Mitochondrial alterations of retinal pigment epithelium in age-related macular degeneration

Mitochondrial dysfunctions have been implicated in the pathophysiology of several age-related diseases including age-related macular degeneration (AMD), a progressive neurodegenerative disease affecting primarily the retinal pigment epithelium (RPE). The aims of our electron microscopic and morphometric studies were to reveal qualitative and quantitative alterations of mitochondria in human RPE from AMD and from age- and sex-matched controls. With increasing age a significant decrease in number and area of mitochondria, as well as loss of cristae and matrix density were found in both AMD and control specimens. These decreases were significantly greater in AMD than in normal aging. Alterations of mitochondria were accompanied by proliferation of peroxisomes and lipofuscin granules in both AMD and control specimens, although the difference between groups was significant only for peroxisomes. Unexpectedly, morphometric data showed that the RPE alterations seen in AMD may also develop in normal aging, 10-15 years after appearing in AMD patients. These findings suggest that (i) the severity of mitochondrial and peroxisomal alterations are different between AMD and normal aging, and (ii) the timing of damage to RPE may be critical for the development of AMD. We conclude that besides the well-documented age-related changes in mitochondrial DNA, alterations of mitochondrial membranes may also play a role in the pathogenesis of AMD. These membranes could be a new target for treatment of AMD and other age-related diseases.

Development and pathology of the hyaloid, choroidal and retinal vasculature

During embryogenesis, the development and differentiation of the eye requires the concomitant formation of the neural/glial elements along with a dense vascular network. The adult neural retina is supported by two distinct vascular systems, the proper retinal vessels and the choroidal vessels. The two beds differ not only in their pattern of embryonic differentiation, but also in their function in the adult organism. The retinal vasculature has barrier properties similar to those observed in the brain, whereas the choroidal vessels display a highly fenestrated phenotype. The hyaloid vasculature is a transient embryonic vascular bed which is complete at birth in mammals and regresses contemporaneously with the formation of the retinal vasculature. The dependence of the retina on its blood supply makes it highly vulnerable to any vascular changes and indeed ocular diseases, such as proliferative retinopathy, age-related macular degeneration and the hyperplastic primary vitreous, which are associated with abnormalities of the different vascular beds of the eye. A number of factors have been implicated in developmental and pathological changes in vessel formation and regression, including fibroblast growth factors, platelet-derived endothelial growth factor and vascular endothelial growth factor, among others. The purpose of this review is to describe and discuss new insights into the mechanisms and molecular cues involved in the development of the normal and pathological vascular systems of the eye. The characterization of the molecules and cell-cell interactions involved in the formation, stabilization and regression of new vessels has led to the identification of potential control points for therapeutic intervention.

Comparison of photodynamic therapy and transpupillary thermotherapy for subfoveal choroidal neovascularization due to age-related macular degeneration

BACKGROUND

The purpose of this study was to compare photodynamic therapy (PDT) against subthreshold transpupillary thermotherapy (TTT) with a diode laser for subfoveal choroidal neovascularization secondary to age-related macular degeneration (AMD).

METHODS

Patients with subfoveal choroidal neovascularization secondary to AMD were offered PDT as an initial intervention. If they declined PDT, then TTT was offered.

RESULTS

We evaluated and followed 115 consecutive patients for an average of 1 year. The primary outcome measure was visual acuity, but the interventions were also compared on the basis of lesion size and angiographically determined lesion activity. Baseline comparisons between the 2 treatment groups showed significant differences in pretreatment visual acuity, lesion size, and lesion composition. Univariate analysis of outcomes demonstrated equivalence between the treatment groups in final lesion size, angiographic activity, and visual acuity. Multivariate analysis also demonstrated equivalence between the treatment groups in final visual acuity while controlling for age, pretreatment visual acuity, and lesion category. Predominantly classic lesions were associated with poorer visual outcomes.

INTERPRETATION

The PDT and TTT groups were equivalent in terms of all outcome parameters evaluated.

