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PubMed2001

Non-cycloplegic screening for refractive errors in children with the hand-held autorefractor Retinomax: final results and comparison with non-cycloplegic photoscreening.

AIMS: To establish the results of refractive screening of preschool children with the hand-held autorefractor Retinomax under non-cycloplegic conditions, and to compare these results with those of photoscreening. METHODS: Among 1218 children undergoing non-cycloplegic refractive screening, 302 (25%) were also refracted under cycloplegia using the same refractor and were used as controls. Our criteria for a positive screening test were based on the spherical or cylinder values and were: myopia over 3D, astigmatism > or = 2D, spherical or cylindrical anisometropia > or = 1.5D, and hyperopia > or = 1.5D. Absolute myopia over 3D, absolute astigmatism > or = 2D, absolute anisometropia > or = 1.5D and absolute hyperopia > 3.5D were considered as true positives. The sensitivity, specificity, and positive and negative predictive values (PPV and NPV) were calculated within the group of controls for each refractive anomaly. On the basis of Bayes' theorem, these figures were then corrected to yield the true screening results that would be expected in a population without verification and selection bias. To determine the usefulness of this screening technique, the likelihood ratios for positive test results (+LR) were also calculated. The results of this screening in terms of sensitivity, specificity and predictive values were then compared with those of photoscreening. RESULTS: The basic results of screening with the hand-held autorefractor were as follows: -EHyperopia: sensitivity 46%, specificity 97%, PPV 55%, NPV 96%, +LR 15; -EAstigmatism: sensitivity 37%, specificity 99%, PPV 69%, NPV 96%, +LR 37; -EAnisometropia: sensitivity 66%, specificity 93%, PPV 19%, NPV 99%, +LR 9; -EMyopia: sensitivity 87%, specificity 99%, PPV 33%, NPV 100%, +LR 87. The comparison with photoscreening revealed a similar performance when screening for hyperopia, but the hand-held autorefractor yielded much better figures when screening for astigmatism. In the case of myopia and anisometropia, the lack of consistent information concerning photoscreening invalidates any comparison. CONCLUSION: The hand-held autorefractor Retinomax appears to have potential as a screening device. Our experience with the non-cycloplegic screening of preschool children for refractive anomalies indicates definite usefulness and reasonable accuracy of the Retinomax for detecting myopia, astigmatism and hyperopia. The weak point of this screening technique is the diagnosis of anisometropia, with only moderate utility and poor accuracy.

Bayes Theorem↗
PubMed2004

The age- and gender-specific prevalences of refractive errors in Tehran: the Tehran Eye Study.

PURPOSE: To determine the age- and gender-specific prevalences of refractive errors in Tehran through a population-based study. METHODS: A total of 6497 citizens representing a cross-section of the population of Tehran were sampled from 160 clusters using a stratified, random, cluster sampling strategy. Eligible people were enumerated through a door-to-door household survey in the selected clusters and were invited to participate. All participants were transferred to a clinic for an extensive eye examination and interview. Refractive error was determined using manifest and cycloplegic refraction. Myopia was defined as the spherical equivalent of -0.5 diopters (D) or more and hyperopia was defined as the spherical equivalent of more than +0.5 D. RESULTS: Of those sampled, 4565 (70.3%) people participated in the study. Refraction data for 4354 participants aged five years and over are presented. The age- and gender-standardized prevalence of myopia based on manifest refraction was 21.8% (95% confidence interval [CI], 20.1 to 23.5) and that for hyperopia was 26.0% (95% CI, 24.5 to 27.6). The prevalences based on cycloplegic refraction were 17.2% (95% CI, 15.6 to 18.8) and 56.6% (95% CI, 54.7 to 58.6), respectively. Prevalences of myopia and hyperopia differed significantly among the age and gender groups (P < 0.001). Astigmatism of 0.75 cylinder diopter or greater was present in 29.6% (95% CI, 28.0 to 31.3) of right eyes with manifest refraction and in 30.3% (95% CI, 28.5 to 32.1) with cycloplegic refraction. Among the study population, 6.1% (95% CI, 5.3 to 6.8%) had anisometropia of 1 D or more. CONCLUSIONS: This report has provided details of the refractive status in the population. We have documented prevalences of myopia, hyperopia, astigmatism and anisometropia by age and gender, identifying more affected age- and gender-groups for prevention programs in the community.

