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PubMed2004

The Seoul Metropolitan Preschool Vision Screening Programme: results from South Korea.

AIM: To report on a new model of preschool vision screening that was performed in metropolitan Seoul and to investigate the distribution of various ocular disorders in this metropolitan preschool population. METHODS: Vision screening was conducted on 36 973 kindergarten children aged 3-5 years in a stepwise manner. The first step was home screening using a set of five picture cards and a questionnaire. The children who did not pass the first step (VA <0.5 in at least one eye or any abnormal responses on the questionnaire) were retested with regular vision charts at the regional public healthcare centres. After this retest, some children were referred to ophthalmologists. The referral criteria for visual acuity were <0.5 at 3 years and <0.63 at 4 or 5 years in at least one eye. RESULTS: Of those screened, 7116 (19.2%) children did not pass the home screening tests and 2058 (28.9%) out of the 7116 were referred. The results of the ophthalmological examination in eye clinics were only available for 894 children (43.4%) of those who were referred. The rest of the children did not visit ophthalmologists because they had been checked at an eye clinic, were currently under treatment, or for personal reasons. Refractive errors were found in 608 (1.6%) children. Astigmatism was associated in 78.2% of ametropes. Amblyopia was discovered in 149 (0.4%) children and refractive error was the major aetiology with a predominant rate (82.5%). Manifest strabismus was detected in 52 children. The positive predictive value of vision screening for any ophthalmological disorder was 0.77, and 0.49 for significant disorders requiring treatment. CONCLUSIONS: This preschool vision screening model was highly accessible to the children and their parents, easy to administer, and effective to detect a variety of ocular disorders. However, the participation rate of the referred children in the examinations by ophthalmologists was quite low. The performance and efficiency of this screening programme need to be optimised with further revision.

Amblyopia↗

PubMed1999

The cornea swells in the posterior direction under hydrogel contact lenses.

Two mathematical models were developed to describe the topographical corneal swelling response to hydrogel contact lenses and the effect of these changes on refractive error. In one, corneal thickness changes resulted in deformation of the anterior corneal surface. In the other, the posterior surface only was deformed. Refractive error, corneal thickness and corneal shape were monitored in a sample of adapted contact lens wearers with one eye patched for 4 h while wearing a soft contact lens. The experimental data were most consistent with the model in which the posterior surface only was deformed.

Contact Lenses, Hydrophilic↗

PubMed2004

[Evaluation of eye total aberration in patients with keratoconus].

PURPOSE: Evaluation of total eye aberration in patients with I, II, III degree of keratoconus according to Amsler scale, and results compared with normal group patients, having only refractive error. MATERIAL AND METHOD: The analyzed group of patients consisted of 43 patients (55 eyes), who underwent examinations: visual acuity, subjective and objective refractive error, cornea keratometric power, pupil diameter and total eye aberration performed by System WASCA (Asclepion-Meditec). Our patients were divided in to two groups: group I--16 patients with keratoconus (25 eyes), group II--27 control patients (30 eyes). RESULTS: Comparison of all analyzed parameters in both groups were statistical significant. In eyes with keratoconus coma aberrations excel spherical aberrations.

Adolescent↗

PubMed2003

Double-pass measurement of retinal image quality in the chicken eye.

PURPOSE: The chicken, Gallus gallus domesticus, is used as an animal model to study the development of refractive error. Although vision is important in determining the eye's refractive state, relatively little is known about the retinal image quality of the chicken eye. An objective double-pass technique was used to measure the optical quality of the eyes of White Leghorn chickens. METHODS: Measurements were made on 21 eyes of six untreated birds and eight experimental birds that were members of a study of refractive development. Ages ranged from 3 to 6 weeks, and refractions ranged from -1.29 to +0.58 D in the untreated eyes and -4.58 to +10.17 D in the experimental eyes. The measurements were made under general anesthesia combined with either cycloplegia or ciliary nerve section. Proper optical alignment of the eye was achieved with the aid of a TV monitor, CCD camera, and an infrared source. A 543-nm laser point source was focused on the retina, and the double-pass aerial image was collected by a high-resolution CCD camera. Refractive errors were corrected with trial lenses, using a bracketing method to optimize the retinal images. Both the full width at half-maximum of the double-pass aerial image and the single-pass modulation transfer function were used as objective estimates of the optical quality. RESULTS: The mean full width at half-maximum value in eyes of the untreated birds was 1.60 min arc for a 4.50-mm mean pupil diameter. Optical quality tended to be worse in the experimental myopic eyes. CONCLUSIONS: The optical quality of the chicken eye measured under monochromatic conditions meets or may even exceed the neural limits of spatial acuity based on anatomical estimates of ganglion cell spacing. The data also suggest that optical quality is worse in myopic eyes, which is consistent with studies of human eyes.

