New approach to Visual Rehabilitation, “virtual reality” system P.G. Limoli
Introduction Impaired vision is a condition whereby a patient, affected by not reversible neurophthalmic pathology, is subject to a reduction of the visual function that cannot be corrected with standard lenses and results in visual disability in respect of the necessary visual needs (1, 2, 3, 4). In recent years the definition “low-vision” has certainly become more familiar in ophthalmology as this condition has become more frequent for two reasons: the senile population has increased steadily and as consequence the degenerative pathologies, which mainly affect the aged, are increasing; on the other side, the level of ophthalmic therapy and prevention has increased dramatically, especially after the 1970’s, this has reduced the number of patients whose illness resulted in blindness, and conversely increased the cases where therapy allows to maintain residual vision which if not useful in itself may at least be utilized (4). Patients may be defined low-vision for a variety of reasons. Some have impaired vision because of a central scotoma in their field of vision, others suffer of a general retinic sensitivity reduction, others are subject to tubular contraction, or various amputation of their visual field (3, 4). The common experience of those who examine these patients is that it is difficult to find two exactly similar low-vision patients. It is highly improbable that two patients have similar characteristics with regard to the type of pathology and its evolutionary trend, visual acuity (far and near), specific needs, clinical condition in both eyes, necessary magnification, preferred system reading speed, age, socio-cultural condition, etc. Variations observed in treating low-vision patients make statistical evaluations
unreliable and the application of a rational unified protocol is difficult. Testing various magnifying systems to ascertain which is the best one is a lengthy process. These lengthy tests reduce the patient's attention, quality of performance, precision of the choice, and finally increase the frustration of the patient. Our goal is to find a method to make the visual rehabilitation more simple, quick and precise. As a consequence, we suggest that the simulation of the condition of impaired vision may be useful in research on low vision. The basis of simulation as a research method is in fact the artificial reproduction of the phenomenon under examination, this phenomenon can be reproduced with the help of mathematical models, through its virtual rapresentations with a personal computer (5, 6, 7, 8, 9, 10). The following reasons suggest to replace the real object with a virtual one: first of all, the possibility to give an example and visualize schematically the concept of low vision, which is often not well defined; secondly, the opportunity to study a virtual model representing the patient without his necessarily being present, in other words the theoretical representation of a real case. The virtual model leads to other benefits motivations lead to other advantages: quickness and ease of use, the examination can be reproduced where and when desired, specially presents an accurate predictive different hypothetical solution to be applied after appropriate evaluation to the low vision patient while becoming a valuable education tool (11, 12, 13, 14, 15, 16, 17). We conducted a selection of the schematics aspects to represent vision in low vision patients.
This simplification allows a “clean” observation with no unnecessary elements, to test the theorical model in a precise and controlled way. In 1991 we started to apply the information obtained from virtual techniques to visual rehabilitation. Patients and methods Let us examine, the disturbed vision of a low vision patient: observe the relationship between an eye with low vision due to a central scotoma and an object. Normally, if the object’s dimension is contained within the scotoma, it cannot be perceived. The patient must therefore resort to two automatic and not-hierarchic compensative mechanisms: decentralization and enlargement of the image to be seen. Decentralization allows the perception of the object, or unvariant parts, by projection on working the retina areas, contiguous to the damaged one (excentric fixation). Enlargement is obtained instinctively by moving the low vision eye closer to the object: its projection on the retina grows until it stimulates enough active receptors to start retina and central perceptive mechanisms (18, 19 ). Of course there are other magnification mechanisms, such as the enlargement of the object or, more often, optical or electronic enlargement systems. These systems, however, cannot be used immediately: the patients visual field can vary, the system visual field has different configurations, and often patients must exercise retinal areas never used before in fine sight processes (reading etc...). It is therefore useful to chart training exercises to bring patients in the habit of using the appropriate and inducing them to exercise their reading and writing abilites and visual field coordination. It is most important to exercise excentric sight during reading, particularly for low vision patients. Decentralizing an image to an area with a lower density of receptors reduces substantially the patient’s ability to
