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PubMed2001

Accuracy and predictability of intraocular lens power calculation after laser in situ keratomileusis.

PURPOSE: To study the accuracy and predictability of intraocular lens (IOL) power calculation in eyes that had laser in situ keratomileusis (LASIK). SETTING: Gimbel Eye Centre, Calgary, Alberta, Canada. METHODS: Refractive outcomes in 6 cataract surgery and lensectomy eyes after previous LASIK were analyzed retrospectively. Target refractions based on measured and refraction-derived keratometric values were compared with postoperative achieved refractions. Differences between target refractions calculated using 5 IOL formulas and 2 A-constants and achieved refractions were also compared. RESULTS: The refractive error of IOL power calculation in postoperative LASIK eyes was significantly reduced when refraction-derived keratometric values were used for IOL power calculation. Persistent residual hyperopia still occurred in some cases; this was corrected by hyperopic LASIK. Refractive results appeared more accurate and predictable when the Holladay 2 or Binkhorst 2 formula was used for IOL power calculation. CONCLUSION: Hyperopic error after cataract surgery in post-LASIK eyes was significantly reduced by using refraction-derived keratometric values for IOL power calculation. Persistent hyperopic error was corrected by hyperopic LASIK.

Adult↗
PubMed2001

Minimizing the risk of recutting with a Hansatome over an existing Automated Corneal Shaper flap for hyperopic laser in situ keratomileusis enhancement.

We report a case series of 4 eyes to discuss the intraoperative complications of recutting a laser in situ keratomileusis (LASIK) flap with a Hansatome microkeratome over an existing 160 microm Automated Corneal Shaper flap for the retreatment of hyperopia. In the eyes that were recut, slivers of stroma were apparent on reflection of the flap; the slivers were located centrally in the 180 microm eye and peripherally in the 160 microm eyes. Recutting a flap for LASIK retreatment runs the risk of visually significant stromal irregularities.

Corneal Stroma↗
PubMed2001

Refractive changes after excimer laser phototherapeutic keratectomy.

PURPOSE: To study the visual and refractive changes in patients with superficial corneal opacities after excimer laser phototherapeutic keratectomy (PTK). SETTING: Eye Clinic, Kobe Kaisei Hospital, Kobe, Japan. METHODS: One hundred twelve eyes of 80 patients with superficial corneal opacities had PTK with the Nidek EC-5000 excimer laser system. All patients had routine ophthalmic examinations including uncorrected and Landolt best corrected visual acuity (BCVA) measurements, subjective and objective refractions, keratometry, EyeSys (Premier Laser Systems, Inc.) corneal topography performed before and 1 week and 1, 3, 6, and 12 months after PTK, and pachymetry performed before and 12 months after PTK. The change in refractive status within 12 months of PTK and the relationship between factors such as ablation depth, transition zone (TZ) setting, and use of masking agents and the amount of hyperopic shift were also assessed. RESULTS: The BCVA increased by more than 2 lines in 65.1% of eyes and by 1 line in 24.1%. The BCVA did not change in 12 eyes (10.8%) because of cataract or underlying retinal disease. A mean hyperopic shift of 3.42 +/- 1.15 diopters (D) (range 1.00 to 5.25 D) was seen in all eyes at 12 months. The hyperopic shift peaked 1 month after PTK and tended to decline after that; it stabilized at 12 months. CONCLUSION: Although PTK is a safe and efficient method for the treatment of superficial corneal opacities, induced hyperopia after the procedure remains a major problem. A shallow ablation depth (less than 100 microm), presence of a TZ setting, and use of a masking agent decrease the hyperopic shift significantly.

Adult↗
PubMed2001

Customized ablation for asymmetrical corneal astigmatism.

PURPOSE: To evaluate laser in situ keratomileusis (LASIK) cases in which a customized ablation assisted by corneal topography was performed. SETTING: Instituto de la Visión, Buenos Aires, Argentina. METHODS: The study group comprised 23 cases with asymmetrical corneas; 17 had myopia and 6, hyperopia. Visual acuity, spherical equivalent (SE), and cylinder vectorial change measurements, along with keratometry and corneal topography, were performed in all cases preoperatively and postoperatively. RESULTS: In the myopic cases, the mean preoperative SE was -4.92 diopters (D) +/- 2.46 (SD); it was -0.38 +/- 0.66 D after a mean follow-up of 4.41 +/- 2.32 months. In the hyperopic cases, the preoperative SE was +3.54 +/- 1.57 D; it was +0.33 +/- 0.50 D after a mean follow-up of 3.42 +/- 3.23 months. Cylinder vectorial change, visual acuity, and the number of visual acuity lines gained or lost were also evaluated in both groups. CONCLUSION: Although some features of our algorithm for corneal-topography-assisted customized ablations should be modified, the results of our treatment of cases with asymmetrical astigmatism were encouraging.

