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PubMed2003

Development of the National Eye Institute refractive error correction quality of life questionnaire: focus groups.

OBJECTIVE: To identify the content area for a questionnaire designed to measure the vision-targeted, health-related quality of life for persons with well-corrected refractive error. DESIGN: Cross-sectional study. PARTICIPANTS: Fifty-two focus groups were conducted with 414 patients from 5 geographically diverse ophthalmic and optometric sites to identify the content area of a questionnaire for use among persons with myopia and hyperopia. METHODS: A standard protocol was used to structure each focus group discussion, and groups were led by centrally trained moderators at each participating site. Results were summarized and analyzed using a standard set of codes. Qualitative and quantitative analyses were conducted. MAIN OUTCOME MEASURE: Self-reported observations or comments about vision, vision correction, and other aspects of quality of life. RESULTS: Among the 414 participants, 9262 mentions of comments were recorded. The most frequent comments reported by participants were about types of vision correction, followed by comments with their own vision and vision-related symptoms. The distribution of comments by topic domain was generally similar across types of correction and type of refractive error. The most frequent specific comments about glasses concerned problems with reading, adjustment between near and far vision, and appearance. The most frequent comments about contact lenses included those on symptoms such as dry eyes, itching and tired eyes, and headaches, and negative comments about ease of use. The most frequent comments among patients with surgical correction concerned fewer driving problems; fewer symptoms; and improvement in vision, recreation, and comfort. Participants provided equal numbers of positive and negative comments about glasses. Twice as many positive as negative comments were given by contact lens wearers, and 4 times as many positive comments were provided by patients who had undergone surgical correction. CONCLUSIONS: Using focus groups, we were able to identify content areas and aspects of visual functioning in persons with refractive error that are not measured by standard visual acuity testing in the clinic or by other vision-targeted, health-related quality of life instruments such as the 25- or 51-item National Eye Institute-Visual Functioning Questionnaire. The similarity of problems mentioned across refractive error type and correction method suggests it will be possible to develop a single questionnaire with adequate content validity to compare the impact of different modes of correction in vision-targeted, health-related quality of life.

Adult↗
PubMed2005

Presbyopia correction with an anterior chamber phakic multifocal intraocular lens.

PURPOSE: To investigate in a pilot study the potential of an anterior chamber phakic refractive multifocal intraocular lens (IOL) prototype for the correction of near and far vision in those with myopic and hyperopic presbyopia. DESIGN: A multicenter, open-label, prospective, noncomparative pilot evaluation. PARTICIPANTS: There were 17 patients (34 eyes), 16 women and 1 man, with a mean age of 52+/-3.94 years (range, 46-62 years). Six eyes were myopic (mean spherical equivalent [SE], -9.3+/-3.83 diopters (D)) and 28 were hyperopic (mean SE, +2.3+/-0.77 D), with astigmatism less than 1.5 D. METHODS: The prototype multifocal phakic IOL was implanted through a 6.5-mm temporal incision. The dominant eye was targeted for emmetropia and the nondominant eye for -1.0 D. MAIN OUTCOME MEASURES: The efficacy of the implant was assessed after surgery by measuring monocular and binocular uncorrected and distance-corrected visual acuity (VA) at distance, intermediate, and near, and distance-corrected near VA with near add. Distance-corrected distance and near VA also were determined in low contrast (25%). The safety index and efficacy index were calculated, and patient satisfaction questionnaires also were administered. Follow-up was at 1-3 days, 5-9 days, 21 days, 3 months, 6 months, and 1 year after surgery. RESULTS: Spherical equivalent refraction ranged from -11.75 to +4.25 D before surgery, and from -2.0 to +1.85 D 1 year after surgery. The binocular efficacy index was 0.68 (near) and 1.0 (distance), and the binocular safety index was 1.0 for both near and distance. Mean binocular uncorrected distance VA improved from 20/59 (+/-4 lines) before surgery to 20/18 (+/-1 line) 1 year after surgery. Mean binocular uncorrected intermediate VA improved from 20/125 (+/-10 lines) to 20/21 (+/-1 line), and mean binocular uncorrected near VA improved from 20/78 (+/-5 lines) to 20/32 (+/-1 line). Binocular uncorrected visual acuity was at least 20/40 (distance and intermediate) and Jaeger 3 in 88.2% of patients, and it was at least 20/40 and Jaeger 5 in 100% of patients. Patient satisfaction was very good in 88% of patients (15 of 17); the remaining 2 patients reported moderate satisfaction. CONCLUSIONS: Promising results were obtained with the refractive multifocal phakic IOL prototype investigated in this pilot study for near and far visual correction in presbyopia associated with myopia and hyperopia. Multifocal phakic intraocular optics may be an option for presbyopia correction.

