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PubMed1996

[Intrastromal keratectomy in high myopia. 1 year results].

Photorefractive keratectomy (PRK) by excimer laser is now a scientifically established treatment method in low and moderate myopia. In high and very high myopia, however, the formation of severe corneal haze or scars and a considerable regression of refraction remain obstacles to the use of PRK. One approach to these two problems is to perform an intrastromal keratectomy. PATIENTS AND METHOD. Between September 1992 and September 1994 intrastromal keratectomy was carried out in 42 eyes with myopia between -8.625 and -36 D. Twenty-one eyes (spherical equivalent of pre-operative refraction between -12.12 and -36 D) were treated by keratomileusis in situ, and 21 eyes (spherical equivalent of pre-operative refraction between -8.625 and -29.25 D) by intrastromal excimer laser keratectomy. Thirty-two eyes were followed up for at least 12 months. RESULTS. The post-operative refraction (spherical equivalent) ranged between +1.375 D and -5.0 D in the keratomileusis in situ group and between +1.5 D and -3.0 D in the intrastromal excimer laser keratectomy group. Nearly all patients regained their pre-operative visual acuity quickly. In the long-term follow-up (1 year) no significant regression of refraction occurred; the pre-operative visual acuity was regained in both groups after 1 year. Significant astigmatism was not induced. CONCLUSIONS. Intrastromal keratectomy is able to correct even very high myopias quite precisely and without regression of the refractive outcome. In addition, considerable haze can be avoided. For these reasons, in high and very high myopia intrastromal keratectomy seems to be superior to conventional anterior photorefractive keratectomy (PRK) by excimer laser.

Adult↗
PubMed1996

Excimer laser photorefractive keratectomy for myopia.

To evaluate the safety, effectiveness and stability of excimer laser photorefractive keratectomy (PRK) treatment, we studied its posttreatment results in 44 normal-sighted myopic eyes where a 193-nm emission wavelength excimer laser was used to correct myopia. The eyes were divided into three groups according to the preoperative refractive error and attempted correction: group I, preoperative myopia < or = 6.00 diopters (D), full correction; group II, preoperative myopia between 6.00 and 8.00 D, full correction; group III, preoperative myopia > 8.00 D, attempted correction of 8.00 D. Percentages of relative spherical equivalents (ie, observed spherical equivalent -- expected spherical equivalent) within +/- 1.0 D 3 months after treatment were 95% in group I, 64% in group II and 67% in group III. Uncorrected visual acuity of 20/40, or better, was achieved in 100% of eyes in group I, and 92% in group II at 6 months. Initial overcorrection followed by myopic regression was observed in all groups. The refractive outcome in our study was stable 3 months after surgery. Anterior stromal haze was mild and disappeared gradually 3 months postoperatively. The greater the diopter correction needed, the higher the grade of corneal haze (p < 0.01). There were no significant complications. The results of this study demonstrated that excimer laser PRK appears to be a reasonably predictable and stable procedure to correct low to moderate myopia.

Adult↗
PubMed1996

Is computer use a risk factor for myopia?

BACKGROUND: Many patients who become myopic or who undergo increases in myopia as adults have concerns about whether the use of video display terminals (VDTs) contributes to these changes in refractive error. This paper is an overview of the current literature on topics concerning VDTs and factors related to proposed etiologies for myopia. METHODS: Selected literature is reviewed on the relationship between VDTs and asthenopia, fatigue, accommodation, and vergence. Clinical studies of myopic progression and transient myopia among VDT users are considered, as is television viewing as a risk factor for juvenile myopia. RESULTS/CONCLUSIONS: Reports of asthenopia are common with VDT use by a factor of 1.4 to 1.5, compared to conventional office work. Questions of comparability remain between VDT users and nonusers with respect to confounding variables such as the number of work hours. Proofreading on a VDT appears to be less efficient than using printed copy. Despite screen flicker and reflections, the accommodative response appears to be accurate to a VDT. Transient, fatigue-induced changes in accommodation and vergence may occur after work with VDTs. Despite these near point changes, there is no compelling evidence in the literature that suggests there is a significant increase in the risk of myopia onset or progression from the use of VDTs by adults compared to other forms of near work.

