Quality of vision after laser in situ keratomileusis: influence of dioptric correction and pupil size on visual function

Bibliometric and visualized analysis of myopic corneal refractive surgery research: from 1979 to 2022

Background

Myopic corneal refractive surgery is one of the most prevalent ophthalmic procedures for correcting ametropia. This study aimed to perform a bibliometric analysis of research in the field of corneal refractive surgery over the past 40 years in order to describe the current international status and to identify most influential factors, while highlighting research hotspots.

Methods

A bibliometric analysis based on the Web of Science Core Collection (WoSCC) was used to analyze the publication trends in research related to myopic corneal refractive surgery. VOSviewer v.1.6.10 was used to construct the knowledge map in order to visualize the publications, distribution of countries, international collaborations, author productivity, source journals, cited references, keywords, and research hotspots in this field.

Results

A total of 4,680 publications on myopic corneal refractive surgery published between 1979 and 2022 were retrieved. The United States has published the most papers, with Emory University contributing to the most citations. The Journal of Cataract and Refractive Surgery published the greatest number of articles, and the top 10 cited references mainly focused on outcomes and wound healing in refractive surgery. Previous research emphasized "radial keratotomy (RK)" and excimer laser-associated operation methods. The keywords containing femtosecond (FS) laser associated with "small incision lenticule extraction (SMILE)" and its "safety" had higher burst strength, indicating a shift of operation methods and coinciding with the global trends in refractive surgery. The document citation network was clustered into five groups: (1) outcomes of refractive surgery: (2) preoperative examinations for refractive surgery were as follows: (3) complications of myopic corneal refractive surgery; (4) corneal wound healing and cytobiology research related to photorefractive laser keratotomy; and (5) biomechanics of myopic corneal refractive surgery.

Conclusion

The bibliometric analysis in this study may provide scholars with valuable to information and help them better understand the global trends in myopic corneal refractive surgery research frontiers. Two stages of rapid development occurred around 1991 and 2013, shortly after the innovation of PRK and SMILE surgical techniques. The most cited articles mainly focused on corneal wound healing, clinical outcomes, ocular aberration, corneal ectasia, and corneal topography, representing the safety of the new techniques.

Beam-Shaping Extended Depth of Focus Intraocular Lens: Optical Assessment With Corneas of Increasing Spherical Aberration

PURPOSE

To assess the optical quality and halo formation of a beam-shaping extended depth-of-focus (EDOF) intraocular lens (IOL) (AcrySof IQ Vivity; Alcon Laboratories, Inc) with corneas of long-range spherical aberration (SA) such as those resulting from myopic laser ablations.

METHODS

The optical quality of the EDOF IOL and a reference monofocal IOL was evaluated with three corneas (A, B, and C, with SA =+0.135, +0.290, +0.540 µm, respectively, for a 5.15-mm pupil at the IOL plane). The through-focus modulation transfer function area (MTFa) curves were obtained between -5.00 and +2.00 diopters (D) defocus range. The halo was also assessed with the three corneas.

RESULTS

Through-focus MTFa curves for a 4.5-mm IOL pupil showed a slight decrease in the maximum MTFa value provided by the EDOF IOL compared to the monofocal IOL in the three corneal situations (A: 45.9 vs 38.6 units; B: 41.1 vs 33.1 units, and C: 26.9 vs 23.8 units). For the 3.0-mm pupil, the EDOF IOL also had lower maximum MTFa than the monofocal IOL; however, the depth-of-focus increased to -2.20 D. With corneas A and B, the halo induced was of low energy with both IOLs. With cornea C, the EDOF IOL created a much larger and intense halo.

CONCLUSIONS

The EDOF IOL provided a good distance optical performance and an extended range of focus of approximately 2.00 D, with a halo of low intensity when evaluated with a corneal SA similar to the one induced by a low to moderate myopic ablation. With a high myopic ablation, the halo induced would be of considerable size and energy. [J Refact Surg. 2023;39(2):95-102.].

Tolerance to Residual Refractive Errors After Trifocal and Trifocal Toric Intraocular Lens Implantation

OBJECTIVE

The objective of this study was to assess the impact of 0.50 diopter (D) positive or negative defocus on visual function in patients implanted with trifocal and trifocal toric intraocular lenses (IOLs).

METHODS

The study included patients implanted with the AcrySof IQ PanOptix IOL or the PanOptix Toric. Visual acuity (VA) at high (100%), medium (50%) and low (10%) contrast, contrast sensitivity function (CSF), and halo perception were assessed three months after surgery. Explorations were performed with corrected distance visual acuity (CDVA), with a positive defocus of +0.50D (myopization) and with a negative defocus of -0.50D (hyperopization).

RESULTS

The study included 60 eyes of 60 patients (30 eyes with PanOptix and 30 eyes with PanOptix Toric). For both groups, VA was better for all contrast settings at the CDVA situation (P<0.05 in all cases). For low spatial frequencies, no differences in CSF were found among the three refractive situations in either group. For higher frequencies, the results showed an overall trend for better CSF results for the CDVA situation. The halo effect was lower for the CDVA situation if compared to myopization and hyperopization in both the PanOptix and the PanOptix Toric groups (P<0.05 for all cases).

CONCLUSIONS

There is an impact on visual quality and halo perception in patients implanted with trifocal or trifocal toric IOLs even for low residual refractive errors.

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.].

Hyperopic Q-optimized algorithms: a theoretical study on factors influencing optical quality

In this work, we analyze the way in which pupil size, optical zone, and initial hyperopic level influence optical quality for hyperopic Q-optimized corneal refractive surgery. Different Q-optimized algorithms and the Munnerlyn formula were tested to analyze the optical quality of the final retinal image for initial hyperopic errors from 1D to 5D. Three optical zones (5.5, 6, and 6.5 mm) and two pupil diameters (5 and 7 mm) were considered. To evaluate optical quality, we computed the modulation transfer function (MTF) and the area under MTF (MTFa). Q-optimized values at around Q = -0.18 were found to provide the best optical quality for most of the conditions tested. This optimum final asphericity for hyperopic ablation was not depending on the degree of hyperopia corrected, the optical zone or the pupil size being this information important for clinical practice.

