Management of choroidal neovascularization within the foveal avascular zone in senile macular degeneration

Combined use of SLO microperimetry and OCT for retinal functional and structural testing

BACKGROUND

This study compared SLO microperimetry scotoma size measurements with the sizes of lesions assessed with OCT in the areas of scotoma.

METHODS

SLO microperimetry was performed on eight patients to assess the location and extent of scotoma areas. An SLO microperimetry master image was used to localize the scotoma areas in the real time OCT fundus image and to center OCT cross scans on the areas of scotoma. The sizes of the morphological changes measured by OCT were compared with the scotoma size measurements.

RESULTS

In each patient, OCT revealed a morphological change located in the area of scotoma. Scotoma sizes ranged from 465 to 3180 microm horizontally and from 570 to 2550 microm vertically. The corresponding lesion sizes ranged from 461 to 2660 microm horizontally and from 523 to 2282 microm vertically. The average difference between SLO and OCT measurements was 2.4% horizontally and 4.9% vertically. There were significant correlations between horizontal and vertical SLO and OCT measurements (Horizontal: R (sq)=0.955, P<0.0001; Vertical: R (sq)=0.898, P=0.0003).

CONCLUSION

SLO microperimetry scotoma size measurements and OCT lesion size measurements are similar to each other. Combining retinal functional testing with morphological testing provides information about the underlying causes of scotoma.

Scanning Laser Ophthalmoscope microperimetry compared with Octopus perimetry in normal subjects

Simultaneously performed ophthalmoscopy and perimetry by microperimetry using the Scanning Laser Ophthalmoscope eliminates some of the classical problems involved in transformation techniques in perimetry such as: optical distortions, unsteady fixation and alignment. Almost all reports published on microperimetry have addressed chorioretinal diseases, with only a few patients in each study. No reports have studied the normal values of this method. To evaluate the reliability of microperimetry, 30 healthy subjects-10 subjects from each of the age group: 40-49 years (male/female ratio: 4/6), 50-59 years (m/f ratio: 5/5) and 60-69 years (m/f ratio: 5/5)-were repeatedly examined with microperimetry and automatic perimetry performed by the Octopus macular program M1. The results of the present study of microperimetry show that the standard deviation of the interindividual variance component was 1.36, that the standard deviation of the intraindividual variance component was 0.94 and that a test result obtained by microperimetry in any of the two locations studied can be related to a test result obtained by Octopus M1 in the same location.

Foveal ablation for subfoveal choroidal neovascularization

Untreated subfoveal choroidal neovascularization (SFCN) often progresses to destroy much central visual function. In this study, laser photocoagulation which included the entire foveal avascular zone was applied to SFCN in the second eye of 13 consecutive patients. Each patient had untreated SFCN in their first eye with visual acuity less than or equal to 20/400. Each second eye had SFCN of recent onset which was less than or equal to 1 disc diameter (DD) in size and visual acuity less than or equal to 20/200. In 10 of 13 (76.9%) treated eyes, SFCN was eliminated for 3 to 30 months. These eyes all retained strikingly better visual fields (Amsler or automated) than their fellow untreated eyes, markedly better subjective vision, and Snellen visual acuities of 20/70 to 20/400. Foveal photocoagulation may be useful in selected cases of SFCN with small neovascular nets and poor visual acuity.

Visual results with low-vision aids in age-related macular degeneration

We reviewed the records of 61 patients with age-related macular degeneration who had an exudative or a dry macular scar and who had received low-vision rehabilitation. Exudative scars resulted from the natural course of sub-retinal new vessels, and dry scars from successful photocoagulation to the new vessels. Low-vision aids consisted of high-power positive lenses. Eyes were divided into three groups according to their distance visual acuity before using low-vision aids: Group 1, 20/100; Group 2, 20/200 to 20/300; and Group 3, 20/400 or poorer. The print size resolution on the Rosenbaum pocket vision screener and power of the low-vision aid in each group were compared for the eyes having exudative scars and those with dry photocoagulation scars. In Groups 2 and 3, eyes with dry macular scars reached a similar resolution of print size but with significantly (P less than .01) lower-power visual aids than eyes with exudative macular scars. In Group 1, eyes with dry macular scars achieved a better print size resolution using significantly (P less than .01) lower-power visual aids than eyes with exudative scars.