Accommodation, Ocular↗
PubMed1996

[Severe myopia and delivery].

AIM: There has been concern that patients with high myopia are at a risk of developing retinal tears as they go through a spontaneous delivery. Therefore the aim of the paper was to examine retinal changes in the group of female patients with high myopia before and after delivery. MATERIAL AND METHODS: Eye examinations were performed before and after delivery in two groups of patients: 42 patients with high myopia and 4 patients with high myopia and retinal detachment surgery in one eye. RESULTS: There was no progression of retinal changes and development of retinal tears, but in some patients retinal hemorrhages and macular edema were observed. CONCLUSIONS: High myopia is not the indication for the cesarean section, but the patients should be examined after the delivery.

Adult↗
PubMedDate not supplied

[Acoustic studies of the sclera in progressive myopia in children and adolescents].

Acoustic density of the sclera (ADS) was examined using ultrasonic scanning device Ophthascan-B in 121 eyes of 91 patients aged 9 to 17 with progressive myopia of 3.5 to 14.0 diopters. ADS of the posterior pole and eyeball equator were measured separately. ADS in health was 47.6ë0.24 dB for the posterior pole and 46.0ë0.24 dB for the equator, in myopia 41.7ë0.26 and 38.8ë0.22 d, respectively. ADS in the eyes with myopia developing at school age was reliably higher than in cases with congenital and early acquired myopia. The lowest ADS values for both the posterior pole and equator were detected in patients with high early acquired myopia.

Adolescent↗
PubMed1997

[Photorefractive excimer laser keratectomy in myopia and astigmatism with a 2-year follow-up after surgery].

In a group of 1037 operated eyes the effectiveness, predictive value, stability and safety of photorefraction keratectomy by means of an excimer laser was tested in myopia (PRK) and astigmatism (PARK) with a two-year follow-up period after operation. The range of the preoperative refraction defect was -1.75 to -2.10 dpt (SE). The maximal value of the corrected cylinder in astigmatism was -6.0 cyl dpt. In the PRK group 459 operations were evaluated, in the PARK group 578 operations. Both groups are classified according to the spherical equivalent of the refractory defect into three groups. Group A is formed by myopia up to -6.0 dpt, group B myopia -6.25 to -10.0 dpt and group C above -10.25 dpt. Non-corrected visual acuity 6/12 and better was recorded in the 20th month after operation in group A in 93.4-97.6% (PARK-PRK) operated eyes, in group B 88.7-91.5% and in group C 61.2-68.4% of operated eyes. The achieved final refraction (SE) in an interval +(-1.0) dpt from the originally planned one was recorded during the 20th month after operation in group A in 92.8-96.5% (PARK-PRK) operated eyes, in group B 73.5-78.9% and in group C 59.7-63.5% operated eyes. The best corrected visual acuity (NKZO) in the whole group 20 months after operation was unaltered or better by 1 line of projected optotypes as compared with NKZO before operation in group A in 97.6%, in group B in 94.3% and in group C in 89.7% operated eyes. The analysis of results in PRK and PARK in the group with a two-year follow-up period after operation permits to evaluate the method as sufficiently effective and safe for correction of myopia up to -10.0 dpt but less predictive in myopia above -10.0 dpt.

Adult↗
PubMedDate not supplied

[Transconjunctival electrostimulation of eye in pathogenetic therapy of progressive myopia].