Progression of visual loss and time between initial assessment and treatment of wet age-related macular degeneration

PURPOSE

To determine whether the time elapsed from initial (referral) diagnosis of neovascular (wet) age-related macular degeneration (AMD) to assessment and treatment by a retinal specialist is associated with visual deterioration in the intervening period.

METHODS

A prospective pilot study of 38 consecutive AMD patients who presented with newly diagnosed subfoveal choroidal neovascularization was conducted in a tertiary care retinal practice. All eligible subjects underwent clinical examination and digital fluorescein angiography at the time of assessment by a retinal specialist. Correlations were performed to assess the association between continuous independent variables and any visual deterioration since initial diagnosis. Multivariate linear regression models with stepwise techniques were used to evaluate any association between visual progression and time elapsed, while controlling for potential clinical covariates.

RESULTS

Of the 38 patients, 32 (84%) met the inclusion and exclusion criteria; no differences in important variables were noted between those included and those excluded. The median time between initial diagnosis and referral assessment and treatment was 28 days (interquartile range=36.5 days); some degree of visual loss developed in 14 (44%) of the subjects. The elapsed time was correlated with progression of visual loss (r=0.50, p=0.003). Multivariate linear regression demonstrated that only time elapsed and lesion type based on fluorescein angiography were associated with progression of visual loss (R2=0.491, F(4,28)=6.744, p=0.001); lesion size, age and sex were not significantly associated with progression of visual loss.

INTERPRETATION

Delay in assessment and treatment of new-onset wet AMD by a retinal specialist is associated with a higher risk of visual loss.

Exposure to Chlamydia pneumoniae infection and progression of age-related macular degeneration

Recent studies have found an association between exposure to Chlamydia pneumoniae infection and risk of age-related macular degeneration (AMD). To assess a potential risk of AMD progression posed by exposure to C. pneumoniae, the authors reexamined Australian residents in 2001-2002 who were aged 51-89 years with early AMD at baseline (1992-1995). Examination included macular photography and an enzyme-linked immunosorbent assay to determine antibody titers to the elementary bodies from C. pneumoniae AR39. AMD progression was assessed quantitatively, using both coarse and fine progression steps following an international classification for AMD grading, and also qualitatively, by side-by-side comparison of baseline and follow-up macular photographs. Serologic data were available for 246 of 254 (97%) subjects. AMD progression was associated with a higher antibody titer. After adjustment for age, smoking, family history of AMD, history of cardiovascular diseases, and source study, the subjects in the upper tertiles of antibody titers were 2.1 (95% confidence interval: 0.92, 4.69), 2.6 (95% confidence interval: 1.24, 5.41), and 3.0 (95% confidence interval: 1.46, 6.37) times more at risk of progression than those in the lowest tertile, using three definitions of progression, respectively. The fact that seroreactivity to C. pneumoniae was independently associated with the risk of AMD progression suggests that C. pneumoniae infection may be an additional risk factor for AMD progression.

Preferred retinal loci and macular scotoma characteristics in patients with age-related macular degeneration

Many patients with macular scotomas due to age-related macular degeneration do not perceive black spots in the visual field where the scotomas are located. Rather, they describe objects as "vanishing," "jumping out of nowhere" or "having blurry parts," or a combination of features. In addition, when the macular scotoma affects the fovea, the visual system uses 1 or more preferred retinal loci (PRLs) as a "pseudofovea" to perform visual tasks. Visual function testing with the scanning laser ophthalmoscope has provided a wealth of information regarding how patients perceive the visual world and how the oculomotor system directs eye movements. This article describes 2 specific functions of the oculomotor system, fixation stability and refixation precision, with data collected from normally sighted people and patients with visual field loss. The implications of the characteristics of PRLs and macular scotomas for clinical testing are discussed.