Individual Differences in Scotopic Visual Acuity and Contrast Sensitivity: Genetic and Non-Genetic Influences

Despite the large amount of variation found in the night (scotopic) vision capabilities of healthy volunteers, little effort has been made to characterize this variation and factors, genetic and non-genetic, that influence it. In the largest population of healthy observers measured for scotopic visual acuity (VA) and contrast sensitivity (CS) to date, we quantified the effect of a range of variables on visual performance. We found that young volunteers with excellent photopic vision exhibit great variation in their scotopic VA and CS, and this variation is reliable from one testing session to the next. We additionally identified that factors such as Circadian preference, iris color, astigmatism, depression, sex and education have no significant impact on scotopic visual function. We confirmed previous work showing that the amount of time spent on the vision test influences performance and that laser eye surgery results in worse scotopic vision. We also showed a significant effect of intelligence and photopic visual performance on scotopic VA and CS, but all of these variables collectively explain <30% of the variation in scotopic vision. The wide variation seen in young healthy volunteers with excellent photopic vision, the high test-retest agreement, and the vast majority of the variation in scotopic vision remaining unexplained by obvious non-genetic factors suggests a strong genetic component. Our preliminary genome-wide association study (GWAS) of 106 participants ruled out any common genetic variants of very large effect and paves the way for future, larger genetic studies of scotopic vision.

Four-year follow-up of corneal aberrations and visual functions of myopic patients after laser in situ keratomileusis

Objective:

To report on 4-year follow-up of corneal higher-order aberrations and daily visual functions of myopic patients after laser in situ keratomileusis (LASIK).

Methods:

One hundred thirty four eyes of 67 patients who underwent LASIK guided by aspherical ablation were included in this study. The vision, corneal spherical aberration (SphA) and Coma were recorded before LASIK and at 6 month and 4 year after LASIK. The evaluation of the questionnaire about daily visual functions was performed by the same physician after LASIK.

Results:

No eye decreased the BCVA during 4 year follow-up. The effect index and safety index were 1.08±0.16, 1.11±0.17 and 1.12±0.16, 1.13±0.14 respectively at 6 month and 4 year post-LASIK. After LASIK the corneal SphA and Coma were significantly increased, however the difference between 6 month and 4 year post-LASIK was no statistical significance. Most patients (94.3%-92.4%) felt satisfaction or high satisfaction about the ability to perform each daily visual function after LASIK. Meanwhile there was still about 7.4%-9.2% patients who complained that they could not drive at night. Further analysis showed that the score of driving at night was negative correlation with corneal SphA (r=-0.645, p=0.040; r=-0.688, p=0.040 at 6 month and 4 year post-LASIK respectively).

Conclusions:

Our four-year follow-up outcomes indicated that the myopic patients after LASIK had the long-term stable corneal aberration and satisfaction of daily visual functions.

Effect of postoperative keratometry on quality of vision in the postoperative period after myopic wavefront-guided laser in situ keratomileusis

PURPOSE

To determine whether postoperative keratometry is a predictor of patient-reported satisfaction and night-vision phenomena after wavefront-guided myopic laser in situ keratomileusis (LASIK).

SETTING

Optical Express, Glasgow, United Kingdom.

DESIGN

Retrospective case series.

METHODS

Myopic eyes treated with wavefront-guided LASIK were analyzed in this study. All patients completed pre-operative and 1-month postoperative questionnaires, in which the satisfaction with visual outcomes and pre-operative and postoperative night-vision symptoms (glare, halos, starburst, ghosting/double-vision) were rated. Multivariate regression analysis was performed to determine factors associated with questionnaire outcomes.

RESULTS

This study evaluated 8672 myopic eyes of 4602 patients. The mean pre-operative manifest spherical equivalent was -3.72 diopters (D) ± 2.00 (SD) (range -0.50 to -11.00 D) and the mean pre-operative keratometry (K) value was 43.64 ± 1.43 D (38.38 to 49.00). At 1 month after surgery, 93.7% and 99.1% of eyes were within 0.50 D and 1.00 D of emmetropia, and 94.6% and 98.3% of eyes achieved monocular and binocular uncorrected-distance visual acuity(UDVA) of 20/20 or better, respectively. There were 48.7% of eyes that had the flat corneal meridian (minimum K) of 40.0 D or less. Although postoperative keratometry was a significant predictor of patient-reported satisfaction and the change in halo reports in the regression analysis, its relative contribution was very low and accounted for less than 0.50% of the variance explained by either model. Postoperative keratometry was not a significant predictor of a change in reports of glare, starburst, and ghosting or double vision.

CONCLUSION

In this large cohort of patients, postoperative keratometry played a minimal and clinically insignificant role in predicting post-LASIK halo visual phenomena and patient-reported satisfaction.

FINANCIAL DISCLOSURE

Dr. Schallhorn is a consultant to Abbott Medical Optics and Zeiss and a Global Medical Director for Optical Express. None of the other authors have a financial or proprietary interest in the products and materials presented in this paper.

Pupil Diameter Changes in High Myopes after Collamer Lens Implantation

PURPOSE

To observe the changes in pupil size under photopic and scotopic conditions after Implantable Collamer Lens (ICL) implantations in eyes with high myopia.

METHODS

The ICL was implanted in 90 eyes belonging to 45 patients with high myopia. Photopic pupil diameters, scotopic pupil diameters, anterior chamber depths, and ICL vaults were examined at the preoperative, postoperative 1-month, and postoperative 3-month stages. The preoperative and postoperative photopic pupil diameters and scotopic pupil diameters were also compared with each other to note the differences between them. The correlations between preoperative and postoperative pupil diameter changes under different light conditions and presurgical refractive error were analyzed alongside patient's age and ICL vault.

RESULTS

Pupil diameters at both postoperative 1-month and postoperative 3-month stages were smaller than those before operation in distinct light environments, as well as pupil constriction amplitude. Correlation analysis showed that there was a statistically significant correlation between pupil diameter changes under different light conditions and presurgical refractive error at 1 month and 3 months after ICL implantation; pupil diameter decreased more when presurgical refractive error powers were less myopic. Statistically significant correlations were not found, however, with patient's age and ICL vault. Postoperative 1-month and mean postoperative 3-month anterior chamber depths were decreased when compared with preoperative anterior chamber depths. Statistically significant correlations were found in change in preoperative and postoperative anterior chamber depth and ICL vault. No statistically significant difference was found between ICL vault at the postoperative 1-month and postoperative 3-month stages.

