version is not currently available. In summary, the rotationally asymmetric multifocal IOLs with + 1.5 D near addition provided enhanced stereoacuity and vision at near and intermediate levels compared with monofocal IOLs. It may be an option for enhanced functional vision, leading to better overall patient satisfaction.