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PubMed2000

Scanning laser polarimetry in normal subjects and patients with myopia.

AIMS: To examine the changes in the retinal nerve fibre layer (NFL) thickness with age and myopia in normal population. METHODS: Retinal nerve fibre layer thickness was measured with a scanning laser polarimeter (NFA-I) in 180 normal subjects of varying age (range 7-83 years) and in 110 eyes of 85 patients with myopia of varying degrees (range -1.00 to -15.00D). They were all voluntary Anatolian people. Superior to nasal (S/N), inferior to nasal (I/N), and the superior to inferior (S/I) ratios were used for the assessment of retinal NFL thickness. RESULTS: The mean superior NFL ratio was 2.96 and the mean inferior NFL ratio was 2.93 in normal subjects. There was a gradual decrease in NFL ratio with increasing age (simple regression analysis, p<0.05). The mean S/I ratio was 1.01 with a large variation. In patients with myopia, the mean superior NFL ratio was 2.60 and the mean inferior NFL ratio was 2.72. Superior and inferior NFL retardations, and S/I ratio in myopic patients were significantly (15.5%, 10.8%, and 4.9% respectively) lower than that of age matched normals (t test, p<0.05). There was also a gradual decrease in NFL thickness with increasing degree of myopia (simple regression analysis, p<0.05). CONCLUSIONS: Nomograms we obtained for retinal NFL thickness may serve as reference points for the assessment of normal Anatolian people and myopic patients in future studies. NFL thicknesses gradually decreased with increasing age. Patients with myopia had significantly lower NFL thicknesses than normal subjects and, although weakened by wide age range of myopic group, there is a linear relation between severity of myopia and NFL thickness in myopic patients.

Adolescent↗
PubMed2003

Interactions of genes and environment in myopia.

Myopia is a condition in which the eye is too long for the focal length of cornea and lens, and the plane of sharp focus ends up in front of the retina. Given that the growth of the length of the eye is normally controlled with extreme precision by an image-processing feedback mechanism in the retina, myopia can either be the result of inappropriate visual stimulation, genetically determined changes in the gain or offset of the feedback loops or of inappropriate responses of the target tissues. There is no doubt that an environmental component is involved and extended near work appears to be the major risk factor. However, there is also no doubt that myopia is inherited since myopic parents are much more likely to have myopic children, and myopia is far more frequent in Asian populations than in the USA or Europe, even if groups are compared that have performed similar amounts of near work. A number of systemic or ophthalmic diseases are associated with myopia, indicating that metabolic conditions may interfere either with the gains of the feedback loops or the responses of the target tissue, the sclera. Since there is still no therapy against myopia development, research is directed toward the identification of genes that control the axial elongation of the eye.

Animals↗
PubMed1997

Visual deprivation myopia with translucent and black goggles.

To study how different visual deprivation conditions influence the degree of myopia, chicks were reared under conditions of unilateral and bilateral visual deprivation with translucent and black goggles in environments of a 12-hour light/dark cycle and complete darkness. Two weeks after hatching, the refractive errors and axial lengths of the eyes were measured. The deprived eyes of the light/dark-reared chicks exhibited severe myopia both unilaterally and bilaterally as well as axial elongations. The dark-reared chicks exhibited slight myopia in the eyes with goggles and no significant axial elongation. The experiments suggest that different degrees of visual deprivation can also cause severe myopia, that myopia develops independently in each eye, and that a light/dark environment is required for severe myopia to develop.

Animals↗
PubMed2004

Sequence variants in the transforming growth beta-induced factor (TGIF) gene are not associated with high myopia.