discriminate, partially compensated with the enlargement: the signal, however, is transmitted through alternative channels, creating the necessity for re-education of the patient’s perception from this new source. There already exist exercises with such purpose, designed to target vision above or below the string of characters; the main limitation is that they offer standardized answers to a universe with many different needs even when belonging to the same rehabilitation category or suffering from the same pathology at the same state of evolution (ex. age related macular degeneration). We chose to simulate the processes described above on the basis of a radically new concept of the personal computer which allows today, to create an environment in which it is possible to sort, organize and ultimately unify on a single medium all data acquired and with which it is possible to interact, with a mouse, in real time and as a matter of routine. Such characteristics define this method as a virtual reality (VR) technology, particulary VR “desktop/vehicle” (others are defined “immersive” and “third person” ) (20, 21, 22, 23, 24). With no need for advanced interaction such as in immersive VR, the operator, sees the simulated environment on a 2-dimension monitor: summaring, the simulated reality we are describing is a reality observed from a window, without actually entering. This type of VR has the advantage of being much more economical than the advanced immersive version, and does not require sophisticated cybernetic equipment to simulate immersion in a 3-D environment. Virtual technology has increased scientific progress in many fields, even if we have only recently begun to see the practical application in rehabilitation field. On the basis of all the above, we have developed at the Low Vision Research Centre of Milan (Italy) a technique for assessment of the visual system in low vision patients which we defined as Virtual Visual Rehabilitation (VVR): the relative graphic rapresentation is the “visual virtual map” (25, 26), obtained by
a new ophthalmological software definited Virtual IPO®. Virtual IPO® is an integrated computerized system for analysis of vision and rehabilitation of patient with impaired vision (27, 28, 29). The PC graphic simulation program is used to recreate the patient’s sight condition, overlaying their field of vision determined according to the Goldmann method, Octopus method or other techniques for analysis of visual field, to a pre-determined size of text (10 pts). The areas delimited by the isopteras are filled in with appropriate contrasting backgrounds for the simulations. A part from the possibility to freely enlarge the text, one can move it, away from the starting point, to the desired degree and direction. That is possible thanks to a particular program which allows to divide the image, (in our case, field of vision and reading text) into 2 or more independent levels. Moving the text on the field of vision grid reproduces the visually impaired patient moving the text he is reading, his head or his eyes, in order to project the image on the functioning areas of the retina. The use of the computer as a mean to regroup these data allows to point out the degree of eccentric vision, intended as the angle the eye forms between the virtual patient starting point and the top medium alignment of the string of letters. The program has an accessories menu which are the visual fields related to various optical systems: a 3x magnification makes reading different when using a Galilean system rather than high-add spectacles; the dimension of the visual field offered by the system interacts with the shape and dimension of the scotoma, if existing, and with the residual contrast of the patient field of vision. That is why the operator has a good idea, considering the reading physiology, of how the patient actually sees the text. Graphic simulation allow text scaling, contrast tuning and use of other everyday objects (TV for instance); this enables the operator to understand fully the way a patient sees (with no active partecipation by the patient himself)
