Photorefractive keratectomy for hyperopia: long-term nonlinear and vector analysis of refractive outcome

Three-Month Outcomes of Laser Vision Correction for Myopia and Hyperopia in Adults With Amblyopia

PURPOSE

To evaluate the visual outcomes of laser vision correction in adults with myopic and hyperopic amblyopia.

METHODS

The medical records of patients diagnosed as having amblyopia who underwent laser refractive surgery between February 2013 and October 2017 were retrospectively reviewed. Eyes with amblyopia were analyzed, and the nonamblyopic fellow eyes of the patients who underwent laser vision correction were used as controls. The uncorrected distance visual acuity (UDVA), subjective manifest refraction, and corrected distance visual acuity (CDVA) were analyzed at the 3-month postoperative time point.

RESULTS

This study included 323 eyes of 164 patients. All patients underwent laser in situ keratomileusis (90.1%, 291 eyes) or photorefractive keratectomy (9.9%, 32 eyes). Three months postoperatively, the manifest spherical equivalent was -0.07 ± 0.55 diopters (D) (range: -1.75 to +1.30 D) and -0.10 ± 0.54 D (range: -2.13 to +1.30 D) in the amblyopia group and fellow eye group, respectively. The percentage of eyes achieving UDVA of 20/20 or better was 16.9% (15 eyes) in the amblyopia group and 61.9% (52 eyes) in the fellow eye group. The percentage of eyes that gained two or more lines of CDVA was 27.9% (24 eyes) in the amblyopia group and 6.2% (5 eyes) in the fellow eye group (P < .01). In the amblyopia group, there was no statistically significant difference in the mean manifest spherical equivalent between the myopic eyes and hyper-opic eyes at any follow-up visit (P = .87, 1 month postoperatively; P = .68, 3 months postoperatively).

CONCLUSIONS

Laser vision correction was found to be effective and safe in adult patients with amblyopia. [J Refract Surg. 2020;36(8):511-519.].

Role of percent peripheral tissue ablated on refractive outcomes following hyperopic LASIK

Objectives

To determine the effect of hyperopic laser in situ keratomileusis (H-LASIK) on corneal integrity, by investigating relationships between proportionate corneal tissue ablated and refractive outcomes at 3 months.

Methods

18 eyes of 18 subjects treated with H-LASIK by Technolas 217c Excimer Laser were included in the study. Orbscan II Topography System was used to determine corneal volume and pachymetry 3mm temporally (3T). The volume of corneal tissue ablated was determined from the laser nomogram. Univariate associations between age, treatment, corneal volume, overall proportion of tissue removed, proportion of tissue removed at 3T, residual bed thickness at 3T and refractive outcomes 3 months post-LASIK were examined and independent factors associated with refractive outcomes determined using linear regression models.

Results

At 3 months post-LASIK, the mean difference to expected refractive outcome was -0.20 ± 0.64 (Range -2.00 to +1.00). In univariate analysis, difference to expected refractive outcome was associated with proportion of tissue removed at 3T (P<0.01, r = -0.605) and total number of pulses (P< 0.05, r = -0.574). In multivariable analysis, difference to expected refractive outcome was associated with the proportion of tissue removed at 3T only.

Conclusion

Subjects undergoing H-LASIK, may present as either over or under-corrected at 3 months. The proportion of tissue removed at 3T was the single significant determinant of this outcome, suggesting unexpected biomechanical alterations resulting in corneal steepening. Future hyperopic LASIK procedures could consider proportionate volume of corneal tissue removed at 3T in addition to laser nomograms to achieve improved refractive outcomes.

Transepithelial Photorefractive Keratectomy for Hyperopia: A 12-Month Bicentral Study

PURPOSE

To investigate the safety, efficacy, and stability of transepithelial photorefractive keratectomy (PRK) for hyperopia.

METHODS

This interventional case series study at two sites included 55 eyes (31 patients) with hyperopia (0.50 to 6.00 diopters [D]), with or without astigmatism (0.00 to -3.00 D), that underwent one-step transepithelial PRK with a Amaris 500-Hz excimer laser (SCHWIND eye-tech-solutions, Kleinostheim, Germany). A 12-month follow-up was conducted. Preoperative and successive postoperative visual acuity, manifest refraction, haze, and other complication data were analyzed.

