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PubMed2002

Anisometropia and degree of optic nerve damage in chronic open-angle glaucoma.

PURPOSE: To address the question of whether the refractive error plays a role in the amount of optic nerve damage in glaucoma, we intraindividually compared inter-eye differences in refractive error with inter-eye differences in parameters indicating the degree of glaucomatous optic nerve damage, and we interindividually correlated refractive error with neuroretinal rim area and visual field loss. DESIGN: Comparative clinical observational study. METHODS: This comparative clinical observational study was conducted in a university eye hospital. The study included 1,444 eyes of 876 patients with primary or secondary chronic open-angle glaucoma. Patients with a highly myopic refractive error (> or = -8 diopters) were excluded, owing to differences in the anatomy of the optic nerve head. Color stereo optic disk photographs were taken and morphometrically evaluated. The main outcome measures were refractive error, neuroretinal rim area, horizontal and vertical cup/disk diameter ratios, and visual field loss. RESULTS: In an interindividual statistical analysis, area of neuroretinal rim, horizontal and vertical cup/disk diameter ratios, and mean visual field loss were not significantly (P >.10) correlated with refractive error. In an intraindividual comparison, inter-eye differences in refractive error were not significantly (P >.05) correlated with inter-eye differences in neuroretinal rim area and mean visual field defect. The eye with the more myopic refractive error and the contralateral eye with the less myopic refractive error did not vary significantly in neuroretinal rim area and mean visual field defect. CONCLUSIONS: For nonhighly myopic (< -8 diopters) patients with primary or secondary chronic open-angle glaucoma, the refractive error may not play a major role for the amount of glaucomatous optic neuropathy. For nonhighly myopic (< -8 diopters) patients with primary or secondary chronic open-angle glaucoma, myopia may not be an important risk factor for glaucoma.

Adolescent↗
PubMed2006

The Refractive Status and Vision Profile (RSVP): Translation into Persian, reliability and validity.

PURPOSE: To translate and test the reliability and validity of a Persian translation of the Refractive Status and Vision Profile (RSVP), a vision-related quality of life questionnaire, in Iran. METHODS: Forward & backward translation, committee review and pilot testing were performed to develop a final Iranian version of the RSVP. Seventy-three consecutive patients with refractive error before or after refractive surgery at the LASIK ward of Farabi Eye Hospital completed the questionnaire. A convenience sample of 14 patients completed the questionnaire twice within one week. Reliability was measured by internal consistency (Cronbach's alpha) and the intraclass correlation coefficient for test-retest reliability. Validity was evaluated by correlation between the different RSVP subscales, known groups comparison analysis, and correlation between the subscales versus global items and traditional clinical measures. RESULTS: Internal consistency was high (Cronbach's alpha : 0.71-0.92; except for the subscale expectations, alpha : 0.6). Test-retest reliability of subscales and the overall RSVP scale, as estimated by the intraclass correlation coefficient, was high except for optical problems and glare. Comparisons between pre- and post-operative groups of patients showed significantly higher (worse) scores for concern, physical/social functioning, and the overall score in the pre-operative group. Almost all subscales showed desirable inter-scale correlations. CONCLUSION: The Iranian version of the RSVP is a reliable and valid measure of vision-related quality of life in patients with refractive error.

Adult↗
PubMed1991

The distribution of dioptric power: ellipsoids of constant probability density.

A sample from a population of dioptric powers may be used to estimate the distribution of dioptric powers in the population itself. This paper describes the method and shows further how one can obtain a graphical representation of the distribution. The graphical representation takes the form of ellipsoids of constant probability density. The centroid of each ellipsoid estimates the mean of the population while the size, shape and orientation show the extent and nature of the spread of the population. For illustrative purposes the theory is applied to measurements of refractive status before and after radial keratotomy. The ellipsoids are presented as stereo-pairs. They are useful for comparative and predictive purposes. Thus the ellipsoid that contains 95% of the population after surgery defines the set of refractive errors within which the refractive error of a particular eye can be expected to fall with a probability of 95%.

Humans↗
PubMedDate not supplied

Corneal shape in hyperopia.

