Pharmacological management of night vision disturbances after refractive surgery

Repeatability of i.Profiler for measuring wavefront aberrations in healthy eyes

PURPOSE

To evaluate the repeatability of wavefront aberration measurements and the correlation between corneal aberration and pupil size in normal eyes using a wavefront-based autorefractor (i.Profiler^Plus; Carl Zeiss Vision, Germany).

METHODS

A prospective cross-sectional study. Wavefront aberrations, including spherical aberration (SA) (Z₄⁰), coma (Z₃^-1, Z₃¹), trefoil (Z₃^-3, Z₃³) and total higher-order aberrations (tHOA), were measured at different pupil diameters. The repeatability was evaluated using one-way ANOVA method, and statistical indicators including within-subject standard deviation (S_w), test-retest repeatability (TRT), and intra-class correlation coefficient (ICC). The correlations between corneal aberrations and pupil sizes were evaluated by Pearson correlation analysis.

RESULTS

A total of 96 healthy young volunteers were enrolled. Corneal and ocular higher-order aberrations (HOA) measured by i.Profiler showed S_w < 0.01 μm, TRT < 0.10 μm, ICC > 0.90. There was a linear positive correlation between the corneal HOA and pupil size. The correlation coefficient between SA and tHOA was the largest (r = 0.996, P < 0.001).

CONCLUSIONS

The measurements of wavefront aberrations by i.Profiler are highly repeatable. Corneal HOA was significantly dependent on pupil size. SA was the most influential aberration for visual quality in this study.

Effect of over-the-counter brimonidine tartrate 0.025% ophthalmic solution on pupil size in healthy adults

Purpose

To evaluate the effect of brimonidine tartrate 0.025% ophthalmic solution on pupil size under scotopic conditions in healthy adults

Methods

Pupil size was measured in 56 eyes of 28 volunteer participants using a pupillometer under scotopic conditions. Age, gender, and iris color were recorded. Subjects using any ophthalmic medications other than artificial tears were excluded. The pupil size was subsequently measured again under scotopic conditions 60 min after instillation of brimonidine tartrate 0.025% ophthalmic solution.

Results

Statistically significant miosis was seen after instillation of brimonidine tartrate 0.025% (p = 0.04). Average pupil size prior to brimonidine 0.025% instillation was 7.28 ± 1.05 mm, and average pupil size after instillation of brimonidine 0.025% was 6.36 ± 1.68 mm, a reduction of − 23.7% in pupil area. Subjects with light irides demonstrated a greater miotic effect than subjects with dark irides (1.55 mm vs. 0.67 mm, p < 0.0001), with a pupil area reduction of − 37.6% and − 17.4%, respectively. The amount of miosis was independent of initial pupil size.

Conclusions

Brimonidine tartrate 0.025% causes significant miosis in scotopic settings, although the effect is not as great in darker colored eyes. Further studies are needed to determine the latency and duration of the effect and whether the amount of miosis is clinically significant.

Evaluation of disk halo size after small incision lenticule extraction (SMILE)

PURPOSE

To investigate changes in objective disk halo size produced by a glare source after small incision lenticule extraction (SMILE) for myopia correction.

METHODS

This prospective clinical study included 45 right eyes of 45 patients with a mean age of 25.40 ± 5.06 years and mean spherical equivalent (SE) of - 6.08 ± 1.90 diopters. Disk halo size was measured with a vision monitor before surgery and at postoperative 1 week and 3 months. Other information was collected, including age, SE, lenticule thickness, lenticule diameter, dark pupil, and pupillary response to light parameters (initial diameter; amplitude, latency, duration, and velocity of contraction; latency, duration, and velocity of dilation; and maximum, minimum, and average pupil size).

RESULTS

Compared to preoperative values, disk halo size increased significantly at postoperative 1 week (P = 0.026) and returned to baseline at postoperative 3 months (P = 0.349). Preoperative disk halo size significantly correlated with SE (r = - 0.346, P = 0.020), minimum pupil size (r = 0.365, P = 0.014), and average pupil size (r = 0.310, P = 0.038). Disk halo size at postoperative 1 week was significantly correlated with age (r = 0.324, P = 0.030) and minimum pupil size (r = 0.297, P = 0.047). Disk halo size at postoperative 3 months was significantly correlated with lenticule diameter (r = - 0.362, P = 0.015), initial diameter (r = 0.311, P = 0.037), maximum pupil size (r = 0.312, P = 0.037), minimum pupil size (r = 0.440, P = 0.002), and average pupil size (r = 0.373, P = 0.012).

CONCLUSIONS

After SMILE, disk halo size demonstrated a temporary increase and then returned to baseline.

