Aspects of Lyme Borreliosis is a comprehensive scientific presentation of virtually all aspects of lyme borreliosis. It starts with a concise history of lyme borreliosis and its causative agent, Borrelia burgdorferi. The morphological and biological characteristics of B. burgdorferi are presented, followed by outlines on the ecology and histopathology of LB.The various aspects of the clinical manifestations of LB are systematically dealt with, starting with a clinical overview. A special chapter covers the microbiological diagnosis. After a presentation on the susceptibility of B. burgdorferi in vitro and in animals against a great variety of antibiotics, a thorough discussion on the treatment of LB including criticalremarks follows. The book closes with a chapter on the epidemiology of LB.

The 4th International Visual Field Symposium of the International Perimetric Society, was held on the 13-16 April 1980 in Bristol, England, at the occasion of the 6th Congress of the European Society of Ophthalmology. The main themes of the symposium were comparison of classical perimetry with visual evoked response, comparison of classical perimetry with special psychophysi cal methods, and optic nerve pathology. Understandably many papers dealt with computer assisted perimetry. This rapidly developing subgroup of peri metry may radically change the future of our method of examination. New instruments were introduced, new and exciting software was proposed and the results of comparative investigations reported. There have been many confusing statements in the literature on the relative value of perimetry and the registration of visual evoked responses. Several reports attempted to bring some clarity in this issue. There is reason for further comparative research. A number of papers dealt with special psychophysical methods, i.e. methods not using the simply monocular differential threshold. The old critical fusion frequency received new attention. Fundusperimetry was used for testing spatial summation. Acuity perimetry, binocular perimetry etc. showed that there exist many possibilities for examining visual function. At present it is not clear to us what exactly the place of these methods is in our diagnostic armament. However it is quite clear that some of them are promising and may lead to a further differentiation of perimetric methods."

The XVlIIth ISCEV symposium was organized by the Netherlands Ophthal- mic Research Institute and took place May 18-22, 1980, at the Wilhelmina Gasthuis in Amsterdam. The invited speakers and the theme "Electrophysio- logy and pathology of the visual pathways" were selected by a programme committee consisting of G.H.M. van lith, D. van Norren, L.H. van der Tweel and H. Spekreijse. The success of a symposium depends not only on the topics selected but also on the clarity and qUality of the presentations. In this respect it is a pleasure to acknowledge the four invited speakers for their clear and comprehensive presentations of recent research results. My co-editor, P. Apkarian, and I wish to thank all participants for timely submission of the manuscripts and for prompt response to inquiries regarding editorial matters. Mr. Peters of Junk Publishers should be acknowleged for observing publication deadlines, thus ensuring that the proceedings will reach all participants prior to the next ISCEV meeting.

ince 1985, it has been my privilege to be the Director of The - ciety of Byron Smith Fellows. During the years in which Byron SSmith was with us, his former fellows would meet at the Ame- can Academy of Ophthalmology's annual meeting. They would present to him, and to one another, interesting cases of their own compli- tions that had occurred or cases that had been sent to them that were complications to be repaired. This forum provided the fellows with an excellent format for evaluating their own problems and also for d- cussing how to treat extremely difficult cases. Shortly after Dr. Brian Brazzo completed his fellowship with me in 1998, he asked if I thought it would be appropriate for him to edit a new book on complications of ophthalmic plastic surgery. Certainly, during his fellowship, it became apparent that Dr. Brazzo was pr- ably the most gifted academician and writer that I had ever had the pleasure of training and meeting. I could think of no one more - propriate to continue the work initiated by Dr. Byron Smith and c- ried on by his students.