and to determine the best potential enlargement system (high-add spectacle, Galilean or Keplerian telescopes or electronic monitor) obtained with minimum magnification and decentralization. The patient then tries the result from the virtual research . The operator virtually acting as the patient selects the most appropriate enlarging system. The advantage, besides the time gained, is the precision of information (degree and direction of excentric vision, number of letters for field of vision or useful magnification) from which it is possible to chart personal exercised to do at home, without aids, or at the Centre with aid, in order to determine the most effective prescription. Such exercises are charted in such a way that the proposed target vision allows the string of characters to be projected on the functioning area of the retina which has been determined through the virtual evaluation of the visual field. The exercises for assimilating magnifying systems are designed according to the formula, calculated from data obtained through Virtual IPO®. The eye-target on the exercise will be positioned n mm. from normal focus of the string of characters (middle-upper alignment) in the direction predetermined for the exentricity of sighting, which generally develops in the direction of the use of an earlier vision of the perceptive invariants. Patients using Virtual IPO® are invited to read using the correct system from the very start: they aim at a target which enables them to perceive the desired string of characters through the residual functioning retinal area which has already been identified. Immediate results encourage patients to continue rehabilitation exercises. We believe such elements are essential for charting personalized reading exercises: they can be carried out in life size (10 cp) that enables patients to read the text using an appropriate magnifying system in a Low Vision Centre or they can be carried out magnified, with the adeguate aiming target, and be used at home by patients, all that
before a decision is taken on prescribing or buying the system. We asked ourselves how reliable the virtual technique could be in the field of visual rehabilitation. We tested virtual visual rehabilitation on 103 patients aged between 18 and 95 years (average 67 years), 62 (60,19%) female and 41 (39,81%) male. These patients were defined low-vision insofar as they belonged to at least one of these categories: 1 Best corrected visual acuity less than 3/10 (W.H.O.) 2 Near visual acuity less than 10 pts (Low Vision Research Centre of Milan) 3 Amputation or contraction of visual field. 4 Specific vision necessities (Low Vision Research Centre of Milan) The criteria used to include those patients require some comments, in particular for points 3 and 4. The average of BCVA is 0,172 (max 0,9, min. 0,005); average near visual acuity is 39,14 pts with physiological correction (max 6 pts,m min. 140 pts). All were offered Virtual IPO®. For each eye the following indications are supplied: BCVA afar in tenths (Snellen), residual near visual acuity in pts, near visual acuity with magnifying system in pts, magnification identified with Virtual IPO®, real magnification, the system identified through Virtual IPO®, the system recommended, reliability, degree and direction of decentralization needed during reading, number of letters contained in every reading field, reading speed in words per minute recorded at the beginning and at the end rehabilitation (Table 1). Virtual data were used for visual rehabilitation. The reliability of Virtual IPO® is assessed through comparison of real and virtual data.
We have considered real and virtual magnification, reading field (virtual number of letters for fixation), final reading speed (words per minute), final reading coefficient (words per minute * C-RBT/100, where CRBT is the comprehension-retention in a short time). Statistical analysis was done by correlation tests using the Statwiew program for Apple Macintosh computers. Results The reliability of Virtual IPO® is evaluated on a group of 103 visually impaired patients independently from their pathology. The pathology could influence the reliability of VVR (for example coexistence of cerebral vasculopathy). The correlation between virtual and real magnification was highly significant statistically (r=0,98 with p=00000,1). Virtual magnification was correlated statistically with final reading speed (r= -0,53 with r=0,00001), final reading coefficient (r= -0,53 with r=0,00001), reading field (r= -0,48 with p=0,00001).
