THE WESTERN JOURNAL OF MEDICINE
o
OCTOBER 1992
o
157
*
Because retinal tissue destroyed by infection cannot be regenerated, visual results depend on early diagnosis. Patients should be encouraged to seek immediate ophthalmologic evaluation if they have blurring, visual field defects (blind spots), or multiple floating spots before one or both eyes. With accurate diagnosis and aggressive therapy, many AIDS-related retinal infections can be controlled. Therapies continue to evolve as new drugs become available and effective treatment regimens are identified. GARY N. HOLLAND, MD Los Angeles, California
REFERENCES Hardy WD: Combined ganciclovir and granulocyte-macrophage colony-stimulating factor in the treatment of cytomegalovirus retinitis in AIDS patients: Rationale for and preliminary results from a phase II randomized trial (ACTG 073), In Spector SA (Ed): Ganciclovir Therapy for Cytomegalovirus Infection. New York, NY, Marcel Dekker, 1991, pp 197-213 Holland GN, Engstrom RE Jr, Glasgow BJ, et al: Ocular toxoplasmosis in patients with the acquired immunodeficiency syndrome. Am J Ophthalmol 1988; 106:653-667 Margolis TP, Lowder CY, Holland GN, et al: Varicella-zoster virus retinitis in patients with the acquired immunodeficiency syndrome. Am J Ophthalmol 1991; 112:119-131 Studies of Ocular Complications of AIDS Research Group, in collaboration with the AIDS Clinical Trials Group: Mortality in patients with the acquired immunodeficiency syndrome treated with either foscamet or ganciclovir for cytomegalovirus retinitis. N EngI J Med 1992; 326:213-220
Photorefractive Keratectomy PHOrOREFRAcrIVE KERATECGOMY is a surgical procedure to correct nearsightedness (myopia), farsightedness (hyperopia), and astigmatism. The procedure involves recontouring the anterior surface of the cornea with an excimer laser that uses ultraviolet light (193 nm). Each laser pulse ablates 0.2 to 0.3 4m of corneal tissue, with almost no thermal or other injury produced in the immediately adjacent tissue. The anterior cornea is reshaped by ablating small amounts of tissue from the corneal surface; to flatten the cornea, more tissue is removed centrally than is removed from the periphery, and corneal steepening is achieved by removing little or no tissue centrally and progressively more tissue towards the corneal periphery. The end result is that a central round area of the cornea measuring between 4 and 6 mm in diameter and overlying the pupil is treated, with a maximum depth of ablation of about 10% of corneal thickness. Clinical trials of photorefractive keratectomy are under way in the United States at about 30 centers, and the Food and Drug Administration (FDA) is carefully controlling the number of patients enrolled in these studies. The FDA has determined that fiveyear follow-up will be evaluated before deciding whether or not to approve this procedure for the correction of refractive errors in otherwise healthy eyes. In Europe, Canada, and Asia, where governmental regulation is less restrictive, many lasers are in place and more than 10,000 eyes have been treated. Data from the clinical sites in the United States and reports from abroad show that, in the short run, the procedure appears to be reasonably safe and effective for the correction of low-to-moderate myopias. Beyond 6 diopters, partial or even total regression of the effect is common, resulting in poor predictability of ultimate results. Because 90% of nearsighted Americans have refractive errors of 5 D or less, most patients are candidates who could expect a favorable result if they need any correction beyond spectacles or contact lenses. Clinical follow-up on a large number of patients has been limited to about two years, so long-term safety and stability remain to be determined. In the short term, a superficial
corneal haze is typical after the procedure, but this generally
4
449
decreases in intensity over time. A few patients have measurable decreases in visual acuity or contrast sensitivity for several weeks after the operation; a persistent decrease in visual acuity due to substantial corneal haze occurred in about 2% of patients in one center in Europe. Although most treatments have been performed for myopia, recent studies suggest this laser can be effective also for the treatment of
astigmatism.
