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Biomedical subjects

R K Maloney

Publications and source records attributed to R K Maloney.

At least 19 recordsLinked to original sources
PubMed2001

Effect of varying the optical zone diameter on the results of hyperopic laser in situ keratomileusis.

PURPOSE: To compare the predictability and safety of laser in situ keratomileusis (LASIK) for low to moderate spherical hyperopia using different ablation zone diameters. DESIGN: Retrospective, nonrandomized, comparative trial. PARTICIPANTS: Forty-nine eyes that underwent hyperopic LASIK. INTERVENTION: Two surgeons (JMD, RKM) performed hyperopic LASIK using the VISX STAR S2 excimer laser (VISX, Inc., Sunnyvale, CA) and the Bausch & Lomb Hansatome microkeratome (Chiron Vision, Irvine, CA) using ablation zone diameters of 5 x 9 mm, 5.5 x 8.5 mm, or 6 x 9 mm (the first number represents the optical zone diameter and the second number represents the diameter of the outer border of the ablation zone). MAIN OUTCOME MEASURES: Refractive and visual outcomes at 3 to 6 months after surgery were analyzed. Groups were compared for deviations from targeted spherical equivalent, uncorrected visual acuity, and loss of best spectacle-corrected visual acuity (BSCVA). RESULTS: The mean intended hyperopic correction was +2.48 +/- 1.13 diopters (D; 0.63-5.50 D). There were 16 eyes in the 5 x 9-mm group, 15 eyes in the 5.5 x 8.5-mm group, and 18 eyes in the 6 x 9-mm group. On average, the 5 x 9-mm group achieved 97% of the programmed correction, the 5.5 x 8.5-mm group achieved 104%, and the 6 x 9-mm group achieved 112% of the programmed correction. The tendency toward overcorrection in the 6 x 9-mm group compared with the 5 x 9-mm group was statistically significant (P < 0.05). The incidence of one line loss of BSCVA was greatest in the 5 x 9-mm group (19%) and lowest in the 6 x 9-mm group (6%). These differences were not statistically significant. No eyes experienced a loss of two or more lines of BSCVA at last examination. CONCLUSIONS: Hyperopic LASIK using the VISX STAR is safe and effective using different ablation zone diameters. There appears to be an increased tendency toward overcorrection with progressively larger optical zone diameters.

Adult↗
PubMed2001

Symptoms of dry eye and recurrent erosion syndrome after refractive surgery.

PURPOSE: To determine the incidence and severity of patient complaints typical of dry eye and recurrent erosion syndrome after excimer laser refractive surgery and to compare the incidence of these symptoms after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). SETTING: Outpatient university practice. METHODS: A questionnaire was mailed to 1731 patients who had had primary myopic PRK or LASIK at least 6 months previously. Questions were designed to determine the incidence and character of ocular dryness and recurrent erosion symptoms and their impact on patient satisfaction and willingness to have surgery again. Responses from PRK and LASIK patients were compared. RESULTS: Responses from 231 PRK patients and 550 LASIK patients revealed an incidence of dryness symptoms in 43% and 48%, respectively (P >.05). Soreness of the eye to touch was reported by 26.8% and 6.7%, respectively (P <.0001). Sharp pains occurred in 20.4% of PRK patients and 8.0% of LASIK patients (P =.0001). Complaints of the eyelid sticking to the eyeball occurred in 14.7% and 5.6%, respectively (P =.0001). All symptoms occurred predominantly on waking. Frequency of eyelid sticking (P <.0005) and sharp pain (P <.005) symptoms, as well as severity of sharp pain symptoms (P <.0001), were significantly greater in PRK patients than in LASIK patients. On a scale of 0 to 10 (10 high), median overall patient satisfaction with surgery was 9 in both groups. Soreness of the eyelid to touch occurred significantly more frequently among patients with symptoms of sharp pains on waking (P <.001) and the sensation of the eyelid sticking to the eyeball (P <.001). Patients with 1 or more symptoms were twice as likely as asymptomatic patients to have a satisfaction score of less than 8 (P <.001). CONCLUSIONS: Ocular dryness symptoms occurred commonly after PRK and LASIK. Symptoms suggestive of mild recurrent erosions included sharp pains, the sensation of the eyelid sticking to the eyeball, and soreness of the eyelid to touch, a previously unrecognized symptom of this condition. These symptoms occurred commonly after excimer laser procedures but were significantly more common, more severe, and more prolonged after PRK. The presence of these symptoms had a significant effect on patient satisfaction.