Adolescent↗
PubMed2000

Development of refraction and strabismus.

Research on the etiology and causes of refractive errors has become a very active field of study during the past few years. Most of this research has focused on myopia. But hyperopia and astigmatism are also being examined both in comparison to myopia and in their own right. Animal models have also been developed for the study of experimentally induced myopia and hyperopia. These studies demonstrate the chain of neural and molecular events that occurs in induced myopia and hyperopia with increasing precision. In the future, these results may elucidate the mechanisms that underlie the refractive errors seen in human populations. Research into the development of strabismus has not progressed with the same vigor. The links among hyperopia, accommodative convergence, and strabismus are well established. Numerous neural, oculomotor, and subjective correlates of strabismus are now well established, but there has been a failure to develop the experimental paradigms needed to demonstrate the causal relations among these different factors.

Adaptation, Ocular↗
PubMed2006

Ocular findings in four children with mucopolysaccharidosis I-Hurler (MPS I-H) treated early with haematopoietic stem cell transplantation.

PURPOSE: To present visual functions and ocular findings in four children with mucopolysaccharidosis I-Hurler (MPS I-H) treated early with stem cell transplantation (SCT). METHODS: Clinical ophthalmological evaluations including visual evoked potentials (VEPs) were carried out. RESULTS: Stem cell transplantation was performed before 20 months of age. Ocular follow-up lasted 1.3-5.6 years (median 4.1 years). Reductions in corneal opacities were observed in all four children post-SCT, but a slight cloudiness persisted. Decreased visual acuity and high hyperopia (median + 6.25 dioptres, range + 4.0 D to + 7.5 D spherical equivalents) were noted in all children. Hyperopia was initially undetected due to dull retinal reflexes and photophobia. Two children developed esotropia, one with amblyopia. Keratometry, performed in two children, demonstrated subnormal values with a mean of 39.33 D (range 37.62-41.00 D). Visual evoked potentials and intraocular pressures were normal. Neither cataract nor dry eye were detected during follow-up. CONCLUSIONS: Early SCT appears to be beneficial in reducing, but not eliminating, corneal opacities in children with MPS I-H. Subjects are at risk of developing high hyperopia and esotropia. Hyperopia might be caused by the storage of glucosaminoglucans that increase corneal rigidity, thereby straightening the curvature of the cornea and reducing refractive power. As early diagnosis and treatment are very important, paediatric ophthalmologists should remember to rule out MPS I-H in children with corneal opacities.

Child↗
PubMed2003

Refractive errors in an elderly Chinese population in Taiwan: the Shihpai Eye Study.

PURPOSE: Few epidemiologic data are available on refractive status in elderly Asians. The purpose of the study was to determine prevalence and risk factors associated with refractive errors in a metropolitan elderly Chinese population in Taiwan. METHODS: A population-based survey was conducted in the Shihpai district of Taipei, Taiwan. A total of 2045 residents aged 65 years or more were randomly selected and invited to complete a comprehensive questionnaire and undertake a detailed ocular examination, including best corrected visual acuity and measurements of refractive error, using autorefraction. Of the subjects, 1361 (66.6%) participated in the ocular examination. Spherical equivalent (SE) was calculated in diopters (D), and data from right eyes were reported. RESULTS: The age- and sex-adjusted prevalence rates were determined for myopia (SE<-0.5 D, 19.4%; SE<-1.0 D, 14.5%), high myopia (SE<-6.0 D, 2.4%), hyperopia (SE>+0.5 D, 59.0%; SE>+1.0 D, 44.2%), astigmatism (cylinder<-0.5 D, 74.0%; cylinder<-1.0 D, 45.3%), and anisometropia (SE difference between right and left eyes>0.5 D, 45.2%; SE difference>1.0 D, 21.8%). The prevalence of myopia, astigmatism, and anisometropia significantly increased with age (all P<0.01). The prevalence of hyperopia tended to decrease with age. There was no gender difference in prevalence rates in any type of refractive error, except that women had a higher rate of hyperopia (SE>+1.0 D) than men (P=0.004). Multivariate regression analysis showed that myopia was weakly associated with higher educational level. The severity of lens nuclear opacity was positively associated with the rates of myopia and negatively associated with the rates of hyperopia. CONCLUSIONS: The prevalence of myopia in this elderly Chinese population is not much higher than in similarly aged elderly white populations, compared with a much greater difference in prevalence among younger Chinese versus white people. This suggests that changing environmental factors may account for the increased prevalence of myopia in younger cohorts of Chinese.