Cervical sympathectomy causes photoreceptor-specific cell death in the rat retina

Changes in the regulation of the vasculature of the eye may be related to some age-related ocular diseases. We have previously shown that loss of sympathetic innervation, as can normally occur with age, resulted in substantial vascular growth of the choroid. The current study was designed to determine whether changes induced by sympathetic denervation causes significant loss of photoreceptors and increased glial cell reactivity in the retina. Sympathetic denervation was performed followed by immunohistochemistry, TUNEL staining, and protein expression analysis to investigate photoreceptor loss. There was a significant reduction (30%) in photoreceptor numbers in the sympathectomized eye. This loss was due to apoptosis, as there was over a doubling in apoptotic cell numbers after sympathectomy. This loss of photoreceptors in the sympathectomized eye resulted in a significantly reduced width of the outer nuclear layer of the retina when compared to the contralateral eye. Increased glial fibrillary acidic protein (GFAP) staining was also noted after sympathectomy in the ganglion cell layer with streaking toward the bipolar cell layer. These results suggest that loss of sympathetic innervation may cause significant changes to the physiology of the choroid.

Hormone replacement therapy, reproductive factors, and age-related macular degeneration: the Salisbury Eye Evaluation Project

PURPOSE

To evaluate a potential relationship between hormone replacement therapy (HRT), reproductive factors and age-related macular degeneration (AMD).

METHODS

1,458 female participants (age 65-84) from the Salisbury Eye Evaluation study were available for this cross-sectional analysis. AMD outcomes were identified by reading center assessment of fundus photographs.

RESULTS

Women who currently used HRT had a lower adjusted odds of large drusen (> 125 microm) (OR = 0.5, 95% CI 0.2-1.0). Use of HRT was not statistically significantly associated with the prevalence of early AMD or advanced AMD, although the odds ratios were all much less than 1. Women who had had an increased number of births had a greater prevalence of large drusen (test of linear trend, p = 0.03).

CONCLUSIONS

Current use of HRT was associated with a lower odds of large drusen, which may be predictive of advanced AMD. No statistically significant correlations were found between HRT or reproductive factors and early or advanced AMD.

Serum levels of macular carotenoids in relation to age-related maculopathy

BACKGROUND

It has been hypothesized that the macular carotenoids, lutein and zeaxanthin, may protect against age-related maculopathy. We evaluated the association between blood concentrations of lutein (L) and zeaxanthin (Z) and age-related maculopathy (ARM) in a case-control analysis of the baseline examination of the Muenster Ageing and Retina Study (MARS).

METHODS

Of the 1060 participants aged 59-82 years at baseline, 910 (85.9%) with bilateral gradable fundus photographs and complete data for the carotenoids and potential confounders were included. The Rotterdam classification system was used for definition of ARM stages. Multivariate linear regression methods were applied to model the relationship between macular carotenoids and the presence of ARM.

RESULTS

The participants' mean age was 70.9+5.5 years, 59.9% were female, 20.8% had a normal bilateral fundus, and 48.5% showed signs of early ARM (uni- or bilateral) and 30.7% of late ARM (in at least one eye). In study participants with L and/or Z supplementation (15.6%), the median serum levels for L (Z) were approximately 2 times (1.5 times) higher than in subjects with no supplementation. After exclusion of subjects with L and/or Z supplementation, no statistically significant bivariate relationship was observed between the serum levels of L or Z and the presence of ARM. Multivariate regression models, adjusting for age, gender, smoking, body-mass index, and HDL-cholesterol blood levels, produced adjusted mean serum levels of 0.124, 0.112, and 0.131 microg/ml for L and 0.019, 0.020, and 0.022 microg/ml for Z in subjects with normal fundus, early ARM, and late ARM, respectively.

CONCLUSION

In this large study, the serum concentrations of L and Z were not related to the prevalence of ARM. However, the large proportion of study participants taking L and/or Z supplementation may have affected these results.

