Showing papers in "Journal of Refractive Surgery in 2001"

History and Principles of Shack-Hartmann Wavefront Sensing

Abstract: developed out of a need to solve a problem. The problem was posed, in the late 1960s, to the Optical Sciences Center (OSC) at the University of Arizona by the US Air Force. They wanted to improve the images of satellites taken from earth. The earth's atmosphere limits the image quality and exposure time of stars and satellites taken with telescopes over 5 inches in diameter at low altitudes and 10 to 12 inches in diameter at high altitudes. Dr. Aden Mienel was director of the OSC at that time. He came up with the idea of enhancing images of satellites by measuring the Optical Transfer Function (OTF) of the atmosphere and dividing the OTF of the image by the OTF of the atmosphere. The trick was to measure the OTF of the atmosphere at the same time the image was taken and to control the exposure time so as to capture a snapshot of the atmospheric aberrations rather than to average over time. The measured wavefront error in the atmosphere should not change more than ␭/10 over the exposure time. The exposure time for a low earth orbit satellite imaged from a mountaintop was determined to be about 1/60 second. Mienel was an astronomer and had used the standard Hartmann test (Fig 1), where large wooden or cardboard panels were placed over the aperture of a large telescope. The panels had an array of holes that would allow pencils of rays from stars to be traced through the telescope system. A photographic plate was placed inside and outside of focus, with a sufficient separation, so the pencil of rays would be separated from each other. Each hole in the panel would produce its own blurry image of the star. By taking two images a known distance apart and measuring the centroid of the images, one can trace the rays through the focal plane. Hartmann used these ray traces to calculate figures of merit for large telescopes. The data can also be used to make ray intercept curves (H'-tan U'). When Mienel could not cover the aperture while taking an image of the satellite, he came up with the idea of inserting a beam splitter in collimated space behind the eyepiece and placing a plate with holes in it at the image of the pupil. Each hole would pass a pencil of rays to a vidicon tube (this was before …

Aberrations and visual performance following standard laser vision correction.

Abstract: 6 pages, 5 figures.-- PMID: 11583239 [PubMed].-- Presented at the 2nd International Congress of Wavefront Sensing and Aberration-free Refractive Correction, in Monterey, CA, on February 9-10, 2001.

Complications of laser in situ keratomileusis: Etiology, prevention, and treatment

Abstract: PURPOSE: To review the etiology, prevention, and management of laser in situ keratomileusis (LASIK) complications. METHODS: Review of literature and the experience of the authors. RESULTS: Careful preoperative screening is critical to prevention of many potential complications of LASIK. Flap complications that occur during surgery are typically managed by replacement of the flap and repeating the surgery or applying special methods such as transepithelial photorefractive keratectomy weeks to months following the initial procedure. A common source of serious complications is the use of a microkeratome that functions after improper assembly. Timely treatment of postoperative complications such as diffuse lamellar keratitis, flap striae, and infection is critical to an optimal outcome. CONCLUSION: Most complications of LASIK can be treated effectively and have minimal effect on the final outcome after surgery, if appropriate methods are used for management. [J Refract Surg 2001;17:350-379]

Effect of acute biomechanical changes on corneal curvature after photokeratectomy.

Abstract: Purpose Unintended hyperopic shift is a common yet poorly understood complication of phototherapeutic keratectomy (PTK) that raises fundamental questions about the etiology of corneal curvature change in PRK and LASIK. We investigated the relative contributions of ablation profile and peripheral stromal thickening to intraoperative PTK-induced central flattening, and propose a biomechanical model of the acute corneal response to central ablation. Methods Fourteen de-epithelialized eye bank globes from seven donors underwent either broadbeam ablation (approximately 100-microm depth, no programmed dioptric change) or sham photoablation in paired-control fashion. Peripheral stromal thickness changes and the pattern of thickness loss across each ablation zone were evaluated by optical section image analysis as predictors of acute corneal flattening. Results Relative to sham ablation, keratectomy caused significant anterior corneal flattening (-6.3+/-3.2 D, P = .002). Concomitant peripheral stromal thickening (+57+/-43 microm, P = .01) was a significant predictor of acute hyperopic shift (r = 0.68, P = .047). Ablation pattern bias did not consistently favor hyperopia and was a poor lone predictor of hyperopic shift. Conclusions Unintended keratectomy-induced hyperopic shift is replicable in a human donor model and is associated with significant thickening of the unablated peripheral stroma. This biomechanical response may have a considerable impact on early refractive outcomes in PTK, PRK, and LASIK.

Iris-claw phakic intraocular lens for high myopia.

