Visual losses in early age-related maculopathy

Longitudinal Evaluation of Visual Function Impairments in Early and Intermediate Age-Related Macular Degeneration Patients

Purpose

To evaluate visual function (VF) changes in early and intermediate age-related macular degeneration (eAMD and iAMD) over 24 months.

Design

Prospective, observational natural history study.

Participants

Participants were enrolled at the Duke Eye Center.

Methods

A total of 101 subjects (33 with eAMD, 47 with iAMD, and 21 normal controls) were recruited. Visual function (VF) tests included best-corrected visual acuity (BCVA), low- luminance visual acuity (LLVA), microperimetry (MP), cone contrast tests (CCTs), and dark adaptation (DA). Mixed-effect model repeated measures based on absolute values and change from baseline identified VF tests differentiating AMD from controls and revealing longitudinal VF decline when controlling for covariates (baseline value, age, coronary artery disease, dry eye, and phakic status). Nine AMD genetic risk variants, combinations of these (genetic burden score), reticular pseudodrusen (RPD), and hyperreflective foci (HRF) were tested as predictors of diagnosis and VF performance.

Main Outcome Measures

Longitudinal changes in VF metrics over 24 months.

Results

A total of 70 subjects completed the 2-year visit (22 with eAMD, 31 with iAMD, and 17 controls). Percent reduced threshold (PRT) on MP and CCT red significantly distinguished iAMD versus controls after 12 and 24 months, respectively. Cone contrast test red, PRT, and absolute threshold (AT) on MP showed significant longitudinal deterioration of VF in iAMD versus baseline at 12 months and onward, however, with a reduced rate of worsening. The DA data confirmed a preexisting functional deficit in iAMD at baseline and revealed an increasing proportion of poorly performing iAMD subjects in DA over the study period. None of the other VF measures showed consistent significant changes among the normal, early, and intermediate groups or over time. The genetic burden score was significantly associated with AMD diagnosis (relative risk for iAMD = 1.64, P < 0.01) and DA (r = 0.42, P = 0.00005). Reticular pseudodrusen and HRF showed moderate associations with DA and weak to moderate associations with MP variables.

Conclusions

In iAMD, MP variables, CCT red, and DA revealed slow and nonlinear functional decline over 24 months. A structure-function relationship in eAMD and iAMD stages was demonstrated among HRF, RPD, and DA, possibly modified by genetic risk factors. These structural and functional features represent potential end points for clinical trials in iAMD.

Focal electroretinogram and microperimetry testing of photoreceptor-retinal pigment epithelium function in intermediate age-related macular degeneration

Purpose

To compare the performance of focal electroretinogram (FERG) and fast mesopic microperimetry in evaluating macular function of intermediate age‐related macular degeneration (iAMD) subjects with preserved visual acuity.

Methods

Cross‐sectional, observational study. Participants with drusen >125 µm and VA ≥80 ETDRS letters and age‐ and sex‐comparable healthy subjects were consecutively enrolled in the study. Three photopic FERG recordings of the central 9° of the macula with luminance modulated stimuli flickering at 42.5 Hz and a fast mesopic microperimetry with a custom pattern of 3 central (CS) and 3 paracentral (pCS) stimuli at 1.2° and 6° from fixation were acquired.

Results

Overall, 112 eyes of 77 participants (age 73.0 ± 7.1 years, 47 iAMD eyes) were analysed. Mean FERG amplitude, CS and pCS (all p < 0.05) were lower in the iAMD group. A significant association was observed between FERG amplitude and iAMD (OR 9.58, p < 0.001) in multiple logistic regression analysis. Z‐scores of FERG were lower than microperimetry in iAMD (p = 0.002) but not for healthy participants. AUC of the ROC curve was greater for FERG than microperimetry (0.895 versus 0.644 and 0.675, both p < 0.05).

Conclusion

Focal ERG objectively measures a cumulative response originating from the photoreceptor‐RPE complex of the central 9° of the macula and demonstrated high accuracy in identifying decreased central macular function in iAMD patients with preserved visual acuity, performing better than fast mesopic microperimetry. Focal ERG should be considered a reliable technique for measuring retinal sensitivity of iAMD patients.

Should clinical automated perimetry be considered for routine functional assessment of early/intermediate age-related macular degeneration (AMD)? A systematic review of current literature

Purpose

There is growing interest in functional testing for early/intermediate age‐related macular degeneration (iAMD). However, systematic evaluation of existing clinical functional tests is lacking. This systematic review examines evidence for using clinical automated perimetry in routine assessment of early/iAMD.

