Morning-to-evening change in refraction, corneal curvature, and visual acuity 11 years after radial keratotomy in the prospective evaluation of radial keratotomy study. The PERK Study Group

EVALUATION AND MANAGEMENT OF POST-OPERATIVE COMPLICATIONS FOLLOWING CATARACT EXTRACTION AND INTRAOCULAR LENS PLACEMENT

THIS REVIEW EXPLORES POST-OPERATIVE CHALLENGES ARISING FROM CATARACT SURGERY, INCLUDING INTRAOCULAR LENS (IOL) DECENTRATION OR DISLOCATION, REFRACTIVE SURPRISES, DYSPHOTOPSIAS, AND IOL OPACIFICATIONS. IOL DECENTRATION OR DISLOCATION IS RARE, HIGHLIGHTING THE NEED FOR CAREFUL MANAGEMENT WITH MONITORING, SURGICAL REPOSITIONING OR LENS EXCHANGE TO ACHIEVE OPTIMAL VISUAL OUTCOMES. REFRACTIVE SURPRISES, ATTRIBUTED TO ERRORS IN IOL CALCULATION AND SELECTION, MAY BE MANAGED CONSERVATIVELY OR SURGICALLY, WITH THE MOST ACCURATE RESULTS ACHIEVED BY LASER VISION CORRECTION. POSITIVE AND NEGATIVE DYSPHOTOPSIAS MAY CONTINUE TO BE INTOLERABLE FOR PATIENTS, AND MAY REQUIRE LENS EXCHANGE AS WELL. IOL OPACIFICATIONS VARY BY IOL MATERIAL AND MAY BE VISUALLY SIGNIFICANT, REQUIRING LENS EXCHANGE. WE UNDERSCORE THE IMPORTANCE OF NUANCED MANAGEMENT AND PROVIDING OPTIMAL PATIENT CARE IN THE ABOVE POST-CATARACT SURGERY AND IOL IMPLANTATION COMPLICATIONS.

The VRF-L and VRF-GL IOL power calculation methods after radial keratotomy

BACKGROUND

To investigate the accuracy of the VRF-L and VRF-GL IOL power calculation methods in cataract surgery after radial keratotomy (RK).

METHODS

The VRF-L and VRF-GL methods were collated with nine formulas: Barrett True K (No History), Haigis, Hoffer Q, Hoffer Q (Double-K), Holladay 1 (Double-K), Holladay 2 (Double-K), PEARL-DGS (RK), SRK/T (Double-K), and T2 (Double-K). With SS-OCT biometry (IOLMaster 700, Carl Zeiss Meditec), data of 78 eyes from 78 patients with previous RK was included. Optimised lens constants were sourced from the IOL Con website. Subjective refraction was obtained at 4 to 5 months postoperatively. The root mean square absolute error (RMSAE) and median absolute error (MedAE) were chosen as primary outcomes and the percentage of eyes with PEs within ±0.25 D, ±0.50 D, ±0.75 D, and ±1.00 D were analysed.

RESULTS

Statistical significance (Bootstrap-t test, P < 0.05) was shown by VRF-GL, VRF-L, and Haigis formulas with the lowest RMSAE (0.813 D, 0.816 D and 0.824 D) and MedAE (0.511 D, 0.497 D and 0.533 D) values. The Barrett True K formula was less predictable (0.836 and 0.580, respectively). The VRF-L, VRF-GL, and Haigis achieved the highest percentage of eyes with a PE within ±0.50 D (52.56%, 50.00%, and 46.15%) and ±1.00 D (79.49%, 79.49%, and 80.77% respectively).

CONCLUSION

The VRF-L and VRF-GL methods demonstrated higher accuracy and were comparable with existing methods in eyes after RK. The Haigis was an alternative option with a higher percentage of eyes with a PE within ±1.00 D (80.77%).

Implantation of a toric intraocular lens after repeated radial keratotomy procedures: A case report

Corneal alterations due to radial keratotomy (RK) complicate intraocular lens calculations, which may explain why there have been few reports of toric intraocular lens (TIOL) implantation after excessive or multiple operations. A 71-year-old male with a history of repeated RKs and at least 30 corneal incisions in each eye was referred for cataract surgery. Preoperatively, the best-corrected distance visual acuity was 0.7 decimal (0.15 logMAR) in the right eye and 0.9 decimal (0.05 logMAR) in the left eye. The refractive errors were -8.00 -3.00 × 80 and -6.00 -3.50 × 80, respectively. The total corneal cylindrical powers (real power; anterior and posterior) were, respectively, -0.90 D and -3.60 D at 9 a.m., compared to -1.60 D and -3.80 D at 1 p.m. Corneal astigmatism in the left eye was considered symmetric and diurnally stable; therefore, an XY1AT6 TIOL (Hoya, Tokyo, Japan; cylindrical power at the plane, +3.75 D) was implanted. A non-toric intraocular lens, the XY1 (Hoya), was implanted in the right eye. Six-month postoperative best-corrected distance visual acuities were 1.2 decimal (-0.08 logMAR) and 1.0 decimal (0.00 logMAR) in the right and left eyes, respectively. Post-operative manifest refractions were +0.00 -3.00 × 70 and -1.00 -2.00 × 85, respectively. The TIOL reduced refractive astigmatism in the left eye; therefore, we believe that even after multiple RKs, the TIOL can be a suitable candidate to correct astigmatism if the corneal astigmatism is diurnally stable and symmetric.

Sequential Customized Therapeutic Keratectomy in Patients With a History of Radial Keratotomy

PURPOSE

To evaluate the outcome of sequential customized therapeutic keratectomy (SCTK) in reducing higher order aberrations (HOAs) and improving quality of vision in highly aberrated corneas consequent to previous radial keratotomy (RK).

METHODS

A retrospective review of patients undergoing SCTK treatment from January 2012 to October 2020 was conducted in the Eye Center, Humanitas Clinical and Research Center (Rozzano, Italy). Indications for treatment in patients who had RK were significantly and/or progressively reduced corrected distance visual acuity (CDVA) combined with visual symptoms critically affecting quality of life. Preoperative and postoperative CDVA, corneal topography and aberrometry, Scheimpflug tomography, and anterior segment optical coherence tomography were registered.

RESULTS

Thirty-four patients who underwent RK a mean of 26.62 ± 7.10 years before SCTK treatment were included. SCTK induced a significant improvement of CDVA from 0.44 ± 0.82 logMAR preoperatively to 0.15 ± 0.64 logMAR postoperatively (P < .001). No patient experienced worsening of CDVA, whereas 8 patients (23,50%) gained one line and 23 patients (67.65%) gained two lines or more. A significant decrease in corneal coma, trefoil, and spherical aberrations was also noted (P = .003, .003, and .004, respectively).