Abstract: Purpose To evaluate the efficacy, safety, predictability, and stability of implanting a polymethylmethacrylate (PMMA) phakic intraocular lens (PIOL) (the Artisan myopia lens) to correct high myopia. Methods An Artisan myopia lens was implanted in 78 consecutive eyes of 49 patients with preoperative myopia that ranged from -6.25 to -28.00 D. Mean patient age was 42.4 years. Mean follow-up was 10.7 months and all patients were followed for at least 6 months; 45 eyes had follow-up of 12 months, and 10 eyes had 24 months. The desired outcome was emmetropia in all eyes except for those eyes with preoperative myopia greater then -23.00 D. Results Fifty-three eyes (67.9%) had a postoperative refraction at the last follow-up examination within +/-1.00 D of emmetropia, and 39 eyes (50.0%) had a postoperative refraction +/- within 0.50 D of emmetropia. The postoperative refraction remained stable during the entire follow-up period. Mean spectacle-corrected visual acuity improved from 20/32 preoperatively to 20/25 postoperatively. Mean postoperative uncorrected visual acuity was 20/32. There was no significant change in endothelial cell density from baseline. We did not encounter major complications. Conclusion Implantation of the Artisan myopia lens to correct high myopia resulted in a stable and fairly predictable refractive outcome. A significant endothelial cell change was not detected.

Choice of spatial frequency for contrast sensitivity evaluation after corneal refractive surgery.

Abstract: PURPOSE: To study the utility of measurements of contrast sensitivity at different spatial frequencies as an index of visual recovery following refractive surgery. METHODS: Contrast sensitivity at 1.5, 3, 6, 12, and 18 c/deg was measured with the Stereo Optical FACT chart in 20 patients after photorefractive keratectomy (PRK) using the Nidek EC-5000 excimer laser system, and in 18 patients following laser in situ keratomileusis (LASIK). Contrast sensitivity was measured preoperatively and 1, 3, 6, and 12 months after surgery. RESULTS: Results showed a statistically significant reduction (P .1). In LASIK patients, decreased contrast sensitivity values 1 month after surgery were also obtained at all spatial frequencies. After 3 months, contrast sensitivity at 1.5 and 3 c/deg had recovered and did not differ significantly from preoperative values (P>.1), although contrast sensitivity at other frequencies remained reduced (P .1). CONCLUSIONS: Contrast sensitivity measurements at 6 and 12 c/deg appear to be most useful in the assessment of patients who have undergone laser refractive surgery because defocus and optical aberrations primarily affect the higher spatial frequencies.

Influence of corneal curvature on calculation of ablation patterns used in photorefractive laser surgery.

Abstract: PURPOSE: The aim of this work was to clarify the influence of the effective illumination area and possible reflection losses that occur during laser-tissue interaction on the modeling of profiles for customized corneal ablation, such as wavefront-guided treatments. METHODS: The changes of the ablation depth per laser pulse due to the projection of a laser spot onto the corneal front surface and reflection losses at the air-tissue interface were calculated. RESULTS: Moving with a scanning-spot from the center of the cornea toward the limbus resulted in an increase of the effective illumination area and reflection losses, which led to a decrease in the ablation depth per laser pulse. The decrease of the ablation depth was strongly related to the initial radiant exposure and the corneal curvature radius. CONCLUSIONS: The corneal front surface must be taken into consideration for ablation profile calculations, especially in customized treatments, due to the strong dependence of the ablation depth on the corneal curvature. [J Refract Surg 2001;17: S584-S587]

Corneal sensitivity and some properties of the tear film after laser in situ keratomileusis.

Abstract: PURPOSE: To investigate central corneal sensitivity, lipid layer structure of the precorneal tear film, and tear volume after laser in situ keratomileusis (LASIK). METHODS: Central corneal sensitivity was measured using the Non-Contact Corneal Aesthesiometer. The aesthesiometer was mounted on a slit lamp and an airpulse of controlled pressure was directed onto the cornea. When central corneal sensitivity was reduced, a higher air pulse pressure was required to stimulate the cornea. The final central corneal sensitivity threshold measured was recorded in millibars. Tear lipid layer structure was assessed by optical interferometry and classified according to appearance using the Keeler Tearscope. Tear volume was measured using the phenol red cotton thread test. Subjects were recruited from a group of patients after LASIK who had experienced no complications (n=22). The average postoperative time was 14 weeks and measurements were taken on one eye. In bilateral cases, measurements were recorded from the right eye only. Average attempted correction was -6.30 D (range, -2 to -11 D). Age-matched controls were later recruited for central corneal sensitivity threshold (n=24). A second group of age-matched controls were recruited for tear volume and lipid layer structure (n=24). RESULTS: The median (range) was 1.1 mbars (0.2 to 4.3 mbars) after LASIK and 0.58 mbars (0.20 to 1.3 mbars) in the controls; the difference was statistically significant (P = .043). The lipid layer of the tear film tended to be thinner in eyes after LASIK compared with controls (P = .032). The mean (+/- SD) tear volume was 16.9 +/- 8.3 mm after LASIK and 19.8 +/- 7.1 mm in controls. This difference was not statistically significant (P = .492). CONCLUSION: At 14 weeks postoperatively, central corneal sensitivity was below normal levels and the tear lipid layer was thinner. The poorer quality lipid layer may predispose to symptoms of dry eye after LASIK.