Corneal Diseases↗
PubMed2001

Conductive keratoplasty for the correction of hyperopia.

BACKGROUND/PURPOSE: Conductive keratoplasty (CK) is a surgical technique that delivers radio frequency (350 kHz) current directly into the corneal stroma through a Keratoplasty tip inserted into the peripheral cornea at 8 to 32 treatment points. A full circle of CK spots produces a cinching effect that increases the curvature of the central cornea, thereby decreasing hyperopia. We report here the 12-month results of a 2-year, prospective, multicenter US clinical trial conducted to evaluate the efficacy, safety, and stability of CK. METHODS: A total of 233 patients (401 eyes) with preoperative hyperopia of +0.75 to +3.00 D and < or = 0.75 D of astigmatism (mean preoperative manifest refractive spherical equivalent = +1.76 D +/- 0.60) were enrolled into the study at 13 centers and underwent CK treatment. RESULTS: Twelve-month postoperative data are available on 203 eyes for safety and stability and 171 eyes for safety, stability, and efficacy. A total of 91% had uncorrected visual acuity (UCVA) of 20/40 or better, and 51% had UCVA of 20/20 or better. Manifest refractive spherical equivalent was within +/- 0.50 D in 58%, within +/- 1.00 D in 91%, and within +/- 2.00 D in 99%. The mean change in residual refraction was 0.26 D +/- 0.49 between 3 and 6 months, 0.09 D +/- 0.37 between 6 and 9 months, and 0.13 D +/- 0.39 between 9 and 12 months. CONCLUSIONS: One-year data show safety and efficacy of CK in the treatment of hyperopia. Changes in residual refractive error after CK appeared to be small, suggesting that a stable refraction could be achieved by 6 months.

Adult↗
PubMed2000

Epithelial ingrowth after laser in situ keratomileusis.

PURPOSE: To report the incidence and risk factors for clinically significant epithelial ingrowth after laser in situ keratomileusis as well as the recurrence rate and visual outcomes after its treatment. METHODS: We defined clinically significant epithelial ingrowth as that which required surgical removal. From a cohort of 3, 786 eyes that underwent primary laser in situ keratomileusis from February 1996 to August 1998 and its derivative of 480 eyes that later underwent enhancement laser in situ keratomileusis by one surgeon (R.K.M.), we identified all eyes with clinically significant epithelial ingrowth. RESULTS: The incidence of significant epithelial ingrowth after primary treatment was 35 (0.92%) of 3,786 eyes. The incidence after enhancement treatment was eight (1.7%) of 480 eyes (p = NS). Fourteen of 43 eyes had a postoperative epithelial defect associated with subsequent development of epithelial ingrowth. Six of 43 eyes had loose epithelium intraoperatively, suggesting epithelial basement membrane dystrophy. Epithelial ingrowth was treated by lifting the flap, scraping the bed and the posterior surface of the flap, and replacing the flap without the use of caustic agents. In 42 of 43 eyes, the epithelial ingrowth under the flap was continuous with the surface epithelium. Clinically significant ingrowth recurred in 10 of 43 eyes after the initial surgical removal. CONCLUSIONS: Clinically significant epithelial ingrowth is an infrequent complication of laser in situ keratomileusis. We hypothesize that epithelial ingrowth is secondary to postoperative invasion under the flap by surface epithelial cells rather than intraoperative implantation of epithelial cells. Treatment should consist of complete mechanical removal of epithelium from the posterior surface of the corneal flap and keratectomy bed and ensuring tight apposition of the flap with the bed.