Disorders of accommodation are acknowledged to contribute to the etiopathogenesis of myopia. A new method for treating this condition is proposed: Transconjunctival electroophthalmostimulation (TEOS). It was used in the treatment of 384 patients with progressive myopia. The treatment had a favorable impact on vision acuity and accommodation. The efficacy of treatment was the best in patients with myopia of up to 1.5 diopters; vision acuity in them increased by an average of 0.3 +/- 0.04, the accommodation volume by 2.23 +/- 0.29 diopters, and the relative accommodation reverse by 1.45 +/- 0.44 diopters. In medium and high myopia TEOS effect was less expressed as regards the vision acuity, whereas decreased accommodation virtually normalized; the subjective refraction reliably decreased (by 0.5 diopters) in all groups of examinees. Other parameters of static refraction were virtually unchanged by TEOS. Moreover, the rheographic coefficient increased from 1.59 +/- 0.66 to 2.89 +/- 0.66 and the temperature of the eyeball rose from 34.2 +/- 0.15 to 35.2 +/- 0.05 degrees C, which indicates activation of blood supply and metabolic processes under the effect of TEOS. Five-year follow-up of this cohort of patients showed the progress of myopia in just 15% of cases, versus 25% in the control group treated with drugs and accommodation training. The effect of treatment persists for one year, after which the treatment is to be repeated.

Accommodation, Ocular↗
PubMedDate not supplied

Near esophoria is associated with high myopia.

BACKGROUND: A retrospective study was undertaken to examine the hypothesis that esophoria is associated with higher amounts of myopia. METHODS: One hundred and forty-four subjects were selected from the files of optometry clinics at the Department of Optometry, National University of Malaysia, from the years 1995 to 1998 inclusive. These subjects were matched in terms of age group, sex, race and near phoria group. Near phorias were determined by Maddox wing technique and were classified into three groups: more than six prism dioptres exophoria, zero to six prism dioptres exophoria and any esophorias. RESULTS: One way analysis of variance revealed that there were significant differences in mean myopias between the three phoria groups (ANOVA, F(2,141) = 5.34, p < 0.01). Further analysis with the Student-Newman-Keuls test showed that the amount of myopia is significantly higher in the esophoric group than in the other two groups. CONCLUSIONS: The results support the hypothesis that near esophoria is associated with high myopia. This study suggests that near phoria might be an important factor in myopia development.

Journal Article↗
PubMed2003

U.S. Food and Drug Administration clinical trial of the Implantable Contact Lens for moderate to high myopia.

PURPOSE: To assess the safety and efficacy of the Implantable Contact Lens (ICL) to treat moderate to high myopia. DESIGN: Prospective nonrandomized clinical trial. PARTICIPANTS: Five hundred twenty-three eyes of 291 patients with between 3 and 20.0 diopters (D) of myopia participating in the U. S. Food and Drug Administration clinical trial of the ICL for myopia. INTERVENTION: Implantation of the ICL. MAIN OUTCOME MEASURES: Uncorrected visual acuity (UCVA), refraction, best spectacle-corrected visual acuity (BSCVA), adverse events, operative and postoperative complications, lens opacity analysis (Lens Opacity Classification System III), subjective satisfaction, and symptoms. RESULTS: Twelve months postoperatively, 60.1% of patients had a visual acuity of 20/20 or better, and 92.5% had an uncorrected visual acuity of 20/40 or better. Patients averaged a 10.31-line improvement in UCVA, 61.6% of patients were within 0.5 D, and 84.7% were within 1.0 D of predicted refraction. Only one case (0.2%) lost > 2 lines of BSCVA. Gains of 2 or more lines of BSCVA occurred in 55 cases (11.8%) at 6 months and 41 cases (9.6%) at 1 year after ICL surgery. Early and largely asymptomatic, presumably surgically induced anterior subcapsular (AS) opacities were seen in 11 cases (2.1%); an additional early AS opacity (0.2%) was seen because of inadvertent anterior chamber irrigation of preservative-containing solution at surgery. Two (0.4%) late (> or = 1 year postoperatively) AS opacities were observed. Two (0.4%) ICL removals with cataract extraction and intraocular lens implantation have been performed. Patient satisfaction (very/extremely satisfied) was reported by 92.4% of subjects on the subjective questionnaire; only four patients (1.0%) reported dissatisfaction. Slightly more patients reported an improvement at 1 year over baseline values for the following subjective symptoms: quality of vision, glare, double vision, and night driving difficulties. Only a 3% difference between pre-ICL and post-ICL surgery was reported for haloes. CONCLUSIONS: The results support the safety, efficacy, and predictability of ICL implantation to treat moderate to high myopia.