Mitomycin C reduces haze formation in rabbits after excimer laser photorefractive keratectomy.

Abstract: PURPOSE To investigate the effects of mitomycin C on haze after photorefractive keratectomy (PRK). METHODS Twenty of 24 rabbits underwent bilateral 193-nm excimer laser PRK to correct -10.00 D of myopia; the remaining four rabbits were not operated (no PRK group). The right eyes of the 20 rabbits were treated with 0.02% mitomycin C during surgery (PRK+MMC group) and the left eyes did not receive 0.02% mitomycin C (PRK alone group). Clinical and histopathologic examinations were performed. RESULTS The most severe haze in the PRK alone group after PRK reached grade 3; the PRK+MMC group did not exceed grade 1 haze. Statistically significant differences were found between the PRK+MMC and PRK alone groups from week 2 to week 26 after treatment (P .05). A marked reduction of keratocytes in the anterior stroma of the PRK+MMC group was observed. At week 1, 2, and 4 after PRK, keratocytes of the PRK+MMC group were only 3.1+/-2.6, 6.8+/-4.7, and 12.4+/-5.7 keratocytes x 10(4)/microm2, respectively, while those of the PRK alone group were 41.2+/-80, 42.3+/-7.8, and 40.0+/-3.3 keratocytes x 10(4)/microm2, respectively. There were statistically significant differences between the two groups (P<.001). CONCLUSION A single intraoperative application of topical mitomycin C during PRK in rabbits reduced corneal haze by inhibiting the proliferation of keratocytes.

Laser in situ keratomileusis vs. laser epithelial keratomileusis (LASIK vs. LASEK).

Abstract: Purpose To compare results of laser in situ keratomileusis (LASIK) and laser epithelial keratomileusis (LASEK) for the treatment of myopia. Methods Two groups of fifteen patients (30 eyes) each were assigned to either the LASIK group or the LASEK group. LASIK procedure: A Hansatome microkeratome with the ring at 9.5 mm was used to create the corneal flap (depth, 160 microm). The myopic correction was then registered on the Nidek EC-5000 excimer laser and the appropriate ablation performed. LASEK procedure: Twenty percent ethyl alcohol was placed within the corneal epithelial ring. An intact epithelial flap was retracted. The Nidek EC-5000 excimer laser was applied in a similar manner to the LASIK procedure. Patients from both groups were followed postoperatively for 6 months, measuring best spectacle-corrected visual acuity, contrast sensitivity, and corneal topographic meridians of 3 mm, 5 mm, and 7 mm. Results Comparing corneal topography, best spectacle-corrected visual acuity, and contrast sensitivity data, refractive results in the LASEK group were better than the LASIK group. Conclusion Objective data show that with the Nidek EC-5000 excimer laser, the LASEK method of corneal splitting may prove superior to the LASIK method.

Diffuse lamellar keratitis associated with recurrent corneal erosions after laser in situ keratomileusis.

Abstract: PURPOSE: Diffuse lamellar keratitis (DLK) is marked by the presence of diffuse or multifocal infiltrates confined to the laser in situ keratomileusis (LASIK) interface. These infiltrates are culture-negative, and the etiology is thought to be noninfectious. Most cases of DLK occur within the first week or two following surgery. METHODS: We describe one case of diffuse lamellar keratitis that occurred 3 months after LASIK. The patient developed a spontaneous corneal erosion in one eye. Over the next 2 days while the erosion was being treated, there was rapid development of DLK. Slit-lamp biomicroscopy and in vivo scanning slit confocal microscopy were performed. The patient was treated with intensive topical corticosteroids. RESULTS: Scanning slit confocal microscopy revealed numerous, highly-reflective round bodies consistent with a polymorphonuclear infiltrate located at the flap interface. Treatment with topical 1.0% prednisolone acetate was instituted, with rapid improvement in patient symptoms, visual acuity, and slit-lamp biomicroscopy. CONCLUSIONS: Diffuse lamellar keratitis may occur months after LASIK as a result of a spontaneous recurrent corneal epithelial erosion.

