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==Overview==
==Overview==
The results of prior studies need to be read cautiously, however, in light of the
There has been emphasis on glaucoma screening, since usually there is an insidious start of the disease (with no clear start point, [[Open-angle glaucoma|POAG]]), and progression in many cases is slow and unnoticed b the patient. Additionally, there is a recognized stage of the disease in which patients are apparently in a pre-perimetric (before loss of the visual field is present) stage, bringing a challenge to the diagnosis and screening techniques.
current definition of primary open-angle glaucoma (POAG), first promulgated by
 
the American Academy of Ophthalmology (AAO) in 1996: [15] “a multifactorial
The purpose of glaucoma screening tests is to detect those with early stage disease, so that these patients can be treated to reduce the risk of visual field loss.
optic neuropathy” with “a characteristic acquired loss of optic nerve fibers”; the
 
definitive characteristics of glaucoma are based on visual field loss or the
The patients in the pre-perimetric stage of glaucoma, screening tests only evaluate the optic nerve and the NFL.<ref name="Yanoff 2013 p.">{{cite book | last=Yanoff | first=Myron | title=Ophthalmology | publisher=Elsevier/Saunders | publication-place=London | year=2013 | isbn=978-1-4557-3984-4 | page=}}</ref> Optic nerve and retinal nerve fiber layer imaging is used to detect anatomic alterations.The OCT of the optic nerve; the new spectral domain OCT is now being used commonly to screen for loss of the retinal fiber layer in glaucoma. However clinical evaluation is paramount, the increase in vertical cup/disc ratio, the appearance of cup notching or hemorrhages in the disc are taken as a positive screening for glaucoma.<ref name="Yanoff 2013 p.2">{{cite book | last=Yanoff | first=Myron | title=Ophthalmology | publisher=Elsevier/Saunders | publication-place=London | year=2013 | isbn=978-1-4557-3984-4 | page=}}</ref>  It is recommended that stereoscopic pictures of the optic nerve be taken with some regularity, and is considered as the most sensitive early detection method. Caution must be taken due to the fact that there is certain variability between observers, and to the fact that there is no gold standard unique test for the diagnosis of glaucoma, but rather a set of factors that all together lead to the diagnosis.<ref name="Vidas Popović-Suić Novak Lauš Jandroković 2017 pp. 382–390">{{cite journal | last=Vidas | first=S | last2=Popović-Suić | first2=S | last3=Novak Lauš | first3=K | last4=Jandroković | first4=S | last5=Tomić | first5=M | last6=Jukić | first6=T | last7=Kalauz | first7=M | title=Analysis of Ganglion Cell Complex and Retinal Nerve Fiber Layer Thickness in Glaucoma Diagnosis. | journal=Acta clinica Croatica | volume=56 | issue=3 | year=2017 | issn=0353-9466 | pmid=29479903 | doi=10.20471/acc.2017.56.03.04 | pages=382–390}}</ref>
appearance of the disc or retinal NFL. Early or mild glaucoma is characterized
 
by optic nerve abnormalities with normal visual fields. [1] Thus, visual field
Every patient during a visit  to an ophthalmologist is checked for visual acuity, intraocular pressure and cup/disc ratio as part of the optic nerve assessment. If any of those key points raises suspicion such as decreased visual acuity (with no other apparent cause), high or borderline intraocular pressure, or a characteristic glaucomatous vertical optic nerve excavation or disc hemorrhages studies are ordered for a more detailed evaluation of the optic nerve fibers and visual function.<ref name="EyeWiki 2016">{{cite web | title=Glaucoma Screening | website=EyeWiki | date=2016-01-04 | url=http://eyewiki.aao.org/Glaucoma_Screening | access-date=2018-03-05}}</ref>
defects are no longer part of the case definition of glaucoma. Moderate
 
glaucoma is defined as visual field abnormalities in one hemifield, not within 5°
The rate of progression through at multiple time points should be recorded since it fundamental for diagnostic and treatment decisions.
of fixation, whereas severe glaucoma involves visual field abnormalities in both
 
