EPITOMES-OPHTHALMOLOGY
Retinitis Pigmentosa RECENT YEARS have seen an increased interest in both basic science and clinical aspects of the genetically diverse group of diseases collectively known as "retinitis pigmentosa." Basic research of current interest centers around genetic studies, the search for chromosomal markers and animal chimeric studies whereby, through intricate microsurgery, retinal tissues from both normal and dystrophic breeds of embryonic mice are joined to produce a hybrid retina. The resulting retina contains both genotypic varieties in one tissue. Further studies include biochemical investigations into visual pigment synthesis, the interaction between retinal pigment epithelium and receptor cells for both normal and dystrophic animals, and retinal enzyme characteristics of selected genetically deficient animals. Clinically, the value of a systematic approach to data accumulation and computer assisted data analysis has become increasingly recognized. Several university centers, including the University of California, Los Angeles, have established registries of retinitis pigmentosa patients. Data have been collected prospectively, but may be reviewed retrospectively at any chosen time. Several interesting points have come to light: * Retinitis pigmentosa starts without intraretinal pigmentary deposition. This may account for the fact that the clinical signs and symptoms are far advanced at the time that the ophthalmoscopic diagnosis is made. Thus, instead of being a rare or atypical form of the disease, the nonpigmented state is universal in the disease's early stages, and correlates with less severe functional loss as measured by visual acuity, dark adaptation function and peripheral visual field constriction. With the passage of time, pigmentation typically appears, making the clinical diagnosis easier. The bone-corpuscle, or cobweb pigmentation is itself of little significance. In some relatively rare instances, intraretinal pigment deposition fails to occur even after 20 or more years of advanced clinical disSuch cases were presumably the ones that Leber referred to as "retinitis pigmentosa sine pigmento." * Accumulated data can be reviewed with respect to the rate of disease progression as a function of the duration of subjective night blindness. X-chromosome linked retinitis pigmentosa appears to be the most severe and rapidly proease.
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gressive form of the disease, with the worst prognosis for vision. Dominantly inherited retinitis pigmentosa may frequently show the mildest functional loss, but variable genetic expressivity accounts for cases of dominant retinitis pigmentosa in which there are severe functional impairment and rapid progression. * Central visual impairment, implying cone involvement, or at least retinal pigment epithelial involvement underlying cone receptors, occurs with greater frequency than previously appreciated. In one series, 48 percent of retinitis pigmentosa patients had Snellen visual acuities of 20/50 or less in one or both eyes at the time of the initial examination. The mean age of the centrally impaired group was only 38 years. Previously held optimism regarding the preservation of central vision until late in life must be reexamined in view of these figures. JEROME T. PEARLMAN, MI) REFERENCES LaVail MM, Mullen RJ: Role of the pigment epithelium in inherited retinal degeneration analyzed with experimental mouse chimeras. Exper Eye Research 23:227-245, Aug 1976 Bok D, Hall MO: The role of the pigment epithelium in the etiology of inherited retinal dystrophy in the rat. J Cell Biol 49: 664-682, Jun 1971 Schmidt S, Berson E, Hayes K: Retinal degeneration in cats fed casein-i: Taurine deficiency. Invest Ophthalmol 15:47-52, Jan 1976 Pearlman JT, Flood TP, Seiff SR: Retinitis pigmentosa without pigment. Am J Ophthalmol 81:417419, Apr 1976
Increasing the Accuracy of Operation for Strabismus ALMOST EVERY CASE of strabismus is some mixture of abnormal restrictions to eye movement, abnormal reflex patterns which control binocular vision and abnormal innervation to the extraocular muscles. While these can be sorted out by special tests in some adults, it is not possible to carry out such investigations in most of our strabismus patients, children. Consequently, operation for strabismus is frequently inaccurate and a reoperation rate of 20 to 50 percent is the result. Ability to adjust or "fine-tune" the surgical result substantially increases the accuracy of results and reduces the incidence of reoperations in difficult cases where ordinary guidelines are lacking. This is carried out by three techniques: The first is to hold the eye in proper alignment position by some "stay" sutures, much as a broken arm is held in position for optimum healing.