Animals↗

PubMed2004

Awareness and knowledge of common eye diseases among the academic staff (non-medical faculties) of University of Malaya.

A cross sectional study was conducted to assess the level of awareness and knowledge of common eye diseases (cataract, glaucoma, diabetic retinopathy and refractive errors) among 473 academic staff (non-medical faculties) of University Malaya. The awareness of cataract was in 88.2%, diabetic retinopathy in 83.5%, refractive errors in 75.3% and glaucoma in 71.5% of the study population. The knowledge about all the above common eye diseases was moderate, except presbyopia which was poor. Multivariate analysis revealed that females, older people, and those having family history of eye diseases were significantly more aware and more knowledgeable about the eye diseases. Health education about eye diseases would be beneficial to seek early treatment and prevent visual impairment in the society.

Adult↗

PubMed1990

Threshold perimetry in tilted disc syndrome.

Twelve consecutive patients (17 eyes) with tilted disc syndrome underwent quantified visual field examination with the G1 Octopus program (Interzeag AG, Schlieren, Switzerland). Visual fields were abnormal in all cases. Although field loss was more pronounced in the superotemporal quadrant (P less than .001), it also involved the other three quadrants, thus demonstrating that optic nerve hypoplasia in tilted disc syndrome is apparently not entirely sectorial. Linear regression analysis showed that an increase in mean defect correlated with increase in myopic refractive error (P less than .05). However, the increase in myopic refractive error was found to be related to a decrease in corrected loss variance (P less than .05), indicating that in tilted discs with higher myopia, field loss is more homogeneous. With this series of patients, short-term fluctuation was within normal ranges in all visual fields, showing that this may be an additional clue for differential diagnosis from acquired disorders.

Adult↗

PubMedDate not supplied

Prevalence of eye disorders among the elderly in Los Angeles.

A series of 431 vision screening records of seniors 55 years of age and older were analysed. Patients were examined by the UCLA Mobile Eye Clinic at two senior centers in the Los Angeles area, between the years 1982 and 1990. Sixty-eight percent of patients were females and 32% were males. The mean (+/-S.D.) age was 69 (+/-7.5) years. Common diagnoses were refractive errors (65.2%) and impaired visual acuity (37.0%). The prevalences of refractive errors were: hyperopia, 24.8%; myopia, 10.4%; presbyopia, 54.1%; and astigmatism, 31.8%. In most patients (94.0%), impaired visual acuity was corrected by spectacles. The prevalence of cataract was 29.5% and age-specific prevalences of cataract increased with age. The prevalences of other eye disorders were as follows: glaucoma, 6.3%; diabetic retinopathy, 1.2%; and macular degeneration, 5.1%. This study highlights the degree of ophthalmic disorders identified by vision screenings in the elderly population in senior centers; our results are consistent with previously reported studies of eye diseases in the elderly.

Journal Article↗

PubMed2006

The AS biometry technique--a novel technique to aid accurate intraocular lens power calculation after corneal laser refractive surgery.

Intraocular lens power (IOL) calculation for cataract surgery has been shown to be inaccurate after photorefractive keratectomy (PRK), laser-assisted subepithelial keratectomy (LASEK) and laser in situ keratomileusis (LASIK). Many techniques exist to calculate corneal power with varying results and require the clinician to be aware of the pitfalls of IOL power calculation in post-refractive eyes. The AS biometry method proposed here is a simple method which does not rely on the calculation of corneal power. This new method is compared to the current gold standard the clinical history method (CHM). Twenty-nine eyes of 15 patients had routine biometry prior to LASIK, LASEK or PRK. The range of pre-operative spherical equivalent refractive error was -5.37 to +4.00 diopters. The post-operative refraction was measured at 3-6 months. The IOL power calculation was calculated using the AS biometry method and the CHM. The two methods were compared using the Student's paired t-test and the Bland Altman technique. There was no statistical difference between the AS biometry method and the CHM. The paired Student's t-test comparing the AS biometry method and the CHM showed no statistical difference, t=0.33 with a p-value of 0.75, at a 95% confidence interval. The authors conclude that the AS biometry technique is as accurate as the CHM. The former is a simpler method which avoids many of the pitfalls and confounding factors involved in IOL power calculation following corneal excimer laser surgery. However, like the CHM it requires measurements prior to laser surgery.

Adult↗

PubMedDate not supplied

Kinetics of foveal cone photopigment in myopia without chorioretinal degeneration.

