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At least 613 records · Page 34Linked to original sources
PubMed2006

Darkness causes myopia in visually experienced tree shrews.

PURPOSE: To examine the effect of a period of continuous darkness on the refractive state and vitreous chamber depth of normal light-reared juvenile tree shrew eyes, and to learn whether eyes that developed myopia in response to monocular minus-lens wear will recover in darkness. METHODS: Starting at 16 days of visual experience (VE), the refractive state of five dark-treatment tree shrews was measured daily to confirm that it was stable and nearly emmetropic. After corneal and ocular component dimension measures, the animals were placed into continuous darkness for 10 days. On removal of the animals from darkness, corneal and ocular component measures were repeated, and daily refractive measures were resumed. The refractive state of the dark-treatment group was compared with that of a normal-lighting group (n = 5) that received standard colony lighting throughout the measurement period. Five dark-recovery animals wore a monocular -5-D lens for 11 days to induce myopia before they were placed into continuous darkness for 10 days. RESULTS: The animals in the normal-lighting group completed the emmetropization process, stabilizing at approximately (mean +/- SEM) 0.7 +/- 0.3 D of hyperopia (noncycloplegic refraction, corrected for the small eye artifact) at 60 days of VE. Dark-treatment group eyes shifted toward myopia (mean +/- SEM, -4.3 +/- 0.5 D) in the dark. The vitreous chamber became elongated by 0.09 +/- 0.02 mm relative to normal eyes. Corneal power showed a small, near-normal decrease (1.4 +/- 0.3 D). Four of five myopic eyes in the dark-recovery group became more myopic (-2.2 +/- 0.9D) in darkness, and all the fellow control eyes shifted toward myopia (-2.8 +/- 0.5 D). CONCLUSIONS: Maintaining emmetropia is an active process. After eyes have achieved emmetropia or have compensated for a minus lens, continued visual guidance is necessary to maintain a match between the axial length and the focal plane or for recovery to occur. Absence of light is myopiagenic in tree shrews that have developed with normal diurnal lighting. This result contrasts with the apparent absence of a darkness effect in tree shrews reared in the dark from before normal eye opening.

Animals↗
PubMedDate not supplied

Myopia and level of education.

PURPOSE: To find out whether the development of myopia is related to the level of education. MATERIALS AND METHODS: From two big ophthalmic outpatient clinics in Jordan, 968 subjects (between the age of 24 and 45 years) were included in this study. A subject was considered myopic if at least one eye had a spherical equivalent refractive error of at least -0.75 diopter. The subjects were divided into two groups: the educated group was those who had finished at least 12 years of education and the non-educated which included those with maximum of six years of education. There were 468 men and 500 women. RESULTS: The frequency of myopia was higher in the educated group in both men and women. A significant relationship was found between the level of education and myopia in the whole study group (p<0.0001). CONCLUSIONS: This study had too few subjects to draw general conclusions, but within the study group there was a significant relationship between the level of education and the development of myopia.

Adult↗
PubMedDate not supplied

Myopia and stature: findings in a population of 106,926 males.

We conducted a nation-wide study of the relationship of myopia with height, weight and body-mass index in order to confirm observations that myopic persons are taller than non-myopes. From a review of the data of 106,926, consecutive male military recruits aged 17 to 19 years, we found that myopia is associated neither with higher stature nor with greater weight. Persons with severe myopia were slightly shorter (172.8 +/- 7.1 cm) and weighed less (62.6 +/- 11.0 kg) than those with mild myopia (173.3 +/- 6.9 cm and 63.8 +/- 10.5 kg respectively), while the non-myopes were taller (173.7 +/- 6.7 cm) and heavier (63.9 +/- 10.2 kg) than the myopes (p = 0.0001). The mean body-mass index was only slightly smaller among the myopes (21.1 +/- 3.1 kg/m2) than among the non-myopes (21.2 +/- 2.9 kg/m2, p = 0.0001).

Adolescent↗
PubMed1975

Instrument myopia.

The basis for instrument myopia, the tendency to accommodate inappropriately while viewing through an optical instrument, was investigated in three experiments. The first demonstrated that the distance of a peripheral surround, analogous to a field stop, influences accommodation but that the magnitude of the effect cannot account for instrument myopia. The second experiment re-examined the hypothesis that perceived distance can affect accommodation. The data indicate that perceived distance is unlikely to influence accommodation and does not provide an explanation of instrument myopia. The last experiment tested the hypothesis that instrument myopia is a manifestation of the return of accommodation to an intermediate state of rest or equilibrium in the absence of an adequate stimulus for accommodation. Implications of the intermediate-resting-state hypothesis are discussed.