Corneal Diseases↗
PubMed2000

Quantitative topographic irregularity as a predictor of spectacle-corrected visual acuity after refractive surgery.

PURPOSE: To evaluate a new topographic index called topographic irregularity as a quantitative predictor of corrected vision after refractive surgery. METHODS: We defined topographic irregularity as the summed difference at all points between a topographic refractive corneal power map and its best-fit spherocylinder. We prospectively studied 107 eyes of 107 patients 3 months after a variety of refractive procedures. Topographic irregularity was calculated from topographic maps, and the correlation between topographic irregularity and spectacle-corrected visual acuity was determined using both high-contrast and low-contrast acuity charts. This correlation was compared with correlations for the surface regularity index and the surface asymmetry index. Next, we analyzed 54 of these topographic maps to create a regression scale relating surface regularity index, surface asymmetry index, and topographic irregularity to predict spectacle-corrected visual acuity. This scale was then used to predict spectacle-corrected visual acuity on the remaining 53 postoperative patients. RESULTS: The correlation of topographic irregularity with spectacle-corrected visual acuity (R(2) =.36) was comparable to the correlation for the surface regularity index (R(2) =.36) and stronger than for the surface asymmetry index (R(2) =.11) when spectacle-corrected visual acuity was measured with high-contrast eye charts. Topographic irregularity correlated more strongly with spectacle-corrected visual acuity (R(2) =.42) than either the surface regularity index (R(2) =.28) or the surface asymmetry index (R(2) =.14) when spectacle-corrected visual acuity was measured with low-contrast eye charts. Using the regression scale, prediction of high-contrast and low-contrast spectacle-corrected visual acuity from topographic irregularity was superior to or comparable to predictions using the surface regularity index and the surface asymmetry index. CONCLUSIONS: Topographic irregularity has a closer correlation with spectacle-corrected visual acuity than existing topographic indexes. Topographic irregularity is also an accurate predictor of spectacle-corrected visual acuity and may be a more sensitive tool for evaluating postoperative visual performance than current topographic measures.

Cornea↗
PubMed2000

Microkeratome complications of laser in situ keratomileusis.

PURPOSE: To evaluate the incidence, types, and outcome of microkeratome complications that occur during laser in situ keratomileusis (LASIK). DESIGN: Retrospective, noncomparative, case series. PARTICIPANTS: Three thousand nine hundred ninety-eight eyes that underwent primary LASIK by four surgeons between November 1996 and August 1998 at a university-based refractive center. METHODS: All cases with significant microkeratome complications leading to abandonment of the LASIK procedure were identified and reviewed. MAIN OUTCOME MEASURES: Incidence of complications, change in best corrected visual acuity (BCVA), change in refractive error, and types of complication. RESULTS: There were 27 complications leading to abandonment of the LASIK procedure of 3998 eyes. The overall rate of microkeratome complication was 1 in 150 (0.68%), but it was 1 in 77 (1.3%) in the surgeons' first 1000 eyes, decreasing to 1 in 250 (0.4%) in the last 1000 eyes. Of the 24 planned bilateral cases, 15 complications (63%) happened on the first operated eye. Twenty-six of 27 eyes (96%) recovered to within one line of preoperative BCVA, and one eye lost two lines. At last examination before any repeat refractive procedures, spherical equivalent manifest refraction returned to within 1 diopter (D) of its preoperative value in 18 of 19 eyes (95%), and astigmatism in 16 of 19 eyes (84%) returned to within 1 D of its preoperative value. Sixteen of 27 eyes (59%) had repeat LASIK. Two eyes had complications at repeat LASIK, one of which led to abandonment of the LASIK procedure for a second time. CONCLUSIONS: There is a significant learning curve in the use of the microkeratome. If ablation is not performed, flap complications rarely lead to significant visual loss and generally do not result in a change in refractive error.