CONCLUSIONS

SCTK proved to be a safe and effective option to treat highly aberrated eyes following RK. The authors suggest the use of SCTK as a first-line approach for the treatment of HOAs after RK and avoiding more invasive procedures such as corneal transplantation or intraocular lens implantation. [J Refract Surg. 2023;39(12):808-816.].

Long-Term Stability of Femtosecond Astigmatic Keratotomy After Treatment of High Postkeratoplasty Astigmatism

PURPOSE

The purpose of this study was to assess long-term stability and outcomes of femtosecond astigmatic keratotomy (FSAK) after treatment of high postkeratoplasty astigmatism.

METHODS

This retrospective study included patients who underwent FSAK for high astigmatism (≥4 D) after penetrating keratoplasty or deep anterior lamellar keratoplasty. Main outcome measures were corneal astigmatism, uncorrected visual acuity, and best-corrected visual acuity (BCVA) at 1 month and 1, 5, and 10 years.

RESULTS

Overall, 61 eyes of 61 patients (mean age 56 ± 19 years, 54.1% male) were included in this study. Preoperative corneal astigmatism ranged from 4 to 25 D. One month after FSAK, mean corneal astigmatism was significantly reduced from 9.02 ± 3.97 D to 4.86 ± 3.10 D (P < 0.001). Thereafter, corneal astigmatism remained stable at all visits up to 10 years (P < 0.05 for all compared with baseline). After FSAK, there was a significant improvement in logMAR uncorrected visual acuity from 1.21 ± 0.48 to 0.87 ±0.54 (P < 0.001) and logMAR BCVA from 1.03 ± 0.55 to 0.49 ± 0.45 (P < 0.001) which remained stable up to 10 years. A mild reduction in BCVA improvement was seen between 1 month and 1 year.

CONCLUSIONS

Femtosecond astigmatic keratotomy was effective and stable at reducing very high magnitudes of postkeratoplasty astigmatism over the long term. The procedure also had a stable effect on visual acuity, albeit some reduction in the degree of BCVA improvement was seen over the early postoperative period.

Intraocular lens power calculation after radical keratotomy and photorefractive keratectomy: A case report

RATIONALE

To report a rare case of calculating the IOL power in a cataract patient who underwent both radial keratotomy (RK) and photorefractive keratectomy (PRK).

PATIENT CONCERNS

A 48-year-old woman underwent bilateral RK at age 22 and bilateral PRK at age 46. She developed bilateral corneal haze and corneal endothelial inflammation and received steroids therapy for long time after PRK. Then she was referred to our hospital due to decreased vision in the both eyes.

DIAGNOSES

The patient was diagnosed with binocular complicated cataract, corneal haze, high myopia and post corneal refractive surgery (RK and PRK).

INTERVENTIONS

The patient underwent bilateral phacoemulsification. The IOL power was calculated using SRK/T formula for RK and Haigis-L formula for PRK, respectively. We finally selected the Haigis-L formula and the intraocular lens (SN60WF) was implanted within the capsular bag.

OUTCOMES

After the surgery, both eyes showed myopia drift, and the right eye continuously fluctuated in refractive results. However, by nearly 1 year later, refractive results in both eyes had stabilized, and no other complications had occurred.

LESSONS

IOL power in patients who undergo both RK and PRK can be reliably calculated using the Shammas-PL, Average of multiple formulas, or Barret True-K No History formulas. Haigis-L formula is not suitable. Such patients require at least three months after surgery to attain refractive stability in both eyes.

Comparison of refractive prediction for intraoperative aberrometry and Barrett True K no history formula in cataract surgery patients with prior radial keratotomy

PURPOSE

To compare prediction errors of the Barrett True K No History (Barrett TKNH) formula and intraoperative aberrometry (IA) in eyes with prior radial keratotomy (RK).

METHODS

A retrospective, non-randomized study of all patients with RK who underwent cataract surgery using IA at the UCHealth Sue Anschutz-Rodgers Eye Center from 2014 to 2019 was conducted. Refraction prediction error (RPE) for IA and Barrett TKNH was compared. General linear modelling accounting for the correlation between eyes was used to determine whether absolute RPE differed significantly between Barrett TKNH and IA. Outcome by number of RK cuts was also compared between the two methods.

RESULTS

Forty-seven eyes (31 patients) were included. The mean RPEs for Barrett TKNH and IA were 0.04 ± 0.92D and 0.01 ± 0.92D, respectively, neither was significantly different than zero (p = 0.77, p = 0.91). The median absolute RPEs were 0.50D and 0.48D, respectively (p = 0.70). The refractive outcome fell within ± 0.50D of prediction for 51.1% of eyes with Barrett TKNH and 55.3% with IA, and 80.8% were within ± 1.00D for both techniques. Mean absolute RPE increased with a higher number of RK cuts (grouped into < 8 cuts and ≥ 8 cuts) for both Barrett TKNH (0.35D and 0.74D, p = 0.008) and IA (0.30D and 0.80D, p = 0.0001).

CONCLUSIONS

There is no statistically significant difference between Barrett TKNH and IA in predicting postoperative refractive error in eyes with prior RK. Both are reasonable methods for choosing intraocular lens power. Eyes with more RK cuts have higher prediction errors.

Refractive approaches to visual rehabilitation in patients with keratoconus

PURPOSE OF REVIEW

As keratoconus is a chronic disease affecting young people, vision-related quality of life is often significantly impaired in patients with this disease. However, successful management of keratoconus, including visual rehabilitation strategies, can improve quality of life in these patients. This review will describe clinical approaches that improve vision-related quality of life in patients with stable keratoconus.

RECENT FINDINGS

Several types of contact lenses including scleral lenses have been used successfully to manage keratoconus. Eyes with severe keratoconus, even those in which fitting with other types of lenses is challenging, can be successfully fitted with scleral lenses. Although laser ablative procedures, such as photorefractive keratectomy (PRK) have been traditionally contraindicated in patients diagnosed with or suspected of having keratoconus, PRK has been attempted to partially correct refractive errors in keratoconus. Although phototherapeutic keratectomy and radial keratotomy have been reported to be used in eyes with keratoconus, effectiveness and safety results have varied. Implantation of phakic intraocular lenses and intraocular lenses, including toric intraocular lenses, which primarily correct regular astigmatism, with cataract extraction or refractive lens exchange can improve vision-related quality of life in patients with keratoconus by significantly reducing cylinder while improving uncorrected visual acuity.

