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PubMed1999

Short-term repeatability of hand-held keratometry measurements.

PURPOSE: The Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) Study is a multi-center, observational investigation of ocular component and refractive error development in schoolchildren. Anterior corneal curvature is one of several ocular components which influence refractive status of the eye, and the CLEERE Study uses the Alcon Auto-Keratometer to measure corneal curvature. This report assesses the repeatability of this hand-held instrument. Previous studies have demonstrated the validity of the Alcon Auto-Keratometer; however, none have assessed its repeatability. METHODS: Sixty children were recruited from clinics affiliated with the Southern California College of Optometry and the University of Houston College of Optometry. Two sets of five hand-held keratometry measurements were obtained on the right eye of each child by one investigator at each site using the Alcon Auto-Keratometer. The two sets of measurements were performed at least 10 minutes apart. RESULTS: The mean differences between the two occasions were not significantly different from zero for either the flat or steep corneal curvature measurements regardless of the number of readings taken. The largest improvement in repeatability, primarily for the steep meridian, occurred when the first two readings were averaged. The addition of readings 3, 4, and 5 to the average did not substantially improve repeatability for either meridian. The 95% limits of agreement between the average of two readings on two occasions for the flat and steep meridians were +/-0.28 and +/-0.39 D, respectively. The 95% limits of agreement after two readings were +/-0.28, +/-0.20, and +/-0.24 D for the M, J0, and J45 vectors, respectively. CONCLUSION: The Alcon hand-held keratometer provides a repeatable measure of corneal curvature as demonstrated by short-term repeat agreement within +/-0.50 D. This level of repeatability can be achieved only by manually averaging two consecutive measurements.

Adolescent↗
PubMed2003

[The evaluation of accommodation range in patients of various age groups by WASCA wavefront aberrometer].

PURPOSE: The aim of this study was, to analyse the results of accommodation range measurement obtained in groups of patients of different age. Wavefront aberrometer was used for evaluation of accommodation range of the patients eyes. MATERIAL AND METHODS: The accommodation range was analysed in 200 eyes in 100 patients. The examined group of patients was divided into 4 groups, depending on the patients age. GROUP I--AGE: 20-30 years old; group II--age: 31-40 years old; group III--age: 41-50 years old; group IV--age: 51-60 years old. The measurements were analysed using WASCA System depend on: refractive error, sex and difference of pupil diameter for far and near vision. RESULTS: Different ranges of accommodation were obtained. We did not observe any correlation between the accommodation range and the sex and refractive error. We noticed statistically significant differences between the accommodation range and pupil diameter, as well as the patients' age. CONCLUSIONS: The WASCA System is a device, which can be used for analysis of accommodation range. This system gives us the possibility, to trace changes of eye accommodation range in the long period of time.

Accommodation, Ocular↗
PubMedDate not supplied

Reasons for not performing LASIK in refractive surgery candidates.

PURPOSE: To analyze the reasons for which LASIK was rejected in eyes of patients who requested surgical correction of their refractive errors. METHODS: A retrospective study was performed in which data pertaining to refractive and ocular status of 338 patients who presented for refractive surgery at our LASIK facility between November 2002 and December 2003 were reviewed. The reasons for not performing LASIK in cases that were rejected were also noted. RESULTS: Among the 338 patients who requested refractive surgery, 223 (66%) underwent LASIK; surgery was not performed in 115 (34%) patients. The most common reason for rejecting LASIK was suboptimal central corneal thickness (55.1%). High myopia > -12.00 diopters (18.4%), keratoconus (9.6%), and hyperopia (5.9%) were other significant reasons. CONCLUSIONS: Suboptimal corneal thickness combined with a high amount of refractive error was found to be the leading cause of rejection of patients for LASIK in India.

Adolescent↗
PubMed2001

Effects of a non-steroidal (ketorolac tromethamine) and a steroidal (dexamethasone) anti-inflammatory drug on refractive state and ocular growth.