Clinical Competence↗
PubMed1999

Deep lamellar keratoplasty using viscoelastic dissection.

We describe a technique for performing deep lamellar keratoplasty using viscoelastic dissection. Deep lamellar dissections of the cornea using viscoelastic substances (sodium hyaluronate) were performed on 4 eyes of 4 patients. One patient with keratoconus and another with corneal scarring underwent lamellar keratoplasty using the technique as the sole procedure for visual rehabilitation. Two patients (2 eyes) with opaque corneas underwent deep lamellar dissection with removal of stromal tissue to allow visualization of the anterior segment structures prior to penetrating keratoplasty, thereby facilitating separation of iridocorneal adhesions as the Descemet membrane was incised. Deep lamellar dissection was performed without complications related to the procedure in all 4 eyes. The 2 lamellar grafts cleared completely, and both eyes achieved excellent visual acuity with spectacle correction. In the other 2 eyes, deep lamellar dissection provided clear visualization of anterior segment structures during incision of the Descemet membrane. Deep lamellar dissection using viscoelastic substances is a useful technique during lamellar keratoplasty.

Aged↗
PubMed1999

Flap complications associated with lamellar refractive surgery.

PURPOSE: Corneal lamellar refractive surgery for myopia reduces the risk of corneal haze but adds to the risk of flap complications. We retrospectively determined the incidence of flap complications in the initial series of eyes undergoing lamellar refractive surgery by one surgeon. We assessed the incidence of flap complications overall, the trend in these complications during the surgeon's learning curve, and the impact of the complications on best spectacle-corrected visual acuity. METHODS: Charts of the first 1,019 eyes that underwent myopic keratomileusis in situ or laser in situ keratomileusis were reviewed for flap complications and visual outcome. RESULTS: Of the 1,019 eyes, 490 eyes underwent myopic keratomileusis in situ, and 529 eyes underwent laser in situ keratomileusis. Eighty-eight (8.6%) of 1,019 eyes had flap-related complications. Six eyes had two complications. Intraoperative complications included irregular keratectomy in nine eyes (0.9%), incomplete keratectomy in three eyes (0.3%), and a free cap in 10 eyes (1.0%). The incidence of intraoperative complications was six (6.0%) in the first 100 consecutive eyes, 14 (2.3%) in the next 600 consecutive eyes (P = .04, chi-square test), and one (0.3%) in the last 300 eyes (P = .03, chi-square test). Postoperative complications included displaced flaps that required repositioning in 20 eyes (2.0%), folds in the flap that required repositioning in 11 eyes (1.1%), diffuse lamellar keratitis in 18 eyes (1.8%), infectious keratitis in one eye (0.1%), and epithelial ingrowth that required removal in 22 eyes (2.2%). The incidence of flap displacement and folds in 200 eyes in which we irrigated under the flap and allowed it to settle without further manipulation averaged 8.5%, whereas the incidence in other groups of 100 consecutive eyes averaged 0.8% (P < .00001, chi-square test). The incidence of diffuse lamellar keratitis was 0.2% in eyes that had undergone myopic keratomileusis in situ and 3.2% in eyes treated by laser in situ keratomileusis (P = .0003, chi-square test). No eye lost 2 or more lines of best spectacle-corrected visual acuity because of flap complications. CONCLUSION: Flap complications after lamellar refractive surgery are relatively common but rarely lead to a permanent decrease in visual acuity. Physician experience with the microkeratome and with the handling of the corneal flap decreases the incidence of flap complications.

Cornea↗
PubMed1999

Effect of astigmatic keratotomy on spherical equivalent: results of the Astigmatism Reduction Clinical Trial.