RESULTS

The preoperative mean spherical equivalent of 2.56 ± 1.90 D improved to emmetropia (-0.08 ± 0.14 D) by 6 months, with subsequent slight mean regression of 0.024 D (range: -0.75 to 0.50) until month 12. Of the treated eyes, 75% and 76.2% were within the target refraction of ±0.50 D at 6 and 12 months postoperatively, respectively. The final mean cylindric refraction was comparable to the preoperative value (-0.94 ± 0.12 to -0.71 ± 0.12 D, P = .17); however, it was induced in 23% of eyes. The preoperative mean uncorrected distance visual acuity logMAR of 0.54 ± 0.05 significantly improved to 0.15 ± 0.03 by month 12 (P < .0001), and 64.2% of the treated eyes gained an uncorrected distance visual acuity of 20/25 or better. Ten eyes (23.8%) lost one line of preoperative corrected distance visual acuity (CDVA). No eye lost two or more lines of preoperative CDVA. Four eyes with a 3+ degree of haze were observed by the final visit. No other notable complications occurred. The low hyperopic eyes exhibited better overall results compared to the moderate hyperopic group.

CONCLUSIONS

One-step transepithelial PRK with the Amaris 500-Hz excimer laser provided reasonable outcomes for the correction of hyperopia with or without mild to moderate astigmatism.

Aspheric Optical Zones in hyperopia with the SCHWIND AMARIS

Purpose

To evaluate the corneal Functional Optical Zone (FOZ) and the Effective Optical Zone (EOZ) of the ablation, among eyes that underwent LASEK/Epi-LASEK treatments for hyperopic astigmatism.

Methods

Twenty LASEK/Epi-LASEK treatments with mean defocus +2.21 ± 1.28 D performed using the SCHWIND AMARIS were retrospectively evaluated at 6-month follow-up. In all cases pre-/post-operative Corneal-Wavefront analyses using the Keratron-Scout (OPTIKON2000) were performed. FOZ-values were evaluated from the Root-Mean-Square of High-Order Wave-Aberration (RMSho), whereas EOZ-values were evaluated from the changes of Root-Mean-Square of High-Order Wave-Aberration (ΔRMSho) and Root-Mean-Square of the change of High-Order Wave-Aberration (RMS(ΔHOAb)). Correlations of FOZ and EOZ with Planned Optical Zone (POZ) and Defocus correction (SEq) were analyzed using a bilinear function.

Results

At six-month, defocus was −0.04 ± 0.44 D, ninety percent eyes were within ± 0.50 D from emmetropia. Mean RMSho increased 0.18 ± 0.22 μm, SphAb −0.30 ± 0.18 μm, and Coma 0.07 ± 0.18 μm 6-month after treatment (6-mm diameter). Mean FOZPre was 7.40 ± 1.48 mm, mean POZ was 6.76 ± 0.22 mm, whereas mean FOZPost was 5.53 ± 1.18 mm (significantly smaller, p < 0.0001; bilinear correlation p < 0.005), mean EOZΔRMSho 6.47 ± 1.17 mm (bilinear correlation p < 0.005), EOZRMS(ΔHOAb) 5.67 ± 1.23 mm (significantly smaller, p < 0.0005; bilinear correlation p < 0.05). EOZ positively correlates with POZ and declines steadily with SEq. A treatment of +3 D in 6.50-mm POZ results in 5.75-mm EOZ (7.75-mm NPOZ), treatments in 7.00-mm POZ result in about 6.25-mm EOZ (8.25-mm nomogrammed POZ).

Conclusions

FOZPost was significantly smaller than FOZPre. EOZΔRMSho was similar to POZ, whereas EOZRMS(ΔHOAb) was significantly smaller. Differences were larger for smaller POZ or larger Defocus. SEq up to +2 D result in EOZ, at least, as large as POZ. For SEq higher than +2 D, a nomogram for OZ can be applied.

Conductive keratoplasty to correct residual hyperopia after cataract surgery

PURPOSE

To evaluate the efficacy, predictability, safety, and stability of conductive keratoplasty (CK) for correcting residual hyperopia after cataract surgery with intraocular lens implantation.

SETTING

Vissum-Instituto Oftalmologico de Alicante, Alicante, and Vissum-Instituto de Albacete, Albacete, Spain.

METHODS

Sixteen eyes of 16 patients had CK for the correction of residual hyperopia after cataract surgery. The CK was performed with the CK View Point Refractec (RCS-200, Refractec, Inc.). The follow-up was 12 months.

RESULTS

One year after CK, 10 eyes (62.5%) achieved an uncorrected visual acuity (UCVA) of 0.50 or better. The mean UCVA was 0.50 +/- 0.21 (SD), and the mean best spectacle-corrected visual acuity (BSCVA) was 0.68 +/- 0.24. One eye lost 1 line of BSCVA, and none lost 2 or more lines. The mean spherical equivalent refraction was +0.39 +/- 0.84 D 1 year after CK. No vision-threatening complications occurred.