Adult↗
PubMed1999

Does overcorrecting minus lens therapy for intermittent exotropia cause myopia?

BACKGROUND: Overcorrecting minus lens therapy has been used as a treatment for intermittent exotropia. It is based on the principle that an exotropic deviation will be decreased by stimulating accommodative convergence with additional minus power in spectacles. Because excessive accommodation has been implicated as a cause of myopia, there is theoretical concern that overcorrecting minus lens therapy for exotropia may cause myopia. OBJECTIVE: To investigate the effect of overcorrecting minus lens therapy for exotropia on the progression of myopia. DESIGN: A retrospective chart review. SUBJECTS AND METHODS: Seventy-four patients with intermittent exotropia were treated with overcorrecting minus lens therapy for at least 6 months (6-month treatment group), and a 34-patient subset of them received overcorrecting minus lens therapy for 5 years (5-year treatment group). The mean change in refractive error (spherical equivalent of the fixing eye) of these 2 groups 5 years after initial examination was compared with the mean change in refractive error of a control group of 45 patients with intermittent exotropia who did not receive overcorrecting minus lens therapy. RESULTS: At the time of initial examination, the mean (+/-SD) refractive error was 0.00 +/- 1.40 diopters (D) in the control group, 0.00 +/- 1.50 D in the study group, and -0.10 +/- 1.50 D in the 5-year study group, all of which were essentially identical. Five years after initial examination, the mean change in refractive error was -1.40 +/- 2.80 D in the control group, -1.52 +/- 1.80 D in the 6-month treatment group, and -1.54 +/- 1.80 D in the 5-year treatment group. These differences in the change in refractive error (myopic shift) were not statistically significant (t test), and the differences are clinically unimportant. CONCLUSION: Overcorrecting minus lens therapy for intermittent exotropia does not appear to cause myopia.

Accommodation, Ocular↗
PubMed2000

Subretinal surgery for choroidal neovascularization in patients with high myopia.

OBJECTIVE: To analyze the visual outcome in patients undergoing surgical removal of subfoveal choroidal neovascularization (CNV) in eyes with high myopia. METHODS: We retrospectively reviewed the medical records of 48 consecutive patients with high myopia (> or =6 diopters [D]) who underwent vitrectomy with surgical removal of subfoveal CNV. The patient population consisted of 2 groups. Group 1 included 23 patients with findings only of myopic degeneration, and group 2 included 25 patients with presumed ocular histoplasmosis syndrome and myopia of 6 D or more. RESULTS: In group 1, the visual acuity improved by 2 or more Snellen lines in 9 eyes (39%), decreased in 8 eyes (35%), and remained unchanged in 6 (26%), with a mean follow-up of 24 months (range, 8-60 months). The preoperative visual acuity was 20/40 or better in only 1 eye (4%), but 8 (35%) achieved a final visual acuity of 20/40 or better. In group 2, the visual acuity improved in 16 eyes (64%), was stable in 4 (16%), and deteriorated in 5 (20%), with a mean follow-up of 18 months (range, 6-44 months). Only 3 eyes (12%) had a preoperative visual acuity of 20/40 or better, but 11 (44%) achieved a final visual acuity of 20/40 or better. Recurrence occurred in 13 (57%) of the 23 eyes in group 1 and in 9 (36%) of the 25 eyes in group 2. Univariate analysis demonstrated a significant relation between younger patient age (group 1) and absence of postoperative CNV recurrence (group 2) and an improvement of visual acuity (P<.01). CONCLUSIONS: Surgical removal of CNV may provide visual benefit in selected cases of subfoveal CNV associated with high myopia. The determination of whether surgical intervention is appropriate in these cases requires a prospective, randomized, clinical trial.

Adolescent↗
PubMed2004

X-linked high myopia associated with cone dysfunction.