Reducing starbursts in highly aberrated eyes with pupil miosis

PURPOSE

To test the hypothesis that marginal ray deviations determine perceived starburst sizes, and to explore different strategies for decreasing starburst size in highly aberrated eyes.

METHODS

Perceived size of starburst images and visual acuities were measured psychophysically for eyes with varying levels of spherical aberration, pupil sizes, and defocus. Computationally, we use a polychromatic eye model including the typical levels of higher order aberrations (HOAs) for keratoconic and post-LASIK eyes to quantify the image quality (the visually weighted Strehl ratio derived from the optical transfer function, VSOTF) with different pupil sizes at both photopic and mesopic light levels.

RESULTS

For distance corrected post-LASIK and keratoconic eyes with a night-time pupil (e.g., 7 mm), the starburst diameter is about 1.5 degrees (1 degree for normal presbyopic eyes), which can be reduced to ≤0.25 degrees with pupil sizes ≤3 mm. Starburst size is predicted from the magnitude of the longitudinal spherical aberration. Refracting the eye to focus the pupil margin also removed starbursts, but, unlike small pupils, significantly degraded visual acuity. Reducing pupil diameter to 3 mm improved image quality for these highly aberrated eyes by about 2.7 ×  to 1.7 ×  relative to the natural pupils when light levels were varied from 0.1 to 1000 cd m^-2 , respectively.

CONCLUSION

Subjects with highly aberrated eyes observed larger starbursts around bright lights at night predictable by the deviated marginal rays. These were effectively attenuated by reducing pupil diameters to ≤3 mm, which did not cause a drop in visual acuity or modelled image quality even at mesopic light levels.

Q-optimized Algorithms: Theoretical Analysis of Factors Influencing Visual Quality After Myopic Corneal Refractive Surgery

PURPOSE

To model the effect of pupil size, optical zone, and initial myopic level on the retinal image quality after Q-optimized myopic corneal refractive surgery.

METHODS

Different Q-optimized and paraxial Munnerlyn algorithms were tested using a schematic myopic eye model to analyze the optical quality of the final retinal image for initial myopic errors from -1.00 to -7.00 diopters (D). Different optical zones (5.5, 6, and 6.5 mm in diameter) and two pupil diameters (5 and 7 mm, mesopic-scotopic conditions) were included in the comparison. Modulation transfer function (MTF) and area under the MTF from 0 to 60 cycles per degree (MTFa) were calculated by ray tracing to evaluate this retinal image quality.

RESULTS

The Q-optimized algorithm with Q = -0.45 provided the highest MTF and MTFa results for myopic corrections less than -5.00 D. For refractive errors greater than -5.00 D, Q = -0.26 provided the highest MTF and MTFa results.

CONCLUSIONS

Q-optimized algorithms improve the visual outcomes with respect to the paraxial Munnerlyn algorithm for myopic corneal surgery. The results show that the Q value that optimizes the results of the Q-optimized algorithm depends on the degree of myopia to correct and the size of the pupil. [J Refract Surg. 2016;32(9):612-617.].

Small-Aperture Intraocular Lens Implantation in a Patient With an Irregular Cornea

PURPOSE

To report a small-aperture intraocular lens (IOL) implantation after corneal trauma.

METHODS

Case report.

RESULTS

A 17-year-old boy with corneal scars, iris defect, and aphakia after perforating trauma in the right eye was scheduled for small-aperture IOL (IC-8; AcuFocus, Irvine, CA) implantation under general anesthesia. No intraoperative complications were observed. Six months after surgery, the uncorrected distance and near visual acuity increased significantly. Furthermore, reduced photopic phenomena were reported.

CONCLUSIONS

The small-aperture IOL is a new and promising option to treat patients suffering from the effects of corneal irregularities. [J Refract Surg. 2016;32(10):706-708.].

Clinical applications of wavefront refraction

Purpose

To determine normative reference ranges for higher-order wavefront error (HO-WFE), compare these values with those in common ocular pathologies, and evaluate treatments.

Methods

A review of 17 major studies on HO-WFE was made, involving data for a total of 31,605 subjects. The upper limit of the 95% confidence interval (CI) for HO-WFE was calculated from the most comprehensive of these studies using normal healthy patients aged 20 to 80 years. There were no studies identified using the natural pupil size for subjects, and for this reason, the HO-WFE was tabulated for pupil diameters of 3 to 7 mm. Effects of keratoconus, pterygium, cataract, and dry eye on HO-WFE were reviewed and treatment efficacy was considered.