Topical steroidal anti-inflammatory drugs (SAID) and non-steroidal anti-inflammatory drugs (NSAID) are known to affect fluid balance. The effects of twice daily topical applications of Maxidex (dexamethasone, a SAID), Acular (ketorolac, a NSAID), and saline were examined biometrically on the development of refractive errors and eye growth in chicks raised from days 3-12 wearing either a monocular +10 D, 0 D, or -10 D lens. Biometric analysis showed that neither SAID nor NSAID nor saline affected refractive error compensation but that the anti-inflammatory drugs affected eye growth. In chicks reared with a +10 D lens, dexamethasone induced a decrease in axial length (AL), vitreous chamber (VC) and anterior chamber (AC) depth, while ketorolac only induced a decrease in AC. In -10 D lens chicks dexamethasone again induced a decrease in AL and VC, but did not affect AC depth, whereas ketorolac only induced an increase in AC depth. Taken together, these results suggest that anti-inflammatory drugs can induce changes in ocular size without affecting refractive state and, as such, have implications for the management of progressive myopia.

Administration, Topical↗
PubMed1992

Instrument myopia and the resting state of accommodation.

I measured the refractive errors of 210 eyes of 105 subjects by means of the Canon Autoref R-1 and by the Nikon autorefractometer NR7000. I also measured their dark focus of accommodation (DF) with the Canon instrument. Refractive errors had similar effects on the differences between the results produced by the two autorefractometers and on the changes in DF. The differences were statistically significant. Differences between the results produced by the two autorefractometers are thought to be mainly due to instrument myopia, which itself is strongly related to the resting state of accommodation. My results indicate a hyperopic shift in high hyperopes when they are observing through an instrument.

Accommodation, Ocular↗
PubMed1996

[Ophthalmological exploration of children with Down's syndrome. Main results and comparison with a control group].

BACKGROUND: Down's Syndrome is the most frequent chromosomal aberration. There is a wide variety of symptoms. From an ophthalmological point of view, numerous alterations associated with Down's Syndrome have been described. MATERIAL AND METHODS: We have carried out a complete ophthalmic exploration on 60 children with Down's Syndrome and 60 control children. RESULTS: The first group showed a high percentage of refraction errors (90%), nystagmus (28%), strabismus (48%) and cataracts (13%). If we compare these results with those of the control group we find that the Down's group has a frequency significantly higher both in refraction errors as a whole (p < 0.001) and myopia (p < 0.01), hypermetropia (p < 0.02) and stigmatism (p < 0.001). They have also shown a frequency significantly higher of strabismus (p < 0.001). CONCLUSION: All of the observed alterations can have a negative influence on the appropriate educational development of these children. An early ophthalmological exploration would be advisable in children with Down's Syndrome.

Cataract↗
PubMedDate not supplied

The factors influencing visual development in blepharophimosis-ptosis-epicanthus inversus syndrome.

PURPOSE: To investigate the factors influencing visual development in blepharophimosis-ptosis-epicanthus inversus syndrome. MATERIALS AND METHODS: The study population comprised 20 patients with blepharophimosis-ptosis-epicanthus inversus syndrome who were referred for an oculoplastic opinion. The ocular examination included measurement of Snellen visual acuity, cycloplegic refraction, ocular movements and alignment, and the presence of amblyopia. Patients were treated with spectacle correction, occlusion therapy, strabismus surgery, and oculoplastic surgery if necessary. Minimum follow-up was 2 years. RESULTS: Nine (45%) patients had amblyopia; 5 (25%) of these patients had unilateral amblyopia and 4 (20%) had bilateral amblyopia. Six (67%) patients with amblyopia had a significant coexisting strabismus. A significant strabismus was present in 11 (55%) patients; 6 (55%) of these patients had unilateral or bilateral amblyopia. Patients with strabismus were more likely to have amblyopia than those without. A total of 14 (70%) patients had refractive error; 6 (43%) of these patients had amblyopia. CONCLUSIONS: Patients with blepharophimosis-ptosis-epicanthus inversus syndrome had a high rate of amblyopia, especially bilateral amblyopia. Patients with strabismus were more likely to have amblyopia than those without. Patients also had a high incidence of refractive errors.