CONCLUSIONS

Pupil diameter may decrease at the 1- and 3-month stages after ICL implantation under both photopic and scotopic conditions. This indicates that reduction of pupil diameter may be caused by mechanical contact between the ICL and the posterior iris surface.

Comparison of visual outcomes after variable spot scanning ablation versus wavefront-optimized myopic LASIK

PURPOSE

To compare the refractive and visual outcomes of variable spot scanning ablation versus the wavefront-optimized ablation for myopia and myopic astigmatism.

METHODS

Fifty patients with myopia who underwent LASIK (100 eyes) were divided into two equal groups. Myopic correction performed using the variable spot scanning (VSS) ablation with the VISX STAR S4/IR platform (Abbott Medical Optics, Inc., Santa Ana, CA) (VSS group) and wavefront-optimized (WFO) ablation profile with the WaveLight Allegretto Wave Eye-Q platform (Alcon Laboratories, Inc., Fort Worth, TX) (WFO group). Manifest refraction, uncorrected distance visual acuity, and corrected distance visual acuity were obtained preoperatively and 1 day and 1 and 3 months postoperatively. Wavefront measurement and contrast sensitivity testing were done preoperatively and 3 months postoperatively.

RESULTS

Postoperative mean refractive spherical equivalent was -0.14 ± 0.2 diopters for the VSS group and -0.15 ± 0.28 diopters for the WFO group. Forty-eight eyes of the VSS group and 47 eyes of the WFO group were within ±0.5 diopters. Postoperative mean corrected distance visual acuity was 1.05 ± 0.13 for the VSS group and 1.06 ± 0.12 for the WFO group. The postoperative uncorrected distance visual acuity was 1.01 ± 0.16 for the VSS group and 1.01 ± 0.11 for the WFO group. The safety index was 1.12 for the VSS group and 1.06 for the WFO group, whereas the efficacy index was 1.07 for the VSS group and 1.01 for the WFO group. The mean induced positive spherical aberration was 0.041 ± 0.046 µm for the VSS group and 0.195 ± 0.171 µm for the WFO group (P < .001). Mesopic contrast sensitivity testing showed no statistically significant differences between groups at all tested spatial frequencies.

CONCLUSIONS

Both VSS and WFO treatments showed similar refractive and visual outcomes. Both induced significant positive spherical aberration, significantly more with WFO.

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.

Changes in contrast sensitivity after surgery for macula-on rhegmatogenous retinal detachment

PURPOSE

To evaluate changes in contrast sensitivity after surgery for macula-on rhegmatogenous retinal detachment (RRD).

DESIGN

Prospective, interventional, consecutive, case-control study.

METHODS

This study included 84 eyes of 84 patients with unilateral macula-on RRD undergoing primary scleral buckling or vitrectomy without postoperative macular complication. We examined the logarithm of the minimal angle of resolution best-corrected visual acuity (logMAR BCVA) and contrast sensitivity at 4 spatial frequencies (3, 6, 12, and 18 cycles/degree) using the CSV-1000E (Vector Vision) before and after surgery. From the data obtained with the CSV-1000E, the area under the log contrast sensitivity function was calculated. The logMAR BCVA and contrast sensitivity in the contralateral normal eyes also were measured and were used as normal controls. Clinical data were collected, including age, gender, surgical procedures, the number of retinal tears, circumferential dimension of retinal tears, and area of retinal detachment, to determine the clinical factors related to visual function.

RESULTS

Preoperative contrast sensitivity was significantly worse in eyes with RRD than in normal controls, but the preoperative logMAR BCVA was not different from that of normal controls. Contrast sensitivity decreased significantly after surgery, but logMAR BCVA did not change by surgery. Multiple regression analysis revealed that postoperative contrast sensitivity had a significant correlation with the circumferential dimension of retinal tears, whereas no clinical parameters were associated significantly with postoperative BCVA.

CONCLUSIONS

Surgery for macula-on RRD did not change visual acuity, whereas contrast sensitivity was affected significantly in association with the extent of retinal tears.

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

Mesopic pupil size in a refractive surgery population (13,959 eyes)

PURPOSE

To evaluate factors that may affect mesopic pupil size in refractive surgery candidates.

METHODS

Medical records of 13,959 eyes of 13,959 refractive surgery candidates were reviewed, and one eye per subject was selected randomly for statistical analysis. Detailed ophthalmological examination data were obtained from medical records. Preoperative measurements included uncorrected distance visual acuity, corrected distance visual acuity, manifest and cycloplegic refraction, topography, slit lamp examination, and funduscopy. Mesopic pupil size measurements were performed with Colvard pupillometer. Relationship between mesopic pupil size and age, gender, refractive state, average keratometry, and pachymetry (thinnest point) were analyzed by means of ANOVA (+ANCOVA) and multivariate regression analyses.

RESULTS

Overall mesopic pupil size was 6.45 ± 0.82 mm, and mean age was 36.07 years. Mesopic pupil size was 5.96 ± 0.8 mm in hyperopic astigmatism, 6.36 ± 0.83 mm in high astigmatism, and 6.51 ± 0.8 mm in myopic astigmatism. The difference in mesopic pupil size between all refractive subgroups was statistically significant (p < 0.001). Age revealed the strongest correlation (r = -0.405, p < 0.001) with mesopic pupil size. Spherical equivalent showed a moderate correlation (r = -0.136), whereas keratometry (r = -0.064) and pachymetry (r = -0.057) had a weak correlation with mesopic pupil size. No statistically significant difference in mesopic pupil size was noted regarding gender and ocular side. The sum of all analyzed factors (age, refractive state, keratometry, and pachymetry) can only predict the expected pupil size in <20% (R = 0.179, p < 0.001).

CONCLUSIONS

Our analysis confirmed that age and refractive state are determinative factors on mesopic pupil size. Average keratometry and minimal pachymetry exhibited a statistically significant, but clinically insignificant, impact on mesopic pupil size.