Results

The calculated upper limit of the 95% CI for HO-WFE in a healthy normal 35-year-old patient with a mesopic pupil diameter of 6 mm would be 0.471 μm (471 nm) root-mean-square or less. Although the normal HO-WFE increases with age for a given pupil size, it is not yet completely clear how the concurrent influence of age-related pupillary miosis affects these findings. Abnormal ocular conditions such as keratoconus can induce a large HO-WFE, often in excess of 3.0 μm, particularly attributed to coma. For pterygium or cortical cataract, a combination of coma and trefoil was more commonly induced. Nuclear cataract can induce a negative spherical HO-WFE, usually in excess of 1.0 μm.

Conclusions

The upper limit of the 95% CI for HO-WFE root-mean-square is about 0.5 μm with normal physiological pupil sizes. With ocular pathologies, HO-WFE can be in excess of 1.0 μm, although many devices and therapeutic and surgical treatments are reported to be highly effective at minimizing HO-WFE. More accurate normative reference ranges for HO-WFE will require future studies using the subjects’ natural pupil size.

Corneal spherical aberration in Saudi population

PURPOSE

To find out the mean corneal spherical aberration and its changes with age in Saudi population.

SETTING

AlHokama Eye Specialist Center, Riyadh, Saudi Arabia.

METHODS

Three hundred (300) eyes of 185 Saudi subjects (97 men and 88 women), whose age ranged from 15 to 85 years old, with matched refractive errors, were divided into three groups according to their age, 100 for each. All the subjects were included in measuring the spherical aberration (SA) using pentacam HR (OCULUS, Germany) at the 6-mm optical zone.

RESULTS

The mean corneal spherical aberration (CSA) of the fourth order (Z4 (0)) of the whole groups was 0.252 ± 0.1154 μm. Patients from 15 to 35 years old have root mean square (RMS) of CSA of 0.2068 ± 0.07151 μm, 0.2370 ± 0.08023 μm was the RMS of CSA of the patients from 35 to 50 years old, while those from 50 to 85 years old have a CSA-RMS of 0.31511 ± 0.1503 μm (P < 0.0001). A positive correlation was found between the spherical aberration (Z4 (0)) and the progress of age (r = 0.3429, P < 0.0001). The high order aberration (HOA) presented 28.1% of the total corneal aberrations. While the fourth order corneal spherical aberration constituted 57% of the HOA and 16% of the total aberration. The pupil diameter shows a negative correlation with the increase in age (P = 0.0012).

CONCLUSION

Our results showed a CSA (Z4 (0)) that is varied among the population, comparable to other studies, and significantly correlates to the progress of age.

Pupil size and LASIK: a review

PURPOSE

To provide a literature review on the evidence both for and against pupil size as an independent predictor of adverse visual outcomes after LASIK.

METHODS

Peer-reviewed publications on the effect of pupil size on LASIK outcomes since 2002 are reviewed. Particular attention was paid to the following attributes of each publication: type of study, number of patients or eyes, mean age, mean level of myopia, mean pupil size, testing conditions, ablation zone diameter, presence or absence of blend zones, and mean follow-up period.

RESULTS

Among the 19 studies examined, none correlates a persistent relationship between pupil size and night vision complaints (NVCs) beyond 3 months when LASIK was performed with a 6.0-mm optical zone or larger ablation. The studies that did explicitly determine a correlation either included some or all patients with ablation zones smaller than 6.0 mm or did not specify ablation diameter at all. Among the studies that had drawn more mixed conclusions, the studies either covered short follow-up intervals (1 to 3 months) or showed a progressive improvement in NVCs over time in a relatively small patient cohort.

CONCLUSIONS

As keratorefractive technology continues to evolve, the role of pupil size warrants further investigation; however, based on the literature reviewed herein, modern LASIK has negated the role of the low light pupil in predicting adverse visual outcomes after LASIK outside of the early postoperative period.

Theoretical analysis of the effect of pupil size, initial myopic level, and optical zone on quality of vision after corneal refractive surgery

PURPOSE

To analyze the theoretical effect that pupil size, optical zone, and initial myopic level have on the final retinal image after corneal refractive surgery.

METHODS

A schematic myopic eye model corrected by the Munnerlyn formula was used to analyze the optical quality of the final retinal image. Root-mean-square radius spot and modulation transfer function were cal- culated by ray tracing to evaluate retinal image quality.

RESULTS

Pupil size had a negative effect on the retinal image only when it was greater than the diameter of the optical zone. In addition, the greater the initial myopic level, the more the pupil size affected image quality. Thus, a clear dependence exists between the initial myopic level and effect that the pupil size can have on the retinal image after laser refractive surgery.