PURPOSE: High myopia is a common complex-trait eye disorder, with implications for blindness due to increased risk of retinal detachment, macular degeneration, premature cataracts, and glaucoma. Mapping studies have identified at least four loci for nonsyndromic autosomal dominant high myopia at 18p11.31, 12q22-q23, 17q21-q23, and 7q36. The smallest haplotyped interval for these loci is that of the MYP2 locus on 18p11.31. Recently, the transforming growth beta-induced factor (TGIF) gene was reported to be a candidate gene for MYP2-associated high myopia in single-nucleotide polymorphism studies. The purpose of this study was to determine whether DNA sequence variants in the human TGIF gene are causally related to MYP2-associated high myopia. METHODS: The protein coding regions and intron-exon boundaries of the human TGIF gene were sequenced using genomic DNA samples from MYP2 individuals (affected, unaffected) and external control subjects. The TGIF model used was the April 20, 2003, human genome National Center for Biotechnology Information (NCBI) build 33, which has 10 exons and encodes eight transcript variants. Polymorphic sequence changes were compared to those in the previous report. Reverse-transcription polymerase chain reaction (RT-PCR) was performed to validate TGIF gene expression in ocular tissues. RESULTS: A total of 21 polymorphisms of TGIF were found by direct sequencing: 3 were missense, 2 were silent, 10 were not translated, 4 were intronic, and 2 were homozygous deletions. The 3 missense allelic variants were localized to exon 10 at positions 236C-->T(Pro-->Leu), 244C-->T(Pro-->Ser), and 245C-->T(Pro-->Leu). Silent mutations were observed in exon 10 at positions 177A-->G, 333C-->T. Ten polymorphisms were novel. No sequence alterations were exclusively associated with the affected disease phenotype. RT-PCR results confirmed expression of TGIF in RNA samples derived from human sclera, cornea, optic nerve, and retina. CONCLUSIONS: TGIF is a known candidate gene for MYP2-associated high myopia, based on its mapped location within the MYP2 interval. Mutation analysis of the encoded TGIF gene for MYP2 autosomal dominant high myopia did not identify sequence alterations associated with the disease phenotype. Further studies of MYP2 candidate genes are needed to determine the gene that causes of this potentially blinding disorder.

DNA Mutational Analysis↗
PubMed2005

Heritability of refractive error and familial aggregation of myopia in an elderly American population.

PURPOSE: To determine the heritability of refractive error and the familial aggregation of myopia in an older population. METHODS: Seven hundred fifty-nine siblings (mean age, 73.4 years) in 241 families were recruited from the Salisbury Eye Evaluation (SEE) Study in eastern Maryland. Refractive error was determined by noncycloplegic subjective refraction (if presenting distance visual acuity was < or =20/40) or lensometry (if best corrected visual acuity was >20/40 with spectacles). Participants were considered plano (refractive error of zero) if uncorrected visual acuity was >20/40. Preoperative refraction from medical records was used for pseudophakic subjects. Heritability of refractive error was calculated with multivariate linear regression and was estimated as twice the residual between-sibling correlation after adjusting for age, gender, and race. Logistic regression models were used to estimate the odds ratio (OR) of myopia, given a myopic sibling relative to having a nonmyopic sibling. RESULTS: The estimated heritability of refractive error was 61% (95% confidence interval [CI]: 34%-88%) in this population. The age-, race-, and sex-adjusted ORs of myopia were 2.65 (95% CI: 1.67-4.19), 2.25 (95% CI: 1.31-3.87), 3.00 (95% CI: 1.56-5.79), and 2.98 (95% CI: 1.51-5.87) for myopia thresholds of -0.50, -1.00, -1.50, and -2.00 D, respectively. Neither race nor gender was significantly associated with an increased risk of myopia. CONCLUSIONS: Refractive error and myopia are highly heritable in this elderly population.

Aged↗
PubMed2005

Glucagon- and secretin-related peptides differentially alter ocular growth and the development of form-deprivation myopia in chicks.