Visual simulation through an aspheric aberration-correcting intraocular lens in subjects with different corneal profiles using adaptive optics

BACKGROUND

The aim of this study was to analyse the visual quality of the AcrySof IQ SN60WF(®) intraocular lens (IOL) when combined with different corneal profiles.

METHODS

Ten eyes of 10 participants with no prior history of refractive or cataract surgery were evaluated. An adaptive optics visual simulator was used to simulate the wavefront aberration pattern of an aspheric aberration-correcting IOL (AcrySof IQ SN60WF(®)). Normal corneas (group A), low and high myopic corneal ablations (groups B and C, respectively) and low and high hyperopic corneal ablations (groups D and E, respectively) were also simulated. Monocular distance visual acuities at 100, 50 and 10 per cent of contrast were measured.

RESULTS

At 100, 50 and 10 per cent contrast, no differences were found between groups A and B (p > 0.06 for all contrasts). Group A obtained better values than groups C, D and E for all contrasts (p = 0.031, p = 0.038, p = 0.032 at 100, 50 and 10 per cent of contrast, respectively). At the same time, group B obtained better values than groups C, D and E (p = 0.041, p = 0.042, p = 0.036 at 100, 50 and 10 per cent of contrast, respectively). Within the five groups, the worst results were always obtained for group E (p = 0.017, p = 0.021 and p = 0.025 at 100, 50 and 10 per cent of contrast, respectively).

CONCLUSIONS

The results suggest that the aspheric aberration-correcting IOL studied provides comparable results, when it is combined with normal corneas and with corneas with simulated low myopic ablations. When negative amounts of residual spherical aberration after cataract surgery are expected to be achieved, IOLs with more positive spherical aberration should be considered.

One year follow-up of contrast sensitivity following conventional laser in situ keratomileusis and laser epithelial keratomileusis

PURPOSE

To determine the effect of conventional laser in situ keratomileusis (LASIK) and laser epithelial keratomileusis (LASEK) for myopia on contrast sensitivity (CS) using the Pelli-Robson and Vector Vision CSV-1000E CS tests.

METHODS

A prospective, comparative study was conducted on 36 eyes of 36 patients with myopia undergoing LASIK (18 eyes) and LASEK (18 eyes). Surgery was performed using the Technolas 217z laser (Bausch & Lomb). CS was recorded preoperatively and at 3, 6 and 12 months postoperatively.

RESULTS

No statistically significant difference was found in LogMAR uncorrected visual acuity post-LASIK (-0.02 ± 0.16) and LASEK (-0.04 ± 0.14). Using the Pelli-Robson, CS was significantly lower in the LASIK group 3 and 6 months postoperatively. No significant postoperative reduction in CS was observed in either treatment group. Using the CSV-1000E test, CS was significantly reduced post-LASIK at 3 (p = 0.05) and 6 (p = 0.05) cycles/degree under photopic conditions. No significant postoperative change occurred in the LASEK group under photopic or scotopic conditions. There was no significant difference in postoperative CS between the LASIK and LASEK groups at 3, 6, 12 or 18 cycles/degree using the CSV-1000E test.

CONCLUSION

One year postoperatively, there was no difference in CS between both treatment groups using the Pelli-Robson and CSV-1000E tests. CS was reduced postoperatively in the LASIK group at the lower spatial frequencies under photopic conditions. No postoperative change was detected in CS following LASIK or LASEK using the Pelli-Robson test.

Effect of preoperative pupil size on quality of vision after wavefront-guided LASIK

PURPOSE

To evaluate the effect of preoperative pupil size on quality of vision after wavefront-guided LASIK.

DESIGN

Prospective study.

PARTICIPANTS

One hundred two eyes.

INTERVENTION

LASIK for mild to moderate myopia or astigmatism (preoperative manifest spherical equivalent, -3.99±1.42 diopters).

MAIN OUTCOME MEASURES

Questionnaires evaluating specific visual symptoms before and after surgery. Each eye was evaluated before surgery, and 1 week and 1, 3, 6, and 12 months postoperatively. Pupils were stratified according to size: small (≤5.5 mm), medium (5.6-6.4 mm), or large (≥6.5 mm). Mesopic pupil size and preoperative and postoperative variables were evaluated using an analysis of variance. A regression model was also performed to determine the correlation between mean spherical equivalent and cylinder and visual symptoms.

RESULTS

In the early postoperative period, there was no difference between the 3 groups with regard to any of the symptoms. At the final 12-month postoperative visit, patients with medium pupils experienced less glare at night than small pupils (P = 0.02), medium pupils had less halos than small or large pupils (P = 0.001 and P = 0.02, respectively), and medium pupils experienced greater satisfaction in visual improvement than small pupils (P = 0.014).

CONCLUSIONS

Twelve months after wavefront-guided LASIK surgery, large pupil size does not positively correlate with any postoperative visual symptoms.

Changes in wave-front aberrations after rigid gas permeable contact lens fitting in post-laser in situ keratomileusis patients with visual complaints

OBJECTIVE

To evaluate the effect of rigid gas permeable (RGP) contact lenses in reducing wave-front aberrations in post-laser in situ keratomileusis (LASIK) myopic patients.

DESIGN

Cross-sectional study.

PARTICIPANTS

Thirty patients with visual complaints after conventional LASIK procedure for correcting myopia.

METHODS

The 30 patients were fitted with RGP contact lenses. Wave-front measurements were taken before and after RGP contact lens wearing.

RESULTS

Compared with bare eye examinations, root mean-square values of higher-order aberrations (HOAs) significantly decreased with RGP contact lens use. Among these, spherical aberration decreased from 0.507 (SD 0.304) microm to 0.164 (SD 0.121) microm (t = 7.186, p < 0.001); coma decreased from 0.470 (SD 0.312) microm to 0.165 (SD 0.090) microm (t = 5.566, p < 0.001); secondary coma decreased from 0.079 (SD 0.050) microm to 0.044 (SD 0.027) m (t = 4.118, p < 0.001); and total HOAs decreased from 0.782 (SD 0.449) microm to 0.307 (SD 0.140) microm (t = 6.710, p < 0.001).

