Wavefront- and topography-guided ablation in myopic eyes using Zyoptix

Simultaneous Topography-guided Custom Ablation With Corneal Cross-linking for Keratoconus: 10-Year Prospective Outcomes

PURPOSE

To assess 10-year visual and tomographic outcomes of topography-guided custom ablation (T-CAT) with corneal cross-linking (CXL) in eyes with keratoconus.

METHODS

T-CAT with CXL was performed in 600 eyes (522 patients). Based on the T-CAT ablation plan, the theoretical maximum ablation depth was 50 µm after epithelium removal. After ablation, accelerated corneal cross-linking (CXL) was performed in the central 8-mm zone (9 mW/cm2 for 10 minutes in "epi-off" mode). The visual acuity and tomography were assessed.

RESULTS

There was significant improvement in uncorrected (P = .001) and corrected (P = .001) distance visual acuity after the procedure. Keratometry, root mean square lower order aberrations and higher order aberrations, defocus, coma 90°, and spherical aberration reduced significantly after surgery at 10 years of follow-up (P < .005). All Pentacam (Oculus Optikgerate GmbH) tomographic variables showed significant changes indicating regularization after T-CAT (P < .005). Flattening of greater than 5.00 diopters in maximum keratometry was noted in 6 eyes (1%). Two of 600 eyes progressed postoperatively and required repeat CXL.

CONCLUSIONS

T-CAT plus CXL is a safe and effective technique even in the long term for regularizing the anterior corneal surface with significant visual improvement and reduction in higher order corneal aberrations. [J Refract Surg. 2023;39(11):759-766.].

Outcomes of topography-guided PRK/CXL in keratoconus using the NIDEK CXIII system-"Bharat Protocol" (Pilot study)

Purpose

Outcome of topography-guided excimer laser ablation in conjunction with accelerated, high-fluence cross-linking in corneal ecstatic disease using the NIDEK CXIII equipped with CATz algorithm from the FinalFit software-"Bharat Protocol."

Methods

Retrospective case record review of 30 eyes of 17 patients of stage 1-3 keratoconus who underwent the procedure was performed. Data collected were for visual acuity, distortion-induced eye pain, and keratometry. Pachymetry, lower order and higher order aberrations, spherical aberrations, and topographic cylinder were documented from by Scheimpflug imaging (Pentacam 70700: Oculus, Wetzlar, Germany).

Results

At a minimum follow-up of 6 months (range 6.2-13 months), there was significant improvement in UCVA (P < 0.00001), BCVA (P = 0.0061), decrease in Kmax (P = 0.0349), Ksteep (P < 0.0411), Kflat (P = 0.0099), and pachymetry (P = 0.0001). Significant improvement was also seen in distortion-induced eye pain (27/30 to 2/30; P < 0.00001). A more than two-line improvement in UCVA and BCVA was seen in 23/30 and 17/30 cases, respectively. Ectasia was stabilized in all cases at the last follow-up, and no complications were seen.

Conclusions

The "Bharat" Protocol to arrest keratectasia progression and improve corneal regularity is a safe and efficacious alternative as a keratoconus management option. This is the first such study on Nidek Platform for the same.

Topography-guided treatment in regular and irregular corneas

Over the last decade, refractive surgery has been revolutionized by advancements in ablation profiles, available for the treatment of both regular and irregular corneas. Advances in corneal imaging have helped highlight the presence of higher-order aberrations, the correction of which could result in a better quality of vision. Topographic measurements being static are more repeatable and pupil independent and therefore provide the ideal platform for correction of both lower and higher-order aberrations and could result in improved visual quality even in patients with seemingly regular corneas. The combination of topography-guided treatment with collagen cross-linking has further increased the scope of treating irregular corneas like keratoconus, post-laser in-situ keratomileusis ectasia, and pellucid marginal degeneration. This review delves into the current literature and guidelines available for the topographic treatment of regular and irregular corneas.

Correction of Myopic Astigmatism with Topography-Guided Laser In Situ Keratomileusis (TOPOLINK)

We aim to assess the feasibility of topography-guided laser in situ keratomileusis (TOPOLINK) for correcting pre-existing and surgical-induced astigmatism. A retrospective, single center cohort study was conducted. Patients with pre-existing irregular myopic astigmatism were recruited into the primary group and those with irregular myopic astigmatism following laser in situ keratomileusis (LASIK) were recruited into the enhancement group. The changes in uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), maximum astigmatism, spherical equivalent (SE) and patient satisfaction were recorded. The Chi-square test, Mann-Whitney U test and Generalized Linear Mixed Model were utilized for the analysis in the current study. A total of 18 eyes were studied in the primary group and 14 eyes were examined in the enhancement group. One year postoperatively, the UCVA, BCVA, maximum astigmatism and SE improved significantly in both the primary and the enhancement groups (all p < 0.05). The UCVA (p = 0.046) and SE (p = 0.003) were worse in the primary group preoperatively but became similar in both groups postoperatively, while the BCVA and maximum astigmatism remained identical between groups throughout the study period (all p < 0.05). In addition, the rate of high and moderate satisfaction reached 90.0% in the primary and the enhancement groups, without significant differences (p = 0.871). In conclusion, the TOPOLINK showed high predictability and will contribute to similar outcomes between primary and postoperative irregular myopic astigmatism concerning visual acuity, refractive status and subject satisfaction.

Outcomes of topography-guided versus wavefront-optimized laser in situ keratomileusis for myopia in virgin eyes

PURPOSE

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

SETTING

Advanced Eye Centre, Post Graduate Institute of Medical Education and Research, Chandigarh, India.

DESIGN

Prospective contralateral-eye case study.

METHODS

Patients had topography-guided LASIK in 1 eye and wavefront-optimized LASIK in the contralateral eye using the Customized Refractive Surgery Master software and Mel 80 excimer laser. Refractive (residual manifest refraction spherical equivalent [MRSE], higher-order aberrations [HOAs]), and visual (uncorrected distance visual acuity [UDVA] and photopic and mesopic contrast sensitivity) outcomes were prospectively analyzed 6 months postoperatively.

