EPITOMES-OPHTHALMOLOGY

results of cataract extraction with intraocular lens implantation and comparative data on the results of cataract surgical procedures without lens implantation are not available. In general, intraocular lens implantation is indicated when: * Cataract extraction is warranted according to the usual ophthalmic surgical criteria, * The patient is 65 to 70 years of age or older, * The patient is unable to use a contact lens satisfactorily, * There is no specific contraindication to intraocular lens implantation, * The patient desires intraocular lens implantation based on fully informed consent. These guidelines should be considered general principles rather than rigid factors. As experience and scientific information increase, these guidelines may be modified. Moreover, special circumstances may warrant lens implantation in patients at a relatively early age, for example, a cataract in a patient with poor manual dexterity due to arthritis, tremor or paralysis. Contraindications to intraocular lens implantation at this stage of scientific knowledge include the following circumstances: * The patient has only one useful eye, * There is a history of uveitis or retinal detachment, * The patient has rubeosis irides or severe iris atrophy, * The patient has proliferative diabetic retinopathy, * Complications at the time of surgical operation, such as severe hemorrhage or a persistently large pupil make implantation inadvisable. These contraindications, just as the foregoing indications, are general principles. They are not comprehensive, and no combination of indications and contraindications can substitute for professional judgment. Finally, it must be emphasized that many facts regarding intraocular lens manufacture, clinical use and long-term results are not available. Recognizing these gaps in knowledge, intraocular lens implantation is the subject of intense professional attention and scientific investigation. BRADLEY R. STRAATSMA, MD REFERENCES Binkhorst CD: The iridocapsular (two-loop) lens and the irisclip (four-loop) lens in pseudophakia. Trans Am Acad Ophthalmol Otolaryngol 77:589-617, Sep-Oct 1973 Nordlohne ME: The Intraocular Implant Lens. The Hague, Dr. W. Jung B. V. Publishers, 1975 Norton EWD, Ridley H, Roper-Hall MJ, et al: Symposium: Intraocular Lenses. Trans Am Acad Ophthalmol Otolaryngol 81: 64-137, 1976

Current Concepts of Proliferative Diabetic Retinopathy Management DIABETIC RETINOPATHY is one of the leading causes of blindness and visual disability in the United States. It can be classified into nonproliferative and proliferative retinopathy. The proliferative stage of the disease is characterized by new vessel growth on the surface of the retina, or optic nerve. It can also be associated with fibrous tissue proliferation, vitreous hemorrhage and tractional retinal detachment. These changes lead to severe degrees of visual loss. Photocoagulation treatment of proliferative retinopathy has gained widespread acceptance in ophthalmology since 1959. There have been numerous studies of photocoagulation treatment for proliferative diabetic retinopathy in the past 15 years. However, most studies have failed to adhere to the most basic principles of clinical trials, that of random assignment of eyes to treatment or control groups, and comparison of treated and untreated eyes. Moreover, the results of the controlled studies that were done were not valid due to the small number of patients involved. Consequently, results of these studies have been inadequate to evaluate fully the effectiveness of photocoagulation on proliferative diabetic retinopathy. In 1971 the Diabetic Retinopathy Study (DRS) began under the sponsorship of the National Eye Institute. This randomized, controlled clinical trial involved more than 1,700 patients enrolled in 15 medical centers. Each DRS clinic followed standardized procedures and data were collected and analyzed centrally. Patients with visual acuity of 20/100 or better in each eye and evidence of proliferative retinopathy in at least one eye, or severe nonproliferative diabetic retinopathy in both eyes were eligible for enrollment. Patients were treated with either argon laser or xenon arc photocoagulation. One eye was treated and the other eye followed as a control. The selection of the eye for treatment and the modality for treatment was done randomly. The results of the study as of September 1975 showed evidence that photocoagulation treatment as carried out in the DRS (extensive scatter photocoagulation and focal treatment to new vessels) was effective in reducing the incidence of severe visual loss (the occurrence of visual acuity less than 5/200 for two consecutively completed four-month follow-up visits) from 16.3 percent THE WESTERN JOURNAL OF MEDICINE