Wavefront customized ablations with the WASCA Asclepion workstation.

Abstract: PURPOSE: WASCA (Wavefront Aberration Supported Cornea Ablation) is a method for wavefront-guided ablation. This new method records all existing eye aberrations with the Asclepion Wavefront Aberrometer and calculates the customized pattern for laser correction. We measured the low and high order aberrations of eyes before and after PRK and LASIK, as well as before and after flap creation. METHODS: The Asclepion Shack-Hartmann aberrometer was used to measure wavefront aberrations. Preoperative and postoperative measurements were made following both PRK and LASIK performed with conventional software, modified Aberration-free Profile (AFA) software, and specially designed WASCA software. Surgery was performed with the Meditec MEL-70 G-scan excimer laser. Additionally, measurements were made before and after flap creation only (10 eyes). RESULTS: There was a significant difference between preoperative and 1-month postoperative high order aberrations, with notable increases following conventional PRK and LASIK and less increase following modified AFA PRK and LASIK. Flap creation only changed the higher order aberrations slightly, and caused a shift toward hyperopia. In the eyes that received WASCA correction with PRK or LASIK, at 3 months postoperative the high order aberrations averaged an increase of 1.3 times for PRK and 1.8 times for LASIK. Both the AFA and WASCA treatments demonstrated improved outcomes in comparison to conventional PRK and LASIK. CONCLUSION: Wavefront mapping of the eye and wavefront-guided ablation with the Asclepion Aberrometer can be used for optimizing the results and fine-tuning visual performance after laser vision correction. WASCA PRK appeared to result in better outcomes than

Clinical results after subepithelial photorefractive keratectomy (LASEK).

Abstract: PURPOSE To study the results of photorefractive keratectomy (PRK) after creation of an epithelial flap and replacement of the flap after ablation (LASEK). METHODS PRK was performed with the Nidek EC-5000 excimer laser. The technology of subepithelial PRK was developed in experiments in vitro in 10 pig eyes and six human eyes. The experiments in vivo were carried out in eight eyes of four rabbits. In patients, subepithelial PRK was carried out in 12 eyes with high myopia, best spectacle-corrected visual acuity of 20/30 and below. LASIK, ordinary PRK, or transepithelial PRK were performed in the second eye to act as a control. RESULTS The basic steps of subepithelial PRK include creation of an epithelial flap, refractive ablation, and subsequent repositioning of the epithelial flap. In the clinical trial, creation of an epithelial flap was easy in five (41.7%) eyes, moderate in four (33.3%) eyes, and difficult in three (25.0%) eyes. No pain occurred in six (50%) eyes, some discomfort in four (33.3%) eyes, and pain in two (16.7%) eyes. After subepithelial PRK, visual and refractive results were similar with both LASIK and PRK. The common components of ordinary PRK, transepithelial PRK, and subepithelial PRK are removal of Bowman's layer and epithelium. The advantages and disadvantages of subepithelial PRK are considered. CONCLUSION Subepithelial PRK (LASEK) has the potential for widespread use in clinical practice, but further development of special instruments and techniques would be helpful.

Intrastromal Corneal Ring Segments: Reversibility of Refractive Effect

Abstract: PURPOSE To evaluate the reversibility of refractive effect following removal of the ICRS (intrastromal corneal ring segments; Intacs) METHODS Data from 34 eyes from which ICRS were removed during United States FDA Phase II and III clinical trials were evaluated with regard to segment size, loss or change of best spectacle-corrected visual acuity (BSCVA), any change of uncorrected visual acuity (UCVA), manifest spherical equivalent refraction, manifest cylinder refraction, stability of manifest cylinder refraction, and subjective visual symptoms RESULTS Out of 725 initial or contralateral eyes placed with the ICRS during Phase II and III clinical trials, segments were removed from 34 eyes (47%) Other than one (1/725, 01%) safety related ICRS removal, 30/725 (41%) were due to visual symptoms ICRS removal was accomplished under topical anesthesia without complications in all eyes The mean length of time the segments remained in the cornea after initial surgery was 103 +/- 54 months At 3 months after ICRS removal, 21 eyes had monitored data available and were within +/-1 line or 10 letters of their preoperative BSCVA Twenty eyes (20/21, 95%) returned to within +/-100 D of their preoperative manifest spherical equivalent refraction All eyes had a stable refraction at the 3-month examination after removal, and a manifest spherical equivalent refraction within +/-100 D of their 1-month examination after removal Nineteen eyes (19/21, 90%) returned to within +/-2 lines and 16 eyes (16/21, 76%) returned to within +/-1 line of preoperative UCVA CONCLUSION The ICRS (Intacs) was easily and safely removed, and eyes returned to preoperative refractive status within 3 months

Laser in situ keratomileusis to correct residual myopia after cataract surgery.