Background: A trend towards decreased peripheral corneal flattening with increasing myopia has recently been demonstrated. The present study was conducted to determine whether corneal asphericity also varies significantly with hyperopic refractive error. Methods: Thirty-five eyes with spherical equivalent refractive error ranging from -0.37 D to +6.00 D were examined. A conicoid equation was fitted to videokeratoscopic (Topographic Modeling System) data and corneal asphericity and apical radius of curvature values were calculated for each subject. Axial length measurements were made using a hand-held biometric ruler. Keratometry was also performed on each eye. Results: The relationship between corneal asphericity (Q) and spherical equivalent refractive error was not statistically significant (p = 0.7419). In addition, no association could be demonstrated between Q and corneal radius of curvature or between Q and axial length. Corneal radius of curvature was positively correlated with axial length (r = 0.367, p = 0.0298). Axial length was found to decrease as hyperopic refractive error increased (r = 0.753, p = 0.0001). Conclusions: For hyperopic eyes, corneal asphericity does not appear to be significantly correlated with refractive error, a finding that is at variance with previous data for myopic eyes showing an association between these two variables. The results suggest that there may be differences between hyperopic and myopic eyes with regard to the anterior segment changes that occur during refractive error development.

Journal Article↗
PubMed1993

Hyperopia as a risk factor for nonarteritic anterior ischemic optic neuropathy.

The most convincing morphologic component in the pathogenesis of nonarteritic anterior ischemic optic neuropathy is the anatomically small and crowded optic nerve head. Because the appearance of the optic disk is presumed to be related to underlying refractive error, we sought to determine if a particular refractive error places patients at additional risk for, or affords protection from, nonarteritic anterior ischemic optic neuropathy. We compared refractive errors of 50 patients with nonarteritic anterior ischemic optic neuropathy to an age-matched and eye-matched control population. The mean refractive error (in spherical equivalents) for the nonarteritic anterior ischemic optic neuropathy group was +0.26 diopter (SD +/- 2.08); the mean refractive error for controls was -0.86 diopter (SD +/- 2.91) (P = .027). Our results suggest that patients who have nonarteritic anterior ischemic optic neuropathy are less myopic than a control population. Whether it is myopia that protects from, or hyperopia that predisposes to nonarteritic anterior optic neuropathy, our results imply another anatomically based factor that characterizes eyes that develop nonarteritic anterior ischemic optic neuropathy. Those eyes tend to be minimally hyperopic.

Arteritis↗
PubMed1993

Hyperopia and neovascularization in age-related macular degeneration.

PURPOSE: Refractive errors for phakic eyes of patients referred with age-related macular degeneration were reviewed to determine whether some range of refractive error might be a risk factor for the neovascular form. METHODS: The authors compared refractive errors of 198 patients with unilateral neovascular disease with refractive errors of 129 patients with bilateral dry disease. These groups had comparable distributions with respect to age, sex, and visual acuity of their better eyes. Student's t tests and multiple linear regression analyses were performed to assess group differences in mean refractive error. Contingency table and multiple logistic regression analyses were performed to determine odds ratios for having the neovascular form based on a stratification of refractive error. RESULTS: By comparing better eyes of the two groups, patients with the unilateral neovascular form had an average spherical equivalent that was 1.0 diopter (D) more hyperopic than that of patients with the bilateral dry form (P < 0.001). Patients with a refractive error of +0.75 D or greater were more likely to have the neovascular form compared with patients with other refractive errors (odds ratio, 2.40; 95% confidence interval, 1.53-3.78; P < 0.001). Similar relationships between the two groups of patients were found by comparing worse eyes. CONCLUSION: These findings suggest that hyperopia is a risk factor for choroidal neovascularization among patients referred with age-related macular degeneration.

Aged↗
PubMed1982

Component and correlation ametropia.

The average axial length for eyes grouped according to refractive error must vary as a function of refractive error. In fact, this change in the average axial length can account almost totally for the change in refractive error. This finding is incompatible with the usual interpretation of correlation ametropia. When the categorization of eyes is based on axial length rather than on refractive error, then a more statistically meaningful division of eyes into component and correlation categories is achieved.

Analysis of Variance↗
PubMed2002

Blur detection thresholds in childhood myopia: single and dual target presentation.

