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PubMed2001

Myopia and night lighting in children in Singapore.

AIM: To examine the role of night time lighting and myopia in children in Singapore METHODS: A cross sectional study was conducted on 1001 children in two Singapore schools. Cycloplegic refraction and A-scan biometry measurements were made in both eyes. A detailed questionnaire was completed by the parents to obtain information on night time lighting, near work activity, educational and demographic factors. RESULTS: There was no difference in myopia prevalence rates in children exposed to night time light (33.1%) compared with children who slept in the dark (31.4%) before age 2. In addition, vitreous chamber depth was not related to night light (p = 0.58) before age 2. These results remained even after controlling for near work. CONCLUSION: Myopia is not associated with night light in Asian populations.

Anterior Chamber↗
PubMed2003

Utility values and myopia in teenage school students.

AIM: To ascertain the utility values of myopic teenage students in Singapore. METHODS: Children (n=699) aged 15-18 years with myopia (spherical equivalent (SE) at least -0.5 dioptres (D)) in two high schools in Singapore were recruited. Information on time trade-off (years of life willing to sacrifice for treatment of myopia) and standard gamble for blindness (risk of blindness from therapy willing to sacrifice for treatment of myopia) utility values, demographic, and socioeconomic status data were obtained. RESULTS: The time trade-off and standard gamble for blindness utility values were 0.93 (95% confidence interval (CI) 0.93 to 0.94) and 0.85 (95% CI 0.84 to 0.86), respectively. Children with presenting better eye logMAR visual acuity >0.3 had lower time trade-off utility values (mean 0.92 versus mean 0.94), after adjusting for race and sex. There were dose-response relations between standard gamble for blindness values and total family income, as well as both utility values and educational stream (all p values for trend <0.01), after controlling for the same factors. CONCLUSION: The utility values in myopic students were higher for teenagers with better presenting visual acuity, children who wore spectacles or contact lenses, higher total family income, more "academic" schooling stream, and who were non-Muslims.

Adolescent↗
PubMed1999

Transient acute myopia induced by antilymphocyte globulins.

Acute onset of transient myopia may be induced by several drugs, different mechanisms having been described. We report the occurrence of such an event after intravenous administration of equine antilymphocyte globulins in a patient treated for aplastic anemia. Clinical ocular examination revealed no other abnormality, and ultrasonography disclosed no swelling of the ciliary body. The drug-induced myopia resolved completely after instillation of topical cyclopentolate, suggesting that its mechanism was the occurrence of a ciliary spasm. Acute myopia is a rare event and, to the authors' knowledge, this represents the first case described as being induced by antilymphocyte globulins.

Acute Disease↗
PubMedDate not supplied

Effect of a nitric oxide synthase inhibitor on lens-induced myopia.

PURPOSE: It has still not been determined whether the retinal mechanism causing form-deprivation myopia (FDM) is different from that causing lens-induced myopia (LIM). We previously reported that FDM was blocked by an intravitreal injection of the nitric oxide (NO) synthase inhibitor, N-nitro-L-arginine methyl ester (L-NAME). In this study, we investigated the effect of L-NAME on LIM in chicks. METHOD: The left eyes of 6-day-old chicks were injected with 30 microl of nontoxic concentrations of L-NAME (< or = 360 mM) or saline. The right eyes were injected with 30 microl of saline. A -16 dpt lens was placed in front of the left eye for 6 days. Another group of 6 chicks were injected with 180 mM L-NAME (left eye) and with saline (right eye) before placing -16 dpt lenses in front of both eyes. After removing the lens, the refraction and the axial length were measured. The effect of L-NAME (180 mM) on the retina of a separate group of chicks was examined by electroretinography 60 min after an intravitreal injection in non-LIM-treated eyes. RESULTS: The eyes of chicks that were injected with 180 or 360 mM L-NAME were less myopic and had significantly shorter axial lengths than control eyes. A significant decrease of the On response and an increase of the Off response were observed. CONCLUSION: The injection of L-NAME into developing chick eyes that were then covered with a -16 dpt lens resulted in a modifications of retinal function and an inhibition of the development of myopia. These results, combined with the earlier findings, suggest that NO modulates a common retinal pathway that leads to both LIM and FDM.