Adult↗
PubMed2002

Prevalence of blindness and low vision in Malaysian population: results from the National Eye Survey 1996.

BACKGROUND: A national eye survey was conducted in 1996 to determine the prevalence of blindness and low vision and their major causes among the Malaysian population of all ages. METHODS: A stratified two stage cluster sampling design was used to randomly select primary and secondary sampling units. Interviews, visual acuity tests, and eye examinations on all individuals in the sampled households were performed. Estimates were weighted by factors adjusting for selection probability, non-response, and sampling coverage. RESULTS: The overall response rate was 69% (that is, living quarters response rate was 72.8% and household response rate was 95.1%). The age adjusted prevalence of bilateral blindness and low vision was 0.29% (95% CI 0.19 to 0.39%), and 2.44% (95% CI 2.18 to 2.69%) respectively. Females had a higher age adjusted prevalence of low vision compared to males. There was no significant difference in the prevalence of bilateral low vision and blindness among the four ethnic groups, and urban and rural residents. Cataract was the leading cause of blindness (39%) followed by retinal diseases (24%). Uncorrected refractive errors (48%) and cataract (36%) were the major causes of low vision. CONCLUSION: Malaysia has blindness and visual impairment rates that are comparable with other countries in the South East Asia region. However, cataract and uncorrected refractive errors, though readily treatable, are still the leading causes of blindness, suggesting the need for an evaluation on accessibility and availability of eye care services and barriers to eye care utilisation in the country.

Adolescent↗
PubMed2003

Incidence of visual loss in rural southwest Uganda.

BACKGROUND: Surveys have been conducted to measure prevalence of eye disease in Africa, but not of incidence, which is needed to forecast trends. The incidence of visual loss is reported in southwest Uganda. METHODS: A rural population residing in 15 neighbouring villages was followed between 1994-5 (R1) and 1997-8 (R2). Survey staff screened adult residents (13 years or older) for visual acuity using laminated Snellen's E optotype cards at each survey. Those who failed (VA >6/18) were evaluated by an ophthalmic clinical officer and an ophthalmologist. Incidence of visual loss (per 1000 person years (PY)) was calculated among those who had normal vision at R1. RESULTS: 2124 people were studied at both survey rounds (60.9% of those screened at R1); 48% were male. Participants in R1 were older (34.7 versus 31.5 years at R2, p<0.001). Visual loss in R2 occurred in 56 (2.8%) of 1997, yielding a crude incidence rate of 9.9, and an age standardised incidence rate of 13.2, per 1000 PY. Incidence of visual loss increased with age from 1.21 per 1000 PY among people aged 13-34 to 64.2 per 1000 PY in those aged 65 years or older (p for trend >0.001). The six commonest causes of visual loss were: cataract, refractive error, macular degeneration, chorioretinitis, glaucoma, and corneal opacity. If similar rates are assumed for the whole of Uganda, it is estimated that 30 348 people would develop bilateral blindness or bilateral visual impairment, per year. CONCLUSIONS: Cataract and refractive error were the major causes of incident visual loss in south west Uganda. These data are valuable for forecasting and planning eye services.

Adolescent↗
PubMed1998

Refractive changes associated with scleral buckling and division in retinopathy of prematurity.

OBJECTIVE: To examine the refractive changes that occur in infant eyes with retinopathy of prematurity (ROP) retinal detachments that are subjected to scleral buckling and subsequent division of the scleral buckle. METHODS: A retrospective medical record review of infants with ROP who were managed with an encircling scleral buckle that was subsequently divided and who underwent refraction evaluation during and after division of the scleral buckle. RESULTS: Seven eyes from 6 patients had scleral exo-plants placed for stage 4 ROP retinal detachments at a mean postconceptional age of 48 weeks. The mean refractive error in eyes with the scleral buckle was -11 diopters (D) (range, -5 to -25 D) with an induced mean anisometropia of -9.5 D. After division of the scleral buckle at a mean of 36 weeks postoperatively, the average post-scleral buckle refractive error was -5.68 D, resulting in a mean myopic reduction of 5.5 D. CONCLUSIONS: Scleral buckling in infants with ROP results in large myopic shifts, which are significantly reduced after division of the scleral buckle. This highlights the importance of repeated refraction testing in infants after placement and division of the scleral buckle to avoid refractive amblyopia.