PURPOSE: To study the early changes in the outer retina of myopic eyes, we performed fundus reflection foveal cone densitometry in 45 subjects with normal visual acuity and no chorioretinal degeneration (ages: 18-47 years, refraction; +2.00-(-14.50) diopters). METHODS: After full bleaching, the density of the photopigment was measured for 7 minutes by using a test spot, 562 nm in wavelength and 1 degrees in diameter, focused on the fovea. We calculated the density difference (DD) and the time constant (TC) of photopigment regeneration. RESULTS: Although we found no correlation between the DD and the refractive error, there was a significant increase in TC as the refractive error increased (r = 0.50, P < 0.01). CONCLUSIONS: These findings indicated that the kinetics of cone pigments become abnormal preceding the loss of cone cells or chorioretinal degeneration in high myopia.

Adolescent↗

PubMed1996

Distribution of astigmatism in the adult population.

We have quantified statistically the astigmatic frequency distribution. Vectorial analysis was used, as it enables formal multivariate statistical techniques to be applied to astigmatic data, allowing the simultaneous inclusion of both modulus and axis in the analytical procedure. These methods were applied to population data for each of total, corneal, and residual astigmatism from a sample of 198 adults. Right and left eyes were analyzed separately. All the distributions were found to depart significantly from a normal distribution. All the distributions were significantly leptokurtic (p < 0.005), and the distributions of total right eye, corneal right eye, and residual left eye astigmatism were also found to be significantly skewed (p < 0.05). Significant mild correlations were found between total and corneal astigmatism (p < 0.05). These findings add to the database of knowledge of astigmatic refractive error and may be of interest to those investigating refractive-error development.

Adolescent↗

PubMedDate not supplied

Refractive results of radial keratotomy after 10 years.

BACKGROUND: We analyzed retrospectively the refractive and visual results of a cohort of patients who underwent radial keratotomy for myopia 10 years ago. METHODS: Radial keratotomies using centripetal incisions were performed by the same surgeon in 1986 and 1987 to correct myopia of -0.75 to -10.00 diopters (D). Refractive and visual results were evaluated at 1 month and on average 10 years after surgery. RESULTS: Thirty-nine patients (71 eyes) underwent radial keratotomy. Mean spherical equivalent refraction before surgery was -3.90 D and after surgery was -0.50 D at 1 month and +0.13 D at 10 years after surgery. At last examination, 41 eyes (43.7%) had a spherical equivalent refractive error within +/- 1.00 D of emmetropia (24 eyes [34%] +/- 0.50 D) and 32.4% of eyes were overcorrected by more than 1.00 D. Between 1 month and 10 years after surgery, a hyperopic shift greater than 1.00 D occurred in 34.1% of eves with a single procedure. Ten years after surgery, 59 eyes (83%) had uncorrected distance visual acuity of 20/40 or better (22 eyes [31%] with uncorrected visual acuity of 20/20 or better). CONCLUSION: This retrospective evaluation confirms that radial keratotomy is an effective procedure to correct myopic error, but the hyperopic shift produces an unstable, less predictable refraction in one-third of eyes at 10 years.

Adult↗

PubMed1986

Blindness in Saudi Arabia.

The prevalence and etiology of visual loss and of eye diseases were determined in the Kingdom of Saudi Arabia. The sample was a stratified geographic cluster sample of 14,577 persons representing the settled population of Saudi Arabia. A nonstatistical sample of 2,233 bedouins was also examined. The survey revealed that 1.5% of the population are blind and another 7.8% are visually impaired according to the World Health Organization definition. The most common causes of blindness include cataract, trachoma, nontrachomatous corneal scars, refractive errors, congenital anomalies, failed medical or surgical treatment, and glaucoma. Refractive errors, amblyopia, and trauma are also important causes of less severe, and often unilateral, lost vision. About 7% of all Saudi Arabians, and 42% of those older than 40 years, have a cataract or its sequelae. Over 3.5% of the population have corneal scars, about half of which are caused by trachoma.

Adolescent↗

PubMed1988

IOL prediction: an evaluation of preoperatively determined intraocular lens power accuracy.

A retrospective survey of 612 eyes that had undergone cataract extraction and IOL implantation was undertaken to evaluate the accuracy of ultrasound biometry combined with keratometry using the SRK regression formula, for the preoperative prediction of intraocular lens powers. A mean error of +0.35 dioptre sphere (DS) (SD +/- 0.98) was found for the series overall, with a significant (P less than 0.005) difference between the distribution of postoperative refractive errors using the S.R.K. formula for IOL prediction and the use of a standard lens of 19.5 DS. The consistency of results was tested for those patients with greater or less than normal axial length. Linear regression analysis showed no correlation between axial length and postoperative refractive error and therefore does not support the adjustment of predicted IOL powers by a factor based on axial length. Statistically significant differences were found between surgeons' results, supporting the practice of A-constant modification for individual surgeons.