PURPOSE: To determine the effect of astigmatic keratotomy on spherical equivalent, as measured by the coupling ratio and a new quantity, coupling constant. METHODS: In a prospective multicenter study, subjects underwent arcuate keratotomy at a 7-mm optical zone by means of the Lindstrom nomogram for correction of astigmatism. One hundred fifty-seven eyes of 95 patients who had a follow-up examination 1 month postoperatively were studied. Mean preoperative refractive cylinder +/- SEM was 2.82 +/- 1.17 diopters. Coupling ratio was defined as the ratio of the flattening of the incised meridian to the steepening of the opposite meridian. Coupling constant was defined as the ratio of the change in spherical equivalent to the magnitude of the vector change in astigmatism. Coupling ratio, coupling constant, and change in spherical equivalent were calculated on the basis of change in refraction and keratometry. RESULTS: On the basis of change in refraction, coupling ratio was 0.95 +/- 0.10 (mean +/- SEM) and coupling constant was -0.01 +/- 0.03, consistent with a minor shift in the spherical equivalent of -0.03 +/- 0.07 diopter. On the basis of change in keratometry, coupling ratio was 0.84 +/- 0.05 and coupling constant was -0.04 +/- 0.02, consistent with minor postoperative keratometric steepening of -0.10 +/- 0.04 diopter. Coupling ratio based on change in refraction was not statistically different from the coupling ratio predicted by the Gauss' law for inelastic domes (P = .370). Incision length and number, amount of achieved cylinder correction, age, and sex had no statistically significant effect on coupling ratio, coupling constant, and change in spherical equivalent. CONCLUSIONS: Cornea behaved as an inelastic surface in response to arcuate keratotomy performed with the Astigmatism Reduction Clinical Trial study nomogram. On average, astigmatic keratotomy had a minimal effect on spherical equivalent refraction. There was variability, however, in coupling ratio, coupling constant, and change in spherical equivalent from eye to eye after astigmatic keratotomy. Caution is therefore advised when simultaneous correction of cylinder and spherical equivalent is planned.

Adolescent↗
PubMed1999

Visual performance after photorefractive keratectomy with a 6-mm ablation zone.

PURPOSE: To prospectively examine the effect of photorefractive keratectomy with a 6-mm ablation zone on best-spectacle-corrected visual performance. METHODS: A prospective study was conducted of 164 eyes of 164 patients with an average (+/-SD) of -4.02 +/- 1.74 diopters (range, -0.63 to -8.38 diopters spherical equivalent). Best-spectacle-corrected high-contrast and low-contrast visual acuity (18% Weber contrast) was measured with both natural and dilated pupils. Patients were tested preoperatively and at 3, 6, and 12 months after photorefractive keratectomy. Photorefractive keratectomy was performed with an argon fluoride excimer laser. Fifty-five eyes of 55 patients also underwent astigmatic keratotomy. RESULTS: Twelve months after photorefractive keratectomy, best-spectacle-corrected high-contrast visual acuity with natural pupils showed no significant change from preoperative values; mean (+/-SD) change was 0.004 +/- 0.10 logMAR (t = 0.45, P = .65). Best-spectacle-corrected low-contrast visual acuity with natural pupils was significantly reduced compared to baseline; mean (+/-SD) change was 0.04 +/- 0.13 logMAR (t = 3.3, P = .001). The low-contrast loss was larger (1.5 lines) with dilated pupils; mean (+/-SD) change was 0.13 +/- 0.15 logMAR (t = 9.31, P < .001). Greater losses in dilated low-contrast visual acuity were associated with concurrent astigmatic ketatotomy (t = 2.28, P = .025) and corneal haze of grade 1 or greater (t = 2.71, P = .005). CONCLUSIONS: Reductions in visual performance occur after photorefractive keratectomy with a 6-mm zone. These changes are greatest for low-contrast visual acuity with dilated pupils. Corneal haze and concurrent astigmatic keratotomy are associated with greater losses in low-contrast visual acuity. Best-spectacle-corrected low-contrast visual acuity is a sensitive measure for evaluating visual performance after refractive surgery.

Adult↗
PubMed1999

Induced astigmatism after photorefractive keratectomy.

