[Changes of dynamic visual acuity after phacoemulsification combined with intraocular lens implantation].

Objective: To compare the spatial resolutions of dynamic optotypes at different speed levels among age-related cataract patients, older people with clear crystalline lenses and senile individuals implanted with intraocular lenses (IOL).

Methods: The control study recruited 24 patients (48 eyes) with age-related cataract scheduled for phacoemulsification surgery in our hospital between Jul. 2011 and Dec. 2011 in the cataract group. Twenty-three older volunteers (46 eyes) with clear crystalline lenses were enrolled in the normal group. The postoperative group consisted of 23 contemporary cases implanted with spherical monofocal non-yellow-tinted IOL and followed up for 3 months postoperatively, of which 5 cases undertook unilateral surgery for normal visual acuity of the contralateral eye. Monocular and binocular best corrected visual acuity at static condition and binocular spatial resolution of optotypes at speeds of 15, 30, 60 and 90 degrees per second (dps) were measured by a logarithmic visual acuity chart. Statistical analysis was performed with student's t test (with Bonferroni correction).

Results: Binocular spatial resolutions at speeds of 15, 30, 60 and 90 dps were (0.29 ± 0.16), (0.34 ± 0.17), (0.47 ± 0.19) and (0.52 ± 0.17), respectively, in the cataract group, and (0.04 ± 0.06), (0.06 ± 0.06), (0.12 ± 0.09) and (0.15 ± 0.11), respectively, in the normal group. Resolution of dynamic optotypes at the four speed levels were statistically lower in the cataract group than in the normal group (t = -6.952, -7.558, -8.235, -8.737; P < 0.01). Velocity dependent spatial resolution changes manifested statistically higher values in the cataract group than in the normal group, with (0.14 ± 0.13) versus (0.03 ± 0.05) at the interval between static and 15 dps (t0-15 dps = -3.874, P = 0.001) and (0.13 ± 0.09) versus (0.06 ± 0.07) at the interval between 30 dps and 60 dps (t30-60 dps = -3.113, P = 0.003). In the postoperative group, resolutions of dynamic optotypes at speeds of 15, 30, 60 and 90 dps were (0.03 ± 0.05), (0.05 ± 0.07), (0.11 ± 0.10) and (0.16 ± 0.11), respectively. Dynamic visual acuities at all the four speed levels were statistically higher in the postoperative group than in the cataract group (t = -7.336, -7.673, -8.328, -8.583; P < 0.01) and compatible to that in the normal group (t = 0.669, 0.400, 0.372, -0.504; P > 0.05). Visual acuity differences between consecutive speed levels were comparable between the postoperative group and the normal group (t = 0.586, -0.326, 0.133, -1.600; P > 0.05), while at the interval between static and 15 dps and the interval between 30 dps and 60 dps, the postoperative group exhibited lower visual acuity changes than the cataract group, with (0.03 ± 0.04) versus (0.14 ± 0.13) (t0-15 dps = -4.182, P < 0.01) and (0.05 ± 0.06) versus (0.13 ± 0.09) (t30-60 dps = -3.334, P = 0.002), respectively.

Conclusions: As the optotype's moving speed increased, spatial resolutions declined more rapidly in patients with age-related cataract. Phacoemulsification combined with IOL implantation could effectively restore the spatial resolution of dynamic optotypes.