SUMMARY

Appropriate selection and application of treatment options based on consideration of multiple factors will help patients with keratoconus, improving their vision-related quality of life and delaying or avoiding keratoplasty.

Multifocal Intraocular Lens Results in Correcting Presbyopia in Eyes After Radial Keratotomy

OBJECTIVES

To report results of multifocal intraocular lens (IOL) implantation in 2 patients with refractive error and presbyopia after previous radial keratotomy (RK).

METHODS

A refractive multifocal IOL with rotational asymmetry (LS313-MF30; Oculentis, Berlin, Germany) was implanted.

RESULTS

The first patient was a 60-year-old man with myopia who underwent unilateral RK 20 years before. His uncorrected distance visual acuity (UDVA) was 20/400, and his distance corrected near vision was J9 in both eyes. Six months after bilateral surgery, his binocular UDVA and uncorrected near visual acuity (UNVA) improved to 20/20 and J1, respectively, although he experienced diurnal fluctuation. The second patient was a 55-year-old woman with hyperopia who underwent bilateral RK 18 years before. Uncorrected distance visual acuity was 20/25 in both eyes, but UNVA was between J9 and J10. Three months after unilateral surgery, UDVA and UNVA of the postsurgical eye improved to 20/20 and J1, respectively. Neither patient reported any significant photic phenomena, and both were satisfied with the results of treatment.

CONCLUSIONS

The desirable clinical outcomes and levels of satisfaction expressed by these patients indicate that surgery using this particular multifocal IOL may benefit presbyopic patients with previous RK.

Intraocular Lens Power Selection after Radial Keratotomy: Topography, Manual, and IOLMaster Keratometry Results Using Haigis Formulas

PURPOSE

To compare final spherical equivalent (SE) refractions in patients who previously underwent radial keratotomy (RK) undergoing routine cataract surgery using keratometry (K) values from the Tomey (Topographic Modeling System [TMS]; Tomey Corp., Phoenix, AZ) Placido topographer, manual keratometer, and IOLMaster (Carl Zeiss Meditec AG, Jena, Germany) keratometer using the Haigis formulas.

DESIGN

Retrospective case series.

SUBJECTS

A total of 26 RK eyes (20 patients) with a minimum of 3 months postoperative follow-up.

METHODS

The following K values were evaluated: TMS topography (flattest K within first 9 rings, average K, minimum K), manual K, IOLMaster K. The final refractive goal was -0.50 diopters (D) for all eyes. The Haigis formula with target refraction -0.50 D was used. In addition, because of observed hyperopic overcorrections, IOLMaster K with the Haigis formula set to -1.00 D but with a final refractive goal of -0.50 D was also tested. The Haigis-L formula using IOLMaster K values was separately evaluated.

MAIN OUTCOME MEASURES

Mean final SE refraction, percent final SE within ideal (-0.12 to -1.00 D), acceptable (0.25 to -1.50 D), or unacceptable (<-1.50 or >0.25 D) range and within ±0.50 D and ±1.00 D of the intended result.

RESULTS

Best results with minimal overcorrections were achieved with TMS flattest K (mean -0.68±0.60 D, 73% within ±0.50 D, and 88% within ±1.00 D of the surgical goal) and IOLMaster K set for target -1.00 D (mean -0.66±0.61 D, 69% within ±0.50 D, and 88% within ±1.00 D of the surgical goal). Other values produced more hyperopic (manual, IOLMaster K set for target -0.50 D, average topography) or higher myopic (minimum topography, Haigis-L) results.

CONCLUSIONS

For simplicity, using the IOLMaster K values combined with the Haigis formula set for target refraction -1.00 D produces acceptable results aiming for -0.50 D final SE refractions in former RK patients undergoing routine cataract surgery.

Multifocal Corneal Excimer Femtosecond Laser in situ Keratomileusis following Radial Keratotomy: A Case Report with Six Months of Follow-Up

We report the case of a 46-year-old female patient who was referred to our clinic (Orasis Eye Clinic, Reinach, Switzerland) seeking improvement of her distance and near visual acuity. Radial keratotomy (RK) was performed at a younger age on both eyes to correct -5 D myopia. The patient underwent a bilateral same-session multifocal corneal excimer femtosecond laser (Supracor) keratomileusis correction. We introduce a new correction approach, possibly suitable for presbyopic patients previously treated with RK, and we present several potential novel advantages such as enhanced near, intermediate vision, and improvement in quality of life. This is the first report of a bilateral excimer laser treatment attempt of presbyopia following RK.

Past and present of corneal refractive surgery: a retrospective study of long-term results after photorefractive keratectomy and a prospective study of refractive lenticule extraction

Surgical correction of refractive errors is becoming increasingly popular. In the 1990s, the excimer laser revolutionized the field of corneal refractive surgery with PRK and LASIK, and lately refractive lenticule extraction (ReLEx) of intracorneal tissue, using only a femtosecond laser, has become possible. Two new procedures were developed, ReLEx flex (FLEX) and ReLEx smile (SMILE). Until this thesis, only a few long-term studies of PRK with a relatively limited number of patients had been published; therefore, this thesis intended to retrospectively evaluate long-term outcomes after PRK for all degrees of myopia for a large number of patients. Furthermore, a prospective contralateral eye study comparing FLEX and SMILE, when treating high to moderate degrees of myopia, had not been performed prior to this study. This was the second aim of this thesis. In the first study, results from 160 PRK patients (289 eyes) were presented. Preoperative spherical equivalent ranged from -1.25 to -20.25 D, with 78% having low myopia (<-6 D). Average follow-up time was 16 years (range 13-19 years), making this the longest published follow-up study on PRK patients. Outcomes from eyes with low myopia were generally superior to outcomes from eyes with high myopia, at final follow-up. Seventy-two percent were within ± 1.00 D of target refraction, as compared to 47% of eyes with high myopia. However, results from a subgroup of unilateral treated PRK patients indicated that refraction at final follow-up was affected by myopic progression. Fifty percent of eyes with low myopia had uncorrected 20/20 distance visual acuity or better, as compared to 22% of eyes with high myopia. Haze did not occur if attempted corrections were <-4 D, and only eyes with high myopia lost two lines or more of CDVA (corrected distance visual acuity). Eighty-one per cent were satisfied or very satisfied with their surgery.

