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Refractive and keratometric results after the triple procedure: experience with early and late suture removal.

OBJECTIVE: The objective of this study was to determine the outcome of early and late suture removal after the triple procedure (i.e., penetrating keratoplasty, cataract extraction, lens implant). DESIGN AND PARTICIPANTS: The refractive and keratometric results of 106 eyes undergoing the triple procedure were reviewed. The target postoperative refractive error was -1 diopter (D). RESULTS: Average length of follow-up was 40.3 months. Twenty eyes had sutures removed early (<18 months after surgery), 39 had sutures removed late (> or = 18 months after surgery), and 47 had sutures still intact at last follow-up. A best spectacle-corrected visual acuity of 20/40 or better was achieved in 90% of eyes with sutures removed early, 82.1% with sutures removed late, and 70.2% with sutures in place. For all eyes, the mean spherical equivalent at last follow-up was -2.50 D, with 75% of eyes falling between -4 and +2 D. The mean final refractive error was -3.40 +/- 3.53 D for eyes with sutures removed early and -1.79 +/- 3.99 D for eyes with sutures removed late. Eyes with sutures remaining had a mean final refractive error of -0.33 +/- 2.25 D. There was an overall decrease in refractive and keratometric astigmatism after both early and late suture removal with no significant difference between groups. However, there was a wide range of change with some eyes experiencing a decrease and others an increase in astigmatism. Mean postoperative K readings increased significantly for both groups after suture removal (final mean K, 47.00 D) but remained stable for eyes with sutures in. CONCLUSION: The authors data suggest that the final refractive error and net change in refractive and keratometric astigmatism after the triple procedure are not dependent on the timing of suture removal.

Aged↗

Active emmetropization--evidence for its existence and ramifications for clinical practice.

There is increasing evidence from animal studies in support of the concept of an active emmetropization mechanism which has potentially important clinical ramifications for the management of refractive errors. Recent research into refractive development and emmetropization is reviewed, with emphasis given to work involving the chick, tree shrew and monkey, which represent the three most widely used animal models in this field. The findings of this research are reviewed in a clinical context. Compensatory eye growth responses to focusing errors imposed by lenses represent the most compelling evidence for active emmetropization. These observations are complemented by other evidence showing recovery from induced refractive errors such as form-deprivation myopia. Of the animals listed above, chicks show the most impressive emmetropization, being able to compensate fully (using choroidal and scleral mechanisms) to lens powers ranging from +15 D to -10 D. The range of lens powers eliciting appropriate compensatory responses is narrower in the tree shrew and monkey, and the response patterns generally are also more complex to interpret. These data relate to young animals and together indicate refractive plasticity during development. Extrapolation of these findings to humans predicts that natural emmetropization will be inhibited in neonates by early intervention with prescription lenses, and that refractive correction of myopia will lead to accelerated progression. This convincing evidence for active emmetropization warrants due consideration in developing clinical management strategies for refractive errors.

Animals↗

An assessment of consecutively presenting orthokeratology patients in a Hong Kong based private practice.