129

EPITOMES-OPHTHALMOLOGY

in all untreated eyes to 6.4 percent in treated eyes after two years of follow-up. Based on these findings and the evaluation of various sub groups of diabetic retinopathy in the DRS, treatment is now being recommended for untreated eyes if the following conditions are present: * Moderate to severe new vessels on or near the optic disk, * Mild new vessels on or near the optic disk with associated vitreous or preretinal hemorrhage, * Moderate to severe new vessels elsewhere on the surface of the retina if vitreous or preretinal hemorrhage is present. It is apparent that while there is no cure for diabetic retinopathy, photocoagulation treatment applied to certain stages of this disease, according to the DRS protocol, is effective in reducing the incidence of severe visual loss. It should be stressed that the current recommendations for treatment are based on a preliminary report of two years' follow-up data after treatment. Evaluation of all patients in the study will continue and further analysis of the findings will be done to determine the long-term effectiveness of photocoagulation therapy, comparison between xenon arc and argon laser treatment, and the effect of this procedure in eyes with other degrees of retinopathy. S. M. KOPELOW, MD REFERENCES Diabetic Retinopathy Study: Preliminary report on effects of photocoagulation therapy. Am J Ophthalmol 81:383-396, Apr 1976 Diabetic Retinopathy Study: Manual of Operations. Baltimore Diabetic Retinopathy Study Coordinating Center, 1972 Goldberg MF, Fine SL (Eds): Symposium on the Treatment of Diabetic Retinopathy-Publication 1890, US Public Health Service. San Francisco, Govemment Printing Office, 1969, ch 2

Visual Evoked Response VISUAL EVOKED RESPONSE (VER) testing has been one of the most exciting clinical tools to be developed from neurophysiologic research in recent years and has provided us with an objective method of identifying abnormalities of the afferent visual pathways. More than thirty years ago it was shown that regularly repeated flashes of light before the eyes produced evoked responses in the electroencephalogram (EEG) recorded over the occipital cortex. However, in only a small number of people was there a visual evoked response because usually the response was so small it was lost in the random noise of the EEG (amplitude of largest VER waveform is only about 20 130

FEBRUARY 1977 * 126 * 2

microvolts as compared with 500 microvolts for the electroretinogram (ERG). It was not until early in the 1960's that computers were developed that permitted averaging of an evoked response that was time locked to the stimulus. Thus, if a light flash was repeated rapidly 100 times before the eyes and the occipital EEG was recorded by a computer-averager, the common time-locked evoked response was added together to produce a clear wave form while the random EEG noise was slowly approximated to zero. The stimulus often used to produce a VER iS one hundred white flashes of light from a photostimulator. However, other investigators find that a more reproducible response is produced to a rapidly reversing black and white checkerboard pattern. Still other investigators use a straight pattern flash without pattern reversal. Thus one of the problems when reading VER literature is to know what stimulus is used (that is, flash, pattern reversal or pattern flash) and what that laboratory considers normal response. The clinical usefulness of VER testing was heralded by Richey and co-workers (1971), Namerow and Enns (1972), Feinsod and associates (1973), and Halliday and associates (1973). They showed the frequent findings of an abnormally prolonged latency or an abnormal waveform in patients with multiple sclerosis who had no historical or clinical signs of visual system involvement. Often the abnormal VER Will confirm a diagnosis of multiple sclerosis and prevent further expensive and painful neurologic testing. VER has been clinically useful in several other ways. Malingerers who claim blindness in one or both eyes will produce a normal VER objectively refuting the patient's claim. On the other hand patients with posttraumatic subjective visual complaints without objective ophthalmologic signs may have an abnormal VER substantiating their

complaints. VER has been used to monitor optic nerve function during surgical removal of a pituitary adenoma compressing the chiasm. During surgical operation restoration of the normal VER pattern with removal of the tumor allowed the neurosurgeon to know when he had adequately decompressed the chiasm. Postoperatively the patient had a return to normal vision. VER to an appropriate pattern reversal screen 60 in size has been shown to measure macular function and may be used to follow various forms of macular degeneration. VER abnormalities

Current concepts of proliferative diabetic retinopathy management.

EPITOMES-OPHTHALMOLOGY results of cataract extraction with intraocular lens implantation and comparative data on the results of cataract surgical pro...
382KB Sizes 0 Downloads 0 Views