Forty-eight eyes with massive periretinal proliferation were examined with ultrasonography. In addition to the triangular retinal detachment T-sign was indicative of severe MPP. And irregular thickening and bending of the retina were observed on ultrasonography in eyes with MPP. The detached retina was immobile in all eyes. Preoperative ultrasonographic findings did not prove the value on the assessment of operative prognosis. REFERENCES Bronson, N.R. & Turner, F.T. A simple B-scan uitrasonoscope. Arch. Ophthalmol. 90: 237 (1973). Coleman, D.J., Koning, W.F. & Katz L.: A Hand-Operated ultrasound scan system for ophthalmic evaluation, Am. J. Ophthalmol. 68: 258 (1969). Fuller. D.G., Laqua, H. & Machemer, R. Ultrasonographic diagnosis of massive periretinal proliferation in eyes with opaque media (triangular retinal detachment). Am. J. Ophthalmol. 83: 460 (1977). Laqua, H. & Machemer, R. Glial cell proliferation in retinal detachment (massive periretinal proliferation). Am. 1. Ophthalmol. 80: 1 (1975). Laqua, H. & Machemer R. Oinical-pathological correlation in Massive periretinal proliferation. Am. J. Ophthalmol. 80: 912 (1975). Machemer, R. & Laqua, H. Pigment epithelial proliferation in retinal detachment (massive periretinal proliferation). Am. J. Ophthalmol. 80: 1 (1975). Machemer, R. & Laqua, H. A logical approach to the treatment of massive periretinal proliferation. Ophthalmology 85: 584 (1978). Machemer, R. Van Horn, D. & Aaberg, T.M. Pigment epithelial proliferation in human retinal detachment with massive periretinal proliferation, Machemer, R. Pathogenesis and classification of massive periretinal proliferation. Br. J. Ophthalmol. 62: 737 (1978).

The Conference on Subretinal Space, held between October 14 and 19, 1979, was organized to bring into the forefront some of the developments in basic and c1il')ical sciences in this field. Indeed the interaction between choroid, pigment epithelium and sensory retina in terms of the physical adherence between the tissues, transport of materials and changes produced by the growth of new vessels, fluid penetration, light damage, etc. are some of the outstanding ophthalmic problems of today. We hope that the proceedings of this Conference may be of some help in providing better understanding both of the subretinal space and of its boun daries. HANAN ZAUBERMAN, M.D. CONTENTS Preface, H. Zauberman v Basic problems related to sub retinal space The retinal circulation: past, present and future. The Fifth Abraham Albert Ticho Lecture, Paul Henkind . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pathology of the sub-retinal space, Mark O. M. Tso ....... . 11 Proteins of the bovine interphotoreceptor matrix, Alice J. Adler & Katherine M. Severin 25 Pigment epithelium, retina junction and photoreceptor distribution in man and in the horse. Histological, ultrastructural and electrophy siologicai study, J. Franr;ois, V. Victoria-Troncoso, A. De Rouck, L. Wouters & A."

This book is based on the papers presented at the Workshop on "Rehabilitation of the Visually Impaired" held in Flo rence at the Institute for the Research on Electromagnetic Waves of the Italian Research Council on April 4-6, 1984. The Workshop, sponsored by the Committee for Medical and Public Health Research of the Commission of the European Communities, was meant to exchange ideas about the need, importance and feasibility of a European cooperation in the field of visual impairment and to identify promising research areas, where current national activities could take advantage of such a collaboration in order to increase their efficiency. In particular, it dealt with the develop ment and use of technical aids (mainly based on computers and signal processing techniques) and with the elaboration, evaluation and standardization of new methods and tests. The attendance was multidisciplinary, including researchers from the fields of technology, medicine and psychology and representatives from organizations involved in the rehabi litation of the visually impaired. Five technical sessions were organized, dealing with the following topics: automatic production of Braille and systems for paperless Braille, aids for reading and for the interaction with coded informa tion sources, low vision aids, transduction of visual infor mation into a tactile representation, mobility aids. Three different application sectors were mainly considered: education and culture, vocational training, mobility. A final session was devoted to a discussion in working groups. The results are briefly outlined in the following concise report of the Workshop.

Measurement of visual acuity has been the cornerstone of visual testing since Snellen began quantitating visual acuity using letter optotypes in the 1860s. Bjerrum in the 1880s brought sophistication and quantitation to the assessment of the visual field with tangent screen examination using differently sized and colored targets. Further advances in visual testing did not occur until the Goldmann perimeter and the Farnsworth Munsell 100 Hue test were introduced in the 1940s, permitting further refinement in the detection and quantitation of acquired visual loss. An explosion of interest in sensory visual function testing followed the demonstration by Quigley and his colleagues in 1982 that despite the loss of more than 40% of the axons in the optic nerve, Snellen acuity and kinetic perimetry remained normal. Much of this interest has focused on a search for more sensitive and disease-specific sensory visual tests. Previously, novel tests used to probe visual function remained in the province of the visual physiologist and psychophysicist. These tests are now being introduced by the ophthalmologist into clinical practice. Concomitantly, the mass production of microcomputers and other technical advances have made tests such as automated perimetry and visual evoked response testing affordable for most offices. The clinician is presently being inundated with a plethora of visual function tests that may require a knowledge of visual psychophysics and statistics to understand and interpret. The purpose of this book is to acquaint the clinician with these new tests so that they may be used to maximum benefit.