RESULTS

The study comprised 35 patients. The UDVA was 0.0 logMAR or better and the postoperative residual MRSE was ±0.50 diopter in 94.29% of eyes in the topography-guided group and 85.71% of eyes in the wavefront-optimized group (P = .09). More eyes in the topography-guided group than in the wavefront-optimized group had a UDVA of -0.1 logMAR or better (P = .04). Topography-guided LASIK was associated with less deterioration of mesopic contrast sensitivity at higher spatial frequencies (12 cycles per degree [cpd] and 18 cpd) and lower amounts of induced coma (P = .04) and spherical aberration (P = .04). Less stromal tissue was ablated in the topography-guided group (mean 61.57 μm ± 16.23 [SD]) than in the wavefront-optimized group (mean 79.71 ± 14.81 μm) (P < .001).

CONCLUSION

Although topography-guided LASIK and wavefront-optimized LASIK gave excellent results, topography-guided LASIK was associated with better contrast sensitivity, lower induction of HOAs, and a smaller amount of tissue ablation.

FINANCIAL DISCLOSURE

None of the authors has a financial or proprietary interest in any material or method mentioned.

Simultaneous versus Sequential Accelerated Corneal Collagen Cross-Linking and Wave Front Guided PRK for Treatment of Keratoconus: Objective and Subjective Evaluation

Aim. To compare objective and subjective outcome after simultaneous wave front guided (WFG) PRK and accelerated corneal cross-linking (CXL) in patients with progressive keratoconus versus sequential WFG PRK 6 months after CXL. Methods. 62 eyes with progressive keratoconus were divided into two groups; the first including 30 eyes underwent simultaneous WFG PRK with accelerated CXL. The second including 32 eyes underwent subsequent WFG PRK performed 6 months later after accelerated CXL. Visual, refractive, topographic, and aberrometric data were determined preoperatively and during 1-year follow-up period and the results compared in between the 2 studied groups. Results. All evaluated visual, refractive, and aberrometric parameters demonstrated highly significant improvement in both studied groups (all P < 0.001). A significant improvement was observed in keratometric and Q values. The improvement in all parameters was stable till the end of follow-up. Likewise, no significant difference was determined in between the 2 groups in any of recorded parameters. Subjective data revealed similarly significant improvement in both groups. Conclusions. WFG PRK and accelerated CXL is an effective and safe option to improve the vision in mild to moderate keratoconus. In one-year follow-up, there is no statistically significant difference between the simultaneous and sequential procedure.

Cone location-dependent outcomes after combined topography-guided photorefractive keratectomy and collagen cross-linking

PURPOSE

To evaluate the effect of keratoconus cone location on the change in refractive outcomes, corneal aberrations, and biomechanics after combined topography-guided photorefractive keratectomy (PRK) and collagen cross-linking (CXL).

DESIGN

Prospective, comparative case series.

METHODS

Topography-guided PRK was performed followed by accelerated CXL using riboflavin A and enhanced-intensity (30 mW/cm(2)) ultraviolet light. Outcome parameters including uncorrected distance visual acuity (UDVA) and best-corrected distance visual acuity (BDVA), corneal tomography and biomechanics (corneal hysteresis [CH] and corneal resistance factor [CRF]), and corneal wavefront aberrations were assessed before and a year after the procedure. Eyes were subdivided into 2 groups preoperatively for statistical analysis: Group 1, cone located within the central 2-mm zone; and Group 2, cone located outside the central 2-mm zone.

RESULTS

UDVA, BDVA, sphere, cylinder, and simulated keratometry improved after treatment in both groups (P < .05). However, BDVA improved more in Group 1 than in Group 2 (P = .04) and the other variables were not affected by cone location. A few corneal wavefront Zernike aberrations changed after treatment (P < .05) but none were affected by cone location (P > .05). CH and CRF increased after treatment in both groups (P > .05). Interestingly, the increases in CH and CRF were greater in Group 2 than in Group 1 (P > .05).

CONCLUSIONS

Cone location appeared to impact only visual acuity and biomechanics after the combined procedure. The greater increase in CH and CRF in Group 2 may indicate differences in the ablation profile and variability in CXL outcomes and requires further study.

Topography-guided custom ablation treatment for treatment of keratoconus

Keratoconus is a progressive ectatic disorder of the cornea which often presents with fluctuating refraction and high irregular astigmatism. Correcting the vision of these patients is often a challenge because glasses are unable to correct the irregular astigmatism and regular contact lenses may not fit them very well. Topography-guided custom ablation treatment (T-CAT) is a procedure of limited ablation of the cornea using excimer laser with the aim of regularizing the cornea, improving the quality of vision and possibly contact lens fit. The aim of the procedure is not to give a complete refractive correction. It has been tried with a lot of success by various groups of refractive surgeons around the world but a meticulous and methodical planning of the procedure is essential to ensure optimum results. In this paper, we attempt to elucidate the planning for a T-CAT procedure for various types of cones and asphericities.

Early clinical outcomes of wavefront-guided myopic LASIK treatments using a new-generation hartmann-shack aberrometer

PURPOSE

To provide an initial retrospective evaluation of early postoperative outcomes after wavefront-guided myopic LASIK using a new-generation Hartmann-Shack wavefront sensor.

METHODS

A noncomparative, retrospective study of 243 eyes of 126 patients that underwent primary wavefront-guided LASIK, using wavefront data obtained with a new Hartmann-Shack aberrometer (iDesign Advanced WaveScan aberrometer; Abbott Medical Optics, Inc., Santa Ana, CA). Visual acuity, refraction, and patient satisfaction were evaluated 1 month after surgery.

RESULTS

The manifest spherical equivalent was reduced from -3.28 ± 1.79 diopters (D) (range: -9.88 to -0.38 D) before surgery to -0.03 ± 0.29 D (range: -1.00 to +1.25 D) 1 month after surgery. The manifest spherical equivalent was within 0.50 and 1.00 D of target in 93.0% and 99.6% of eyes, respectively. Manifest astigmatism preoperatively (-0.72 ± 0.67 [range: 0.0 to -5.00 D]) was reduced to -0.14 ± 0.20 (range: 0.0 to -1.00 D) at 1 month and the vector-derived correction ratio (surgically induced refractive change/intended refractive correction) was 1.02 ± 0.30. Uncorrected distance visual acuity of 20/16, 20/20, and 20/25 or better was achieved in 79.0%, 93.4%, and 96.7% of eyes, respectively. No eyes lost two or more lines of corrected distance visual acuity, whereas a gain of one or more lines was observed in 14.0%. Most patients (98.5%) reported that they were satisfied with the outcome of their procedure.