CONCLUSIONS

Fitting RGP contact lenses effectively decreased HOAs induced by conventional myopic LASIK surgery. Possible reasons may be the elimination of irregularity and dissymmetry on the corneal anterior surface, relief of the aspherical extent of the central corneal surface, and enlargement of the effective optical zone.

Reverse geometry rigid gas permeable contact lens wear reduces high-order aberrations and the associated symptoms in post-LASIK patients

PURPOSE

This study evaluated the efficacy of custom-made reverse geometry rigid gas permeable (RGP) contact lenses in the control of symptoms related to increased wavefront aberrations after LASIK correction of myopia.

MATERIALS AND METHODS

Twenty-eight myopes treated with LASIK were assessed for post-LASIK symptoms (declined night vision, glare, halos and/or monocular diplopia) and corneal topography. A set of RGP contact lenses was selected as trial lenses based on the matching between the lens and the patient's corneal topography. If the fluorescein pattern between the trial lens and the corneal surface showed a central alignment, a mid-peripheral bearing and peripheral clearance and if the patient felt comfortable with the lens wear, a duplicated lens was ordered for the patient. Otherwise, a lens satisfied with corneal topography of the patient and clinical judgment was used. Visual acuity (VA) and wavefront aberrations were measured after the lens wear.

RESULTS

The custom-made lenses well matched the host cornea with no dislodgment in all subjects. The post-LASIK eyes showed an increase of 1 Snellen line in VA (from 0.90 +/- 0.33 to 1.11 +/- 0.24) and a significant improvement in all symptoms after the lens wear. The total higher-order aberration is significantly reduced after the lens wear with at least 70% reduction in either spherical aberration, coma, third or fourth aberration but only 33% reduction in the fifth aberration.

CONCLUSIONS

Reverse geometry RGP lenses with the design based on individual topographic data can improve visual performance of post-LASIK eyes by reducing higher order aberrations.

Correlation of aberrometry, contrast sensitivity, and subjective symptoms with quality of vision after LASIK

PURPOSE

To compare which parameter category (wavefront data, psychophysical data, or subjective symptoms) predicts best subjective quality of vision after LASIK.

METHODS

Twenty-eight eyes (15 patients) were included. Twenty-three eyes (12 patients) underwent uneventful LASIK; 5 eyes (3 patients) were symptomatic eyes treated with myopic LASIK elsewhere. Mean preoperative spherical equivalent refraction was -4.79+/-1.92 diopters (D) (range: -1.63 to -7.13 D); mean patient age was 36.6+/-7.4 years (range: 18 to 48 years). All examinations were performed 1 month postoperatively. The wavefront error was described with Zernike polynomials (6-mm pupil). Psychophysical tests included high-contrast visual acuity and contrast sensitivity with and without glare at 167 cd/m(-2), 1.67 cd/m(-2), and 0.167 cd/m(-2) with best spectacle correction. Correspondingly, overall subjective quality of vision and frequency of visual symptoms (glare, halos, starbursts, ghosting, blur) were assessed for three lighting conditions (photopic, high-mesopic, and low-mesopic) using a questionnaire with a visual analog scale. For each parameter category and each lighting condition, a multiple stepwise backwards regression model with the overall quality of vision item value as dependent was applied.

RESULTS

Under all lighting conditions, subjective symptom scores predicted subjective quality of vision best (adjusted R2=0.83-0.92) with blur as the main predictor throughout all conditions. Psychophysical tests did not significantly predict postoperative subjective quality of vision. The adjusted R2 for the Zernike coefficients was highest for low-mesopic (0.56) and lowest for photopic conditions (0.31).

CONCLUSIONS

Different parameter categories for the description of optical quality did not predict subjective quality of vision after LASIK equally. Subjective symptom scores had the highest predictability, whereas psychophysical tests with spectacle correction had no predictability. The latter probably do not reflect all dimensions of subjective quality of vision.

Wavefront-guided versus wavefront-optimized laser in situ keratomileusis: contralateral comparative study

PURPOSE

To compare the outcomes of wavefront-guided and wavefront-optimized treatment in fellow eyes of patients having laser in situ keratomileusis (LASIK) for myopia.

SETTING

Medical and Vision Research Foundation, Tamil Nadu, India.

METHODS

This prospective comparative study comprised 27 patients who had wavefront-guided LASIK in 1 eye and wavefront-optimized LASIK in the fellow eye. The Hansatome (Bausch & Lomb) was used to create a superior-hinged flap and the Allegretto laser (WaveLight Laser Technologie AG), for photoablation. The Allegretto wave analyzer was used to measure ocular wavefront aberrations and the Functional Acuity Contrast Test chart, to measure contrast sensitivity before and 1 month after LASIK. The refractive and visual outcomes and the changes in aberrations and contrast sensitivity were compared between the 2 treatment modalities.

RESULTS

One month postoperatively, 92% of eyes in the wavefront-guided group and 85% in the wavefront-optimized group had uncorrected visual acuity of 20/20 or better; 93% and 89%, respectively, had a postoperative spherical equivalent refraction of +/-0.50 diopter. The differences between groups were not statistically significant. Wavefront-guided LASIK induced less change in 18 of 22 higher-order Zernike terms than wavefront-optimized LASIK, with the change in positive spherical aberration the only statistically significant one (P= .01). Contrast sensitivity improved at the low and middle spatial frequencies (not statistically significant) and worsened significantly at high spatial frequencies after wavefront-guided LASIK; there was a statistically significant worsening at all spatial frequencies after wavefront-optimized LASIK.

CONCLUSION

Although both wavefront-guided and wavefront-optimized LASIK gave excellent refractive correction results, the former induced less higher-order aberrations and was associated with better contrast sensitivity.

Mesopic contrast sensitivity and ocular higher-order aberrations after overnight orthokeratology

PURPOSE

To investigate mesopic contrast sensitivity and night driving ability in eyes undergoing overnight orthokeratology, and to analyze the relationship among mesopic contrast sensitivity, ocular higher-order aberrations, and myopic correction.

DESIGN

Prospective, noncomparative, consecutive case series.