Many books from symposia describe the current status in well established fields of research, where much is known and where the loose ends are only details in the picture. The topic dealt with here does not fall into this pattern. The study of time as a parameter in its own right is difficult, and the loose ends tend to do minate the present picture. Although the book does provide the reader with an overview of the field, its main value is probably to act as a source of "food for thought" for those interested in the function of sense organs and nervous systems as substrates for behaviour. The Introduction is intended to provide the readers of the book with a short guide to the topiCS discussed in the different chapters. The rather detailed Index may help those looking for information on specific topiCS. The Index also explains most of the abbreviations used in the book. The basic idea of the Danavox symposia is to invite a small group of experts to discuss a rather narrow theme in sound communication. The small number of active par tiCipants has the advantage of encouraging intense dis cussions and of avoiding overloading the program. On the other hand, selecting the partiCipants is difficult."

The value of Age-Related Macular Degeneration has stood the test of time, but progress in both basic and clinical ophthalmology has been relentless, mandating the need for an updated book. This second edition focuses on the pathophysiology and the epidemiology of age-related macular degeneration (AMD), the clinical features and management of dry and wet AMD, imaging techniques, and medical therapy for both non-neovascular AMD and neovascular AMD. It describes both clinically validated and experimental therapies as well as rehabilitation technology, and presents strategies to prevent the progression of non-exudative AMD. Results from current clinical trials are also included. New chapters in this edition cover: Genetics and treatment Oxidative stress and its relation to the pathophysiology of AMD and CNV (choroidal neovascularization-a common symptom of wet AMD) Polypoidal choroidal vasculopathy Microperimetry and psychophysical testing and ways to track geographic atrophy progression Non-VEGF pathways Retinal stem cells

This book comprises the proceedings of the first meeting of the Internatio nal Society for Corneal Research, held in Kyoto on May 12 and 13, 1978, on the occasion of the International Congress of Ophthalmology. The Society was founded by Dr. Stuart I. Brown (USA), who has to be congratulated very sincerely for this idea. The cornea, window of the eye, becomes, indeed, more and more important and its diseases more and more frequent. Consequently, cornea research is of the greatest necessity not only to cure but also to prevent the various disorders of the membrane. The scientific program of the meeting, established by Dr. Brown, was outstanding. The limiting membranes, the epithelium as well as the endo thelium, the stroma, the corneal transplantation, as well as the graft rejec tion, the inflammations as well as the immunological aspects, were discussed by experts in the field. The meeting, which was conducted by Professor Motokazu Itoi, honorary Chairman, and successfully organized by his Japanese colleagues, Professor Nakajima, Professor Mishima and their staff, was as interesting as fruitful and left in our mind the best memory. I am convinced that the ophthalmologists will take a great interest in reading the various papers, which bring the latest advances in corneal patho logy. Prof. Jules Franyois President of the International Council of Ophthalmology."

Proceedings of the Seventh Symposium of the International Research Group on Colour Vision Deficiencies Held at Centre Medical Universitaire, Geneva, Switzerland, 23-25 June, 1983

The 5th International Visual Field Symposium of the International Peri metric Society was held on October 20-23, 1982, in Sacramento, California, before the joint meeting of the International Congress of Ophthalmology and the American Academy of Ophthalmology. A majority of the members of the International Perimetric Society took part in the meeting together with many guests. The topics of the symposium were: glaucoma: correlation between the visual field and the optic disc; the visual field in low-tension glaucoma; neuro-ophthalmology and ergo-perimetry. Apart from this there were many papers on automated perimetry and general topics. The papers concerning the correlation of optic disc and visual field dealt with several aspects: peripapillary atrophy, defects in the retinal nerve fiber layer, fluorescein angiography and the characteristics of the glaucomatous excavation itself. New and interesting findings were presented showing that the careful, detailed observation of the disc and peripapillary area is re warding. The visual fields in low-tension glaucoma were studied extensively by four groups. Various approaches to the problem have led to some differences in results, which were extensively discussed. In the general glaucoma session the visual fatigue phenomenon was dis cussed extensively; apparently conflicting results were demonstrated re garding the stability of contrast threshold measurements during one and the same test session in glaucoma. The relationship between the visual field and the performance at the working place was considered in the session on ergo-perimetry."