Animals↗
PubMedDate not supplied

Differences between regressive eyes and non-regressive eyes after LASIK for myopia in the time course of corneal changes assessed with the Orbscan.

The aim of this study was to compare regressive eyes with non-regressive eyes after laser in situ keratomileusis (LASIK) for myopia with regard to the time course of biomechanical changes of the cornea and to evaluate the possible roles of these changes in refractive regression following surgery. 15 eyes of 9 patients with refractive regression and 15 eyes of 11 patients with no refractive regression after LASIK for myopia were enrolled in this study. The time courses of central corneal thickness (CCT) and anterior/posterior corneal curvature radiuses (CCR) were measured with Orbscan slit scanning before and 1 week, 1 month and 3 months after LASIK for myopia. The regressive and non-regressive eyes had similar time courses of CCT before and after LASIK, whereas the 2 groups differed in the time courses of corneal shifting movements. In the regression group, the posterior CCR after LASIK was relatively stable (all p > 0.05). By contrast, in the non-regression group, the postoperative posterior CCR at week 1 had a significantly steeper curvature than that at month 3 (p = 0.000). The anterior CCR in the regression group at week 1 had a significantly flatter curvature than that at month 3 (p = 0.002) postoperatively. In contrast, there was no significant change of anterior CCR postoperatively (all p > 0.05) in the non-regression group. Taken together, these data suggest that refractive regression after LASIK might be mainly induced by corneal protrusion rather than central corneal thickening.

Adult↗
PubMed1997

Severe myopia as a risk factor for progressive visual field loss in primary open-angle glaucoma.

The optic nerve head in severely myopic eyes may be particularly vulnerable to glaucomatous damage. To study this hypothesis, we examined 122 primary open-angle glaucoma eyes with fair to good control of the intraocular pressure and a sign of baseline optic nerve damage. Then, parameters for the progression of the visual field defects were evaluated by multivariate analysis. A high mean intraocular pressure (p = 0.007) and a large refractive error (p = 0.023) were significant risk factors for subsequent visual field loss. A high baseline cup-to-disk ratio (p = 0.100) was a marginal risk factor. Nonsignificant parameters included patient age (p = 0.692), the use of beta-adrenergic antagonists (p = 0.384), gender (p = 0.831) and left versus right side (p = 0.977). When the refractive error was used to subclassify patients into severely myopic (< or = -4 dpt), mildly myopic (-0.25 to -4 dpt), or emmetropic and hyperopic (> or = 0 dpt), only severe myopia was a significant risk factor for progressive visual field loss. Severe myopia, but not mild myopia, is a significant risk factor for subsequent visual field loss in patients with primary open-angle glaucoma.

Adolescent↗
PubMed2003

GABA, experimental myopia, and ocular growth in chick.

PURPOSE: To learn whether gamma-aminobutyric acid (GABA) participates in retinal mechanisms that influence refractive development. METHODS: White leghorn chicks, some of which wore a unilateral goggle to induce myopia, received daily intravitreal injections of agonists or antagonists to the major GABA receptor subtypes. Eyes were studied with refractometry, ultrasound, and calipers. Retinas of other chicks wearing unilateral goggles were assayed for GABA content. RESULTS: Antagonists to GABA(A) or GABA(A0r) (formerly known as GABA(C)) receptors inhibited form-deprivation myopia. GABA(A) antagonists showed greater inhibition of myopic growth in the equatorial than the axial dimension. A GABA(A0r) antagonist displayed parallel inhibition in the axial and equatorial dimensions. A GABA(A0r) agonist but not GABA(A) agonists altered the myopic refraction of goggled eyes. GABA(B) receptor antagonists, more so than an agonist, also slowed development of myopia, inhibiting axial growth more effectively than equatorial expansion of goggled eyes. When administered to nongoggled eyes, GABA(A) or GABA(A0r) agonists or antagonists also altered eye growth, chiefly stimulating it. Only a GABA(A) agonist induced a myopic refraction. Several of these agents stimulated eye growth in the axial, but not the equatorial, dimension. Retinal GABA content was slightly reduced in goggled eyes. CONCLUSIONS: GABA(A), GABA(A0r), and GABA(B) receptors modulate eye growth and refractive development. The anatomic effects of these drugs reinforce the notion that eye shape and not just eye size is regulated. A retinal site of action is consistent with the known ocular localizations of GABA and its receptors and with the altered retinal biochemistry in form-deprived eyes.