Recent findings

PubMed, Web of Science Core Collection, and Embase were searched from inception to October 2020 to answer, is there evidence of visual field defects in early/iAMD, and if so, are early/iAMD visual field defects linked to real‐world patient outcomes? Articles using clinical automated perimetry (commercially accessible and non‐modified devices/protocols) were included. Microperimetry was excluded as this has yet to be incorporated into clinical guidelines. The primary outcome was global visual field indices including mean deviation (MD), pattern standard deviation (PSD), mean sensitivity (MS) and frequency of defects. The secondary outcome was any real‐world patient outcome including quality of life and/or activities of daily living indices. Twenty‐six studies were eligible for inclusion and all studies were observational. There was consistent evidence of worsened MD, PSD, MS and frequency of defects for early/iAMD compared to normal eyes under photopic, low‐photopic and scotopic conditions. Meta‐analysis of studies using standard automated perimetry (SAP) under photopic conditions revealed worsened MD (−1.52dB [−2.27, −0.78 dB]) and MS (−1.47dB [−2, −0.94 dB]) in early/iAMD compared to normal eyes, representing large statistical effect sizes but non‐clinically meaningful reductions. There was insufficient data for meta‐analyses regarding other clinical automated perimetry protocols. Only one study assessed a real‐world patient outcome (on‐road driving performance), with no significant link to visual field outcomes in early/iAMD.

Summary

Significant reduction of global visual field indices is present in early/iAMD, but not clinically meaningful using SAP under photopic conditions. Translational relevance of visual field outcomes to patient outcomes in early/iAMD remains unclear. Thus, SAP under photopic conditions is unlikely to be useful for routine assessment of early/iAMD.

Assessment of age‐related maculopathy using subjective vision tests

This paper reviews non-standard, clinical vision tests that may be used to detect the earliest visual loss in age-related maculopathy (ARM), before fundus changes are detected. We recommend a clinical test battery for all patients aged 60 years and older, comprising low luminance/low contrast (SKILL) VA or low contrast VA, desaturated D-15 colour vision assessment, flicker perimetry, glare recovery and dark adaptation if possible, together with conventional assessments of case history, ophthalmoscopy and high contrast visual acuity (VA) for the detection and diagnosis of ARM. Reading rate is also discussed as a potential indicator of early visual loss. For monitoring the progressive visual loss in age-related macular degeneration (AMD) and determining the requirements for optometric vision rehabilitation, we recommend more conventional clinical vision tests of distance and near visual acuity, reading rate, the effects of varying illumination and a functional central visual field assessment.

Retinal Sensitivity Using Microperimetry in Age-Related Macular Degeneration in an Amish Population

BACKGROUND AND OBJECTIVES

To evaluate retinal sensitivity (RS) by mesopic and scotopic microperimetry (MP-1S) in an elderly Amish population with age-related macular degeneration (AMD).

PATIENTS AND METHODS

Mesopic and scotopic microperimetric testing was performed in 148 eyes of 77 elderly Amish subjects (age > 50 years) from Pennsylvania using a retinal function analyzer. Scotopic testing was performed using a 2.0 log unit neutral density filter following 30 minutes of dark adaptation. All subjects underwent complete ophthalmic examinations, including spectral-domain optical coherence tomography, fundus autofluorescence, infrared reflectance imaging, and flash color fundus photography. Certified graders at Doheny Image Reading Center identified subjects with evidence of AMD as defined by the Beckman classification and quantified drusen volume. RS in subjects with and without AMD was compared. Correlations between RS and drusen burden were analyzed. Ten eyes with incomplete MP-1S exams were excluded from the final analysis.

RESULTS

Among the 138 eyes from 77 subjects included in the final analysis, 42 eyes from 29 subjects had evidence of early or intermediate AMD. The mean age of subjects with AMD was 69.65 years ± 13.81 years versus 63.04 years ± 12.69 years in those without AMD (P = .06). Mesopic RS was 18.8 dB ± 2.1 dB in subjects with AMD and 19.6 dB ± 1.4 dB in those without AMD (P = .07). Scotopic RS was significantly lower (P = .04) in subjects with AMD (15.9 dB ± 2.9 dB) compared with those without AMD (17.3 dB ± 2.4 dB). There was no relationship between mesopic RS and either drusen area (r = -0.06; P = .32) or drusen volume (r = -0.08; P = .30). There was a trend for an association between scotopic RS and both drusen area (r = -0.39; P = .24) and drusen volume (r = -0.36; P = .30).

CONCLUSIONS

In an elderly Amish population, eyes with early or intermediate AMD show a greater reduction in scotopic RS than mesopic RS, suggesting that rod function is more severely affected than cone function. Drusen area and volume measurements better correlated with scotopic RS. [Ophthalmic Surg Lasers Imaging Retina. 2019;50:e236-e241.].

Mesopic Pelli-Robson contrast sensitivity and MP-1 microperimetry in healthy ageing and age-related macular degeneration

PURPOSE

To determine whether decreasing illumination of the Pelli-Robson contrast sensitivity (CS) chart and MP-1 microperimeter to low mesopic conditions is more sensitive to vision changes occurring with healthy ageing and in early and intermediate age-related macular degeneration (AMD) and whether these mesopic tests can differentiate visual function between healthy older participants with and without AMD risk genotypes.