A common haplotype in the complement regulatory gene factor H (HF1/CFH) predisposes individuals to age-related macular degeneration

Age-related macular degeneration (AMD) is the most frequent cause of irreversible blindness in the elderly in developed countries. Our previous studies implicated activation of complement in the formation of drusen, the hallmark lesion of AMD. Here, we show that factor H (HF1), the major inhibitor of the alternative complement pathway, accumulates within drusen and is synthesized by the retinal pigmented epithelium. Because previous linkage analyses identified chromosome 1q25-32, which harbors the factor H gene (HF1/CFH), as an AMD susceptibility locus, we analyzed HF1 for genetic variation in two independent cohorts comprised of approximately 900 AMD cases and 400 matched controls. We found association of eight common HF1 SNPs with AMD; two common missense variants exhibit highly significant associations (I62V, chi2 = 26.1 and P = 3.2 x 10(-7) and Y402H, chi2 = 54.4 and P = 1.6 x 10(-13)). Haplotype analysis reveals that multiple HF1 variants confer elevated or reduced risk of AMD. One common at-risk haplotype is present at a frequency of 50% in AMD cases and 29% in controls [odds ratio (OR) = 2.46, 95% confidence interval (1.95-3.11)]. Homozygotes for this haplotype account for 24% of cases and 8% of controls [OR = 3.51, 95% confidence interval (2.13-5.78)]. Several protective haplotypes are also identified (OR = 0.44-0.55), further implicating HF1 function in the pathogenetic mechanisms underlying AMD. We propose that genetic variation in a regulator of the alternative complement pathway, when combined with a triggering event, such as infection, underlie a major proportion of AMD in the human population.

An interinstitutional comparative study and validation of computer aided drusen quantification

AIMS

To assess the portability and clinical applicability of a software program based on Photoshop (Adobe Systems Inc, San Jose, CA, USA) for digital drusen quantification.

METHODS

Independent graders from the Digital Fundus Photo Reading Center of Columbia University and King's College Hospital used macular background levelling software to quantify the percentage of drusen in the central and middle Wisconsin subfields. 100 images of consecutive patients with choroidal neovascularisation in one eye and significant drusen in the other eye were analysed to determine suitability, and 10 were chosen for assessment by this software.

RESULTS

Of the 10 images used in the interinstitutional validation, the random effects ANOVA for the central and middle subfields showed a high degree of interobserver agreement. The ICC for interobserver reliability was 0.83 (95% CI: 67 to 95) for the central subfield and 0.84 (95% CI: 69 to 99) for the middle subfield. Overall agreement with the manual grading results was good and the within patient coefficient of variation was about 20% for all the pairwise comparisons between observers and the manual stereo gradings. Of the 100 images used to assess practical applicability of the software, 79 were suitable for semiautomated analysis. 13 had extensive mixed retinal pigment epithelial (RPE) changes limiting drusen identification, five had a significant number of reticular drusen, which are poorly identified by the software, and three had multiple small areas of RPE atrophy, which are difficult to distinguish from drusen.

CONCLUSIONS

The software was successfully used by two institutions demonstrating portability, with good correlation between graders and to the manual stereo grading. Digital drusen quantification was possible in 79% of the images analysed.

Impact of lesion size on photodynamic therapy with verteporfin of predominantly classic lesions in age related macular degeneration

AIM

To determine if photodynamic therapy (PDT) outcomes are related to lesion size in patients with subfoveal predominantly classic choroidal neovascularisation (CNV) secondary to age related macular degeneration (AMD).

METHODS

According to greatest linear dimension (GLD) of the entire lesion determined with fluorescein angiography (FA) patients were divided into two groups. In the first group GLD was <3000 microm and in the second one GLD was 3000-5000 microm. All eyes were treated with standard PDT with the verteporfin protocol. The primary outcome was the proportion of eyes in both groups that did not show significant leakage in FA at the end of follow up. Secondary outcomes were changes in GLD and in best corrected visual acuity (BCVA).