Age Distribution↗
PubMed2002

Refractive error in children in an urban population in New Delhi.

PURPOSE: To assess the prevalence of refractive error and related visual impairment in school-aged children in an urban population in New Delhi, India. METHODS: Random selection of geographically defined clusters was used to identify a sample of children 5 to 15 years of age. From December 2000 through March 2001, children in 22 selected clusters were enumerated through a door-to-door survey and examined at a local facility. The examination included visual acuity measurements, ocular motility evaluation, retinoscopy and autorefraction under cycloplegia, and examination of the anterior segment, media, and fundus. Myopia was defined as spherical equivalent refractive error of at least -0.50 D and hyperopia as +2.00 D or more. Children with reduced vision and a sample of those with normal vision underwent independent replicate examinations for quality assurance in four of the clusters. RESULTS: A total of 7008 children from 3426 households were enumerated, and 6447 (92.0%) examined. The prevalence of uncorrected, baseline (presenting), and best corrected visual acuity of 20/40 or worse in the better eye was 6.4%, 4.9%, and 0.81%, respectively. Refractive error was the cause in 81.7% of eyes with vision impairment, amblyopia in 4.4%, retinal disorders in 4.7%, other causes in 3.3%, and unexplained causes in the remaining 5.9%. There was an age-related shift in refractive error from hyperopia in young children (15.6% in 5-year-olds) toward myopia in older children (10.8% in 15-year-olds). Overall, hyperopia was present in 7.7% of children and myopia in 7.4%. Hyperopia was associated with female gender. Myopia was more common in children of fathers with higher levels of education. CONCLUSIONS: Reduced vision because of uncorrected refractive error is a major public health problem in urban school-aged children in India. Cost-effective strategies are needed to eliminate this easily treated cause of vision impairment.

Adolescent↗
PubMed1992

Refractive plasticity of the developing chick eye.

We have developed a lightweight plastic goggle with rigid contact lens inserts that can be applied to the eyes of newly hatched chicks to explore the range and accuracy of the developmental mechanism that responds to retinal defocus. Convex and concave lenses of 5, 10, 15, 20 and +30 D were applied to one eye on the day of hatching. The chick eye responds accurately to defocus between -10 and +15 D, although hyperopia develops more rapidly than myopia. Beyond this range there is first a levelling off of the response and then a decrease. The resulting refractive errors are caused mainly by increases and decreases in axial length, although high levels of hyperopia are associated with corneal flattening. If +/- 10 D defocusing lenses are applied nine days after hatching the resulting myopia and hyperopia are equal to about 80% of the inducing power. After one week of inducing myopia and hyperopia with +/- 10 D lenses, the inducing lenses were reversed. In this case, the refractive error did not reach the power of the second lens after another week of wear. Instead, astigmatism in varying amounts (0-12 D) was produced, being greater when reversal was from plus to minus. Finally, astigmatism can also be produced by applying 9 D toric inducing lenses on the day of hatching. The astigmatism produced varies from 2 to 6 D, and the most myopic meridian coincides with the power meridian of the inducing lens. This astigmatism appears to be primarily due to corneal toricity.(ABSTRACT TRUNCATED AT 250 WORDS)

Accommodation, Ocular↗
PubMed2003

[Indications for refractive procedures in adult patients with strabismus and results of the subsequent therapeutic procedures].

