3.1. Preoperative Patient Data

The mean age of the 20 women (76.5%) and 8 men (23.5%) was 58.75 ± 5.941 years (range 47 to 73 years). Cataract removal was performed in 4 eyes (7.1%), whilst clear lens extraction was performed in 52 eyes (92.9%). Mean follow-up was 27.59 ± 10.146 months (ranging from 8 to 48 months). The mean IOL power was +24.38 ± 3.651 D (ranging from 13.5.0 to 33 D).

All 28 patients had both eyes operated, with a total of 56 eyes operated. Femtosecond laser-assisted surgery was performed in 28 eyes (50%), whereas conventional phacoemulsification was performed in 28 eyes (50%).

Table 1 shows the patients’ preoperative characteristics by technique group. There was no statistically significant difference between the 2 groups preoperatively. Regarding CDVA, each group had 26 eyes (92.8%) with 20/30 or better (Snellen notation), whereas 2 eyes (7.2%) in each group had CDVA worse than 20/30 (p>0.50). The cases were distributed evenly between the 2 surgeons and between the 2 treatment techniques (p = 0.987) (Table 2).

Table 1.

Patient demographic and clinical characteristics.

Parameter Monocular Mean value ± SD P value FS CP UDVA (logMAR) 0.36 ± 0.302 0.36 ± 0.294 0.986 CDVA (logMAR) 0.03±0.080 0.04±0.077 0.865 Spherical Equivalent (D) 1.35±2.140 1.75±2.333 0.505 Total corneal astigmatism (D) 0.540±0.227 0.654±0.128 0.188 Nuclear sclerosis† 0.18±0.669 0.14±0.525 0.825 Average keratometry (D) 43.98±1.430 44.02±1.595 0.915 Axial length (mm) 21.87±1.600 21.75±1.644 0.776 Anterior chamber depth (mm) 3.17±0.218 3.19±0.255 0.831 White-to-white (mm) 11.77±0.293 11.77±0.289 0.999 Table 2.

Case distribution between the 2 surgeons and between the 2 treatment techniques (p = 0.987).*

Parameter Surgeon 1 Surgeon 2 Total Conventional 15 13 28 Phacoemulsification Surgery Femtosecond 15 13 28 Laser-assisted Surgery Total 30 26 56 3.2. Refraction and Visual Acuity

Femtosecond laser treatment was delivered successfully in all cases in the FS group, with no adverse events registered (including the presence of myosis or significant bubbles); similarly, conventional phacoemulsification was performed without any adverse events.

Mean postop UDVA was 0.01 ± 0.0661 logMAR (range -0.1 to 0.18) for all operated eyes (both techniques), while mean postop CDVA was -0.01 ± 0.0412 logMAR (range -0.1 to 0). The mean duration of surgical procedures was 14.80 ± 2.733 min for the femtosecond laser-assisted surgery (FLALS or FS) and 14.69 ± 2.121 min for Conventional Phacoemulsification (CP) (p>0.05).

As shown in Table 3, mean postop visual acuity data did not differ significantly between techniques (p values >0.05) at 6 months postoperatively. Cumulative snellen visual acuity is shown in Fig. (1), comparing uncorrected and corrected postoperative values for far, intermediate and near for the two techniques. Twenty-six eyes (92.8%) in the FS group and 25 eyes (89.3%) in the CP group had a monocular UDVA of 20/25 or better; all eyes in both groups had a minimum UDVA of 20/32 at 6 months postoperatively. Twenty-seven eyes (96.4%), both in FS and CP groups, had a CDVA of at least 20/20, and all eyes in both groups had a CDVA of 20/25 (Fig. 1A).

CDVA = corrected distance visual acuity (6 m); D = diopters; DCIVA = distance-corrected intermediate visual acuity (at 60 cm); DCNVA = distance-corrected near visual acuity (40 cm); LogMAR = logarithm of the minimum angle of resolution; UDVA = uncorrected distance visual acuity (6 m); UIVA = uncorrected intermediate visual acuity (at 60 cm); UNVA = uncorrected near visual acuity (40 cm)

Regarding postop UIVA, the CP group presented with 20/20 in 85.7% of the eyes against 78.6% in the FS group (p=0.494), with closer results for DCIVA of 20/20 (78.6% vs 75%, respectively for CP and FS) (p=0.955) (Fig. 1B). Concerning UNVA and DCNVA, mean values did not differ significantly (p=0.803 and p=0.968, respectively); for DCNVA, 92.8% in the FS group and 85.7% in the CP group achieved 20/25 or better (Fig. 1C). Considering safety in the context of the best measured visual acuity, histograms for far, intermediate and near are shown in Fig. (2), with similar results for both techniques.

Table 3.

Postoperative visual and refractive outcomes.