The authors of this book are busy practical men with no particular barrow to push. The text of the book includes a comprehensive review of all aspects of intraocular lens surgery including details of the design, optics chem istry and sterilization of intraocular lenses. Its value is enhanced by excellent illustrations and extensive tabulated references to the litera ture. Accounts of patient acceptability are balanced against candid discus sion of complications and their management. The historical introduction recalls that in the early stages of develop ment of the art, over a period of 10 years, two dozen different lens designs were proposed, most claiming elimination of problems which had arisen with their predecessors. Eventually nearly all disappeared from the scene. In an age where every cataract surgeon has to determine a personal position on intraocular lens implantation the author's reflections on these matters are timely. Intraocular lenses are neither a miracle nor a menace, provided that personal decisions and preferences are carefully thought through and put into practice upon the basis of known facts and not upon the basis of fickle fashion and fad. This book provides a background upon which the reader can eva luate in his own mind the validity of information provided by the manufacturers of various lens designs."

Numerous drugs administered either generally or locally have shown a cata- ractogenic action. From a pathogenic point of view a di,stinction must be made between drugs which modify the transparency of the lens due to accumulation (mer- curic,'silver, gold salts, etc.) from those influencing its metabolism. Among the latter, Triparanol, antimitotic drugs, various phenothiazinic derivates, corticosteroids and certain miotics cause the most significatn dam- age. It is necessary to indicate the most frequent reports which evidence a relationship between a prolonged oestroprogestinic therapy and alterations of the lens transparency. The authors also indicate pathogenic mechanisms which probably cause iatrogenic cataracts. REFERENCES Apponi G., Rinaldi E. & De Simone S. Cataratta monolaterale dopo iniezione endo- carotidea di 2-3-5 Trisetilenimmino 1-4 benzochinone (Trenimon Bayer). Ann. Ot- tal. 90, 224, 1964. Baron J.B., Morel P., Rivollan Y. & Soulairac A.: Incidences ophtalmologiques du traitement prolonge par la chloropromazine associee ou non Ii des troubles cutanes. Agressiologie, 9, (2) 293, 1968. Bryk E.: Generalized argyrosis with involvement oflenses. Klin. Oczna 26,217,1956. Conel E.B. & Kelman C.D.: Ophthalmologic findings with oral contraceptives. Obstet. Gynec. 31,456, 1968. Conklin, Upton & Christenberry & MC.Donald: Citato da Duke-Elder. Radiat. Res. 19, 156,1963. Davidson S.I.: Reported adversa effects of oral contraceptives on the eye. Trans. Oph- thai. Soc. U.K. 91,561,1971. De Long S.L.: Incidence and significance of chloropromazine-induced eye changes. Dis. Nerv. Syst. 29 (3), Suppl. 19, 1968.

The Theory of Binocular Vision is a book about neurological control theory. In this sense it was far ahead of its time, for the formal development of control theory was many decades in the future when this book appeared in 1868. Hering's principal concept is that the control of eye movements is greatly simplified if there is only one neurological control system commanding the 'double-eye' as a single organ. This idea leads directly to the first thorough exposition of what is now known as Hering's law, that the corresponding muscles of the two eyes are always equally innervated. As Hering eloquently states it, "one and the same impulse of will directs both eyes simultaneously as one can direct a pair of horses with single reins" (Ch. 2). The 19th Century The book was written during an exciting era for physiological research. Before the mid-19th century the study of physiology had been limited to isolated efforts by great men who worked largely without colleagues or organized laboratories. Now for the first time of inquiry, with many sensory physiology was becoming a living field groups working simultaneously on fundamental problems. Like the classical Greeks before them in philosophy, the physiologists of the 19th century were defining in a burst of creative energy the problems 1 2 Introduction which would shape subsequent inquiry; and like the Greeks, they produced a splendid period of science.