CONCLUSIONS

Wavefront-guided LASIK using the new aberrometer in this retrospective evaluation was effective, safe, and predictable in the early postoperative time period for the correction of myopia with high patient satisfaction.

Four-year visual, refractive, and contrast sensitivity outcomes after wavefront-guided myopic LASIK using an advanced excimer laser platform

PURPOSE

To evaluate the 4-year visual, refractive, and contrast sensitivity outcomes of wavefront-guided LASIK for the correction of low to moderate myopia using the VISX CustomVue technology (Abbott Medical Optics, Inc., Santa Ana, CA).

METHODS

This was a prospective study including 255 consecutive eyes of 145 patients (age range: 19 to 55 years) with low to moderate myopia (mean spherical equivalent: -3.36 ± 1.71 diopters [D]) undergoing laser refractive surgery. Wavefront-guided LASIK was performed in all eyes using the VISX STAR S4 IR excimer laser platform and the CustomVue procedure for the ablation profile design. Visual, refractive, and contrast sensitivity changes were evaluated during a 4-year follow-up period.

RESULTS

Postoperative logMAR uncorrected distance visual acuity was 0.1 or better (20/25 Snellen) in 98.0% and 100% of eyes at 1 and 4 years, respectively. At 4 years postoperatively, mean spherical equivalent was reduced significantly to a mean value of -0.22 ± 0.28 D (P < .01), with 97.3% of eyes with a spherical equivalent within ±0.50 D. The astigmatic power vector component J0 of manifest refraction was also reduced significantly (P < .01). Postoperative logMAR corrected distance visual acuity was 0.0 or better (20/20 Snellen) in 96.1% and 98.8% of eyes at 1 and 4 years, respectively. Improvement in contrast sensitivity was observed in some spatial frequencies between 1 and 4 years postoperatively. No significant correlations were found between 4-year contrast sensitivity and corrected distance visual acuity (0.024 ≤ r ≤ -0.120, P ≥ .06).

CONCLUSION

Wavefront-guided LASIK using the VISX CustomVue technology provides an effective and predictable correction of low to moderate myopia in the long term, preserving the patient's visual acuity and quality.

Clinical results of topography-based customized ablations for myopia and myopic astigmatism

PURPOSE

To evaluate clinical outcomes after primary treatments for myopia and myopic astigmatism with topography-based ablation profiles on the Allegretto Wave Eye-Q platform (Alcon Laboratories Inc).

METHODS

Records of patients who underwent topography-guided, Q-adjusted LASIK were retrieved and analyzed. Patients with mean refractive spherical equivalent up to -16.00 diopters (D) and cylindrical errors up to 6.00 D were included (2051 eyes). Refractive outcomes and visual acuities were analyzed preoperatively and 3 months postoperatively.

RESULTS

Manifest spherical refractive error decreased from -5.05 +/- 2.33 to +0.04 +/- 0.35 D. Manifest cylindrical refractive error decreased from 0.83 +/- 0.75 to 0.23 +/- 0.22 D. At 3 months postoperatively, 86.1% (1766 eyes) had a spherical equivalent refraction within +/- 0.50 D of targeted refraction. The number of eyes with uncorrected distance visual acuity of 20/16 and 20/20 was 851 (41.5%) and 1495 (72.9%), respectively. At 3 months, 0.10% (2 eyes) lost more than 2 lines of corrected distance visual acuity and a loss of 2 lines occurred in 0.24% (5 eyes). All patients who lost lines of visual acuity were found to have corneal erosions related to dryness and recovered vision on further follow-up.

CONCLUSIONS

The results of this retrospective study demonstrate refractive predictability, efficacy, and safety comparable to other treatment modalities such as wavefront-optimized and wavefront-guided treatments. Results are also similar to those reported with other topography-guided systems.

Visual outcomes of topography-guided excimer laser surgery for treatment of patients with irregular astigmatism

The aim of this study was to evaluate the efficacy, safety, and predictability of topography-guided treatments to enhance refractive status following other corneal surgical procedures. In a prospective case series study, 28 consecutive eyes of 26 patients with irregular astigmatism after radial keratotomy, corneal transplant, small hyperopic and myopic excimer laser optical zones, and corneal scars were operated. Laser-assisted in situ keratomileusis (LASIK) (n = 8) and photorefractive keratectomy (PRK) (n = 20) were performed using the ALLEGRETTO WAVE excimer laser and topography-guided customized ablation treatment software. Preoperative and postoperative uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), manifest and cycloplegic refraction, and corneal topography with asphericity were analyzed in 12 months follow-up. Uncorrected visual acuity (UCVA) changed from 0.2 ± 0.2 or (20/100 ± 20/100) to 0.51 ± 0.31 or (20/40 ± 20/60) in the LASIK group (P = 0.01) and from 0.34 ± 0.16 or (20/60 ± 20/120) to 0.5 ± 0.23 or (20/40 ± 20/80) in the PRK group (P = 0.01). Refractive cylinder decreased from -3.2 ± 0.84 diopters (D) to -2.06 ± 0.42 D in the LASIK group (P = 0.07) and from -2.25 ± 0.39 D to -1.5 ± 0.23 D in the PRK group (P = 0.008). Best corrected visual acuity did not change significantly in either group. Topography-guided treatment is effective in correcting the irregular astigmatism after refractive surgery. Topography-guided PRK can significantly reduce irregular astigmatism and increase the UCVA and BCVA.