The reliability of Virtual IPO® as resulting from the comparison between virtual and real data, appears to be high in determining the correct degree of magnification. For the latter, Virtual IPO® submits more than one option: the system is recommended by the ophthalmologist on the basis of the quality of residual vision, binocularity, working distance, specific needs, cost. Knowing before, the required magnification degree and the system to achieve it reduces the time spent in searching for the most appropriate aid, increases the accuracy of such research and maintains high patient's attention, allows a better dialogue with patients and reduces the stress for the specialist. The preliminary knowledge of the degree and direction of decentralization necessary for reading and the number of letters per reading
field (data obtainable only trough Virtual IPO®) allows planning of the rehabilitation process through custom designed reading exercises which induce low vision patients to use their functionally integre retinal areas with the help of appropriate pointers. Furthermore, the degree of decentralization and the number of letters for reading field have an important prognostic significance: they allow indications for visual rehabilitation when the degree of decentralization is less than 4° and when the number of letters is equal to or more than 5. When such conditions do not exist reading becomes painfully slow, excessively difficult if not impossible. In these cases visual rehabilitation is suggested only if there is strong patient motivation. Conclusions Virtual representation obtained with Virtual IPO® gives us a virtual patient similar to the real one: we can quickly and precisely test the best magnification and decentralization. Necessary magnification is inversely proportional to the reading field, reading speed and the reading coefficient. With Virtual IPO® we can find a way to read with the lower magnification and the higher reading field, to obtain the higher final reading coefficient. Moreover, less tests seem to be the best way to increase the patient's attention, quality of performance, precision of choice, and finally less frustration of the patient. In the field of visual rehabilitation there has never been a diagnostic system able to evaluate the magnification and the type of system which together gives prognostic information on the visually impaired patient. It is for this reason that the reliability of such a system looks to us high or anyhow important, to be able to choose between two systems within the proposed magnification looks like a progress against a rather difficult and archaic research by the patient, the oculist can have at his disposal some important data before to indicate the most adeguate rehabilitation program or prescribes a suitable system, as when schiascopy or
autocheratorefractometry are used to prescribe corrective lenses. Virtual IPO® appears to be a reliable technique for selecting the most useful degree of magnification for low vision patients and in identifying the most appropriate system to obtain such magnification. It is a unique instrument for developing customized exercises and it is promising in judging rehabilitation prognosis for low vision patients. Virtual IPO® is indicated for low vision patients for whom the required magnification may be obtained with a variety of systems (where close vision is between 18 and 54 pts). In other cases it is useful when a patient has lost the useful central fixation, as it allows for designing exercises for stimulating use of excentric vision. Virtual IPO® may be used telematically for easy rehabilitation of patient residing far from Centre, simply sending by mail visual field measures, taken at fixed dates. It is a model for sight-system studies, allowing simulation of different sight conditions. Physiology of reading may be studied in-depth, articulate didactic programs may be constructed on the subject, operators may be trained in a short time, putting them virtually in place on their patients. Virtual IPO® does not imply high costs as it uses only one specific PC software, optimizing the classic Goldmann perimeter, computerized perimeters or microperimetry. This method offers many possibilities. We can correctly define visual rehabilitation for each low vision patient, but we can also study the effects of photodynamic therapy, neural photostimulation, antiapoptotic therapy , neurotrophic factors, and the impact they have on rehabilitation parameters such as the reading field, decentralization and magnification. REFERENCES 1. Cullinan TR. Visually disabled people in the community. Health Services Research Unit Report 28, Table 21, 1977. 2. Silver S. Visual disability. Part 1: Introduction and epidemiology. The
Ophthalmic Optician 841-842, 18/12/1982. 3. Hyvarinen L. Classificazione delle menomazioni visive. Chibret int J Ophthalmol. 6 (1): 5-13, 1990. 4. Genesky SM. A functional classification system of the visually impaired to replace the legal definition of blindess. Rand.Corp., Santa Monica CA, 1970. 5. Blanchaer MC. A role for clinical case simulation in basis medical science education. The Physiologist, 28, 422-424, 1985. 6. Bishop CW. Teaching diagnosis by computer. The Physiologist, 28, 451, 1985. 7. Bonolio M. La Costruzione del Vedere. Simulazione Visiva, Realtà Virtuale e Costruzione del Mondo. Edizioni Nuovo Progetto. Vicenza, 1992. 8. Caudell TP, Summers KL, Holten J 4th, Hakamata T, Mowafi M, Jacobs J, Lozanoff BK, Lozanoff S, Wilks D, Keep MF, Saiki S, Alverson D. Virtual patient simulator for distributed collaborative medical education. Anat Rec 2003 Jan;270B(1):23-9 9. Cunningham D, Krishack M. Virtual Rehabilitation Works, Inc., Birmingham, Alabama 35244, USA. Virtual reality: a wholistic approach to rehabilitation. Stud Health Technol Inform 1999;62:90-3 10. Department of Developmental and Rehabilitative Sciences, University of Medicine and Dentistry of New Jersey, 65 Bergen St, Newark, NJ 07103, USA. Virtual reality-augmented rehabilitation for patients following stroke. Phys Ther 2002 Sep;82(9):898-915 11. Ford L. Teaching strategies and tactis in intelligent computer assisted instruction. Artificial Intelligence Review, 1987, 1, 3, 201-215 12. Gellrich NC, Schramm A, Hammer B, Rojas S, Cufi D, Lagreze W, Schmelzeisen R. Department of Oral and Maxillofacial Surgery, Albert-LudwigsUniversity, Freiburg, Germany. Computer-assisted secondary reconstruction of unilateral posttraumatic
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2 Limoli PG, D’Amato L., Giulotto A., Franzetti M, Carella A. “Virtual Visual Rehabilitation. Reliable for assessing the visual system in low vision patients?.” EUROPEAN SOCIETY OF OPHTHALMOLOGY, Xth Congress,1993. Milano, Italy, June 2529, 1995.