Abstract: PURPOSE: To evaluate the effectiveness, predictability, and safety of laser in situ keratomileusis (LASIK) for correcting residual myopia after cataract surgery with intraocular lens implantation. METHODS: Twenty-two eyes of 22 patients underwent LASIK for the correction of residual myopia after cataract surgery. LASIK was carried out using the Chiron Automated Corneal Shaper and the NIDEK EC-5000 excimer laser. In all eyes, the follow-up was 12 months. RESULTS: Before LASIK, 1 eye (4.5%) had an uncorrected visual acuity of 0.5 or better; 12 months after LASIK, 10 eyes (45.4%) achieved this level of visual acuity and 0 eyes achieved 1.00 or better. Before LASIK, mean refraction was -2.90 +/- 1.80 D; 12 months after LASIK it decreased significantly to 0.40 +/- 0.60 D (P < .01). In 18 eyes (81.8%) at 12 months after LASIK, spherical equivalent refraction was within +/-1.00 D of emmetropia; 11 eyes (50%) were within 0.50 D. No vision-threatening complications occurred. CONCLUSION: LASIK with the Automated Corneal Shaper and Nidek EC-5000 excimer laser was an effective, predictable, stable, and safe procedure for correcting residual myopia after cataract surgery. No intraocular lens or cataract incision related complications occurred when LASIK was performed at least 3 months after phacoemulsification.

Changes in intraocular pressure after laser in situ keratomileusis.

Abstract: Purpose To evaluate changes in intraocular pressure (IOP) measurements by Goldmann applanation tonometry after laser in situ keratomileusis (LASIK) for myopia and myopic astigmatism, and to assess the accuracy of Goldmann applanation tonometry measurements after LASIK in these eyes. Methods LASIK was performed on 166 eyes of 93 patients for correction of myopia and myopic astigmatism. Intraocular pressure was measured by Goldmann applanation tonometry at the central and temporal parts of the cornea before and at 1, 3, 6, and 12 months after LASIK. The amount of change in IOP was computed and its relation to different variables was evaluated by regression analysis. Results Intraocular pressure measured at the center of the cornea was reduced by a mean of 3.69 +/- 1.63 mmHg after LASIK. Multiple regression analysis showed that the decrease in IOP was related to the preoperative IOP and the change in central corneal thickness after LASIK. Measurements of IOP at the temporal part of the cornea were also reduced by a mean of 2.39 +/- 1.71 mmHg. There was wide variability in the amount of difference between the temporal and central measurements after LASIK (temporal measurements were higher than central by 0 to +4 mmHg). Conclusion LASIK for myopia produced underestimation of IOP measured by Goldmann applanation tonometry at the central part of the cornea by a mean of 3.69 +/- 1.63 mmHg. The decrease of IOP was related to preoperative IOP and the change in central corneal thickness after LASIK. Temporal Goldmann applanation tonometry measurements, although decreased after LASIK, were less reliable.

Posterior chamber phakic intraocular lenses to correct high myopia: a comparative study between Staar and Adatomed models.

Abstract: Purpose To determine the feasibility of using posterior chamber phakic intraocular lenses (PIOLs) to treat high myopia, comparing two different models, Staar and Adatomed. Methods Twenty-four eyes from 12 patients were studied prospectively. A phakic Staar IOL was implanted in one eye of each patient, and the other eye received a phakic Adatomed IOL. Patients with uveitis or ocular trauma prior to ocular surgery, diabetic retinopathy, or capsular pseudoexfoliation were excluded. The mean preoperative spherical equivalent refraction was -16.00 +/- 5.05 D for the Staar group and -15.39 +/- 2.83 D for the Adatomed group. Average follow-up was 32.4 months (range, 19 to 46 mo) for the Adatomed group and 18.3 months (range, 11 to 21 mo) for the Staar group and included evaluation of intraocular pressure, intraocular lens pigment deposits, lens decentration, anterior subcapsular cataract, and visual acuity. Results Spectacle-corrected and uncorrected visual acuity improved in all eyes in both groups. No statistically significant differences in visual acuity gain were observed with the two materials (Student t-test, P = .08 for the Staar group and P = .6 for the Adatomed group), although the gain in visual acuity was somewhat greater with the Staar PIOLs. The difference in mean intraocular pressure before surgery and at last follow-up was 1.5 mmHg for the Staar group and 2.3 mmHg for the Adatomed group (P = .36). The incidence of lens pigment deposits was the same in both groups (41.66%), with deposits in 5 of the 12 eyes in both groups. The incidence of lens decentration was higher in the Adatomed group (5/12; 41.66%) than in the Staar group (2/12; 16.7%). Anterior subcapsular cataract was higher in the Adatomed group (4/12; 33.3%) than in the Staar group (3/12; 25%). Conclusions There was a higher incidence of lens decentration and anterior subcapsular cataract in the Adatomed group than in the Staar group.

