Prospective Study of Photorefractive Keratectomy for Myopia Using the VISX StarS2 Excimer Laser System

Outcomes of photorefractive keratectomy following laser in situ keratomileusis: a cohort study

OBJECTIVE

To analyze the outcomes of photorefractive keratectomy (PRK) on residual myopia and hyperopia post-laser in situ keratomileusis (LASIK) and to compare these results with PRK on eyes without previous laser refractive surgery.

DESIGN

Retrospective comparative cohort study.

PARTICIPANTS

Patients undergoing PRK between 2006 and 2010 were reviewed.

METHODS

Patients were divided into 4 groups, myopic or hyperopic PRK post-LASIK (mPRK-PL and hPRK-PL, respectively) and myopic or hyperopic PRK on corneas without previous laser refractive surgery (mPRK and hPRK, respectively). Uncorrected and corrected distance visual acuity, mean refractive spherical equivalent (MRSE), and mean keratometry and aberrations (total, higher order [HOA], coma, trefoil, and spherical aberration) were recorded at months 3 and 6 postoperatively, as were complications and attempted versus achieved MRSE.

RESULTS

Thirty-three eyes of 25 patients who underwent PRK post-LASIK (21 eyes of 14 patients for hPRK-PL and 12 eyes of 11 patients for mPRK-PL) and 35 eyes of 21 patients who underwent PRK on virgin eyes (11 eyes of 8 patients for hPRK and 24 eyes of 13 patients for mPRK) were included in the study. The only significant differences in outcomes were found to be HOA at 3 months for hPRK-PL as compared with both hPRK and mPRK. Achieved MRSE was significantly different from expected MRSE for hPRK-PL at 3 months postoperatively. No haze- or flap-related complications were observed.

CONCLUSION

Outcomes of PRK were not different in myopic and hyperopic corrections post-LASIK by 6 months or when compared with PRK in virgin eyes. HOA may render hPRK-PL results less predictable early in the postoperative period.

Photorefractive keratectomy in the correction of astigmatism using Schwind Amaris 750s laser

AIM

To evaluate the results of three photorefractive keratectomy (PRK) procedures in the treatment of astigmatism.

METHODS

In this retrospective comparative case series, 89 eyes of 50 patients who underwent PRK treatment for astigmatism were enrolled. The patients were divided into 3 groups based on the PRK procedure: Group 1: PRK without mitomycin-C (MMC) application, Group 2: PRK with MMC application, and Group 3: Trans-Photorefractive Keratectomy (T-PRK). The efficacy, safety, predictability, and complications of treatment were assessed at 1, 3 and 6 months after the treatment.

RESULTS

At postoperative 6 months, the percentage of postoperative uncorrected visual acuity (UCVA) of 20/20 or better was 55.6% (20 eyes) in group 1, 75% (15 eyes) in group 2, and 75.8% (25 eyes) in group 3 (P=0.144). The percentage of postoperative best corrected visual acuity (BCVA) of unchanged or gained ≥1 lines was 80.6% (29 eyes) in group 1, 70% (14 eyes) in group 2, and 90.9% (30 eyes) in group 3 (P=0.151). The percentage of postoperative BCVA of lost ≥2 lines was 11.1% (4 eyes) in group 1, 20% (4 eyes) in group 2, and 6.1% (2 eyes) in group 3. The mean manifest refractive spherical equivalent (MRSE) and mean cylindrical refraction were not significantly different among the each groups (P>0.05). At postoperative 6 months, the percentage of MRSE of within ±0.50 D was 100% (36 eyes) in Group 1, 100% (20 eyes) in Group 2, and 93.9% (31 eyes) in Group 3. At the each follow-up period, there was no significant difference in number of eyes with haze and mean haze score(P>0.05).

CONCLUSION

The study showed that PRK without MMC, PRK with MMC and T-PRK appears to have similar effectiveness, safety and predictability in the treatment of astigmatism. The incidence of haze was also similar between the three groups.