PURPOSE: Exogenous glucagon inhibits the induction of myopia in chicks, but the endogenous peptide and receptor that regulate eye growth are unknown. The purpose of this study was to determine which peptides and receptors in the glucagon-secretin family play a role in the control of ocular growth. METHODS: The effect of intravitreally injected peptides on the development of form-deprivation (FD) myopia and on the growth of eyes with unrestricted vision was determined by refraction and A-scan ultrasonography. Chicks received three injections, one every 48 hours, of secretin-related peptides (porcine secretin, human peptide histidine-isoleucine-amide-27, vasoactive intestinal peptide [VIP], VIP fragment 6-28, or pituitary adenylate cyclase-activating polypeptide; 10(-8)-10(-4) M in 20 microL) or five injections of proglucagon-derived peptides (human glucagon, oxyntomodulin, miniglucagon, or glucagon-like peptide [GLP]-2 or chicken GLP-1). Immunohistochemistry was used to detect proglucagon-derived peptides in the eye. RESULTS: Secretin-related peptides had no effect on FD myopia, whereas some proglucagon-derived peptides did. Both glucagon and oxyntomodulin dose-dependently inhibited development of myopia, primarily by inhibition of vitreous chamber elongation (EC(50) = 10(-4) M and 10(-5.5) M, respectively). GLP-1 increased deprivation-induced myopic refractive error by altering anterior chamber development. None of the peptides significantly affected refractive error in eyes with unrestricted vision, although changes in anterior and posterior eye growth were observed in response to glucagon, oxyntomodulin, GLP-1, and miniglucagon. Immunoreactivity for miniglucagon and GLP-1 was colocalized in glucagon-immunoreactive amacrine cells. CONCLUSIONS: Prevention of experimental myopia by exogenous glucagon is mediated by receptors selective for glucagon and oxyntomodulin, indicating that glucagon-like peptides and receptors are probable endogenous retinal regulators of the development of myopia.

Animals↗
PubMed2006

Family-based association analysis of hepatocyte growth factor (HGF) gene polymorphisms in high myopia.

PURPOSE: To investigate the association of high myopia with polymorphisms in the hepatocyte growth factor (HGF) gene, a potential candidate for myopia development. METHODS: Single nucleotide polymorphisms (SNPs) were screened and identified in the HGF gene region with denaturing high-performance liquid chromatography, and their linkage disequilibrium pattern was established in a Han Chinese population (n=150). Tag SNPs were selected and genotyped using restriction digestion and fluorescence polarization assays for 128 nuclear families with 133 severely myopic (mean spherical equivalent [MSE]<or=-10.0 D) offspring. A family-based association study was performed using FBAT and GenAssoc (Cambridge University, Cambridge, UK). RESULTS: Of three tag SNPs (HGF5-5b, HGFe9, and HGFe10b) selected for association study, HGF5-5b, located in the upstream region, was found to be associated with high myopia considered as a quantitative trait (MSE) in additive, dominant, and recessive models (P=0.0157, 0.0108, and 0.0108, respectively). The genotype relative risk was 2.19 for the genotype C/T, and 2.14 for T/T with reference to C/C of HGF5-5b. Significantly reduced transmission was demonstrated for the haplotypes C-A-C (HGF5-5b, HGFe9, and HGFe10b; P=0.0031) and C-A (HGF5-5b and HGFe9; P=0.0015) in the recessive model, whereas significantly increased transmission was found for haplotype T-C (HGF5-5b and HGFe10b; P=0.0040) under the dominant model. Preferential transmission of haplotypes remained significant even after correction for multiple comparisons. Analysis gave similar results, with myopia considered to be a qualitative trait. CONCLUSIONS: HGF is a potential locus associated with high myopia in the Han Chinese population. This is the first study reporting the association of an HGF gene polymorphism with high myopia.

Adult↗
PubMedDate not supplied

Bilateral myopia following blunt trauma to one eye.

PURPOSE: To evaluate bilateral myopia following blunt trauma to one eye. CASE REPORT: Traumatic myopia is a rare transient situation which may be seen in the injured eye or both eyes after blunt ocular trauma. We examined one case with transient myopia in the left eye which had been exposed to a blunt ocular injury. Myopia was also observed in the right eye 12 hours after the trauma. The right eye and left eye had reverted to emmetropia respectively two and six weeks after trauma. DISCUSSION: The myopia may have been due to ciliary spasm arising from stimulation of the efferent autonomic system in the right eye and ciliary body edema in the left eye. CONCLUSIONS: To our knowledge, this is the first reported case developing bilateral transient myopia after the blunt trauma to only one eye.

Accommodation, Ocular↗
PubMedDate not supplied

Use of optical coherence tomography in myopia.