CONCLUSIONS

One-year data show that CK for the correction of low to moderate hyperopia after cataract surgery was safe, stable, relatively predictable, and efficient. No complications occurred when CK was performed after phacoemulsification.

Surgical Correction of Hyperopia

Surgical attempts to correct hyperopia have yielded varying results over the last 130 years. These techniques include the reshaping of the cornea through incisions, burns, or lamellar cuts with removal of peripheral tissue; the addition of central inlays; laser ablations; and the replacement of the crystalline lens. By examining the success of each surgical technique, the refractive surgeon may be able to make an informed decision on its indications and limitations, based on the specific patient's characteristics. Reporting the outcomes and complications of hyperopic surgery will help refine our approach to the management of an increasingly hyperopic and presbyopic population.

Conductive Keratoplasty for the Correction of Residual Hyperopia After LASIK

PURPOSE

To report the 6-month results concerning efficacy, safety, predictability, and stability of conductive keratoplasty for the correction of residual hyperopia after corneal refractive surgery.

METHODS

A total of 35 eyes (26 patients) with residual hyperopia after corneal refractive surgery ranging between +1.00 to +4.75 diopters (D) of spherical equivalent refraction were enrolled in the study and underwent conductive keratoplasty following a modified nomogram.

RESULTS

Variables and data were available for all eyes at 6 months postoperatively. A total of 24 (69%) eyes had uncorrected visual acuity (UCVA) of > or = 20/40, and 10 (29%) eyes had UCVA of 20/20. Manifest refractive spherical equivalent was within +/- 0.50 D in 17 (49%) eyes and within +/- 1.00 D in 25 (71%) eyes in cases of previous hyperopic LASIK; the optical zone was significantly increased.

CONCLUSIONS

Using a modified nomogram, conductive keratoplasty for correction of residual hyperopia was effective, but predictability was not satisfactory and safety needs to be established.

A Comparison of Induced Astigmatism in Conventional and Wavefront-guided Myopic LASIK Using LADARVision4000 and VISX S4 Platforms

PURPOSE

To evaluate and compare the surgically induced astigmatism in myopic eyes undergoing conventional and wavefront-guided LASIK.

METHODS

A retrospective review was performed of the charts of 200 myopic eyes of 121 patients who underwent either custom or conventional treatments via the VISX S4 or LADARVision4000 platforms (50 consecutive eyes in each of the four groups). The primary outcome measure was manifest refraction, which was evaluated preoperatively and at 3 months postoperatively. The magnitude and axis of the unintended surgically induced astigmatism were calculated using vector analysis. The Student t test was used to compare the magnitudes of the surgically induced astigmatism and the absolute angle of error.

RESULTS

The mean preoperative manifest cylinder was 0.66 +/- 0.38 diopters (D) for conventional VISX S4 and 0.68 +/- 0.39 D for VISX CustomVue (P = .795), and 0.76 +/- 0.56 D for LADARVision and 0.61 +/- 0.36 D for LADAR CustomCornea (P = .114). The success index was 0.19 +/- 0.41 for VISX S4 and 0.49 +/- 0.49 for VISX CustomVue (P = .0013), and 0.25 +/- 0.47 for LADARVision and 0.20 +/- 0.39 for LADAR CustomCornea (P = .5721). The absolute mean angle of error was 4.4 +/- 13.9 degrees for VISX S4 versus 14.9 +/- 23.9 degrees for VISX CustomVue (P = .0085), and 6.1 +/- 12.30 for LADARVision versus 3.9 +/- 11.1 degrees for LADAR CustomCornea (P = .3501). Of the VISX CustomVue eyes, 32% had an absolute angle of error > 10 degrees, as compared to 10% for both the VISX S4 and LADAR CustomCornea eyes (P = .013), and 16% for the LADARVision group (P = .056).

CONCLUSIONS

Wavefront-guided ablation is associated with higher surgically induced astigmatism and larger astigmatic axis shift on the VISX platform as compared to the LADAR CustomCornea and the LADAR and VISX conventional platforms. Care should be emphasized mainly during registration/alignment to minimize surgically induced astigmatism in wavefront-guided LASIK.

Laser in situ Keratomileusis for Hyperopia and Hyperopic and Mixed Astigmatism With LADARVision Using 7 to 10-mm Ablation Diameters

PURPOSE

To evaluate the results of laser in situ keratomileusis (LASIK) performed to correct hyperopia, and hyperopic and mixed astigmatism using wider ablation diameters (optical zone diameter and overall ablation diameter) than those commonly used with the same and other lasers.