PURPOSE: The aim of this study was to collect objective, subjective and demographic data on consecutively presenting orthokeratology (ortho-k) patients who attended for routine follow-up examination in a Hong Kong based private practice in May 2001. METHOD: Sixty-nine patients who returned to the surveyed practice for follow-up visits during the study period (May 2001) were interviewed and relevant data extracted from their files. Data collected included identification and estimation of the extent of complications encountered by ortho-k patients and their satisfaction with the treatment. RESULTS: Among the 61 patients who had been wearing ortho-k lenses for at least one month, 50 patients were younger than 16 years old. Twelve children (24 per cent) had been reluctant to wear ortho-k lenses before undergoing the treatment but, after commencement of lens wear, only one child was not very willing to wear the ortho-k lenses. The mean pre-ortho-k spherical refractive error of these patients was -3.93 +/- 2.30 D (OS only). Of the 59 patients who wore ortho-k lenses for at least one month and who were on night therapy, 10 patients had to wear spectacles or contact lenses in the daytime due to significant residual myopia. There was no statistically significant correlation between post-ortho-k unaided visual acuity and pre-ortho-k refractive error (spherical, cylindrical or the equivalent sphere) in the 49 patients who did not need to wear any vision correction in the daytime. Of the 61 patients, four reported eye inflammation/infection during the treatment. All recovered their ocular health without any effect on their vision or corneal health. The incidence of corneal staining that required lens wear to be stopped appeared to increase with the duration of ortho-k lens treatment. The incidence of staining was not related to refractive error, unaided visual acuity or the age of the subjects. The most common problem reported by the patients was lens binding and there were also reports of increased redness, itching, light sensitivity and secretion of mucus in the morning after opening their eyes. More than 50 per cent of the patients experienced some distance vision blur, which was worse towards the end of the day. For most patients, these problems occurred only occasionally. Higher pre-ortho-k spherical refractive error was related to poor near and distance vision and worse distance vision towards the end of the day. CONCLUSION: The majority of the patients interviewed were children who reported being 'happy with the results of the treatment'. Night wear is the main wearing modality and in view of the increased risk of complications in overnight wear and the fact that a large number of the patients are children, the need for strict compliance with the practitioner's instructions for lens use and care cannot be overemphasised. With careful monitoring and good compliance, complications with overnight ortho-k wear can be minimised. In view of the high incidence of lens binding, it is essential that patients and parents of young patients know the correct method to free a bound lens.

Adolescent↗

High prevalence of myopia in Japanese patients with multiple evanescent white dot syndrome.

PURPOSE: To compare the incidence of refractive errors in Japanese patients with multiple evanescent white dot syndrome (MEWDS) with that in age- and sex-matched controls. METHODS: Fifty Japanese patients with MEWDS (11 males and 39 females; ages, 15-58; mean 29.9 years) were studied retrospectively. The refractive errors (spherical equivalent) in the patients were compared with those of 150 age- and sex-matched controls. RESULTS: The mean refractive error in the patient group was -5.30 +/- 4.58 diopters (D) which was significantly greater than that in the controls (-2.57 +/- 2.94 D, P = 0.0005). Twenty-two (44.0%) of the 50 MEWDS patients had refractive errors >-6.00 D; whereas 14 (9.3%) of 150 normal subjects had this degree of myopia. This difference was statistically significant ( P < 0.005). CONCLUSION: Japanese patients with MEWDS tend to be highly myopic.

Adolescent↗

Retinal stretching limits peripheral visual acuity in myopia.

Axial elongation of the myopic eye has the potential to stretch the retina, thereby reducing the sampling density of retinal neurons. Resolution acuity in the peripheral field of normal eyes is known to be sampling-limited, which suggests that retinal stretching in the myopic eye should have a direct effect on resolution acuity everywhere in the visual field except perhaps the fovea, which is usually optically limited. We tested this prediction that neural sampling density is reduced in myopic eyes by measuring resolution acuity for sinusoidal gratings in the fovea plus five peripheral locations in 60 myopic subjects exhibiting a wide range of refractive errors. Control experiments using a detection paradigm to provoke spatial aliasing verified that peripheral resolution was sampling limited. Retinal spatial frequencies of the grating stimulus were computed assuming Knapps' Law of visual optics, which ensures that retinal image size (in mm) is independent of refractive error when axial myopia is corrected by a spectacle lens located in the anterior focal plane of the eye. Results obtained at every retinal locus showed that resolution acuity declined linearly with magnitude of refractive error. Regression of the population data indicated that approximately 15 D of refractive error doubles the spacing between retinal neurons, thereby halving peripheral resolution acuity relative to the emmetropic eye. Several subjects also demonstrated sampling-limited performance in the fovea, which indicated that optical filtering by the eye's optical system failed to protect the fovea from aliasing artifacts of neural undersampling in these eyes. We conclude that stretching of the retina is a primary cause of reduced spatial resolution of the peripheral field, and occasionally of the fovea, in myopic eyes. Stretching appears to be locally uniform over the central +/-15 degrees of visual field but is globally non-uniform since the foveal region appears to stretch more than the globe itself.

Adult↗

[Correction of the astigmatism with the Artisan phakic toric lens].