CONCLUSIONS

Pupil size may be a risk factor for night vision disturbances, but only when it is larger than the theoretical optical zones utilized in this study. Its effect depends not only on the optical zone size, but also on the initial "myopic level. Therefore, this relationship should be taken into account during patient selection for refractive surgery

Efficacy, predictability, and safety of wavefront-guided refractive laser treatment: metaanalysis

PURPOSE

To compare the efficacy, predictability, safety, and induced higher-order aberrations (HOAs) between wavefront-guided and non-wavefront-guided ablations.

SETTING

Division of Ophthalmology and Visual Sciences, University of Nottingham, Nottingham, United Kingdom.

DESIGN

Metaanalysis.

METHODS

The Cochrane Central Register of Controlled Trials, PubMED, and EMBASE were searched for randomized controlled trails. Trials meeting the selection criteria were quality appraised and data extracted by 2 independent authors. Measures of association were pooled quantitatively using metaanalytical methods. Comparison between wavefront-guided and non-wavefront-guided ablations was measured as pooled odds ratios (ORs) or weighted mean differences. The pooled ORs and 95% confidence intervals (CIs) were computed for efficacy, safety, and predictability. The weighted mean difference and 95% CIs were used to compare induced HOAs.

RESULTS

Eight trials involving 955 eyes were included. After wavefront-guided LASIK, the pooled OR of achieving uncorrected distance visual acuity (UDVA) of 20/20 (efficacy) was 1.10 (95% CI, 0.66-1.83; P=.72), the pooled OR of achieving a result within ± 0.50 diopter of intended target (predictability) was 1.03 (95% CI, 0.60-1.75; P=.92), and the weighted mean difference in induced HOAs was -0.09 (95% CI, -0.17 to -0.01; P=.04). No study reported loss of 2 or more lines of Snellen acuity (safety) with either modality.

CONCLUSIONS

Metaanalysis showed no clear evidence of a benefit of wavefront-guided over non-wavefront-guided ablations. However, there was a lack of standardized reporting of UDVA better than 20/20, which might mask an advantage in wavefront-guided treatment. With high preexisting HOAs, wavefront-guided has advantages over non-wavefront-guided treatment.

Efficacy of brimonidine tartrate 0.2% ophthalmic solution in reducing halos after laser in situ keratomileusis

PURPOSE

To quantitatively evaluate the effect of brimonidine tartrate 0.2% (Alphagan) on halo and pupil size in patients who had symptomatic night-vision difficulties after laser in situ keratomileusis (LASIK).

SETTING

Nune Eye Hospital, Seoul, Korea.

METHODS

This study comprised 28 eyes of 14 patients with symptomatic night-vision difficulties after LASIK. Pupil diameter was measured with a Colvard pupillometer (Oasis Medical, Inc.). Quantitative analysis of halos was performed by measuring the area using a new computerized method. Pupil size and halo size were evaluated under scotopic and normal room light conditions. Alphagan was administered, and the effect was measured after 30 minutes and 1, 6, 12, and 24 hours.

RESULTS

There was a statistically significant correlation between pupil size and halo size (r = 0.527; P<.0001; slope = 691.6 pixel/mm). Pupil size and halo size decreased significantly 30 minutes after Alphagan instillation under both luminance conditions (all P< .0001). Under normal room light, the pupil and halo remained decreased until the last measurement at 24 hours. Under scotopic conditions, the pupil returned to its preinstillation size at 24 hours while the halo remained decreased. The maximum effect on halos was observed after 6 hours, when the mean reduction over preinstillation size was 28.2% and 29.1% under normal room light conditions and scotopic conditions, respectively.

CONCLUSION

Alphagan effectively reduced halo size and pupil size in postoperative LASIK patients with night-vision symptoms.

Pupil size and corneal laser surgery

PURPOSE OF REVIEW

The role of scotopic pupil size as a factor in predicting night vision complaints is controversial. This review summarizes reports in the literature, some that have found and some that have failed to find a correlation with scotopic pupil size and night vision complaints.

RECENT FINDINGS

Pupil-measuring devices are discussed along with informed consent issues and reports showing that wavefront aberrations increase with increasing pupil size. A new objective measuring device (Larson) showed a correlation with postoperative starbursts and pupil size and a decrease in starbursts with wavefront-guided treatments compared with conventional excimer laser treatments. Cortical adaptation allows many patients to adapt to their new night vision. Treatment options for those who remain symptomatic include drops to reduce pupil size and wavefront-guided retreatments.

SUMMARY

Reports in the literature are conflicting, and refractive surgeons would be wise to inform their patients that large scotopic pupil size is a potential risk factor for night vision complaints. By doing this they will follow the recommendations in recent patient information brochures of both VISX (Santa Clara, California) and Alcon (Orlando, Florida) and on the United States Food and Drug Administration web site.