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PubMed1992

Radial keratotomy: eleven-year experiences.

During the period from 1980 to 1991, Radial Keratotomy (RK) had been done by the author under topical anesthesia in more than 10,000 cases, mostly on both eyes at the same time. Those patients had myopia with a preoperative refractive error between 1.5 and 20.0 diopters (D). The surgical technique consisted of 4, 8, 16 incisions using a diamond knife with micrometer and the diameter of the central clear zone was mostly 3.0 mm and determined by preoperative refractive error. Many different procedures were tried to improve the effect of RK, including redeepening intentional microperforations at 1.5 mm, 3 mm, 5 mm distance from the corneal center. But these procedures had no significant effect 6 months after the operation. Complications such as infection, glaucoma, cataract, etc. were almost none. Results of RK on long term follow up showed hyperoptic tendency, and the visual fluctuation were none or minimal.

Follow-Up Studies↗
PubMed2002

[Amblyopia in myopia in patients with strabismus and without strabismus].

PURPOSE: To determine factors, which have influence on presence of strabismus among myopic patients with amblyopia. MATERIAL AND METHODS: Material covers 21 myopic patients with amblyopia, aged 6-15. All children presented have a different amount of anisometropia, 12 of them had strabismus. Authors, compared the group of patients with amblyopia and strabismus (12) with the group of patients with pure anisometropic amblyopia (9), according to the following criteria: age of presentation, best corrected visual acuity, mean refraction error of amblyopic eye, mean amount of anisometropia, percentage of patients with central fixation and binocular vision. RESULTS: Patients with strabismus presented oneself earlier than patients without squint. Best corrected visual acuity was better in patients without strabismus. Refraction error in both groups has similar value. Amount of anisometropia was slightly smaller in the group with squint. Central fixation and binocular vision were better preserved among patients without strabismus. Authors didn't find the following correlations too: correlation between amount of anisometropia and amount of amblyopia in both groups, correlation between amount of anisometropia and the amount of the deviation of squinting eye, correlation between depth of amblyopia and the amount of deviation of the squinting eye. CONCLUSION: It seems, that primary factor leading to presence of strabismus among patients with anisometropic myopia, is motor dysfunction of extraocular muscles.

Adolescent↗
PubMed1999

Refractive changes among Norwegian university students--a three-year longitudinal study.

PURPOSE: The aim of this study was to investigate the changes in refractive error during a three-year period among university students exposed to high educational demands. METHODS: A three-year longitudinal cohort study was performed among 224 Norwegian engineering students (mean age 20.6 years, 117 females and 107 males) measuring their refraction at the beginning and the end of the period. The examinations included automated and clinical refraction in cycloplegia. A total of 192 students (100 females and 92 males) completed the study. RESULTS: In the student population under study the prevalence of myopia increased significantly from 48% to 65% (p<0.001, right eye) and the mean refractive error increased significantly from -0.64+/-2.18 D (n=224) to -1.21+/-2.30 D (n=192) (p<0.001, right eye) during the period. Of eyes emmetropic at the start of the study (n=49, right eye), 59% became myopic. Among the eyes initially myopic (n=92, right eye), 73% progressed further into myopia, with at least -0.37 D during the three-year period. Of eyes initially hyperopic (n=51, right eye), 8% became myopic, while 14% became emmetropic. CONCLUSIONS: A shift in refraction towards myopia is frequent among university students during their study period.

Adult↗
PubMed1998

[Cataract surgery in nanophthalmic eyes with an axial length of less than 20.5 mm].