Adult↗
PubMed2001

Myopic and hyperopic laser in situ keratomileusis retreatments: indications, techniques, limitations, and results.

PURPOSE: To assess the efficacy of myopic and hyperopic laser in situ keratomileusis (LASIK) retreatment procedures. SETTING: Mater Private Hospital, Dublin, Ireland. METHODS: Retreatment was defined as either lifting the previously created flap or when this was not possible, cutting a new flap. Fifty-six patients were retreated, 17 with hyperopia (Group 1) and 39 with myopia (Group 2). The mean preoperative spherical equivalent in Group 1 was +3.79 diopters (D) +/- 1.53 (SD) (range +1.75 to +8.12 D) and in Group 2, -5.46 +/- 2.87 D (range -0.38 to -15.25 D). RESULTS: The indications for retreatment were undercorrection, decentration, epithelial ingrowth, and central island. Postoperatively, the mean spherical equivalents in Groups 1 and 2 were +1.11 +/- 2.02 D (range -1.75 to +5.50 D) and -1.02 +/- 2.20 D (range +4.75 to -9.00 D), respectively. In Group 1, the uncorrected visual acuity (UCVA) was 6/12 or better in 5.8% preoperatively and in 35% postoperatively. In Group 2, the UCVA was 6/12 or better in 5.1% preoperatively and in 59.0% postoperatively. Although 29% of the hyperopic eyes and 8% of the myopic eyes lost 1 Snellen line of best corrected visual acuity (BCVA), there was an improvement (of 1 or more lines) in BCVA in 12% and 49%, respectively. In cases that were decentered preoperatively, the postoperative optical zone ablation centration was better in 85.7% of Group 1 eyes and 61.5% of Group 2 eyes. Corneal complications following retreatment included peripheral scarring, epithelial ingrowth, Bowman's folds, and keratectasia. CONCLUSIONS: Both myopic and hyperopic retreatments resulted in a stable refractive outcome. Myopic retreatments were superior to hyperopic retreatments in both efficacy and safety.

Adult↗
PubMed2002

Arcuate keratotomy for asymmetrical steep islands after laser in situ keratomileusis and automated lamellar keratoplasty.

PURPOSE: To determine the safety and efficacy of arcuate keratotomy (AK) to reduce or eliminate steep asymmetrical islands after laser in situ keratomileusis (LASIK) and automated lamellar keratoplasty (ALK). SETTING: Rancho Bernardo Laser and Vision Center, San Diego, California, USA. METHODS: This retrospective and noncomparative interventional study comprised 8 eyes of 5 patients who received arcuate incisions to reduce topographically defined asymmetrical steep islands after LASIK (n = 7) and ALK for hyperopia (n = 1). The islands occurred unexpectedly after standard excimer laser treatment (VISX Star and S2) for myopic astigmatism that induced irregular astigmatism and unwanted optical effects. Cases occurred consecutively over 16 months, an incidence of less than 1%. Arcuate incisions extended 30 or 45 degrees in LASIK eyes based on the amount of residual refractive astigmatism and were placed at 7.0 mm on the steep axis. Radial incisions were limbal sparing to a 5.0 mm optical zone following the Casebeer nomogram. Outcome measures were uniformity of postenhancement topography, uncorrected visual acuity (UCVA), postenhancement refraction, and reduction in unwanted optical effects. RESULTS: The preenhancement mean spherical equivalent (SE) in the LASIK eyes was -0.99 diopters (D) +/- 0.48 (SD); the astigmatism ranged from 0.50 to 1.75 D. After incisional keratotomy, the mean SE was -0.21 +/- 0.12 D and the net residual astigmatism was reduced to a range of 0 to 0.75 D. All 8 eyes had AK to reduce topographically defined steep islands that were causing visual blurring and unwanted optical effects including ghosting, halos, and polyplopia. After enhancement, there was a marked reduction in the asymmetrical steep islands by topography, fewer unwanted optical effects, less refractive astigmatism, and improved UCVA. Two patients retained small inferior steep areas that may indicate forme fruste keratoconus, although this condition was not detected preoperatively by topographical indices. CONCLUSION: Uncorrected visual acuity improved and unwanted optical effects were reduced after AK on the peripheral axis of asymmetrical steep islands that occurred after uneventful LASIK and hyperopic ALK. This relatively simple incisional approach may be used until more advanced topography-linked ablations with rapid and precise eye tracking are perfected and widely available.