The authors estimated the contribution of the refraction intervention and a possible evolution in the position of eyes in 102 adult individuals considering a refraction intervention. The indications for this intervention were a disorder in eye position or amblyopia in those who were interested in this operation and were examined in the years 1996 to 2002. The basic refraction examination was always supplemented by a detailed orthoptic analysis. Based on this examination the intervention was not recommended in 14 examined subjects (14%). ARK represented the contraindication of the refraction intervention in 9 patients, since subsequent changes in the size of the deviation or operation adjustment of strabismus could result in diplopia. An excessive convergence with a high AC/A in hyperopia was also considered as an unsuitable indication, since a lasting cosmetic and functional significant convergent deviation into near distances could not be excluded. Five patients declined from the refraction intervention on the basis of this explanation. The paper is mainly dealing with an analysis of the development of position of the eyes and binocular functions in 46 adult patients, who decided to undergo a refraction intervention and further orthoptic care after a complex stroboscopic and refraction examination. The adjustment of refractive error was made by the LASIK methods (Laser in Situ Keratomileusis) on 69 eyes (80%) and CLE (Cleans Lens Extraction) on 17 eyes (20%). The orthoptic analyses before and the refraction intervention revealed that in all 29 even only partially accommodating esotropia, the deviation was diminished after the refraction intervention on the average by +11.2 degrees (in the rage of +2 degrees to +30 degrees) to 5.4 degrees (in the range of parallel position to +20 degrees) in the predominantly represented hyperopia, but also in 6 myopias. The improved position of the bulbs was not directly associated with the degree of hyperopia with the original deviation. The deviation after the refraction intervention in 23 patients (79%) with esotropia was not higher than degrees. The cosmetic position of the eyes was completely satisfactory and did not therefore represent even indication for the operation. The 9 patients (35%) with esotropia and hyperopia there were an improvement of binocular functions. It could be theoretically due to the newly developed emetropia making permanent optimal sensory information possible. In all 17 exotropias there were not any significant changes in the size of deviation and the binocular functions were not reestablished, if they were not retained before. The position of eyes was solved surgically in 12 patients, while exotropia predominated in two thirds of them. The weakening or strengthening interventions on horizontal straight muscles were selected according to character of strabismus in 11 patients. Recession of the lower oblique muscle was indicated one case only for the simultaneously present torticollis with exotropia. The residual deviation was not greater than 5 degrees immediately after the operation or during the following months. Binocular functions were not reestablished in any patients. A alternate suppression or suppression of perception on one eye were proved.

Adult↗
PubMed2004

Duration and effect of single-dose atropine: paralysis of accommodation in penalization treatment of functional amblyopia.

BACKGROUND AND PURPOSE: Atropine dilates the pupil and paralyzes the ciliary muscle accommodation, blurring vision, and therefore is an effective penalization of the sound eye in the treatment of functional amblyopia of the other eye. The degree of blur induced is a function of the amount of the patient's uncorrected hyperopia and the distance from the eye of the viewed material or object. Another factor determining effectiveness of atropine penalization is the duration of the effect of the atropine. It is the purpose of this study to investigate these factors. METHODS: Six normal children underwent complete eye exam with cycloplegic refraction several days before deliberate instillation of atropine 1% in the sound, or right eye. Distance and near acuity was then tested after 30 minutes, and on subsequent days. Additional data points were derived by placing known minus lenses in front of the tested eye. In addition, we also studied one successfully treated amblyopic patient when he terminated chronic daily atropine in his normal, sound eye. RESULTS: Atropine initially produced a linear reduction in logMAR acuity (blur) at distance of about 0.2 logMAR lines per diopters of uncorrected hyperopia. The magnitude of the blur was greater for near, but the effect of increased hyperopia was slightly greater for distance measurements. This blurring of acuity lasted just less than 48 hours for normal subjects, and just over 48 hours following prompt cessation of chronic daily atropine in that one subject. Regression formulae were derived relating uncorrected hyperopia and time interval following atropine cessation on distance and near acuity in children of amblyopic age range. CONCLUSION: The degree of penalization is highly dependent on the uncorrected hyperopic refractive error. A significant penalization effect is present only for one day or so. Daily atropine is therefore indicated for penalization. To better tailor penalization therapy to target sound eye acuity blur, these formulae and graphs can be used, specifically, in addition, to determine the amount of deliberate spectacle hyperopic undercorrection to maximize the penalization effect.

Accommodation, Ocular↗
PubMed1994

Refractive surgery.

Myopia (nearsightedness) and hyperopia (farsightedness) are almost equally distributed in the general population but myopia has received the most surgical attention, probably because it produces the greater disability. It also seems more amenable to surgical correction as the widespread successful employment of radial keratotomy bares out. On the other hand, attempts at surgically correcting hyperopia such as hexagonal keratotomy; thermokeratoplasty; hyperopic lamellar keratotomy, and keratophakia have had a less happy experience. Even the more sophisticated technique of laser photoablation is unable to successfully manage hyperopia. It would seem that steepening the cornea is much more difficult than flattening it. Refractive eye surgery is a new subspecialty of ophthalmology only recently come into its own. Considering the tremendous changes in cataract surgery in the past 30 years it is likely that hyperopia will eventually fall to the refractive eye surgeon.