Adult↗
PubMed2001

Cluster of Mycobacterium chelonae keratitis cases following laser in-situ keratomileusis.

PURPOSE: To describe a cluster of Mycobacterium chelonae keratitis cases involving patients who underwent laser in-situ keratomileusis (LASIK) at a single refractive surgery center. DESIGN: Descriptive case series of four patients and cohort study to identify disease associations. METHODS: Examination schedules, diagnostic tests, and therapy were based on best medical judgment. Isolates from three patients were compared by pulsed-field gel electrophoresis. Epidemiologic studies were performed to identify the source of infection. RESULTS: Seven of eight eyes developed M. chelonae keratitis following bilateral simultaneous LASIK. Each patient was thought to have diffuse lamellar keratitis initially, but all seven eyes were noted to have opacities suggestive of infectious keratitis by 13 to 21 days after surgery. All eyes had undergone hyperopic LASIK over four days in April 2001 by one surgeon in a community-based refractive surgery center. A cohort study of all patients undergoing LASIK at the same center in April 2001 revealed that M. chelonae keratitis occurred only in persons undergoing correction of hyperopia (seven of 14 eyes vs. none of 217 eyes undergoing myopic LASIK, P <.001). The only difference identified between procedures was use of masks created from a soft contact lens in hyperopic LASIK. Three isolates (three patients) were indistinguishable by pulsed-field gel electrophoresis. Eyes were treated with a combination of antimicrobial agents, including topical azithromycin in three patients, with resolution of infection in all eyes over 6 to 14 weeks. The source of infection was not identified on environmental cultures. CONCLUSION: Postoperative nontuberculous mycobacterial keratitis can occur in an epidemic fashion following LASIK. Topical amikacin, azithromycin, clarithromycin, ciprofloxacin, or a combination of these agents, appears to be effective treatment for these infections.

Anti-Bacterial Agents↗
PubMed2003

Corneal iron ring after conductive keratoplasty.

PURPOSE: To report formation of corneal iron ring deposits after conductive keratoplasty. DESIGN: Observational case report. METHODS: Case report. RESULTS: A 54-year-old woman underwent conductive keratoplasty for hyperopia. One year after conductive keratoplasty, iron ring pattern pigmentation was detected at the corneal epithelium of both eyes. CONCLUSIONS: This is the first report of the appearance of corneal iron ring deposits following conductive keratoplasty treatment in a patient. It is suggested that alterations in tear film stability, resulting from conductive keratoplasty-induced changes in corneal curvature, constitute the contributory factor for these deposits.

Cornea↗
PubMed1992

Preserved para-arteriolar retinal pigment epithelium retinitis pigmentosa.

In two patients, we studied retinitis pigmentosa with preservation of the retinal pigment epithelium adjacent to and under the retinal arterioles (despite panretinal degeneration). Both patients with preserved para-arteriolar retinal pigment epithelium also exhibited a peculiarly strong hyperopia. In addition to previously reported features, these patients also had sheathing of the major vascular arcades, which suggested a vascular involvement in this uncommon form of retinitis pigmentosa.

Adult↗
PubMed2001

Making sense of refractive surgery in 2001: why, when, for whom, and by whom?

Surgical alteration of the focusing or refractive properties of the eye has been performed on millions of patients. An array of procedures to correct myopia, hyperopia, astigmatism, and presbyopia have been introduced over the past 25 years with varying degrees of success. Improved technology has increased patient and physician satisfaction and enthusiasm. Currently available surgical procedures can be categorized as incisional, surface-altering, lamellar, and intraocular. The choice of procedure depends on individual patient indications and contraindications based on results of ocular examinations, eg, corneal pachymetry to measure corneal thickness, keratometry to measure the corneal curvature, basal tear secretory rate, and dark-adapted pupil size. The postoperative uncorrected visual acuity depends, in large part, on the quality of the preoperative evaluation and refraction. Before scheduling a patient for surgery, the ophthalmologist must ensure that the patient understands the potential risks of the procedure and has realistic expectations for the postoperative level and quality of uncorrected visual acuity. Postoperative complications include corneal flap displacement, undercorrection and overcorrection, and epithelial ingrowth under the corneal flap and inflammatory keratitis. Postoperative dry eye, infection, and inflammation are usually treated medically. Ongoing technological innovations to customize the surgical approach to an individual patient's eye continue to improve outcomes.