PURPOSE: To measure retinal thickness and retinal nerve fiber layer thickness using optical coherence tomography in patients with myopia. PATIENTS AND METHODS: Thirty patients (13 girls and 17 boys) 14 to 18 years old were included in the study. The control group consisted of 15 patients. Each patient was subjected to routine ophthalmic investigations, which included the assessment of visual acuity for near and distant objects, autorefractometry, measurement of intraocular pressure, biometry, and assessment of the static visual field. The foveal retinal thickness and the peripapillary nerve fiber layer thickness were measured using optical coherence tomography. RESULTS: The mean foveal retinal thickness was 231.0 microm in eyes with low myopia, 218.0 microm in eyes with medium myopia, and 178.0 microm in eyes with high myopia. The mean thickness of the retinal nerve fiber layer was 150.0 microm, 140.0 microm, and 152.0 microm, respectively. Statistically significant differences were revealed between patients with high myopia and the control group. CONCLUSION: Optical coherence tomography can be employed to assess the retinal thickness and thus facilitate the detection of the evolution of alterations in myopia.

Adolescent↗
PubMedDate not supplied

Myopia in preterm children at 12 to 24 months of age.

PURPOSE: To examine biometric factors that may influence the high incidence of myopia in pre-term children at 12 to 24 months of age. PATIENTS AND METHODS: Fifty eyes of 25 patients with myopia and 70 eyes of 35 patients with emmetropia at 12 to 24 months of age were selected from a group of preterm children who had been screened for retinopathy of prematurity and returned for follow-up examinations. Forty eyes of 20 full-term children of the same age were also included in the study as a control group. A-scan ultrasonography was performed to measure axial length, lens thickness, and anterior chamber depth in the three groups. RESULTS: The myopic group had a significantly greater axial length than did the other groups. However, the three groups did not differ in lens thickness or anterior chamber depth. The degree of myopia increased with the increase in axial length and the decrease in anterior chamber depth. CONCLUSIONS: The development of myopia in preterm children 12 to 24 months of age appears to be influenced mainly by axial length, whereas the degree of myopia seems to be related to axial length and anterior chamber depth. Among refractive components, axial length plays a major role in myopia occurring at this age in preterm patients.

Anterior Chamber↗
PubMedDate not supplied

Excimer laser photorefractive keratectomy for myopia: two-year follow up.

This study, comprising 60 eyes with a follow up of at least 2 years, was designed to evaluate the efficacy and safety of excimer laser photorefractive keratectomy (PRK) for myopia in Japanese people. Eyes were divided into three groups: low myopia group (-2.00 diopters (D) to -3.00 D), 11 eyes; medium myopia group (-3.10 D to -6.00 D), 28 eyes; and high myopia group (-6.10 D to -14.00 D), 21 eyes. In 60 eyes, uncorrected visual acuity improved and spectacle corrected visual acuity remained unchanged. At 2 years, 100%, 75%, and 52%, respectively, of the low, medium, and high myopia groups, were within +/- 1.00 D of the attempted correction. Twenty-two eyes (37%) developed corneal haze of grade 2 or more. These data show that in low or medium myopia the predictability is good. But we think we have to pay attention to the strong haze, which seems to have developed more frequently in Japanese people than in previous reports of PRK in Caucasians.

Adult↗
PubMedDate not supplied

Three multizone photorefractive keratectomy algorithms for myopia. The Melbourne Excimer Laser Group.

OBJECTIVE: To compare the efficacy and complications of three different excimer laser algorithms for multizone photorefractive and photoastigmatic keratectomy. METHODS: Three different software algorithms were applied to treat myopia and myopic astigmatism with the VISX 20/20 excimer laser. Each algorithm had a maximum ablation zone of 6 mm but differed in the number of zones employed, the proportion of the total treatment allocated to each ablation zone, and the treatment of astigmatism. The Melbourne multizone technique equally divided myopia correction into a maximum of three ablation zones. The Pop multizone technique biased myopia treatment into the smaller diameter zones to a maximum of six ablation zones, with one central island pretreatment. The Alpins multizone technique equally divided myopia treatment through all zones up to a maximum of six, with one central island pretreatment. RESULTS: A total of 585 patients (780 eyes) were treated and 625 eyes (80%) were followed for more than 6 months. The mean baseline spherical equivalent refractive error was -5.63 D (-1.00 to -19.50 D). Between 71 and 79% of eyes were treated for astigmatism. There was no statistically significant differences in baseline refractive error or other characteristics among the three groups. At 6 months, the Alpins multizone algorithm had more eyes with a refractive error within +/- 1.00 D of emmetropia (p = 0.01) and more within +/- 2.00 D of emmetropia (p < 0.01). This new algorithm produced more eyes with an uncorrected visual acuity of 20/20 or better at 6 months (p < 0.01). When multiple logistic regression was used to correct for any differences in baseline myopia among the three groups, this algorithm also had a higher odds ratio for achieving 20/20 or better uncorrected visual acuity (OR = 1.58). CONCLUSION: At 6 months, all three algorithms were effective in the reduction of myopia. Significantly better visual acuity and refractive results were achieved with the Alpins multizone algorithm that spread the total treatment over a larger number of ablation zones, with an equal number of diopters of treatment in each zone.