METHODS

After flap creation using an Alcon SKBM microkeratome set for a 10-mm flap diameter, 53 eyes (33 patients) with a mean spheroequivalent attempted correction of +2.34 +/- 2.09 D underwent LASIK (Alcon LADARVision 4000) using a 7-mm optical zone diameter and a 3-mm transition zone for an overall 10-mm total ablation diameter. The nasal hinge was prevented from undesired ablation by the use of proprietary hinge protector software. Eyes were followed for 6 months after surgery.

RESULTS

Six months after surgery, mean spheical equivalent refractive error was -0.22 +/- 0.41 D. There were 79.2% of eyes within +/- 0.50 D, and 98.1% within +/- 1.00 D of intended correction. Uncorrected visual acuity of 20/20 or better was achieved by 28 eyes (53%) and 20/40 or better by 50 eyes (94.3%). No meaningful visual complaints during nighttime hours, such as haloes or glare, were subjectively reported by patients.

CONCLUSION

The use of larger ablation diameters in LASIK for hyperopia, and hyperopic and mixed astigmatism produced accurate results, early refractive stability, and good visual performance.

Scraping and Mitomycin C to Treat Haze and Regression After Photorefractive Keratectomy for Myopia

PURPOSE

To evaluate the efficacy, safety, and predictability of therapeutic scraping and application of a diluted 0.02% mitomycin C solution to treat haze and regression after photorefractive keratectomy (PRK) for myopia.

METHODS

We performed a non-comparative, non-randomized retrospective study of 35 eyes of 30 patients who had previously undergone PRK for myopia and developed haze and regression after treatment. The range of refractive error after regression was -0.75 to -5.50 D (mean -2.92 D). Haze, ranging from grade 3 to 4 (scale: 0 to 4) caused a best spectacle-corrected visual acuity loss of 1 to 6 Snellen lines. All eyes were treated 6 to 12 months after PRK by scraping the stromal surface and application of a 0.02% mitomycin C solution for 2 minutes using a soaked merocel sponge. No laser ablation was performed. Corneal transparency, refractive error, and visual outcomes were evaluated over a 12-month follow-up period.

RESULTS

All eyes had significant improvement in corneal transparency. Thirty-one eyes had haze grades lower than 1, which were maintained over time. Only four eyes showed haze grades 1 to 2 and two of them needed further treatment using the same technique. At 12 months after treatment, all eyes were within +/-1.50 of original intended correction (mean 0.04 +/- 0.63 D). BSCVA improved in all eyes. No toxic effects were observed during re-epithelialization or during follow-up.

CONCLUSION

Single application of diluted mitomycin C 0.02% solution following scraping of the corneal surface was effective and safe in treating haze and regression after PRK.

Photorefractive keratectomy versus laser in situ keratomileusis for the treatment of spherical hyperopia

OBJECTIVE

To compare photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) in treating spherical hyperopia using the VISX STAR S2 excimer laser.

INTERVENTION

Fifteen consecutive eyes of 15 patients underwent PRK, and 16 consecutive eyes of 16 patients underwent LASIK (follow-up: 12 months).

MAIN OUTCOME MEASURES

Postoperative pain, uncorrected visual acuity (UCVA), deviation from intended correction, and loss of best spectacle-corrected visual acuity (BSCVA).

RESULTS

Mean preoperative spherical equivalent was + 2.18 diopter [D] for PRK and + 2.03D for LASIK. All PRK patients experienced significant postoperative pain that required systemic medication, whereas LASIK patients had minor and transient discomfort. Mean deviation from intended correction was -0.83D, + 0.01D, and + 0.18D at 1, 6, and 12 months after PRK, and + 0.22D, +0.30D, and + 0.40D at 1, 6, and 12 months after LASIK (P = 0.002 at 1 month). A higher proportion of LASIK eyes had a UCVA of 20/20 or better at all time points (P = 0.013 and 0.025 at 1 and 3 months, respectively). There was no statistically significant difference between both groups in BSCVA loss.

CONCLUSIONS

LASIK and PRK are comparable in efficacy and safety. However, PRK was more painful, with an initial and temporary myopic over-correction that did not occur after LASIK. Stability was achieved between 3 and 6 months following PRK, and one month following LASIK.

Concomitant Effect of Topical Ubiquinone Q10 and Vitamin E to Prevent Keratocyte Apoptosis After Excimer Laser Photoablation in Rabbits

PURPOSE

To investigate in vivo whether ubiquinone Q10 together with vitamin E protects rabbit corneas from keratocyte apoptosis after excimer laser irradiation.