Astigmatism↗
PubMedDate not supplied

Dynamic retinoscopy: the missing data.

Dynamic retinoscopy is a well described but often overlooked technique that allows rapid assessment of accommodative ability. The key to the technique is the neutralization of the retinoscopic reflex that occurs when the patient accommodates on a target adjacent to the retinoscope. This clinical tool can provide critical data that can help solve treatment dilemmas, such as when a child presents with high hyperopia or when a patient presents at any age with possible accommodative insufficiency. In this review, performance of dynamic retinoscopy will be detailed, with the applicability of the technique demonstrated with use of case examples.

Accommodation, Ocular↗
PubMed2000

Diurnal illumination patterns affect the development of the chick eye.

Exposure to continuous illumination disrupts normal ocular development in young chicks, causing severe corneal flattening, shallow anterior chambers and progressive hyperopia ('constant light (CL) effects'). We have studied the minimum requirements of a diurnal light cycle to prevent CL effects. (1) Seven groups of 10 chicks were reared under a 0 (constant light, CL), or 1, 2, 3,4, 6, or 12/12 h (normal) light-dark cycles. It was found that CL effects were prevented if the dark period was 4 h or longer. Below 4 h, the effects were dose-dependent and inversely correlated with the amplitude of the Fourier component of illumination at 1 cycle per day (CPD). (2) Three groups of 20 chicks were exposed to 4 h of darkness distributed differently over 24 h to vary the amplitude of the Fourier component at 1 CPD. It was found that complete suppression of the CL effects required that the 4 h of darkness were given in one block and at the same time each day. Our results show that normal ocular development in the chick requires a minimum of 4 h darkness per day, provided at the same time of the day without interruption, and suggest that the light-dark cycle interacts with a linear or weakly nonlinear oscillating system.

Animals↗
PubMed2001

Overnight lens removal avoids changes in refraction and eye growth produced by plano soft contact lenses in infant marmosets.

Infant marmosets were fitted with zero-powered (plano) soft contact lenses from 4 to 8 weeks of age worn either continuously (24 h per day) (n = 4), for 12 h (n = 4), or for 8 h (n = 3) per day to determine whether limiting the daily duration of lens-wear could significantly reduce or eliminate the effects of continuous lens-wear on ocular growth and refractive state. As in macaques (Hung, L. F., & Smith, E. L. (1996). Extended-wear, soft, contact lenses produce hyperopia in young monkeys. Optometry and Vision Science, 73, 579-584), eyes fitted with contact lenses worn continuously developed more hyperopic refractions (mean +3.22 +/- 1.49 D SE) compared to their fellow untreated eyes, inconsistent changes in vitreous chamber depth (-0.02 +/- 0.09 mm SE) and flatter corneas (mean decrease in corneal power 4.22 +/- 0.39 D SE). Eyes wearing lenses for only 12 h per day showed similar but reduced effects compared to the 24-h group. Most importantly, ocular growth, corneal power and refraction were unaffected in the 8-h group. Future studies using contact lenses in infant primates should employ a reduced daily duration of lens-wear to eliminate the undesirable effect of contact lens-wear per se on ocular development.

Analysis of Variance↗
PubMed2001

Refractive state and accommodation in the eyes of free-swimming versus restrained juvenile lemon sharks (Negaprion brevirostris).

Optical measurements of the refractive state of the eyes of various shark species typically have depicted sharks as hyperopic (far-sighted) with little evidence of accommodation (i.e. the ability to change focus for visualizing objects at different distances from the eye). In this study, we used infrared video retinoscopy to measure the refractive state in juvenile lemon sharks (Negaprion brevirostris). This technique allows dynamic measurement of refractive state in free-swimming animals as they pass by an aquarium window. We found that unrestrained lemon sharks are focused emmetropically relative to a 1-m distant photorefractor for the lateral visual field. However, when restrained either right side up or upside down (the latter inducing tonic immobility), the sharks become increasingly hyperopic, an artifact also reported in some other vertebrates. In addition, unrestrained lemon sharks display small amplitude accommodative excursions. Thus, refractive state measurements on restrained sharks in general may not reflect the natural, resting state of the shark eye, but rather, an induced hyperopia and lack of accommodative function. Such an artifact may be present in other vertebrate species, underscoring the need to obtain measurements of refractive state in unrestrained animals.