METHODS

Retinal sensitivity was measured in 98 healthy participants (19-85 years) and 21 AMD (AREDS Grade 2/3) patients (73.9 ± 6.5 years) using the Pelli-Robson CS chart and MP-1 microperimeter under low mesopic and standard illumination. The effect of ageing and AMD on retinal sensitivity was estimated using regression analysis. Healthy older participants (>50 years; n = 24) were genotyped for AMD risk genes CFH and/or ARMS2 and retinal sensitivity was compared between genotypes.

RESULTS

With healthy ageing, photopic and mesopic Pelli-Robson CS showed a similar decline (-0.004 log CS/year). In AMD, photopic CS showed a similar decline to healthy ageing (-0.004 log CS/year) while mesopic CS was significantly reduced (-0.007 log CS/year). Both standard and low mesopic microperimetry showed a significant decline (-0.51 and -0.73% contrast/year) with healthy ageing and greater decline (-0.73 and -0.99% contrast/year) with AMD onset. Pelli-Robson CS and microperimetry sensitivity did not differ between AMD risk genotypes in healthy participants.

CONCLUSIONS

Mesopic Pelli-Robson CS detects functional deficits before photopic CS in early and intermediate AMD that can be differentiated from ageing. This test can be easily administered in clinical practice and may provide a means for early detection of retinal dysfunction.

Efficacy of the Amsler Grid Test in Evaluating Glaucomatous Central Visual Field Defects

PURPOSE

To investigate the efficacy of the Amsler grid test in detecting central visual field (VF) defects in glaucoma.

DESIGN

Prospective, cross-sectional study.

PARTICIPANTS

Patients with glaucoma with reliable Humphrey 10-2 Swedish Interactive Threshold Algorithm standard VF on the date of enrollment or within the previous 3 months.

METHODS

Amsler grid tests were performed for each eye and were considered "abnormal" if there was any perceived scotoma with missing or blurry grid lines within the central 10 degrees ("Amsler grid scotoma"). An abnormal 10-2 VF was defined as ≥3 adjacent points at P < 0.01 with at least 1 point at P < 0.005 in the same hemifield on the pattern deviation plot. Sensitivity, specificity, and positive and negative predictive values of the Amsler grid scotoma area were calculated with the 10-2 VF as the clinical reference standard. Among eyes with an abnormal 10-2 VF, regression analyses were performed between the Amsler grid scotoma area and the 10-2 VF parameters (mean deviation [MD], scotoma extent [number of test points with P < 0.01 in total deviation map] and scotoma mean depth [mean sensitivity of test points with P < 0.01 in total deviation map]).

MAIN OUTCOME MEASURES

Sensitivity, specificity, and positive and negative predictive values of the Amsler grid scotoma area.

RESULTS

A total of 106 eyes (53 patients) were included (mean ± standard deviation age, 24-2 MD and 10-2 MD = 66±12 years, -9.61±8.64 decibels [dB] and -9.75±9.00 dB, respectively). Sensitivity, specificity, and positive and negative predictive values of the Amsler grid test were 68%, 92%, 97%, and 46%, respectively. Sensitivity was 40% in eyes with 10-2 MD better than -6 dB, 58% in eyes with 10-2 MD between -12 and -6 dB, and 92% in eyes with 10-2 MD worse than -12 dB. The area under the receiver operating characteristic curve of the Amsler grid scotoma area was 0.810 (95% confidence interval, 0.723-0.880, P < 0.001). The Amsler grid scotoma area had the strongest relationship with 10-2 MD (quadratic R(2)=0.681), followed by 10-2 scotoma extent (quadratic R(2)=0.611) and 10-2 scotoma mean depth (quadratic R(2)=0.299) (all P < 0.001).

CONCLUSIONS

The Amsler grid can be used to screen for moderate to severe central vision loss from glaucoma.

Color vision deficits in intermediate age-related macular degeneration

PURPOSE

To assess the effect of intermediate age-related macular degeneration (AMD) on foveal cone-contrast thresholds.

METHODS

We measured L-M and S-cone-contrast thresholds in subjects with intermediate AMD (n = 10) and age-matched control subjects (n = 10). Monocular, foveal 3-degree Gaussian blobs (600-millisecond raised cosine) were presented at 16 cone ratios throughout L-, M-, and S-cone space, and threshold contours were modeled with probability summation between two independent detection mechanisms. The role that preretinal absorption plays in aging was also evaluated by simulation with FG15 and neutral-density filters.