METHODS

In 44 eyes of 22 subjects (mean age +/- standard deviation [SD], 24.0 +/- 3.2 years) with orthokeratology, ocular aberrations and mesopic contrast sensitivity were determined before and three months after commencement of the procedure. Mean spherical equivalent refraction +/- SD was -2.34 +/- 0.99 diopters at baseline. Mesopic contrast sensitivity with and without glare was assessed using the Mesotest II (Oculus, Wetzlar, Germany).

RESULTS

Orthokeratology significantly reduced the log mesopic contrast sensitivity from 0.25 +/- 0.08 to 0.08 +/- 0.10 without glare (P < .0001, Wilcoxon) and from 0.21 +/- 0.11 to 0.07 +/- 0.10 with glare (P < .0001). The proportion of eyes that fulfilled the German standard recommendation level for night driving was 36%. The induced changes in log mesopic contrast sensitivity showed significant negative correlation with the changes in third-order (r = -0.490, P = .0013 without glare; r = -0.362, P = .0177 with glare; Spearman rank correlation coefficient) and fourth-order root mean square (r = -0.586, P = .0001 and r = -0.306, P = .0450, respectively). Furthermore, significant correlation was found between the amount of myopic correction and the induced changes in log mesopic contrast sensitivity (r = -0.442, P = .0038 without glare; r = -0.464, P = .0024 with glare). The induced changes in higher-order aberrations significantly correlated with the amount of myopic correction (P < .0001, Pearson correlation coefficient).

CONCLUSIONS

Mesopic contrast sensitivity after overnight orthokeratology is deteriorated significantly as ocular higher-order aberrations increase, and these changes depend on the amount of myopic correction.

Effect of a yellow intraocular lens on scotopic vision, glare disability, and blue color perception

PURPOSE

To compare the photopic and scotopic contrast sensitivity with and without glare as well as blue color perception between eyes with an AcrySof SN60AT Natural intraocular lens (IOL) (Alcon Laboratories Inc.) and eyes with a conventional AcrySof SA60AT IOL.

SETTING

Ankara University School of Medicine, Department of Ophthalmology, Ankara, Turkey.

METHODS

Right eyes of 38 patients with an AcrySof Natural IOL and right eyes of 38 age-matched patients with a conventional AcrySof SA60AT IOL were included in a study. Contrast sensitivity was measured with the Functional Acuity Contrast Test under photopic conditions. Scotopic contrast sensitivity in the presence or absence of glare was measured using the Mesotest II (Oculus GmbH). Blue-green color vision was evaluated with the Moreland equation of the HMC Anomaloskop MR (Oculus GmbH).

RESULTS

The mean age of patients was 66.6 years +/- 8.2 (SD) in the Natural IOL group and 66.4 +/- 8.0 years in the conventional IOL group. There was no statistically significant difference in photopic contrast sensitivity, scotopic contrast sensitivity with and without glare, or disability glare between the 2 groups (P>.05). Photopic and scotopic contrast sensitivity with and without glare significantly decreased with age in both groups (P<.01). There was no statistically significant difference in anomaloscope scores between the 2 groups (P>.05). The Moreland middle match point showed a significant shift toward blue with age in both groups (P<.01).

CONCLUSIONS

The AcrySof SN60AT Natural IOL provided contrast sensitivity under photopic and scotopic conditions (with and without glare) and blue color perception comparable that obtained with the AcrySof SA60AT IOL. Scotopic vision and blue color discrimination decreased with age with both IOLs.

Contrast Sensitivity After LASIK, LASEK, and Wavefront-guided LASEK With the VISX S4 Laser

PURPOSE

To evaluate the changes in contrast sensitivity and glare after corneal refractive surgery for moderate myopia.

METHODS

The study comprised 267 eyes of 149 patients who underwent LASIK, laser epithelial keratomileusis (LASEK), or wavefront-guided LASEK with the VISX STAR S4. Contrast sensitivity was measured with VCTS 6500 before surgery and at 2 and 6 months postoperatively. Glare was evaluated using questionnaires and the ALC glare test at last follow-up. Contrast sensitivity at 2 and 6 months was compared with preoperative contrast sensitivity in each group. Glare sensitivity in each group was compared to normal controls.

RESULTS

Contrast sensitivity did not change after LASIK (P > .05). Contrast sensitivity of 3 and 6 cycles per degree (cpd) at 2 months increased after LASEK (P < .05) and contrast sensitivity of 6, 12, and 18 cpd at 2 months and 3, 6, 12, and 18 cpd at 6 months improved in wavefront-guided LASEK (P < .05). Glare test and questionnaires did not show any significant difference between the groups.

CONCLUSIONS

Wavefront-guided LASEK induced significant increases in contrast sensitivity of moderate myopes at high spatial frequencies under mesopic conditions by 6 months. Glare was not affected by the different refractive procedures.

[Study of pupillary motility after implantation of an iris claw lens (Artisan) in a phakic population with severe myopia]

PURPOSE

To assess the effect of the Artisan lens on pupillary motility in a highly phakic myopic population.

PATIENTS AND METHODS

Eleven patients (21 eyes) were enrolled in a nonrandomized prospective study between September 2002 and August 2003, with a 6- to 11-month follow-up. A portable Colvard pupillometer was used to measure pupil diameters before and after surgery under two different light conditions: one with scotopic surroundings with absolute darkness in the examination room and the other maximal simulated photopic surroundings, caused by the instillation of a pilocarpine 2% drug until a nonreactive myosis could be observed. Under such light conditions, both the horizontal and vertical pupil motion ranges were measured. Measures were then sorted into five temporal segments in order to have enough samples per temporal segment for a cohesive data analysis. Mean values and confidence intervals were then derived per temporal segment according to Student's law. Constraints on the pupil motion range were identified.

RESULTS

After implantation of an Artisan lens, the pupil motion range was limited to both horizontal and vertical axes. For the horizontal axis, the motion range was 4.3+/-0.2mm (p=0.1) before claw implantation and was 2.7+/-0.5mm (p=0.1) 9 months after claw implantation. For the vertical axis, the motion range was 4.46+/-0.28mm before claw implantation and 3.08+/-0.89mm 9 months after claw implantation.

CONCLUSIONS

The Artisan lens durably restrains the pupil in its motion range and introduces a noticeable oval deformation under extreme light condition variations. This side effect is, however, not visible under regular conditions but only in maximal photopic surroundings.