Accommodation, Ocular↗
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↗
PubMed2002

Effect of hyperopic laser in situ keratomileusis on ocular alignment and stereopsis in patients with accommodative esotropia.

OBJECTIVE: To evaluate the effect of laser in situ keratomileusis (LASIK) on ocular alignment and stereopsis in patients with accommodative esotropia. DESIGN: Retrospective, non-comparative, interventional case series. PARTICIPANTS: Since 1998, 27 patients (mean age, 33.3 years; range, 10-52 years) with comitant esophoria or esotropia and hyperopia meeting eligibility requirements underwent bilateral LASIK for correction of refractive error. INTERVENTION: Bilateral hyperopic LASIK was performed using the Technolas Keracor 217 excimer laser (Bausch & Lomb) in 22 patients and using the Nidek 5000 excimer laser in 5 patients. MAIN OUTCOME MEASURES: Visual acuity (best-corrected and uncorrected), refractive error, ocular alignment, and stereopsis were recorded before and after LASIK. Log transformation of each visual acuity was done before data analysis. RESULTS: Using paired t tests, the mean uncorrected esotropia was significantly reduced from 9.0 prism diopters (PD) (range, 0 [esophoria only] to 20 PD; standard deviation [SD], 7.39) before surgery to 3.3 PD (range, 0-15 PD; SD, 6.20) after surgery (P < 0.0001). Most patients (14 patients, 58%) had a reduction in esodeviation after LASIK, but 10 patients (42%) had no response to surgery, and these patients could not be predicted on the basis of preoperative sensorimotor testing. No patient had a worsening sensorimotor status after LASIK. Nine patients subsequently underwent conventional eye muscle surgery. CONCLUSIONS: Hyperopic LASIK was effective in reducing the mean uncorrected esotropia in this group of patients. However, accurately determining those patients most likely to benefit from the procedure was difficult.

Accommodation, Ocular↗
PubMed2003

Outcome after treatment of ametropia with implantable contact lenses.

OBJECTIVE: To evaluate long-term results after insertion of implantable contact lenses (ICLs) in phakic eyes. DESIGN: Prospective, noncomparative, interventional case series. PARTICIPANTS: Seventy-five phakic eyes (65 myopic, 10 hyperopic eyes) of 45 patients aged 21.7 to 60.6 years were included. INTERVENTION: STAAR Collamer Implantable Contact Lenses (STAAR Surgical Inc., Nidau, Switzerland) were implanted for correction of high myopia and hyperopia. MAIN OUTCOME MEASURES: Uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), and intraocular pressure (IOP) were determined. Presence of lens opacification and the distance between the ICL and the crystalline lens were assessed by slit-lamp examination before surgery and at 1, 3, 6 months, and yearly after lens implantation. RESULTS: Preoperative mean spherical equivalent was -16.23+/-5.29 diopters (D) for myopic eyes and +7.88 +/-1.46 D for hyperopic eyes. After ICL implantation, mean residual refractive error was -1.77+/-2.17 D in myopic patients and +0.44+/-0.69 D in hyperopic patients. Preoperative mean UCVA was Snellen 0.03+/-0.03 for myopic patients and Snellen 0.12+/-0.16 for hyperopic patients. Preoperative mean BCVA was Snellen 0.49+/-0.23 for myopic patients and Snellen 0.82+/-0.23 for hyperopic patients. After ICL implantation, mean UCVA up to the end of individual observation time was Snellen 0.36+/-0.36 for myopic patients and Snellen 0.58+/-0.28 for hyperopic patients. Mean BCVA was Snellen 0.73+/-0.26 for myopic and Snellen 0.80+/-0.24 for hyperopic patients. Mean preoperative IOP was 14.2+/-2.7 mmHg, and mean postoperative IOP was 13.46+/-2.1 mmHg over all follow-up investigations. The main complication was the development of subcapsular anterior opacifications of the crystalline lens in 25 eyes (33.3%), 2 of which showed direct contact to the ICL. Eleven eyes (14.7%) were stable in opacification and 14 eyes (18.7%) had progressive opacifications. The median time to opacification was 27.1 months. In 8 patients (10.7%), the subjective visual impairment mandated cataract surgery. CONCLUSIONS: The most significant long-term complication after ICL implantation is the formation of opacifications of the crystalline lens with the risk of the necessity of subsequent cataract surgery (10.7%). Old age, female gender, and contralateral opacification are independent significant risk factors for early formation of opacifications in this patient group.