Fig. 1: This is, as appears, the input mask of the virtual vision pre-map. At the top, on the right there are some bottons called rehabilitatives tools, whereby it is possible to import the visual field or the micro perimeters of the low vision patient and adapt it at the program in order to simulate how that patient see with a graphic approximation.
Fig. 2: In this imagine we observe an Octopus visual field just imported in the simulation program. We must underline the centering of the image and of the corner taken in consideration before to give the authorization to import the visual pre-map of the patient.
Fig. 3: After importing, the visual field is coincident with the mask of virtual visual pre-map. We can begin to turn to our simulation.
Fig. 4: We can help with the HTML guide that tells us for each isopter of the visual field what kind of virtual isopter choose.
Fig. 5: The originals isopters are replaced by appropriate contrasts of gray that transform the original visual field in the virtual visual pre-map.
Fig. 6: The operator tries to read a string of 10 pts through the visual field of the patient to confront his disability. At this point the simulation begins.
Fig 7: In the virtual visual map the operator enlarges and decentralizes the string reading until it is readable with the lowest possible magnification and decentralization. In this case we need 5 magnifications and a PRL in a lower positions of 12.7 째. The program tells us that to stimulate this PRL we will use an exercise with targets of fixation setting lower than 3 mm. inferiorly at the superior average alignment of the string.
Fig 8: The program, in addition to providing data for the stimulation of PRL, allows, using the library Accessories, to search and print the exercise useful to assimilate the use of PRL less than 3 mm. or those that we considered most appropriate from time to time.
Fig. 9: The exercises are configured so that fixing the target the string position is correctly setted in PRL. So the patient uses to assimilate the system the apposite exercise developed on its own PRL. The target of fixation is perceptually relevant and due to the cerebral integration is seen complete even if crossed by absolute scotoma and therefore can be followed during the reading of the string without any problems.
Fig. 10: Let analyze this case of central scotoma. The scotoma is not particularly large but sufficiently deep, this allows a decentralization of more than 2 째 about, but still requires a large 3.5 X magnification. This result can be reached by an magnyfing system of 14 diopter or by an aplanatic, in this case preferable for the less optical aberrations. The reading range of 7 letters suggests a good prognosis.
Fig. 11: In this map we see the behavior of a patient with retinitis pigmentosa and tubular field. The patient does not see beyond the twentieth and 30 cp to close. The maximum magnification that allows to appreciate a range of 4 letters is 2X. But the perception of the string is very difficult because of low light sensitivity of the residual functional area.
Also could try an optical system for 2 X, it's better use a video magnifier with negative contrast at low magnification.