Effect of pupil size on residual wavefront aberration with transition zone after customized laser refractive surgery

The analysis of the change in residual wavefront aberrations after laser refractive surgery is important for the development of visual correction technology. Based on the ablation profile for wavefront-guided refractive surgery including optical zone and transition zone, the effect of pupil size on residual wavefront aberrations was studied. The research revealed that the optical zone to pupil ratio had a significant influence on the residual wavefront aberrations. The residual spherical aberration and coma were obviously larger than other individual Zernike higher-order terms when pupil diameter was larger than the optical zone size, and they increased rapidly as the pupil size increased. In addition, when the ablation zone diameter was kept constant, the residual higher-order aberrations increased rapidly as the blend coefficient increased for a 6 mm or 7 mm pupil. Furthermore, the residual higher-order aberrations with treatment decentration were distinctly larger than those without decentration. In the achievement of the best postoperative visual performance, the design of ablation profile played a crucial role in decrease of the residual wavefront aberrations after refractive surgery, especially optical zone size and the ablation pattern of transition zone.

Visual outcome after correcting the refractive error of large pupil patients with wavefront-guided ablation

Purpose

To investigate the efficacy and predictability of wavefront-guided laser in situ keratomileusis (LASIK) treatments using the iris registration (IR) technology for the correction of refractive errors in patients with large pupils.

Setting

Horus Vision Correction Center, Alexandria, Egypt.

Methods

Prospective noncomparative study including a total of 52 eyes of 30 consecutive laser refractive correction candidates with large mesopic pupil diameters and myopia or myopic astigmatism. Wavefront-guided LASIK was performed in all cases using the VISX STAR S4 IR excimer laser platform. Visual, refractive, aberrometric and mesopic contrast sensitivity (CS) outcomes were evaluated during a 6-month follow-up.

Results

Mean mesopic pupil diameter ranged from 8.0 mm to 9.4 mm. A significant improvement in uncorrected distance visual acuity (UCDVA) (P < 0.01) was found postoperatively, which was consistent with a significant refractive correction (P < 0.01). No significant change was detected in corrected distance visual acuity (CDVA) (P = 0.11). Efficacy index (the ratio of postoperative UCDVA to preoperative CDVA) and safety index (the ratio of postoperative CDVA to preoperative CDVA) were calculated. Mean efficacy and safety indices were 1.06 ± 0.33 and 1.05 ± 0.18, respectively, and 92.31% of eyes had a postoperative spherical equivalent within ±0.50 diopters (D). Manifest refractive spherical equivalent improved significantly (P < 0.05) from a preoperative level of −3.1 ± 1.6 D (range −6.6 to 0 D) to −0.1 ± 0.2 D (range −1.3 to 0.1 D) at 6 months postoperative. No significant changes were found in mesopic CS (P ≥ 0.08), except CS for three cycles/degree, which improved significantly (P = 0.02). Magnitudes of primary coma and trefoil did not change significantly (P ≥ 0.34), with a small but statistically significant increase in primary spherical aberration.

Conclusion

Wavefront-guided LASIK provides an effective correction of low to moderate myopia or myopic astigmatism in large pupil patients without deterioration of visual quality.

Precision of a commercial hartmann-shack aberrometer: limits of total wavefront laser vision correction

PURPOSE

To assess the intrasession and intersession precision of higher-order aberrations (HOAs) measured using a commercial Hartmann-Shack wavefront sensor (Zywave; Bausch & Lomb) in refractive surgery candidates.

DESIGN

Prospective, experimental study of a device.

METHODS

To analyze intrasession repeatability, 1 experienced examiner measured 30 healthy eyes 5 times successively. To study intersession reproducibility, the same clinician obtained measurements from another 30 eyes in 2 consecutive sessions at the same time of day 1 week apart.

RESULTS

For intrasession repeatability, excellent intraclass correlation coefficients (ICCs) were obtained for total ocular aberrations, total HOAs, and second-order terms (ICC, > 0.94). The ICCs for third-order terms also were high (ICCs, > 0.87); however, fourth-order ICCs varied from 0.71 to 0.90 (Z(4)(0) = 0.90); and fifth-order ICCs were less than 0.85. For intersession reproducibility, only total ocular aberrations, total ocular HOAs, second-order terms, Z(4)(0), Z(3)(1), and Z(3-)(3) had ICCs of 0.90 or more. Bland-Altman analysis showed that the limits of agreement (were clinically too wide for most higher-order Zernike terms, especially for the third-order terms (> 0.21 μm).

CONCLUSIONS

Total ocular aberrations, total HOAs, and second-order terms can be measured reliably by Zywave aberrometry without anatomic recognition. Third-order terms and Z(4)(0) are repeatable, but not as reproducible between visits. Fourth-order terms, except for Z(4)(0), and fifth-order terms are not sufficiently reliable for clinical decision making or treatment. Because the variability of Zywave can be a major limitation of a truly successful wavefront-guided excimer laser procedure, surgeons should consider treating HOA magnitudes that are more than the intrasession repeatability values (2.77 × S(w)) as those presented in this study.

Prospective contralateral eye study to compare conventional and wavefront-guided laser in situ keratomileusis

PURPOSE

To compare outcomes of customized/wavefront guided with conventional ablation in myopic patients with or without astigmatism undergoing laser in situ keratomileusis.

METHODS

A prospective, comparative, contralateral eye study was performed. Sixty-eight eyes of 34 myopic patients with similar refractive error in both eyes were included. One eye was randomly selected to undergo conventional and the fellow eye customized ablation. Surgery was performed using the Technolas 217z laser (Bausch & Lomb, Surrey, UK). Uncorrected visual acuity, manifest refractive spherical equivalent (MRSE), astigmatism, aberrometry and contrast sensitivity were recorded pre and 3 months postoperatively.

RESULTS

Mean MRSE treated in the conventional and customized groups were 3.77 ± 1.61 dioptres and -3.83 ± 1.59 dioptres respectively. Three months postoperatively there was no significant difference between the groups in mean MRSE (p = 0.99) or cylinder (p = 0.56). The factor increase in postoperative total higher order aberrations (HOAs) was less in the customized (1.32) compared with the conventional (1.54) treatment group but did not reach statistical significance (p = 0.08). Scotopic contrast sensitivity decreased significantly postoperatively in the conventional but not in the customized treatment group.

CONCLUSION

Visual acuity and refractive error outcomes were similar in both treatment group and no patient preference was observed. Customized ablation was associated with a smaller but not statistically significant postoperative increase in HOAs, better preservation of scotopic contrast sensitivity, quicker treatment time and removal of less corneal tissue.