Animals↗
PubMed2007

Regional variations in the relationship between macular thickness measurements and myopia.

PURPOSE: To investigate the relationship between myopia and macular thickness, as measured by optical coherence tomography. METHODS: A total of 143 normal subjects comprising 80 eyes with high myopia (spherical equivalent [SE] < -6.0 D), 37 eyes with low to moderate myopia (SE between -6.0 and -0.5 D), and 26 nonmyopic eyes (SE > -0.5 D) were analyzed in this cross-sectional study. Total average, foveal, and inner and outer average macular thicknesses measured by the StratusOCT (Carl Zeiss Meditec Inc., Dublin, CA) were compared among the three diagnostic groups. Associations between macular thickness and refractive error/axial length were evaluated by linear regression analysis. RESULTS: The minimum foveal and average foveal (1-mm ring on the OCT retinal thickness map) thicknesses were significantly greater, and the outer ring macular (3-6-mm) thicknesses significantly lower in the high myopic eyes than in the low to moderate myopic and nonmyopic eyes. No significant difference was found in the inner ring (1-3-mm) macular thickness measurements among the groups. There was a positive correlation between the axial length and the average foveal thickness (r = 0.374, P < 0.001). Negative correlations were found between axial length and the average outer ring macular thickness (r= -0.471, P < 0.001) and total average macular thickness (r= -0.311, P < 0.001). CONCLUSIONS: Retinal thickness is related to refractive error/axial length in normal subjects with regional variations in correlation within the 6-mm macular region. Analysis of macular thickness in the evaluation of macular diseases and glaucoma should be interpreted only in the context of refractive errors and the location of measurement.

Adult↗
PubMedDate not supplied

Refractive lens exchange for correction of high myopia.

PURPOSE: To evaluate the efficiency and safety of refractive lens exchange for the correction of high myopia. METHODS: We made a prospective study of the results of refractive lens exchange in 72 eyes that had undergone this surgical procedure between January 1996 and January 2001. Lens extraction by phacoemulsification was done by one surgeon on 34 patients. Follow-up was five months to five years (mean 48 months). The postoperative refractive target was emmetropia or a low degree of myopia. We compared pre- and postoperative uncorrected visual acuity, and preoperative best-corrected visual acuity with postoperative uncorrected visual acuity. Intra- and postoperative complications were recorded. RESULTS: In 72.2% of the eyes best-corrected visual acuity (BCVA) was > or = 0.5 before surgery. Four years after refractive lens exchange, uncorrected visual acuity (UCVA) was > or = 0.5 in 58.3% of eyes, and the proportion of eyes with BCVA > or = 0.5 increased to 83.3%. The sphere was fully corrected in 70.8% of cases, remained within 1.0 D of emmetropia in 87.5% and within 2.0 D of emmetropia in 95.8%. Posterior capsule opacification developed in 22 eyes (30.5%) and was treated with neodymium:YAG (Nd:YAG) laser capsulotomy. Cystoid macular edema with retinal detachment occurred in one eye. No wound leakage or eye infections were observed during five years' follow-up. CONCLUSIONS: Refractive lens exchange seems to be an effective alternative for the correction of high myopia, helping people over 40 years of age regain their distant vision.