CONCLUSION

The results support the continued use of the excimer laser for corneal surface ablation as a treatment option for correction of low degrees of myopia, and as the treatment of choice for subgroups of refractive patients (thin corneas, etc.). The results also highlight that treatment of higher degrees of myopia with standard PRK should only be done today under special circumstances, due to low refractive predictability, and high risk of corneal haze. Technological advances since then should be taken into account when comparing these results with contemporary techniques. In the second study, 35 patients were randomized to receive FLEX in one eye and SMILE in the other. Preoperative spherical equivalent refraction ranged from -6 to -10 D with low degrees of astigmatism. A total of 34 patients completed the 6 month follow-up period. Refractive and visual outcomes were very similar for the two methods, as well as tear film measurements and changes in corneal biomechanics. Ninety-seven percent were within ± 1.00 D of target refraction, no eyes lost two lines or more of CDVA, and contrast sensitivity was unaffected after both procedures. The changes in higher-order aberrations were also very similar. There were also no differences in tear film parameters 6 months after surgery, although less postoperative foreign body sensation was reported within the first week after surgery in SMILE eyes. Corneal sublayer pachymetry measurements demonstrated equally increased epithelial thickness 6 months after surgery. Contrary to expectations, it was not possible to measure the theoretical biomechanical advantages of a small corneal incision in SMILE as compared to a corneal flap in FLEX. The main differences between FLEX and SMILE were found when the corneal nerves and intraoperative complications were evaluated. Thus, corneal sensitivity was better preserved and corneal nerve morphology was less affected after SMILE, but intraoperative complications occurred more frequently, although without visual sequela. Finally, 97% were satisfied or very satisfied with both their surgeries.

CONCLUSION

The results support the continued use of both FLEX and SMILE for treatment of up to high degrees of myopia. Overall, refractive and visual results for both procedures were good and similar, but from a biological point of view, the less invasive SMILE technique is more attractive, as demonstrated in this study, despite being slightly more surgically demanding than FLEX.

Laser in-situ keratomileusis for refractive error following radial keratotomy

AIM

To evaluate the safety and efficacy of laser in-situ keratomileusis (LASIK) in eyes with residual/induced refractive error following radial keratotomy (RK).

DESIGN

Retrospective study.

MATERIALS AND METHODS

A retrospective analysis of data of 18 eyes of 10 patients, who had undergone LASIK for refractive error following RK, was performed. All the patients had undergone RK in both eyes at least one year before LASIK. Parameters like uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), contrast sensitivity, glare acuity and corneal parameters were evaluated both preoperatively and postoperatively. STATISTICAL SOFTWARE: STATA-9.0.

RESULTS

The mean UCVA before LASIK was 0.16±0.16 which improved to 0.64 ± 0.22 ( P < 0.001) after one year following LASIK. Fourteen eyes (out of 18) had UCVA of ≥ 20/30 on Snellen's acuity chart at one year following LASIK. The mean BCVA before LASIK was 0.75 ± 0.18. This improved to 0.87 ± 0.16 at one year following LASIK. The mean spherical refractive error at the time of LASIK and at one year after the procedure was -5.37 ± 4.83 diopters (D) and -0.22 ± 1.45D, respectively. Only three eyes had a residual spherical refractive error of ≥ 1.0D at one year follow-up. In two eyes, we noted opening up of the RK incisions. No eye developed epithelial in-growth till 1 year after LASIK.

CONCLUSION

LASIK is effective in treating refractive error following RK. However, it carries the risk of flap-related complications like opening up of the previously placed RK incisions and splitting of the corneal flap.

Irregular astigmatism after cataract surgery resulting from inadequate clear corneal incision formation

A 66-year-old woman was referred to us due to visual complaints after cataract surgery. The patient's complaints were decreased visual acuity and a localized blur in her visual field. At slit lamp biomicroscopy, an unusually long and centrally located clear corneal incision was noted. Corneal topography revealed an irregular astigmatism in the optical axis, originating from the site of the incision. The patient's visual complaints were treated by fitting a rigid gas permeable contact lens, which increased her best corrected visual acuity to 20/16. This case report demonstrated that inadvertently long and centrally located corneal incisions should be avoided during cataract surgery to prevent high levels of irregular astigmatism. RGP contact lenses can lead to successful visual rehabilitation.

PresbyLASIK

Presbyopia represents the most common refractive error. There is currently no surgical treatment for presbyopia, which is effective, reliable, and safe. Excimer laser surgery has become a routine procedure for the correction of myopia, hyperopia, and astigmatism for years. Various treatment strategies for presbyopia have been brought forward using the excimer lasers. Besides monovision, creation of a multifocal cornea represents an attractive option. This procedure is also called "PresbyLASIK." Different ablation profiles to form a multifocal cornea are reviewed here and first clinical results are summarized."PresbyLASIK" is a new, interesting treatment strategy, with a huge potential for the future. At the present it should be used in controlled studies only because of some unsolved questions.

A return to primitive practice? Radial keratotomy revisited

Recently, a refractive surgeon was quoted in the national and professional press as proposing that radial keratotomy (RK) is to be preferred over laser procedures, such as photorefractive keratectomy (PRK) and laser assisted in situ keratomileusis (LASIK). The rationale for this public recommendation was that the RK procedure achieves better visual results and fewer complications than the laser procedures. Peer reviewed literature on these refractive procedures was surveyed to establish the validity of such a statement and it was found that current data do not support the notion that RK results in better visual outcomes than PRK and LASIK The true incidence of complications is difficult to establish. However, when the post procedure chronic effects are compared between RK, PRK and LA SIK, it becomes apparent that the post-RK patient pays the highest price, by a large margin, in visual quality impairment and corneal health. Although the visual acuity outcomes for low to moderate myopes, when corrected by any of the three refractive procedures considered here, are not dramatically different, we concluded that RK is not the preferred methodology because of its associated chronic visual and corneal health complications.

Using the Freiburg Acuity and Contrast Test to measure visual performance in USAF personnel after PRK

PURPOSE

Photorefractive keratectomy (PRK) may be an alternative to spectacle and contact lens wear for United States Air Force (USAF) aircrew and may offer some distinct advantages in operational situations. However, any residual corneal haze or scar formation from PRK could exacerbate the disabling effects of a bright glare source on a complex visual task. The USAF recently completed a longitudinal clinical evaluation of the long-term effects of PRK on visual performance, including the experiment described herein.

METHODS

After baseline data were collected, 20 nonflying active duty USAF personnel underwent PRK. Visual performance was then measured at 6, 12, and 24 months after PRK. Visual acuity (VA) and contrast sensitivity (CS) data were collected by using the Freiburg Acuity and Contrast Test (FrACT), with the subject viewing half of the runs through a polycarbonate windscreen. Experimental runs were completed under 3 glare conditions: no glare source and with either a broadband or a green laser (532-nm) glare annulus (luminance approximately 6090 cd/m) surrounding the Landolt C stimulus.