Photorefractive keratectomy is to be distinguished from radial keratotomy, a procedure that has been done in the United States since 1978 to correct nearsightedness and astigmatism. Radial keratotomy involves creating incisions deep (90% depth or greater) into the corneal stroma. Four, eight, or more incisions are created, starting in the paracentral cornea and extending radially to the corneal periphery. A large multicenter National Eye Institute-sponsored clinical trial, the Prospective Evaluation of Radial Keratotomy (PERK) Study, was carried out in the early and mid- 1980s to define the safety and effectiveness of this procedure. Visionthreatening complications are rare after radial keratotomy, but predictability is somewhat limited; about two thirds of the patients in the PERK study had adequate vision without spectacles or contact lenses after the operation. In addition to correcting refractive error, the excimer laser is also being used, as an alternative to corneal transplantation, to remove anterior corneal opacities. This procedure, called phototherapeutic keratectomy, has been largely successful to date, and the FDA is currently considering granting approval of the laser for this indication. Should approval be granted, this procedure will provide an outpatient, costsaving surgical alternative to about 10% of the 40,000 patients who undergo corneal transplant each year in the United States. PETER J. McDONNELL, MD Los Angeles,
California
REFERENCES McDonald MB, Frantz JM, Klyce SD, et al: One-year refractive results of central
photorefractive keratectomy for myopia in the nonhuman primate comea. Arch Ophthalmol 1990; 108:40-47 McDonnell PJ, Moreira H, Clapham TN, D'Arcy J, Munnerlyn CR: Photorefractive keratectomy for astigmatism: Initial clinical results. Arch Ophthalmol 1991; 109:1370-1373 Seiler T, Wollensak J: Myopic photorefractive keratectomy with the excimer laser: One-year follow-up. Ophthalmology 1991; 98:1156-1163 Sher NA, Bowers RA, Zabel RW, et al: Clinical use of the 193-nm excimer laser in the treatment of comeal scars. Arch Ophthalmol 1991; 109:491-498
Macular Surgery THE
APPLICATION OF
vitreoretinal
microsurgical techniques
to disorders of the macula, the central retinal visual area, has become one of the most exciting and rapidly developing areas
in ophthalmology. Until recently the primary indication for a macular operation has been the treatment of avascular membranes that may develop on the surface of the macula, descriptively termed "macular pucker." Since the late 1970s the surgical removal of epimacular membranes has improved the vision in about 80% of patients. The development of idiopathic full-thickness macular holes is a common cause of central vision loss, typically affecting older women, and occurring in both eyes in 10% to 20% of patients. A new hypothesis implicated centrifugal traction of the vitreous parallel to the retinal surface at the vitreomacular interface (tangential traction) in the pathoThis genesis of idiopathic full-thickness macular holes.macular of treatment the that the surgical report prompted holes has met with stunning yet widely corroborated success.
o
OCTOBER 1992
o
157
*
Because retinal tissue destroyed by infection cannot be regenerated, visual results depend on early diagnosis. Patients should be encouraged to seek immediate ophthalmologic evaluation if they have blurring, visual field defects (blind spots), or multiple floating spots before one or both eyes. With accurate diagnosis and aggressive therapy, many AIDS-related retinal infections can be controlled. Therapies continue to evolve as new drugs become available and effective treatment regimens are identified. GARY N. HOLLAND, MD Los Angeles, California
REFERENCES Hardy WD: Combined ganciclovir and granulocyte-macrophage colony-stimulating factor in the treatment of cytomegalovirus retinitis in AIDS patients: Rationale for and preliminary results from a phase II randomized trial (ACTG 073), In Spector SA (Ed): Ganciclovir Therapy for Cytomegalovirus Infection. New York, NY, Marcel Dekker, 1991, pp 197-213 Holland GN, Engstrom RE Jr, Glasgow BJ, et al: Ocular toxoplasmosis in patients with the acquired immunodeficiency syndrome. Am J Ophthalmol 1988; 106:653-667 Margolis TP, Lowder CY, Holland GN, et al: Varicella-zoster virus retinitis in patients with the acquired immunodeficiency syndrome. Am J Ophthalmol 1991; 112:119-131 Studies of Ocular Complications of AIDS Research Group, in collaboration with the AIDS Clinical Trials Group: Mortality in patients with the acquired immunodeficiency syndrome treated with either foscamet or ganciclovir for cytomegalovirus retinitis. N EngI J Med 1992; 326:213-220