Efficacy of laser in situ keratomileusis in correcting anterior and non-anterior corneal astigmatism: comparative study

PURPOSE

To compare the efficacy of conventional laser in situ keratomileusis (LASIK) in treating corneal astigmatism and in treating noncorneal ocular residual astigmatism.

SETTING

Private practice, Nashville, Tennessee, USA.

DESIGN

Retrospective case series.

METHODS

The records of dominant eyes of consecutive patients who had LASIK were retrospectively analyzed to compare the efficacy of LASIK in eyes with predominantly anterior corneal astigmatism with the efficacy in eyes with predominantly ocular residual astigmatism (ORA). The ORA was determined by vector analysis using refractive cylinder and topographic astigmatism. Preoperatively, the ratio of ORA to preoperative refractive cylinder (R) was used to divide the patients into 2 groups; that is, eyes with predominantly anterior corneal astigmatism (ORA/R ratio <1.0) and eyes with predominantly ORA (ORA/R ratio ≥1.0). Efficacy was determined by examining the magnitude of the remaining uncorrected astigmatism and comparing the index of success (proportion of preoperative refractive astigmatism that remained uncorrected by LASIK) between the 2 groups.

RESULTS

The study evaluated 61 eyes of 61 patients. Conventional LASIK was twice as efficacious in the low-ORA group as in the high-ORA group. The index of success was 0.24 and 0.50, respectively, and the difference between groups was statistically significant (P = .036).

CONCLUSION

The efficacy of astigmatic correction by LASIK was significantly higher in eyes in which the preoperative refractive astigmatism was located mainly on the anterior corneal surface than in eyes in which it was mainly located posterior to the anterior corneal surface.

Effect of higher order aberrations on contrast sensitivity function in myopic eyes

PURPOSE

To evaluate the relation between higher order aberrations (HOAs) and contrast sensitivity function (CSF) in a population with myopia.

METHODS

In this case series, HOAs were measured in 70 myopic eyes over a 6-mm pupil. Contrast sensitivity was also measured. From the contrast sensitivity data, the area under the log contrast sensitivity function (AULCSF) was calculated. Pupil diameter was measured under photopic conditions.

RESULTS

Seventy right eyes of 70 myopic subjects with a mean age of 26.6 +/- 5.7 years were studied. The mean spherical equivalent and refractive astigmatism were -4.97 +/- 1.6 D and 0.93 +/- 0.5 D, respectively. AULCSF was significantly but negatively correlated with the cycloplegic spherical equivalent (r (2) = 0.57, P = 0.02), the root mean square (RMS) of total HOAs (r (2) = 0.065, P = 0.03), the RMS of fourth-order aberrations (r (2) = 0.089, P = 0.015), and the RMS of the spherical aberration (r (2) = 0.037, P = 0.004). AULCSF did not have any significant association with age, photopic pupil diameter, refractive astigmatism, or the RMS of the coma aberration.

CONCLUSION

Spherical and fourth-order aberrations significantly affect CSF in myopic eyes. However, the effect of myopia on CSF cannot be attributed only to HOAs. Other factors such as neural elements in the visual pathway should be taken into account.

Visual performance after overnight orthokeratology

PURPOSE

To investigate visual performance after overnight orthokeratology in terms of changes from baseline values, regression of the orthokeratology effect over time, and evaluation of the best-corrected vision after treatment. In particular, to evaluate any residual visual deficits over the duration of a day due to the abnormal corneal topography induced by orthokeratology treatment.

METHOD

One eye of each of six subjects was fitted with custom designed BE orthokeratology lenses (Capricornia, Brisbane, Australia), with the fellow eye acting as a control. Unaided vision, subjective sphero-cylindrical refraction, high contrast high luminance visual acuity, low contrast high luminance visual acuity, high contrast low luminance visual acuity and letter contrast sensitivity were measured at baseline and after one night (Day 1) and eight nights (Day 8) of lens wear. Except for baseline, data were collected after overnight lens wear immediately after lens removal, and again 3, 6 and 9h after lens removal. At each time point throughout the day, the visual performance measures were evaluated with the initial refraction of the day (the 0h refraction) and also using the optimum subjective refraction at each measurement time. This method was used to evaluate the practical visual performance to be expected after orthokeratology treatment and the residual visual deficits arising from any induced corneal changes after correction of defocus.

