There is also a theory that during eye movement the optic nerve is stretched more in people with larger eyeballs, and this can give rise to glaucoma. Managing glaucoma in patients with myopia is similar to managing glaucoma in other people but can be more challenging. When the pressure is already relatively low to start with it can be difficult to lower the pressure further with standard treatments.
Furthermore surgical management in myopic eyes is challenging — these eyes are anatomically larger and respond to surgery slightly differently, and do not tolerate low pressures hypotony well.
As the incidence of myopia is increasing dramatically in the developed world, the number of cases of glaucoma associated with this will increase too. Attempts to understand the mechanism for the development and progression of myopia with the hope to develop effective interventions are very important, in addition to checking people with myopia to diagnose glaucoma early if it occurs. High Myopia and Glaucoma-like Optic Neuropathy.
APJO ; Ophthalmology ; Glaucoma in Myopia: diagnostic dilemmas. If the values are beyond the normal range of mmHg, this may indicate glaucoma. Your eye care specialists may have a hard time assessing the optic disc of individuals with high myopia. The optic disc is the raised part of your retina where the optic nerve enters. This may also make it difficult to check the optic nerve for any problems.
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Ophthalmic Physiol Opt. Bell GR. Biomechanical considerations of high myopia: part I--physiological characteristics. J Am Optom Assoc. Int J Ophthalmol. Measuring visual field progression in the Early Manifest Glaucoma Trial.
Acta Ophthalmol Scand. Comparison of retinal nerve fiber layer thickness measured by Cirrus HD and Stratus optical coherence tomography. Prevalence and risk factors for myopia in a rural Korean population. Prevalence of myopia in Taiwanese school children: to Ann Acad Med Singapore. Chang RT Singh K. Myopia and glaucoma: diagnostic and therapeutic challenges.
Curr Opin Ophthalmol. Predictors of long-term progression in the early manifest glaucoma trial. Nitta K Sugiyama K Higashide T Does the enlargement of retinal nerve fiber layer defects relate to disc hemorrhage or progressive visual field loss in normal-tension glaucoma?
Risk factors for progression of visual field abnormalities in normal-tension glaucoma. Sung KR. Disc hemorrhage: is that a risk factor or sign of progression?
Nitta K. Disc hemorrhage is a sign of progression in normal-tension glaucoma. Prevalence of primary open-angle glaucoma in central South Korea the Namil study. View Metrics. Functional effects of unilateral open-angle glaucoma on the primary and extrastriate visual cortex. Forgot password? To View More Create an Account or Subscribe Now. You must be signed into an individual account to use this feature. Table 1. View Table. Table 2 presents rates of self-reported glaucoma, vertical cup-to-disc-ratio greater than or equal to 0.
Table 2. The adjusted odds of self-reported glaucoma were not significantly increased in subjects with mild myopia OR 0. The adjusted odds of vertical cup-to-disc ratio greater than or equal to 0. The adjusted odds of having any visual field abnormality were significantly increased in subjects with mild myopia OR 2. Refractive status was also evaluated with respect to the severity of visual field defects.
The Figure presents the proportions of subjects with each category of visual field abnormality amongst subjects with each category of refractive error. The proportion of subjects with moderate and severe visual field defects increased with increasing severity of myopia.
View Original Download Slide. The percentage of subjects with worse visual field defects increases with increasing severity of myopia. This study of a population-based sample of adults in the US aged 40 years and older found an association between myopia and visual field defects, but failed to find an association between myopia and self-reported glaucoma or vertical cup-to-disc ratio. In subjects with mild, moderate, and severe myopia, the odds of having any visual field defect were increased approximately 2-fold, 3-fold, and fold, respectively, compared with subjects with emmetropia.
This pattern suggests an exponential rather than a linear relationship between myopia and visual field defects. In addition, when visual field defects were further categorized into early, moderate, and severe, a pattern emerged suggesting an exponentially increasing proportion of worse visual field defects among subjects with greater myopia.
Our results support findings from previous large population-based studies on myopia and glaucoma. There are several potential explanations for our findings, including the known possibility that myopia can cause visual field defects independent of those found in glaucomatous disease. Myopia is a known risk factor for numerous retinal diseases, and one significant limitation of our study was the lack of data regarding prior history of retinal detachment.
We did, however, repeat our analyses excluding subjects with self-reported macular degeneration and found no substantial difference in our results. Another factor that may have influenced our results and conclusions is that glaucoma is known to be underdiagnosed both in the developed and developing world.
It is certainly possible that some subjects in the NHANES population with glaucomatous disease were unaware of their diagnosis and that their visual field abnormality is a more sensitive indicator of the disease than a self-reported diagnosis. Given that glaucoma screening is more common amongst the elderly and myopia is more common amongst the young, the possibility of a systematic ascertainment error or bias is a strong possibility.
It is noteworthy, however, that the prevalence of glaucoma found in this study is consistent with that reported in previous studies. Under ideal circumstances, all subjects would have received a complete ophthalmologic examination to determine whether or not glaucoma was present. The lack of such testing also leaves open the possibility that some subjects with self-reported glaucoma were in fact glaucoma suspects or ocular hypertensives. However, it has recently been shown that a self-reported diagnosis of glaucoma, while not a highly sensitive ascertainment method, is quite specific amongst those who state that they have the disease.
A less likely misclassification error that might explain our findings would be a scenario where subjects with myopia, who often have optic nerves that are difficult to assess with regard to glaucoma, were told that they did not have glaucoma when in fact they did. Given that such patients are often labeled as glaucoma suspects, and that the self-reporting in NHANES would have likely identified such individuals, such a misclassification is unlikely to have been significant in our study.
Another potential limitation of our study is that vertical cup-to-disc ratio may not be an appropriate surrogate measure of glaucomatous disease. This parameter can be especially difficult to judge in myopic subjects, as they are more likely to have tilted optic nerves that are anatomically abnormal. Lastly, the range of normal optic disc sizes and cup-to-disc ratios vary among ethnicities 37 , 38 and among individuals, so a numerical threshold value for abnormal cup-to-disc ratio may not be a good proxy for assessing glaucoma risk in a study which includes a diverse, nationally representative population.
Another potential bias in our study could be a nondifferential recall and misclassification with regard to glaucoma diagnosis among subjects with various categories of refractive status, which would most likely result in bias toward the null.
In this situation, there would be an underestimation of the strength of the relationship between refractive error and glaucoma diagnosis, a possible explanation for the lack of association between refractive status and self-reported glaucoma in our study. In addition, rather than using standard automated perimetry for visual field testing, NHANES used a FDT N screening protocol with a scoring algorithm for visual field loss that is highly specific One study that compared FDT with standard automated perimetry found the test—retest variability of FDT to be favorable with regard to uniformity over the entire measurement range of the instrument with less variability in the areas of visual field damage.
This stricter algorithm is associated with lower sensitivity but greater specificity in detecting subjects with glaucoma relative to single FDT testing. Using this strict algorithm with a low sensitivity and high specificity, the subjects who were identified as being abnormal were more likely to have glaucomatous visual field loss relative to other algorithms that employ single FDT testing.
We have no reason to believe standard automated perimetry or FDT visual field testing would perform differentially based upon refractive status and, thus, expect this underestimation to be nondifferential and bias our results toward the null.
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