Influence of mydriatic eye drops on wavefront sensing with the Zywave aberrometer

PURPOSE

To investigate a potential influence of mydriatic eye drops on wavefront sensing with the Zywave aberrometer (Technolas Perfect Vision) in terms of predicted phoropter refraction (PPR) and higher order aberrations (HOA).

METHODS

In this prospective study, 200 myopic eyes were measured in miosis and pharmacologically induced mydriasis with an aberrometer and automated refraction. One hundred eyes were dilated with tropicamide 0.5%+phenylephrine 2.5% eye drops (tropicamide/phenylephrine group), and the remaining 100 eyes with tropicamide 0.5% (tropicamide only group). The PPR values for a pupil diameter of 3.5 mm in miosis and mydriasis, respectively, were compared and correlated to the corresponding values of automated refraction. Changes in HOAs up to the 4th order were recorded.

RESULTS

Predicted phoropter refraction values obtained in mydriasis were less myopic than in miosis. The spherical equivalent refraction of PPR differed by an average of 0.36 ± 0.36 diopters (D) in the tropicamide/phenylephrine group. In the tropicamide only group, the difference was 0.24 ± 0.43 D. Sphere of PPR differed by an average of 0.33 ± 0.36 D in the tropicamide/phenylephrine group and by an average of 0.24 ± 0.35 D in the tropicamide only group. Patient age had no major influence on the level of difference. Automated refraction yielded a smaller difference in spherical equivalent refraction. Changes in HOA root-mean-square were statistically significant.

CONCLUSIONS

The cycloplegic effect of mydriatic eye drops should be taken into account when interpreting aberration measurements and planning a wavefront-guided ablation. Ideally, the use of mydriatic eye drops should be avoided to minimize refractive surprises.

Topography-guided treatment of decentered laser ablation using LaserSight's excimer laser

PURPOSE

To assess the efficacy of topography-guided laser ablation for correction of previously decentered laser ablation using LaserSight's excimer laser.

METHODS

Re-treatment was performed to correct decentered ablation using LaserSight's excimer laser for 18 patients who previously underwent LASIK surgery for myopia correction in both eyes. For each patient, only the decentered eye was re-treated while the other asymptomatic eye forms a control group for this study. Measurements were conducted on ablation center, best spectacle-corrected visual acuity (BSCVA), contrast sensitivity and corneal aberrations pre- and post-operatively.

RESULTS

For the retreated 18 eyes, the mean decentration was significantly reduced from 1.32+/-0.28mm to 0.61+/-0.23mm post-operatively (t=16.24, p<0.001), and with a significant improvement in mean BSCVA from 0.08+/-0.09 logMAR to 0.01+/-0.11 logMAR (t=4.58, p<0.001). The post-operative contrast sensitivity at the spatial frequencies (SF) of 1.00 and 0.70 was significantly improved (p<0.05 for both SFs). Corneal higher-order aberrations (HOAs), including the coma-like aberrations and spherical aberration, were decreased. In comparing the measurements for the retreated group to those for the control group, no significant differencewas found either in decentration or in BSCVA, but the contrast sensitivity at 0.70 was lower and the level of corneal aberrations was higher.

CONCLUSIONS

Topography-guided ablation with LaserSight excimer laser is effective to correct decentered ablation. However, the re-treated eye is still inferior to the eye with originally centered ablation in corneal optical quality or visual performance.

Advances in technologies for laser-assisted in situ keratomileusis (LASIK) surgery

Laser-assisted in situ keratomileusis (LASIK) has become the most widely used form of refractive surgery today. The objective of this surgical technique is to modify the anterior corneal shape by ablating tissue from the stroma by means of the excimer laser after creating a hinged corneal flap. This way, we are able to change the refractive status of the patient, providing better unaided vision. Continuous improvements in the original technique have made the surgical procedure safer, more accurate and repeatable. These progressions are due to the development of novel technologies that are the responsible for new surgical instrumentation, which makes the surgical procedure easier for the surgeon, and better excimer laser ablation algorithms, which increase the optical quality of the ablation and thus the safety of the vision correction procedure. This article aims to describe the more relevant advances in LASIK that have played an important role in the spread and popularity of this technique.

Wavefront-guided laser in situ keratomileusis in the treatment of high myopia by using the CustomVue wavefront platform

PURPOSE

To assess the efficacy, predictability, and safety of wavefront-guided laser in situ keratomileusis (LASIK) in the treatment of high myopia by using the Visx S4 CustomVue wavefront platform.

METHODS

A retrospective analysis of consecutive cases of eyes with high myopia (manifest refraction spherical equivalent >or= -6.00 D) that underwent non-physician-adjusted wavefront-guided LASIK by using the Visx S4 CustomVue wavefront platform. Forty-three eyes of 29 patients were included. Preoperative best spectacle-corrected visual acuity (BSCVA), manifest refraction, WaveScan refraction, postoperative uncorrected visual acuity (UCVA) and BSCVA, and manifest refraction were determined. The clinical outcomes were evaluated on the basis of standard formats and criteria. Data at 3 months postoperatively are presented.

RESULTS

Preoperatively, we found mean sphere was -6.89 +/- 1.08 D, mean cylinder was -0.97 +/- 0.75 D, and mean spherical equivalent (SE) was -7.38 +/- 1.20 D. Postoperatively, mean sphere was 0.02 +/- 0.40 D, mean cylinder was -0.40 +/- 0.40 D, and mean SE was -0.18 +/- 0.43 D. UCVA was 20/15 or better in 27.9% and cumulatively 20/20 or better in 58% of eyes. All eyes treated had at least 20/50 UCVA. Efficacy index was 0.94. Eighty-two percent of eyes were within 0.50 D and 97.6% were within 1.00 D of emmetropia at the 3-month follow-up visit. Ninety-one percent of eyes either maintained or gained 1 line of BSCVA. No eye lost >1 line of BSCVA. The safety index was 1.1.

CONCLUSIONS

The 3-month follow-up results of our study indicate that wavefront-guided LASIK by using the Visx S4 CustomVue wavefront platform is an effective, predictable, and safe treatment of high myopia.

Patient satisfaction and visual symptoms after wavefront-guided and wavefront-optimized LASIK with the WaveLight platform

PURPOSE

To investigate patient satisfaction and visual symptoms after wavefront-guided LASIK.