RESULTS

As expected, orthokeratology lens wear significantly changed unaided vision and refraction from baseline. However, it did not significantly affect visual acuity in different contrast conditions, or contrast sensitivity. The spherical component of refraction was the only parameter to exhibit regression over each day (p=0.021), with more stability demonstrated on Day 8 than Day 1 (p=0.012). There were no statistically significant changes of best-corrected acuity from baseline in the differing contrast and luminance conditions.

CONCLUSION

Apart from the predicted improvements in unaided vision and reduction of the myopic refractive error, orthokeratology treatment was not found to significantly change any other aspects of visual acuity and contrast sensitivity. All visual performance measures exhibited stability over a 9-h period. Spherical refractive error changed significantly on Day 1 but became stable after a week of treatment. These results indicate that the corneal topography changes induced by orthokeratology do not induce changes in aberrations that are large enough to significantly diminish visual performance.

Contrast sensitivity function and ocular higher-order wavefront aberrations in normal human eyes

PURPOSE

To investigate the relation between contrast sensitivity function and ocular higher-order wavefront aberrations in normal human eyes.

STUDY DESIGN

Prospective observational case series.

PARTICIPANTS

Three hundred seven eyes of 161 normal subjects, ranging in age from 15 to 60 years (30.9+/-8.0 [mean +/- standard deviation]).

METHODS

Ocular higher-order aberrations were measured for a 4-mm pupil using the Hartmann-Shack wavefront analyzer. The root-mean-square of the third- and fourth-order Zernike coefficients was used to represent comalike and spherical-like aberrations, respectively. We measured contrast sensitivity, low-contrast visual acuity (VA), and letter contrast sensitivity. From the contrast sensitivity data, the area under the log contrast sensitivity function (AULCSF) was calculated. Pupil diameter in a photopic condition was recorded using a digital camera.

RESULTS

Multiple linear regression analysis revealed that comalike aberration (P = 0.002) was significantly associated with AULCSF, but spherical-like aberration (P = 0.200), age (P = 0.185), and photopic pupil diameter (P=0.252) were not. Comalike aberration showed a significant correlation with low-contrast VA (P<0.001), but spherical-like aberration (P = 0.293), age (P = 0.266), and pupil diameter (P = 0.756) did not. Comalike aberration was found to be significantly associated with letter contrast sensitivity (P<0.001), but spherical-like aberration (P=0.082), age (P = 0.370), and pupil diameter (P = 0.160) were not.

CONCLUSIONS

In normal human eyes, comalike aberration of the eye significantly influences contrast sensitivity function.

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.

Wound-healing response and refractive regression after conductive keratoplasty

PURPOSE

To characterize the histological changes that occur after conductive keratoplasty (CK) using a rabbit model.

SETTING

LSU Eye Center and Neuroscience Center of Excellence, Louisiana State University Health Sciences Center, School of Medicine, New Orleans, Louisiana, USA.

METHODS

Conductive keratoplasty was performed on 24 eyes of 12 New Zealand albino rabbits. In each eye, 24 spots were placed in a cross-corneal manner using 3 optical zones at 6.0, 7.0, and 8.0 mm. Eyes were assessed with corneal topography weekly. Rabbits were humanely killed 2, 4, 6, and 8 weeks postoperatively. The eyes were then enucleated and processed for histopathology and immunohistochemical analysis.

RESULTS

All eyes showed an initial mean steepening of the corneal curvature of 2.24 diopters (D) 2 weeks postoperatively. Corneal topography revealed a 26%, 36%, and 39% regression of the refractive results at 4, 6, and 8 weeks, respectively. Immunohistochemical analysis demonstrated keratocyte apoptosis, myofibroblast appearance, and upregulation of chondroitin sulfate, MMP-1, and collagen III in the area surrounding the tip in each spot.