OBJECTIVE: Bornholm eye disease (BED) consists of X-linked high myopia, high cylinder, optic nerve hypoplasia, reduced electroretinographic flicker with abnormal photopic responses, and deuteranopia. The disease maps to chromosome Xq28 and is the first designated high-grade myopia locus (MYP1). We studied a second family from Minnesota with a similar X-linked phenotype, also of Danish descent. All affected males had protanopia instead of deuteranopia. METHODS: X chromosome genotyping, fine-point mapping, and haplotype analysis of the DNA from 22 Minnesota family individuals (8 affected males and 5 carrier females) and 6 members of the original family with BED were performed. Haplotype comparisons and mutation screening of the red-green cone pigment gene array were performed on DNA from both kindreds. RESULTS: Significant maximum logarithm of odds scores of 3.38 and 3.11 at theta = 0.0 were obtained with polymorphic microsatellite markers DXS8106 and DXYS154, respectively, in the Minnesota family. Haplotype analysis defined an interval of 34.4 cM at chromosome Xq27.3-Xq28. Affected males had a red-green pigment hybrid gene consistent with protanopia. We genotyped Xq27-28 polymorphic markers of the family with BED, and narrowed the critical interval to 6.8 cM. The haplotypes of the affected individuals were different from those of the Minnesota pedigree. Bornholm eye disease-affected individuals showed the presence of a green-red hybrid gene consistent with deuteranopia. CONCLUSIONS: Because of the close geographic origin of the 2 families, we expected affected individuals to have the same haplotype in the vicinity of the same mutation. Mapping studies, however, suggested independent mutations of the same gene. The red-green and green-red hybrid genes are common X-linked color vision defects, and thus are unrelated to the high myopia and other eye abnormalities in these 2 families. CLINICAL RELEVANCE: X-linked high myopia with possible cone dysfunction has been mapped to chromosome Xq28 with intervals of 34.4 and 6.8 centimorgan for 2 families of Danish origin.

Adolescent↗
PubMed1987

Intelligence, education, and myopia in males.

We conducted a nationwide study of the relationship among refractive error, intelligence scores, and years of schooling in 157,748 males aged 17 to 19 years. We found a strong association of myopia with both intelligence and years of school attendance. The prevalence of myopia was found to be significantly higher in the more intelligent and more educated groups. By fitting models of logistic regressions, we worked out a formula expressing the relationship among the rate of myopia, years of schooling, and intelligence level. We found that years of schooling and intelligence weigh equally in the relationship with myopia.

Adolescent↗
PubMed2005

Laser photocoagulation for choroidal neovascularisation in pathologic myopia.

BACKGROUND: Pathologic myopia is usually defined as the need for a spectacle correction of -6 diopters or higher. Choroidal neovascularisation (CNV) is the most commonly occurring cause of visual loss in people with pathologic myopia. In myopic macular degeneration the occurrence of newly formed vessels in the macula often leads to a fibrotic pigmented scar causing a blind spot in the centre of the visual field. OBJECTIVES: The primary objective of this review was to examine the effects of laser photocoagulation for CNV associated with pathologic myopia. A secondary objective was to compare the effects of different photocoagulation techniques. SEARCH STRATEGY: We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Group Trials Register) on The Cochrane Library (Issue 2, 2005), MEDLINE (1966 to July 2005), EMBASE (1980 to July 2005, week 28), LILACS (July 2005) and the reference lists of included studies. SELECTION CRITERIA: We included randomised controlled trials comparing photocoagulation with observation or comparing different photocoagulation techniques in people with CNV associated with myopia of -6 diopters or higher. DATA COLLECTION AND ANALYSIS: Two authors independently assessed the search results for eligibility. MAIN RESULTS: Two studies were included that enrolled people with CNV located at 100 microns or more from the foveal centre. One study compared photocoagulation with observation. At the final examination, 16/35 participants randomised to photocoagulation versus 31/35 randomised to observation had visual acuity of 20/100 or worse after 6 to 48 months. The second study randomised 27 eyes (26 patients) to photocoagulation with three laser wavelengths (9 eyes per group). The number of eyes losing two or more lines was 2 (577 nm), 3 (590 nm) and 3 (620 nm) after 3 to 17 months. In both studies comparisons were made using outcomes assessed at the final examination. As the final examination took place at different follow-up times it was difficult to interpret the findings and it was impossible to extract data for further analyses. AUTHORS' CONCLUSIONS: Despite its use over several years the effectiveness of laser photocoagulation for myopic CNV has not been established. Although there was a suggestion of short-term effectiveness in one small study on non-subfoveal CNV the results were potentially biased. Observational studies suggest that the enlargement of the atrophic laser scar after laser treatment of non-subfoveal CNV could be a potentially vision-threatening long-term complication, even in eyes free of CNV recurrence.