Adult↗
PubMedDate not supplied

Small incision clear lens extraction for correction of high myopia.

PURPOSE: To evaluate the effectiveness, predictability, and safety of clear lens extraction in the correction of high myopia. SETTING: Kartal Education and Research Hospital, Istanbul, Turkey. METHODS: This retrospective study comprised 56 eyes of 30 patients who had clear lens extraction to correct myopia of 12.00 diopters (D) or more. Small incision clear lens extraction using an anterior chamber maintainer was performed and low-power posterior chamber intraocular lens (IOL) was implanted. The mean postoperative follow-up was 40.2 +/- 11.9 months. RESULTS: Uncorrected visual acuity improved in 94.6% of eyes. Best-corrected visual acuity (BCVA) improved in 37 eyes (66%); 27 (48.2%) gained two or more lines. The percentage of eyes achieving a BCVA of 20/40 or better increased from 26.7% preoperatively to 58.9% postoperatively. Of the eyes, 38 (67.8%) were within +/- 1.00 D of targeted refractive error and 52 (92.8%) were within +/- 2.00 D. Posterior capsule tear with vitreous loss occurred in one eye (1.7%). During the follow-up, retinal detachment (RD) occurred in 2 eyes (3.5%). CONCLUSIONS: Clear lens extraction and IOL implantation was effective and had an acceptable predictability and a low morbidity in correcting high myopia. Regular retinal examination is necessary to prevent postoperative RD.

Adult↗
PubMedDate not supplied

High myopia and congenital myopathy with partial pachygyria in cutis laxa syndrome.

PURPOSE: Several types of inborn errors of the O-glycan biosynthesis are known, leading to clinically very distinct phenotypes. Children with O-mannosyl glycan biosynthesis defects commonly present as a severe form of congenital muscular dystrophy with decreased alpha-dystroglycan staining, congenital eye anomalies, and brain migration defects. Alpha-dystroglycan is an O-mannosylated glycoprotein with additional mucin type O-glycans. METHODS: Based on overlapping clinical features with O-mannosyl glycan defects, especially with muscle-eye-brain disease, the authors performed a muscle biopsy in a child with severe congenital hypotonia, high myopia, partial pachygyria, mental retardation, cutis laxa, and an inborn error affecting the biosynthesis of both mucin type O-glycans and N-linked glycans. RESULTS: The histology showed no signs of muscle dystrophy, but a mild myopathy with slight increase in the muscle fiber diameter variability and type I fiber predominance. No significant decrease in the alpha-dystroglycan staining was detected; therefore, in spite of the phenotypic similarities the authors could not confirm the role of abnormal dystroglycan in the etiology of the muscle weakness and the developmental anomalies. CONCLUSIONS: High myopia, muscle weakness, and cortical neuronal migration abnormalities are common in disorders of O-mannosylation and also observed in the authors' patient. However, compared to the severe generalized defect observed in mannosyl glycan defects, in this child the cerebral white matter and cerebellum were spared, and no muscle dystrophy could be confirmed. This is the first description of high myopia in cutis laxa syndrome in combination with congenital disorders of glycosylation.

Abnormalities, Multiple↗
PubMedDate not supplied

Relationship between retinal lesions and axial length, age and sex in high myopia.

We analysed the relationship between central and peripheral retinal lesions and axial length (AL), patient's age and sex with myopia greater than 6 diopters. A total of 212 eyes of 109 patients with high myopia underwent detailed funduscopy and A-scan ultrasonography. AL was measured, and central and peripheral retinal lesions were noted. Results were analysed using Student's t-test. Sixty-one patients (118 eyes) were female and 48 (94 eyes) male. Mean age was 31.00 +/- 13.67 years, and mean AL was 28.31 +/- 2.02 mm. Chorioretinal atrophy, Fuchs' spot, posterior staphyloma and posterior vitreous detachment increased significantly with AL and age. Fuchs' spot was more common in females. White-without-pressure (WWP) was inversely correlated with AL and age, and was more common in males. The high frequency of WWP in younger patients and moderate AL suggests that these lesions result from vitreoretinal tractions. Lattice degeneration was also a frequent finding in high myopia, and tended to increase with AL and age, though without reaching statistical significance.