Fig. 12: In this case we observe the rehabilitative behavior of a Mrs. myopic 24 D that, after the shutdown of its MNV gotten with two photodynamics treatments, presents a state of moderate low vision. The visual acuity for near is not enough to read, but a magnification of 2 X and an inferiorly decentralization of 1.6 째 allows a more than acceptable reading with a simple iper-corrective. As there is an initial cataract and an high myopia we imagined, using the estimates prevision obtained by simulation, to remove the cataract and insert an IOL with a myopization of - 4 D in order to use a ipercorrective system of only + 4 D (total magnification 2X). The prediction proved correct and now the lady reads the newspaper without glasses, while uses a lens of + 4 for the smallest things.
Fig. 13: In this case we observe a kind of bitubular field. This is a one-eyed patient suffering from myopia of 23 diopters already surgery with cerclage operation for retinal detachment. The quality of the retina due to the high myopia and to the outcome of the surgery means that the is very low and only in two points. We are obligated to prefer the less sensitive PRL because it is less decentralized than the other witch is more than 15째 away from the foveal area and that would require an higher magnification. For its rehabilitation we will choose a video
low magnification.
magnifier with negative contrast at
Virtual Patient - Real Patient MAGNIFICATION 2 = ,967
y = 1,018x - ,175 r
11 10 9 8 7 Real magnification 6 5 4 3 2 1 1
2
3
4
5
6
7
8
9
10
11
Virtual magnification
Fig.14: A comparison between virtual and real magnification: the reliability of the virtual visual map is 97%.
Summary: The virtual visual rehabilitation is a diagnostic technique that allows to simplify the visual rehabilitation of low vision patients. The authors performed a retrospective study comparing data magnification necessary to restore the ability to read virtually achieved through the application of the data provided by the software rehabilitative and magnification actually found and then prescribed in the real visual rehabilitation. The comparison is a highly significant correlation between the "virtual patient" and the real patient. The virtual visual rehabilitation may be considered an advanced and reliable diagnostic method in evaluating the low vision patient and in setting its visual rehabilitation
The virtual low vision patient, real and virtual data.
Paolo Limoli MD°, Sergio Z. Scalinci*, Enzo Vingolo PhD^ °Low Vision Research Centre - Milano ^La Sapienza University- Roma * Università degli Studi - Bologna
Corresponding Author's information: Low Vision Research Centre - Milano Piazza Sempione 3, 20154 Milano - Italia Tel/Fax: 02-3318996 e-mail: filippo.tassi@hotmail.it paolo.limoli@centrostudioipovisione.191.it
The authors have any direct interest and any grant or fund was received for the study. The study was presented at ARVO 2003, Fort Lauderdale USA.
Abstract: Pourposes: Visual rehabilitation for low vision patients presents one main problem: it is a lengthy process to test the magnifying system in order to ascertain which is the best solution. These lengthy tests reduce the patient's attention, quality of performance, precision of the choice, and finally increase the frustration of the patient. Our goal is to find a method to make the visual rehabilitation more simple, quick and precise. Methods: We have created Virtual IPO速, software with a computerized simulation of a patient's visual performance, that permits us to understand the existing visual conditions and suggests the best magnification and decentralization necessary to restore reading ability. We tested virtual visual rehabilitation on 103 low vision patients, we considered real and virtual magnification, reading field, final reading speed, final reading coefficient. Statistical analysis was done by correlation tests using the Statwiew program for Apple Macintosh computers.
Results: The correlation between virtual and real magnification was highly significant statistically. Virtual magnification was correlated statistically with final reading speed, final reading coefficient, reading field. Conclusions: Virtual representation obtained with Virtual IPO速 gives us a virtual patient similar to the real one: we can quickly and precisely test the best magnification and decentralization. Less tests seem to be the best way to increase the patient's attention, quality of performance, precision of choice, and finally less frustration of the patient. We can correctly define visual rehabilitation for each low vision patient, we can also study the effects of photodynamic therapy, neural photostimulation, antiapoptotic therapy, neurotrophic factors, and their impact on rehabilitation parameters.
Key words: Low vision, customized rehabilitation, Virtual Visual map, Visual rehabilitation, Virtual Visual Rehabilitation (VVR).