Adolescent↗
PubMed2006

Higher order ocular aberrations in eyes with myopia in a Chinese population.

PURPOSE: To describe the characteristics of higher order ocular aberrations of adult Chinese eyes with myopia. METHODS: Higher order aberrations in consecutive right eyes of 166 Chinese patients with myopia who enrolled for preoperative assessment for LASIK were retrospectively reviewed. Wavefront aberrations were measured with the Bausch & Lomb Zywave over a 6-mm dilated pupil. The correlations between higher order aberrations and myopia, astigmatism, and age, respectively, were analyzed. RESULTS: Mean patient age was 32.1 +/- 6.2 years, the mean refractive error was sphere -5.23 +/- 1.79 diopters (D) and cylinder -1.29 +/- 0.98 D. The mean of the total higher order root-mean-square (RMS) (third to fifth order) was 0.49 +/- 0.16 microm. Third-order RMS was largest (mean 0.37 +/- 0.16 microm), followed by fourth-order RMS (mean 0.29 +/- 0.11 microm). For individual higher order Zernike coefficients, spherical aberration (C4(0)) predominated with a mean of 0.23 +/- 0.14 microm. No correlation was found between total higher order RMS and myopia or between total higher order RMS and age. Small but statistically significant relationships were found in the following groups: age and vertical primary coma (C3(-1))(r=-0.206, P=.008); age and spherical aberration (C4(0)) (r=0.196, P=.012); and myopia and horizontal trefoil (C3(3)) (r=-0.158, P=.042). CONCLUSIONS: Higher order aberrations varied among individuals with myopia. Third-order RMS was the predominant higher order aberration. Spherical aberration and vertical primary coma increased slightly with age. Our study helps establish ocular aberration standards for Chinese refractive surgery candidates.

Adult↗
PubMed2006

Attrition of military enlistees with a medical waiver for myopia, 1999-2001.

BACKGROUND: Military service requires physical fitness, including vision within set standards. Premature attrition inflicts a considerable manpower and fiscal burden upon the military. METHODS: We conducted a retrospective cohort survival analysis of newly enlisted military personnel who entered active duty with a medical waiver for myopia between January 1, 1999, and December 31, 2001. Premature attrition rates, both medical and overall, were compared with those for a matched, fully qualified, comparison group. RESULTS: New enlistees with a waiver for myopia had the same probability of remaining on active duty through the first 2 years of service as did fully qualified peers. Enlistees with a waiver for myopia also had a low probability of an early medical discharge for myopia. CONCLUSION: The results of this study tend to validate the current branch-specific myopia waiver processes. They also provide evidence that current myopia accession criteria may be too restrictive and in need of policy review.

Adolescent↗
PubMedDate not supplied

[The clinical results of using specialized laser keratomileusis for the correction of myopia].

Laser in-situ keratomileusis has been performed on 2023 eyes of 1162 patients with myopia of 1-18 diopters and complex myopic astigmatism of 0.75-5 diopters. A Hansatome TM 230 HT keratome and Nidek EC 5000 eximer laser device were employed. The resultant refraction and visual acuity were analyzed during one year postoperation in different age groups and groups with myopia of different degree. In myopia of up to 6 diopters high visual acuity without correction (0.93-0.99) was attained in all age groups. In higher myopia, visual acuity has been increasing over the entire period of observation, the gradient of its alteration being 0.17-0.27. The final visual acuity formed in presbiopes during 3 months. The spherical refraction equivalent of up to 1 diopter was 96.1%. The mean refraction values were stable during the entire period of observation. In myopia of 9.5 diopters and higher the residual myopia in patients aged over 30 years was approximating 1.0 diopters. Hypercorrection was observed in 1.3%, hypocorrection in 2.6% cases. The described combination of equipment for laser keratomileusis provides stable visual and refraction results at a lower incidence of complications.