The proceedings of this symposium on Medical Therapy in Glaucoma are divided in four major parts. The pharmacological introduction gives the reader a short description of factors that are involved between administration of the drug and its action at the desired position in the eye. The new and exciting field of drug delivery systems will be dealt with in this part and part II. Originally we had asked Ken Richardson to give part of the lectures on Membrane technology and basic aspects of cholinergic action. Unfortu nately at the last moment he could not come. Our thanks go to Gavin Paterson and Klaus Heilmann who were willing to take over a part of his job. Part II on cholinergic action offers next to the well-known drugs infor mation about Ocusert. Part III covers the new developments in the adrenergic field, including guanethidine and atenolol. The clinical aspects of medical therapy in glaucoma are covered by Part IV. Many subjects could not be handled. We left out the systemic treatment of glaucoma (diamox, mannitol etc.). We left out all special cases and prob lem cases. Some questions could be answered during the round table discus sion, most remained unanswered. It is clear that there is enough subject-mat ter and interest for another symposium on therapy of glaucoma."

Dominant exudative vitreoretinopathy (DEVR) is an eye disease which has only recently received wider attention. In 1969 Criswick and Schepens used the designation "familial exudative vitreoretinopathy" to describe a syndrome they observed in six patients belonging to two families. The condition was characterized by several symptoms involving the vitreous and retina, e. g. "posterior vitreous detachment, organized vitreous membranes, heterotopia of the macula, retinal neovascularizations, subretinal and intraretinal exudates, and localized retinal detachment". The clinical features impressed the authors as strongly reminiscent of retrolental fibroplasia, but none of the patients had a record of premature birth or postnatal oxygen administration. In 1971 Cow and Oliver described the same syndrome in several members of one family. They considered their findings to be compatible with auto- somal dominant transmission. Canny and Oliver (I976) were the first to de- monstrate the fluorescein-angiographic changes of DEVR in four members of the abovementioned family. The most striking finding was "abrupt cessation of the capillary network in a scaloped edge near the equator". Fluorescein was seen to leak from the retinal vessels localized in this marginal zone, and in some eyes from massive fibrovascular lesions as well. Similar fluorescein- angiographic changes have been described in recent years in other reports on families with DEVR (Nijhuis et aI. , 1979; Slusher and Hutton, 1979; Dudgeon, 1979; Ober et a1. , 1980; Laqua, 1980). In 1979 I commenced a clinical study of this still little-known condition at the Nijmegen University Institute of Ophthalmology (The Netherlands).

This text was designed for the physicians, nurses, technical personnel, and staff members of medical facilities using lasers for surgical, therapeutic, and diagnostic purposes. The objective is to provide an understanding of the potential health and safety hazards associated with the use of medical laser systems and the precautions needed to use them safely. To do this, it is necessary to have an awareness of applicable standargs and regula tions that apply to laser use. This book is not intended as a substitute for the American National Standards Institute (ANSI) Z-136. 3, "Safe Use of Lasers in Health Care Facilities," but to facilitate its implementation as well as the implementation of the many other related regulations and guidelines that are pertinent. These other regulations include the Medical Device Amendments to the Food and Drug Act, the Federal Laser Product Performance Standards issued under the Radiation Control for Health and Safety Act, and applicable regulations of the Occupational Safety and Health Administration (OSHA). The text is organized to provide first an overview of laser hazards, laser surgical applications, and laser biological effects. General safety control measures and safety standards are then presented. Because laser tech nology is rapidly evolving, these general guidelines will allow safe use of new laser systems as they become available. Finally, specific safety guide lines and precautions are provided for specialized laser applications in the different health care specialties."

Proceedings of the Ninth symposium of the International Research Group on Colour Vision Deficiencies, held at St. John's College, Annapolis, MD, July 1-3, 1987.

Retinopathy of Prematurity presents a review of the current knowledge of this disease, which tragically renders many premature infants blind. First, the volume covers the natural history, classification and histopathology of ROP, followed by examination techniques, recommendations for follow-up and therapy and finally a panel discussion providing answers to frequent questions and areas of legal concern.