RESULTS

Aging results in loss of neural sensitivity, not explained by lens changes. On average, intermediate AMD was associated with reduced sensitivity in both color and luminance channels (p < 0.05) that appeared to indicate greater involvement of S-cones. When data were normalized to age-expected values, the changes to cone sensitivity were shown to be consistent (∼200% loss) across L-M, M-L, and S-cone mechanisms. In comparison, the luminance (L + M) mechanism showed relative sparing (155% loss, p < 0.05).

CONCLUSIONS

Eyes with the same phenotype of intermediate AMD can have varying degrees of color threshold loss. Functional markers enhance the clinical definition of disease expression in AMD.

Quantification of visual field loss in age-related macular degeneration

Background

An evaluation of standard automated perimetry (SAP) and short wavelength automated perimetry (SWAP) for the central 10–2 visual field test procedure in patients with age-related macular degeneration (AMD) is presented in order to determine methods of quantifying the central sensitivity loss in patients at various stages of AMD.

Methods

10–2 SAP and SWAP Humphrey visual fields and stereoscopic fundus photographs were collected in 27 eyes of 27 patients with AMD and 22 eyes of 22 normal subjects.

Results

Mean Deviation and Pattern Standard Deviation (PSD) varied significantly with stage of disease in SAP (both p<0.001) and SWAP (both p<0.001), but post hoc analysis revealed overlap of functional values among stages. In SWAP, indices of focal loss were more sensitive to detecting differences in AMD from normal. SWAP defects were greater in depth and area than those in SAP. Central sensitivity (within 1°) changed by −3.9 and −4.9 dB per stage in SAP and SWAP, respectively. Based on defect maps, an AMD Severity Index was derived.

Conclusions

Global indices of focal loss were more sensitive to detecting early stage AMD from normal. The SWAP sensitivity decline with advancing stage of AMD was greater than in SAP. A new AMD Severity Index quantifies visual field defects on a continuous scale. Although not all patients are suitable for SWAP examinations, it is of value as a tool in research studies of visual loss in AMD.

Loss of chromatic sensitivity in AMD and diabetes: a comparative study

BACKGROUND

Abnormalities in rod and cone photoreceptor morphology have been reported in normal aging retinas in the absence of known pathology and have been taken as an indicator of susceptibility to retinal disease. Some loss of visual performance may therefore precede retinal structural changes that can be detected reliably using conventional fundus imaging techniques. Red/green (RG) and yellow/blue (YB) colour discrimination thresholds are sensitive measures of normal retinal function and poor YB discrimination is often taken as an indicator of retinal disease, though it is generally acknowledged that RG loss is also present in most cases of acquired deficiency. Although structural changes in age-related macular degeneration (AMD) and diabetes share some similarities, significant differences remain and this may result in different patterns of RG and YB loss.

AIM

The aim of this study was to quantify and compare the severity of RG and YB loss of chromatic sensitivity in patients with AMD and diabetes.

METHODS

Patients with varying severity of AMD and diabetes and normal subjects of similar age were recruited for the study. RG and YB colour detection thresholds were measured in the two groups of patients and the control group, using the Colour Assessment and Diagnosis (CAD) test.

RESULTS

Each AMD subject investigated showed significant, but unequal loss of YB and RG chromatic sensitivity, with YB discrimination showing the greatest loss. Diabetic subjects also exhibited reduced chromatic sensitivity, but with almost equal and highly correlated RG and YB thresholds (R(2) = 0.99). The severity of colour vision loss measured with the CAD test also correlates well with a clinical classification index of disease progression in AMD, and with the level of hyperglycaemic control in diabetes.

CONCLUSIONS

These findings suggest that accurate measurements of RG and YB colour thresholds can provide a sensitive measure of functional change in diseases of the retina with patterns of loss that differ significantly in AMD and diabetes.

Early age-related macular degeneration impairs tolerance to stimulus degradation

PURPOSE

Pathologic changes of retinal photoreceptors associated with early age-related macular degeneration (AMD) have been well established, but the disease is usually asymptomatic at the early stage, and traditional suprathreshold clinical tests often fail to reveal functional deficiencies. The aim of this study is to demonstrate subtle changes of one suprathreshold visual function in early AMD eyes.

METHODS

The quality of preattentively discriminable texture stimuli was systematically degraded through random deletion of texture checks. The task of the subject was to make a forced choice decision on whether two equally degraded patches contained samples of the same or different types of textures. Tolerance to texture stimulus degradation was measured in young and elderly normal controls and in patients with early AMD.

RESULTS

Subjects were trained to perform the texture discrimination task until they made few errors in discriminating intact textures. Texture discrimination deteriorated with increasing stimulus degradation in all subjects. There was no significant difference between performance of young and elderly normal controls. Early AMD eyes showed significantly less tolerance to stimulus degradation than age-similar normal controls at a range of degradation levels. After controlling for visual acuity, normal subjects still performed significantly better than early AMD eyes at approximately 22% check deletion. There was no significant difference between better eyes of early AMD patients and fellow eyes of late AMD eyes. Performance on the degraded texture task was not correlated with visual acuity. A mild blur of the stimulus had little effect on discrimination of degraded textures.

