CONTRAST SENSITIVITY DURING PROVOKED VISUAL IMPAIRMENT IN MULTIPLE SCLEROSIS*

Contrast sensitivity and spherical aberration in eyes implanted with AcrySof IQ and AcrySof Natural intraocular lens: the results of a meta-analysis

BACKGROUND

To systematically evaluate the visual performance of aspheric AcrySof IQ and spherical AcrySof Natural intraocular lens (IOL) after cataract surgery.

METHODOLOGY/PRINCIPAL FINDINGS

Potential randomized controlled trials (RCTs) that involved implanting AcrySof IQ and AcrySof Natural were searched from PubMed, Web of science, EMBASE, Chinese Science and Technology Periodicals Databases and Cochrane Central Register of Controlled Trials. The methodological quality of the studies was assessed by the Jadad method. Standardized mean differences (SMDs) with 95% confidence intervals (CIs) of best-corrected visual acuity (BCVA), contrast sensitivity and spherical aberration were pooled using a random-effects model. Seven studies were identified and analyzed to compare AcrySof IQ (236 eyes) with AcrySof Natural (232 eyes) after phacoemulsification. There was no significant difference in postoperative BCVA between AcrySof IQ and AcrySof Natural (p =0.137) after a follow up of 3 months. For contrast sensitivity, these differences reached statistical significance under photopic conditions at two spatial frequencies (3 cycles per degree (cpd), 6 cpd, 12 cpd, and 18 cpd; p =0.022, p =0.017, p = 0.065, and p=0.191, respectively) and under mesopic conditions at three spatial frequencies (3 cpd, 6 cpd, 12 cpd, and 18 cpd; p =0.007, p =0.033, p =0.030, and p =0.080, respectively). Eyes with AcrySof IQ also had statistically significant less spherical aberration than eyes with AcrySof Natural (p<0.001). Sensitivity analysis showed that the results were relatively stable and reliable.

CONCLUSIONS/SIGNIFICANCE

The overall findings indicate that AcrySof IQ with a modified aspheric surface induced significantly less spherical aberration than AcrySof Natural. Contrast sensitivity in eyes with AcrySof IQ is better than that in eyes with AcrySof Natural, especially under mesopic conditions.

Contrast sensitivity and glare disability after implantation of AcrySof IQ Natural aspherical intraocular lens

PURPOSE

To evaluate contrast sensitivity and glare disability after implantation of an AcrySof IQ Natural SN60WF aspherical intraocular lens (IOL) (Alcon Laboratories).

SETTING

Iladevi Cataract & IOL Research Centre, Ahmedabad, India.

METHODS

One hundred twenty consecutive patients who had phacoemulsification in a prospective triple-masked trial were randomized to receive an AcrySof SA60AT IOL (40 eyes), AcrySof Natural SN60AT IOL (40 eyes), or AcrySof IQ SN60WF IOL (40 eyes). At 3 months, contrast sensitivity was measured using the CSV-1000E contrast sensitivity chart test face (Vector Vision) at 3, 6, 12, and 18 cycles per degrees (cpd) under photopic conditions (85 cd/m(2)) and mesopic conditions (2.7 cd/m(2)) with 4.0 mm and 6.0 mm fixed central apertures, with and without glare. The Kruskal-Wallis test was used and a pair-wise comparison performed. The main outcome measure was the difference in contrast sensitivity between IOLs at each spatial frequency.

RESULTS

The best corrected visual acuity was similar between the 3 IOL groups (P = .6). The AcrySof IQ group had significantly higher contrast sensitivity at 18 cpd under photopic conditions (P = .008); at 3, 6, 12, and 18 cpd during mesopic testing with a 4.0 mm aperture without glare (P = .018, P = .011, P = .007, and P = .0001, respectively) and with glare (P = .003, P = .006, P = .005, and P = .004, respectively); and at all spatial frequencies during mesopic testing with a 6.0 mm aperture without glare (P = .018, P = .006, P = .009, and P = .0001, respectively) and with glare (P = .019, P = .002, P = .01, and P = .017, respectively).