PURPOSE: To retrospectively analyze a group of patients to determine whether their induced astigmatism was caused by asymmetry in the laser beam, asymmetry in ablation rates, or wound healing in different corneal meridians. SETTING: Single-center physician office. METHODS: In this study, 146 eyes of 116 patients who had photorefractive keratectomy (PRK) for myopia with the Apex laser (Summit Technology) were retrospectively identified. In 28 eyes, the patient's chair had been rotated 90 degrees from its usual position under the laser. The vector-summated mean change in astigmatism in eyes with the chair rotated 90 degrees was compared with that in a group of control eyes in which the chair was in the usual position. RESULTS: The vector-summated mean change in the control eyes was 0.30 diopter (D) at 83 degrees. Forty-eight of 113 eyes (42.5%) had induced with-the-rule (WTR) astigmatism, and 14 of 113 eyes (12.4%) had induced against-the-rule (ATR) astigmatism. In the eyes in which the chair was rotated 90 degrees, vector-summated mean change was 0.10 D at 13 degrees (P < .0005). One of 27 eyes (3.7%) had induced WTR astigmatism, and 13 of 27 eyes (48.1%) had induced ATR astigmatism (P < .001, chi-square). CONCLUSION: Astigmatism induced by myopic PRK with the Apex laser was small. The axis of induced astigmatism rotated 90 degrees when the patient's chair was rotated, implying that it is inhomogeneities in the beam rather than meridional asymmetry in ablation rates or wound healing that are responsible for induced astigmatism.

Adult↗
PubMed1999

Growth factor expression in corneal wound healing after excimer laser keratectomy.

PURPOSE: To develop a rabbit model of reproducible corneal haze after excimer laser keratectomy and to characterize expression of transforming growth factor beta (TGFbeta) and basic fibroblast growth factor (bFGF) in rabbit corneas during haze formation. METHODS: Seven rabbits underwent a 100 microm deep phototherapeutic keratectomy (PTK) in one eye and a 15-microm shallow PTK in the contralateral eye. Corneal haze was compared at 1-20 weeks after surgery. Subsequently, 16 rabbits underwent 100-microm PTK in one eye and 15-microm PTK in the contralateral eye. Four rabbits were killed at 1, 2, 3, and 4 weeks, respectively, after surgery. Immunohistochemistry was performed on the corneas to localize the expression of TGFbeta and bFGF. Control subjects were rabbits that underwent either epithelial debridement alone or no surgery. RESULTS: A 100-microm PTK resulted in significantly more corneal haze than a 15-microm PTK at every postoperative examination (p < 0.05). Both TGFbeta and bFGF were expressed in the scars at 1-4 weeks after deep and shallow excimer ablations. bFGF was expressed in the keratocytes of both treated and control corneas. Minimal TGFbeta was detected in the keratocytes of the control corneas, whereas prominent TGFbeta expression was noted in the keratocyte-like cells adjacent to the postkeratectomy scars. CONCLUSIONS: The 100-microm PTK ablation resulted in significantly more corneal scarring than the 15-microm PTK ablation. Even though there was no immunohistochemical difference in the pattern of TGFbeta and bFGF expression after deep and shallow ablations, there was an association between the expression of the growth factors and corneal scarring after excimer laser keratectomy.

Animals↗
PubMed1998

The prediction of surgically induced refractive change from corneal topography.