There is some suggestion that the ability to detect blur may be altered in adults with myopia. Here, we address the question of whether children with myopia have worse blur detection than other children, and whether blur detection in myopic children is related to the rate of myopia progression. We recruited 20 myopes and 20 non-myopes aged between 8 and 12 years. Refractive errors, visual acuity, and contrast sensitivity were measured and the change in refractive error over the past year calculated from clinic records. Blur detection thresholds for two different types of black and white targets (text and scenes), two illumination conditions and two testing protocols were determined using a computer-based forced-choice testing procedure. The two testing protocols used were: (i) dual image presentation where subjects were asked to choose the clearer of the two images, one image always having zero blur, and (ii) single image presentation in which the subject reported whether the image was clear or blurred. Blur discrimination ability under all tested conditions was similar for both refractive error groups. Blur detection thresholds were 0.27+/-0.15 D (myopes) and 0.24+/-0.07 D (non-myopes) for text images. Thresholds were similar when measured with a one log unit reduction in lighting: 0.27+/-0.31 D compared to 0.23+/-0.14 D. Blur detection thresholds were greater for photographic scenes (myopes 0.41+/-0.36 D, non-myopes 0.44+/-0.36 D) and when only a single text image (myopes 0.51+/-0.21 D, non-myopes 0.59+/-0.01 D) was presented, but this increase was measured in both refractive error groups. There was no correlation between blur thresholds and refractive error magnitude, refractive error progression over the past year, or contrast sensitivity. We found that the blur detection ability showed greater individual variation in myopic children. Further work is required to determine whether blur detection ability is of relevance to myopia development.

Accommodation, Ocular↗
PubMed2005

Long-term outcomes of photorefractive keratectomy for anisometropic amblyopia in children.

PURPOSE: To evaluate the long-term visual acuity (VA) and refractive error responses to excimer laser photorefractive keratectomy (PRK) for treatment of anisometropic amblyopia in children. DESIGN: Prospective interventional case-control study. PARTICIPANTS: Eleven children, 2 to 11 years old, with anisometropic amblyopia who were noncompliant with conventional therapy with glasses or contact lenses and occlusion therapy were treated with PRK. A cohort derived retrospectively of 13 compliant and 10 noncompliant children with refractive errors similar to those of the PRK group who were treated with traditional anisometropic amblyopia therapy served as control groups. INTERVENTION: Photorefractive keratectomy for the eye with the higher refractive error. MAIN OUTCOME MEASURES: (1) Refractive error reduction and stability in the treated eye, (2) cycloplegic refraction, (3) VA, (4) stereoacuity, and (5) corneal haze up to 3 years after PRK. Compliant and noncompliant children with anisometropia amblyopia were analyzed as controls for refractive error and VA. RESULTS: Preoperative refractive errors were -13.70 diopters (D) (+/-3.77) for the myopic group and +4.75 D (+/-0.50) for the hyperopic group. Mean postoperative refractive errors at last follow-up (mean, 31 months) were -3.55 D (+/-2.2.5) and +1.41 D (+/-1.07) for the myopic and hyperopic groups, respectively. At last follow-up, cycloplegic refractions in 4 (50%) of 8 myopes and all hyperopes (100%) were within 3 D of that of the fellow eye. Five (63%) of 8 myopic children achieved a refraction within 2 D of the target refraction. Two (67%) of 3 hyperopic patients maintained their refractions within 2 D of the target. Refractive regressions (from 1 year after surgery to last follow-up) were 0.50+/-1.41 D (myopes) and 0.60+/-0.57 D (hyperopes). Seven children (77%) were able to perform psychophysical VA testing preoperatively and postoperatively. Five (71%) of the 7 children had uncorrected VA improvement of at least 2 lines, and 4 (57%) of 7 had best spectacle-corrected VA improvement of at least 2 lines, with 1 improving 7 lines. Five (55%) of 9 children had improvement of their stereoacuity at last follow-up. Subepithelial corneal haze remained negligible. The mean final VA of the PRK group was significantly better than that of the noncompliant control group (P = 0.003). The mean final refractive error for both myopic and hyperopic groups was also significantly better that that of the control groups (P = 0.007 and P<0.0001, respectively). CONCLUSIONS: Photorefractive keratectomy for severe anisometropic amblyopia in children resulted in long-term stable reduction in refractive error and improvement in VA and stereopsis, with negligible persistent corneal haze.

Amblyopia↗
PubMed1994

Comparison of cycloplegic and noncycloplegic retinoscopy in Chinese pre-school children.