Adolescent↗
PubMedDate not supplied

Epikeratophakia: the surgical correction of myopia. I. Lathing of corneal tissue.

In order to develop a surgical technique as an alternate method for the treatment of myopia, we have adapted the epikeratophakia corneal graft procedure. The procedure is not burdened with some of the side effects associated with radial keratotomy and a wide range of predictable correction can be obtained. Preliminary trails in a non-human primate model have indicated that myopia up to -27 diopters can be corrected accurately with these grafts. In this paper we present the mathematical model for the lathing of epikeratophakia grafts for the correlation of myopia, and preliminary results in the non-human primate model.

Animals↗
PubMed1990

Scleral changes in chicks with form-deprivation myopia.

The sclera in myopic regions of chick eyes was studied histologically and compared to the sclera in corresponding regions of normal fellow eyes. Chicks had been monocularly deprived of form vision in the nasal half of the retina from hatching. The fellow control eye and the temporal retina of the deprived eye had normal vision. With this treatment, the resulting form-deprivation myopia and eye enlargement are restricted to the retinal region that had been form deprived. We found that the cartilaginous sclera in the myopic nasal region exhibited several differences from that in the corresponding non-myopic region: it was thicker, its cell density was lower, and the number of chondrocytes and binucleate cells was higher. In contrast, the fibrous sclera was thinner. These changes suggest that form-deprivation myopia causes an increased production of extracellular matrix and an increased level of mitotic activity in the cartilaginous sclera. As expected, the non-myopic temporal regions of experimental and control eyes did not differ in any of these parameters. The findings of the present study suggest that the eye enlargement accompanying form-deprivation myopia is not the consequence of scleral stretching but of abnormal growth.

Animals↗
PubMed2000

Long-term results of laser in situ keratomileusis for high myopia.

The objective of this study was to evaluate the results of laser in situ keratomileusis (LASIK) for high myopia after a follow-up of two years. A total of 42 eyes from 33 patients with high myopia (range: -9.00 D to -25.50 D) were studied. LASIK was performed using an automated microkeratome (Steinway, USA) and OmniMed II excimer laser with the standard MKM program (Summit Technology, Inc., Waltham, MA) in all patients. The patients were followed up at one, three, six, 12 and 24 months. During follow-up manifest refraction and best corrected and uncorrected visual acuity were measured. Any complications were also analyzed. The two-year follow-up results were as follows. The mean postoperative manifest spherical equivalents (MSE) were -0.51 D at one month, -1.09 D at three months, -1.78 D at six months, -2.17 D at 12 months and -2.61 D at 24 months. Myopic regression continued during the two-year follow-up (p < 0.05). The accuracy of the intended postoperative correction within +/- 2.00 D was 73.8% at one month, 69.1% at three months, 52.4% at six months, 52.4% at 12 months, and 45.2% at 24 months. The best corrected visual acuity (BCVA) was unchanged or increased in 35 eyes (83.3%). Only three eyes (7.2%) lost two or more lines of BCVA. This was due to irregular astigmatism in one eye, macular degeneration in one eye, and rhegmatogenous retinal detachment in one eye. In this study, LASIK was effective and safe in the correction of high myopia, however continuous myopic regression was seen over the two-year follow-up. Refining the nomogram to adjust for progressive myopic regression will be necessary in order to obtain better results.

Adult↗
PubMedDate not supplied

Excimer laser in situ keratomileusis for myopia.