Parameter Monocular Mean value±SD P value FS CP UDVA (LogMAR) 0.01±0.068 0.02±0.065 0.337 CDVA (LogMAR) -0.01±0.044 -0.01±0.038 0.522 UIVA (LogMAR) 0.02±0.042 0.01±0.036 0.494 DCIVA (LogMAR) 0.03±0.044 0.02±0.049 0.955 UNVA (LogMAR) 0.04±0.054 0.04±0.059 0.851 DCNVA (LogMAR) 0.05±0.060 0.04±0.070 0.968 Spherical Equivalent (D) 0.009±0.259 -0.054±0.574 0.575

Fig. (1). (A, B and C) Cumulative postoperative monocular visual acuity at last visit (28 eyes in each group) (CDVA = corrected distance visual acuity (6 m); CP = conventional phacoemulsification group; DCIVA = distance-corrected intermediate visual acuity (at 60 cm); DCNVA = distance-corrected near visual acuity (40 cm); FS = femtosecond group; UDVA = uncorrected distance visual acuity (6 m); UIVA = uncorrected intermediate visual acuity (at 60 cm); UNVA = uncorrected near visual acuity (40 cm).

The assessment of efficacy and safety outcomes from an essentially refractive point of view (comparing preop CDVA vs. postop UDVA and CDVA, respectively) is also shown in the histograms in Fig. (3). The efficacy index was high for both techniques, with 1.08 ± 0.149 for the FS group and 1.05 ± 0.244 for the CP group (p=0.893). With regard to the safety index, the FS group of eyes achieved a value of 1.13 ± 0.244, whereas the CP group had a similar value of 1.12 ± 0.236 (p=0.888). Regarding efficacy and safety indexes, there was no clinical difference between the techniques (p>0.5).

Fig. (2). (A, B and C) Difference between postoperative uncorrected and corrected monocular visual acuity at last visit (28 eyes in each group) (CDVA = corrected distance visual acuity (6 m); CP = conventional phacoemulsification group; DCIVA = distance-corrected intermediate visual acuity (60 cm); DCNVA = distance-corrected near visual acuity (40 cm); FS = femtosecond group; UDVA = uncorrected distance visual acuity (6 m); UIVA = uncorrected intermediate visual acuity (at 60 cm); UNVA = uncorrected near visual acuity (40 cm).

The accuracy of both techniques, regarding postoperative spherical equivalent, is shown in Fig. (4A). In the FS group, 96.4% of the eyes fell in ±0.50 D range, compared to 84% of the eyes in the CP group. Four eyes (14.2%) in the CP presented with a negative postoperative spherical equivalent in the range of -0.51 to -1.25D. Postoperative refractive cylinder assessment showed no differences between the two groups (Fig. 4B). Evaluation of the achieved versus attempted spherical equivalent refraction was conducted (Fig. 4C and D), with regression analysis showing the determination coefficients for both groups; the value of R2 was similar for the FS group (R2 = 0.9859) and CP group (R2 = 0.9687), thus not validating lower predictability of the CP procedure as compared to FS technique for this study population.

Stability of refraction was defined as a change of manifest refraction inferior to 0.5D between the 1st month visit and the last visit. Refraction was stable in all FS eyes, whereas a change occurred in 2 of the 28 eyes (7.1%) operated with CP between 1st month and 6th month visits (Fig. 5). There was a myopic change of 0.50D towards “plano” (0.0D) refraction.

Fig. (3). (A) Cumulative monocular postop UDVA vs. preop CDVA at last visit (28 eyes in each group). (B) Difference between postop monocular CDVA and preop CDVA at last visit (28 eyes in each group) (CDVA = corrected distance visual acuity; FS = femtosecond group; CP = conventional phacoemulsification group; UDVA = uncorrected distance visual acuity).

Fig. (4). (A) Accuracy of postoperative refractive spherical equivalent (n=28 eyes in each group). (B) Postoperative Refractive Cylinder (D). (C and D) Achieved versus Attempted Spherical Equivalent Refraction (CP = conventional phacoemulsification group; D = diopters; FS = femtosecond group).

Fig. (5). Stability of spherical equivalent refraction (CP = conventional phacoemulsification group; D = diopters; FS = femtosecond group).

Table 4.

Postoperative visual and refractive outcomes.

Parameter Monocular FS CP p value QoV 1.14±0.650 1.29±0.713 0.103 Satisfaction Index 4.54±0.508 4.34±0.488 0.134

No statistically significant difference between the two techniques was obtained regarding refraction assessment, in spite of a difference between techniques regarding the accuracy of spherical equivalent (SE), with 96.4% of eyes in the FS group presenting postoperative manifest refraction in the ±0.50D range, as compared to 84% of the CP group eyes. At 6 months’ timepoint, we found no significant difference in the postoperative visual acuity or postoperative spherical equivalent between the two groups.

Quality of vision and satisfaction, assessed at 6 months’ visit, were slightly better with FLALS, but still not statistically significant (p=0.103 and p=0.134, respectively) (Table 4).