hemifields or loss within 5° of fixation. [1] By using this definition, up to 15 million
persons in the United States could potentially have glaucoma presently, well
above the current estimate by Prevent Blindness America (PBA) of 2.2
million. [16]
PURPOSE OF THE TEST
The purpose of a glaucoma-screening test is to detect and then treat the
disease before it significantly reduces function. The current definition raises four
important questions: (1) What are the likelihood and rate of progressive loss in
persons with early glaucoma (i.e., those with only optic nerve or retinal NFL
loss)? (2) Do currently available treatments slow, stop, or reverse NFL loss and
the consequent loss of visual functioning? (3) At what point does NFL loss
cause functional loss of significance to patients, and what degree of visual field
loss (or any other physiologic or psychometric measure), if any, is required
before patients notice a decrease in visual functioning or quality of life (QOL)?
(4) Is treatment success compromised if the therapy is initiated later in the
disease course?
These essential issues address key concepts that were presupposed in prior
screening efforts – namely, that even early loss adversely affects patients (or
that later loss is harder to control), that treatment effectively reduces the rate of
anatomic and functional loss, and that a sufficiently high number of patients
progress without treatment to make screening for early stages worthwhile.
Estimates of the likelihood of progression from early optic nerve loss to
subsequent additional loss depend on the stage of disease. [17] [18] [19] Among
untreated persons with elevated IOP in the Ocular Hypertension Treatment
Study (OHTS), 9% had progression of optic nerve changes or visual field loss
over 6 years. [19] Risk factors for incremental progression included an increased
cup-to-disc ratio, indicating the possibility of subtle prior glaucomatous damage
(early glaucoma, by definition). For those with manifest glaucoma (including
early visual field loss), the Early Manifest Glaucoma Trial showed that 62% of
untreated patients had worsening of their visual field over 5 years. [20] [21] On
the basis of a meta-analysis of these and other data, Maier and colleagues
concluded that reducing IOP “in patients with ocular hypertension or manifest
glaucoma is beneficial in reducing the risk of visual field loss in the long term.”
[22]
The second issue has been effectively answered by OHTS, EMGT, and other
studies. The EMGT reported that patients with POAG who achieved IOP
reduction generally had subsequent decreased progression of visual field loss.
[20] [21] Although these studies are ongoing, the evidence to date indicates that
treatment can, indeed, effectively retard the rate of vision loss due to glaucoma.
Our understanding of the effect of suboptimal vision on patients’ function has
increased considerably in recent years. For patients with “trouble seeing,” the
QOL impact is commensurate with that of several major systemic illnesses. [23]
[24] [25] Yet glaucoma patients traditionally have been thought not to have
noticeable vision problems until relatively late in the disease course. A
prospective case-control study reported that patients with glaucoma had
significantly lower general functional status than those without glaucoma, [26]
although results of other studies contradict this finding. [27] [28] Notably,
significant visual field loss is associated with reduced activities of daily vision [29]
and elevated rates of automobile accidents. [30] Studies have shown that visual
function and field loss are associated with vision-related QOL. [31] [32] [33]
Hyman et al. assessed the impact of different severities of glaucoma on quality
of life by comparing the mean deviation (MD) on visual field testing with mean
Visual Functioning Questionnaire (VFQ) scores. [32] These investigators found
that under -4.15 MD, there was no significant affect of glaucoma on quality of
life. Patients with MD scores of -4.16 to -19.08 started developing VFQ deficits.
These findings are important because these justify screening efforts to detect
moderate glaucoma (with field loss > 4.15MD). However, further studies are
necessary to justify allocating resources to screen patients with earlier
glaucoma (< 4.15 MD). [32]
The final question is whether early treatment is related to a better outcome over
the course of the disease. A study from Olmstead County, MN, looked at the
rates of glaucoma progression to blindness in patients undergoing filtration
surgery. [34] One of the key findings from this study was that patients who had
more severe visual field loss at presentation had an increased risk of blindness
following surgery. This suggests that intervening earlier in the course of the
disease, prior to the development of significant field loss, is beneficial.
Considering that most patients will demonstrate disease worsening during their
lifetimes despite therapy, if patients are identified earlier through screening, they
may not progress to blindness or significant visual impairment. Thus, the
importance, value, and timing of screening for glaucoma has become more
positive, but it remains an open question, pending additional information on the
functional impact of early visual loss and o
==References==
==References==
{{reflist|2}}
{{reflist|2}}

Revision as of 20:21, 5 March 2018

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Rohan Bir Singh, M.B.B.S.[2]

Overview

There has been emphasis on glaucoma screening, since usually there is an insidious start of the disease (with no clear start point, POAG), and progression in many cases is slow and unnoticed b the patient. Additionally, there is a recognized stage of the disease in which patients are apparently in a pre-perimetric (before loss of the visual field is present) stage, bringing a challenge to the diagnosis and screening techniques.

The purpose of glaucoma screening tests is to detect those with early stage disease, so that these patients can be treated to reduce the risk of visual field loss.

The patients in the pre-perimetric stage of glaucoma, screening tests only evaluate the optic nerve and the NFL.[1] Optic nerve and retinal nerve fiber layer imaging is used to detect anatomic alterations.The OCT of the optic nerve; the new spectral domain OCT is now being used commonly to screen for loss of the retinal fiber layer in glaucoma. However clinical evaluation is paramount, the increase in vertical cup/disc ratio, the appearance of cup notching or hemorrhages in the disc are taken as a positive screening for glaucoma.[2] It is recommended that stereoscopic pictures of the optic nerve be taken with some regularity, and is considered as the most sensitive early detection method. Caution must be taken due to the fact that there is certain variability between observers, and to the fact that there is no gold standard unique test for the diagnosis of glaucoma, but rather a set of factors that all together lead to the diagnosis.[3]

Every patient during a visit to an ophthalmologist is checked for visual acuity, intraocular pressure and cup/disc ratio as part of the optic nerve assessment. If any of those key points raises suspicion such as decreased visual acuity (with no other apparent cause), high or borderline intraocular pressure, or a characteristic glaucomatous vertical optic nerve excavation or disc hemorrhages studies are ordered for a more detailed evaluation of the optic nerve fibers and visual function.[4]

The rate of progression through at multiple time points should be recorded since it fundamental for diagnostic and treatment decisions.

References

  1. ↑ Yanoff, Myron (2013). Ophthalmology. London: Elsevier/Saunders. ISBN 978-1-4557-3984-4.
  2. ↑ Yanoff, Myron (2013). Ophthalmology. London: Elsevier/Saunders. ISBN 978-1-4557-3984-4.
  3. ↑ Vidas, S; Popović-Suić, S; Novak Lauš, K; Jandroković, S; Tomić, M; Jukić, T; Kalauz, M (2017). "Analysis of Ganglion Cell Complex and Retinal Nerve Fiber Layer Thickness in Glaucoma Diagnosis". Acta clinica Croatica. 56 (3): 382–390. doi:10.20471/acc.2017.56.03.04. ISSN 0353-9466. PMID 29479903.
  4. ↑ "Glaucoma Screening". EyeWiki. 2016-01-04. Retrieved 2018-03-05.

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