Excimer laser in situ keratomileusis was done in 97 eyes of 59 patients to correct moderate and high myopia. Mean follow-up was 150 days. Mean preoperative myopia was -10.75 diopters (D). Mean reduction in myopia was -11.281 D (106.98%) at 1 month and -10.37D (98.417%) at 3 months. At 1-month, 41 eyes (42.27%) had a refraction within -1.00 D and 70 teeyes (72.16%) had a refraction within -2.00 D. At 3 months, 41 eyes (46.59% of 88 eyes) had a refraction within -1.00 D and 66 eyes (75% of 88 eyes) had a refraction within -2.00 D. Mean preoperative keratometric power was 44.00 D; mean postoperative keratometric power was 36.39 D. The keratometric change in power was 7.61 D. Preoperatively, 73 eyes (75%) had a spectacle corrected visual acuity of 20/40 or better; postoperatively, 64 eyes (65.63%) at 1 month and 75 eyes (77.01%) at 3 months reached 20/40 or better. The uncorrected visual acuity was 20/40 or better in 33 eyes (33.72%) at 1 month and in 49 eyes (49.96%) at 3 months. Mean ablation zone diameter was 4.92 mm. Astigmatism was treated separately in 10 eyes. Complications included optical zone decentration (3 eyes with more than 1 mm, epithelial implantation (1 eye), incomplete resection of the disc (2 eyes), severe hypotension, and irregular astigmatism (1 eye).

Adolescent↗
PubMedDate not supplied

Photorefractive keratectomy for undercorrected myopia after radial keratotomy: two-year follow up.

We evaluated the clinical results of excimer laser photorefractive keratectomy (PRK) on 18 myopic eyes of 13 patients with residual myopia after radial keratotomy. Follow up was 24 months or more and the time interval between radial keratotomy and PRK ranged from 12 to 94 months. Patients were divided into two groups for analysis based on their preoperative myopia: group 1 (-6.00 diopters (D) or less), group 2 (more than -6.00 D). Uncorrected visual acuity at 2 years follow up was 20/40 or better in 86% (group 1) and 50% (group 2). Mean manifest refractive change was from -3.55 D to -0.91 D in group 1 and from -7.44 D to -2.50 D in group 2. Predictability within 1.00 D between attempted and achieved correction was 71.4% (group 1) and 80% (group 2). Most complications were transient except decreased spectacle corrected visual acuity in one eye--a complication also reported by others. Glare (61%) and decreased vision at night (50%) were the most troublesome subjective symptoms. These results show that previous radial keratotomy may not influence the myopic correction of PRK. Planned two-stage myopic correction (PRK after radial keratotomy) in high myopia can be considered a useful technique.

Adult↗
PubMedDate not supplied

Photorefractive keratectomy for myopia of 6 to 12 diopters.

To conduct a prospective, nonrandomized clinical trial to assess the efficacy, stability and safety of the use of excimer laser photorefractive keratectomy (PRK) to correct myopia of greater than -6.00 diopters (D) in Singapore. Two hundred thirty-three eyes of 176 patients with a mean preoperative spherical equivalent refraction of -8.70 +/- 2.3 D (range, -5.75 D to -18.13 D) underwent PRK with a 193nm ArF excimer laser (ExciMed, Summit) for myopic corrections of between -6.20 D and -11.90 D. The first 66 of 233 eyes that reached at least 1 year of postoperative follow up are reported. One year postoperatively, the mean manifest spherical equivalent refraction was -1.50 D +/- 1.90 D (range -6.25 D to +3.25 D); 34% of eyes were within +/- 1.00 D of attempted correction; uncorrected visual acuity was 20/40 or better in 75% of eyes. No eyes lost two or more Snellen lines of spectacle corrected visual acuity. Central corneal haze was mild in 20% of eyes and moderate in 3% of eyes. Five eyes developed ocular hypertension that subsequently resolved with treatment. Excimer laser PRK is reasonably effective and safe in the treatment of -6.00 D to -12.00 D of myopia. However, it is less accurate than PRK in eyes with low to moderate myopia and is more likely to result in significant corneal haze.

Adult↗