Contrast Sensitivity After Posterior Chamber Phakic Intraocular Lens Implantation for High Myopia

Abstract: PURPOSE: To evaluate contrast sensitivity after posterior chamber phakic intraocular lens (PIOL) implantation for the correction of high myopia. METHODS: Twenty eyes of ten patients had a posterior chamber phakic intraocular lens (Staar ICL) implanted to correct high myopia. Mean preoperative myopia was -14.10 ± 2.70 D. Follow-up was 24 months for all patients. Contrast sensitivity was tested with best spectacle-corrected visual acuity preoperatively and 3, 6, 12, 18, and 24 months postoperatively. RESULTS: Contrast sensitivity increased after surgery in all spatial frequencies. Normal values were achieved for low and intermediate spatial frequencies (3 and 6 c/deg). However, in spite of the improvement, values were still below normal for high spatial frequencies (12 and 18 c/deg). When the first postoperative examination was not considered, there were no statistically significant differences in contrast sensitivity values at different postoperative periods. CONCLUSION: Contrast sensitivity increased after posterior chamber phakic intraocular lens implantation (Staar ICL) in all spatial frequencies when compared to preoperative contrast sensitivity (best spectacle-corrected).

The cornea is not a piece of plastic.

Abstract: To the Editor: In her recent editorial (Roberts C. The cornea is not a piece of plastic. J Refract Surg 2000;16:407413), Dr. Roberts points out that biomechanical flattening enhances a myopic excimer laser ablation and works against a hyperopic ablation. Would the circular severing of corneal lamellae in hyperopic ablation not lead to a contraction of the central part of these lamellae with a heaping up of tissue? This effect could compensate for the flattening by the peripheral pull or even exceed it. One might also argue that central islands in myopic ablation seem to contradict an additional central flattening effect. Klaus D. Teichmann, MD Jeddah, Saudi Arabia

Laser in situ keratomileusis for the correction of hyperopia from +0.50 to +11.50 diopters with the Keracor 117C laser.

Abstract: PURPOSE To evaluate excimer laser in situ keratomileusis (LASIK) for the correction of hyperopia. METHODS We reviewed retrospectively the medical records of 46 patients treated with LASIK for hyperopia. All patients had a complete ophthalmologic evaluation. The corneal bed was ablated using the Bausch & Lomb Chiron Keracor 117C excimer laser to create a paracentral annular ablation under a nasally hinged 160-microm corneal flap with the Chiron Automatic Corneal Shaper microkeratome. Follow-up was a minimum of 6 months. RESULTS Eighty eyes of 46 patients (23 males and 23 females) were included. Age ranged from 18 to 65 years (mean, 42 yr). The range of preoperative spherical equivalent refraction was +0.50 to +11.50 D (mean, +3.40 D). Mean postoperative spherical equivalent refraction at 6 months was +0.26 D. Six months after surgery, 35 eyes (44%) achieved uncorrected visual acuity of 20/20 or better and 78 eyes (97.5%) achieved 20/40 or better. Forty-six eyes (58%) had a postoperative spherical equivalent refraction within +/-0.50 D of attempted correction, and 67 eyes (84%) were within +/-1.00 D of attempted correction. When using the Bausch & Lomb Chiron Keracor 117C excimer laser to correct hyperopia, eyes with a spherical equivalent refraction less +2.00 D should be overcorrected by 25%, +2.00 to +4.00 D by 30%, and over +4.00 by 40%. The positive cylinder should be overcorrected by 10%. CONCLUSIONS LASIK was safe and effective in the treatment of hyperopia from +0.50 to +11.50 D. Regression following LASIK for hyperopia remains a problem. A special nomogram was required to achieve results comparable with those for myopia.