Choroidal Neovascularization↗
PubMed2006

Photorefractive keratectomy (PRK) versus laser-assisted in-situ keratomileusis (LASIK) for myopia.

BACKGROUND: Myopia (also known as short-sightedness or near-sightedness) is an ocular condition in which the refractive power of the eye is greater than is required, resulting in light from distant objects being focused in front of the retina instead of directly on it. The two most commonly used surgical techniques to permanently correct myopia are photorefractive keratectomy (PRK) and laser-assisted in-situ keratomileusis (LASIK). OBJECTIVES: The aim of this review was to compare the effectiveness and safety of PRK and LASIK for correction of myopia. SEARCH STRATEGY: We searched the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library (2005, Issue 3), MEDLINE (1966 to September 2005), EMBASE (1980 to September 2005) and LILACs (1982 to 3 November 2005). We also searched the reference lists of the studies and the Science Citation Index. SELECTION CRITERIA: We included randomised controlled trials comparing PRK and LASIK for correction of any degree of myopia. We also included data on adverse events from prospective multicentre consecutive case series in the Food and Drugs Administration (FDA) trials database (http//www.fda.gov/cdrh/LASIK/lasers.htm). DATA COLLECTION AND ANALYSIS: Two authors independently assessed trial quality and extracted data. Data were summarised using odds ratio and mean difference. Odds ratios were combined using a random-effects model after testing for heterogeneity. MAIN RESULTS: This review included six randomised controlled trials involving a total of 417 eyes, of which 201 were treated with PRK and 216 with LASIK. We found that although LASIK gives a faster visual recovery than PRK, the effectiveness of these two procedures is comparable. We found some evidence that LASIK may be less likely than PRK to result in loss of best spectacle-corrected visual acuity. AUTHORS' CONCLUSIONS: LASIK gives a faster visual recovery than PRK but the effectiveness of these two procedures is comparable. Further trials using contemporary techniques are required to determine whether LASIK and PRK are equally safe.

Humans↗
PubMed1999

Modulation of scleral DNA synthesis in development of and recovery from induced axial myopia in the tree shrew.

Visually modulated scleral extracellular matrix remodelling is associated with the development of, and recovery from, induced axial myopia in the tree shrew, a commonly used mammalian model of refractive error development. The involvement of scleral cell proliferation in this process was investigated using [3H] thymidine. Tree shrews were monocularly deprived of pattern vision, using translucent occluders, or the retinal image was optically defocused, using negative lenses, over a period of 5 days. A further group was monocularly deprived for 5 days, then allowed 3 days of binocular recovery. A control group of binocularly open animals was employed to establish normal parameters. On the final day of the experimental period, [3H] thymidine was administered by intraperitoneal injection, then optical and biometric measures were taken and tissue samples collected for assay. Incorporation of [3H] thymidine into cellular DNA was measured in proteinase K digests, following precipitation with trichloroacetic acid. After 5 days, significant amounts of myopia were present in the treated eyes of both form-deprived [-7. 0+/-0.7 Dioptres (D), group mean+/-s.e.m.; P<0.01] and lens-defocused animals (-6.2+/-0.9 D;P<0.01). After 3 days of recovery, 50% of the refractive error had been compensated for, predominantly through shortening of the vitreous chamber in the treated eye. Reduced levels of [3H] thymidine incorporation were observed in sclera from both groups of myopic animals (form-deprived, -34.3+/-9.9%;P<0.05 and lens-defocus, -32.8+/-4.5%;P<0.005). Increased levels of [3H] thymidine incorporation were found in the sclera of recovering animals (+144.0+/-43.2%;P<0.05). The results show that changes in regulation of cell proliferation, during the development of myopia, are visually mediated and inversely related to the direction of change in ocular size. This implies that alterations in the scleral fibroblast population are involved in the modulation of scleral matrix turnover during myopia development.