CONCLUSIONS

Early AMD may not directly affect suprathreshold visual functions when the stimuli are intact and contain redundant information but may manifest itself as a reduction of tolerance to stimulus degradation in the form of localized information loss. The performance of patients with early AMD may be compromised when the visual stimulus contains less redundant information.

Functional deficits in early stage age-related maculopathy

BACKGROUND

It is of interest to examine paracentral functional deficits in early age-related maculopathy (ARM), as histopathological studies indicate that this is where the earliest changes occur. The purpose of this study is to detect the sensory functional deficits at chosen retinal areas around the fovea and at the fovea itself in patients with early age-related maculopathy and to determine the type of functional losses that are more pronounced in early ARM.

METHODS

Ten participants with early ARM and 10 age-matched controls took part. Crowded and uncrowded visual acuity and static and transient contrast sensitivity were measured in the same selected eye of each participant at eight predetermined retinal locations plus the fovea in patients with early ARM and controls. All measurements were made using computer-generated targets.

RESULTS

A significant difference between the controls and subjects with ARM was found in low spatial frequency static contrast sensitivity (p = 0.05) but not for transient contrast sensitivity (p = 0.586). Visual acuity (uncrowded VA and crowded VA) showed a borderline difference (p = 0.072 and p = 0.084, respectively). Compared to controls, there was no evidence of increased contour interaction effects in early ARM (p = 0.595).

CONCLUSION

The subjects with very early ARM showed significant loss of low spatial frequency static contrast sensitivity before the loss of high contrast VA, indicating that static contrast sensitivity may be one of the earliest functional losses in early ARM and this loss was found to extend across the central 10 degrees of the retina.

Macular function surveillance revisited

BACKGROUND

The Amsler grid is a widely used means of evaluating the central 20 degrees diameter visual field. It is a common practice to have patients who are at risk for exudative maculopathy evaluate their macular function daily using the Amsler grid. The goal is to make the patient aware of the earliest symptoms of choroidal neovascularization at a time when therapeutic intervention has the greatest chance for success. There are, however, several important shortcomings of self-monitoring macular function with the Amsler grid, including low sensitivity and low compliance.

METHODS

The history of macular function surveillance is reviewed. The following techniques that are either currently available or under development for home self-monitoring of macular function are discussed: Amsler grid, red Amsler grid, threshold Amsler grid, environmental Amsler techniques, entoptic perimetry, preferential hyperacuity perimetry, and Internet-based interventions.

CONCLUSION

There is compelling evidence that several currently available technologies are superior to the conventional Amsler grid in detecting the earliest symptoms of macular disease. Threshold Amsler grid, entoptic perimetry, and preferential hyperacuity perimetry each have been found to be more sensitive than the conventional Amsler grid in detecting vision disturbances caused by macular disease. Any one of these diagnostic tests could conceivably be utilized by patients at home for self-monitoring of macular function if the technology were suitably deployed for this purpose, such as over the Internet.

Recent progress in macular function self-assessment

BACKGROUND

Patients that are deemed to be at risk for the development of choroidal neovascularization are frequently instructed to self-monitor their vision for symptoms that may signal the presence of choroidal neovascularization. Traditionally, the Amsler grid has been used for this purpose, but recent technological innovations have resulted in a number of potential alternatives that offer important advantages, including greater sensitivity, the ability to differentiate exudative from non-exudative disease, and quantitative analysis of test results.

METHODS

The following technologies that could be employed for patient self-assessment of macular function in a home setting are reviewed: computerized Amsler grid, preferential hyperacuity perimetry, macular mapping test and noise-field campimetry.

CONCLUSIONS

A number of technologies are currently available that could significantly improve the ability of patients at risk for the development of choroidal neovascularization to self-monitor their central visual field.

Parafoveal letter recognition at reduced contrast in normal aging and in patients with risk factors for AMD

BACKGROUND

Patients with early age-related maculopathy (ARM) do not necessarily show obvious morphological signs or functional impairment. Many have good visual acuity, yet complain of decreased visual performance. The aim of this study was to investigate the aging effects on performance of parafoveal letter recognition at reduced contrast, and defects caused by early ARM and normal fellow eyes of patients with unilateral age-related macular degeneration (nfAMD).

METHODS

Testing of the central visual field (8 degrees radius) was performed by the Macular Mapping Test (MMT) using recognition of letters in 40 parafoveal target locations at four contrast levels (5, 10, 25 and 100%). Effects of aging were investigated in 64 healthy subjects aged 23 to 76 years (CTRL). In addition, 39 eyes (minimum visual acuity of 0.63;20/30) from 39 patients with either no visible signs of ARM, while the fellow eye had advanced age-related macular degeneration (nfAMD; n = 12), or early signs of ARM (eARM; n = 27) were examined. Performance was expressed summarily as a "field score" (FS).