RESULTS

64 patients (mean (SD) age, 76.7 (7.7) years; range 58-95 years) were recruited to participate in the study. All participants in the study completed the follow up time (mean 16.6 months). 24 patients (75%) in the group of smaller lesions (n = 32) compared with 15 patients (46.8%) in the group of larger lesions (n = 32) did not show significant leakage in FA at the end of follow up (p = 0.02). A GLD increase >1000 microm was recorded in nine eyes (28.1%) in the group of smaller lesions and in 16 eyes (50%) in the group of larger lesions (p = 0.07). 22 eyes (68.7%) in the group of smaller lesions compared with 19 eyes (59.3%) in the group of larger lesions lost less than three lines of vision (p = 0.06). Relevant side effects related to verteporfin therapy were not recorded, except for four patients (6.2%) with infusion related back pain.

CONCLUSIONS

These results suggest that lesion size at baseline may be a prognosis factor in PDT in patients with subfoveal predominantly classic CNV secondary to AMD. There are no relevant side effects or safety concerns derived from verteporfin therapy.

Optical coherence tomography in photodynamic therapy for subfoveal choroidal neovascularisation secondary to age related macular degeneration: a cross sectional study

AIMS

To introduce new terminology and validate its reliability for the analysis of optical coherence tomography (OCT) scans, compare clinical detection of cystoid macular oedema (CMO) and subretinal fluid (SRF) with OCT findings, and to study the effect of photodynamic therapy (PDT) on the foveal morphology.

METHODS

Patients with subfoveal, predominantly classic choroidal neovascularisation (CNV) secondary to age related macular degeneration (AMD) undergoing PDT were evaluated with refraction protocol best corrected logMAR visual acuity (VA), slit lamp biomicroscopy, stereoscopic fluorescein angiography (FFA), and OCT. New terminologies introduced to interpret the OCT scans were: neuroretinal foveal thickness (NFT), bilaminar foveal thickness (BFT), outer high reflectivity band thickness (OHRBT), intraretinal fluid (IRF), subretinal fluid (oSRF), and vitreomacular hyaloid attachment (VMHA).

RESULTS

Fifty six eyes of 53 patients were studied. VA was better in eyes with a thinner outer high reflectivity band (OHRBT) (p = 0.02) and BFT (p = 0.05). BFT was less in eyes that had undergone a greater number of PDT treatments (p = 0.04). There was poor agreement between OCT and clinical examination in the detection of CMO and subretinal fluid (kappa = 0.289 and kappa = 0.165 respectively). To validate the interpretation and measurements on OCT, two groups of 20 scans were analysed by two independent observers. There was good agreement between the observers in the detection of IRF, oSRF, and VMHA (p<0.001). Measurements of NFT and BFT had a high reproducibility, and of OHRBT reproducibility was low.

CONCLUSIONS

New terminology has been introduced and tested. OCT appears to be superior to clinical examination and FFA in the detection of CMO. In this study, better vision was associated with a thinner OHRBT and/or the absence of SRF giving insight into the biological effect of PDT.

Intravitreal triamcinolone in the treatment of serous pigment epithelial detachment and occult choroidal neovascularization secondary to age-related macular degeneration

PURPOSE

To report two cases of occult choroidal neovascularization (CNV) and serous pigment epithelial detachment (PED) treated with intravitreal triamcinolone (IVT) injections.

METHODS

Interventional case reports.

RESULTS

Both patients showed an increase in visual acuity and a complete flattening of the PED at 10 months (Case 1) and 4 months (Case 2) after IVT injections. No complications or adverse effects are reported.

CONCLUSIONS

Future studies should be designed to investigate if IVT can effectively influence the clinical and functional outcome of eyes with serous PED and occult CNV secondary to age-related macular degeneration, for which at the moment no treatment has been shown to be effective.

[Carboxyamido-triazole inhibits substeps of choroidal neovascularization on retinal pigment epithelial cells and choroidal endothelial cells in vitro]

BACKGROUND

Retinal pigment epithelial cells (RPE cells) and choroidal endothelial cells (CECs) are important cell types in the process of choroidal neovascularization in exudative age-related macular degeneration (AMD). In this study, we evaluated the antiproliferative and antimigratory abilities of carboxyamido-triazole (CAI), a drug modulating calcium-dependent signal transduction on RPE cells and CECs.