BACKGROUND: Aim of this study was to analyze the results of cataract surgery in nanophthalmic eyes with axial length of less than 20.5 mm. PATIENTS AND METHODS: From 1991 to 1996 extracapsular cataract extraction with posterior chamber lens implantation was performed in 20 eyes of 19 patients (mean age 70.2 +/- 12.7 years, 4 male, 16 female) with axial length of less than 20.5 mm. Mean preoperative visual acuity was 0.16 +/- 0.15, refractive error +5.1 +/- 3.8 dpt and intraocular pressure 18.7 +/- 10.3 mm Hg. The mean follow-up was 24.4 months. Patient data were collected prospectively with standardized "Erlanger Augenblätter" and the computer-aided automatized operation record system "OPERA". These data together with the biometrical data were analized in a retrolective manner. RESULTS: Preoperatively 6 of 20 eyes had angle closure situation, 7 of 20 eyes had undergone intraocular surgery previously (5 x iridotomy, 1 x surgical iridectomy, 1 x filtration procedure). Pseudoexfoliation syndrome was present in 3 eyes. The posterior chamber lens (mean refractive power 31.7 +/- 3.0 dpt, optic diameter 6.5 and 7.0 mm) was positioned 18 x intracapsular, 2 x into the sulcus and 1 x by scleral fixation due to capsular rupture without vitreous loss. In 16 of 20 eyes iris surgery was performed additionally, in one eye an anterior sclerotomy was necessary. Intraoperatively "vis a tergo" occurred in 10 eyes and anterior chamber hemorrhage in one eye. Visual acuity improved in 16 of 20 eyes. The mean visual acuity was 0.3 +/- 0.2. At the end of follow-up 13 eyes had an improvement of visual acuity. Mean intraocular pressure was 16.5 +/- 3.3 mm Hg, refractive error was +0.47 +/- 2.9 dpt and differed by -0.49 +/- 1.8 dpt from the preoperatively calculated refraction. Postoperatively angle closure glaucoma developed in one eye, a ciliopseudophakic angle closure glaucoma and recurrent iris bombata in one eye. Reoperations included cyclokryokoagulation in two eyes, pars plana vitrectomy in one eye and repeated Nd-YAG iridotomies in one eye. CONCLUSION: Regarding the special anatomic situation, the surgical procedure has to be planned individually, including the determination of sclera thickness, corneal diameter and lens volume/eye volume ratio.

Aged↗
PubMed1986

Long-term follow-up of refractive and keratometric results of pediatric epikeratophakia.

To examine the long-term stability of epikeratophakia and its effect on the development of young eyes, the change in corneal curvature and refractive error over time were reviewed in pediatric patients who underwent epikeratophakia for optical correction of aphakia. Over an average follow-up time of 28.0 months, corneal curvature flattened by 1.15 diopters, or 0.53 D/yr. The average change in refractive error was -2.81 D over 23.6 months, or 1.49 D/yr. Patients younger than 1 year of age at surgery became significantly more myopic over the period of follow-up (4.75 D) than patients older than 1 year of age at surgery (2.24 D). These changes are consistent with the corneal flattening and increase in axial length expected from normal growth. Aphakic infants corrected to emmetropia with epikeratophakia will likely require correction of myopia in later childhood.

Aphakia, Postcataract↗
PubMed1982

Strabismus and amblyopia associated with regressed retinopathy of prematurity.

A series of 38 patients with regressed retinopathy of prematurity were compared with control groups of babies having similar gestational age who did not have retinopathy of prematurity, and to a control group of full-term babies. A substantially higher incidence of strabismus, amblyopia, and high refractive errors was found in the group with retinopathy of prematurity as compared with both other groups. In general, these patients had a successful response to standard amblyopia and strabismus management. No substantial difference was found between the refractive errors of the babies in the premature control group and the term control group.

Amblyopia↗
PubMed2006

Visual experience and patient satisfaction with wavefront-guided laser in situ keratomileusis.

PURPOSE: To determine the correlation between patient perception and clinical measurements after wavefront-guided laser in situ keratomileusis (LASIK). SETTING: Multicenter clinical trial. METHODS: In this retrospective analysis of clinical study results in 274 eyes, wavefront-guided LASIK procedures were performed in 274 myopic-astigmatic eyes at 6 sites. Comprehensive evaluations of vision and ocular health were conducted preoperatively and for 6 months postoperatively. Visual acuity and contrast sensitivity were measured, and questionnaires were administered. Questionnaire responses were compared with clinical measurements. RESULTS: The overall distribution shifted toward "more satisfied." The "very satisfied" population increased by as much as 70% in all areas. There was no significant change in frequency of visual symptoms. Patients were more expressive about visual decline than visual improvement. Perception of changes in vision appeared to be related to mesopic contrast sensitivity and mesopic contrast sensitivity under glare. Mesopic pupil diameter was not a major predictor of patient satisfaction. Contact lens wearers were more satisfied with postoperative vision than were spectacle wearers. Men were more likely to report visual symptoms and to complain about night vision, although their changes were the same as those of the women. Residual refractive error was a major predictor for most questionnaire items. CONCLUSION: Most patients were as satisfied or more satisfied with their postoperative uncorrected visual acuity than with their preoperative best corrected visual acuity. By continuing to minimize postoperative refractive error through the use of nomograms and improved technology, visual complaints such as night glare and halo could be diminished or even eliminated. The study shows that subjective experience affected satisfaction with results. Some dissatisfaction might be mitigated by being sure patients are educated and have realistic expectations before surgery.