The implantation of the intraocular anterior chamber phakic toric lens (PTIOL) Artisan, a product of the Ophtec company, is one of the most up-to-date methods of the correction of higher degree of myopic as well as hyperopic astigmatism. The authors refer about the results of PTIOL Artisan implantation in 6 patients (10 eyes). The major indication was the hyperopic astigmatism--in 5 patients (8 eyes); in one patient the indication was myopic astigmatism. In the followed up group of patients, there is the preponderance of men (5), and one woman only. The patients were divided into two subgroups: one with myopic astigmatism (1 patient, 2 eyes) and other with hyperopic astigmatism (5 patients, 8 eyes). The average age of the whole group at the time of the surgery was 27.7 +/- 2.8 years (range 23-38 years) and the average follow up period was 13.0 +/- 6.9 months (range 6-22 months). In the group the patients with follow up period shorter than 6 months were not included. The average preoperative spherical refractive error was +4.8 +/- 2.25 dioptres (D) and the average astigmatic error was -5.15 +/- 2.82 cylinders (Dcyl). In one case of myopia, the preoperative refractive error in both eyes was -7.0 D and -3.5 Dcyl. The target refraction was emetropia +/- 1.0 D. The authors evaluate the final uncorrected and best-corrected visual acuity (UCVA, BCVA), final postoperative refractive error, presence of intra- as well as postoperative complications, and changes of endothelial cells' density over time. The average final postoperative error in patients with hyperopic astigmatism was +0.72 +/- 0.93 D and -1.08 +/- 0.60 Dcyl. In the only patient with myopic astigmatism the final postoperative error of both eyes was +0.5 D and -0.5 Dcyl. The advantage of the PTIOL implantation is fast visual recovery, potential reversibility of the procedure, maintaining of the accommodation, and stability of the postoperative refraction.

Adult↗

Burden of moderate visual impairment in an urban population in southern India.

OBJECTIVE: To assess the prevalence and causes of moderate visual impairment in an urban population in southern India. DESIGN: Population-based, cross-sectional study. PARTICIPANTS: A total of 2522 (85.4% of the eligible) persons of all ages, including 1399 persons 30 years of age or older, from 24 clusters representative of the population of Hyderabad city. TESTING: The eligible subjects underwent a detailed ocular evaluation, including logarithm of the minimum angle of resolution (logMAR) visual acuity, refraction, slit-lamp biomicroscopy, applanation tonometry, gonioscopy, cataract grading, and stereoscopic dilated fundus evaluation. Automated threshold visual fields and slit-lamp and fundus photography were done when indicated by standardized criteria. MAIN OUTCOME MEASURE: Moderate visual impairment was defined as presenting distance visual acuity less than 20/40 to 20/200 or visual field loss by predefined standardized conservative criteria in the better eye. RESULTS: In addition to the 1% prevalence of blindness in this sample reported earlier, moderate visual impairment was present in 303 subjects, an age-gender-adjusted prevalence of 7.2% (95% confidence interval [CI], 4.5%-9.9%; design effect, 2.7). The major cause of moderate visual impairment was refractive error (59.4%, 95% CI, 52.3%-66.5%) followed by cataract (25.3%, 95% CI, 19%-31.6%). Multivariate analysis showed that the prevalence of moderate visual impairment was significantly higher in those 40 years of age or older (odds ratio, 10.9; 95% CI, 8-15) and females (odds ratio, 1.89; 95% CI, 1.41-2.53) and lower in those belonging to the highest socioeconomic status (odds ratio, 0.27; 95% CI, 0.14-0.51). However, because of the pyramidal age distribution of the population, 38.1% of the total moderate visual impairment was present in those younger than 40 years of age. The proportion of moderate visual impairment caused by refractive error was higher in the younger than in the older age groups (P < 0.0001). CONCLUSIONS: Projecting the results to the 26.5% urban population of India, there would be 18.4 million (95% CI, 11.5-25.2 million) persons with moderate visual impairment in urban India alone. Refractive error was the major cause of moderate visual impairment in the population studied. The absolute proportion of moderate visual impairment in those younger than 40 years of age was considerable. The eyecare policy of India, apart from dealing with blindness, should address the issue of the relatively easily treatable uncorrected refractive error as the cause of moderate visual impairment in an estimated 10.9 million persons in urban India.