RESULTS

Performance in the MMT begins to decline linearly with age in normal subjects from the age of 50 and 54 years on, at 5% and 10% contrast respectively. The differentiation between patients and CTRLs was enhanced if FS at 5% was analyzed along with FS at 10% contrast. In 8/12 patients from group nfAMD and in 18/27 from group eARM, the FS was statistically significantly lower than in the CTRL group in at least one of the lower contrast levels.

CONCLUSION

Using parafoveal test locations, a recognition task and diminished contrast increases the chance of early detection of functional defects due to eARM or nfAMD and can differentiate them from those due to aging alone.

The rod-mediated multifocal electroretinogram in aging and in early age-related maculopathy

PURPOSE

To measure function with the rod-mediated multifocal electroretinogram (mfERG) in younger and older subjects with normal vision and with early age-related maculopathy (ARM).

METHODS

Thirty subjects were studied: 10 healthy subjects with a mean age of 31 years (young group), 10 healthy subjects with a mean age of 71 years (old group), and 10 early ARM subjects with a mean age of 71 years (early ARM group). The influence of cataract was approximated by retesting five subjects of the young group through an 0.3 neutral density filter (ND filter group). We analyzed first-order N1P1-amplitude and P1-implicit time (P1-IT) mfERG responses and correlated them with funduscopic changes as defined by the Age-Related Eye Disease Study (AREDS) group.

RESULTS

Averaged concentric ring P1-ITs were significantly delayed in the old (p = 0.02) and early ARM (p < 0.001) compared with the young group and in the early ARM group compared with the old and ND group (p < or = 0.01). There were no significant differences in N1P1-amplitudes between groups, but there was a significant location effect for all groups with highest mean amplitudes for the most peripheral ring of hexagons (p < 0.01). Significantly delayed overall P1-ITs (p < 0.05) were correlated with progressive funduscopic changes.

CONCLUSIONS

Aging and early ARM affects the rod-mediated mfERG, and there is good correlation with funduscopic changes. Although a lens effect cannot be excluded, a neuronal transmission alteration at the postreceptoral level is suggested.

Functional loss in early age-related maculopathy: the ischaemia postreceptoral hypothesis

We review proposed models and psychophysical and electrophysiological tests performed in many studies for early age-related maculopathy (ARM). We suggest that ischaemia is the trigger for impaired retinal pigment epithelium function causing imbalance of secretion of vascular growth factors, reduced disc degradation capability and reduced metabolic activity and possible inflammatory response. This results in increased deposition of cell debris, such as drusen and thickens Bruch's membrane causing even more ischaemia of the overlying neurosensory retina. The photoreceptors are more resistant to ischaemia given their proximity to the choroid. Furthermore, being 'upstream' from the inner retinal layers, they act as an oxygen sink depriving retinal layers further from the choroid. Postreceptoral cell layers and especially parts of the inner nuclear layer that are located in the watershed zone between two sources of blood supply are preferentially vulnerable to ischaemia. Based on psychophysical and electrophysiological findings we propose that most of the function impairment in early ARM starts postreceptorally.

Visual function and dysfunction in early and late age-related maculopathy

Late age-related maculopathy (ARM) is responsible for the majority of blind registrations in the Western world among persons over 50 years of age. It has devastating effects on quality of life and independence and is becoming a major public health concern. Current treatment options are limited and most aim to slow progression rather than restore vision; therefore, early detection to identify those patients most suitable for these interventions is essential. In this work, we review the literature encompassing the investigation of visual function in ARM in order to highlight those visual function parameters which are affected very early in the disease process. We pay particular attention to measures of acuity, contrast sensitivity (CS), cone function, electrophysiology, visual adaptation, central visual field sensitivity and metamorphopsia. We also consider the impact of bilateral late ARM on visual function as well as the relationship between measures of vision function and self-reported visual functioning. Much interest has centred on the identification of functional changes which may predict progression to neovascular disease; therefore, we outline the longitudinal studies, which to date have reported dark-adaptation time, short-wavelength cone sensitivity, colour-match area effect, dark-adapted foveal sensitivity, foveal flicker sensitivity, slow recovery from glare and slower foveal electroretinogram implicit time as functional risk factors for the development of neovascular disease. Despite progress in this area, we emphasise the need for longitudinal studies designed in light of developments in disease classification and retinal imaging, which would ensure the correct classification of cases and controls, and provide increased understanding of the natural course and progression of the disease and further elucidate the structure-function relationships in this devastating disorder.