Adult↗
PubMedDate not supplied

Is there a hyperopic shift in myopic eyes during the presbyopic years?

BACKGROUND: Studies of age-related changes in myopia during the presbyopic years have produced contradictory results. Some studies have shown that myopic eyes undergo a hyperopic shift after the age of 40 or 45 years, whereas others have provided evidence for a myopic shift. In this paper, we report the results of both a cross-sectional study and a retrospective longitudinal study of age-related changes in refraction during the presbyopic years. METHODS: In the cross-sectional study, refractive error data were tabulated for the right eyes of 559 patients over the age of 45 years, who had been examined during a 17-month period in an established optometric practice. In the longitudinal study, we tabulated refractive error data on 100 myopes, 100 hyperopes and 100 emmetropes, who had been examined for periods varying from 10 to 26 years after age 40, all of whom had 6/6 visual acuity at all examinations. RESULTS: In the cross-sectional study, the prevalence of myopia during the later presbyopic years was found to be greater when eyes with all visual acuities were included than when only eyes with acuity of 6/6 or better were considered. In the longitudinal study, it was found that almost all hyperopic and emmetropic eyes showed an age-related hyperopic shift; but only a small proportion of myopic eyes shifted toward hyperopia, with others remaining relatively stable and still others increasing in myopia. DISCUSSION AND CONCLUSIONS: We suggest that when healthy myopic, hyperopic, or emmetropic eyes shift in the hyperopic direction, it is because of an age-related decrease in the gradient index of the lens; but when healthy myopic eyes shift in the myopic direction, it is because of axial elongation that more than compensates for the decrease in the gradient index of the lens. Another possible cause of a myopic shift, even for eyes having 6/6 visual acuity, is the presence of early, sub-clinical nuclear sclerosis.

Journal Article↗
PubMedDate not supplied

Laser in situ keratomileusis improves visual acuity in some adult eyes with amblyopia.

PURPOSE: To report the results of laser in situ keratomileusis (LASIK) in a series of adult patients with amblyopia. METHODS: A retrospective noncomparative review was performed on patients with amblyopia who underwent LASIK for correction of ametropia, using the Summit Krumeich Barraquer microkeratome and the Nidek EC-5000 excimer laser. Data were collected on uncorrected visual acuity, best spectacle-corrected visual acuity, manifest refraction, anterior segment evaluation, intraocular pressure, corneal topography, and dilated fundus examination (preoperative and postoperatively on day 1, months 2 and 6). RESULTS: Eight eyes of seven patients were included, with a mean patient age of 30 +/- 10 years (range 21 to 49 yr). Mean preoperative spherical equivalent refraction was -4.70 D (range -12.62 to +4.71 D) and the best spectacle-corrected visual acuity varied from 20/32 to 20/80. At 2 months after LASIK, mean spherical equivalent refraction was -0.37 +/- 0.60 D (range -1.37 to + 0.60 D), uncorrected visual acuity ranged between 20/20 to 20/30, and a mean gain of 3 Snellen lines (range 2 to 4 lines) was observed. All patients reported significant subjective improvement in their perception of vision. The visual acuity and subjective improvement were maintained throughout 6 months postoperatively. CONCLUSIONS: LASIK with the Nidek EC-5000 laser for correction of ametropia in adult amblyopic eyes provided encouraging results for visual acuity improvement beyond correction of the refractive error.

Adult↗
PubMed1997

Excimer laser correction of astigmatism using erodible masks.