Twenty-seven Hong Kong Chinese children, aged 3 to 5 1/2 years, were recruited in this study to evaluate the relation between refractive error as measured retinoscopically before and after cycloplegia using cyclopentolate 1%. The noncycloplegic spherical refractive error of these children ranged from -0.75 to +2.50 D and approximately 98% of the Hong Kong pre-school children have a manifest spherical error within this range. The cycloplegic refractive error can be approximated by multiplying the spherical component of the manifest error by 1.45 and adding +0.39 D to the product, while keeping the astigmatic power and axis unchanged. Cyclopentolate 1% requires more time to produce mydriasis and cycloplegia in eyes with heavily pigmented irides; however, its final effect on refractive error is apparently independent of iris pigmentation and depends on the amount of spherical refractive error present.

Accommodation, Ocular↗
PubMed1999

Naturally occurring vitreous chamber-based myopia in the Labrador retriever.

PURPOSE: To investigate whether myopia is present in a breed of domestic dog, the Labrador retriever, and how the ocular components are related to refractive error in this breed. METHODS: Cycloplegic refractive error was measured in 75 Labrador retrievers by retinoscopy. Corneal and crystalline lens radii of curvature were measured in the right eyes of 57 of these dogs using a video-based keratophakometer, with axial ocular dimensions measured using A-scan ultrasonography. RESULTS: Of the 75 dogs tested, 11 (14.7%) were myopic by at least -0.50 D in one eye, and 6 (8.0%) were myopic in both eyes (full range of refractive errors, +3.50 D to -5.00 D). Of the 57 dogs with ocular component measurements, seven (12.3%) were myopic by at least -0.50 D in the right eye. There was a significant negative correlation between refractive error and vitreous chamber depth (Spearman r = -0.42; P < 0.001). Myopic eyes had an elongated vitreous chamber depth (10.87+/-0.34 mm for myopic dogs, 10.02+/-0.40 mm for nonmyopic dogs; P < 0.0001, Kruskal-Wallis test). There was also a significant quadratic association between lens thickness and vitreous chamber depth (P < 0.005; R2 = 0. 11), indicating that thinner lenses occurred at both shorter and longer vitreous chamber depths. CONCLUSIONS: Myopia in the Labrador retriever is analogous to human myopia in that it is caused by an elongated vitreous chamber. Thinner crystalline lenses found at longer vitreous chamber depths may be analogous to lens thinning documented in human ocular development. The Labrador retriever warrants investigation as a potential model of myopia that is naturally occurring rather than experimentally induced.

Animals↗
PubMed2005

Axial growth and changes in lenticular and corneal power during emmetropization in infants.

PURPOSE: To evaluate the contribution made by the ocular components to the emmetropization of spherical equivalent refractive error in human infants between 3 and 9 months of age. METHODS: Keratophakometry in two meridians was performed on 222 normal-birthweight infant subjects at 3 and 9 months of age. The spherical equivalent refractive error was measured by cycloplegic retinoscopy (cyclopentolate 1%). Anterior chamber depth, lens thickness, and vitreous chamber depth were measured by A-scan ultrasonography over the closed eyelid. RESULTS: Both the mean and SD for spherical equivalent refractive error decreased between 3 and 9 months of age (+2.16 +/- 1.30 D at 3 months; +1.36 +/- 1.06 D at 9 months; P < 0.0001, for the change in both mean and SD). Average ocular component change was characterized by increases in axial length, thinning, and flattening of the crystalline lens, increases in lens equivalent refractive index, and decreases in lens and corneal power. Initial refractive error was associated in a nonlinear manner with the change in refractive error (R(2) = 0.41; P < 0.0001) and with axial growth (R(2) = 0.082; P = 0.0005). Reduction in hyperopia correlated significantly with increases in axial length (R(2) = 0.16; P < 0.0001), but not with changes in corneal and lenticular power. Decreases in lenticular and corneal power were associated with axial elongation (R(2) = 0.40, R(2) = 0.12, respectively; both P < 0.0001). CONCLUSIONS: Modulation in the amount of axial growth in relation to initial refractive error appeared to be the most influential factor in emmetropization of spherical equivalent refractive error. The associations between initial refractive error, subsequent axial growth, and change in refractive error were consistent with a visual basis for emmetropization. The cornea and crystalline lens lost substantial amounts of dioptric power in this phase of growth, but neither appeared to play a significant role in emmetropization.