RESULTS

Systematic effects of PRK on VA relative to baseline were not identified. However, VA was almost 2 full Snellen lines worse with the laser glare source in place versus the broadband glare source. A significant drop-off was observed in CS performance after PRK under conditions of no glare and broadband glare; this was the case both with and without the windscreen. As with VA, laser glare disrupted CS performance significantly and more than broadband glare did.

CONCLUSIONS

PRK does not appear to have affected VA, but the changes in CS might represent a true decline in visual performance. The greater disruptive effects from laser versus broadband glare may be a result of increased masking from coherent spatial noise (speckle) surrounding the laser stimulus.

Flap lift for LASIK retreatment in eyes with myopia

PURPOSE

To analyze the results achieved with LASIK retreatment after lifting the original flap in a large series of patients.

DESIGN

Retrospective, noncomparative, interventional consecutive case series.

PARTICIPANTS

Two thousand four hundred twenty-two consecutive eyes undergoing LASIK surgery for myopia, including 334 eyes submitted to flap lift for LASIK retreatment.

MAIN OUTCOME MEASURES

Uncorrected visual acuity, best-corrected visual acuity, refractive error, and complications.

RESULTS

LASIK retreatment was performed in 334 eyes (14%), and the mean time between initial procedure and retreatment was 8.2+/-6.2 months. The mean spherical equivalent (SE) improved from -1.2+/-0.6 diopters (D) (range, -4.2 to +1.2 D) before retreatment to +0.2+/-0.4 D (range, -3.1 to +1.1 D) after the retreatment. The uncorrected visual acuity (UCVA) after retreatment was 20/20 or better in 58% and 20/40 or better in 92% of eyes. The mean SE was within +/-1.0 D in 96% of the patients and within +/-0.5 D in 80.5% after retreatment. Eighteen eyes (5%) lost 1 line of best-corrected visual acuity, and 4 eyes (1%) lost 2 lines.

CONCLUSIONS

LASIK retreatment surgery performed by relifting the flap was a useful procedure for correcting residual refractive errors after the primary LASIK procedure. It provided good uncorrected visual acuity, predictable results, good refractive stability, and few complications.

Psychometric properties of the National Eye Institute–Refractive Error Quality of Life instrument

OBJECTIVE

To estimate the psychometric properties of a vision-targeted measure of health-related quality of life, the National Eye Institute-Refractive Error Quality of Life survey (NEI-RQL), which includes 13 scales designed to assess the impact of refractive error and its correction on day-to-day life.

DESIGN

Cross-sectional survey.

PARTICIPANTS

The NEI-RQL was self-administered by 667 myopes, 380 hyperopes, and 114 emmetropes recruited from the practices of 6 medical centers. All participants had near and distance visual acuity of 20/32 or better in the worse eye while benefiting from their current method for correction of refractive error (glasses, contact lens, refractive surgery).

METHODS

Mean scores, standard deviations, internal consistency reliability, and test-retest intraclass correlations were estimated for the NEI-RQL scales. Item discrimination was assessed by item-scale correlations. Construct validity was evaluated by assessing the sensitivity of scale scores to type of refractive error, type of refractive error correction, and spherical equivalent. Construct validity of the NEI-RQL was compared to those of the Medical Outcomes Study 36-item short-form health survey (SF-36) and the National Eye Institute Vision Functioning Questionnaire (NEI VFQ-25) in a random subsample of respondents.

MAIN OUTCOME MEASURES

The 13 NEI-RQL scales-clarity of vision, expectations, near vision, far vision, diurnal fluctuations, activity limitations, glare, symptoms, dependence on correction, worry, suboptimal correction, appearance, and satisfaction with correction.

RESULTS

Emmetropes tended to score significantly better on the NEI-RQL scales than myopes and hyperopes. The method of refractive error correction was also associated with NEI-RQL scores. In addition, the NEI-RQL multi-item scales accounted for 29% of the variance in the NEI-RQL satisfaction with correction item beyond that explained by the SF-36 and the NEI VFQ-25.

CONCLUSION

These results support the reliability and construct validity of the NEI-RQL. The instrument appears to be useful for comparisons of people with different types of correction for refractive error.

Responsiveness of the National Eye Institute Refractive Error Quality of Life instrument to surgical correction of refractive error

OBJECTIVE

Refractive error and the means by which it is corrected may impact substantially on quality of vision and health-related quality of life in ways not captured adequately by standard measures of visual acuity. The goal of this analysis was to evaluate the responsiveness of the National Eye Institute Refractive Error Quality of Life (NEI-RQL) instrument to surgical correction of refractive error.

DESIGN

Prospective, multicenter cohort study.

PARTICIPANTS

The NEI-RQL, a 42-item measure with 13 scales, was self-administered by 185 patients before and after undergoing surgical correction of myopic or hyperopic refractive error. Preoperative and postoperative clinical information was collected, including refractive error and corrected visual acuity.

METHODS

Differences between preoperative and postoperative NEI-RQL scores were examined. Responsiveness was assessed using the standardized response mean and the responsiveness statistic. We also compared scales using relative efficiency estimates.

MAIN OUTCOME MEASURES

Changes in NEI-RQL scales (clarity of vision, expectations, near vision, far vision, diurnal fluctuations, activity limitations, glare, symptoms, dependence on correction, worry, suboptimal correction, appearance, and satisfaction with correction).

RESULTS

For myopes and hyperopes combined, refractive surgical correction was associated with statistically significant (P<0.05) improvements in scores for 11 of 13 scales. The largest improvements, ranging from 26 to 58 points on the 0 to 100 possible score range, were seen in expectations, activity limitations, dependence on correction, appearance, and satisfaction with correction. Separate analysis of myopes and hyperopes revealed similar effects in the 2 groups. Baseline scores were found to be predictive of change after surgery.

CONCLUSIONS

The NEI-RQL is responsive to changes in vision-targeted health-related quality of life resulting from keratorefractive surgery. This instrument may prove useful for evaluating the beneficial and adverse impacts of surgical and nonsurgical methods of refractive error correction.

Development of the National Eye Institute refractive error correction quality of life questionnaire

OBJECTIVE

To identify the content area for a questionnaire designed to measure the vision-targeted, health-related quality of life for persons with well-corrected refractive error.

DESIGN

Cross-sectional study.

PARTICIPANTS

Fifty-two focus groups were conducted with 414 patients from 5 geographically diverse ophthalmic and optometric sites to identify the content area of a questionnaire for use among persons with myopia and hyperopia.

METHODS

A standard protocol was used to structure each focus group discussion, and groups were led by centrally trained moderators at each participating site. Results were summarized and analyzed using a standard set of codes. Qualitative and quantitative analyses were conducted.