METHODS

Human fetal RPE cells and bovine CECs were exposed to CAI in a concentration range of 0.1 to 10 microM. Cell proliferation was stimulated with 10% serum or 10 ng/ml bFGF. The effect of CAIs on cell proliferation was estimated. Furthermore, we evaluated CAI's effects on CEC and RPE cell migration induced by fibronectin.

RESULTS

CAI had a stronger inhibitory effect on serum-induced CEC proliferation than on RPE cell proliferation. A much stronger effect was seen on the proliferation of bFGF-stimulated RPE cells and CECs. Furthermore, the fibronectin-stimulated migration of RPE cells and CECs was inhibited by CAI. In this assay, a stronger inhibitory effect was seen on RPE cells than on CECs. CONCLUSION; CAI inhibits important substeps of choroidal neovascularization on RPR cells and CECs. Therefore, CAI may be of value for the treatment of choroidal neovascularization in exudative AMD.

Future pharmacological treatment options for nonexudative and exudative age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of irreversible vision loss in the industrialised world. Within the past decade, researchers have introduced many promising prevention and treatment options in an attempt to minimise the central vision loss imparted from AMD. Based on large-scale, randomised, prospective, placebo-controlled trials, a specially formulated combination of the antioxidants vitamin C, vitamin E, beta-carotene, copper and zinc is the only proven means of AMD prophylaxis. Thermal laser photocoagulation and photodynamic therapy with verteporfin are the only standard treatment options. However, efficacy is limited and treatment is only applicable to a minority of AMD patients. Thus, alternative pharmacological interventions are in all phases of clinical development. Researchers are guardedly optimistic that these advances may change the entire approach to AMD management in the near future. This review article will detail the currently accepted treatment options, as well as describe several of the more promising investigational pharmacological approaches to AMD.

Visual acuity and structural findings in old age-related macular degeneration

BACKGROUND

Although exudative age-related macular degeneration (AMD) leads to a substantial visual loss in most patients there is still significant variation in the end- stage visual acuity level. We analysed lesions in eyes with long-standing AMD in order to find contributing factors for this variation.

METHODS

Sixty-one out of 121 patients examined for exudative AMD and still alive 4.8-9.2 (mean 6.8) years after the acute phase were re-examined. The lesion size, area of subretinal fibrosis, geographic atrophy, presence of a persistent exudative process, and shortest distance to normal looking retina were measured from digital fundus photographs taken at the re-examination and correlated with visual acuity.

RESULTS

Lesion size, the presence of a continuing exudative process, or subretinal fibrosis were independent predictors for poor vision. Better vision in the other eye was connected with poor vision in the affected study eye.

CONCLUSIONS

In addition to lesion size, the presence of a continuing exudative process and subretinal fibrosis also have deleterious effects on long-term visual acuity after exudative AMD.

Drusen classification in bilateral drusen and fellow eye of exudative age-related macular degeneration

AIM

To assess the value of the modified international classification system in screening high-risk patients with bilateral age-related maculopathy (ARM) from those with lower risk characteristics.

METHODS

In total, 164 digital images of 106 patients with either bilateral ARM (group A) or the fellow eyes of unilateral exudative age-related macular degeneration (AMD) (Group B) were included. Patients with no signs of ARM in both eyes or those with bilateral late AMD were excluded. The images were randomised and then graded by two masked ophthalmologists based on the modified International Classification of ARM.

RESULTS

The interobserver consistency between the two graders was high with a Kappa value of 0.82 (SE 0.34, P<0.0001). There were no significant differences in the distribution of the stages of ARM between the two subgroups. Stage 3 was the most common stage in each group for both graders followed by stage 2a in the bilateral drusen group. Stages 1a, 2a and 2b were equally the next common stage in the fellow eye of chordial neovascularisation group.

