Photocoagulation of disciform macular lesions in the ocular histoplasmosis syndrome

MANAGEMENT OF NEOVASCULAR OCULAR HISTOPLASMOSIS: Past and Present

PURPOSE

To review the wide variety of treatment modalities available for choroidal neovascularization secondary to the presumed ocular histoplasmosis syndrome.

METHODS

A literature search was performed to review the multitude of studies conducted to investigate the efficacy and safety of treatment modalities available for choroidal neovascularization secondary to the presumed ocular histoplasmosis syndrome.

RESULTS

Each treatment modality is reviewed, with the studies summarized and presented to support or refute the method of treatment. Two case reports are presented to demonstrate the treatment regimens.

CONCLUSION

This is a comprehensive review of the treatment modalities available to address choroidal neovascularization secondary to the presumed ocular histoplasmosis syndrome. Investigators will continue to strive toward higher efficacy and safety with future innovations in the field.

Ocular histoplasmosis syndrome

The Macular Photocoagulation Study (MPS) is a multi-center clinical trial supported by the National Eye Institute whose purpose is to assess argon laser photocoagulation as a treatment for choroidal neovascular membranes (NVMs) that do not involve the fovea. The MPS documented that in patients with ocular histoplasmosis syndrome argon laser photocoagulation in comparison with no treatment can reduce the risk of severe visual loss from 46 to 13% in the first two years. Accordingly, patients with ocular histoplasmosis and NVMs outside the fovea are advised to undergo prompt treatment with argon laser photocoagulation.

Treatment of macular subretinal neovascularization with the red-light krypton laser in presumed ocular histoplasmosis syndrome

A patient with presumed ocular histoplasmosis and decreased visual acuity in one eye had subretinal neovascularization and retinal hemorrhage in the macular area. Argon-laser treatment to eradicate the subretinal neovascular membrane was contraindicated because of the proximity of the hemorrhagic lesion to the fovea. We used a red-light krypton laser (647 nm) because the light is not absorbed by the hemoglobin in the retinal hemorrhage or by the macular luteal pigment (xanthophyll), and because it is transmitted into the choroid, allowing treatment within the macular zone with less damage to the internal retinal elements. After treatment, the subretinal neovascular membrane completely disappeared and the macular hemorrhage cleared. To the best of our knowledge, this is the first time that a histoplasmic macular subretinal neovascular membrane has been treated with the red-light krypton laser.

The disciform response: an historical perspective

This paper is a survey of the literature in an attempt to provide the basis for our current understanding of the disciform process. Particular emphasis is placed on its pathogenesis and the role of subretinal neovascularization. No two lesions appear exactly alike because of the many stages and combinations possible. Gass (1967) has delineated the broad spectrum with the many different clinical manifestations of this disease process. Verhoeff and Grossman (1937) provided the histopathologic basis for our understanding of the disciform process. The histologic correlation of the clinical "predisciform" state would seem to offer the most promising information for understanding the pathogenesis of the disciform process (Frank et al. 1973; Green and Key 1977; Kornweig 1967; Sarks 1973 and 1976; Small et al. 1976; Zauberman 1970). It is hoped that this literature review has sufficiently emphasized the inherent deficiencies of strictly clinical studies and the need for an appropriate experimental animal model (Ryan 1979).

Follow-up study of presumed ocular histoplasmosis syndrome

One hundred and sixty-two patients with presumed ocular histoplasmosis syndrome were evaluated. New macular scars not present on initial angiogram developed in 9% of eyes. The risk of developing a symptomatic macular lesion in eyes with asymptomatic macular scars was 23%. In eyes with peripapillary scarring, 3.8% developed a peripapillary neovascular membrane. Follow-up was 5.5 years. When the neovascular membrane was touching or outside the foveal avascular zone, the difference between photocoagulated and control eyes was not statistically significant. When only adequately photocoagulated eyes (20) were compared with control eyes (40), the difference was statistically significant (P = 0.04).