Adolescent↗

Assessment of objective and subjective eccentric refraction.

PURPOSE: When performing perimetry, refracting subjects with central visual field loss, and in emmetropization studies, it is important to accurately measure peripheral refractive errors. Traditional methods for foveal refraction often give uncertain results in eccentric angles as a result of the large aberrations and the reduced retinal function. The aim of this study is therefore to compare and evaluate four methods for eccentric refraction. METHODS: Four eccentric methods were tested on 50 healthy subjects: one novel subjective procedure, optimizing the detection contrast sensitivity with different trial lenses, and three objective ones: photorefraction with a PowerRefractor, wavefront measurements with a Hartmann-Shack sensor, and retinoscopy. The peripheral refractive error in the horizontal nasal visual field of the right eye was measured in 20 degrees and 30 degrees. RESULTS: In general, the eccentric refraction methods compared reasonably well. However, the following differences were noted. Retinoscopy showed a significant difference from the other methods in the axis of astigmatism. In 30 degree eccentric angle, it was not possible to measure 15 of the subjects with the PowerRefractor and the instrument also tended to underestimate high myopia (<-6 D). The Hartmann-Shack sensor showed a myopic shift of approximately 0.5 D in both eccentricities. The subjective method had a relatively larger spread. CONCLUSIONS: This study indicates that it is possible to assess the eccentric refraction with all methods. However, the Hartmann-Shack technique was found to be the most useful method. The agreement between the objective methods and the subjective eccentric refraction shows that detection contrast sensitivity in the periphery is affected by relatively small amounts of defocus.

Adult↗

Effects of short-term VDT usage on visual functions.

An on-site comparative study was carried out on the effects of video display terminal (VDT) and non-VDT work on visual functions in two working populations in the same office environment. Both continuous VDT usage in a training situation over a few days and intermittent VDT usage in a normal working situation were assessed and particular attention paid to their effects on the refractive error of different refractive groups and for different age populations. Other visual functions measured were visual acuity (VA), accommodation, and convergence. Results show that VDT work does not have a significantly greater effect on visual function than non-VDT work.

Accommodation, Ocular↗

Recent advances in measurement of monochromatic aberrations of human eyes.

The field of aberrations of the human eye is moving rapidly, being driven by the desire to monitor and optimise vision following refractive surgery. It is important for ophthalmologists and optometrists to have an understanding of the magnitude of various aberrations and how these are likely to be affected by refractive surgery and other corrections. In this paper, I consider methods used to measure aberrations, the magnitude of aberrations in general populations and how these are affected by various factors (for example, age, refractive error, accommodation and refractive surgery) and how aberrations and their correction affect spatial visual performance.

Accommodation, Ocular↗

[Retrospective evaluation of PC IOL power after extracapsular cataract extraction].

PURPOSE: Retrospective evaluation of PC IOL power calculation accuracy and comparison of the refractive errors after ECCE resulted from different methods of calculation. MATERIAL AND METHODS: The PC IOL power in 100 eyes with senile cataract without significant refractive errors, was calculated using SRK II formula with two different biometers and based on primary refraction. The final IOL power was established by surgeon based on all mentioned calculations (surgeon choice). Half a year after surgery the refractive error was measured. The proper IOL power, which did not require additional correction, was calculated (ideal lens). RESULTS: 48 eyes did not require any distance correction. In 44 eyes small hyperopia (to +2.0 D) appeared and in 8 eyes myopia (to -1.5 D). The smallest error was made in cases where we implanted lenses according to surgeon choice. The average power of ideal lens was 20.32 D. We observed statistically significant difference between both ultrasound biometers. CONCLUSIONS: The most accurate results were achieved in cases where IOL power was chosen by the surgeon based on SRK II formula and primary refraction. Possible source of errors can be inadequate indications of biometers.

Aged↗

Factors influencing the outcome of strabismus surgery in patients with exotropia.