Birth Weight↗
PubMed1997

Comparison between the refractive results of combined penetrating keratoplasty/transsclerally sutured posterior chamber lens implantation and the triple procedure.

PURPOSE: We determined how accurately we could predict the intraocular lens (IOL) power for a combined penetrating keratoplasty and transsclerally sutured posterior chamber lens implantation procedure (PK/TS-SPCL) compared with the Triple procedure (penetrating keratoplasty, extra-capsular cataract extraction, and IOL insertion). METHODS: We retrospectively evaluated the postoperative refractive results of 27 patients who had undergone PK/TS-SPCL and compared them with those of 46 patients who had undergone a Triple procedure. All patients with a final visual acuity > 20/50 who had surgery at the University of Minnesota between January 1988 and December 1993 were included in this study. RESULTS: The mean postoperative deviation from the predicted refractive error was 1.79 D for the Triple group and 1.81 D for the PK/TS-SPCL group (p = 0.95). Sixty-three percent of the Triple patients and 67% of the PK/TS-SPCL patients were within -2.00 D and +2.00 D of their predicted refractive error. As a group, the Triple patients had a mean postoperative keratometry reading of 44.64 compared with 45.58 for the PK/TS-SPCL patients (p = 0.12). CONCLUSION: These results indicate that our accuracy in predicting the IOL implant power in PK/ TS-SPCL is quite comparable with that obtained for the Triple procedure, and our refractive results for each group are quite similar.

Cataract Extraction↗
PubMedDate not supplied

Mesopic contrast sensitivity function after excimer laser photorefractive keratectomy.

PURPOSE: To evaluate contrast sensitivity under mesopic conditions in patients who had undergone uncomplicated excimer laser photorefractive keratectomy (PRK) for myopia. METHODS: Monocular contrast sensitivity function was measured with the Stereo Optical F.A.C.T. chart in 26 patients who had received PRK using the Nidek EC-5000 excimer laser system. Mean preoperative refractive error was -6.23 +/- 1.69 D (range, -4.00 to -8.25 D); postoperatively, mean refractive error was -0.36 +/- 0.58 D (range, -0.75 to +0.50 D). Contrast sensitivity function was measured 6 months after surgery using four different chart luminances: 85, 5.0, 2.5, and 0.1 cd/m2, the first being a photopic level and the rest mesopic. A control group of eight emmetropic subjects was also studied to allow comparison of results for statistical purposes. RESULTS: Logarithmic values of contrast sensitivity at each spatial frequency were used for statistical analysis and normalized values were used for graphical representation. The results showed a statistically significant reduction (P < .01) in contrast sensitivity for the PRK patients in comparison with the control group under mesopic conditions for each spatial frequency tested (1.5, 3, 6, 12, and 18 c/deg), although no significant contrast sensitivity differences were observed between PRK and control groups at the photopic (85 cd/m2) level (P > .01 for all frequencies). CONCLUSION: Photorefractive keratectomy can induce significant reductions in contrast sensitivity under mesopic conditions, even though the photopic contrast sensitivity function is normal.

Adult↗
PubMed1998

Ocular status of boys with fragile X syndrome: a prospective study.