Accommodation, Ocular↗
PubMed1986

Congenital cataract and evolutive myopia. Relationship with hypophyseal-adrenal cortical axis function.

To see whether or not reduced light input in children with congenital cataract produces degenerative myopia and whether it is associated with an impairment of the hypophyseal-adrenal cortical axis, the authors studied biometric values and circadian rhythm and cortisol reserve in nine children with monolateral and ten children with bilateral cataract. 38.75% of patients had: refractions less than 10D, increased antero-posterior diameter of the eyeball, varying degrees of myopic chorioretinitis, showing that the lack of light input induces degenerative myopia only in a group of patients who are probably genetically predisposed. The negative correlation between cortisol reserve and ocular lesions seems to reveal a precocious negative effect of the lack of light input on the development of the hypothalamic-hypophyseal-adrenal cortical axis. The alteration of the circadian cortisol rhythm and the reduction of the cortisol reserve found exclusively in children with monolateral cataract must be studied further to be explained. The slight increase in plasma cortisol levels earlier described in adults with acquired degenerative myopia was not found in children with congenital cataract. This difference could be due to: special endocrine characteristics in children with congenital cataract, endocrine differences between childhood and adulthood, differing influences of hormonal factors on myopia, or vice versa, in childhood and adulthood.

Adolescent↗
PubMed1995

Double-pass excimer laser photorefractive keratectomy: treatment in 62 eyes with high myopia.

To evaluate the efficacy and safety of Excimer Laser Photorefractive Keratectomy (PRK) on the correction of high myopia, we performed planned double-pass PRK procedure at the same session on 62 eyes of 55 patients with myopia ranging from -6.30D to -15.25D (mean, -9.94D). In the first pass, a myopic correction of -6.00D with a 4.5 millimeter ablation zone was performed, and immediately after, a second correction of remaining myopia with a 5.0 millimeter ablation zone was performed. Attempted correction ranged from -6.30D to -9.50D (mean, -8.70D). The eyes were divided into two groups which were -10.50D or less (group A), and higher than -10.50D (group B). All the eyes received topical corticosteroid therapy postoperatively. One year after double-pass PRK, uncorrected visual acuity in group A and B improved to 20/40 or better in 84.0%, and 73.3% of the eyes and to 20/30 or better in 75.0% and 33.3% of the eyes respectively. The mean refractive errors at 12 months after PRK were -0.3 +/- 1.6D in group A, and -1.5 +/- 2.1D in group B. The percent of achieved correction within +/- 1.0D were 70.8% in group A, and 46.7% in group B 12 months after surgery. The epithelium healed by three days and there were no corneal erosions. Corneal haze (Grade 2 or more) was seen in 9.0% in group A and 36.4% in group B at 12 months after PRK. A planned double-pass PRK is a promising approach to correct high myopia (up to -10.50D), but long-term follow up will be required.

Adult↗
PubMedDate not supplied

Automated lamellar keratomileusis in situ for myopia.

BACKGROUND: Keratomileusis in situ, particularly automated lamellar keratoplasty, is a commonly performed technique of keratomileusis in the United States. METHODS: A single center consecutive series of 152 eyes undergoing keratomileusis in situ for myopia was analyzed. Spherical equivalent refractions were compared before and after surgery. The standard nomogram supplied with the automatic corneal shaper (Chiron Vision Corp, Irvine, Calif) was used. The mean of preoperative myopia treated was -9.30 +/- 3.10 diopters (D) (range, -5.12 to -22.75 D). RESULTS: Of the 144 eyes with 1 month follow up, 30 (21%) were within 0.50 D of the planned correction at 1 month, 54 (38%) were within 1.00 D, and 97 (67%) were within 2.00 D. At 6 or more months follow up, 51 of 68 eyes (75%) achieved uncorrected visual acuity of 20/40 or better and 13 of 68 (19%) 20/20 or better when eyes with macular degeneration and amblyopia were removed. Forty-six of 78 eyes (59%) with 6 months or greater follow up required retreatment procedures to correct residual myopia or astigmatism. Multiple regression analysis explained 40% of the variation between attempted correction and postoperative results. An overall 5% shift of refraction in the myopic direction occurred between 1 and 6 months. Of the 110 eyes with both 1- and 3-month examinations, the spherical equivalent refraction changed between these time intervals by 1.00 D or more in 54 (49%) eyes; and 11 (31%) eyes changed by 1.00 D or more between the 3- and 6-month examinations. Although 6% of eyes lost 2 or more lines of spectacle-corrected visual acuity, 11% gained 2 or more lines. CONCLUSION: Myopic keratomileusis in situ using the automated lamellar keratoplasty technique appears to be a safe and most effective procedure to reduce moderate to high myopia. However, the predictability of the procedure needs improvement.