Objective functional assessment of age‐related maculopathy: a special application for the multifocal electroretinogram

This paper gives a brief review of methods that assess objectively function in age-related maculopathy (ARM) with emphasis on a newer method, the multifocal electroretinogram (mfERG). In contrast to other electrophysiological tests, such as the full-field and focal electroretinogram (ERG) or the electro-oculogram (EOG), which measure summed responses from various cells from larger areas of the retina, the multifocal electroretinogram maps function locally with a resolution as small as four degrees within the central 30 degrees. By using different paradigms it can measure local cone- and rod-mediated functional impairment at early and late stages of ARM. This improved mapping and higher resolution of the posterior pole compared to other objective methods might lead to earlier detection of ARM. Its usefulness has been demonstrated in documenting the effects of treatment after established laser treatments, such as photodynamic therapy (PDT) and in documenting function after retinal pigment epithelial transplantation, a possible future treatment in late neovascular ARM.

Spare the rod and spoil the eye

This review presents a new unified view of the pathogenesis of three common causes of acquired retinal degenerative disease-diabetic retinopathy, age related macular degeneration, and retinopathy of prematurity. In these three conditions, angiogenesis has a predominant role in the development of sight threatening pathology. Angiogenesis is controlled by among other factors the expression of vascular endothelial growth factor (VEGF), which in turn is regulated by absolute and relative lack of oxygen. The severe pathological manifestations of these three conditions are not part of a general underlying disease process because they are peculiar to the eye, and the profound hypoxia that develops in normal retina during dark adaptation (rod driven hypoxia) is an adequate and elegant additional factor to explain their pathogenesis. A large number of experimental reports support this conclusion, although rod driven anoxia is not generally considered as a causal factor in ocular disease. However, the hypothesis can be critically tested, and also suggests novel methods of treatment and prevention of these conditions that may be simpler and more inexpensive than current therapies and that have a smaller potential for adverse effects.

Colour vision testing as an aid to diagnosis and management of age related maculopathy

AIM

To provide a simple test that detects the onset of age related maculopathy (ARM), and can be used to monitor its severity.

METHODS

Colour contrast sensitivity was measured using computer graphics techniques. Colour thresholds were measured along tritan and protan colour confusion axes in the presence of dynamic luminance noise. Thresholds were determined separately for two sizes of optotypes (6.5 degrees and 1.5 degrees). Natural pupils were used. Normal values for the test have been established.

RESULTS

In all patients with unilateral age related macular degeneration, the smaller optotype was invisible in that eye and in almost all, the larger optotype could not be seen. In the symptomless fellow eyes (with ARM) the larger optotype thresholds were raised. The degree of loss was larger for tritan. For the smaller optotype, protan thresholds were elevated in the majority of patients. Tritan losses were greater and disproportionate to the loss seen with the larger optotype. Every person including those with minimal fundal changes had tritan test results for 1.5 degree optotypes >2 SD above the normal mean. Tritan thresholds varied with the severity of the ARM.

CONCLUSIONS

The test is sensitive, simple and quick to administer, and easy for patients. Therefore, it should be useful in detecting and monitoring elderly people with age related changes in their fundi before irreversible loss of vision has occurred.

Identification of lesion components that influence visual function in age related macular degeneration

AIMS

To explore the relation between lesion composition as assessed by fundus photography and fluorescein angiography with clinical measures of vision in eyes of patients with age related macular degeneration (AMD).

METHODS

A standardised visual function assessment along with colour stereo pair fundus photography was carried out in both eyes of 58 subjects with a confirmed clinical diagnosis of AMD. The size, location, and composition of the macular lesion (blood, exudate, subretinal fluid, pigment, membrane, atrophy, and fibrosis) were measured on the colour photographs using computer assisted image analysis. Of the 58 subjects, 44 also had concurrent fluorescein angiography. Classic and occult choroidal neovascularisation (CNV), blood, blocked fluorescence, fibrosis, geographic atrophy, and the total area of abnormal fluorescence were measured. Multiple linear regression was used to examine the relation between clinical measures of vision and the location and extent of lesion components identified by both colour and fluorescein image capture.

RESULTS

The composition of the macular lesion strongly influenced visual function, with atrophy (p=0.001) and fibrosis (p=0.002) accounting for most of the variation. When the location of the lesion with respect to the fovea was examined, fibrosis within the fovea significantly influenced all clinical measures of vision (p=0.008). The regression model selected the total area of abnormal fluorescence and a composite parameter (a semiquantitative measure of the following characteristics: atrophy, exudates, blood, and fibrosis ) from colour photography (r(2) =0.52) as the variables that explained most of the variation in clinical measures of vision.

CONCLUSIONS

The composition and extent of the macular lesion strongly influences visual function in eyes with AMD. Both colour photography and angiography yielded information, which together explained considerably more of the variation in the clinical measures of vision than either on its own.

A vision specific functional index for use in patients with age related macular degeneration

AIM

To develop and evaluate a new vision specific functional index for use in individuals with age related macular degeneration (AMD).