CONCLUSION

The histological changes that occur after CK may be responsible for the well-established regression of its refractive effect. A better understanding of the wound-healing response after CK is necessary to improve the long-term stability of the procedure.

Long-term results of conductive keratoplasty for low to moderate hyperopia

PURPOSE

To assess the long-term safety, efficacy, predictability, and stability of conductive keratoplasty (CK) for the treatment of low to moderate hyperopia and to evaluate the impact of the procedure on the quality of vision.

SETTING

University of Crete, Medical School, Vardinoyannion Eye Institute of Crete, Crete, Greece.

METHODS

In this prospective nonrandomized noncontrolled single-center study, 38 eyes of 26 patients (13 women and 13 men) were treated for hyperopia with a Refractec ViewPoint CK system and followed for 30 months. Preoperatively, the mean manifest refraction spherical equivalent (MRSE) was +1.89 diopters (D) +/- 0.6 (SD) (range +1.00 to +3.25 D), and the mean follow-up was 30.9 +/- 1.1 months. All eyes were treated with the regular CK nomogram for the treatment of spherical hyperopia. The treatment consisted of 8 to 32 spots applied to the periphery of the cornea. Mean age was 50.3 +/- 8.8 years (range 31 to 71 years). All treated eyes were analyzed for safety, efficacy, predictability, and stability.

RESULTS

At 12 months, the MRSE was -0.06 +/- 0.8 D and at 30 months was -0.02 +/- 0.7 D. At 30 months, the mean MRSE was within +/-0.50 D in 68%, within +/-1.00 D in 92%, and within +/-2.00 D in all eyes. At 30 months, uncorrected visual acuity was 20/20 or better in 52.5% and 20/40 or better in 89% of eyes. No eye lost 2 or more Snellen lines or had an induced cylinder of 2.00 D or greater. The procedure did not cause statistically significant changes in contrast sensitivity.

CONCLUSION

Results show that CK for low to moderate hyperopia is a safe, effective, predictable, and stable procedure.

Wavefront-guided laser in situ keratomileusis using the WaveScan system for correction of low to moderate myopia with astigmatism: 6-month results in 277 eyes

PURPOSE

To assess the safety and effectiveness of wavefront guided LASIK surgery using the Visx WaveScan system for correction of low to moderate myopia with astigmatism.

SETTING

Multicenter study at 6 sites in the United States.

METHODS

In this prospective nonrandomized clinical trial, treatments were performed at 6 sites in the United States using the WaveScan (CustomVue) guided excimer laser. A total of 351 eyes were enrolled, and 277 eyes were analyzed at 6 months.

RESULTS

At 6 months, 94% of eyes achieved an uncorrected visual acuity (UCVA) of 20/20 or better and 74% achieved a UCVA of 20/16 or better. Sixty-nine percent of eyes had the same or better postoperative UCVA than their preoperative best spectacle-corrected visual acuity (BSCVA). Ninety percent of eyes were within +/-0.5 diopter of intended correction. No eye lost more than 1 line of BSCVA. Total higher-order root-mean square (RMS), coma, and spherical aberration values were stable (P<.05).

CONCLUSION

The data support the safety and effectiveness of the WaveScan-guided customized laser ablation using the Visx Star S4 system for correction of low to moderate myopia with astigmatism.

Thin flap laser in situ keratomileusis: analysis of contrast sensitivity, visual, and refractive outcomes

PURPOSE

To analyze refractive, visual, and contrast sensitivity outcomes of laser in situ keratomileusis (LASIK) performed under thin flaps (less than 100 microm), and compare them with those of conventional thicker flaps.

SETTING

Clínica Baviera, Instituto Oftalmológico Europeo, Madrid, Spain.

METHODS

This retrospective study comprised 280 consecutive eyes that had LASIK for myopia using the Moria LSK-One microkeratome and the Technolas 217C excimer laser. Efficacy, predictability, and contrast sensitivity indicators were compared between 3 groups of flap thickness: thin (<100 microm, n = 105), medium (100 to 129 microm, n = 122), and thick (>130 microm, n = 53).