Inter- and Intraobserver Reliability of Pupil Diameter Measurement During 24 Hours Using the Colvard Pupillometer

PURPOSE

To evaluate the inter- and intraobserver agreement of pupil size diameter measurements determined using the Colvard pupillometer.

METHODS

The eyes of 69 patients were examined (T1) using the Colvard pupillometer under mesopic and scotopic conditions by two examiners and repeated 1 hour (T2) and 24 hours (T3) later. The limits of agreement (mean difference between measurements +/- 2 standard deviations) were calculated for measurements between examiners (inter-examiner agreement) and between different time points measured by the same examiner (intra-examiner agreement).

RESULTS

At T1, there was a 99% and a 97% chance of two different examiners producing readings within 0.5 mm under mesopic and scotopic conditions, respectively. There was a 15% chance and a 9% chance of finding a pupil difference > 0.5 mm over 1 hour under mesopic and scotopic conditions, respectively. For mesopic and scotopic measurements taken 24 hours apart, there was a 31% chance and a 21% chance, respectively, of finding a difference > 0.5 mm by the same examiner.

CONCLUSIONS

This study showed high interobserver agreement under scotopic conditions, with 98% of measurements between two examiners falling within 0.5 mm, but substantial variability in pupil diameter measurements over 24 hours. These results suggest that serial office measurements may be necessary to establish the true range of pupil size.

Night vision disturbances after successful LASIK surgery

OBJECTIVE

To evaluate the changes in correlations of higher order aberrations of the first corneal surface with halo phenomena, a form of image degradation, under night vision conditions measured objectively after successful LASIK (laser in situ keratomileusis) surgery.

METHODS

A prospective, observational, analytical study of 110 eyes that had undergone successful LASIK surgery for myopia and astigmatism. Preoperative sphere was (mean (SD)) -3.48 (1.70) D (0 to -8.00 D) and preoperative cylinder was -0.86 (0.87) D (0 to -4.00 D). Visual disturbance caused by halo phenomena was measured with the Starlights v1.0, and pupil size was measured with Colvard pupilometry after adaptation to a dark environment (0.17 lux). Corneal aberrations were computed for a corneal diameter representative of the eye's entrance pupil under night vision conditions.

RESULTS

The halo disturbance index increased in this study by a factor of 2.15 after successful LASIK surgery. Total root mean square for monochromatic higher order aberration displayed a significant correlation with halo disturbance index (r = 0.42; p<0.01). However, only secondary astigmatism (r = 0.36; p<0.01), coma (r = 0.25; p = 0.02) and spherical aberration (r = 0.40; p<0.01) were responsible for such behaviour, with the remaining corneal aberrations up to the sixth order not displaying any significant correlation when considered individually.

CONCLUSION

Patients undergoing LASIK procedures display an increase of halo phenomena around lights in night vision conditions, even when the results of the surgery are considered entirely satisfactory according to current international standards of predictability, efficacy and safety. Secondary astigmatism, coma and spherical aberration are the higher order aberrations up to the sixth order that significantly correlated with halo disturbance index.

Uses and complications of mitomycin C in ophthalmology

Mitomycin C is a chemotherapeutic agent that acts by inhibiting DNA synthesis. Its use and application in ophthalmology has been increasing in recent years because of its modulatory effects on wound healing. Current applications include pterygium surgery, glaucoma surgery, corneal refractive surgery, cicatricial eye disease, conjunctival neoplasia and allergic eye disease. Although it has been used successfully in these conditions, it has also been associated with significant complications. This article reviews the current trends and uses of mitomycin C in the eye and its reported complications.

The relationship between anterior corneal aberrations and contrast sensitivity in conventional LASIK

PURPOSE

To evaluate the changes of anterior corneal aberrations before and after laser in situ keratomileusis (LASIK) and to assess the correlation between contrast sensitivity and anterior corneal aberrations.

METHODS

Right eyes of 51 patients including 6 males and 45 females undergoing conventional LASIK from September 2000 to July 2003 were enrolled. The calculation of anterior corneal aberrations before and after LASIK was obtained by analyzing the corneal topography from TMS-1 by using VOL-CT Version 6.23 software. Contrast sensitivity was measured after LASIK with an MCT 8000 under daytime and nighttime settings and with glare conditions. The differences of the Zernike coefficients and root mean square (RMS) of anterior corneal aberrations before and after LASIK were analyzed. The changes of contrast sensitivity at 1.5, 3, 6, 12, and 18 cpd were added separately for daytime and nighttime contrast sensitivity with and without glare after LASIK and were correlated with the changes of anterior corneal aberrations.

RESULTS

Vertical coma, RMS of coma-like RMS of spherical-like, RMS of trefoil-like and RMS of higher-order anterior corneal aberrations increased significantly after LASIK surgery. There were no significant correlations between the changes of anterior corneal aberrations and the changes of contrast sensitivity at daytime and nighttime, with and without glare. Contrast sensitivity at daytime and nighttime decreased at each spatial frequency after LASIK.

CONCLUSIONS

LASIK surgery induces changes of the anterior corneal aberrations. However, changes in anterior corneal aberrations did not correlate with the changes of contrast sensitivity at daytime and nighttime, with and without glare.

Binocular Visual Performance After LASIK

PURPOSE

To analyze binocular visual function after LASIK.

METHODS

Eye aberrometry and corneal topography was obtained for both eyes in 68 patients (136 eyes). To evaluate visual performance, monocular and binocular contrast sensitivity function and disturbance index for quantifying halos were measured. Tests were performed under mesopic conditions.

RESULTS

Binocular summation and disturbance index diminished significantly (P<.0001) after LASIK with increasing interocular differences in corneal and eye aberrations. Binocular visual deterioration was greater than monocular deterioration for contrast sensitivity function and disturbance index.

CONCLUSIONS

Binocular function deteriorates more than monocular function after LASIK. This deterioration increases as the interocular differences in aberrations and corneal shape increase. Improvements in ablation algorithms should minimize these interocular differences.