METHODS

A prospective, randomized, double-masked, controlled study comprised 200 eyes of 100 young patients who underwent LASIK for myopia and astigmatism. Patients were randomly divided into two different treatment groups: standard ablation using wavefront-optimized profiles (wavefront-optimized group) and aberration customized aspheric treatment ablation (customized group) using the WaveLight ALLEGRETTO platform. Patients were asked to complete questionnaires regarding reasons for surgery, satisfaction, and visual symptoms. Patients were followed for 6 months.

RESULTS

The most frequent motivating factor for surgery was to improve uncorrected visual acuity (UCVA) in the wavefront-optimized and customized groups (both 100%), followed by freedom from spectacles (86.9% vs 96.3%). At 6 months postoperatively, over 95% of patients in both groups reported their UCVA was as good as anticipated and they were satisfied with the surgery and would recommend the operation to a friend or family member. Satisfaction was not correlated with age, attempted refractive error, residual refractive error, postoperative UCVA, or root-mean-square higher order aberration. The rate of postoperative overall visual symptoms was reduced and the mean analog scores of the symptoms in both groups did not change significantly postoperatively (P > .05). The rate of visual symptoms such as glare (8.7% vs 7.4%), halo (0% vs 7.4%), and night driving difficulty (8.7% vs 3.7%) decreased after LASIK at 6 months postoperatively in the wavefront-optimized and customized groups, respectively.

CONCLUSIONS

Patient satisfaction was achieved in young myopic patients who underwent wavefront-guided and standard ("wavefront-optimized") LASIK. The rate of visual symptoms such as glare, halo, and night driving difficulty decreased postoperatively after both treatment protocols.

Topographic Customized Photorefractive Keratectomy for Regular and Irregular Astigmatism After Penetrating Keratoplasty Using the LIGI CIPTA/LaserSight Platform

PURPOSE

To evaluate the use of a software ablation program (Corneal Interactive Programmed Topographic Ablation [CIPTA]) that provides customized photorefractive keratectomy (PRK) to correct astigmatism after keratoplasty.

METHODS

In this prospective, noncomparative, consecutive case series, 44 eyes underwent CIPTA for correction of astigmatism after penetrating keratoplasty. Eighteen eyes were treated for regular astigmatism and 26 eyes were treated for irregular astigmatism after penetrating keratoplasty. Orbscan II topography (Bausch & Lomb) and a flying-spot laser (LaserScan 2000; LaserSight) were used. Epithelial debridement with alcohol was performed before PRK in 16 eyes and transepithelial PRK was performed in 28 eyes. Mean target-induced astigmatism was 8.19 +/- 2.68 diopters (D) and 7.68 +/- 4.50 D in the regular and irregular astigmatism groups, respectively.

RESULTS

Mean follow-up was 25.4 +/- 13 months. At last postoperative follow-up, 13 (72.2%) and 18 (69.2%) eyes in the regular and irregular astigmatism groups, respectively, had uncorrected visual acuity (UCVA) better than 20/40. Four (22.2%) and 8 (30.7%) eyes in the regular and irregular astigmatism groups, respectively, had UCVA of 20/20. Fourteen (77.7%) and 18 (69.2%) eyes in the regular and irregular astigmatism groups, respectively, were within 1.00 D of attempted correction in spherical equivalent manifest refraction. No eye lost Snellen lines of best spectacle-corrected visual acuity. Mean surgically induced astigmatism was 7.66 +/- 2.70 D and 6.99 +/- 3.80 D for the regular and irregular astigmatism groups, respectively. Index of success of astigmatic correction was 0.138 and 0.137 for the regular and irregular astigmatism groups, respectively. Haze developed in three eyes.

CONCLUSIONS

Topography-driven PRK using CIPTA software is a suitable solution for correcting regular and irregular astigmatism after penetrating keratoplasty.

Effect of Hormone Replacement Therapy in Women on Ocular Refractive Status and Aberrations

PURPOSE

To evaluate the effects of hormone replacement therapy (HRT) on refractive status, corneal topography, and aberrations of the eye in postmenopausal women.

METHODS

Thirty-six healthy postmenopausal women (72 eyes) were included in the study. All patients received HRT that consisted of 0.625 mg/day conjugated estrogen and 5 mg/day medroxyprogesterone acetate in a continuous combined regimen. Schirmer II test and tear film break-up time (BUT) were performed on all patients at the time of enrollment and 6 months after initiation of HRT. Refractive status, corneal topography, and wavefront aberrations were evaluated with the NIDEK Optical Path Difference-Scan before and 6 months after HRT was initiated.

RESULTS

Mean patient age was 50.8 +/- 2.6 years (range: 47 to 57 years). The mean duration of menopause was 2.7 +/- 0.8 years (range: 1.4 to 3.5 years). The Schirmer II test and tear film BUT measurements were significantly lower after HRT (P < .05). Before HRT, the mean spherical equivalent refraction was -0.19 +/- 1.79 diopters (D) (range: -4.38 to +3.00 D). After HRT, the mean spherical equivalent refraction was -0.22 +/- 1.81 D (range: -4.63 to +/- 2.63 D). No significant differences were noted between refractive status, corneal topography, and wavefront aberrations of eyes of patients before and 6 months after HRT (P > .05).

CONCLUSIONS

Hormone replacement therapy in postmenopausal women does not significantly affect refractive status, corneal topography, and wavefront aberrations of the eye at 6-month follow-up.

Wavefront-guided LASIK for Myopia With the Technolas 217z: Results at 3 Years

PURPOSE

To evaluate the clinical outcome of wavefront-guided LASIK in patients with low to high myopia.

METHODS

The study included 316 eyes of 158 patients; 172 eyes with low to moderate myopia (< or = 6.00 diopters [D]) and 144 eyes with high myopia (> or = 6.25 D). Preoperative wavefront analysis was performed with the Hartmann-Shack aberrometer, and LASIK was done with the Technolas 217z excimer laser. Follow-up was 36 months. Safety, efficacy, predictability, stability, and complications were compared between groups.

