Visual performance after reduced blinking in eyes with soft contact lenses or after LASIK

Contact Lens Wear and Dry Eye: Beyond the Known

Contact lens wear is one of the relevant risk factors for dry eye, and the coexistence of dry eye poses a serious challenge in patients wearing contact lenses. The Tear Film and Ocular Surface Society Workshop addressed issues around the topic of discomfort in contact lens wear, which is a major cause for discontinuation of contact lens wear, and termed this condition as contact lens discomfort. With the rapid advances in contact lens technology and pharmacological agents and deeper understanding of this field, updating the "new normal" beyond what is known as standard is essential. This review aims to summarize the latest topics in contact lens and dry eye that would be useful for clinicians and contact lens practitioners.

Subjective Comparison of Pre-Lens Tear Film Stability of Daily Disposable Contact Lenses Using Ring Mire Projection

PURPOSE

To subjectively evaluate the in vivo tear film stability of three daily disposable contact lenses (DDCLs) using placido ring reflection at lens wear times of 5 mins and 8 and 12 hrs.

PATIENTS AND METHODS

This prospective, randomized, observer-masked, 3-way crossover study evaluated 28 subjects with good tear film stability. In vivo tear film stability was assessed for three DDCLs (nelfilcon A, etafilcon A, omafilcon A) on three different days over 12 hrs of lens wear. Time to first distortion by non-invasive keratography drying-up time (NIK-DUT_f) was assessed by reviewing the captured videos. Lens wettability was also graded subjectively by three investigators using a scale from 0 (no visible distortions) to 3 (distortions in more than one-third of the ring reflection zone). Medians were analyzed statistically.

RESULTS

Mean NIKDUT_f at 8 hrs was longer for nelfilcon A and shorter for etafilcon A and omafilcon A, but the differences were not significant. NIK-DUT_f did not differ significantly among nelfilcon A, etafilcon A and omafilcon A DDCLs at all visits (p=0.36). Subjective wettability grades after 5 mins, 8 hrs, and 12 hrs differed significantly for etafilcon A (P <0.01) and omafilcon A (p < 0.01), but not for nelfilcon A (p = 0.05), DDCLs.

CONCLUSION

Grading was sufficiently sensitive to differentiate the wettability performances of the three lens materials. Nelfilcon A maintained wettability over the wearing period, whereas etafilcon A material showed faster dewetting at 8 and 12 hrs than at 5 mins after lens insertion.

Functional Visual Acuity

Dry eye (DE) causes irregularity of the ocular surface and reduces the quality of vision. An intact, regular tear film is essential for high-quality retinal images; however, visual tasks requiring sustained gazing can disrupt the tear film, eventually degrading visual function. A functional visual acuity (FVA) measurement system has been uniquely developed in Japan to evaluate visual function related to tear stability in patients with DE. FVA has been shown to correlate with optical quality. The system measures the change in visual acuity (VA) over time automatically in aqueous-deficient DE and short tear breakup tear film DE characterized by decreased tear stability and minimal epithelial damage. It is also useful to detect minimal visual deterioration correlated with minimal ocular surface abnormality and vision-related quality of life otherwise undetectable by conventional VA testing, to assess and quantify vision-related symptomatology, and to determine the efficacy of treatments for DE disease. Recently, its use has been expanded, such as for the analysis of visual function accompanying refractive surgery, contact lens, cataract and cataract-related disease, retinal disease, glaucoma, amblyopia, presbyopia, and vehicle driving. Its use has revealed that FVA reflects not only visual function related to tear dynamics, but also visual function related to quick recognition of the target. This simple, noninvasive, and sensitive FVA measurement system may be expected to be used worldwide.

Comparison of self-reported quality of vision outcomes after myopic LASIK with two femtosecond lasers: a prospective, eye-to-eye study

Purpose

To compare self-reported quality of vision (QoV) outcomes after myopic LASIK (laser-assisted in situ keratomileusis) with two femtosecond lasers.

Design

Prospective, randomized, eye-to-eye study.