PURPOSE: The purpose of this study was to determine whether the high rates of ocular problems described in previous retrospective reports of individuals with fragile X syndrome were present in a prospective sample of young boys. Fragile X syndrome is currently considered the leading hereditary cause of mental retardation, with prevalence estimates of 1:2500 to 1:5000 males. METHODS: Forty-eight boys with fragile X syndrome between the ages of 2.5 and 11 years were evaluated for ocular abnormalities. They received complete ophthalmic evaluations including assessment of visual acuity, cycloplegic refraction, ocular motility assessment, and dilated fundus examination. RESULTS: Approximately 25% of the children had clinically significant ocular findings that included refractive errors (17%, primarily hyperopia and astigmatism) and strabismus (8%). Of the 42 children with quantifiable visual acuities, only 1 child, with diagnoses of nystagmus and hyperopia, had a Snellen visual acuity that was not within normal limits for his age. Three of the 5 children with gross measures of visual acuity had clinically significant findings: 2 had hyperopia greater than 3.5 diopters and 1 had esotropia. The other 2 children with gross measures of acuity and the 1 child without visual acuity assessment had cycloplegic refractions of +1.25 to +1.5 and ocular motility appeared normal. CONCLUSIONS: These results suggest that previous reports of high rates of vision problems, particularly strabismus, in boys with fragile X syndrome may have resulted from selection bias. Although we did observe a higher prevalence of strabismus than that found in the general population (8% vs 0.5% to 1%), the proportion of children having strabismus in our sample was much smaller than that reported in other studies of children with fragile X syndrome (30% to 40%). However, 17% of the sample did have significant refractive errors. In addition to evaluating the ocular motility of children with fragile X syndrome, cycloplegic refraction should also be performed to determine whether refractive problems are present.

Child↗
PubMed1995

Ocular dimensions and refraction in Tibetan children.

A cross-sectional study of 404 Tibetan children (212 males, 192 females) aged 6 to 16 years was conducted in the Bouda region of Kathmandu, Napal in April, 1992. Examination procedures included retinoscopy (1% cyclopentolate HCl), keratometry A-scan ultrasonography, and video ophthalmophakometry. The mean refractive error was +1.11 D (SD: 0.56 D) at age 6 years decreasing to +0.63 D (SD: 0.34 D) at age 16 years with a prevalence of myopia in this group of 3.9%. Most children examined had low refractive errors, with 95.5% having errors in the range -0.50 to +1.50 D. Crystalline lens power decreased by 2.59 D, with an associated increase in its anterior radius of curvature of 1.98 mm and 0.49 mm in its posterior radius of curvature over the age range studied. Vitreous chamber depth increased by 0.69 mm, but no significant changes were recorded in anterior chamber depth, lens thickness, or corneal curvature. We conclude that the balance between the decrease in crystalline lens power and the increase in vitreous length is the major factor in maintaining the tendency to emmetropia in these children.

Adolescent↗
PubMed2005

Development of spherical equivalent refraction in prematurely born children during the first 10 years of life: a population-based study.

OBJECTIVE: To evaluate the development of refraction, expressed as spherical equivalents, in prematurely born children during the first 10 years of life. METHODS: Retinoscopy in cycloplegia was performed at 6 months, 2.5 years, and 10 years of age in 198 prematurely born children from a previous population-based study on the incidence of retinopathy of prematurity. Spherical equivalents were calculated. Myopia was defined as a spherical equivalent of less than 0 diopters (D), clinically significant myopia at 10 years of age as -1 D or less, and moderate or high myopia as less than -3D. Hypermetropia greater than +3 D was regarded as significant. RESULTS: There were no significant differences during the refractive development between the various subgroups of retinopathy of prematurity. Cryotreated eyes had a wider distribution of refractive errors. A multiple regression analysis revealed that the spherical equivalents at 2.5 years of age predicted clinically significant myopia (</=-1 D) at 10 years of age. CONCLUSIONS: Retinoscopies at 6 months, 2.5 years, and 10 years of age show a similar course of spherical equivalent refractive development regardless of the stage of retinopathy of prematurity. Refraction at 6 months of age is an unreliable predictor, but the refraction at 2.5 years of age seems to be a better tool for identifying refractive errors that will remain at 10 years of age.

Child↗
PubMed2003

A new fundus camera technique to help calculate eye-camera magnification: a rapid means to measure disc size.