Treatment of progressive or recurrent epithelial ingrowth with ethanol following laser in situ keratomileusis

Abstract: Purpose To evaluate the use of ethanol in the treatment of progressive or recurrent epithelial ingrowth following laser in situ keratomileusis (LASIK). Methods Four eyes of four patients with aggressive epithelial ingrowth following LASIK underwent epithelial ingrowth removal with 50% ethanol. Aggressive epithelial ingrowth was defined as, 1) progressive enlargement on serial examination with an area of ingrowth involving at least 30% of the flap surface area, 2) epithelial ingrowth associated with stromal melting as evidence on clinical or topographic examination, or 3) recurrent epithelial ingrowth in the same area following previous removal. Results Epithelial ingrowth was removed successfully in all eyes. No eye lost best spectacle-corrected visual acuity. One eye with multiple risk factors for failure experienced nonprogressive recurrence. No eyes required reoperation for recurrent epithelial ingrowth. No eyes experienced progression of stromal melt. Regularization of corneal topography was observed in an eye with preoperative stromal melting. The only complication was a tendency for the development of diffuse lamellar keratitis. Two eyes (50%) experienced diffuse lamellar keratitis following epithelial ingrowth removal with ethanol, which resolved completely with topical corticosteroids. Conclusion Ethanol may be a useful adjunct in the treatment of aggressive or recurrent epithelial ingrowth following LASIK. Cautious use with the lowest concentration of ethanol may prove useful in these difficult epithelial ingrowth cases. Randomized and prospective studies are recommended to evaluate our experience.

Reversal of myopic anisometropic amblyopia with phakic intraocular lens implantation.

Abstract: PURPOSE To report a case of reversal of myopic anisometropic amblyopia with phakic intraocular lens implantation. METHODS A 6-year-old boy with anisometropic amblyopia with spherical equivalent refraction of right eye: -14.00 -3.00 x 100 degrees, left eye: -0.50 -3.25 x 90 degrees, was treated for 2 years with occlusion to the left eye, with poor results. Refractive surgery was planned because of contact lens intolerance at age 8 years. A -15.00-D iris claw Artisan intraocular lens (IOL) was implanted. RESULTS Following surgery, treatment of the amblyopia and spectacle correction of -4.00 D cylinder at 85 degrees in the right eye and -3.50 D cylinder at 90 degrees in the left eye was necessary. Visual acuity 6 months after surgery was 20/25 in the right eye and 20/20 in the left eye, and has remained stable 18 months after surgery. CONCLUSION Myopic anisometropic amblyopia in an 8-year-old boy was treated successfully with implantation of an Artisan iris claw phakic anterior chamber IOL, combined with occlusion therapy, and resulted in reversal of amblyopia.

Central necrotic lamellar inflammation after laser in situ keratomileusis.

Abstract: Purpose To report four cases of corneal interface complications that occurred after excimer laser in situ keratomileusis (LASIK). Methods Four eyes of three patients underwent technically uneventful LASIK. Results One day after LASIK, patients presented with severe pain, blurred vision, conjunctival infection, and diffuse opacity at the interface. Two days after LASIK, significant features were central opacity, striae in the flap, loss of uncorrected and best spectacle-corrected visual acuity, and corneal sensitivity. The findings did not improve by using drugs or by lifting the flap and irrigating the bed. The central opacity partially resolved over 8 to 12 months, leaving a hyperopic shift (one patient), striae (one patient), and loss of two or more lines of best spectacle-corrected visual acuity (three patients). Conclusion This severe central inflammation after LASIK could be an extreme manifestation of diffuse lamellar keratitis.

Epithelial and stromal changes induced by intacs examined by three-dimensional very high-frequency digital ultrasound.

Abstract: PURPOSE: To examine epithelial and stromal layers by three-dimensional very high-frequency (VHF) digital ultrasound scanning before and after implantation of Intacs (intracorneal ring segments [ICRS]). METHODS: Three-dimensional scanning was performed in five eyes before and 3 months after Intacs insertion. Digital signal processing techniques provided high-resolution B-scan imaging and I-scan traces for high-precision (1-microm) three-dimensional pachymetry. Thickness maps of individual corneal layers were constructed of the epithelium, stroma, and full cornea before and after surgery. Difference maps for epithelium and stroma were produced to examine anatomical changes in the thickness profile induced in each layer and correlate these to refractive changes. RESULTS: B-scan examination revealed stromal and epithelial anatomy anterior and adjacent to the Intac. Ring depth could be measured topographically. There was stromal lamellar displacement by the ring segments that produced a concave anterior stromal groove within an annulus central to the ring. Epithelial filling of this concavity was shown in three dimensions in such a way as to produce orthogonally asymmetrical flattening of the corneal surface, thus potentially accounting for induced astigmatism. Mapping of the central stroma demonstrated thickening, potentially also accounting for astigmatic changes ascribable to orthogonal asymmetry. CONCLUSIONS: VHF digital ultrasound scanning provided imaging and three-dimensional thickness mapping of corneal layers, enabling anatomical evaluation of the changes induced in the cornea by Intacs.

Anterior corneal optical aberrations induced by photorefractive keratectomy for hyperopia.