Corneal Transplantation↗
PubMed1998

Refractive error and age-related maculopathy: the Blue Mountains Eye Study.

PURPOSE: To assess associations between refractive error (hyperopia, myopia, and spherical equivalent [SEq]) and age-related maculopathy (ARM) in an older population. METHODS: A population-based survey examined 3654 people aged 49 years or older, 82% of whom were permanent residents in an area west of Sydney, Australia. Participants had a detailed eye examination, including standardized refraction and stereo macular photographs. ARM was diagnosed from blinded photographic grading. Autorefractor measurements and subjective refraction were used to assess SEq refractive error for each eye in diopters. Mean SEq of the two eyes was used to define emmetropia, myopia, and hyperopia in each person. RESULTS: After known ARM risk factors (age, sex, ARM family history, current smoking) had been adjusted for, no association was found between mean SEq (two eyes) and late ARM (odds ratio [OR], 1.0; 95% confidence interval [CI], 0.9-1.1). However, a statistically significant increased risk of early ARM was found for each diopter of increase in mean SEq (OR, 1.1; CI, 1.0-1.2). In logistic regression models, moderate to high hyperopia was significantly associated with increased early ARM risk (OR, 2.0; CI, 1.2-3.4). When a generalized estimating equation model (GEE), which assessed the relationship at eye level while accounting for the correlation between the two eyes, was used, this association was marginally insignificant (OR, 1.3; CI, 0.9-1.9). No significant associations were found between myopia and any ARM stage with either model. CONCLUSIONS: These population-based data suggest a weak association between hyperopia and early ARM.

Age Distribution↗
PubMed2003

Axial length-disc area ratio in esotropic amblyopia.

BACKGROUND: Hyperopia is a risk factor for esotropia and amblyopia. A previous study indicated that disc areas (DAs) are reduced in patients with amblyopia. OBJECTIVE: To determine if there is a difference in the relative size of the optic disc in hyperopic eyes without strabismus or amblyopia compared with esotropic and amblyopic eyes, the relationship of axial length (AXL) to DA in subjects with hyperopia was evaluated. METHODS: Eight hundred fifty records from my private practice, which included AXL measurements and optic disc photographs or digital images, were analyzed to locate 122 subjects with bilateral refractive errors greater than +2.00 diopters. Disc areas were measured using objective techniques. Axial lengths were determined by ultrasonographic biometry. A ratio, AXL/DA, was derived by dividing the AXL in millimeters by the DA in square millimeters. RESULTS: The mean (SD) AXL/DA for the group with hyperopia was 9.48 (2.70) mm and 12.30 (3.45) mm for the group with hyperopic strabismus (P =.01). The mean (SD) AXL/DA was 15.24 (4.61) mm in the amblyopic eyes and 13.61 (3.67) mm for the nonamblyopic fellow eye (P =.02). CONCLUSION: The optic discs of eyes with hyperopic strabismus with and without amblyopia were disproportionately and markedly reduced when compared with hyperopic eyes without amblyopia or esotropia.

Adult↗
PubMed2003

Refractive error and ethnicity in children.

OBJECTIVE: To report the baseline prevalence of refractive error in the study population. DESIGN: A multicenter, longitudinal, observational study of refractive error and ocular development in children from 4 ethnic groups. PATIENTS AND METHODS: The study population included 2523 children (534 African American, 491 Asian, 463 Hispanic, and 1035 white) in grades 1 to 8 (age, 5-17 years). Myopia was defined as -0.75 diopters (D) or more and hyperopia as +1.25 D or more in each principal meridian, and astigmatism was defined as at least a 1.00-D difference between the 2 principal meridians (cycloplegic autorefraction). RESULTS: Overall, 9.2% of the children were myopic, 12.8% were hyperopic, and 28.4% were astigmatic. There were significant differences in the refractive error prevalences as a function of ethnicity (chi2, P<.001), even after controlling for age and sex (polychotomous logistic regression, P<.001). For myopia, Asians had the highest prevalence (18.5%), followed by Hispanics (13.2%). Whites had the lowest prevalence of myopia (4.4%), which was not significantly different from African Americans (6.6%). For hyperopia, whites had the highest prevalence (19.3%), followed by Hispanics (12.7%). Asians had the lowest prevalence of hyperopia (6.3%) and were not significantly different from African Americans (6.4%). For astigmatism, Asians and Hispanics had the highest prevalences (33.6% and 36.9%, respectively) and did not differ from each other (P =.17). African Americans had the lowest prevalence of astigmatism (20.0%), followed by whites (26.4%). CONCLUSION: There were significant differences in the prevalence of refractive errors among ethnic groups, even after controlling for age and sex (P<.001).