MAIN OUTCOME MEASURE

Self-reported observations or comments about vision, vision correction, and other aspects of quality of life.

RESULTS

Among the 414 participants, 9262 mentions of comments were recorded. The most frequent comments reported by participants were about types of vision correction, followed by comments with their own vision and vision-related symptoms. The distribution of comments by topic domain was generally similar across types of correction and type of refractive error. The most frequent specific comments about glasses concerned problems with reading, adjustment between near and far vision, and appearance. The most frequent comments about contact lenses included those on symptoms such as dry eyes, itching and tired eyes, and headaches, and negative comments about ease of use. The most frequent comments among patients with surgical correction concerned fewer driving problems; fewer symptoms; and improvement in vision, recreation, and comfort. Participants provided equal numbers of positive and negative comments about glasses. Twice as many positive as negative comments were given by contact lens wearers, and 4 times as many positive comments were provided by patients who had undergone surgical correction.

CONCLUSIONS

Using focus groups, we were able to identify content areas and aspects of visual functioning in persons with refractive error that are not measured by standard visual acuity testing in the clinic or by other vision-targeted, health-related quality of life instruments such as the 25- or 51-item National Eye Institute-Visual Functioning Questionnaire. The similarity of problems mentioned across refractive error type and correction method suggests it will be possible to develop a single questionnaire with adequate content validity to compare the impact of different modes of correction in vision-targeted, health-related quality of life.

Correlation of visual and refractive outcomes between eyes after same-session bilateral laser in situ keratomileusis surgery

PURPOSE

To determine whether between-eye refractive and visual outcomes after same-session laser in situ keratomileusis (LASIK) surgery are correlated, and to determine whether suboptimal visual and refractive outcomes in one eye are predictive of poor results in the fellow eye.

DESIGN

Observational case series.

METHODS

Retrospective chart review. A total of 484 eyes of 242 patients met inclusion criteria of having undergone same-day LASIK surgery and having 3-month refractive and visual acuity outcomes. Statistical comparisons of outcomes were performed, including between-eye Pearson correlation analysis and logistic regression models for predicting second-eye outcome. Main outcome measures were 1-month, 3-month, and 6-month uncorrected visual acuity and manifest refraction.

RESULTS

Refractive outcomes at 1, 3, and 6 months between first (right) and second eyes were not found to be significantly different. No difference in uncorrected or best spectacle-corrected visual acuity was observed between first and second eyes Refractive outcomes of spherical equivalent, sphere, and cylinder and visual outcomes of uncorrected and best spectacle-corrected visual acuity were highly correlated between the two eyes. Analysis of cases with suboptimal outcomes (> or =1 diopter from intended correction or uncorrected acuity equal to or worse than 20/40) suggests that a poor refractive or visual outcome in the first eye increases the risk of a poor outcome in the second eye by approximately 20-fold.

CONCLUSIONS

Retrospective analysis of refractive and visual outcomes from patients undergoing same-session bilateral LASIK demonstrates a high correlation of refractive and visual outcome between the eyes.

Incisional refractive surgery

The use of incisional refractive surgery has become limited due to the widespread use of the excimer laser to correct myopia, hyperopia and astigmatism. Laser in situ keratomileusis and photorefractive keratectomy have proven to be much more accurate and predictable in correcting refractive error. This has made some forms of incisional refractive surgery practically obsolete. Radial keratotomy should not be considered a primary refractive procedure in the modern world, as RK has become "RKhaic". There are still indications for incisional refractive surgery in cataract and post-surgical patients for the treatment of astigmatism. However, with the advent of the toric intraocular lens and the use of LASIK in such aforementioned patients, these indications for incisional surgery will likely become more limited. In this review, we go over the past history of incisional refractive surgery and also report the current uses and advancements of this technique in today's practice environment.

Prospective Randomized Study of Corneal Aberrations 1 Year After Radial Keratotomy or Photorefractive Keratectomy

PURPOSE

To evaluate the optical properties of the cornea 1 year after either radial keratotomy (RK) or photorefractive keratectomy (PRK) in a randomized group of patients with low myopia.

METHODS

Ninety-six patients with myopia between -0.75 and -5.00 D were randomized to either radial keratotomy (n = 46) or photorefractive keratectomy (n = 50). Topography maps were obtained 1 year after surgery and analyzed by computation of total corneal wavefront aberration and Zernike polynomial coefficients for pupil sizes of 2, 4, and 6 mm. The 4-mm pupil size was used for optimization of the model.

RESULTS

The total corneal wavefront aberrations after RK and PRK were similar and not statistically different. Wavefront aberrations arising from astigmatism or defocus accounted for approximately 70% of the total wavefront error at all pupil sizes in both groups. All types of aberrations, and in particular spherical aberration, increased significantly with increasing pupil size. Higher-order wavefront aberrations were almost twice as high after RK than after PRK at pupil sizes of 4 and 6 mm. Spherical aberration and coma were slightly higher after PRK than after RK.

CONCLUSIONS

Pupil size had a major effect on corneal aberrations after RK and PRK. The most important aberrations were sphero-cylindrical, in which eyes became significantly more myopic with increasing pupil size. The image forming properties of the cornea are better after PRK compared with RK due to the lesser amount of higher-order aberrations.

Epithelial plugs in radial keratotomy: the origin of incisional keratitis?

PURPOSE

Incisions in radial keratotomy (RK) patients were examined histopathologically to explore the cause of delayed infections occurring following this procedure.

METHODS

Four corneas from two successful RK patients were obtained postmortem and 1 cornea from an unsuccessful RK was collected following lamellar keratoplasty. The tissue was prepared for light and transmission electron microscopy.

RESULTS

All incisions examined contained an epithelial plug. The average depth of the plugs for left and right corneas in the 2 successful cases were 142.58 microm (range: 36.46-183.04 microm) and 58.44 microm (range: 29.27-115.66 microm), whereas the unsuccessful case these measurements were 121.06 microm (range: 70.03-172.01 microm). In the successful cases, the plugs were on average 4.2 cells deep (range: 2-5) in one case and for the other the plugs were 8.78 cells deep (range: 1.5-11.5) and 2.72 cells wide (range: 2-4). In the unsuccessful case the plugs were on average 6.89 cells deep (range: 5-11) and 8.56 cells wide (range: 4-13). The average epithelial thickness, measured 200 microm on either side away from the plug, was 47.11 microm and 55.09 microm for the successful cases, and 27.52 microm for the unsuccessful case. Degenerate cells were often observed within the plug and along the overlying surface. Lamellae cut during surgery remained severed in all corneas observed. The stroma adjacent to the incision contained an elevated number of stromal cells (8%-78%).

