Foveal contrast sensitivity affected by glaucoma
Foveal contrast sensitivity affected by glaucoma
Could contrast sensitivity testing help detect glaucoma earlier?
A scene as it might be viewed by a person with glaucoma. A new study found that central vision is significantly decreased by the disease
Source: National Eye Institute,
In contrast to conventional wisdom, new research finds that sharp central vision is significantly decreased by glaucoma. The research, published in January in Archives of Ophthalmology, found significantly lower foveal contrast sensitivity in both photopic and mesopic conditions in eyes with glaucoma.
“The maintenance of good visual acuity until late in the disease and the absence of characteristic central visual field defects lead to the belief that the fovea remains unaffected in the early stages of the disease,” reported co-lead study author Hani Levkovitch-Verbin, M.D., Goldschleger Eye Institute, Sheba Medical Center, Tel-Hashomer, Israel. “However, the density of ganglion cells is 10-fold greater at the fovea than the density at 25 degrees eccentricity and 100-fold greater than at the farther periphery, an effect that enables substantial redundancy at the fovea to overcome the early loss in the glaucomatous process, sparing normal foveal function.”
Just because the fovea is still in good working order doesn’t mean it’s not affected. “The CS [contrast sensitivity] testing methods used in this study detected damage in central vision despite good acuity,” Dr. Levkovitch-Verbin noted.
A factual basis for foveal damage
Dr. Levkovitch-Verbin analyzed 35 eyes with glaucoma, age-matched against 23 control eyes with visual acuity of 20/30 or better.
The glaucoma group included eyes with primary open-angle glaucoma (15 eyes), exfoliation glaucoma (six eyes), chronic angle-closure glaucoma (five eyes), normal-tension glaucoma (three eyes), and suspected glaucoma (six eyes).
“Contrast sensitivity was examined by means of two computerized psychophysical tests,” Dr. Levkovitch-Verbin reported. “The transient method included the presentation of a target in a temporal, two-alternative, forced-choice procedure, and the static method involved four forced-choice procedures.”
Using the transient method, researchers found significant differences between the glaucoma and control groups at all special frequencies (SFs) under both photopic and mesopic conditions. Researchers also uncovered significant differences using the static method.
“We used the common SF (6.0 cpd) that was used in both the static and transient methods to compare CS between different glaucoma categories and the controls,” Dr. Levkovitch-Verbin reported. “There was a trend of decreasing CS with increasing severity of glaucoma. Patients with severe glaucoma had significantly decreased CS compared with controls using the static or the transient photopic SF of 6.0 cpd.”
Previous research has indicated that glaucoma affects contrast sensitivity, but this is one of the first reports to indicate an impact on the fovea itself.
“Our results are consistent with previous studies but add psychophysical evidence that foveal functions are affected in glaucoma, thus supporting various histopathological, anatomical, and other psychophysical studies,” Dr. Levkovitch-Verbin reported.
While the clinical impact of the foveal damage may be subtle, it’s definitely there. “Our study, using different modes of foveal CS testing, was able to detect significant differences between patients with glaucoma who have good visual acuity and controls,” Dr. Levkovitch-Verbin concluded.
Further, Dr. Levkovitch-Verbin’s report demonstrated that both the transient and static methods were sufficiently accurate for this type of CS testing. However, the static method appeared to be more efficient.
“In a clinical setting, it is essential for a test to be accurate at diagnosing a disease, and it is advantageous for it to be fast and easy to use,” Dr. Levkovitch-Verbin noted. “The difference in conductance and timing between the tested methods makes the static method easier and faster. Results showed that both methods produce similar trends and are equally accurate, thus implying that the static method may be used safely in the future.”
It’s now time to further research the role of CS testing in screening and monitoring glaucoma, Dr. Levkovitch-Verbin noted.
That’s a good idea, according to John D. Sheppard, M.D., professor of ophthalmology, microbiology, and immunology, Eastern Virginia Medical School, Norfolk.
“It may be a new way to make the diagnosis [of glaucoma], and it may be more sensitive since it involves central vision,” Dr. Sheppard said. “Central vision is the last part of visual capability to go in glaucoma, but it may be the first to go in early glaucoma.”
Such a test might also be embraced by patients. “If the test is sensitive, it would be very useful because patients understand central vision better than peripheral vision,” Dr. Sheppard said. “Most glaucoma patients detest having a visual field test done. A foveal test may be more patient-friendly.”
Editors’ note: Dr. Levkovitch-Verbin has no financial interests related to this study. Dr. Sheppard has no financial interests related to his comments.