Animals↗
PubMed2002

Temporal relationship of choroidal blood flow and thickness changes during recovery from form deprivation myopia in chicks.

When form deprived, young chicks rapidly develop axial myopia, from which they recover if the treatment is ceased at a sufficiently early age. The increased axial growth of the eye is accompanied by choroidal thinning and decreased choroidal blood flow (ChBF). In contrast, during the early part of the recovery process, the choroid thickens, shifting the retina towards the new plane of focus. Little information is available about ChBF during recovery from myopia. Because of the possibility that choroidal thickening during recovery from myopia might be driven by an increase in ChBF, the temporal relationship of ChBF and choroidal thickness changes was examined during such recovery. White Leghorn chicks were form deprived from 3 days of age for 2-3 weeks using detachable plastic diffusers. Axial ocular dimensions, including choroidal thickness, were then measured by high frequency A-scan ultrasonography at various times after the diffusers were removed up to 240 hr. ChBF was measured transclerally immediately following the A-scan ultrasonography, using laser Doppler flowmetry. In the chicks measured immediately after diffuser removal, the vitreous chamber was 29.9% longer, the choroid was 6.4% thinner and ChBF was 13.7% less in the treated than in the non-treated control eyes. These changes are characteristic of myopic chick eyes and are reversible in young eyes. Thus, in chicks examined 7 hr after diffuser removal, the ChBF in recovering eyes was now greater than that in control eyes. This ChBF increase peaked about 19 hr after the diffusers were removed. The mean increase in ChBF in treated eyes for the 7-30 hr monitoring period was 187%, relative to control eyes. ChBF in the treated eyes gradually returned to the control level after this time. By contrast to the early, transient increase in ChBF, significant choroidal thickening was not observed in treated eyes until 30 hr after diffuser removal, and continued to increase relative to control eyes over the remainder of the monitoring period, reaching a final mean value of 182%. This study demonstrates, in chick eyes recovering from form deprivation myopia, large increases in ChBF that preceded increases in choroidal thickness and were also more transient than the latter. These results raise the possibility that the increase in ChBF may trigger or even drive the subsequent onset of choroidal expansion, perhaps by facilitating the filling of the choroidal lymphatic lacunae that are well developed in the avian eye.

Animals↗
PubMed1992

Apparent cleavage of the retinal nerve fiber layer in asymptomatic eyes with high myopia.

The appearance of the retinal nerve fiber layer was studied in one eye of 203 normal Asians (59 with high myopia greater than or equal to -5 D, and 144 with emmetropia or hyperopia). "Cleavage" of the retinal nerve fiber layer was observed in 3 of these 59 highly myopic eyes, but there was no significant damage to either the retinal pigment epithelium or the choroid. In contrast, no cleavage was observed in the other 144 emmetropic or hyperopic eyes. High myopia (P = 0.0237, Fisher's exact test) was a significant risk factor for "cleavage" development in the retinal nerve fiber layer. The occurrence of a defect (nerve fiber loss) in the retinal nerve fiber layer in severe myopia (5/59, 8%) was also greater than that in either emmetropia or hyperopia (2/144, 1%; P = 0.0229). These results indicate that subtle changes can occur in the appearance of the retinal nerve fiber layer of the eye in some patients with asymptomatic myopia.

Adult↗