Age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of irreversible severe visual loss in the United States in people over 50 years of age. The nonexudative stage includes hard drusen (associated with localized dysfunction of the retinal pigment epithelium [RPE]), soft drusen (associated with diffuse dysfunction of the RPE), and geographic (areolar) atrophy. These fundus changes may predispose the eye to develop the neovascular/exudative stages of AMD. Most patients who develop severe visual loss from AMD have this exudative stage. Treatment for AMD has been shown to be effective for only a small proportion of patients who have a well-defined choroidal neovascular membrane (CNVM) more than 200 microns from the foveal center. Even in successfully treated cases, severe visual loss is postponed only for about 18 months because of the high rate of recurrent CNVMs that extend into the fovea. Thus, despite recent breakthroughs in laser treatment for AMD, most patients who develop the exudative form of AMD will develop central visual impairment. At the present time, the only available treatments for the majority of patients who develop the exudative form of AMD are low vision aids. Investigators are currently evaluating whether treatment is effective for membranes within 200 microns of the foveal center. Future studies need to be directed toward further understanding of the pathogenesis, treatment and prevention of the blinding complications of AMD.

Choroidal neovascularization

Choroidal neovascularization is now considered to be a most important feature in the pathogenesis and treatment of a number of chorioretinal disorders. Since the recognition of its importance, choroidal neovascularization has been described in clinical and pathologic studies of a variety of different ophthalmologic conditions. We have summarized the diseases in which choroidal neovascularization occurs and have reviewed studies on the natural history, clinical findings, and therapy of choroidal neovascularization that provide the basis for the current management of this condition.

Analysis of monochromatic green argon-laser treatment for age-related macular degeneration

A retrospective evaluation of 61 consecutive age-related disciform macular degeneration patients who received green argon-laser photocoagulation was done to evaluate the visual results and to search for characteristics of the presenting lesion that correlated with prognosis. For subretinal new vessels within 200 micron of the foveal avascular center, average pretreatment visual acuity was 20/80 and post-treatment 20/200. Twenty-eight percent improved, 36% stabilized, and 36% had worse acuity at last follow-up. Where new vessels were more than 200 micron from the foveal center, 36% improved, 20% stabilized, and 44% had worse acuity. The average pre- and post-treatment visual acuity for this group was 20/80. Overall, 36% required more than one treatment, and associated retinal vascular obliteration was noted in 31%. Hemorrhage over part of the neovascularization, turbid pigment epithelial detachment, and pigment epithelial detachment in the foveal avascular zone were signs that yielded the worst visual prognosis.

The monochromatic green argon laser in the management of macular disorders

The authors have been using an argon laser photocoagulator equipped with a green filter for about 21/2 years. Compared to the usual blue-green argon laser, the advantage of such an instrument is that green radiation is not absorbed to any significant degree by macular pigment. This ensures a selective action on hemoglobin and pigment epithelium. The green wavelength appears to be extremely useful in the management of macular disorders. The authors report the criteria they follow and the technique they use in the treatment of subretinal neovascular membranes and of macular edema arising from different retinal vascular disorders.

Natural history of choroidal neovascularization in degenerative myopia

We studied 354 eyes with myopic chorioretinal degeneration by means of standard clinical evaluation and fluorescein angiography. The eyes were classified on the basis of the degree of chorioretinal degeneration found in the posterior pole. Lacquer cracks (breaks in Bruch's membrane) were noted in 82% of the 149 eyes with choroidal neovascular membranes (CNM) and in 96% of the 58 eyes with isolated subretinal hemorrhages. These hemorrhages were reabsorbed without adverse visual sequelae in 32 eyes that were followed; in 14 of these eyes that were followed closely, the average time of reabsorption was 6.4 weeks. Seventy eyes with CNM were followed for an average of 40.9 months. In 96% of these eyes the CNM remained stable or regressed, leaving an atrophic, nonexudative scar. This study indicates that CNM in degenerative myopia is usually self-limited.

Subretinal neovascularization in senile macular degeneration

When fluorescein angiograms from 563 patients with senile macular degeneration examined at a large community hospital during a 9.5-year period were retrospectively reviewed, 200 patients were found to have a dry atrophic type of senile macular degeneration, consisting of drusen and retinal pigment epithelial changes. Of the 363 patients with exudative senile macular degeneration, 244 had subretinal neovascular membranes. Seventy-eight membranes were less than 1 disk diameter in size. Most of the large (157 of 224) and small (44 of 78) membranes showed a predilection for the fovea. Only 13 large and six small neovascular membranes were 200 microns or more from the center of the foveal avascular zone.