CONCLUSION

A screening system based on clinical characteristics would be of value in risk prediction in a clinical setting. Type of Drusen alone, as identified by the modified International grading system, may not be reliably predictive in screening for patients who are at high risk of developing choroidal neovascularisation.

Decreased thickness and integrity of the macular elastic layer of Bruch's membrane correspond to the distribution of lesions associated with age-related macular degeneration

Age-related macular degeneration (AMD) is a leading cause of blindness in the elderly. In its severest form, choroidal neovessels breach the macular Bruch's membrane, an extracellular matrix compartment comprised of elastin and collagen laminae, and grow into the retina. We sought to determine whether structural properties of the elastic lamina (EL) correspond to the region of the macula that is predilected toward degeneration in AMD. Morphometric assessment of the macular and extramacular regions of 121 human donor eyes, with and without AMD, revealed a statistically significant difference in both the integrity (P < 0.0001) and thickness (P < 0.0001) of the EL between the macular and extramacular regions in donors of all ages. The EL was three to six times thinner and two to five times less abundant in the macula than in the periphery. The integrity of the macular EL was significantly lower in donors with early-stage AMD (P = 0.028), active choroidal neovascularization (P = 0.020), and disciform scars (P = 0.003), as compared to unaffected, age-matched controls. EL thickness was significantly lower only in individuals with disciform scars (P = 0.008). The largest gaps in macular EL integrity were significantly larger in all categories of AMD (each P < 0.0001), as compared to controls. EL integrity, thickness, and gap length in donors with geographic atrophy did not differ from those of controls. These structural properties of the macular EL correspond spatially to the distribution of macular lesions associated with AMD and may help to explain why the macula is more susceptible to degenerative events that occur in this disease.

Results 28 months following transpupillary thermotherapy for classic and occult choroidal neovascularization in patients with age-related macular degeneration

BACKGROUND AND OBJECTIVE

To report the outcome of patients 28 months following treatment with transpupillary thermotherapy (TTT) for classic and occult choroidal neovascularization (CNV) secondary to age-related macular degeneration.

PATIENTS AND METHODS

A nonrandomized pilot trial of 36 eyes of 33 patients was performed. Eyes with angiographically defined CNV, 11 predominantly classical and 25 predominantly occult, were treated with large spot diode laser (810 nm) TTT for 1 minute, the end point being no or minimal visible change. Outcome was assessed with best-corrected LogMAR visual acuity, clinical examination, and fluorescein angiography.

RESULTS

Patients were observed for a mean of 28.7 months (range, 18 to 40 months). The mean change in LogMAR visual acuity for predominantly classic membranes was -1.91 (standard deviation [SD] = 4.3) and 5 of 11 (45.5%) eyes had a loss of 3 or more LogMAR lines. Predominantly classic membranes were closed in 9 of 11 eyes and stabilized in 2 of 11 eyes. The mean change in LogMAR visual acuity for predominantly occult membranes was -1.48 (SD = 6.3) and 10 of 25 (40%) patients had a loss of 3 lines or more. Predominantly occult CNV was stabilized in 25 of 25 cases, and recurrence developed in 2 of 25 cases; one of the latter developed classic CNV.

CONCLUSIONS

The medium-term results for patients treated with TTT for both occult and classic CNV show good stability, with little visual loss and few recurrences. These data confirm the original findings of this study.

[RPE transplantation: the challenges and the future]

Transplantation of RPE cells represents a potential therapeutic intervention for various retinal degenerations including complex, multifactorial age-related macular degeneration (AMD). Prerequisite for a successful RPE transplantation is the isolation of suitable cells, which must establish themselves in the host eye to develop functionality similar to that of healthy RPE cells in vivo. Autologous cells can be harvested from the peripheral retina. Ex vivo gene manipulation offers the possibility that even a dysfunctional donor RPE cell can be restored to perform a required specific function in the retina which may in turn help prevent or slow down the degenerative process in the host eye. The problem of cultured RPE cells is that they lose many of their normal phenotypic characteristics, which also leads to a reduction of their functional capacity. Currently highly "stressed" RPE cells are transplanted, whether fresh or cultured, which may not establish their normal in vivo functions. The generation of a genetically engineered cell line with all the functions of a healthy RPE cell and the use of retinal stem cells represent alternative and promising approaches for the future.