Abstract: PURPOSE Photorefractive keratectomy (PRK) for hyperopia requires both a steepening of the central cornea and a flattening of the mid-periphery to achieve its effect and is likely to affect the optical aberrations of the eye. METHODS Nine patients underwent PRK to correct between +2.00 and +4.00 D of hyperopia (first eye treated for each patient) using the Summit Technology Apex Plus excimer laser. Anterior corneal aberrations for pupil diameters of 3, 5.5 and 7 mm were estimated from corneal topography data (TMS-1), assuming a uni-index, single surface cornea. Refractive error was assessed using retinoscopy and standard subjective tests. RESULTS Apart from the intended change in refraction (mean spherical equivalent manifest refraction, +4.60 +/- 1.60 D before surgery and +0.70 +/- 1.60 D at 1 year after surgery), the most significant change was in spherical aberration. Anterior corneal spherical aberration was positive (+1.60 +/- 0.60 D for a 5.5-mm pupil) before surgery and became negative after surgery (-1.80 +/- 1.20 D at 1 year). The change in spherical aberration was related to the achieved change in refractive error. CONCLUSIONS The large change (approximately 3.00 D) in spherical aberration (from positive to negative aberration) has implications for the optical performance of the whole eye, where the effects of lenticular aberration must also be considered.

Change in intraocular pressure in myopic eyes measured with contact and non-contact tonometers after laser in situ keratomileusis.

Abstract: PURPOSE To study the change in the intraocular pressure (IOP) after laser in situ keratomileusis (LASIK) for correction of myopia. METHODS One hundred twenty consecutive myopic eyes (60 patients) were included in a prospective study. All eyes received LASIK with the Nidek EC-5000 excimer laser and the Chiron Automated Corneal Shaper. Baseline refraction, keratometry, pachymetry, ablation depth, and IOP measured by Goldmann applanation tonometry and non-contact air puff tonometry were correlated with the IOP change after surgery. Sixty healthy eyes of 30 subjects served as controls. RESULTS At 6 months, 108 eyes (90%) were examined. Compared to preoperative values, IOP decreased in 103 eyes (95.4%) when measured with applanation tonometry; it decreased in all eyes when measured with air puff tonometry. Mean change in IOP was -4.3 +/- 2.1 mmHg (range, -10.0 to +1.0 mmHg) with the applanation and -6.1 +/- 2.3 mmHg (range, -12.0 to -1.0 mmHg) with air puff tonometry. The IOP change measured with either instrument correlated significantly with the baseline IOP (P < .001) and the ablation depth (air puff, P < .001, applanation; P = .006). CONCLUSION Intraocular pressure decreased significantly after LASIK when measured with either Goldmann (mean 4.3 mmHg) or air puff (mean 6.1 mmHg) tonometers. This decrease may delay the diagnosis or affect the management of future glaucoma that may develop in a myopic eye that received LASIK.

Prevention of corneal ectasia in laser in situ keratomileusis.

Abstract: PURPOSE Ectasia after laser in situ keratomileusis (LASIK) is a rare but serious complication. Prevention includes proper patient selection with detection of those at particular risk. Causes of ectasia include predisposition, excessive ablation with less than 250 microm of residual stromal bed, thicker than normal flap, irregular corneal thickness, and different ablation rates. METHODS We evaluated corneal curvature patterns and their relationship to corneal topography and pachymetry maps. RESULTS Corneal topography (axial, tangential, and altimetric) and pachymetry map characteristics of normally astigmatic corneas, keratoconus, false-positive and false-negative cases, as well as contact lens-induced warpage are discussed. CONCLUSIONS Preoperative pachymetry maps for LASIK surgery allow accurate case selection through detection of borderline cases, and provide important documentation of preoperative status, as well as useful information for improving surgical strategy. Another important parameter is the asphericity index.

Surgical treatment of keratoconus at the turn of the 20th century.

Abstract: Purpose This paper reviews surgical modalities for treatment of keratoconus at the threshold of the 20th century. Methods All ophthalmic literature from 1895 until 1925 in English and German, available at the library of the Institute of Ophthalmology, London, United Kingdom, was studied with respect to this topic. Results Three thermal procedures were described; galvanocauterization with perforation, without perforation, and a non-contact application of heat to the corneal apex. Radial extension of a thermal burn to correct the minus cylinder represented a further modification. Excision of the conical area was suggested either as a lamellar dissection or as a full thickness trephination. Incision of the cone appeared to be less popular. In staged procedures, a combination of galvanocauterization, splitting of the cornea, conjunctival flap, and a subsequent optical iridectomy were applied. Conclusion The treatment of keratoconus 100 years ago used refractive surgery to improve visual function by modifying corneal shape.