PURPOSE: The latest development in the erodible mask technology is an excimer laser containing the mask in the laser optical pathway. This paper reports the results of the first human series of consecutive treatments performed for the correction of compound myopic astigmatism. METHODS: We have treated 83 eyes. Spherical equivalent attempted correction ranged between -1.75 and -11.75 D (mean -7.07 +/- 2.45 D), astigmatic attempted correction ranged between -1.00 and -5.00 D (mean -2.42 +/- 1.02 D). The sphere correction was made by diaphragm using a multi-zone software with three ablation zones: 100% of the total attempted correction for the central 5.0 mm zone, 70% for the second 6.0 mm zone, 30% for the outer 6.5 mm zone. Cylinder correction was made sequentially after myopic correction using the appropriate mask. RESULTS: One month after treatment, mean refractive error was +1.07 +/- 1.24 D (range +4.50/-1.75 D) for spherical equivalent, and -0.49 +/- 0.57 D (range +0.75/-2.00 D) for astigmatism. Forty-eight eyes (57.8%) had uncorrected visual acuity of 20/40 or better. At six months, mean refractive error was +0.42 +/- 0.97 D (range +3.75/-1.00 D) for spherical equivalent, and -0.44 +/- 0.51 D (range +0.25/-3.00 D) for astigmatism. Vector analysis showed that 57 eyes (68.7%) had 5 or less degrees rotation. Seventy-two (86.7%) and 54 eyes (65.1%) had uncorrected visual acuity equal or better than 20.40 and 20/25 respectively. One eye (1.2%) showed a best corrected visual acuity loss of more than one line, but 8 eyes (9.6%) had a gain of more than one line. One-year results on a smaller series (33 eyes) overlap the six-month results. CONCLUSIONS: The mask in-the-rail excimer laser delivery system appears to be effective and predictable in the correction of compound myopic astigmatism. We observed no significant regression of the astigmatic correction over time. Longer follow-up on larger series is necessary to draw final conclusions.

Adolescent↗
PubMedDate not supplied

Compound myopic astigmatism correction using a mask in-the-rail excimer laser delivery system. Preliminary results.

PURPOSE: The latest development in the erodible mask technology is an excimer laser containing the mask in the laser optical pathway. This paper reports the results of the first human series of consecutive treatments performed for the correction of compound myopic astigmatism. METHODS: We have treated 83 eyes. Spherical equivalent attempted correction ranged between -1.75 and -11.75 D (mean -7.07+/- 2.45 D), astigmatic attempted correction ranged between -1.00 and -5.00 D (mean -2.42+/- 1.02 D). The sphere correction was made by diaphragm using a multi-zone software with three ablation zones: 100% of the total attempted correction for the central 5.0 mm zone, 70% for the second 6.0 mm zone, 30% for the outer 6.5 mm zone. Cylinder correction was made sequentially after myopic correction using the appropriate mask. RESULTS: One month after treatment, mean refractive error was + 1.07 +/- 1.24 D (range + 4.50/-1.75 D) for spherical equivalent, and -0.49 +/- 0.57 D (range + 0.75/-2.00 D) for astigmatism. Forty-eight eyes (57.8%) had uncorrected visual acuity of 20/40 or better. At six months, mean refractive error was +0.42 +/- 0.97 D (range + 3.75/-1.00 D) for spherical equivalent, and -0.44 +/- 0.51 D (range +0.25/-3.00 D) for astigmatism. Vector analysis showed that 57 eyes (68.7%) had 5 or less degrees rotation. Seventy-two (86.7%) and 54 eyes (65.1%) had uncorrected visual acuity equal or better than 20/40 and 20/25 respectively. One eye (1.2%) showed a best corrected visual acuity loss of more than one line, but 8 eyes (9.6%) had a gain of more than one line. One-year results on a smaller series (33 eyes) overlap with the six-month results. CONCLUSIONS: The mask in-the-rail excimer laser delivery system appears to be effective and predictable in the correction of compound myopic astigmatism. We observed no significant regression of the astigmatic correction over time. Longer follow-up on larger series is necessary to draw final conclusions.

Adolescent↗
PubMed2001

Manifest refraction versus autorefraction for patients with subfoveal choroidal neovascularization.

PURPOSE: To compare the results from manifest refraction using trial lenses and a standard visual acuity protocol to results from autorefraction for obtaining refractive error and best corrected visual acuity in patients enrolled in a randomized clinical trial. METHODS: During a 4-month period, 29 patients with subfoveal choroidal neovascularization (CNV), who were enrolled in the Submacular Surgery Trials (SSTs) Pilot Study at the Wilmer Ophthalmological Institute, gave verbal consent to participate in this study. Best corrected visual acuity was obtained using Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity charts and standardized room lighting after performance of manifest refraction, according to the SST protocol, and autorefraction. Refractive error (spherical equivalent) and visual acuity scores were obtained in both eyes of all patients. RESULTS: On average, manifest refraction gave a spherical equivalent that was 1.04 D more plus than autorefraction (95% limits of agreement = 0.74, 1.34). On average, the visual acuity score was 1.5 letters better after manifest refraction than after autorefraction (95% limits of agreement = 0, 3.0). The comparison of the two methods of refraction was subdivided according to visual acuity level and eye disease (age-related macular degeneration or ocular histoplasmosis syndrome). CONCLUSIONS: Despite large differences in spherical equivalent between manifest refraction and autorefraction, the visual acuity scores were close (mean difference, 1.5 letters). Other studies comparing subjective refraction and autorefraction have shown similar results. Autorefraction in patients with subfoveal CNV may be a satisfactory alternative to manifest refraction in clinical trials and field studies in which best corrected visual acuity is of interest.