Adult↗
PubMed2002

Corneal asphericity after hyperopic laser in situ keratomileusis.

PURPOSE: To analyze corneal asphericity after hyperopic laser in situ keratomileusis (LASIK) and its relationship to the clinical outcomes. SETTING: Corneal and Refractive Surgery Service, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, USA. METHODS: In a retrospective case series, 23 patients (33 eyes) with hyperopia or hyperopic astigmatism who had LASIK were evaluated. A computer program (Holladay Diagnostic Summary, EyeSys Laboratories) was used to analyze corneal asphericity (Q) before and after LASIK. Corneal asphericity was evaluated to determine the association with the postoperative refractive error, best spectacle-corrected visual acuity (BSCVA), uncorrected visual acuity (UCVA), achieved refractive correction, mean corneal power (K), refractive yield (achieved/attempted correction), and keratometric yield (change in keratometry/attempted correction). RESULTS: After hyperopic LASIK, all corneas exhibited increased negative central Q. The postoperative corneal radius of curvature, BSCVA, and refractive and keratometric yields were not significantly correlated with the preoperative Q values. The asphericity change, Delta Q, was highly correlated with the achieved correction (r = 0.747, P <.0001). The postoperative Q value correlated well with the preoperative value (r = 0.534, P <.05) and the achieved correction (r = 0.601, P <.05) but not with the Delta Q. Neither the postoperative Q nor the Delta Q was correlated with the spherical equivalent, K, BSCVA, or UCVA. CONCLUSIONS: Asphericity may be a useful quantitative descriptor of the corneal optical contour after hyperopic LASIK. Negative central Q increased after hyperopic LASIK, especially when greater degrees of refractive correction were attempted.

Adult↗
PubMed2003

Histological and immunohistochemical findings after laser in situ keratomileusis in human corneas.

PURPOSE: To describe histopathological and immunohistochemical findings in human corneas after myopic laser in situ keratomileusis (LASIK) followed by iatrogenic keratectasia and after hyperopic LASIK. SETTING: Department of Ophthalmology, University of Innsbruck, Innsbruck, Austria. METHODS: Clinical, histological, and immunohistochemical investigations were performed of 1 human cornea with iatrogenic keratectasia following myopic LASIK and 1 human cornea with irregular astigmatism and central scar formation after hyperopic LASIK. Corneal buttons were obtained during penetrating keratoplasty in both patients. RESULTS: Histopathological examination showed thinning of the central stroma with a posterior residual thickness of 190 microm in the patient with iatrogenic keratectasia after myopic LASIK and significant midperipheral thinning in the patient who had hyperopic LASIK. However, this characteristic ablation profile of the stroma after hyperopic LASIK was partially mitigated and compensated by the epithelium, which was significantly thinned in the center and markedly thickened in the midperiphery. Traces of wound healing with minimal scar tissue were present at the flap margin after myopic and hyperopic LASIK. In a few sections of the cornea with keratectasia after myopia LASIK, only a few collagen lamellae were visible crossing between the posterior residual stroma and the superficial flap. Immunohistochemical examination revealed minimally increased staining of dermatan sulfate proteoglycan within the stroma adjacent to the interface of the microkeratome incision. Increased staining of hepatocyte growth factor was found on keratocytes/fibroblasts at the flap margin in both corneas. CONCLUSIONS: The wound-healing response is generally poor after LASIK, which may result in significant weakening of the tensile strength of the cornea after myopic LASIK, probably due to biomechanically ineffective superficial lamella. After LASIK in patients with high hyperopia, compensatory epithelial thickening in the annular midperipheral ablation zone might be partly responsible for regression.

Adult↗
PubMed2003

Acute psychotic reaction caused by topical cyclopentolate use for cycloplegic refraction before refractive surgery: case report and review of the literature.

A 56-year-old woman was evaluated for the surgical correction of hyperopia (+3.0 diopters). Two drops of cyclopentolate 1% were instilled in both eyes for measurement of the cycloplegic refraction and wavefront analysis. Immediately after the second instillation, the patient reported drowsiness, dizziness, nausea, and fatigue. Ten minutes later, stimulatory central nervous system symptoms in the form of restlessness, cheerfulness, and a 20-minute-long roar of laughter were observed, interrupted by a new sedative phase. Basic medical and neurologic examinations were unremarkable except for gait ataxia. Four hours later, the examination was continued uneventfully. As surgical treatment of refractive errors and measurement of cycloplegic refraction using cyclopentolate become more frequent, ophthalmologists should be aware of this unusual acute event.

Acute Disease↗
PubMed2003

Corneal perforation after conductive keratoplasty with previous refractive surgery.