METHODS

Following consultation with patients with AMD and healthcare professionals, a questionnaire entitled the Daily Living Tasks Dependent on Vision (DLTV) was constructed. It was administered by interview to three separate groups of individuals aged 50 years or older: people with AMD, people with cataract, and people with no visual disability. The relations between DLTV, distance visual acuity, and disorder were examined using Pearson's product moment correlation coefficients, stepwise regression, and principal component analysis.

RESULTS

There was a positive correlation between DLTV items and distance visual acuity in the better eye. Principal component analysis showed that the DLTV has a major single dimension within it. This first principal component accounted for 59% of the variation and correlated well with distance visual acuity in the better eye. Other components were found, one of which correlated with the difference in vision in the two eyes and one which featured in the differentiation of AMD subjects from individuals with cataracts.

CONCLUSIONS

The DLTV provided information on visual impairment in patients over and above that obtained from a measure of visual acuity. It also showed that patients with AMD experience greater difficulty with daily living tasks for any given level of acuity than do patients with cataract.

Questionnaire-based survey on the importance of quality of life measures in ophthalmic practice

PURPOSE

To assess the awareness of the existence of quality of life (QOL) instruments and their perceived relative merit in the management of various eye conditions among ophthalmologists in the United Kingdom.

METHODS

A self-administered questionnaire was circulated among various grades of ophthalmologists attending a major UK ophthalmology conference. The respondents were asked to rank from a list in order of importance various tests of visual function in different ophthalmic conditions.

RESULTS

Distance and near visual acuity were consistently rated high with mean ranks lower than 4.0. Contrast sensitivity and reading speed were consistently rated as low in importance with mean ranks ranging from 4 to 5.8. QOL instruments were deemed to be of some importance in the management of cataract and to a lesser extent in the management of age-related macular degeneration. Only 2 respondents of 36 could name either a generic or a vision-specific QOL instrument.

CONCLUSION

UK ophthalmologists appear to be unfamiliar with QOL measures, despite the fact that in health economics they have become the standard means of assessing the results of health care interventions and of prioritizing funding. Notwithstanding the evolution of a variety of tests for the assessment of visual function, ophthalmologists still rely primarily on distance and, to a lesser extent, near visual acuity to plan their patient management. It is important to identify those tests of visual function that correlate best with the patient's ability to function in the seeing world, and to develop appropriate QOL instruments for use in ophthalmic disorders.

Colour contrast sensitivity in patients with soft drusen, an early stage of ARM

The present institutional study was undertaken in order to determine whether testing of colour contrast sensitivity is valuable in detecting early functional changes in patients at initial stages of age-related maculopathy (ARM). The study included 27 patients with soft drusen as an early sign of ARM and 29 age-matched normals. The area occupied by drusen was determined using a computer program. Colour contrast sensitivity was measured with a computer graphics system. Visual acuity, central visual field (Humphrey Field Analyser) and colour vision (D-15 panel) were normal in both groups. Mean colour contrast sensitivity was significantly lower in patients with early ARM (for the protan axis: p = 0.00019, for the deutan axis: p = 0.000078 and for the tritan axis: p = 0.000096) than in the controls. Interindividual variations were large. There was a tendency towards a bimodal distribution for all three colour axes, most evident for the tritan axis. We found a correlation of the drusen area with the protan and deutan thresholds for the fundus colour photographs r = 0.5 (p < 0.01) and r = 0.4 (p < 0.05), respectively, and with the tritan threshold for the angiograms r = 0.5 (p < 0.05). The findings suggest that colour contrast sensitivity may offer an additional possibility of predicting exudative ARM. Whether the patients with the highest thresholds are those who will be the first to show progression with indications of exudative ARM is not yet known. The patient group will be followed up in order to elucidate this question.

Role of the completion phenomenon in the evaluation of Amsler grid results

PURPOSE

To evaluate the limitations, particularly those related to the perceptual completion phenomenon, of Amsler grid tests in patients with central scotomas caused by macular disorders.

METHODS

We tested 15 affected eyes of 15 patients with macular lesions. In each subject, the central visual field was assessed by using four different types of Amsler grid testing and a tangent screen. Tests were conducted in a random order, and the sequence of tests was repeated once. The distance between the fixation point and the closet border of the plotted scotoma was assessed. For each patient, reproducibility in repeated examinations was evaluated by assessing changes in location of the computed center of the defects and by measuring changes in the position of the center of the scotoma.

RESULTS

The tangent screen was more sensitive than Amsler grids in delineating the borders of the scotoma, and the results were more reproducible. Furthermore, by using a tangent screen, the fixation point was found adjacent to the scotoma.

CONCLUSION

Poor sensitivity and intraindividual variations found with Amsler grid testing are at least partly a result of the perceptual completion phenomenon. This phenomenon proved to be a dynamic and fluctuating process, as the results of two successive Amsler grid tests were not comparable, even when the technique was identical and the time between tests was no more than two to 15 minutes.