patient will generally notice the visual acuity change earlier than if the nondominant eye is affected. Common presenting complaints involve difficulty reading fine print, reading scrolling lines of print (the “news ticker”) at the bottom of a television picture, or the inability to read clocks at a distance. Other visual acuity–related problems reported by patients include greater difficulty with walking and navigating outdoors, participating in leisure activities such as golf or tennis, and shopping [9].

Testing involving visual impairment showed that distance visual acuity explains a significant proportion of the variance in the total score [10]. Estimation of the impact of visual function through quality of life measures has found visual acuity was the most important predictive variable [11]. Measures of distance visual acuity (along with peripheral visual field) are the principal measures used by legal statutes to determine blindness.

7.2.2Visual Distortion

At present, there are no practical methods to quantify distortion. There are various methods used to try to determine if visual distortion is present. The use of a grid of lines to diagnose macular diseases started in the midnineteenth century [12]. Awareness of the importance of the macula, as well as improved methods of ophthalmic examination and photographic documentation led to increased relevancy of diagnostic tests for macular problems. Eventually Marc Amsler studied grids in detail and developed a set of grids to diagnose ocular diseases [12].

A modified Amsler grid using black lines on a white background instead of white lines on a black background is commonly used as a screening tool [13]. Each version of this test is a suprathreshold test, which may fail to detect relative scotomas [14]. Testing of patients with Amsler grid has shown it to be a suboptimal test [15–18]. In a series of 100 consecutive AMD patients, the grid detected an abnormality in less than 30% tested eyes with CNV [16]. In a study of AMD, the grid detected 34% of CNV eyes and 30% of those with geographic atrophy (GA) [17], while in another study, the grid detected 53% of CNV and 44% of those with GA [18]. At home, testing with Amsler grids has yielded dismal results; in a series of 49 new CNV patients observing an Amsler grid on a regular basis at home, only five noticed the abnormality first during Amsler grid testing [3].

Difficulties in detecting abnormal areas in the Amsler grid test have been attributed to development of a preferred retinal locus away from the scotoma,

questionable fixation in the first place, and perceptual completion, where the brain fills in the missing features [19]. To avoid some of these defects, a macular perimetry methodology based on hyperacuity was developed [17, 18]. This instrument requires the patient to be tested in an instrument, after receiving a tutorial on its use. Once the test begins, it takes about 6 min [21], although the total time for the test is much longer given the need for a tutorial.

In a multicentered clinical trial, preferential hyperacuity perimetry (PHP) showed that 100% of patients with neovascular AMD had a positive test, as did 96% with GA, 70% with intermediate AMD (as diagnosed by the presence of drusen), and 51% with early AMD [18]. Somewhat lower percentages were found in an earlier study [17]. A separate study involving 185 patients with a visual acuity of 20/160 or better with intermediate stage AMD or worse found the test had a sensitivity of 82% for detecting CNV and a specificity of 88% [21]. However, in this study, 63 eyes were removed from analysis despite having taken the test. Of those excluded, 11 had what was considered an unreliable test, although why the test was deemed unreliable was not stated. In addition, 12 eyes with geographic atrophy and 16 others with macular diseases such as pattern dystrophy were excluded [21]. Given the results of previous studies [17, 18], these patients would likely test positive, thus drawing both the reported sensitivity and specificity into question. The large proportion of excluded patients severely limit the generalizability of the study because the results would be difficult to prospectively apply to a group of patients being evaluated in an AMD clinic.

It is difficult to know at what step in the analysis of potential CNV patients PHP testing would be employed efficiently. There does not seem to be a reason to use one in a retinal specialist clinic, because the sensitivity and specificity of the test are easily exceeded by a standard retinal examination, which often includes some combination of ophthalmoscopy, optical coherence tomography (OCT), and fluorescein angiography. As a screening tool in a general clinic, the test is hampered by cost, the time needed to administer the test, and its relatively low sensitivity and specificity.

7.2.3Visual Field Defects

It is common for newly presenting patients with CNV secondary to AMD to describe small defects in their