[Reading performance in the scar stage of age-related macular degeneration]

PURPOSE

To evaluate reading performance in patients with age-related macular degeneration (AMD).

SUBJECTS AND METHODS

Six normal subjects over 50 years of age and 40 patients with AMD were evaluated. Near visual acuity, critical print size, and maximum reading speed were tested to compare the data from normal subjects with those from AMD patients. Scanning laser ophthalmoscope (SLO) microperimetry was performed to observe fixation in AMD patients.

RESULTS

The mean critical print size for normal subjects was 0.15 logarithm of the minimum angle of resolution (log MAR) and the mean maximum reading speed was 307 characters/min. There was a plateau area in reading function where reading speed did not rise and stayed constant even though print size increased. The mean critical print size for AMD patients was 0.97 log MAR, and the mean maximum reading speed was 140 characters/min. The critical print size and maximum reading speed differed significantly between normal and AMD subjects. Eleven of the 40 patients with AMD did not have the character size and reading speed relationship, which means they manifested a plateau as seen in normal subjects. Eight of the 11 patients did not show stable fixation with SLO microperimetry.

CONCLUSIONS

The reading performance of AMD patients was remarkably impaired, especially in those with poorer visual function and no fixation.

Impaired RPE survival on aged submacular human Bruch's membrane

Resurfacing of diseased or iatrogenically damaged Bruch's membrane with healthy retinal pigment epithelium (RPE) has been proposed as adjunctive treatment for age-related macular degeneration (AMD). The purpose of this study was to determine whether cultured fetal human RPE cells can attach and differentiate on aged submacular human Bruch's membrane. Bruch's membrane was debrided to expose native RPE basement membrane, the superficial inner collagenous layer directly below the RPE basement membrane, or the deep inner collagenous layer. These are three surfaces that transplanted RPE cells will encounter in situ. Approximately 3146 cultured fetal RPE cells mm(-2) were seeded onto these three surfaces and grown in organ culture for 1, 7, or 14 days. Explants were bisected and examined histologically or analyzed with a scanning electron microscope. RPE nuclear density was measured on stained sections. Morphology and cell density were compared to cells seeded onto bovine corneal endothelial cell-extracellular matrix (BCE-ECM). In situ submacular RPE nuclear density was also measured in tissue sections of donor eyes ranging from 18 weeks gestation to 88 years of age to determine the effect of age on RPE density. Compared to cells seeded onto BCE-ECM at similar density, RPE cell coverage and cellular morphology on aged submacular human Bruch's membrane was poor at all time points. In contrast to cells on BCE-ECM, RPE cell density on Bruch's membrane decreased with time. In general, cell morphology on all three Bruch's membrane surfaces worsened by day-7 compared to day-1. Although some cells were more pigmented on RPE basement membrane and the deep inner collagenous layer at day-7, poor cellular morphology indicated the remaining cells were not well differentiated. At day-14, the cells were uniform and cuboidal on BCE-ECM, with cell density similar to that at day-7 and similar to in situ density of young donors (<age 30 years). The morphology of cells on Bruch's membrane was variable, and the nuclear density declined over time. A Bruch's membrane explant from a donor with large soft drusen showed the poorest resurfacing at day-7 in organ culture. These data indicate that aged submacular human Bruch's membrane does not support transplanted RPE survival and differentiation readily. The formation of localized RPE defects, cell death, and worsening cellular morphology on aged Bruch's membrane indicates that modification of Bruch's membrane may be necessary to prevent graft failure in AMD patients receiving RPE transplants.