OBJECTIVE: To find a simple means for calculating eye-camera magnification to permit estimation of true retinal object size from a retinal photograph. METHODS: The position of the focusing knob on 3 different retinal cameras (TRC-50F and TRC-50X; Topcon America Corp, Paramus, NJ; and the CR6-45NM Non-mydriatic Retinal Camera; Canon Inc, Tokyo, Japan) was measured during optic nerve photography and correlated with the refractive error, or spectacle refraction, of the subject (N = 11 for each camera). RESULTS: A strong correlation was found between focusing knob position and spectacle refraction for each of the 3 cameras tested (r = 0.96, r = 0.99, and r = 0.97, respectively). CONCLUSIONS: The focusing knob position reflects the spectacle refraction of the eye being photographed, and spectacle refraction is known to correlate well with eye-camera magnification. Therefore, focusing knob position can be used to help calculate eye-camera magnification and, hence, true retinal object size. CLINICAL RELEVANCE: The true size of the optic nerve head is important for the diagnosis of glaucoma from a retinal photograph. This technique is a simple means to calculate optic nerve head size, which may be especially useful in mass retinal photographic screening programs.

Anthropometry↗
PubMed1991

Trapezoidal keratotomy for the correction of naturally occurring astigmatism.

We performed trapezoidal keratotomy, consisting of combined nonintersecting semiradial and transverse incisions, in 64 eyes of 45 consecutive patients with naturally occurring astigmatism. The central clear zone diameter and number and length of transverse incisions were determined by the refractive error. Mean preoperative refractive astigmatism was 3.18 +/- 1.16 diopters (D) (range, 2.25 to 7.00 D). At the 1-year follow-up examination, the mean surgically corrected astigmatism determined by vector analysis was 3.70 +/- 1.50 D (range, 0.75 to 8.5 D), and the mean residual refractive astigmatism was 0.85 +/- 0.72 D (range, 0 to 4.0 D), with 64% of eyes having 1.00 D or less. The smaller the clear zone diameter, the greater the astigmatic correction. Longer transverse incisions produced more steepening of the secondary meridian. The operative complications included microperforation (5%), misalignment of surgical meridian (6%), encroachment on clear zone (5%), and inadvertent crossed incisions (11%). Trapezoidal keratotomy reduced naturally occurring astigmatism, but with only fair predictability and with some irregular astigmatism due to irregular wound healing.

Adolescent↗
PubMed1998

Staar Collamer posterior chamber phakic intraocular lens to correct myopia and hyperopia.

PURPOSE: To evaluate the efficacy, safety, stability, and predictability of implanting a collagen polymer (Staar Collamer), posterior chamber phakic intraocular lens (IOL) to correct myopia and hyperopia. SETTING: Centre for Advanced Refractive Eye Surgery at the BMI Alexandra Hospital, Cheadle, Manchester, United Kingdom. METHODS: A Staar Collamer posterior chamber phakic IOL was implanted in 25 eyes of 14 patients with a mean age of 37.9 years (range 20 to 50 years). Seven patients were men and seven, women. Sixteen were myopic and 9, hyperopic. Before treatment, each patient had a thorough evaluation including refractive, general, ocular, and social and personal histories. The examination included visual acuity, refraction, tonometry, topography, biometry, biomicroscopy, pupil size in dim illumination, and posterior segment evaluation by a vitreoretinal specialist. Patients were informed about the surgical process and expected outcome, their own expectations were discussed, and their consent to surgery was obtained. Surgical implantation was performed through a less than 3.0 mm clear corneal sutureless incision using brief general anesthesia on a day-case surgical basis. RESULTS: At 3 months postoperatively, all eyes had a significant increase in uncorrected visual acuity, allowing all but two patients (three eyes) to manage most activities without spectacles. Adjustment by incisional corneal surgery was planned for undercorrected myopic eyes (n = 3). Pupil block glaucoma and pigment deposits occurred in one patient each. CONCLUSION: In this short-term study, the posterior chamber phakic IOL was predictable, safe, and efficacious in the correction of myopic and hyperopic refractive errors, with good refractive stability. Long-term follow-up is required to validate that the absence of significant complications in most patients is a lasting phenomenon.

Adult↗