RESULTS

Refractive results were excellent and comparable between the 3 groups; however, visual outcomes-measured as efficacy, postoperative evolution of uncorrected visual acuity, and contrast sensitivity-test were significantly better in the thin flap group. Efficacy results were 92.9%, 91.0%, and 81.0% in the thin, medium, and thick flap groups, respectively (P < .05), and the rate of enhancements was 0%, 2.3%, and 5.6%, respectively. With regard to contrast sensitivity, changes between preoperative and postoperative values at month 3 of follow-up, the thin flap group achieved the preoperative levels at 3 spatial frequencies (3, 6, and 18 cycles per degree), while the thicker flap groups maintained lower than preoperative levels at more than 2 spatial frequencies. When comparing contrast sensitivity values between the 3 groups, the thin flap group also obtained the best results at lower spatial frequencies.

CONCLUSIONS

Thin flap LASIK is a safe technique to correct myopic defects since it blends the advantages of surface and lamellar procedures (minimal debilitation of corneal biomechanical architecture with the rapid and comfortable visual recovery of lamellar approaches). Moreover, it achieves excellent refractive outcomes, a lower rate of enhancements, and a good visual performance with better contrast sensitivity test results.

Contrast sensitivity after implantation of toric iris-claw lenses in phakic eyes

PURPOSE

To evaluate the change in contrast sensitivity after implantation of the Verisyse toric phakic intraocular lens (IOL) (AMO) for the correction of myopia with astigmatism.

SETTING

Department of Ophthalmology, Johannes Gutenberg-University, Mainz, Germany.

METHODS

Eighteen eyes had implantation of an iris-supported toric phakic IOL to correct myopia with astigmatism. The mean preoperative spherical equivalent was -12.65 diopters +/- 3.6 (SD). The contrast sensitivity with best spectacle correction was determined before surgery and 3 months after surgery using the CSV-1000 HGT instrument (Vector Vision Inc.).

RESULTS

Three months after IOL implantation, the mean contrast sensitivity had significantly increased from preoperatively at midrange spatial frequencies from 3.2 to 4.4 (6 cycles per degree [cpd]; P = .033) and from 2.4 to 3.7 (12 cpd; P = .032). The differences at spatial frequencies of 3 cpd and 18 cpd were not statistically significant (P = .59 and P = .086, respectively).

CONCLUSIONS

Implantation of the Verisyse toric iris-claw lens in phakic eyes to correct high or moderate myopia with astigmatism has the potential to improve contrast vision. The mean contrast sensitivity increased considerably at all spatial frequencies compared with preoperative levels.

Reliability and Validity of the Melbourne Edge Test and High/Low Contrast Visual Acuity Chart

PURPOSE

The purposes of the study were to investigate the test-retest reliability and the validity of new versions of the Melbourne Edge Test (MET) and the High/Low Contrast Visual Acuity (H/LCVA) chart and to investigate the agreement between the original and new versions.

METHODS

The MET original photographic version, MET new light box version, H/LCVA Chart original photographic version, H/LCVA Chart new printed version, and the Pelli-Robson chart were administered twice to one eye of 22 subjects with low vision and 20 soft contact lenses wearers.

RESULTS

For the low vision group, the test-retest 95% limits of agreement were +/- 5.2 dB for the MET new light box version and +/- 0.39 logarithm of the minimum angle of resolution (logMAR) for the LCVA component of the H/LCVA new printed version. For the soft contact lens group, the test-retest 95% limits of agreement were +/- 2.1 dB for the MET new light box version and +/- 0.26 logMAR for the LCVA component of the H/LCVA new printed version. Moderate to high correlations were obtained between contrast sensitivity tests, thus providing evidence of validity. Scores obtained for the new test versions were significantly higher than the original versions (p < 0.01).

CONCLUSIONS

Of all the tests administered, the MET original photographic version and the Pelli-Robson Chart had the highest test-retest reliability for the low vision group. For the soft contact lens group, the H/LCVA original version (low contrast letters, 18% Weber) and the Pelli-Robson Chart had the highest reliability.