Methods

Consecutive myopic patients were treated with wavefront-guided LASIK bilaterally. Eyes were randomized according to ocular dominance. The flap of one eye was made with the IntraLase FS 60 kHz femtosecond laser with a conventional 70° side-cut, and the flap of the fellow eye was made with the IntraLase iFS 150 kHz femtosecond laser with an inverted 130° side-cut. Patients completed the validated, Rasch-tested, linear-scaled 30-item QoV questionnaire preoperatively and at Months 1, 3, 6, and 12.

Results

The study enrolled 120 fellow eyes in 60 patients. None of the measured QoV parameters exhibited statistically significant differences between the groups preoperatively or at any postoperative time point.

Conclusion

Creating LASIK flaps with an inverted side-cut using a 150 kHz femtosecond laser and with a conventional 70° side-cut using a 60 kHz femtosecond laser resulted in no significant differences in self-reported QoV assessed by the QoV questionnaire.

Functional Visual Acuity of Early Presbyopia

Purpose

To evaluate visual function in patients with early presbyopia using the functional visual acuity (FVA) test.

Methods

This study included 27 eyes of 27 healthy older volunteers (mean age, 44.1 ± 2.6 years) and 14 eyes of 14 healthy young volunteers (mean age, 28.4±4.8 years). The distance-corrected visual acuity (DCVA), distance-corrected near VA (DCNVA), subjective amplitude of accommodation (AA), and distance and near pupillary diameters were measured. The distance FVA and distance-corrected near FVA (DCNFVA) were measured using the FVA Measurement System. The standard Schirmer test and standard tear break-up time measurement also were performed.

Results

The logarithm of the minimum angle of resolution (logMAR) DCVA was better than 0 in all subjects. The percentages of subjects with logMAR DCNVA below 0 was significantly lower in the presbyopia group than in the young group. The DCNFVA in the presbyopia group was significantly (P < 0.001) poorer than the DCNVA in that group. Significant linear negative correlations were seen between the DCNVA and AA (r = -0.507, P < 0.001) and the DCNFVA and AA (r = -0.681, P < 0.001) in the older subjects. Stepwise regression analysis showed that only the AA was a significant factor predictive of the DCNFVA in the presbyopia group. Tear function parameters were not adopted in the regression model.

Conclusions

Measurement of the DCNFVA can detect decreased AA in early presbyopia better than measurement of the conventional near VA. The DCNFVA is a good index for early presbyopia.

Impact of long-term soft contact lens wear on epithelial flap production and postoperative recovery in laser-assisted subepithelial keratomileusis

PURPOSE

To investigate the impact and postoperative clinical recovery of long-term soft contact lens wear on the epithelial flap made during laser-assisted subepithelial keratomileusis (LASEK).

METHODS

In a prospective study, 371 patients (589 eyes) who underwent LASEK were divided into four groups (G1, G2, G3, G4) according to their length of soft contact lens wear. After the contact lens (CL) was removed 1 week after surgery, various symptoms - uncorrected visual acuity (UCVA), oedema of the corneal epithelium, spherical equivalent (SE) and haze degree - were recorded on day 1, and at 1 and 3 months postoperatively.

RESULTS

There were no significant differences in corneal flap production among the first three groups that wore CLs, but various symptoms and UCVA were all different from the fourth group that did not wear CLs. There were statistically significant differences in oedema of corneal epithelium among the first three groups, and the degree of oedema was positively correlated with the CL wearing time. There were no significant differences in postoperative SE and haze in all four groups.

CONCLUSIONS

Long-term soft CL wear can affect production of the epithelial flap and postoperative recovery, including various symptoms, oedema of the central corneal epithelium and visual acuity. In contrast, there was no effect of long-term CL wear on postoperative mean refractive spherical equivalent (MRSE) and haze.

The effect of tinted soft contact lens wear on functional visual acuity and higher-order aberrations

PURPOSE

To investigate the differences of functional visual acuity (FVA) and high order aberrations (HOAs) in relation to tinted and clear hydrogel soft contact lens (SCL) wear.