Adult↗
PubMed1981

Keratophakia and keratomileusis--clinical results.

A random, retrospective study was performed on 158 patients. who underwent keratophakia and keratomileusis for the correction of refractive errors. The primary indication for surgery was high anisometropia. Data on corneal curvature modification, refraction, accuracy, stability, and complications are reported. Both keratophakia and hypermetropic keratomileusis are capable of fully correcting aphakic hyperopia. Myopic keratomileusis corrected up to 16 diopters of myopia in this series. Lamellar refractive keratoplasty appears to have no significant detrimental effect on visual acuity. The majority of myopic patients had an improved best-corrected visual acuity postoperatively. High or irregular astigmatism was not noted following this surgery. The stability of the postoperative curvature appeared to be good with both keratophakia and myopic keratomileusis. Complications in this series were minimal, and one resulted in decreased vision postoperatively. Inaccuracy in achieving the desired refractive result appeared to be the major disadvantage of these techniques.

Adolescent↗
PubMed1996

Anisometropia and binocularity.

PURPOSE: To determine the effects of experimentally induced anisometropia on binocular function in healthy adults as a means of assessing the potentially detrimental effects of uncorrected anisometropia on binocular development in childhood. METHODS: Nineteen adults with normal binocularity, ranging in age from 26 to 59 years, were studied. Unilateral myopia, hyperopia, or astigmatism (at 90 degrees or 45 degrees) was induced in each subject using trial lenses. Sensory status then was assessed by measuring stereoacuity, Worth four-dot fusion, and Bagolini lens response. RESULTS: All subjects showed a decline in binocular function with increasing levels of anisometropia. Foveal suppression was evident on the Worth four-dot test, and increased in proportion to the anisometropia. Stereoacuity was similarly degraded by the induced anisometropia, with some subjects showing significant loss of stereoacuity with as little as 1 diopter of spherical anisometropia. Bagolini lens responses were binocular in almost all patients, although occasional abnormalities were found. CONCLUSIONS: Relatively low degrees of anisometropia may cause significant abnormalities in high-grade binocular visual functions in adults. The potential effects of uncorrected anisometropia on binocularity in children require further investigation, but should be considered in developing guidelines for the empiric correction of refractive errors.

Adult↗
PubMed1996

Preliminary results of photorefractive keratectomy in active-duty United States Navy personnel.

PURPOSE: To evaluate the safety, efficacy, and quality of vision after photorefractive keratectomy (PRK) in active-duty military personnel. METHODS: Photorefractive keratectomy (6.0-mm ablation zone) was performed on 30 navy/marine personnel(-2.00 to -5.50 diopters [D]; mean, -3.35 D). Glare disability was assessed with a patient questionnaire and measurements of intraocular light scatter and near contrast acuity with glare. RESULTS: At 1 year, all 30 patients had 20/20 or better uncorrected visual acuity with no loss of best-corrected vision. By cycloplegic refraction, 53% (16/30) of patients were within +/- 0.50 D of emmetropia and 87% (26/30) were within +/- 1.00 D. The refraction (mean +/- standard deviation) was +0.45 +/- 0.56 D (range, -1.00 to 1.63 D). Four patients (13%) had an overcorrection of more than 1 D. Glare testing in the early (1 month) postoperative period demonstrated increased intraocular light scatter (P<0.01) and reduced contrast acuity (with and without glare, (P<0.01). These glare measurements statistically returned to preoperative levels by 3 months (undilated) and 12 months (dilated) postoperatively. Two patients reported moderate to severe visual symptoms (glare, halo, night vision) worsened by PRK. One patient had a decrease in the quality of night vision severe enough to decline treatment in the fellow eye. Intraocular light scatter was increased significantly (>2S D) in this patient after the procedure. CONCLUSIONS: Photorefractive keratectomy reduced myopia and improved the uncorrected vision acuity of all patients in this study. Refinement of the ablation algorithm is needed to decrease the incidence of hyperopia. Glare disability appears to be a transient event after PRK. However, a prolonged reduction in the quality of vision at night was observed in one patient and requires further study.