METHODS

Photorefractive keratectomy (PRK) was performed in both eyes of three New Zealand white rabbits. During 3 days before surgery, each right eye received four-times-daily instillation of an eye-drop solution containing ubiquinone Q10 0.20% and vitamin E 0.04%; each left eye was treated with a solution that did not contain ubiquinone or vitamin E. The central cornea was analyzed after surgery using the in situ end labelling (ISEL) technique of nicked DNA to detect DNA fragmentation. To determine the number of ISEL positive nuclei, an average of 70 random microscopic fields (five for each de-epithelialized tissue section) of 138,000 mu2 were examined in the right and left cornea samples at 250X by two different observers.

RESULTS

Light microscopic examination of the sections from corneas treated before PRK showed that cells committed to apoptosis by PRK were about 50% compared to those of untreated controls.

CONCLUSION

Treatment of rabbit eyes before PRK with ubiquinone Q10 lowered the number of apoptotic events.

Laser in situ keratomileusis for myopia and astigmatism: safety and efficacy: a report by the American Academy of Ophthalmology

OBJECTIVE

This document describes laser in situ keratomileusis (LASIK) for myopia and astigmatism and examines the evidence to answer key questions about the efficacy and safety of the procedure.

METHODS

A literature search conducted for the years 1968 to 2000 retrieved 486 citations and an update search conducted in June 2001 yielded an additional 243 articles. The panel members reviewed 160 of these articles and selected 47 for the panel methodologist to review and rate according to the strength of evidence. A Level I rating is assigned to properly conducted, well-designed, randomized clinical trials; a Level II rating is assigned to well-designed cohort and case-control studies; and a Level III rating is assigned to case series and poorly designed prospective and retrospective studies, including case-control studies.

RESULTS

The assessment describes randomized controlled trials published in 1997 or later (Level I evidence) and more recent comparative and noncomparative case series (Level II and Level III evidence), focusing on results for safety and effectiveness. It is difficult to extrapolate results from these studies that are comparable to current practices with the most recent generation lasers because of the rapid evolution of LASIK technology and techniques. It is also difficult to compare studies because of variations in the range of preoperative myopia, follow-up periods, lasers, nomograms, microkeratomes and techniques, the time frame of the study, and the investigators' experience.

CONCLUSIONS

For low to moderate myopia, results from studies in the literature have shown that LASIK is effective and predictable in terms of obtaining very good to excellent uncorrected visual acuity and that it is safe in terms of minimal loss of visual acuity. For moderate to high myopia (>6.0 D), the results are more variable, given the wide range of preoperative myopia. The results are similar for treated eyes with mild to moderate degrees of astigmatism (<2.0 D). Serious adverse complications leading to significant permanent visual loss such as infections and corneal ectasia probably occur rarely in LASIK procedures; however, side effects such as dry eyes, night time starbursts, and reduced contrast sensitivity occur relatively frequently. There were insufficient data in prospective, comparative trials to describe the relative advantages and disadvantages of different lasers or nomograms.

Prevention of corneal keratocyte apoptosis after argon fluoride excimer laser irradiation with the free radical scavenger ubiquinone Q10

PURPOSE

To assess in vitro the potential of the free radical scavenger ubiquinone Q10 in preventing keratocyte apoptosis after argon fluoride (ArF) excimer laser irradiation.

METHODS

Cultured rabbit keratocytes were irradiated at very low single-pulse laser fluences. The cumulative effects generated by three total fluence doses between 12 and 45 mJ/cm2, representative of single-pulse subablative doses during photorefractive keratectomy (PRK) in humans, were evaluated. We employed the following parameters to compare pretreated (10 microM ubiquinone Q10) and untreated samples: 1) number and morphology of living cells by Trypan blue test and ultramicroscopy, respectively; 2) level of free-radical formation assessed by malonaldehyde quantitation; 3) cellular energy level evaluated by ATP assay.

RESULTS

Excimer laser irradiation kills cultured keratocytes by inducing apoptosis. The effect increases with the cumulative fluence dose. In the samples pretreated with ubiquinone Q10 there were significantly fewer cumulative apoptotic events than in the untreated ones. Quantitative analysis of malonaldehyde cellular levels suggested this protective action of ubiquinone Q10 was connected with its ability to scavenge laser-generated free radicals. ATP assay also confirmed that it raised cellular energy levels.

CONCLUSIONS

The treatment of corneal keratocytes with relatively low concentrations of ubiquinone Q10 can prevent apoptosis after ArF excimer laser irradiation. If these findings are confirmed on human keratocytes this treatment could be usefully exploited in the PRK surgical procedure. That might lead to a reduction in the occurrence of haze and curvature regression triggered by programmed cell death.