PURPOSE: To determine the factors associated with favorable and less favorable outcomes in strabismus surgery for treatment of exotropia and to show the factors influencing the efficacy of the surgical procedure. METHODS: Case files of 225 patients with a diagnosis of primary exotropia were evaluated. Information about patient age at onset of deviation, patient age at surgery, interval between onset and surgery, preoperative deviation, refractive errors, degree of anisometropia, visual acuity, presence of amblyopia, presence of an A- or a V-pattern, amount of surgery performed, type of exotropia (intermittent or constant), and existence of binocular single vision before surgery were obtained and evaluated using multiple regression analysis. RESULTS: Preoperative deviation and refractive errors were proved to be significant factors influencing a favorable outcome in patients with surgically treated exotropia (r(2) = 0.12, P <.001, and r(2) = 0.07, P <.001 respectively). Preoperative deviation, amount of surgery performed, and refractive errors shifting toward myopia significantly influenced the efficacy of the surgery performed (r(2) = 0.31, 0.06, and 0.025, respectively). CONCLUSION: Special care should be paid to refractive errors in patients with exotropia before determining the amount of surgical intervention.

Child, Preschool↗

Corneal asphericity and apical curvature in children: a cross-sectional and longitudinal evaluation.

PURPOSE: The contour of the human cornea is closely modeled by a conic section, which is fully described by asphericity (Q) and apical radius of curvature (r(o)). The relationship between corneal shape and other ocular dimensions in children, including anterior and vitreous chamber depths, axial length, and spherical equivalent refractive error, was investigated. METHODS: Corneal asphericity and r(o) were calculated by using corneal topography data on 643 children (72 myopes, 370 emmetropes, and 201 hyperopes), ages 6 to 15 years, who participated in the Orinda Longitudinal Study of Myopia (OLSM) during 1991. Measurements from a younger subset of these children, including 8 myopes, 92 emmetropes, and 75 hyperopes, ages 6 to 9 years in 1991, were compared to 1996 data for longitudinal analysis. RESULTS: Mean +/- SD Q of the 1991 study sample was -0.346 +/- 0.101, representing a prolate corneal shape. Almost all (99.7%) of the corneas examined were prolate. Corneal asphericity was less prolate among myopes than in emmetropes and hyperopes (P = 0.010). Less prolate corneas were related to deeper anterior chamber depths among emmetropes (r = 0.324, P < 0.0001) and hyperopes (r = 0.275, P < 0.0001), but not among myopes (r = 0.230, P = 0.0515). Flatter values of r(o) were related to longer vitreous chamber depth (r = 0.607, P < 0.0001) and axial length (r = 0.606, P < 0.0001) in all refractive error groups. Initial corneal shape was unrelated to change in refractive error over a 5-year period. CONCLUSIONS: Most corneas examined in this study were prolate in contour. Deeper anterior chamber depths were related to less prolate corneas among emmetropes and hyperopes, which is probably the result of mechanical influences on the peripheral cornea as the anterior chamber elongates during ocular growth. Longitudinal results suggest initial corneal shape is of little or no value in predicting refractive error progression.

Adolescent↗

One-year outcomes of a bilateral randomized prospective clinical trial comparing laser subepithelial keratomileusis and photorefractive keratectomy.

PURPOSE: To compare laser subepithelial keratomileusis (LASEK) and photorefractive keratectomy (PRK) in different eyes of the same patients in terms of visual acuity, refractive error, and complications over 1 year. METHODS: This prospective, randomized, double-masked study comprised 30 active-duty military personnel with myopia who underwent LASEK in one eye and PRK in the other eye. RESULTS: Twenty-eight patients' results were available for 1-year follow-up. The primary outcome measures were visual acuity and refractive error. The mean visual acuity for the LASEK group was 1.56 and 1.67 for the PRK group (z = -0.18, P = .15). The mean spherical equivalent refraction for the LASEK group was -0.007 D and +0.124 D for the PRK group (t = 0.982, P = .40). No significant differences were noted in visual acuity or refractive error in the eyes that had LASEK versus the eyes that had PRK. CONCLUSIONS: After 1-year follow-up, LASEK and PRK show similar levels of visual acuity and refractive error.

Adult↗

[Clinical evaluation of modifications of the SRK formula].

