But, more importantly he says, in a study of 35 patients who all complained of blurred vision, he found that often different patients with the same visual acuity will each score very differently on the contrast-sensitivity test (Brain 1976;99:695-710). Thirty-one of the 35 patients in that study had a “profound” change in contrast sensitivity without corresponding changes in conventionally measured visual acuity.
“Our findings established that there is no unique correspondence of visual acuity to contrast sensitivity,” he writes. And, that is why he hopes con-trast-sensitivity testing could be used as an aid in differential diagnosis.
Other studies have shown that certain specific visual dysfunctions have a characteristic contrast sensitivity curve. Bodis-Wollner says that the curve is specific for those visual dysfunctions regardless of the visual acuity (provided they can see well enough to be measured). For example, patients with glaucomatous optic neuropathy have less than normal contrast sensitivity for grating patterns with larger stripes (Am J Ophthalmol 1979;88:205-211).
Patients with macular disease have subnormal contrast sensitivity for grating patterns with narrower stripes, often before visual acuity is affected (Acta Ophthalmol 1977;55:507-514); and some patients with cerebral lesions have been found to have poor contrast sensitivity in the middle regions. Very cheap drugs at your disposal – buy ampicillin antibiotics buy now to get best deals at best pharmacy.