Adult↗
PubMed1999

Excimer laser photorefractive keratectomy for the correction of myopia.

AIM OF STUDY: To ascertain the efficacy, predictability, safety and stability of photorefractive keratectomy (PRK) for the correction of myopia. METHODS: Nine-hundred and seventy-one eyes of 628 patients had PRK performed for the correction of myopia. The mean pre-operative myopia was -5.7 D +/- 2.21 D (range -1.0 D to -15.25 D). The mean attempted correction was -5.0 D +/- 1.9 D (range -1.0 D to -9.90 D). RESULTS: Four-hundred and sixty-seven eyes had a follow-up of 6 months or more. Ninety-three percent of low myopic eyes (pre-operative myopia of less than or equal to 6.0 D) and 75% of high myopic eyes (pre-operative myopia of more than 6.0 D) attained an unaided visual acuity of 6/12 or better. Seventy-four percent of low myopic and 50% of high myopic eyes were within 1 D of the intended correction. The mean post-operative refraction at 6 months was 0.60 D +/- 1.46 D. Eight eyes in the high myopia group and 1 eye in the low myope group lost 2 or more lines or best-corrected visual acuity. CONCLUSION: PRK was safer and produced better results for low myopes.

Adult↗
PubMed1999

[Contemporary views on the etiology, pathogenesis as well as treatment of school-age and progressive myopia].

The contemporary views on the etiology, pathogenesis as well as treatment of school-age and progressive myopia are discussed. The history of myopia investigations is described. The results of papers indicating environmental and genetic reasons of myopia are presented. The anatomical, physiological, and biochemical changes taking place during the school-age and progressive myopia progress are characterized. The attitude towards some conservative and surgical methods of school-age and progressive myopia is expressed. The possibilities of using the newest experimental results in progressive myopia treatment are indicated.

Adolescent↗
PubMed2000

Scleral remodeling during the development of and recovery from axial myopia in the tree shrew.

PURPOSE: Recent investigations have suggested that scleral thinning in mammalian eyes with axial myopia is a consequence of the loss of scleral tissue, rather than the redistribution of existing tissue as the eye enlarges. The present study investigated whether further changes in the distribution and metabolism of scleral tissue occur during the process of recovery from axial myopia. Scleral glycosaminoglycan (GAG) synthesis and content as well as scleral dry weight changes were monitored as indicators of remodeling in myopic and recovering tree shrew sclerae. METHODS: Myopia was induced in tree shrews by monocularly depriving them of pattern vision. Some animals then had the occluder removed and were allowed to recover from the induced myopia for periods of 1, 3, 5, 7, and 9 days. Newly synthesized GAGs were radiolabeled in vivo with [(35)S]sulfate. Sulfate incorporation and total GAG content in the sclera was measured through selective precipitation of GAGs from proteinase K digests with alcian blue dye. Dry weights of the sclerae were also determined. Changes in ocular refraction and eye size were monitored using retinoscopy, keratometry, and ultrasonography. RESULTS: Eyes developing myopia showed a significant reduction in scleral GAG synthesis, particularly in the region of the posterior pole (-36% +/- 7%) compared with contralateral control eyes. Scleral dry weight was also significantly reduced in these eyes (-3.7% +/- 1.2%). In recovering eyes, significant changes in GAG synthesis were apparent after 24 hours of recovery. After 3 days of recovery, significantly elevated levels of GAG synthesis were found (+79% +/- 15%), returning to contralateral control eye values after 9 days of recovery. Interocular differences in scleral dry weight were shown to follow a similar pattern to that observed for GAG synthesis. CONCLUSIONS: Active remodeling, resulting in either the loss or replacement of scleral tissue and not passive redistribution of scleral tissue, is associated with changes in eye size during both myopia development and recovery. Regulatory changes in scleral metabolism can be rapidly evoked by a change in visual conditions and the direction of regulation is related to the direction of change in eye size.

Animals↗