Adolescent↗
PubMedDate not supplied

Central islands of corneal steepening after automated lamellar keratoplasty for myopia.

BACKGROUND: Central steep islands are a phenomena of videokeratography that demonstrate local central steepening within a larger diameter area of the cornea treated by refractive surgery that removed stromal tissue to reduce myopia. This report details four cases in which central steep islands occurred following automated lamellar keratoplasty (keratomileusis in situ). METHODS: A total of 43 automated lamellar keratoplasty procedures were performed on 32 patients between January 1993 and September 1993. Central islands were identified using video-keratography. RESULTS: Out of 43 cases of automated lamellar keratoplasty, central steep islands developed in six eyes of four patients. These steep areas developed within a few weeks after surgery; increases in the elevation of these islands correlated with recurring myopia. Slit-lamp microscopy revealed no epithelial surface abnormalities or difficulties with the interface of the resection. A central steep island did not prevent excellent uncorrected visual acuity. After subsequent refractive keratotomy for residual myopia, central steep islands either regressed or disappeared. CONCLUSION: Central islands of corneal steepening may occur after automated lamellar keratoplasty for myopia. The etiology is unknown.

Automation↗
PubMedDate not supplied

Correlation of subepithelial haze and refractive regression 1 month after photorefractive keratectomy for myopia.

PURPOSE: To relate myopic regression after photorefractive keratectomy (PRK) to subepithelial haze at the first postoperative month. METHODS: One hundred nineteen eyes of 119 patients underwent excimer laser PRK for treatment of myopia up to -8.00 D. Eyes were examined at 1, 3, 6, 9, and 12 months after surgery. All eyes received fluorometholone 0.1% for the first 5 postoperative months in a tapered dose. Dexamethasone 0.1% qid for 1 month was prescribed to all eyes with a spherical equivalent refraction less than plano, followed by an augmented dose of fluorometholone 0.1%. Eyes with myopia greater than -0.75 D at 12 months, as well as those that had received dexamethasone at any postoperative interval--regardless of refractive outcome--were considered to be regressed. Eyes that regressed and those that did not regress were compared statistically (Chi-squared statistical criterion with Yate's correction) regarding haze grade. RESULTS: Forty-seven percent (56 of 119) of eyes regressed. In 89.28% (50 of 56) of eyes, subepithelial haze grade was 1 to 2, and in 10.71% (6 of 56), subepithelial haze was graded 0 to 0.5 at 1 month. Fifty-three percent of eyes (63 of 119) did not regress and in all, subepithelial haze was graded 0 to 0.5 at the first month. The correlation between regression and haze grade 1 or more at the first postoperative month was statistically significant (P<.001). CONCLUSION: Mild to marked subepithelial haze (grade 1 to 2) at the first postoperative month after PRK for myopia is strongly related to regression of initial refractive effect and increasing myopia.

Adult↗
PubMedDate not supplied

Long-term results of correction of high myopia with an iris claw phakic intraocular lens.

PURPOSE: Anterior chamber phakic intraocular lenses (PIOLs) are one of the modalities used to correct high myopia. We report the long-term results of our prospective study on the Artisan 5-mm optic myopia lens. METHODS: We studied 67 eyes of 38 consecutive patients with preoperative myopia ranging from -5.38 to -28.00 D. All patients were operated by one surgeon. Mean follow-up was 35 months (24 months in 67 eyes and 36 months in 61 eyes). RESULTS: In 45 eyes (67.2%), postoperative residual refraction was within +/- 1.00 D of emmetropia. The mean refraction was stable statistically during the entire follow-up period. Mean best spectacle-corrected visual acuity improved from 20/40 to 20/32. Mean endothelial cell loss at 6 months was 5.5% (range, -52.4% to +9.3%), at 12 months, 7.21% (range, -53.2% to +20.1%), at 24 months, 9.1% (range -43.6% to +13.6%), and at 36 months, 10.9% (range, -43.0O% to +11.4%). The majority of eyes had an increase in best spectacle-corrected visual acuity; 5 eyes lost best spectacle-corrected visual acuity. We encountered no major complications. CONCLUSION: Implanting the Artisan 5-mm optic myopia lens in high myopic eyes resulted in a stable and accurate refractive outcome. The apparent progressive corneal endothelial cell loss remains a matter of concern.