Adult↗
PubMed1999

Progression of myopia in Hong Kong Chinese schoolchildren is slowed by wearing progressive lenses.

PURPOSE: In Chinese societies, primary and secondary schoolchildren perform large amounts of reading and homework and thus spend long periods performing near work during their growth years. Progressive lenses, which can permit a focused retinal image at distance, intermediate, and near, without accommodation, may slow the development of myopia. This paper reports results of a 2-year longitudinal study to examine the effects of progressive lenses on myopia progression in myopic Chinese children; these children were aged between 9 and 12 years at the beginning of the study. METHODS: Prestudy vision screening tests and five examinations, which included noncycloplegic refraction, were conducted at half-yearly intervals. Of those who completed the study, 32 children wore single vision (SV) lenses (the SV group) and 36 wore progressive lenses; of the latter, 22 wore a +1.50 D addition (the P1 group) and 14 wore a +2.00 D addition (the P2 group). Refractive error, corneal curvature, axial length, vitreous depth, and intraocular pressure were measured at every examination. Height was measured as an index of general growth. RESULTS: Progressive lenses significantly retarded the progression of the myopia in these children. Initially, the mean refractive error of the SV group was -3.67 D, of the P1 group was -3.73 D, and of the P2 group was -3.67 D. The mean myopic progressions over the 2 years of the study were -1.23, -0.76, and -0.66 D for the SV, P1, and P2 groups, respectively. CONCLUSION: Progressive lenses reduce the progression of myopia. It may be that the interaction of the progressive lenses with the accommodation system is the cause of this reduction in myopia progression because the +2.00 D addition appeared more effective than the +1.50 D addition in slowing the progression.

Child↗
PubMed2003

AC/A ratios in myopic and emmetropic Hong Kong children and the effect of timolol.

PURPOSE: Caucasian children with myopia have elevated response accommodative vergence to accommodation (AC/A) ratios. The purpose of this study was twofold: to determine if response AC/A ratios vary with refractive error and with myopic progression rate in Hong Kong Chinese children, and to determine the effect of beta-adrenergic antagonism with topical timolol application on AC/A ratios. METHODS: Thirty children aged eight to 12 years participated in the study. All refractive errors were corrected with spectacle lenses. Accommodative responses were measured using a Shin-Nippon autorefractor and concurrent changes in vergence were assessed using a vertical prism and a Howell-Dwyer card at three metres and 0.33 metre. Accommodative demand was altered using plus or minus two dioptre lenses and lens- and distance-induced response AC/A ratios were calculated. Measurements were repeated 30 minutes after the instillation of topical timolol maleate (0.5 per cent). RESULTS: AC/A ratios appeared higher in progressing myopic children but the difference was not statistically significant. Timolol application reduced accommodative convergence (AC) in the stable myopes (reduction = -3 +/- 1.14 prism dioptres) but not in the emmetropes (0.69 +/- 0.96 prism dioptres) or progressing myopes (0.16 +/- 0.43 prism dioptres) and this difference between refractive groups was statistically significant (F(2, 27) = 3.766; P = 0.036). However, timolol did not produce a significant change in the accommodative response to positive or negative lenses or response AC/A ratios. CONCLUSIONS: We did not find that AC/A ratios in myopic Chinese children were elevated and therefore, it is unlikely that elevated AC/A ratios are responsible for the high levels of myopia that occur in Hong Kong. The finding that timolol reduced AC in the stable myopes suggests that the autonomic control of accommodative convergence in these children may be different from that in emmetropic children and those with progressing myopia.

Accommodation, Ocular↗
PubMed1987

Intraocular lens style and refraction in eyes treated with silicone oil.

The comparatively high refractive index of silicone oil significantly alters the refractive power of the human eye when it is placed into the vitreous cavity during retinal reattachment surgery. If cataract extraction and intraocular lens (IOL) implantation are subsequently performed, significant refractive errors result with most IOL styles if standard formulas are used to determine lens power. Thick-lens optical analysis of four IOL styles showed that the meniscus style yields the smallest difference between predicted (Binkhorst, Sanders-Retzlaff-Kraff formulas) and actual postoperative refraction. This IOL style also minimizes the change in refractive error that accompanies subsequent alterations in the contents of the vitreous cavity, including removal of silicone oil and replacement with balanced salt solution.

