1 - 24 of 49000+results Greetings from my product. Each component of a web page has aneye-catching visual effect that draws the viewer's attention to it. The eye isincreasingly drawn to a force as it becomes stronger. Other elements appear tobe affected by these forces as well, giving your future movement visualdirection and recommending where you should turn your attention next.
Conflicting datafrequently occurs. Surgeons advise on the best course of action.
Today, to detect diseaseand track progression, glaucoma surgeons mostly use optical coherencetomography, which assesses ocular anatomy, and visual fields, which evaluatefunction. However, they frequently disagree with one another. That begs thequestion of what to do in the event of a dispute.
A multitude offactors, including measuring artifacts, no glaucomatous diseases, abnormaloptic discs, and the nonlinear relationship between changes in structure andfunction as glaucoma advances, can lead to discrepancies between OCT and visualfield data. Here, surgeons with in-depth knowledge of the subject go over someof the possible causes of discrepancies between OCT and visual field data whenexamining glaucoma and what you can do when it does.
There are furthercauses for conflicting data as well. These can be broadly divided into threecategories: problems with technology, problems with ocular structure, andproblems with disease. They consist of:
• Various testingtechniques. Dr. Greenfield says, "For instance, portions of retinaltopography may not immediately correspond to the same regions in visual fieldtesting."
• Subpar OCT scanresults. Dr. Schuman emphasizes the need of having high-quality testing,especially with OCT. The technology won't be able to accurately segment thelayers of the retina if the scan quality isn't high enough, he claims."What Richard Lee, MD, likes to refer to as "red sickness" has alot to do with it. A thin nerve fiber layer receives a misleading reading dueto improper segmentation, which appears red on the report.
• The learning impactin the visual field. Christopher A. Girkin, MD, the head of the department ofophthalmology and vision sciences at Callahan Eye Hospital, University ofAlabama, says, "This potentially has a tremendous impact." Astructure-function discrepancy can result from a few points or even clustersthat imitate a true visual loss.
Non-average eyescan also result in false readings:
• An extremely thin ordense coating of nerve fibers. Even with high-quality testing, Dr. Schumancautions that inconsistent visual field and OCT results might occur when thenerve fiber layer is extremely thick or thin. Assume the patient has a nervefiber layer that is relatively thick but falls below the usual range, he says."What we refer to as the tipping point is a nerve fiber layer thickness ofabout 75 m. Even if a region on the OCT may appear abnormal and be abnormal ifthe mean nerve fiber layer thickness is more than that, it is unlikely that youwill uncover an aberration in the visual field. This may also hold over time;if you're monitoring a patient whose NFL is thicker than 75 m, OCT progressionanalysis may show progression as the NFL thins, but the visual field remainsunaltered. When the thickness of the nerve fiber layer is in the intermediatezone, contradicting findings are less common.
• Variability in thehead of the optic nerve. Dr. Girkin emphasizes that glaucomatous readings canresult from normal fluctuation in the optic nerve head. Larger optic nerveheads may show up abnormally on scans, the author warns. In particular, atilted disc "may appear aberrant when it is only atypical."
He makes the pointthat the optic nerve's appearance during a visual examination might also bedeceptive. The glaucomatous micro disk, according to him, is probably the mosttypical non-artifactual cause of the pseudo-structure-function discrepancy inthe presence of actual disease. If the effect of the scleral canal size on thenerve's appearance isn't understood, even a slight amount of cupping in anoptic nerve head with a short neural canal can indicate a serious injury thatmight go unnoticed.
There may also be adiscrepancy between OCT and visual fields due to no glaucomatous pathology:
• Severe myopia Dr.Schuman notes that the retina in a myope—particularly a high myope—must cover alot more surface area than in an emmetropic eye. "As a result, the retinabecomes thinner overall. As a result, even though the retina is normal, a personwith moderate to high myopia may have a nerve fiber layer or macular measurethat is thinner than the normal thickness range. They might consider that oddmeasurement to be completely normal.
He says,"Unfortunately, those with very myopic eyes are not included in thenormative OCT datasets." "In general, the individuals in suchdatabases have myopia of no more than -6 D, if any. Therefore, a high myopiamay appear aberrant on an OCT but result in a normal visual field. You can endup doubting if the patient has glaucoma.
Function vs.Structure
According to David S.Greenfield, MD, professor, Douglas R. Anderson Chair in Ophthalmology,vice-chair for academic affairs, and co-director of the Glaucoma Service at theBascom Palmer Eye Institute, University of Miami Miller School of Medicine,"disagreement between structure and function measurements in glaucoma isvery common." "Our team examined data from 147 glaucomatous eyes thatwere examined serially and had their retinal nerve fiber layer and maculameasured using OCT once a year for six years. 1 Only 7% of these eyesdemonstrated steady improvement across all three measures.
The most well-knownexplanation for a discrepancy between OCT and visual fields is undoubtedly oneof the most frequent ones: Measurable changes in structure don't alwayscorrespond to measurable changes in function. Dr. Greenfield observes that"ganglion cell axons die and eventually become atrophic as biologicalchanges linked with glaucoma progression occur." "Longitudinalchanges in macular ganglion cell thickness and retinal nerve fiber layerthickness should [in theory] agree with serial changes in visual function usingstandard automated perimetry, but many patients with glaucoma progressiondevelop isolated changes in structural tests without detectable changes invisual function, and vice versa."
According to Philip P.Chen, MD, professor and Grace Hill Chair in the department of ophthalmology atthe University of Washington and chairman of ophthalmology at the UW MedicineEye Institute, "there are situations when one measurement indicatessignals of deteriorating while the other seems stable." "Forinstance, early glaucoma frequently results in a visual field that appearsnormal, but OCT may reveal that structural change is occurring. Harry Quigley'slaboratory demonstrated many years ago that a 5-dB loss observable on automatedperimetry required a 20% loss of ganglion cells.
He continues,"I'd acquire a confirmation OCT and then explain to the patient that eventhough we can't yet find any symptoms, initiating treatment is the prudentthing to do. If the OCT reveals the structural change in early disease.
The same disconnect,but in the opposite direction, occurs as the disease progresses, according toJoel S. Schuman, MD, FACS, head of the NYU Langone Eye Center and ElaineLangone Professor and chief of ophthalmology at NYU Langone Health, NYUGrossman School of Medicine. A patient with more advanced glaucoma would oftenhave both an abnormal visual field and an abnormal OCT if their nerve fiberlayer is extremely thin, say below 55 m. But even when the patient is trulygetting worse, if you're looking for progression, the mean OCT nerve fiberlayer thickness might not be changing. The OCT floor effect is the reason forthat. Since the visual field still has a wider dynamic range at the low end,progress can still be seen there.
Dr. Chen concurs,saying "The OCT RNFL assessment may lose its relevance sooner than visualfield testing does." The measured thinning ends despite ongoing injurybecause of glial scar tissue or other nonfunctional structural tissue in theretinal nerve fiber layer. As a result, especially if you're performing a10-degree test rather than a 24- or 30-degree test, OCT RNFL thickness mayreach a measurement floor while areas on the visual field are still followable.
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