Adolescent↗
PubMedDate not supplied

Diameters of topographic optical zone and programmed ablation zone for laser in situ keratomileusis for myopia.

PURPOSE: To compare topographic optical zones with programmed ablation zone settings of eyes treated with laser in situ keratomileusis (LASIK) for myopia using the VISX S2 excimer laser. METHODS: Two-hundred three eyes treated with LASIK using the VISX S2 excimer laser were retrospectively evaluated to determine the size of the topographic optical zone. Three to six months after LASIK, the topographic optical zone was measured at the zone of highest curvature on topography and subtraction topography. Eyes were divided into four groups (A, B, C, D) in order of increasing myopia. RESULTS: When the topographic optical zone was compared with the programmed ablation zone, an optical zone reduction of 0.5 +/- 0.1 mm and 0.4 +/- 0.1 mm was found for the longest and shortest diameters, respectively. For eyes with spherical ablation zones, this reduction was 0.6 +/- 0.1 mm and 0.4 +/- 0.1 mm shorter than the programmed horizontal and vertical dimensions. Groups A, B, C, and D, in order of increasing myopia, all showed reductions of approximately 0.5 +/- 0.1 mm for the longest and 0.3 to 0.4 +/- 0.1 mm for the shortest diameters of the optical zone. CONCLUSIONS: The topographic optical zone was reduced from the programmed ablation zone. This reduction was statistically significant for both elliptical and spherical ablations, and seemed to be independent of the amount of myopia.

Cornea↗
PubMedDate not supplied

Prospective, paired comparison of laser in situ keratomileusis and laser epithelial keratomileusis for myopia less than -6.00 diopters.

PURPOSE: To compare visual and refractive results, contrast sensitivity, and tear stability after laser in situ keratomileusis (LASIK) in one eye and laser epithelial keratomileusis (LASEK) in the fellow eye for low myopia. METHODS: Patients diagnosed with low myopia, with a maximum difference of 1 D between their two eyes, were randomly assigned to receive LASEK on one eye and LASIK on the other eye. A total of 64 eyes of 32 patients with a mean age of 26.83 +/- 5.33 years were included in the study. Preoperative myopia ranged from -1.00 to -6.00 D. Follow-up was 6 to 12 months. Uncorrected (UCVA) and best spectacle-corrected visual acuity (BSCVA), Schirmer test results, tear break-up time, corneal asphericity, corneal uniformity index, predicted corneal acuity, and contrast sensitivity values were compared with preoperative values. A Wilcoxon test was used for statistical comparisons and a P-value less than .05 was considered significant. RESULTS: At 6 months after surgery, there was no statistically significant difference in UCVA, BSCVA, spherical and cylindrical refractive error, Schirmer test, or tear break-up time between groups. Contrast sensitivity values in the LASIK eyes were lower in comparison to preoperative values, but there was no change in the LASEK group. CONCLUSIONS: Based on 6-month results, LASEK for low myopia was safe and effective with predictable results, offered early refractive stability, and may be considered an alternative for LASIK.

Adult↗
PubMed1999

Photorefractive keratectomy with an ablatable mask and rail system for simultaneous correction of myopia and astigmatism: preliminary results.

BACKGROUND: Alternative methods to correct myopic astigmatism with excimer laser surgery are being examined in an attempt to increase efficacy and reliability. One approach that is developing interest is the incorporation of a polymethylmethacrylate mask into the laser procedure. We examined the efficacy and safety of the Summit Apex Plus laser using a new ablatable mask and rail system. METHODS: Retrospective study based on follow-up of patients at 1 month (59 eyes), 3 months (37 eyes) and 6 months (24 eyes) at an eye laser centre in southern Ontario. Patients were recruited from 19 ophthalmic practices located primarily in the Niagara region and in western New York. Selected patients with naturally occurring myopia and astigmatism were treated with the Summit Apex Plus laser with the mask and rail system. Patients were evaluated for changes in refraction and visual acuity, and complications (including glare, haloes, haze and lines lost of best corrected visual acuity) were assessed. We calculated the surgically induced refractive change using the Holladay 10-step method. RESULTS: At 6 months the average residual sphere for the low myopia group (-7.00 dioptres or less) was -0.60 D and for the high myopia group (greater than -7.00 D) -0.61 D. This result was found to be both stable and accurate over the follow-up period. The cylinder component was reduced irrespective of the amount of preoperative myopia. Vector analysis showed that in most patients the correction of astigmatism was accurate, although slight undercorrection was observed. Complications were minimal, with few residual adverse effects at 6 months. INTERPRETATION: We found the mask and rail technique to be both effective and safe. Refractive change was stable and accurate, although astigmatism was slightly undercorrected. The procedure resulted in few complications, most of which resolved by 6 months.