The eye has fascinated scientists from the earliest days of biological in vestigation. The diversity of its parts and the precision of their interaction make it a favorite model system for a variety of developmental studies. The eye is a particularly valuable experimental system not only because its tissues provide examples of fundamental processes, but also because it is a prominent and easily accessible structure at very early embryonic ages. In order to provide an open forum for investigators working on all aspects of ocular development, a series of symposia on ocular and visual devel opment was initiated in 1973. A major objective of the symposia has been to foster communication between the basic research worker and the clinical community. It is our feeling that much can be learned on both sides from this interaction. The idea for an informal meeting allowing maximum ex change of ideas originated with Dr. Leon Candeub, who supplied the nec essary driving force that made the series a reality. Each symposium has concentrated on a different aspect of ocular development. Speakers have been selected to approach related topics from different perspectives."

This volume contains chapters derived from a N. A. T. O. Advanced Study Institute held in June 1983. As the director of this A. S. I. it was my hope that some of the e1ectrophysiologists could express the potentialities of their work for perceptual theory, and that some perceptionists could speculate on the underlying "units" of perception in a way that would engage the imagination of physio logists. The reader will have to be the judge of whether this was achieved, or whether such a psychophysiological inter1ingua is still overly idealistic. It is clear that after the revolution prec pitated by Hube1 and Weisel in understanding of visual cortical neurons we still have only a foggy idea of the behavioral output of any particular species of cortical detector. It was therefore particularly unfortunate that two persons who have made great strides in correlating interesting facets of cat cortical physio logy with human psychophysics (Max Cynader and Martin Regan of Dalhousie University) were unable to attend this meeting. Never theless, a number of new and challenging ideas regarding both spatial perception and cortical mechanisms are represented in this volume, and it is hoped that the reader will remember not only the individual demonstrations but the critical questions posed by the apposition of the two different collections of experimental facts. David Ingle April 1984 VII TABLE OF CONTENTS PREFACE V D. N. Lee and D. S. Young Visual Timing of Interceptive Action 1 J. J."

The HF A is a computerized perimeter with a very comprehensive set of test point patterns, strategies and custom tests. The instrument employs several solutions which have proved useful in earlier computerized perimeters and several new concepts. The construction with stimulus generation through a projection system, input through a CRT, programmes stored in PROMs and a double disc drive for storage of test results makes it simple to adapt the instrument to future needs, whether these are new test algorithms or point patterns, different input or display screens or new statistical analysis programmes. All these changes could be made without modification of actual instrument hardware. REFERENCES 1. Dannheim, F. and Drance, S.M. Psycho visual disturbances in glaucoma. A study of temporal and spatial summation. Arch. Ophthalmol. 91: 463 -468 (1974). 2. Fankhauser, F. and Hiiberlin, H. Dynamic range and stray light. An estimate of the falsifying effect of stray light in perimetry. Documenta Ophthalmol. 50: 143-167 (1980). 3. Fankhauser, F., Hiiberlin, H. and Jenni, A. Octopus programs SAPRO and F. Two new principles for the analyses of the visual field. Graefes Arch. Klin. exp Ophthal- mo1216: 155-165 (1981). 4. Gramer, E. and Krieglstein, G.K. Zur Spezifitiit der iiberschwelligen Computer- perimetrie. Klin. Mbl. Augenheilk. 181; 373-375 (1982). 5. Gramer, E., Kontic, D. and Krieglstein, G.K. Die computerperimetrische Dar- stellung glaukomatoser Gesichtsfelddefekte in Abhangigkeit von der Stimulus- grosse. Ophthalmologica 183: 162-167 (1981).

The Seventh International Visual Field Symposium organized by the Interna tional Perimetric Society was held in Amsterdam, The Netherlands, September 6-10,1986. In many respects it was an exciting and fruitful meeting. The number of participants was greater than ever. The number of papers was too great to accommodate all of them. The quality of the papers reflects the continuously rising interest in perimetry in general and in automated perimetry in particular. Last but not least the social programme was organized in the, by now, almost classical friendly, enjoyable and humouristic style of the International Perimetric Society. This created an atmosphere of openness and free exchange of informa tion whICh was clearly also felt in the scientific sessions. The scientific part was divided in seven sessions with 44 spoken papers and a separate postersession during which the 46 posters were discussed. The major themes of the meeting were 'The influence of media-disturbances on the visual field' and 'Advances in perimetry in glaucoma with special emphasis on pro gression'. The session on 'media' provided interesting information on how the visual field was effected by preretinal filters. The authors either studied the influence of lens or corneal opacities or simulated opacities by special filters placed in front of the eye. In two papers the effect of cataract was qualified by photography or stray light measurements."