RESULTS

Mean preoperative spherical equivalent refraction (SE) was -6.50 +/- 7.72 D (range: -1.50 to -16.00 D) in the entire study group, -4.91 +/- 1.38 D in the low to moderate myopia group, and -9.41 +/- 2.51 D in the high myopia group. At 36 months, 222 (70%) eyes showed no change in best spectacle-corrected visual acuity and 67 (21%) eyes gained > or = 1 line. In the low to moderate myopia group, SE of +/- 0.50 D was achieved by 85% of eyes and +/- 1.00 D by 97%, and 65% and 80%, respectively, in the high myopia group. Undercorrection > 0.50 D was observed in 25% (36 eyes) of the high myopia group and 5% (8 eyes) of the low to moderate myopia group. All eyes showed significant reduction in spherical aberration (Z4,0) at 12 months postoperatively with no complications except diffuse lamellar keratitis in 2 eyes (1 eye in each group).

CONCLUSIONS

Wavefront-guided LASIK is an efficient refractive surgery technique for patients with low to moderate myopia. Higher degrees of myopia may be subject to under- and overcorrection.

Clinical Ocular Wavefront Analyzers

PURPOSE

To provide a summary of the methods used by clinical wavefront analyzers and their historical, current, and future applications.

METHODS

Review of the literature and authors' experience with the various devices.

RESULTS

A wide range of clinical wavefront aberrometers, which use different principles, are available to clinicians and researchers.

CONCLUSIONS

Applications of wavefront analyzers in vision sciences range from assessment of refractive error, refractive surgery planning, evaluation of outcomes, optimization of contact lenses and IOL designs, evaluation of pathology relating to optical performance of the eye, and evaluation of accommodation alterations.

Topography-guided Ablation for Treatment of Patients With Irregular Astigmatism

PURPOSE

To evaluate the customized aspheric treatment zone (CATz) topography-guided ablation for the correction of irregular astigmatism induced by initial corneal refractive surgery or corneal injury.

METHODS

CATz ablation was performed on 32 eyes of 28 patients. Each procedure was performed by photorefractive keratectomy (PRK) or LASIK using a NIDEK EC-5000 excimer laser. The eyes had decentered ablations, small optical zones, decreased best spectacle-corrected visual acuity (BSCVA), and asymmetrical astigmatism. Subjective symptoms, uncorrected visual acuity (UCVA), BSCVA, refraction, corneal topography, and higher order aberrations were measured. Mean follow-up was 161.9 +/- 129.9 days (range: 90 to 492 days).

RESULTS

Data obtained at final postoperative follow-up show that UCVA and BSCVA increased by > or = 2 lines after CATz ablation in 17 and 11 eyes and decreased in 4 and 2 eyes, respectively. Higher order aberrations were decreased in 16 eyes and increased in 1 eye. Topographical maps were improved with decreased surface regularity index (20 eyes) and surface asymmetry index (22 eyes). Seven eyes required further enhancement for residual refractive errors. Thirteen patients (15 eyes) claimed they were satisfied with the outcome, 6 patients (7 eyes) stated that the outcome was lower than expected, and 4 patients (4 eyes) stated they were dissatisfied.

CONCLUSIONS

CATz topographic ablation effectively improves the quality of vision and symptoms in the majority of patients with irregular corneal astigmatism from previous excimer laser refractive surgery. However, residual or induced refractive errors may need to be corrected with a second operation after CATz.

Comparison of higher-order aberrations after wavefront-guided laser in situ keratomileusis and laser-assisted subepithelial keratectomy

PURPOSE

To compare the higher-order aberrations (HOAs) in 70 eyes (38 patients) that had wavefront-guided laser in situ keratomileusis (LASIK) with those in 70 eyes (40 patients) that had wavefront-guided laser-assisted subepithelial keratectomy (LASEK) for the treatment of myopia.

SETTING

Department of Ophthalmology, Yonsei University College of Medicine, Myongdong Bal-geun sesang Eye Clinic, and Seran Eye Center, Seoul, Korea.

METHODS

In a prospective study, 140 consecutive eyes of 78 patients were treated with wavefront-guided LASIK or LASEK according to the patient's choice after each procedure had been thoroughly explained. The patients were followed for 6 months. Best corrected visual acuity (BCVA), uncorrected visual acuity (UCVA), manifest refraction, and wavefront aberrations were measured at baseline and 1, 3, and 6 months after surgery.

RESULTS

There were no significant differences in postoperative BCVA, UCVA, and manifest refraction between groups. The mean root-mean-square wavefront error of HOAs for a scotopic pupil in the wavefront-guided LASIK group was significantly smaller than that in the wavefront-guided LASEK group at 1 month. Analyzing individual Zernike coefficients, the spherical aberration and second coma were significantly smaller in the wavefront-guided LASIK group than in the wavefront-guided LASEK group at 1 month. This difference in HOAs between groups disappeared at 3 and 6 months.

CONCLUSIONS

The HOAs in the scotopic condition were not different between the wavefront-guided LASIK and LASEK groups beginning 3 months after surgery. However, the HOAs in the LASIK and LASEK groups had a different time course, especially in the case of spherical aberration. This finding suggests that postoperative changes in aberration contribute to the final outcome of wavefront-guided ablation.

Topography-guided Treatment of Irregular Astigmatism With the WaveLight Excimer Laser

PURPOSE

To evaluate the feasibility, safety, and predictability of correcting high irregular astigmatism in symptomatic eyes with the use of topography-guided photoablation.

METHODS

In a prospective, non-comparative case series, 16 consecutive symptomatic eyes of 11 patients with small hyperopic and myopic excimer laser optical zones, decentered and irregular ablation after corneal graft, and corneal scars were operated. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), manifest and cycloplegic refraction, and corneal topography, with asphericity and regularity, were analyzed. LASIK (n = 10) and photorefractive keratectomy (n = 6) were performed using the ALLEGRETTO WAVE excimer laser and T-CAT software (Topography-guided Customized Ablation Treatment; WaveLight Laser Technologie AG, Erlangen, Germany).