Adolescent↗
PubMed2004

Intracorneal inlay complicated by intrastromal epithelial opacification.

OBJECTIVE: To report epithelial perilenticular opacity as a new complication of intracorneal inlay implantation for the correction of hyperopia. DESIGN: Prospective observational case series. PARTICIPANTS: Eleven eyes of 7 patients underwent intracorneal inlay implantation for the correction of hyperopia. METHODS: Intracorneal inlays were implanted onto the stromal bed by using a microkeratome cut to create an inferior hinged corneal flap. MAIN OUTCOME MEASURES: Postoperative complication occurrence of intracorneal perilenticular opacity, microbiological laboratory analysis, histopathological analysis, and confocal microscopy study. RESULTS: Of 11 implanted eyes, 5 showed diffuse perilenticular opacity of varying intensity that was unresponsive to steroid use following intracorneal inlay implantation. All patients had moderate to severe loss of best-corrected visual acuity. The inlays showed deposits at the edge and on the surface. Confocal microscopy in all eyes produced images compatible with the confocal morphologic features of epithelial cells. Explantation of inlays was performed in 5 eyes. The histopathologic study showed the presence of epithelial cells, and microbiological analysis and cultures were negative for bacteria, fungi, and mycobacteria. CONCLUSION: Epithelial perilenticular opacity is a new and serious complication in patients with intracorneal inlay implantation for the correction of hyperopia.

Adult↗
PubMed1995

Choroidal and scleral mechanisms of compensation for spectacle lenses in chicks.

It is known that when hyperopic or myopic defocus is imposed on chick eyes by spectacle lenses, they rapidly compensate, becoming myopic or hyperopic respectively, by altering the depth of their vitreous chamber. Changes in two components--ocular length and choroidal thickness--underlie this rapid compensation. With monocular lens treatment, hyperopic defocus imposed by negative lenses resulted in substantially increased ocular elongation and a slight thinning of the choroid, both changes resulting in myopia; myopic defocus imposed by positive lenses resulted a dramatic increase in choroidal thickness, which pushed the retina forward toward the image plane, and a slight decrease in ocular elongation, both changes resulting in hyperopia. The refractive error after 5 days of lens wear correlated well with vitreous chamber depth, which reflected the changes in both choroidal thickness and ocular length. The degree of compensation for lenses was not affected by whether the fellow eye was covered or open. Both form-deprivation myopia and lens-induced myopia declined with age in parallel, but wearing a -15 D lens produced more myopia than did form deprivation. The spectacle lenses affected the refractive error not only of the lens-wearing eye, but also, to a much lesser degree, of the untreated fellow eye. At lens removal refractive errors were opposite in sign to the lense worn, and the subsequent changes in choroidal thickness and ocular length were also opposite to those that occurred when the lenses were in place. In this situation as well, effects of the spectacle lenses on the fellow eyes were observed. Eyes with no functional afferent connection to the brain because of either prior optic nerve section or intraocular tetrodotoxin injections showed compensatory changes to imposed defocus, but these were limited to compensation for imposed myopic defocus, at least for the eyes with optic nerve section. In addition, optic nerve section, but not tetrodotoxin treatment, moved the set-point of the visual compensatory mechanism toward hyperopia. Optic nerve section prevents myopia in response to negative lenses but not to diffusers, suggesting that compensation for hyperopia requires the central nervous system.

Animals↗
PubMed2006

Intacs adjustment surgery for keratoconus.