Adult↗
PubMed2000

Paracentral photoablations to correct higher grades of naturally occurring astigmatism.

PURPOSE: To evaluate the efficacy of paracentral ablations in treating higher degrees of naturally occurring myopic and hyperopic astigmatism. SETTING: Augenklinik, Kreiskrankenhaus Bad Hersfeld, Germany. METHODS: Twenty-five eyes (7 with hyperopia, 18 with myopia) with naturally occurring corneal astigmatism greater than 1.75 diopters (D) were treated by excimer laser. The mean refractive cylinder was -4.05 D +/- 1.46 (SD) (range -1.75 to -7.00 D). The intention was to reduce the astigmatism without consideration of the spherical refractive error. Two paracentral ablations were performed by photorefractive keratectomy with treatment zones of 3.5 mm in the flatter meridian of the cornea. Objective refraction, best corrected visual acuity (BCVA), changes in corneal radius, development of haze, and regression were recorded. RESULTS: The paracentral ablations induced a steepening of the corneal radius in the flatter meridian from 8.12 mm (mean preoperative value) to 7. 84 mm (mean postoperative value) and thus reduced the mean refractive cylinder to -1.12 +/- 0.82 D (range 0.00 to - 3.00 D), corresponding to a mean reduction of 78%. No eye experienced a loss of Snellen lines. The preoperative BCVA (mean 20/25; range 20/50 to 20/20) was unchanged postoperatively CONCLUSIONS: Paracentral ablations resulted in a stable corneal curvature immediately after epithelial healing, with a moderate regression over time. Paracentral ablations with the excimer laser appear to be a safe and effective method to correct higher grades of corneal astigmatism.

Adult↗
PubMed2001

Surgically induced astigmatism after hyperopic and myopic photorefractive keratectomy.

PURPOSE: To compare the axis and magnitude of surgically induced refractive astigmatism (SIA) after hyperopic and myopic photorefractive keratectomy (PRK). SETTING: Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA. METHODS: In this single-center retrospective study, the VISX Star S2 excimer laser was used to create a peripheral annular ablation profile to correct spherical hyperopia in 23 eyes of 16 consecutive patients. Attempted corrections ranged from +0.50 diopter (D) to +4.25 D with 0 to 1.00 D of astigmatism. The same laser was used to create a central ablation profile to correct spherical myopia in 25 eyes of 17 consecutive patients. Attempted corrections ranged from -2.25 to -6.50 D with 0 to 1.00 D of astigmatism. The absolute change in refractive astigmatism was calculated by taking the difference in magnitudes of astigmatism before and after laser treatment without regard to axis. Axis and magnitude of SIA were analyzed by vector differences. Magnitudes were compared using the Student t test, and axial shifts were compared using the chi-square test. All patients were followed for a minimum of 6 months. RESULTS: The mean changes in absolute astigmatism were 0.29 +/- 0.28 D at 3 months and 0.34 +/- 0.29 D at 6 months after hyperopic PRK and 0.40 +/- 0.35 D at 3 months and 0.39 +/- 0.36 D at 6 months after myopic PRK. The mean vectoral magnitudes were 0.49 +/- 0.29 at 3 months and 0.52 +/- 0.25 at 6 months after hyperopic PRK and 0.48 +/- 0.39 at 3 months and 0.44 +/- 0.38 at 6 months after myopic PRK. The mean values for SIA (the centroid) were 0.10 +/- 0.57 D x 113 degrees at 3 months and 0.15 +/- 0.57 D x 131 degrees at 6 months after hyperopic PRK and 0.04 +/- 0.63 D x 160 degrees at 3 months and 0.08 +/- 0.58 D x 171 degrees at 6 months after myopic PRK. There was no statistically significant difference between the 2 groups in vectoral axis or magnitude of SIA. CONCLUSION: Surgically induced astigmatism after hyperopic PRK was comparable to astigmatism induced by myopic PRK. A peripheral annular ablation for hyperopic correction, similar to a central ablation in myopic PRK, did not appear to result in uneven corneal healing causing astigmatism.

Astigmatism↗