RESULTS

In the LASIK group, UCVA improved from 0.81 +/- 0.68 IogMAR (20/130) (range: 0.2 to 2.0) to 0.29 +/- 0.21 logMAR (20/39) (range: 0.1 to 0.7) at 6 months. In the PRK group, mean UCVA improved from 0.89 +/- 0.87 IogMAR (20/157) (range: 0.1 to 2.0) to 0.42 +/- 0.35 logMAR (20/53) (range: 0.1 to 1.0) at 6 months. Best spectacle-corrected visual acuity did not change significantly in either group. One PRK patient lost one line of BSCVA. Refractive cylinder for the LASIK group improved from -2.53 +/- 1.71 diopters (D) (range: -0.75 to -5.75 D) to -1.28 +/- 0.99 D (range: 0 to -2.50 D) at 6 months. Refractive cylinder in the PRK group improved from -2.21 +/- 2.11 D (range: -0.25 to -5.50 D) to -1.10 +/- 0.42 D (range: -0.50 to -1.50 D). Index of surface irregularity showed a decrease from 60 +/- 12 (range: 46 to 89) to 50 +/- 9 (range: 32 to 63) at 6 months in the LASIK group whereas no significant change was noted in the PRK group. Subjective symptoms, such as glare, halos, ghost images, starbursts, and monocular diplopia, were not present postoperatively.

CONCLUSIONS

Topography-guided LASIK and PRK resulted in a significant reduction of refractive cylinder and increase of UCVA, without a significant loss of BSCVA.

CustomVue laser in situ keratomileusis for myopia and myopic astigmatism using the Visx S4 excimer laser

PURPOSE

To evaluate the efficacy, predictability, and safety of custom laser in situ keratomileusis (LASIK) using the Visx wavefront platform CustomVue for the treatment of myopia and myopic astigmatism.

SETTING

Stanford University Eye Laser Center, Stanford, California, USA.

METHODS

This retrospective analysis was of the initial 140 eyes of 78 patients treated consecutively with LASIK for myopia using the Visx Star S4 excimer laser. Primary outcome variables, including uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), manifest refraction, and complications, were evaluated at 1 week and 1 and 3 months. Vector analysis was performed on eyes that received astigmatic correction.

RESULTS

Mean preoperative spherical equivalent (SE) was reduced from -3.89 diopters +/- 1.48 (SD) to an SE of -0.21 +/- 0.36 D at 1 month and -0.28 +/- 0.36 D at 3 months (P < .001). At 1 and 3 months, UCVA was 20/20 or better in 84.3% and 87.9%, respectively. Eighty-six percent of eyes at 1 month and 81.4% of eyes at 3 months were within +/-0.5 D of emmetropia. No eyes lost more than 2 lines of BSCVA. Vector analysis yielded an index of success of 0.39, indicating a 61% success rate in achieving the astigmatic surgical correction at 3 months. The preoperative root-mean-square value of 0.28 +/- 0.08 microm increased slightly to 0.33 +/- 0.11 microm at 1 month and 0.34 +/- 0.11 microm at 3 months.

CONCLUSION

Wavefront-guided LASIK using the Visx CustomVue system was effective, predictable, and safe for correction of low to moderate myopic refractive error.

Application of infrared light for in vivo neural stimulation

A novel method for damage-free, artifact-free stimulation of neural tissue using pulsed, low-energy infrared laser light is presented. Optical stimulation elicits compound nerve and muscle potentials similar to responses obtained with conventional electrical neural stimulation in a rat sciatic nerve model. Stimulation and damage thresholds were determined as a function of wavelength using a tunable free electron laser source (lambda = 2 to 10 microm) and a solid state holmium:YAG laser (lambda = 2.12 microm). Threshold radiant exposure required for stimulation varies with wavelength from 0.312 Jcm2 (lambda = 3 microm) to 1.22 Jcm2 (lambda = 2.1 microm). Histological analysis indicates no discernable thermal damage with suprathreshold stimulation. The largest damage/stimulation threshold ratios (>6) were at wavelengths corresponding to valleys in the IR spectrum of soft tissue absorption (4 and 2.1 microm). Furthermore, optical stimulation can be used to generate a spatially selective response in small fascicles of the sciatic nerve that has significant advantages (e.g., noncontact, spatial resolution, lack of stimulation artifact) over conventional electrical methods in diagnostic and therapeutic procedures in neuroscience, neurology, and neurosurgery.

Topography-guided Custom Retreatments in 27 Symptomatic Eyes

PURPOSE

To evaluate the use of topography-guided ablations for refractive irregularities induced by previous surgery.

METHODS

This prospective, non-comparative trial comprised 27 symptomatic eyes with a history of LASIK for myopia that underwent topography-guided treatment with the ALLEGRETTO WAVE system. Pre- and postoperative refraction, uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), corneal asphericity (Q value), low contrast sensitivity, and patient's subjective assessment of improvement were measured.

RESULTS

Preoperative data were sphere -0.84 +/- 1.37 diopters (D), cylinder -1.55 +/- 0.78 D, UCVA 20/49 +/- 0.22, BSCVA 20/32 +/- 0.15, and Q value 1.46 +/- 0.79. Postoperative data at mean 6-month follow-up were: sphere -0.61 +/- 0.81 D, cylinder -0.53 +/- 0.58 D, UCVA 20/25 +/- 0.21 (P < .01), BSCVA 20/21 +/- 0.14 (P < .001), and Q value 1.07 +/- 0.89. Contrast sensitivity scores improved by 70%. No loss of BSCVA occurred in any patient.

CONCLUSIONS

Topography-guided treatments may be effective in correcting the quality of vision. It should be viewed as a possible two-step procedure due to spherical adjustment that may change refraction unpredictably.

Orbscan computerized topography: Attributes, applications, and limitations

An extensive electronic search was undertaken in January 2004 to identify all relevant peer-reviewed publications on Orbscan slit-scanning/Placido computerized topography. Ninety-one publications were identified. These address elevation topography and best-fit sphere, accuracy and repeatability of anterior and posterior corneal elevation and keratometric maps, comparison of Orbscan-acquired data and Placido-based computerized videokeratography instruments, pachymetry measurement and correlation with ultrasound, screening eye-bank corneas, detection of keratoconus, identifying corneal ectasia after refractive surgery, and miscellaneous applications. Studies were analyzed and critically compared in relation to attributes, applications, and limitations of Orbscan corneal topography. The review highlights advantages of this technique in assessing the cornea in health and disease and after surgery and identifies specific aspects that require further investigation and clarification.