Eight-year Follow-up of Photorefractive Keratectomy for Myopia

PURPOSE

We evaluated 8-year results of excimer laser photorefractive keratectomy (PRK) for myopia in terms of stability and late complications.

METHODS

Ninety-two myopic eyes of 55 patients were treated with a single-step method using an Aesculap-Meditec MEL 60 excimer laser with a 5.0-mm ablation zone. Treated eyes were divided into three groups according to preoperative refraction: low myopes (< or = -6.00 D), medium myopes (-6.10 to -10.00 D), and high myopes (>-10.00 D).

RESULTS

Change in myopic regression stabilized in all myopia groups within 12 months, although a small myopic shift occurred up to 8 years after PRK. Mean change in refraction between 2 and 8 years was -0.42 +/- 0.48 D for low myopes, -0.37 +/- 0.34 D for medium myopes, and -0.41 +/- 0.50 D for high myopes. The percentage of eyes within +/- 1.00 D of emmetropia 8 years after PRK was 78.3% in the low myopia group, 68.8% in the medium myopia group, and 57.1% in the high myopia group. One eye lost 2 lines of best spectacle-corrected visual acuity due to irregular astigmatism. In 13.0% of eyes, a residual trace corneal haze was observed, which had no effect on visual acuity. Apart from the loss of 2 lines of BSCVA in one eye, there were no other late complications during the study period.

CONCLUSIONS

The mean change in refraction between 2 and 8 years was less than -0.50 D, regardless of preoperative refraction, and may be attributed to natural age-related refractive change. The appearance of residual corneal haze after 8 years correlated with the amount of myopic correction. PRK was a safe and stable surgical procedure in this group of patients.

Two-year results of conductive keratoplasty for the correction of low to moderate hyperopia

PURPOSE

To evaluate the 2-year postoperative safety, efficacy, predictability, and stability results of conductive keratoplasty (CK) to correct low to moderate hyperopia.

SETTING

Department of Ophthalmology, Stanford University Medical Center, Stanford, California, USA.

METHODS

In a prospective nonrandomized noncontrolled trial, 25 eyes of 14 patients with +0.75 to +3.00 diopters (D) of hyperopia and </=0.75 D of cylinder were treated with CK. Low-energy, radio-frequency current was applied to the peripheral corneal stroma through a probe inserted at 8 to 32 treatment spots. An early nomogram was used in 2 eyes, and a current nomogram was used in 23 eyes; the intended refraction was plano. The 23 eyes treated with the current nomogram were analyzed for efficacy, predictability, and stability. All 25 eyes were included in the safety and patient-satisfaction analyses.

RESULTS

Preoperatively, the mean manifest refraction spherical equivalent (MRSE) in the 23 current-nomogram eyes was +1.55 D. At 2 years, the uncorrected visual acuity was 20/20 or better in 64% of eyes and 20/40 or better in 95%. The MRSE was within +/-0.50 D in 64% of eyes, within +/-1.00 D in 91%, and within +/-2.00 D in 100%. No eye lost more than 1 line of best spectacle-corrected visual acuity or had an induced cylinder greater than 0.75 D. The mean MRSE of the cohort with all follow-ups was +0.48 D, which reflected a 29% regression from the intended plano and 43% regression from the 1-month postoperative overcorrection. The rate of regression appeared to be low and decreasing, +0.024 D per month between 12 and 24 months. A patient survey revealed improved quality of vision and a high level of satisfaction.

CONCLUSIONS

Conductive keratoplasty appeared to be safe, effective, and predictable for correcting low to moderate hyperopia. Mild hyperopic regression was observed; however, the rate of regression indicated by the mean change in MRSE per month was low and decreased over the 2-year follow-up. Longer follow-up may be necessary to further characterize the refractive stability of CK.

Laser-assisted subepithelial keratectomy and photorefractive keratectomy for the correction of hyperopia: Results of a 2-year follow-up

PURPOSE

To evaluate and compare the efficacy, safety, predictability, and stability of laser-assisted subepithelial keratectomy (LASEK) and photorefractive keratectomy (PRK) for low to moderate hyperopia with a 2-year follow-up.