Measurement of Contrast Sensitivity and Glare Under Mesopic and Photopic Conditions Following Wavefront-guided and Conventional LASIK Surgery

PURPOSE

To compare contrast and glare vision in a prospective study of eyes treated using conventional and wavefront-guided LASIK surgery. The reproducibility of a glaremeter device used to quantitatively measure glare and halo was also determined.

METHODS

Ninety-two eyes of 46 patients underwent conventional LASIK surgery and 104 eyes of 52 patients underwent wavefront-guided LASIK surgery. Visual acuity, glare disability measured using a glaremeter, and contrast sensitivity assessed using a Pelli-Robson chart were measured monthly for 6 months postoperatively. Glaremeter testing was performed under both mesopic (5.4 +/- 0.4 cd/m2) and photopic (78.3 +/- 4.4 cd/m2) conditions. To evaluate the reproducibility of the glaremeter, 36 eyes of 18 nonoperated myopic patients were tested.

RESULTS

The coefficient of variation and the reliability coefficient for the glare test were 13.6% and 95.2%, respectively. The glaremeter showed that glare disability under mesopic conditions differed between conventional and wavefront-guided LASIK eyes over 6-month follow-up (907.5 +/- 491.5 vs 986.1 +/- 448.0 pixels preoperatively and 1717.1 +/- 521.2 vs 1407.8 +/- 411.3 pixels at 6 months, P<.0001). At 6 months, contrast sensitivity log values were 1.62 +/- 0.31 and 1.78 +/- 0.34 for conventional and wavefront-guided LASIK eyes, respectively (P=.010). The visual complaint score was lower in the wavefront-guided LASIK group (P=.0116).

CONCLUSIONS

Compared to conventional ablation, wavefront-guided ablation provided superior outcomes in terms of postoperative glare under mesopic conditions, subjective complaints, and contrast sensitivity. In addition, it appears the glaremeter can be used for clinical quantitative evaluation of glare and halo.

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.

Mitomycin: clinical applications in ophthalmic practice

Mitomycin (mitomycin C; MMC) is an antibiotic isolated from Streptomyces caespitosus. The drug is a bioreductive alkylating agent that undergoes metabolic reductive activation, and has various oxygen tension-dependent cytotoxic effects on cells, including the cross-linking of DNA. It is widely used systemically for the treatment of malignancies, and has gained popularity as topical adjunctive therapy in ocular and adnexal surgery over the past 2 decades. In ophthalmic medicine, it is principally used to inhibit the wound healing response and reduce scarring of surgically fashioned ostia. Hence, it has been used as adjunctive therapy in various ocular surgeries, such as glaucoma filtering surgeries, dacryocystorhinostomy, corneal refractive surgery and surgeries for ocular cicatrisation. In addition, it has been used as an adjunct in the surgical management of pterygia, ocular surface squamous neoplasia, primary acquired melanosis with atypia and conjunctival melanoma. In many of these surgeries and ophthalmic pathologies, MMC showed a significant beneficial effect.

Measuring contrast sensitivity under different lighting conditions: comparison of three tests

PURPOSE

The purpose of this study was to evaluate three psychophysical tests for the measurement of contrast sensitivity (CS) and disability glare (DG) at different luminance levels.

METHODS

In 60 eyes of 60 individuals (group 1: 20 healthy eyes of young individuals; group 2: 20 healthy eyes of elderly subjects; group 3: 20 eyes with nuclear cataract), CS with best correction was measured twice with the Frankfurt-Freiburg Contrast and Acuity Test System (FF-CATS) and the Functional Acuity Contrast Test (FACT, 1.5 cycles per degree [cpd]) at 167 cd/m2 and 0.167 cd/m2, and with the Pelli-Robson Chart (PRC) at 100 cd/m2 with and without glare. Repeatability of test and retest, and discriminative ability between the different subgroups, were assessed for CS values.

RESULTS

Maximum CS values varied across tests. In all groups, highest CS values were obtained with the photopic FF-CATS. For FACT scores at 1.5 cpd, there was a ceiling effect for young subjects. CS scores obtained with the PRC were the lowest. The PRC had the best test-retest repeatability of all tests. Under mesopic conditions with glare, reliability was generally lower; the FF-CATS had the highest repeatability of the mesopic tests. The FF-CATS discriminated best between the different groups for all conditions.

CONCLUSIONS

There are large discrepancies in the test results between CS testing methods, especially under different lighting conditions. Results from different CS tests are not interchangeable.

Improved contrast sensitivity and visual acuity after wavefront-guided laser in situ keratomileusis: in-depth statistical analysis

PURPOSE

To evaluate changes in contrast sensitivity and visual acuity following wavefront-guided laser in situ keratomileusis (LASIK) procedures with the Visx CustomVue system.

SETTING

Six clinical sites that participated in an Investigational Device Exemption clinical study.

METHODS

Two hundred seventy-four myopic astigmatic eyes (spherical equivalent range -0.63 to -6.00 diopters) completed 6 months of follow-up examinations. Wavefront-guided procedures using the WaveScan aberrometer and Star S4 excimer laser system with variable spot scanning were performed at 6 clinical locations. Visual acuity and contrast sensitivity under photopic, mesopic, and mesopic-with-glare lighting conditions were tested preoperatively and over a 6-month follow-up period. This study was a retrospective analysis of contrast sensitivity data with controls for the effects of retinal magnification, mesopic pupil size, and the influence of prior soft contact lens wear on visual outcome.

RESULTS

Patients experienced statistically significant improvements in contrast sensitivity at all spatial frequencies and under all lighting conditions (P<.05, Student t test). Contrast sensitivity under mesopic conditions with glare improved in 40% of patients. There was more improvement at higher (12 cycles per degree [cpd], 18 cpd) than lower (3 cpd) spatial frequencies. No correlation was found between mesopic pupil size and contrast sensitivity. Results stratified by spectacle or soft contact lens wear were similar. Soft contact lens wearers had slightly higher disability glare scores than spectacle wearers.

CONCLUSIONS

A significant number of patients experienced improved corneal optical quality after wavefront-guided LASIK. The contrast sensitivity in most patients was unchanged. Contrast sensitivity improved in a significant number of patients. There was no correlation between mesopic pupil size and mesopic or mesopic-with-glare contrast performance. Spectacle wearers improved more than soft contact lens wearers.