CONCLUSIONS

Healing did not include repair of anterior limiting lamina or stromal lamellae, which all remained severed in all incisions observed. Epithelial plugs were invariably present in all incisions regardless of clinical outcome, thus, increasing the distance a basal cell travels to reach the epithelial surface by 2 to 4 times. Since the epithelial cell has a limited life, it is hypothesized that cells originating in the plug may die before reaching the surface, thus, leading to intermittent loss of surface integrity. The loss of the epithelial barrier allows invasion of microorganisms and the delayed onset of keratitis. The larger the plug the greater the possibility of surface defects and resultant infection.

Minimizing radial-keratotomy-induced diurnal variation in vision using contact lenses

A 41-year-old man with 16 radial keratotomy (RK) incisions in each eye reported a paradoxical diurnal variation in vision in both eyes with low Dk/L soft contact lenses. After rk, the patient experienced the conventional diurnal change a morning-to-evening mean (right and left eyes) myopic change of -1.80 diopters (D). However, while wearing low Dk/L contact lenses, a paradoxical morning-to-evening mean hyperopic change of 2.30 D was found. The diurnal variation was minimized (0.50 D) by wearing high Dk/L contact lenses. These results suggest that contact lenses can be used to treat diurnal variation in manifest refraction after RK by inducing appropriate stress.

Laser in situ keratomileusis to correct residual myopia and astigmatism after radial keratotomy

PURPOSE

To evaluate the safety and efficacy of laser in situ keratomileusis (LASIK) in selected post-radial-keratotomy (RK) eyes with residual myopia and astigmatism.

SETTING

TLC-The Brea Laser Eye Center, Brea, California, USA.

METHODS

Nine eyes of 6 patients who had had RK but had residual myopia and/or astigmatism had LASIK. All RK eyes had 8 radial incisions, were more than 1 year post-RK, had no epithelial inclusion cysts or corneal disease, and had had no subsequent ocular surgery. Follow-up was a minimum of 13 months, at which time uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), manifest refraction, cycloplegic refraction, keratometry, central and peripheral pachymetries, intraocular pressure, and a subjective assessment of visual function were obtained.

RESULTS

At the last follow-up, the mean spherical equivalent (SE) was -0.156 diopter (D) +/- 0.174 (SD). All eyes treated for distance vision had a UCVA of 20/25 or better. No patient lost BCVA. No intraoperative or postoperative complications occurred. Seven eyes had morning and evening measurements. The mean change in manifest SE from morning to evening was -0.143 D. Six of the 7 eyes (86%) had 0 to 1 Snellen line change in UCVA from morning to evening. The subjective questionnaire revealed a high degree of satisfaction with overall vision, minimal glare, and less fluctuation in daily vision than before LASIK.

CONCLUSION

Laser in situ keratomileusis is safe and efficacious for reducing residual myopia and astigmatism in properly selected RK patients.

Understanding corneal topography

With the increase in corneal laser refractive surgery, there is a greater need for precise evaluation of the corneal surface. Articles published in the past year have reported possible use of confocal scanning laser technology-based devices to image the cornea. Other studies have compared existing instruments and software in an effort to determine if data from different instruments are comparable. Topographic evaluation also has served to highlight long-term complications of procedures like radial keratotomy and the promise of newer surgical procedures like the intrastromal corneal ring segments. Studies of the corneal surface have helped refine surgical procedures like photorefractive keratectomy, laser in situ keratomileusis, penetrating keratoplasty, and cataract surgery. Topographic measures that serve as direct correlates of ocular visual performance, however, still remain elusive. Studies in the past year have confirmed that corneal topographic evaluation may be a powerful tool in the search for a genetic basis of keratoconus. Important areas for future research include precise determination of the power of the postrefractive surgery cornea to allow precise estimation of intraocular lens power in these eyes. Detecting the presence of past corneal refractive surgery in donor eyes also is likely to be a challenge. Despite the numerous advances in the field of corneal topography in the past year, there is still a need to present the data in a standardized format that is universal to all instruments and technologies.

Diurnal stability of refraction after implantation with intracorneal ring segments

PURPOSE

To investigate diurnal changes in visual acuity and refraction in myopic eyes implanted with intracorneal ring segments (ICRS).

SETTING

University of California San Diego Shiley Eye Center, La Jolla, California, and Emory University Vision Correction Center, Atlanta, Georgia, USA.

METHODS

This prospective study involved 2 groups of patients who had ICRS (Intacs) implantation and a follow-up of at least 6 months. The first group included 102 eyes of 51 bilaterally treated patients; the second group, 32 eyes of 16 unilaterally treated patients. Examinations including visual acuity, manifest refraction, and videokeratography were done in the morning and evening at least 9 hours apart on a single day. Refractive changes were analyzed by power vectors; multivariate statistics were used to determine the significance of change in any component of the spectacle prescription.

RESULTS

In the bilateral treatment group, 97 eyes (95%) were within 1 line of spectacle-corrected visual acuity from morning to evening. The mean change in manifest refraction was -0.14 +0.08 x 4 and in spherical equivalent, -0.10 diopters (D) (sigma = 0.3; range -0.750 to +0.875 D). Ninety-six eyes (94%) had a change in refraction within 0.50 D of spherical equivalent. There was no significant change in corneal power (P =.20). In the unilateral treatment group, there was no significant difference between treated and untreated eyes in changes in spectacle-corrected visual acuity, manifest refraction, or corneal power and toricity (P.05).

CONCLUSION

No clinically significant diurnal variation in visual acuity or manifest refraction was observed after ICRS implantation or in untreated paired eyes. Moreover, the data suggest less diurnal change in visual acuity and refraction after ICRS implantation.

Use of reverse geometry rigid gas permeable contact lenses in the management of the postradial keratotomy patient: review and case report

Radial keratotomy (RK) is a well-known procedure for reducing myopia. However, the complications associated with the procedure and the development of newer technologies, such as photorefractive keratectomy and laser-assisted in situ keratomileusis, has resulted in the technique of RK falling out of favor. A number of patients who received RK during the 1980s are now experiencing a shift in their prescription and are presenting to primary care practitioners for contact lens fitting. These patients pose a significant challenge to the contact lens practitioner, and novel methods frequently are required to fit corneas that exhibit such abnormal topography. This article reviews the potential problems associated with fitting patients who have received RK and describes a case in which a novel lens design was used to achieve a successful lens fit.