METHODS

A prospective comparative study was performed in 16 eyes of 16 healthy volunteers. Dynamic visual acuity (using a FVA measurement system) and higher-order aberrations (using a wavefront sensor) were compared in subjects wearing two types of soft contact lenses: 1-day Acuvue(®) (Vistakon, Jacksonville, FL) clear and the 1-day Acuvue(®) Define(TM) (Vistakon, Jacksonville, FL) tinted lens. The blink rates were recorded during FVA testing. The correlation between the difference of HOAs and differences in FVA values was analyzed.

RESULTS

The mean LogMAR FVA scores with clear and tinted SCLs were 0.07 ± 0.13 and 0.14 ± 0.17 (P<0.05). The mean blink frequencies with clear and tinted SCL wear were 18.4 ± 8.3 and 25.3 ± 4.7 blinks/min (P<0.05). Both 3rd-order aberrations and total HOAs showed statistically significant differences between the two types of soft contact lenses for 6mm pupil measurements (P<0.05). A significant positive linear correlation was observed between ΔHOAs and ΔLogMAR FVA for 6mm pupil measurements (R=0.53, P=0.04).

CONCLUSIONS

Tinted contact lens wear appears to induce a reduction in optical quality. Functional visual acuity measurement is a useful procedure to study the changes of visual performance and quality in tinted contact lens wear.

Scale and spatial distribution of aberrations associated with tear breakup

PURPOSE

We examined the spatial correlation between tear breakup (TBU) and the associated optical anomalies on multiple spatial scales.

METHODS

Five subjects refrained from blinking while the time course and patterns of TBU were sequentially observed using fluorescein, retroillumination, and Shack-Hartmann (SH) aberrometry. Wavefront error maps were developed using Zernike polynomials, as well as local zonal analysis of measured wavefront slopes. The difference between these maps reveals the presence of very high-order aberrations missed by standard modal fitting methods. Size of SH spots was also quantified to estimate optical perturbations on a microscopic scale. The spatial correlation between TBU and optical aberrations was also computed.

RESULTS

Degradation of the tear film increased wavefront aberrations over all spatial scales measured. Consistent with tear thinning, blink suppression induced an irregular pattern of phase advances in regions of TBU. SH spot size also increased in regions of TBU, which indicates the presence of optical aberrations on a scale smaller than individual lenslets.

CONCLUSIONS

The optical signature of TBU caused by blink suppression is a combination of wavefront aberrations on macroscopic and microscopic scales due to non-uniform tear film thinning and possible exposure of a rough epithelial surface. Localized optical defects correspond temporally and spatially with TBU revealed by fluorescein and retroillumination. In addition to gross wavefront aberrations, scatter develops in areas of TBU that will further contribute to image degradation and visual disturbances after TBU.

Effect of experimentally induced astigmatism on functional, conventional, and low-contrast visual acuity

PURPOSE

To report the changes in functional visual acuity (FVA) in eyes with experimentally induced astigmatism.

METHODS

This study included 26 right eyes from 26 healthy participants (mean age: 27.0±4.4 years). After confirming best correction under cycloplegia, the cylinder power ×90° and ×180° (against-the-rule [ATR] and with-the-rule [WTR] astigmatism, respectively) were added with 0.50-diopter (D) steps, from 0.50 to 2.50 D. Conventional visual acuity (VA), FVA as measured by the FVA Measurement System (NIDEK Co Ltd), and 10% low-contrast visual acuity (LCVA) were measured with 3-mm artificial pupil under each condition.

RESULTS

The mean corrected logMAR VA, FVA, LCVA were -0.18±0.00 (20/13), -0.10±0.08 (20/16), and 0.06±0.06 (20/23), respectively. The VA, FVA, and LCVA had a significant linear negative correlation with the addition of cylinder irrespective of the axes. A significant decrease in FVA was noted on addition of ⩾0.50 D WTR astigmatism and ⩾1.00 D ATR astigmatism. With the addition of 1.00 D of cylindrical lens, 96% of eyes with WTR and ATR astigmatism could maintain 20/20 in VA testing, whereas only 50% and 62% of eyes with WTR and ATR astigmatism, respectively, could maintain 20/20 in FVA testing.

CONCLUSIONS

Astigmatism may be associated with deterioration of visual function even when conventional VA of 20/20 is attained. Functional VA testing seems to be useful in evaluating the masked astigmatic visual impairment that cannot be detected by conventional VA testing.