Contact information
Levkovitch-Verbin: halevko@hotmail.com
Sheppard: 757-622-2200, docshep@hotmail.com
by Matt Young EyeWorld Contributing Editor
Could contrast sensitivity testing help detect glaucoma earlier?
A scene as it might be viewed by a person with glaucoma. A new study found that central vision is significantly decreased by the disease
Source: National Eye Institute,
In contrast to conventional wisdom, new research finds that sharp central vision is significantly decreased by glaucoma. The research, published in January in Archives of Ophthalmology, found significantly lower foveal contrast sensitivity in both photopic and mesopic conditions in eyes with glaucoma.
“The maintenance of good visual acuity until late in the disease and the absence of characteristic central visual field defects lead to the belief that the fovea remains unaffected in the early stages of the disease,” reported co-lead study author Hani Levkovitch-Verbin, M.D., Goldschleger Eye Institute, Sheba Medical Center, Tel-Hashomer, Israel. “However, the density of ganglion cells is 10-fold greater at the fovea than the density at 25 degrees eccentricity and 100-fold greater than at the farther periphery, an effect that enables substantial redundancy at the fovea to overcome the early loss in the glaucomatous process, sparing normal foveal function.”
Just because the fovea is still in good working order doesn’t mean it’s not affected. “The CS [contrast sensitivity] testing methods used in this study detected damage in central vision despite good acuity,” Dr. Levkovitch-Verbin noted.
A factual basis for foveal damage
Dr. Levkovitch-Verbin analyzed 35 eyes with glaucoma, age-matched against 23 control eyes with visual acuity of 20/30 or better.
The glaucoma group included eyes with primary open-angle glaucoma (15 eyes), exfoliation glaucoma (six eyes), chronic angle-closure glaucoma (five eyes), normal-tension glaucoma (three eyes), and suspected glaucoma (six eyes).
“Contrast sensitivity was examined by means of two computerized psychophysical tests,” Dr. Levkovitch-Verbin reported. “The transient method included the presentation of a target in a temporal, two-alternative, forced-choice procedure, and the static method involved four forced-choice procedures.”
Using the transient method, researchers found significant differences between the glaucoma and control groups at all special frequencies (SFs) under both photopic and mesopic conditions. Researchers also uncovered significant differences using the static method.
“We used the common SF (6.0 cpd) that was used in both the static and transient methods to compare CS between different glaucoma categories and the controls,” Dr. Levkovitch-Verbin reported. “There was a trend of decreasing CS with increasing severity of glaucoma. Patients with severe glaucoma had significantly decreased CS compared with controls using the static or the transient photopic SF of 6.0 cpd.”
Previous research has indicated that glaucoma affects contrast sensitivity, but this is one of the first reports to indicate an impact on the fovea itself.
“Our results are consistent with previous studies but add psychophysical evidence that foveal functions are affected in glaucoma, thus supporting various histopathological, anatomical, and other psychophysical studies,” Dr. Levkovitch-Verbin reported.
While the clinical impact of the foveal damage may be subtle, it’s definitely there. “Our study, using different modes of foveal CS testing, was able to detect significant differences between patients with glaucoma who have good visual acuity and controls,” Dr. Levkovitch-Verbin concluded.
Further, Dr. Levkovitch-Verbin’s report demonstrated that both the transient and static methods were sufficiently accurate for this type of CS testing. However, the static method appeared to be more efficient.
“In a clinical setting, it is essential for a test to be accurate at diagnosing a disease, and it is advantageous for it to be fast and easy to use,” Dr. Levkovitch-Verbin noted. “The difference in conductance and timing between the tested methods makes the static method easier and faster. Results showed that both methods produce similar trends and are equally accurate, thus implying that the static method may be used safely in the future.”
It’s now time to further research the role of CS testing in screening and monitoring glaucoma, Dr. Levkovitch-Verbin noted.
That’s a good idea, according to John D. Sheppard, M.D., professor of ophthalmology, microbiology, and immunology, Eastern Virginia Medical School, Norfolk.
“It may be a new way to make the diagnosis [of glaucoma], and it may be more sensitive since it involves central vision,” Dr. Sheppard said. “Central vision is the last part of visual capability to go in glaucoma, but it may be the first to go in early glaucoma.”
Such a test might also be embraced by patients. “If the test is sensitive, it would be very useful because patients understand central vision better than peripheral vision,” Dr. Sheppard said. “Most glaucoma patients detest having a visual field test done. A foveal test may be more patient-friendly.”
Editors’ note: Dr. Levkovitch-Verbin has no financial interests related to this study. Dr. Sheppard has no financial interests related to his comments.
Contact information
Levkovitch-Verbin: halevko@hotmail.com
Sheppard: 757-622-2200, docshep@hotmail.com
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