Photorefractive Keratectomy PHOrOREFRAcrIVE KERATECGOMY is a surgical procedure to correct nearsightedness (myopia), farsightedness (hyperopia), and astigmatism. The procedure involves recontouring the anterior surface of the cornea with an excimer laser that uses ultraviolet light (193 nm). Each laser pulse ablates 0.2 to 0.3 4m of corneal tissue, with almost no thermal or other injury produced in the immediately adjacent tissue. The anterior cornea is reshaped by ablating small amounts of tissue from the corneal surface; to flatten the cornea, more tissue is removed centrally than is removed from the periphery, and corneal steepening is achieved by removing little or no tissue centrally and progressively more tissue towards the corneal periphery. The end result is that a central round area of the cornea measuring between 4 and 6 mm in diameter and overlying the pupil is treated, with a maximum depth of ablation of about 10% of corneal thickness. Clinical trials of photorefractive keratectomy are under way in the United States at about 30 centers, and the Food and Drug Administration (FDA) is carefully controlling the number of patients enrolled in these studies. The FDA has determined that fiveyear follow-up will be evaluated before deciding whether or not to approve this procedure for the correction of refractive errors in otherwise healthy eyes. In Europe, Canada, and Asia, where governmental regulation is less restrictive, many lasers are in place and more than 10,000 eyes have been treated. Data from the clinical sites in the United States and reports from abroad show that, in the short run, the procedure appears to be reasonably safe and effective for the correction of low-to-moderate myopias. Beyond 6 diopters, partial or even total regression of the effect is common, resulting in poor predictability of ultimate results. Because 90% of nearsighted Americans have refractive errors of 5 D or less, most patients are candidates who could expect a favorable result if they need any correction beyond spectacles or contact lenses. Clinical follow-up on a large number of patients has been limited to about two years, so long-term safety and stability remain to be determined. In the short term, a superficial
corneal haze is typical after the procedure, but this generally
4
449
decreases in intensity over time. A few patients have measurable decreases in visual acuity or contrast sensitivity for several weeks after the operation; a persistent decrease in visual acuity due to substantial corneal haze occurred in about 2% of patients in one center in Europe. Although most treatments have been performed for myopia, recent studies suggest this laser can be effective also for the treatment of
astigmatism.
Photorefractive keratectomy is to be distinguished from radial keratotomy, a procedure that has been done in the United States since 1978 to correct nearsightedness and astigmatism. Radial keratotomy involves creating incisions deep (90% depth or greater) into the corneal stroma. Four, eight, or more incisions are created, starting in the paracentral cornea and extending radially to the corneal periphery. A large multicenter National Eye Institute-sponsored clinical trial, the Prospective Evaluation of Radial Keratotomy (PERK) Study, was carried out in the early and mid- 1980s to define the safety and effectiveness of this procedure. Visionthreatening complications are rare after radial keratotomy, but predictability is somewhat limited; about two thirds of the patients in the PERK study had adequate vision without spectacles or contact lenses after the operation. In addition to correcting refractive error, the excimer laser is also being used, as an alternative to corneal transplantation, to remove anterior corneal opacities. This procedure, called phototherapeutic keratectomy, has been largely successful to date, and the FDA is currently considering granting approval of the laser for this indication. Should approval be granted, this procedure will provide an outpatient, costsaving surgical alternative to about 10% of the 40,000 patients who undergo corneal transplant each year in the United States. PETER J. McDONNELL, MD Los Angeles,
California
REFERENCES McDonald MB, Frantz JM, Klyce SD, et al: One-year refractive results of central
photorefractive keratectomy for myopia in the nonhuman primate comea. Arch Ophthalmol 1990; 108:40-47 McDonnell PJ, Moreira H, Clapham TN, D'Arcy J, Munnerlyn CR: Photorefractive keratectomy for astigmatism: Initial clinical results. Arch Ophthalmol 1991; 109:1370-1373 Seiler T, Wollensak J: Myopic photorefractive keratectomy with the excimer laser: One-year follow-up. Ophthalmology 1991; 98:1156-1163 Sher NA, Bowers RA, Zabel RW, et al: Clinical use of the 193-nm excimer laser in the treatment of comeal scars. Arch Ophthalmol 1991; 109:491-498
Macular Surgery THE
APPLICATION OF
vitreoretinal
microsurgical techniques
to disorders of the macula, the central retinal visual area, has become one of the most exciting and rapidly developing areas
in ophthalmology. Until recently the primary indication for a macular operation has been the treatment of avascular membranes that may develop on the surface of the macula, descriptively termed "macular pucker." Since the late 1970s the surgical removal of epimacular membranes has improved the vision in about 80% of patients. The development of idiopathic full-thickness macular holes is a common cause of central vision loss, typically affecting older women, and occurring in both eyes in 10% to 20% of patients. A new hypothesis implicated centrifugal traction of the vitreous parallel to the retinal surface at the vitreomacular interface (tangential traction) in the pathoThis genesis of idiopathic full-thickness macular holes.macular of treatment the that the surgical report prompted holes has met with stunning yet widely corroborated success.