Retinitis Pigmentosa RECENT YEARS have seen an increased interest in both basic science and clinical aspects of the genetically diverse group of diseases collectively known as "retinitis pigmentosa." Basic research of current interest centers around genetic studies, the search for chromosomal markers and animal chimeric studies whereby, through intricate microsurgery, retinal tissues from both normal and dystrophic breeds of embryonic mice are joined to produce a hybrid retina. The resulting retina contains both genotypic varieties in one tissue. Further studies include biochemical investigations into visual pigment synthesis, the interaction between retinal pigment epithelium and receptor cells for both normal and dystrophic animals, and retinal enzyme characteristics of selected genetically deficient animals. Clinically, the value of a systematic approach to data accumulation and computer assisted data analysis has become increasingly recognized. Several university centers, including the University of California, Los Angeles, have established registries of retinitis pigmentosa patients. Data have been collected prospectively, but may be reviewed retrospectively at any chosen time. Several interesting points have come to light: * Retinitis pigmentosa starts without intraretinal pigmentary deposition. This may account for the fact that the clinical signs and symptoms are far advanced at the time that the ophthalmoscopic diagnosis is made. Thus, instead of being a rare or atypical form of the disease, the nonpigmented state is universal in the disease's early stages, and correlates with less severe functional loss as measured by visual acuity, dark adaptation function and peripheral visual field constriction. With the passage of time, pigmentation typically appears, making the clinical diagnosis easier. The bone-corpuscle, or cobweb pigmentation is itself of little significance. In some relatively rare instances, intraretinal pigment deposition fails to occur even after 20 or more years of advanced clinical disSuch cases were presumably the ones that Leber referred to as "retinitis pigmentosa sine pigmento." * Accumulated data can be reviewed with respect to the rate of disease progression as a function of the duration of subjective night blindness. X-chromosome linked retinitis pigmentosa appears to be the most severe and rapidly proease.
132
FEBRUARY 1977 * 126 * 2
gressive form of the disease, with the worst prognosis for vision. Dominantly inherited retinitis pigmentosa may frequently show the mildest functional loss, but variable genetic expressivity accounts for cases of dominant retinitis pigmentosa in which there are severe functional impairment and rapid progression. * Central visual impairment, implying cone involvement, or at least retinal pigment epithelial involvement underlying cone receptors, occurs with greater frequency than previously appreciated. In one series, 48 percent of retinitis pigmentosa patients had Snellen visual acuities of 20/50 or less in one or both eyes at the time of the initial examination. The mean age of the centrally impaired group was only 38 years. Previously held optimism regarding the preservation of central vision until late in life must be reexamined in view of these figures. JEROME T. PEARLMAN, MI) REFERENCES LaVail MM, Mullen RJ: Role of the pigment epithelium in inherited retinal degeneration analyzed with experimental mouse chimeras. Exper Eye Research 23:227-245, Aug 1976 Bok D, Hall MO: The role of the pigment epithelium in the etiology of inherited retinal dystrophy in the rat. J Cell Biol 49: 664-682, Jun 1971 Schmidt S, Berson E, Hayes K: Retinal degeneration in cats fed casein-i: Taurine deficiency. Invest Ophthalmol 15:47-52, Jan 1976 Pearlman JT, Flood TP, Seiff SR: Retinitis pigmentosa without pigment. Am J Ophthalmol 81:417419, Apr 1976
Increasing the Accuracy of Operation for Strabismus ALMOST EVERY CASE of strabismus is some mixture of abnormal restrictions to eye movement, abnormal reflex patterns which control binocular vision and abnormal innervation to the extraocular muscles. While these can be sorted out by special tests in some adults, it is not possible to carry out such investigations in most of our strabismus patients, children. Consequently, operation for strabismus is frequently inaccurate and a reoperation rate of 20 to 50 percent is the result. Ability to adjust or "fine-tune" the surgical result substantially increases the accuracy of results and reduces the incidence of reoperations in difficult cases where ordinary guidelines are lacking. This is carried out by three techniques: The first is to hold the eye in proper alignment position by some "stay" sutures, much as a broken arm is held in position for optimum healing.