It was previously reported that the axial length and the refractive error were analyzed in selecting intraocular lens powers which were calculated by the SRK formula. Moreover, the predicted postoperative refraction was compared with the actual postoperative refraction. Two modifications of the SRK formula were derived from these relationships as follows; Modified SRK formula 1: R = 0.98 (P-I)-0.16L + 4.48, Modified SRK formula 2: R = 0.82 (P-I)-0.21L + 5.39. The modifications of the SRK formula were evaluated in 200 other eyes after posterior chamber lens implantation. As a result, the average refractive error was + 0.397 +/- 0.585D by the standard SRK formula, but it decreased by an average numbers of + 0.037 +/- 0.557D and + 0.047 +/- 0.547D respectively by modified SRK formulae 1 and 2. While the incidence of deviation within +/- 1.0D was 87.0% for the standard SRK formula, it was 94. 5% for both modified SRK formulas. The refractive errors, moreover, were less dependent on the axial length with both modified SRK formulae. The predicted postoperative refraction was more accurate by modified SRK formulae, especially between emmetropia and myopia up to 0.5 diopters.

Adult↗

Clinical comparison of the visual parameters in infants with intrauterine growth retardation vs. infants with normal birth weight.

We measured vision function in a number of 7-month-old infants with intrauterine growth retardation (IUGR) and compared these findings to those for 7-month-old infants of normal birth weight. The IUGR infants had an average visual acuity of 6/162 (20/540) and an average spherical refractive error of 1.49 D hyperopia. The normal birth weight infants had an average visual acuity of 6/118.8 (20/396) and an average spherical refractive error of 0.94 D hyperopia. However, the differences between the infant groups for visual acuity and refractive error were not statistically significant. Anisometropia, astigmatism, and strabismus were infrequent for both infant groups. The results of this study suggest that IUGR infants have visual abilities resembling those of normal birth weight infants.

Astigmatism↗

Inhibitory effects of apomorphine and atropine and their combination on myopia in chicks.

PURPOSE: The inhibitory effect of apomorphine on form-deprivation myopia implies a role for dopaminergic pathways in eye growth; however, the effect of apomorphine on lens-induced changes has not been studied. Our study filled this deficiency. After establishing that apomorphine inhibited lens-induced myopia, we investigated whether apomorphine and atropine acted sequentially via the same control pathway or via different parallel pathways. METHODS: This study, conducted in 8-day-old chicks, was comprised of two parts: (1) a comparative study of apomorphine's effect on lens-induced myopia (-15 D), form-deprivation myopia (diffusers), and lens-induced hyperopia (+15 D) and (2) a study of the interacting effects of apomorphine and atropine on lens-induced myopia and form-deprivation myopia. In the first part, dH2O and six apomorphine doses (8 pmole to 800 nmole in log10 steps) were given as 10-microL intravitreal injections in combination with the above visual treatments. Apomorphine was used alone or given with atropine in the second part, which included four drug treatment groups: (1) control (dH2O); (2) 80 pmole of apomorphine; (3) 18 nmole of atropine; and (4) apomorphine + atropine. Additional dH2O injections were used to equalize the number of injections across groups. After 4.5 days of treatment, refractive errors and axial ocular dimensions were measured. RESULTS: The myopic shifts and axial elongation typical of lens-induced myopia (-15 D lens wear) were inhibited to maxima of 43% (4.5 D) and 52% (0.17 mm) by apomorphine, which, in contrast, enhanced lens-induced hyperopia (refractive error: 114%, 1.55 D; axial length: 134%, 0.16 mm). Inhibitory effects of apomorphine on lens-induced myopia were observed at doses > or = 80 pmole, whereas the doses required to enhance lens-induced hyperopia were 2 log10 units higher. Only a weak inhibitory effect of apomorphine on form-deprivation myopia was observed. Although both apomorphine and atropine inhibited lens-induced myopia, atropine was slightly more effective for the doses compared (refractive error, 53% cf. 32%), and the effect of the combination was not significantly greater than that of atropine alone (refractive error, 59% cf. 53%). CONCLUSIONS: Apomorphine inhibits both types of experimental myopia, which implies the involvement of dopaminergic mechanisms in both phenomena; likewise, cholinergic mechanisms are indicated by the inhibitory effects of atropine on both lens-induced myopia and form-deprivation myopia. We speculate that apomorphine and atropine act at different sites on a common control pathway because the combined effect of apomorphine and atropine was no more than atropine alone.

Animals↗