Cornea↗

PubMed1983

The use of isotropic photorefraction for vision screening in infants.

Isotropic photorefraction is a technique which makes possible the rapid, economic, large scale screening of infants and young children for refractive errors. The relative size of blur circles reflected from the fundus in 3 flash photographs with different camera settings allows the size and direction of refractive errors to be estimated. The method has been validated against retinoscopic measures on a large group of infants. Findings of a high incidence of astigmatism in the first year are confirmed. Detection of hypermetropia in early infancy by this screening procedure may allow preventive treatment for accommodative strabismus.

Astigmatism↗

PubMed1976

Effects of non-contact tonometry on refraction.

The spherical component of refractive error was measured subjectively before and after noncontact tonometry in 19 eyes and also on the fellow (control) eyes without tonometry. No significant change in this measure of refractive error was found after tonometry. The tested group could not be distinguished from the control group.

Adult↗

PubMed1993

The relationship between ciliary muscle fatigue and the type of artificial light used to illuminate the area of visual work.

The relationship between the degree of eye fatigue resulting from visual work and type of light source used to illuminate the field of work was assessed. The tests were performed using artificial light sources: fluorescent lamps, incandescent lamps, high pressure mercury (vapour) and high pressure sodium (vapour) lamps. The assessment was performed on two groups of 10 women each, of which one included women without, and the other with, refraction errors. On the basis of changes of nearer vision point and dispersing lens tolerance, it was found that sodium light produced the highest visual fatigue in the test women, especially in those with refraction errors.

Adult↗

PubMed1996

Penetrating keratoplasty with donor and recipient corneas of the same diameter.

BACKGROUND AND OBJECTIVE: A retrospective study was conducted to investigate the effect of penetrating keratoplasty (PK) with donor and recipient corneas of equal diameter on astigmatism, corneal curvature, and spherical equivalent. PATIENTS AND METHODS: A total of 89 eyes of 86 consecutive patients who underwent PK with donor and recipient corneas of equal diameter were studied. The surgical techniques were performed using the Hanna suction punch block (endothelial cut) with the trephine system, and a single running 16-bite 10-0 nylon suture. Sixteen eyes underwent a triple procedure (PK, extracapsular cataract extraction, and intraocular lens [IOL] insertion) and 14 eyes underwent PK with sulcus fixation of a posterior chamber IOL. Follow-up ranged from 12 to 30 months (mean +/- SD 17.5 +/- 4.7). The sutures were removed at approximately 12 months postoperatively. RESULTS: The postoperative astigmatism ranged from 0.4 to 10.8 D (mean +/- SD 4.5 +/- 2.8), as evaluated by a computer-assisted videokeratograph topography unit. Twenty-seven eyes (30.3%) achieved a refractive error (spherical equivalent) within +/- 1.5 D of emmetropia. The mean postoperative refractive error (spherical equivalent) was -0.1 +/- 3.5 D (range -6.75 to + 7.25). No wound dehiscences or glaucoma was noted during the follow-up. CONCLUSION: The Hanna suction system creates a sharp, deep, and perpendicular cut on both button cornea and host cornea, making it possible to use donor and recipient corneas of the same diameter in PK with good clinical and refractive results, particularly for myopic (keratoconus) patients.

Astigmatism↗

PubMedDate not supplied

Resource management of cataract patients: can visual rehabilitation be achieved in three visits?

PURPOSE: To assess the feasibility and acceptability of reduced postoperative follow-up after phacoemulsification using a scleral tunnel technique. SETTING: Cataract service of a large free-standing eye hospital in a capital city. METHODS: In this pilot study, patients with age-related cataract requiring surgery were prospectively recruited to a standardized management protocol, the three-episode model, with assessment by an independent observer. Main outcome measures were number of postoperative visits, patient satisfaction, and refractive error at 2 and 6 weeks postoperatively. RESULTS: Almost 90% of patients could be managed within this model of care. Patient satisfaction was high; no patient requested further hospital visits. Mean change in refractive error between 2 and 6 weeks was 0.34 diopters (D), with a modal value of 0 D. Patients were able to obtain spectacles 2 weeks postoperatively because little change in refraction occurs over the next month. CONCLUSION: The three-episode model for the management of patients with cataract could result in significant financial savings. Such savings could be used to treat patients with cataract who otherwise would not have treatment or would have their surgery delayed.

Episode of Care↗