A 56-year-old woman had conductive keratoplasty (CK) for residual hyperopia and astigmatism. Three years before the procedure, the patient had arcuate keratotomy, followed by laser in situ keratomileusis 2 years later for high astigmatism correction in both eyes. During CK, a corneal perforation occurred in the right eye; during the postoperative examination, an iris perforation and anterior subcapsule opacification were seen beneath the perforation site. The perforation was managed with a bandage contact lens and an antibiotic-steroid ointment; it had a negative Seidel sign by the third day. The surgery in the left eye was uneventful. Three months after the procedure, the uncorrected visual acuity was 20/32 and the best corrected visual acuity 20/20 in both eyes with a significant improvement in corneal topography. Care must be taken to prevent CK-treated spots from coinciding with areas in the corneal stroma that might have been altered by previous refractive procedures.

Anti-Infective Agents↗
PubMed2003

Comparison of myopes and hyperopes after laser in situ keratomileusis monovision.

PURPOSE: To compare the results of laser in situ keratomileusis (LASIK) monovision in myopes and hyperopes. SETTING: Private practice, Little Silver, New Jersey, USA. METHODS: In this retrospective study, 391 consecutive patients older than 40 years who had LASIK between December 1999 and June 2001 were examined. All patients were asked to complete a questionnaire, and study results are based on the analysis of data from patient charts correlated with questionnaire responses. RESULTS: Visual results were excellent in both groups, with all monovision patients achieving 20/30 acuity or better in the distance eye and J2 or better acuity in the near eye. Satisfaction scores were high in all groups. Statistical analysis indicated that visual results for distance were better in myopes than in hyperopes (P =.043), enhancements were higher in monovision (P =.04) and in hyperopia (P =.08), and satisfaction was higher among myopes (P =.012) and full distance patients (P =.002). Monovision hyperopes had the most difficulty with 6 side effects (P =.00). CONCLUSION: Hyperopic monovision was a viable but more problematic solution to correcting presbyopia than myopic monovision.

Adult↗
PubMed2003

Photorefractive keratectomy to correct hyperopic shift after radial keratotomy.

To evaluate the safety, efficacy, and predictability of photorefractive keratectomy (PRK) to correct post-radial-keratotomy (RK) hyperopic shift. University of Sherbrooke, Sherbrooke, Québec, Canada.This retrospective nonconsecutive case series comprised 53 eyes of 53 patients who had PRK to correct hyperopic shift after RK. Both RK and PRK were performed by the same surgeon at the same clinic from 1993 to 2001.The mean time after RK was 57 months (range 24 to 84 months). The mean follow-up after hyperopic PRK (HPRK) was 10 months (range 3 to 33 months). The mean hyperopic shift 1 month post-RK to HPRK was +1.6 diopters (D) +/- 1.0 (SD) (range +0.25 to +4.125 D). The mean pre-HPRK spherical equivalent (SE) was +2.15 +/- 0.80 D (range +1.00 to +4.125 D) and the mean post-HPRK SE, -0.10 +/- 0.80 D (range -2.00 to +2.125 D). At the last examination, 47 eyes (88.7%) had a refractive error within +/-1.0 D of emmetropia and 38 eyes (71.7%) had an uncorrected visual acuity of 20/25 or better. Two eyes lost 1 Snellen line of best corrected visual acuity. No significant haze or complications developed in any eye. Hyperopic PRK with a conservative technique (large optical zone and small ablation thickness) can be used successfully to correct RK-induced hyperopia in patients with small to moderate refractive errors. It appeared to be effective, predictable, and safe.

Adult↗
PubMed2003

Fourier analysis of induced irregular astigmatism. Photorefractive keratectomy versus laser in situ keratomileusis in a bilateral cohort of hyperopic patients.

PURPOSE: To analyze corneal topographic data by Fourier analysis to determine differences in irregular astigmatism following spherical hyperopic correction by photorefractive keratectomy (PRK) or laser in situ keratomileusis (LASIK). SETTING: Department of Ophthalmology, St. Thomas' Hospital, London, United Kingdom. METHODS: Thirty-six eyes of 18 patients with moderate hyperopia had LASIK in 1 eye and PRK in the other eye. The flap was cut on a nasal hinge with a Moria LSK One microkeratome. The laser was a Summit SVS Apex Plus with an optical zone of 6.5 mm and a blending zone of 1.5 mm. Corneal topographic data were acquired with a TMS-1 topographer (Computed Anatomy Inc.) preoperatively and 1, 3, 6, and 12 months postoperatively. The ASCII files containing the dioptric power values were extracted and analyzed with custom-written software to extract the Fourier harmonics. RESULTS: The irregular astigmatism increased in both groups postoperatively, peaking at 3 months and then decreasing over the next 9 months. There was no statistically significant difference between the 2 groups at any time point (P<.05). The change in the topographically derived equivalent sphere showed undercorrection in both groups at all time points. Regular astigmatism showed a marginal statistically significant increase in the LASIK group at 12 months (P =.049). CONCLUSION: Irregular astigmatism, equivalent sphere, and regular astigmatism were not significantly different in the PRK and LASIK groups during the follow-up. Based on the corneal topography, the 2 procedures induced an equal amount of irregular astigmatism.