Adult↗
PubMed1976

Instrument myopia--microscopy.

Looking through optical instruments stimulates the eye to accommodate more than would be necessary for naked eye viewing; this increased near power is called instrument myopia. The amount (up to -5 diopters) varies with the observer and the conditions of viewing. Using microscopes produces -1.5 to -2 diopters of instrument myopia. More instrument myopia is found with low-power magnification, inexperienced users, and when focusing form minus blur to sharp image. Physiologically, the instrument myopia appears to be associated with an accommodative equilibrium position and, psychologically, with a sensing of proximity.

Accommodation, Ocular↗
PubMed1999

Naturally occurring vitreous chamber-based myopia in the Labrador retriever.

PURPOSE: To investigate whether myopia is present in a breed of domestic dog, the Labrador retriever, and how the ocular components are related to refractive error in this breed. METHODS: Cycloplegic refractive error was measured in 75 Labrador retrievers by retinoscopy. Corneal and crystalline lens radii of curvature were measured in the right eyes of 57 of these dogs using a video-based keratophakometer, with axial ocular dimensions measured using A-scan ultrasonography. RESULTS: Of the 75 dogs tested, 11 (14.7%) were myopic by at least -0.50 D in one eye, and 6 (8.0%) were myopic in both eyes (full range of refractive errors, +3.50 D to -5.00 D). Of the 57 dogs with ocular component measurements, seven (12.3%) were myopic by at least -0.50 D in the right eye. There was a significant negative correlation between refractive error and vitreous chamber depth (Spearman r = -0.42; P < 0.001). Myopic eyes had an elongated vitreous chamber depth (10.87+/-0.34 mm for myopic dogs, 10.02+/-0.40 mm for nonmyopic dogs; P < 0.0001, Kruskal-Wallis test). There was also a significant quadratic association between lens thickness and vitreous chamber depth (P < 0.005; R2 = 0. 11), indicating that thinner lenses occurred at both shorter and longer vitreous chamber depths. CONCLUSIONS: Myopia in the Labrador retriever is analogous to human myopia in that it is caused by an elongated vitreous chamber. Thinner crystalline lenses found at longer vitreous chamber depths may be analogous to lens thinning documented in human ocular development. The Labrador retriever warrants investigation as a potential model of myopia that is naturally occurring rather than experimentally induced.

Animals↗
PubMed1999

[The possibilities of using the newest experimental results in the progressive myopia treatment].

Most recent experimental results concerning the pathomechanism of myopia are discussed. Anatomical, physiological, and biochemical changes taking place in the eye with experimental myopia are described. Special attention is focused on the following substances inhibiting the progress of experimental myopia: apomorphine, reserpine, 6-hydroxydopamine, atropine, pirenzepine, chlorpyrifos, alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid, kainic acid, naloxane, formoguanamine, gentamicin, sodium iodate, central and peripheral antagonist of vasoactive intestinal polypeptide, basic fibroblast growth factor. The possibilities of the above-mentioned pharmacological agents in the progressive myopia treatment are indicated.

Animals↗
PubMed1999

Nearpoint phoria changes associated with the cessation of childhood myopia progression.

BACKGROUND: A convergent (eso) shift in near phoria associated with the onset of myopia has been reported. METHODS: Data from two Midwestern United States optometry practices were used to assess whether the near phoria shifted back in the divergent (exo) direction after the cessation of childhood myopia progression. Data were collected for myopic children who had three or more examinations before the age of 15 years and at least one examination after the age of 17 years. RESULTS: Refractive error data were used to calculate an index of the age of cessation of childhood myopia progression. The phoria at the first examination after the cessation age was designated as the baseline and was normalized to zero. For all previous and subsequent examinations, the changes in phoria with respect to the baseline phoria were calculated. The phoria at the examination just after the cessation age was significantly more divergent than those at the first, third, and fourth examinations prior to the cessation age (1.1, 1.4, and 1.7 prism diopters, respectively). The third visit after the cessation age was 1.8 prism diopters more divergent than the first visit after the cessation age. Thus, these data showed an exo shift in near phoria after the cessation of childhood myopia progression.

Adolescent↗
PubMed1999

[Myopia and labor].

The authors describe 7 cases of pregnant women with high myopia to 15 diopters, who have been delivered vaginally without worsening of the vision and especially of the myopia. That's why the authors practice and recommend a vaginal delivery to women with a myopia, including high-degree myopia.

Adult↗