Accommodation, Ocular↗
PubMed1996

A new subjective refraction method--the meridional polarized vernier optometer.

BACKGROUND: The purpose of this study was to develop a more accurate and precise method for measuring subjective sphero-cylindrical refractive errors. It employed the principles of a vernier optometer and meridional refraction. METHODS: A meridional polarized vernier optometer was used to measure the refraction of three subjects. Trial lenses were added to change the refractive error by known amounts and refractions were repeated to assess accuracy. RESULTS: Refractions were within the range expected. The instrument had a slight bias (+0.04D) and 95 percent confidence interval of +/- 0.45D for measuring change in refractive error. Mean standard deviation for repeated measurements was 0.08D. CONCLUSIONS: This new approach has the potential to measure subjective refractive errors more accurately than is possible with current methods.

Adult↗
PubMed2002

Biometry of the silicone oil-filled eye: II.

PURPOSE: In phakic silicone oil-filled eyes, removal of the silicone oil can be combined with phacoemulsification and intraocular lens (IOL) implantation. True axial length (AL) of the silicone oil-filled (viscosity 1300 centistokes) eye can be estimated from the measured AL (MAL) obtained on A and/or B scan echography, by multiplying MAL by a conversion factor of 0.71. IOL power can then be calculated using current biometry formulae (SRK/T). This study aims to evaluate the conversion factor in clinical practice. METHODS: Eleven patients undergoing combined removal of silicone oil and phacoemulsification with IOL implant were studied. Patients were divided into two groups. In Group 1 (seven patients), the IOL was placed in the capsular bag and in Group 2 (four patients) the IOL was placed in the ciliary sulcus. Calculated AL (CAL) was obtained by multiplying the MAL of the silicone oil-filled eye (as measured on A or B scan ultrasonagraphy) by the conversion factor of 0.71. IOL power was then estimated using the CAL in the SRK/T formula. The spherical equivalent of the postoperative refractive error was compared to predicted refractive error. RESULTS: The mean difference in actual and predicted refractive error was 0.74 dioptres (D) (standard deviation 0.75 D) for Group 1 and 1.31 D (standard deviation 1.4 D) for Group 2. CONCLUSIONS: The conversion factor of 0.71 corrects for the apparent increase in AL induced by silicone oil of viscosity 1300 centistokes. This allows accurate prediction of the required IOL power in eyes undergoing combined cataract extraction, removal of silicone oil and lens implant. Sulcus placement of the IOL gives a less predictable result than placement in the capsular bag.

Biometry↗
PubMed1994

Genotypic evaluation of ocular pathologies in sickle cell diseases.

Sickle cell disease patients are known to manifest different types of ocular problems. These problems include proliferative and non-proliferative retinopathies, and refractive errors. The distribution of these pathologic and refractive problems among the sickle cell genotypes is analyzed according to the individual genotypes. Data collected from a total of 63 sickle cell disease patients who responded to the questionnaires shows that fifty-six percent (35) are males and forty-four percent (28) are females. The genotype distributions are: SS, 55% (34); SC, 33% (21); S-Thal, 11% (7); while 2% (1), is AS-genotype. Overall findings show that severe ophthalmic abnormalities were reported by approximately 90% of the respondents with sickle cell disease. The majority of sickle cell disease patients in this research show consistent susceptibility to both fungal and bacterial infections with varying degree of refractive errors. It is observed that refractive errors are prevalent in SC and S-Thal sickle cell genotypes, while the severity of anemia and painful crises are more prevalent in SS and S-Thal genotypes. Systemic ocular problems are also prevalent among the SC and S-Thal disease genotypes.

Adolescent↗
PubMed2000

The measurement of patient-reported outcomes of refractive surgery: the refractive status and vision profile.