Adult↗
PubMed1994

Clear lens extraction for the correction of high refractive error.

The results of clear lens extraction and posterior chamber intraocular lens implantation in 31 eyes with high myopia and six eyes with high hyperopia were reviewed. In the myopic group, 77% of eyes achieved 20/40 or better uncorrected postoperative visual acuity and 97% achieved 20/40 or better corrected acuity. Sixty-eight percent of eyes were within 1.0 diopter (D) of emmetropia and 90% were within 2.0 D. Astigmatic keratotomy (four eyes) and radial keratotomy (one eye) were performed for postoperative refractive errors. Intraocular lens exchange was necessary to correct power in one case. In the hyperopic group, all six eyes achieved 20/40 or better uncorrected postoperative visual acuity and all were within 1.0 D of emmetropia. During the 20-month mean follow-up, no retinal detachment or cystoid macular edema was observed. Posterior capsule opacification was the major complication and it developed faster than reported in other studies.

Adult↗
PubMed1990

Effects of intraocular lens position errors on postoperative refractive error.

Previous theoretical attempts to predict the refractive effects of intraocular lens (IOL) misalignment have resulted in conflicting information. Discrepancies in both the potential magnitude and direction of the refractive changes exist in the literature. This paper provides a detailed description of the mathematical framework required to achieve a valid predictive model and a quantitative analysis of the effects of IOL positional errors. The effects of misalignment are shown to influence the spherical refractive component primarily. Astigmatism related to oblique incidence is generally small. Movement of the IOL away from the retina produces myopia, while movement toward the retina produces hyperopia. It is likely that longitudinal IOL positional errors are a principal component of postoperative refractive errors. Alignment errors, on the other hand, must have generally minor effects on refraction.

Astigmatism↗
PubMed1990

Effect of thermokeratoplasty on corneal curvature.

A cadaver eye model was used to evaluate and quantify the use of thermokeratoplasty for steepening the central cornea to correct hyperopia. Four groups of eye-bank eyes were treated with four separate surgical plans. Each plan involved the placement of controlled thermal burns (in the depths of the corneal stroma, using a cautery probe) applied in a radial pattern up to a premarked optical zone. The plans differed in the sequence of surgical steps. All plans progressively added radials and applications (to decrease optical zone) in various sequences. Corneal curvature was measured at baseline and at each surgical step. As more surgery was done within each plan, the corneas became progressively steeper. Total mean changes in corneal curvature ranged from 16.26 diopters to 19.76 diopters, depending on the plan. At each optical zone, as the number of radials increased, the effect increased. With progressively smaller optical zone size, the effect also increased.

Cornea↗
PubMedDate not supplied

Refractive changes after phototherapeutic keratectomy.

PURPOSE: To evaluate refractive error changes after phototherapeutic keratectomy (PTK). SETTING: University Eye Hospital, Kiel, and University Eye Hospital, Hulle, Germany. METHODS: The MEL 60 excimer laser (Aesculap Meditec) was used in all cases. To even out the peaks and valleys of irregular surfaces, modulating agents were applied. The study included 45 patients with various preoperative corneal diseases: central scars, recurrent erosions, corneal dystrophies, and surface irregularities. Subjective and objective refraction, keratometry, slitlamp photography, and corneal topography were performed preoperatively and postoperatively. The follow-up was up to 24 months. RESULTS: Twenty-six patients had stable postoperative refractions. Thirteen patients developed a hyperopic shift; the highest observed amount was +4.0 diopters. In seven patients, the astigmatic error increased, although no significant change in axis was measured. Three patients had a myopic shift. CONCLUSION: After PTK, all types of refractive change can occur. The greatest risk is that of a hyperopic shift. We saw a correlation between the degree of hyperopia and the ablation depth. Methods for preventing such changes include (1) a large treatment zone, (2) use of a polishing program involving a low viscosity fluid at the end of the laser procedure, (3) a two-step treatment in selected cases to avoid ablations that are too deep.

Adult↗