Diurnal fluctuations in corneal topography 10 years after radial keratotomy in the Prospective Evaluation of Radial Keratotomy Study

PURPOSE

To correlate clinically observed fluctuations in manifest refraction, visual acuity, keratometry, and intraocular pressure (IOP) with changes in the anterior corneal surface as measured by videokeratography in patients 10 years after radial keratotomy (RK).

SETTING

Four clinical centers in the United States that participated in the Prospective Evaluation of Radial Keratotomy (PERK) study.

METHODS

Thirty-two eyes of 20 PERK patients who noted diurnal fluctuations in vision had clinical examination and videokeratography (TMS-1, Computed Anatomy Inc.) in the morning and evening of the same day a mean of 10.3 years (range 7.8 to 11.7 years) after RK. The videokeratographs were analyzed in terms of various indexes generated by custom-designed software. Morning-to-evening changes in the means of the various clinical and videokeratographic values were assessed using pairwise methods.

RESULTS

The mean increase in myopia was 0.36 diopters (D) +/- 0.58 (SD) from morning to evening (P < .01). Analysis of the videokeratographs showed a corresponding increase in average corneal power (ACP), reflecting a steepening of 0.52 +/- 0.45 D (P < .001). The change in ACP was correlated with a change in the manifest spherical equivalent refraction (R = 0.39, P = .03) and a change in best spectacle-corrected visual acuity (R = 0.38, P = .03) over the same period. Similarly, simulated keratometry (SimK) readings correlated with the change in the manifest spherical equivalent refraction (R = 0.38, P = .03 for SimK1; R = 0.37, P = .35 for SimK2; R = 0.4, P = .02 for average SimK), although the standard clinical keratometric data did not (P = .26 for K1, P = .11 for K2, and P = .09 for the mean K). The elevation depression magnitude, a measure of the low-frequency irregularities of the cornea, showed a decrease of 0.32 +/- 1.59, which also correlated with the change in the manifest spherical equivalent refraction (R = 0.37, P = .04). Intraocular pressure tended to decrease from morning to evening (mean change of -0.97 +/- 3.29 mm Hg), but the difference was not significant. Variations in IOP in individual patients, however, were correlated with changes in the manifest spherical equivalent refraction (R = 0.37, P = .04).

CONCLUSIONS

Diurnal fluctuations in corneal topographic indexes can be used to evaluate the diurnal fluctuations in refraction and visual acuity after RK. The study findings provide statistical support for the idea that IOP contributes to the diurnal fluctuation in visual acuity after RK.

Surgical correction of moderate myopia: which method should you choose? I. Radial keratotomy will always have a place

This set of "Viewpoints" articles examines the relative merits of radial keratotomy (RK), photorefractive keratectomy (PRK), and laser assisted in-situ keratomileusis (LASIK). Drs. Rowsey and Morley review advances in RK techniques, long-term results, and complications, and explain why RK will remain a viable method for correction of moderate myopia, notably its minimal cost. Drs. Steinert and Bafna review both PRK and LASIK, discussing techniques and results and comparing their advantages and disadvantages with each other and with RK. Dr. Dutton, as "Viewpoints" section editor, summarizes clinical, technologic, and economic aspects of all three techniques, concluding that all will find a place among refractive surgeons for some time to come.

Unilateral Refractive Keratotomy for Anisometropia

BACKGROUND

In anisometropia, the asymmetry of refractive error produces disparity of image magnification (aniseikonia) that can create visual discomfort, especially when asymmetry is 3.00 diopters or more.

METHODS

A prospective study of 20 eyes of 20 patients between 18 and 61 years of age who underwent unilateral radial and/or transverse keratotomy was conducted; results of at least 12 months follow-up are presented. The efficacy of keratotomy was evaluated by the following criteria: 1) change in spherical and cylindrical refraction, 2) decrease in refraction difference between two eyes of each patient, 3) change in spectacle-corrected visual acuity, and 4) change in binocular vision functions and asthenopic complaints.

RESULTS

Mean decrease in spherical refractive error was 3.66 +/- 1.58 D (range, 1.25 to 7.50 D) and 2.08 +/- 0.81 D (range, 1.00 to 3.50 D) in astigmatic refraction. The mean refraction difference between two eyes was 4.90 +/- 2.20 D preoperatively, and this difference regressed to 1.79 +/- 1.42 D postoperatively. Spectacle-corrected visual acuity increased in seven eyes (35%), remained the same in 12 eyes (60%) and decreased in one eye (5%). All patients reported relief of asthenopic complaints. Fusion amplitudes increased in 12 (60%) patients. Stereoscopic vision improved in five (25%) patients.

CONCLUSION

Monocular refractive keratotomy can significantly decrease anisometropia.

Photorefractive keratectomy. A 6-year follow-up study

OBJECTIVE

This study aimed to assess the long-term stability and efficacy of excimer laser photorefractive keratectomy.

DESIGN

Patients who participated in the first United Kingdom photorefractive keratectomy clinical trial were asked to attend a 6-year follow-up assessment.

PARTICIPANTS

Eighty-three patients (68%) of the original cohort of 120 participants were observed for 6 years. A Summit Technology UV200 excimer laser with a 4-mm ablation zone had been used with patients allocated to one of six groups according to their preoperative refraction. Each group received one of the following spherical corrections: -2, -3, -4, -5, -6, or -7 diopters (D). Within each group, all patients received an identical treatment, and thus emmetropia was not the goal in all patients.

INTERVENTION

The induced refractive change, objective corneal haze, glare, and halo measurements, together with possible late-phase complications, were analyzed.

MAIN OUTCOME MEASURES

All groups achieved a refractive undercorrection, and the magnitude of the undercorrection was related to the size of the attempted correction. The induced refraction stabilized by 6 to 12 months and has been maintained up to the 6-year follow-up stage.

RESULTS

Ninety-one percent of patients who underwent a -2.00-D correction and 76% of patients who received a -3.00-D correction were within +/- 1 D of the intended refraction at 6 years. Fifty-seven percent of the -4.00-D group and 50% of those in the -5.00-D group were within +/- 1 D, and this was reduced further to 43% in the -6.00-D group and 19% in the -7.00-D group. Six patients (7%) had evidence of residual corneal haze, which was visually significant in two patients (3%). Ten patients (12%) had significant night halos due to the small 4-mm ablation zone that was used in this early treatment trial.

CONCLUSIONS

There was no further regression of the refraction after 1 year, and, more important, there was no sign of hyperopic shift or diurnal fluctuation in the patients' refraction. In addition, corneal haze appeared to reduce further with time, with no intraocular or retinal side effects being noted. Night halos remain a significant reported problem in a small number of patients who were treated with the 4-mm ablation zone.