PURPOSE: To describe the visual outcome of keratoconic eyes managed with Intacs (Addition Technology, Inc.) that required additional Intacs surgery (defined as any combination of removal, exchange, addition, or shifting of an Intacs segment). SETTING: Private refractive surgery center, Jerusalem, Israel. METHODS: This retrospective noncomparative interventional consecutive small case series studied all eyes of a cohort of 58 keratoconic eyes managed with Intacs that had additional Intacs surgery. The uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity, manifest refraction, videokeratography, and patient questionnaires on visual function were assessed. These outcome measures were compared before Intacs implantation, before Intacs adjustment, and 1 year after the final Intacs adjustment. Eyes having any intervention other than Intacs surgery were excluded. RESULTS: Of 58 keratoconic eyes managed with Intacs, 7 had additional Intacs surgery. After the initial Intacs surgery, 6 of these eyes had UCVA < or =20/100 and 1 had UCVA of 20/50. After the final Intacs adjustment, 3 eyes achieved UCVA > or =20/40, 5 achieved UCVA > or =20/70, and 2 remained <20/200. The indications for Intacs adjustments were increased astigmatism in 4 eyes, induced hyperopia (overcorrection) in 3, and undercorrection in 1. One eye had both surgically induced astigmatism and hyperopia. Induced astigmatism and hyperopia were most often managed by removing the superior segment. The undercorrected eye, having initially received a single inferior segment, was treated by implanting a superior segment. CONCLUSIONS: Approximately 10% of keratoconic eyes managed with Intacs may require Intacs adjustment surgery, which often has a good outcome.

Adult↗
PubMed2005

Ocular compensation for alternating myopic and hyperopic defocus.

During development, the eye grows under visual feedback control, as shown by its compensating for defocus imposed by spectacle lenses. Under normal conditions the sign and magnitude of defocus vary with viewing distance, accommodative status and other factors. To explore how periods of myopic and hyperopic defocus are integrated over time we presented rapidly alternating episodes of myopic and hyperopic defocus by sequentially illuminating a nearby scrim and the wall beyond it to chick eyes wearing lenses that put the far point between the two surfaces. We found that equal periods of myopic and hyperopic defocus generally led to compensatory hyperopia, showing that myopic defocus had a disproportionate effect. Furthermore, the degree of hyperopia depended on the frequency of alternation: low frequencies (1 cycle/30 min) resulted in more hyperopia, whereas at high frequencies (1 cycle/s) the myopic and hyperopic defocus nearly cancelled each other. If similar temporal integration effects apply to humans, they may help explain why brief accommodation events may not influence lens-compensation and why a child's total reading time may be a poor predictor of myopic progression.

Accommodation, Ocular↗
PubMed2003

Refractive errors, intraocular pressure, and glaucoma in a white population.

OBJECTIVE: To examine the relation of refractive errors to glaucoma and intraocular pressure (IOP) in a defined white population. DESIGN: Population-based cross-sectional and follow-up study. PARTICIPANTS: Persons aged 43 to 86 years living in Beaver Dam, Wisconsin (n = 4926). METHODS: All participants received a standardized assessment of refraction, IOP, and glaucoma at baseline (1988-1990), with IOP remeasured 5 years later (1993-1995). Refraction was defined at baseline as follows: myopia as spherical equivalent of -1.00 diopters (D) or less, emmetropia as -0.75 to +0.75 D, and hyperopia as +1.00 D or more. MAIN OUTCOME MEASURES: Relation of baseline refraction to prevalent glaucoma (defined from IOP, optic disc, and visual field criteria) and incident ocular hypertension (defined as IOP more than 21 mmHg at the 5-year examination in eyes with IOP of 21 mmHg or less at baseline). RESULTS: A myopic refraction was correlated with increasing IOP at baseline (P < 0.001). After controlling for age and gender, persons with myopia were 60% more likely to have prevalent glaucoma than those with emmetropia (odds ratio [OR], 1.6; 95% confidence interval [CI], 1.1, 2.3). In contrast, controlling for age, gender, and baseline IOP, persons with hyperopia were 40% more likely to have incident ocular hypertension than those who were emmetropic at baseline (OR, 1.4; 95% CI, 1.0, 2.0). Myopia was not related to incident ocular hypertension. CONCLUSIONS: In these population-based data, there was a cross-sectional association of myopia with higher IOP and prevalent glaucoma. Similar associations have been found in previous studies. Hyperopia may be associated with 5-year risk of ocular hypertension, a finding that needs further investigation.

Adult↗