Peripapillary neovascular membranes in presumed ocular histoplasmosis

We studied 39 eyes with ocular histoplasmosis and peripapillary neovascular membranes for an average of 12 months. On the basis of clinical findings, 19 were selected for treatment with photocoagulation. Of the treated eyes, 12 (63%) had a visual result of 6/12 (20/40) or better. Of the 20 untreated eyes, six were clinically untreatable and 14 were electively followed up. All but one of the eyes electively followed up had a good visual result. Proximity of the neovascular membrane to the fovea was the most important prognostic factor in determining visual outcome. All eyes with membranes less than 1/4 disk diameter from the fovea lost central vision. All membranes greater than one disk diameter had excellent results. The indications for treatment were prolonged serous or hemorrhagic detachment of the fovea, documented progression of the membrane, and possibly, loss of central vision in the fellow eye from peripapillary disease. Residual and recurrent neovascularization were significant treatment complications.

Results of argon laser photocoagulation in presumed ocular histoplasmosis

We performed argon laser photocoagulation on 31 eyes of 30 patients with presumed ocular histoplasmosis. Nineteen of 25 eyes (76%) with neovascular membranes 0.25 disk diameter or further from the fovea had 6/12 (20/40) or better vision after an average follow-up period of 20 months. Twenty-two of these eyes (88%) had the same or improved visual acuity during this period. When compared to a similar group of untreated eyes, the apparent advantage of photocoagulation in preserving visual acuity was not statistically significant.

Hereditary hemorrhagic macular dystrophy

Four members of a family with dominantly inherited macular dystrophy demonstrated the essential features of hereditary hemorrhagic macular dystrophy. They reported decreased visual acuity in the third decade and eventually developed bilateral disease. Fundus evaluations revealed hemorrhagic and exudative maculopathy associated with pigment atrophy, pigment clumping, and eventual glial scar formation. Early stages of the disease manifested a macular subretinal neovascular network. Photocoagulation treatment of subretinal neovascularization was successful in Case 3, unsuccessful in Case 1. Follow-up of these four brothers lasted over a period of two to 12 years. After they reached the cicatricial phase, the size of the lesion and visual symptoms remained stable. Visual function tests in the early and late stages indicated a local or geographic disease. We differentiated this dystrophy from other hereditary causes for subretinal neovascularization. We recommend early obliteration of the subretinal neovascular network with intense photocoagulation because the outcome of untreated hereditary hemorrhagic macular dystrophy is legal blindness.

Follow-up study in eyes with choroidal neovascularization caused by presumed ocular histoplasmosis

Sixty-four eyes of 60 patients with ocular histoplasmosis, and choroidal neovascularization documented by fluorescein angiography, and not treated with photocoagulation, were followed for an average of 29 months. The primary determinant of visual outcome was the proximity of the neovascular membrane to the fovea. Sixty-four percent of eyes with membranes 0.25 disk diameter or greater from the fovea had a final visual acuity of 6/12 (20/40) or better, and 71% of such eyes maintained or improved initial visual acuity. All eyes with subfoveal neovascularization had a poor visual result. Other factors related to visual prognosis included initial visual acuity, size of the neovascular membrane, size of sensory retinal detachment, and presence of hemorrhage.

Subretinal neovascularization developing after prophylactic argon laser photocoagulation of atrophic macular scars

Two patients who had lost central vision in one eye due to a histoplasmic disciform macular scar received prophylactic argon laser photocoagulation to one or more atrophic lesions (histo spots) in the second macula in an effort to reduce the risk of developing active neovascularization in the second eye. Despite this prophylactic treatment, both patients developed a choroidal neovascular membrane from the photocoagulation scar.

Idiopathic focal subretinal neovascularization

In 20 patients idiopathic focal subretinal neovascularization was characterized by a solitary focus of subretinal neovascularization at or near the fovea, associated with serous or hemorrhagic detachment of the overlying and adjacent sensory retina, or both. Although the lesions resembled the neovascular membrane seen in the presumed ocular histoplasmosis syndrome, none of the other associated characteristic ophthalmoscopic findings, considered essential to make the latter diagnosis, were apparent. In this group of patients, the incidence of positive histoplasmin skin tests was no greater than in the general population. Of the 20 patients, two had bilateral disease. In no case were there any other lesions of any kind in the afflicted or the opposite eye. The disease is self-limited over a variable period of time, but may result in extensive scarring with loss of central vision.

Photocoagulation of active and inactive lesions of presumed ocular histoplasmosis

Argon laser photocoagulation was employed in 27 eyes with presumed ocular histoplasmosis. Thirteen eyes with active macular lesions had stable or improved visual results (72%).