CONCLUSION

Eyes with the AcrySof IQ SN60WF IOL had significantly higher contrast sensitivity than eyes with an AcrySof SA60AT or AcrySof Natural SN60AT IOL at all spatial frequencies during mesopic testing (with and without glare) with 4.0 and 6.0 mm artificial pupil.

Role of clearance and treatment zones in contrast sensitivity: significance in refractive surgery

PURPOSE

To evaluate the relationship between contrast sensitivity, surgical treatment zone, and clearance (ablation or clear zone-pupil diameter) in photorefractive keratectomy (PRK) and radial keratotomy (RK).

SETTING

Saint Louis University Eye Institute, St. Louis, Missouri, and Hunkeler Eye Center, Kansas City, Missouri, USA.

METHODS

Thirteen patients had PRK and 20, RK. Contrast sensitivity was measured with the Stereo Optical F.A.C.T. (F.A.C.T.) and VectorVision CSV-1000 (VV) charts. Pupils were measured with the Rosenbaum card.

RESULTS

In the PRK group, VV contrast sensitivity at 6 and 12 cycles per degree (cpd) correlated with the ablation zone (r2 = 0.18 and 0.22, respectively), while visual acuity and F.A.C.T. contrast sensitivity did not correlate. In the RK group, both VV and F.A.C.T. contrast sensitivity at 6 cpd correlated with clearance (r2 = 0.29 and 0.12, respectively). Pupils were larger with the VV test than with the F.A.C.T. chart because ambient chart luminance was less in the former.

CONCLUSION

Contrast sensitivity is likely a more sensitive indicator of visual function than acuity in refractive surgery. The VV system unmasks aberrations from the transition zone of ablated and unablated cornea in PRK. Larger samples are needed to determine the critical ablation clearance of the pupil to avoid loss of visual function.

Abnormal visual adaptation to flicker in multiple sclerosis

A visual psychophysical adaptation procedure was used on patients with Multiple Sclerosis (MS) in an attempt to induce a temporary and local exacerbation of subclinical visual impairment. Using a flicker detection task, sensitivity before and after adaptation to a flickering stimulus was measured in 9 MS patients and 9 control subjects. Although only 22% of patient eyes had abnormal flicker sensitivity prior to adaptation, visual deficit was observed in 83% of eyes studied after adaptation. Of the 7 MS eyes studied for which no other sign or symptom of visual involvement was present, 5 were found to have visual deficits after flicker adaptation. In addition, 10 of the 11 eyes affected by MS showed an abnormal response to flicker adaptation. Recovery from the effects of adaptation was complete in all patients within 2 minutes. The results suggest that partial demyelination of visual pathway neurons may exist in patients without signs or symptoms of visual involvement. The prolonged stimulation provided during adaptation may produce a temporary fatiguing or conduction blockade of such neurons which may lead to reductions in sensory sensitivity.

Contrast sensitivity, acuity, and the perception of 'real-world' targets

A major assumption underlying the use of contrast sensitivity testing is that it predicts whether a patient has difficulty seeing objects encountered in everyday life. However, there has been no large-scale attempt to examine whether this putative relationship actually exists. We have examined this assumption using a clinic based sample of adults aged 20-77 years. Contrast thresholds were measured for both: (1) gratings of 0.5-22.8 cycles/degree; and (2) real-world targets (faces, road signs, objects). Multiple regression techniques indicated that the best predictors of thresholds for real-world targets were age and middle to low spatial frequencies. Models incorporating these variables accounted for 25-40% of the variance. Although acuity significantly correlated with thresholds for real-world targets, the inclusion of acuity as a predictor variable did not improve the model. These data provide direct evidence that spatial contrast sensitivity can effectively predict how well patients see targets typical of everyday life.