PURPOSE: To develop a method to predict the refractive power of the cornea from corneal topography. METHODS: We reviewed preoperative and postoperative cycloplegic refraction, keratometry, and corneal topography in 40 eyes of 40 patients who had undergone photorefractive keratectomy, radial keratotomy, myopic keratomileusis in situ, or hyperopic lamellar keratoplasty. For each axial dioptric power map, we calculated the aspheric ellipsoid that best fit that map. Central corneal points were weighted more heavily than peripheral points, based on the Stiles-Crawford effect. The equation of the best-fit ellipsoid yielded the spherical and astigmatic power and axis for each cornea preoperatively and postoperatively. RESULTS: The preoperative corneal spherical and astigmatic powers measured by the best-fit method were consistent with the spherical and astigmatic powers measured by keratometry and simulated keratometry. The change in corneal spherical power predicted by the best-fit method was significantly (P < .05) more accurate at predicting the change in spherical equivalent refraction than change either in spherical equivalent keratometry or in spherical equivalent simulated keratometry. The prediction of the astigmatic change was less precise than that of the spherical, but the best-fit method was the most accurate. CONCLUSIONS: The best-fit method is more accurate than simulated keratometry and standard keratometry are in evaluating corneal refractive power after refractive surgery. An improved method of calculating corneal refractive power may facilitate subjective refraction after refractive surgery, improve the accuracy of intraocular lens power calculation for eyes that have had previous refractive surgery, and improve ablation profiles for excimer laser refractive surgery.

Astigmatism↗
PubMed1998

Photorefractive keratectomy versus laser in situ keratomileusis for moderate to high myopia. A randomized prospective study.

OBJECTIVE: This report presents the results of a randomized clinical trial of photorefractive keratectomy (PRK) and laser-assisted in situ keratomileusis (LASIK). DESIGN: A randomized, prospective multicenter clinical trial. PARTICIPANTS: A total of 220 eyes of 220 patients entered the study cohort: 105 randomized to PRK and 115 to LASIK. The mean preoperative manifest refraction spherical equivalent was -9.23 diopters (D) in the PRK group and -9.30 D in the LASIK group. INTERVENTION: All patients received a one-pass, multizone excimer laser ablation as part of either a PRK or LASIK procedure using the Summit Apex excimer laser. Attempted corrections ranged from 6.00 to 15.00 D. MAIN OUTCOME MEASURES: Data on uncorrected and spectacle-corrected visual acuity, predictability,and stability of refraction, corneal haze, and flap complications were analyzed. Patients were observed for up to 6 months. RESULTS: One day after surgery, 0 (0.0%) and 3 (4.5%) eyes in the PRK group saw 20/20 and 20/40 or better uncorrected, respectively, while 7 (10%) and 48 (68.6%) eyes in the LASIK group saw 20/20 and 20/40 or better, respectively. At 6 months after PRK, 13 (19.1%) and 45 (66.2%) eyes saw 20/20 and 20/40 or better, respectively, while after LASIK, 16 (26.2%) and 34 (55.7%) eyes saw 20/20 and 20/40 or better, respectively (odds ratio = 0.56 for likelihood of uncorrected visual acuity < 20/40 for PRK vs. LASIK, 95% confidence interval [CI] = 0.31-1.19). After PRK, 39 eyes (57.4%) were within 1.0 D of attempted correction compared with 24 eyes (40.7%) in the LASIK group (odds ratio = 0.50 for likelihood fo undercorrection 1.0 D for PRK vs. LASIK, 95% CI = 0.24-1.04); however, the standard deviation of the predictability was similar between groups: 1.01 D for PRK and 1.22 D for LASIK. From months 1 to 6, there was an average regression of 0.89 D in the PRK group and 0.55 D in the LASIK group. After PRK, eight eyes (11.8%) had a decrease in spectacle-corrected visual acuity of two Snellen lines or more; after LASIK, two eyes (3.2%) had a decrease of two lines or more (odds ratio = 3.89 for risk of loss of spectacle-corrected visual acuity for PRK vs. LASIK, 95% CI = 0.71-21.30). Only two eyes had postoperative spectacle-corrected visual acuity less than 20/32, however. CONCLUSIONS: Although improvement in uncorrected visual acuity is more rapid in LASIK than in PRK, efficacy outcomes in the longer term generally are similar between the two procedures. There is a greater tendency toward undercorrection in LASIK eyes using the specific laser and nomogram in this study, but the scatter in achieved versus attempted correction is similar, suggesting little difference in the accuracy of the two procedures. A suggestion of decreased propensity for loss of spectacle-corrected visual acuity in LASIK eyes requires further investigation.

Adult↗