PURPOSE: To develop a questionnaire, the Refractive Status and Vision Profile (RSVP), to assess health-related quality of life associated with refractive error and its correction. METHODS: The published literature on patient report of visual and overall function was reviewed, and the RSVP was self-administered by 550 participants with refractive error. Cross-sectional validation was performed using standard psychometric techniques. The responsiveness of the RSVP to surgical intervention was assessed prospectively in a subset of 176 patients. The principal outcomes measures were scores on the overall RSVP scale (S) and on 8 RSVP subscales (functioning, driving, concern, expectations, symptoms, glare, optical problems, problems with corrective lenses). RESULTS: The RSVP (S) and its subscales demonstrated very good internal consistency (Cronbach's alpha, 0.70-0.93). S and several subscale scores were independently associated with satisfaction with vision and were more correlated with satisfaction with vision than with either visual acuity or refractive error. Higher refractive error was associated with lower scores on S and on 5 subscales. In the prospective surgical cohort, 15% of patients had some worsening in their total RSVP score; however, substantial variation was seen in the individual subscales where worsening ranged from 7% (problems with corrective lenses) to 41% (driving). The effect size (measure of responsiveness) of the RSVP and most of its subscales was very high. Approximately 14% of patients had significant worsening in 3 or more subscales, and this outcome was found to be independently associated with being dissatisfied with vision following surgery (OR, 5.84; 95% CI, 1.88, 8.13). CONCLUSIONS: The RSVP has been validated as a questionnaire that measures patient-reported quality of life related to refractive error and its correction. It is responsive to surgical intervention and provides important information regarding patient outcomes not available from standard clinical measurements.

Adult↗
PubMed2005

Results of resident-performed laser in situ keratomileusis.

PURPOSE: To analyze the results of resident-performed laser in situ keratomileusis (LASIK). SETTING: Rush University Medical Center, Department of Ophthalmology, Chicago, Illinois, USA. METHODS: This retrospective study comprised 44 consecutive eyes of 22 patients who had LASIK performed from August 2000 through February 2002. Based on preoperative spherical equivalent, the eyes were divided into a low myopia group (A) (-1.0 to -6.0 diopter [D]) and a higher myopia group (B) (> -6.01 D). Preoperative and postoperative spherical equivalent (SE), best corrected visual acuity (BCVA), and uncorrected visual acuity (UCVA) were measured and analyzed within each group. Patients had at least 2 follow-up visits, with the second visit occurring between 1 and 9 months postoperatively. RESULTS: Preoperatively, the mean SE in Group A was -3.93 D +/- 1.53 (SD) and in Group B, -8.49 +/- 1.70 D. At the final visit, the SE in Group A decreased to -0.29 +/- 0.55 D and in Group B, -1.09 +/- 0.87 D. The UCVA in Group A at the final visit was 20/20 or better in 43% of eyes and 20/40 or better in 100% of eyes. In Group B, the UCVA was 20/20 or better in 31% of eyes and 20/40 or better in 75% of eyes. In all eyes, the BCVA improved by 1 line in 16% or remained the same in 84%. No eyes lost any lines of BCVA. The SE taken at the last visit was within +/-0.5 D in 69% of all eyes and within +/-1.0 D in 82% of all eyes. The incidence of patients needing retreatment in resident-performed LASIK surgery was 3 of 44 (6.8%). CONCLUSIONS: Laser in situ keratomileusis performed by residents is a safe and effective procedure for correction of refractive error. Postoperative UCVA, refractive error, retreatment rate, and loss of BCVA were consistent with published results from nonresident surgeons. These results also exceeded the U.S. Food and Drug Administration requirements for LASIK surgery.

Adult↗
PubMedDate not supplied

Alcon LADARWave customcornea retreatments.

PURPOSE: To present our experience performing wavefront-guided ablations for the treatment of residual refractive error following previous refractive surgery. METHODS: Four different cases are presented-1) primary wavefront-guided LASIK; 2) wavefront-guided lift-flap LASIK retreatment; 3) wavefront-guided photorefractive keratectomy (PRK) retreatment; and 4) wavefront-guided PRK over radial keratotomy retreatment. All procedures were performed with the Alcon CustomCornea laser platform. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), manifest refraction, and wavefront analysis (6.5-mm pupil) were performed preoperatively and 3 months after CustomCornea retreatment. The Alcon LADARWave device was used for wavefront measurements. RESULTS: Total lower order and higher order aberrations were decreased following wavefront-guided retreatment, resulting in improved quality of vision. The maximum target offset (+ 0.75 diopters) can be used to prevent an overcorrection of defocus (myopia) when treating a significant amount of spherical aberration. CONCLUSIONS: Wavefront-guided ablation was an effective treatment for residual lower and higher order aberrations following previous refractive surgery. Custom ablation treatment algorithms need to be developed specifically for retreatment procedures.

Adult↗