Eye↗
PubMed1989

Visual, refractive, and keratometric results of epikeratophakia in children. A two-year follow-up.

Fifty-two patients under the age of 16 years (68 eyes) received epikeratophakia grafts for the correction of aphakia. In 27 eyes, epikeratophakia was a primary procedure combined with lensectomy. Fifteen children underwent bilateral surgery. Overall, the success rate was 91%, and with repeated surgery it was 94%. The average change in refractive error was 15.9 diopters (D) and the average spectacle overcorrection was +0.3 D. Sixty-one percent (35/57) of the eyes were within 1 D of emmetropia and 97% (55/57) were within 3 D of emmetropia. Overall, the refraction was stable in the follow-up between six months and 1 1/2 years following surgery. However, a myopic shift of 2.0 D occurred between six months and 1 1/2 years in very young children following refractive surgery. The corneal curvature was measured only in older children and showed an average increase of 10.7 D. Visual acuity results in verbal patients were comparable to those in patients with contact lenses. The majority of smaller children demonstrated improvement in visual acuity with a combination of epikeratophakia and amblyopia therapy.

Adolescent↗
PubMed1997

[Computerized video-keratoscopic analysis and cataract surgery by phacoemulsification. Predictive calculation of the power of the intraocular implant].

PURPOSE: The authors present the results of a prospective study of 125 consecutive cases of phacoemulsification, performed by a single surgeon, to assess the benefit of computerised videokeratoscopy for the improvement of the predictive calculation of the power of intraocular lenses (IOL). METHODS: Preoperative keratometry was determined by means of 3 concurrent techniques, including automated kerato-refractometry (AKR 2000, Nidek) and videokeratoscopy by TMS-1 (Tomey) and CAS-1 (EyeSys). The results of the IOL calculation by these 3 methods was compared postoperatively to the power of the actual IOL yielding emmetropia as calculated by the optical method based on the postop, refraction at the various time-points. RESULTS: Simulated values obtained with videokeratoscopy significantly reduced the refractive error at 1 postop, week (p = 0.001), one month (p = 0.002) and 3 months (p = 0.002) for the CAS1 and at 3 months (p = 0.002) for the TMS1, as compared to values obtained with conventional automated keratometry. The refractive error was significantly reduced with the CAS1 at one month (p = 0.001) and 3 months (p = 0.019) as compared to TMS1. CONCLUSION: The determination of the anterior curvature of the entrance pupil by videokeratoscopy significantly improves the predictive calculation of the IOL power.

Aged↗
PubMed2006

Comparison of single-segment and double-segment Intacs for keratoconus and post-LASIK ectasia.

PURPOSE: To evaluate the efficacy of single-segment Intacs and compare with double-segment Intacs in subjects with post-LASIK ectasia and keratoconus. DESIGN: Retrospective comparative analysis. METHODS: setting: Boxer Wachler Vision Institute, Beverly Hills, California, USA. study population: Thirty-seven eyes of 28 patients with keratoconus and post-LASIK ectasia classified into two groups: single-segment group (17 eyes, 11 patients) and double-segment group (20 eyes, 17 patients). Both groups were matched for age, visual acuity (uncorrected, UCVA; best spectacle-corrected, BSCVA), refractive error (sphere, cylinder, spherical equivalent), and keratometry (K) value (flat, steep, average) by t test for equality of means. intervention: Single- or double-segment Intacs procedure with axis of incision for insertion in the steep axis of manifest refraction. main outcome measure: Improvement of acuity, refractive error, K values, and inferior-superior (I-S) ratio. RESULTS: There was more improvement in UCVA in the single-segment group (nine lines) than the double-segment group (2.5 lines), P < .01; in BSCVA in the single-segment group (2.5 lines) than the double-segment group (<1 line), P < .01; in steep K values in the single-segment group (2.76 diopters +/- 2.68) than the double-segment group (0.93 diopters +/- 2.01), P = .02; and in I-S ratio in the single-segment group (9.51 +/- 7.49) than the double-segment group (4.22 +/- 4.82), P = .01; and greater cylinder decrease after Holladay vector analysis in the single-segment group (5.69 diopters +/- 3.10) than the double-segment group (1.58 diopters +/- 3.09), P < .01. CONCLUSIONS: Single-segment Intacs improved both UCVA and BSCVA by differential flattening of inferior meridian and steepening of superior meridian as reflected by change in I-S ratio.

Adult↗