SETTING

Department of Ophthalmology, Masaryk University Hospital, Brno, Czech Republic.

METHODS

This prospective comparative single-surgeon study included 216 eyes of 108 patients with hyperopia who received PRK in 1 eye and LASEK in the contralateral eye. The mean patient age was 38.3 years (range 25 to 58 years). The mean preoperative spherical equivalent (SE) cycloplegic refraction was +3.67 diopters (D) +/- 1.15 (SD) (range +2.00 to +5.00 D), and astigmatism was less than 1.00 D. In each patient, PRK was performed in 1 eye (Group A) and LASEK was performed in the other eye (Group B) using the Nidek EC-5000 excimer laser. Postoperative uncorrected visual acuity (UCVA), best corrected visual acuity, contrast sensitivity, manifest and cycloplegic refractions, refractive stability and predictability, postoperative pain, and corneal haze were examined and statistically analyzed. A P value less than 0.05 was considered significant.

RESULTS

At 1 week, the UCVA was 20/40 or better in 58% of PRK eyes and 85% of LASEK eyes (P =.037); at 2 years, it was 20/40 or better in 81% and 91%, respectively (P =.076). At 2 years, the UCVA for near was N8 or better in 73% of PRK eyes and 89% of LASEK eyes (P =.064). No patient lost 2 or more lines of Snellen visual acuity. The safety index was 1.03 in PRK eyes and 1.08 in LASEK eyes. Refractive stability was achieved at 6 months in LASEK eyes and at 12 months in PRK eyes. The mean SE cycloplegic refraction decreased from +3.58 D (PRK eyes) and +3.76 D (LASEK eyes) at baseline to +0.74 D and +0.32 D, respectively, at 2 years; in 57% and 78% of eyes, respectively, the refraction was within +/-0.50 D of the targeted refraction. Peripheral corneal haze scores at 3 to 9 months and pain scores at 1 to 3 days were significantly lower in the LASEK group than in the PRK group.

CONCLUSIONS

Laser-assisted subepithelial keratectomy for hyperopia up to +5.00 D provided good visual and refractive results. It significantly reduced postoperative pain, grade of peripheral ring-shaped corneal haze, and regression of hyperopia. Hyperopic LASEK provided quicker visual recovery and achieved better efficacy, predictability, and refractive stability than hyperopic PRK.

Comparison of designs of laser systems utilized for refractive surgery

Several different laser types are available on the market for the practitioner to use in refractive surgery. Each laser type has certain parameters that the surgeon must understand to obtain the best refractive outcomes. Studies published in peer-reviewed literature between February 2002 and March 2003 show that refractive results across all types of lasers have improved compared with those of several years ago. A difference in refractive outcomes between lasers is impossible to directly compare, as there are no randomized studies that hold surgeon or patient characteristics constant.

Cataract surgery in patients with prior refractive surgery

As the number and types of keratorefractive procedures increase and as the baby boomer population moves into the "cataractous decades," the number of patients requiring cataract surgery following refractive surgery grows larger each year. While technological advances in surgical instrumentation and intraocular lens (IOL) design allow us to perform cleaner, faster, and more reliable cataract extractions, the ultimate postoperative refraction depends primarily on calculations performed before surgery. Third-generation IOL formulas ( Haigis, Hoffer Q, Holladay 2, or SRK/T) provide outstanding accuracy when used for eyes with physiologic, prolate corneas. In addition, most instruments used today for measuring corneal curvature and power were designed before the era of refractive surgery. These formulas and instruments make assumptions about the anatomy and refractive properties of the cornea that are no longer valid following most keratorefractive procedures. These breakdowns in IOL calculation often result in a "refractive surprise" after cataract surgery, which may require subsequent surgical correction. This article examines recent publications of modeling studies of various methods for estimating effective K values for IOL calculation, cataract surgery case series following refractive surgery, new corneal topography technologies and methods for correcting "refractive surprises" postoperatively.