The relevance of assessing pupil diameter, working distance and illumination in real life conditions when selecting a multifocal lens design for the presbyopic patient

Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados GRAU EN ÒPTICA I OPTOMETRIA TREBALL FINAL DE GRAU THE RELEVANCE OF ASSESSING PUPIL DIAMETER, WORKING DISTANCE AND ILLUMINATION IN REAL LIFE CONDITIONS WHEN SELECTING A MULTIFOCAL LENS DESIGN FOR THE PRESBYOPIC PATIENT SILVIA LÓPEZ BAUSILI GENÍS CARDONA TORRADEFLOT DEPARTAMENT D’ÒPTICA I OPTOMETRIA 26 de Gener del 2015 Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados GRAU EN ÒPTICA I OPTOMETRIA El Sr. GENÍS CARDONA TORRADEFLOT, com a director/a del treball CERTIFICA Que la Sra. SILVIA LÓPEZ BAUSILI ha realitzat sota la seva supervisió el treball THE RELEVANCE OF ASSESSING PUPIL DIAMETER, WORKING DISTANCE AND ILLUMINATION IN REAL LIFE CONDITIONS WHEN SELECTING A MULTIFOCAL LENS DESIGN FOR THE PRESBYOPIC PATIENT que es recull en aquesta memòria per optar al títol de grau en Òptica i Optometria. I per a què consti, signo aquest certificat. Sr. Genís Cardona Torradeflot Director del treball Terrassa, 12 de Gener de 2015 Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados GRAU EN ÒPTICA I OPTOMETRIA THE RELEVANCE OF ASSESSING PUPIL DIAMETER, WORKING DISTANCE AND ILLUMINATION IN REAL LIFE CONDITIONS WHEN SELECTING A MULTIFOCAL LENS DESIGN FOR THE PRESBYOPIC PATIENT SUMMARY Purpose: Determinate the visual needs of presbyopic patients in terms of habitual tasks, measuring working distance and assessing pupil diameter. This information can be useful for eye care practioners in the selection of the best contact lens design for each patient, once their particular needs and expectations have been investigated. Methods: A total of 59 presbyopic subjects took part in the study. Inclusion criteria was age between 45 and 65 years (inclusive), previous monofocal contact lens wearers and non-wearers. Patients manifestin any eye disease, injury or abnormality of the cornea, strabismus or ambliopia or a clinically significant anisocoria were excluded from the study. Subjects were firs interviewed regarding their visual demands with the aid of an ad hoc questionnaire. Then, pupil diameter of each participant while conducting each of their described (in the questionnaire). Habitual tasks was determined. In addition, working distance was determined with a measuring tape and the illumination that reached the pupil during each of the diferent tasks was measured, in lux, with a light meter. Statistical analysis was performed with the SPSS software 19.0 for Windows. Results: A total of 59 patients with diverse backgrounds participated in the study. Forty-eight (81.4%) of the participants used glasses or contact lenses daily. Of those requiring visual correction, 15 subjects were using or had used contact lenses, and, with the exception of 3 participants, all contact lens wearers reported good comfort with their lenses. Interestingly, only 7 patients (11.9%) had tried multifocal contact lenses and only one was still using them. Conlcusion: The main findings of the present research may be summarized as that there is an important lack of information about multifocal contact lenses. The pupil diameter and the multifocal lens addition depend on the age, the job, the custom of lighting and working distance. That’s why, it’s very important to take in count all this parameters. Each patient have a different pupil diameter and working distance which entail to a change add power lens. Finally , is critical to measure the pupil diameter while the users conducted their habitual tasks to ensure that a particular lens design is suitable for an individual patient. Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados GRAU EN OPTICA I OPTOMETRIA RESUM Objectiu: Determinar les necessitats visuals dels usuaris prèsbites segons les seves tasques habituals, mesurant la seva distància de treball i el diàmetre pupil·lar. Aquesta informació pot ser útil pels Optometristes en la selecció de la lent de contacte més adequada per a cada usuari. Metodologia: Van participar a l’estudi un total de 59 usuaris prèsbites. Es van incloure usuaris d’entre 45 i 65 anys, usuaris i no usuaris de lents de contacte. Es van excloure usuaris que presentessin algun desordre ocular, lesió corneal, estrabisme, ambliopia o anisocòria clínicament significant. Primer es va passar un qüestionari preguntant sobre la demanda visual al realitzar les seves tasques habituals. Després es va mesurar el diàmetre pupil·lar mentre realitzaven aquestes tasques, aquest diàmetre es va mesurar amb un regle. També es va mesurar la distància de treball amb una cinta mètrica i la il·luminació que arribava a la pupil·la amb un luxòmetre mentre realitzaven les seves tasques. L’anàlisi estadístic es va realitzar amb el programa SPSS 19.0 per a Windows. Resultats: Van participar a l’estudi un total de 59 usuaris amb diferents perfils i historial. Quaranta vuit (81.4%) dels participants portaven ulleres o lents de contacte a diari. D’aquests que necessitaven correcció, 15 feien servir o havien fet servir lents de contacte i, a excepció de 3, la resta d’usuaris de lents de contacte van afirmar que els hi eres còmodes les seves. Una dada interessant va ser que només 7 dels participants (11.9%) havien provat les lents de contacte multifocals i només 1 les feia servir encara. Conclusions: La conclusió principal d’aquest estudi ha sigut que hi ha una important manca d’informació sobre les lents de contacte multifocals. El diàmetre pupil·lar i l’addició de les lents de contacte multifocals depèn de l’edat de l’usuari, de la seva ocupació principal i dels hàbits de llum i distància de treball. Per això és molt important tenir en compte tots aquests paràmetres. Cada usuari té un diàmetre pupil·lar i distancia de treball diferent cosa que implica que els canvis de potència en les lents de cada usuari hagi de ser diferent. Finalment, és crític mesurar el diàmetre pupil·lar en les condicions habituals de cada usuari per a aconseguir les lents de contacte més adequades per a cadascú i així garantir una bona visió i la màxima confortabilitat. Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados GRAU EN OPTICA I OPTOMETRIA RESUMEN Objetivo: Determinar las necesidades visuales de los usuarios présbitas según sus tareas habituales, midiendo la distancia de Trabajo y el diámetro pupilar mientras las realizan. Esta información puede ser útil para los Optometristas que deban adaptar las lentes de contacto, para así encontrar la más adecuada para cada usuario. Metodología: Un total de 59 usuarios présbitas tomaron parte en el estudio. Se incluyeron personas de entre 45 y 65 años, usuarios y no usuarios de lentes de contacto. Se excluyeron aquellas personas que presentaran algún tipo de desorden ocular, lesiones corneales, estrabismo, ambliopía o una anisocoria clínicamente significante. Primero se les pasó un cuestionario donde se les hacían preguntes acerca de la demanda visual al realizar sus tareas habituales. Después se midió el diámetro pupilar con una regla mientras realizaban éstas tareas. También se midió la distancia de trabajo, con una cinta métrica, y la iluminación que llegaba a la papilla, con un luxómetro. El análisis estadístico se realizó con el programa SPSS 19.0 para Windows. Resultados: Participaron 59 usuarios con diferentes perfiles e historial. Cuarenta y ocho (81.4%) de los participantes usaban gafas o lentes de contacto a diario. De éstos, 15 utilizaban o habían utilizado lentes de contacto y, a excepción de 3, el resto afirmaron confortabilidad con ellas. Un dato interesante fue que, únicamente 7 de los participantes (11.9%) habían probado las lentes de contacto multifocales y solo 1 las utilizaba aun. Conclusiones: La conclusión principal del estudio ha sido que existe una importante falta de información sobre las lentes de contacto multifocales. El diámetro pupilar y la adición de las lentes de contacto multifocales dependen de la edad del usuario, de su ocupación principal y de los hábitos de luz y distancia de trabajo. Por eso es muy importante tener en cuenta todos estos parámetros. Cada usuario tiene un diámetro pupilar y una distancia de trabajo diferente, eso implica que los cambios de potencia en las lentes de cada usuario deben ser diferentes. Finalmente, es crítico medir el diámetro pupilar en las condiciones habituales de cada usuario para conseguir las lentes de contacto más adecuadas para cada uno y así garantir una buena visión y la máxima confortabilidad. Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados INDEX 1. Introduction, 7 2. State of the Art 2.1. Presbyopia, 8 2.2. Optical compensation 2.2.1. Spectacles, 9 2.2.2. Contact lenses, 10 2.2.3. Monovision, 10 2.2.4. Surgery, 11 2.3. Contact lenses 2.3.1. Rotational, 11 2.3.2. Non-rotational, 12 2.3.3. Simultaneous-image (vision) designs 2.3.3.1. Depth of Focus, 13 2.3.3.2. Concentric, centre-near or centre-distance, 15 2.3.3.3. Modified monovision, 19 2.3.3.4. Considerations regarding pupil diameter, 20 2.3.3.5. Success with multifocal lenses, 20 3. Objectives and hypothesis, 22 4. Subjects and Methods, 4.1. Study sample, 23 4.2. Methods, 23 4.3. Data analysis, 27 5. Results 5.1. Study sample description, 28 5.2. Pupil diameter measurements, 29 5.3. Habitual tasks, 29 6. Discussion, 35 7. Conclusions, 39 8. Article, 40 9.References,41 7 Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados 1. INTRODUCTION In the aging world, the number of presbyopic patients has been growing exponentially year after year. Nowadays, there are more than 20 million presbyopes in Spain. This number represents more than 40% of the total population (INS, Instituto Nacional de Estadística)1. Worldwide, about 50% of the population is presbyopic and in the last two decades this percentage has been documented to be even larger in Europe2. Therefore, it may be assumed that this can be a good opportunity for the professional development of contact lens solutions for presbyopia. With every generation there is a progressive evolution in the visual needs and overall expectations. Today’s presbyopes are not the same as the presbyopes years ago: they are health-conscious individuals, physically and socially active, computer-savvy and interested in maintaining a youthful appearance. They need to be offered optimal optical compensation for their needs and, therefore, it is a good time to increase the number of contact lens fittings in presbyopes. To ensure visual satisfaction, we must make the right choice of lens design and material and achieve good fitting conditions. Furthermore, the presbyopic eye is not a young eye, whereupon particular care shall be necessary to manage a successful contact lens fit devoid of complications. Advances in research and development have produced different kinds of multifocal contact lenses with considerable improvement in lens designs and material technology. Many of these designs involve simultaneous vision, which has been found to be very sensitive to pupil diameter changes and to working distances. Therefore, some of the most important factors in patient selection are motivation and proper assessment of the patient’s visuals needs. Patients must be asked to provide complete information about their lifestyle, including habitual lighting conditions and working distances. It will be the job of a good contact lens practitioner to select the best design for each patient, according to this information. It was the aim of the present study to determine the visual needs of a group of presbyopic patients in terms of habitual tasks, both at home and at the workplace, and to assess working distance for each task. In addition, pupil diameter was measured while patients were instructed to perform these visual tasks under usual (distance and illumination) conditions. It was believed that, with this information, relevant insight would be obtained to help eye care practitioners in the selection of the best contact lens design for each patient, once their particular needs and expectations have been investigated. 8 Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados 2. STATE OF THE ART 2.1. PRESBYOPIA Presbyopia is a common type of vision disorder that occurs with increasing age. It results in the inability to focus objects located at close distances, a problem associated with inadequate refraction in the eye. Presbyopia is a physiological consequence of the aging eye. The eye is not able to focus light directly onto the retina due to the hardening of the natural lens (Figures 2.1 and 2.2). Aging also affects the muscle fibres around the lens, making it harder for the eye to focus on upclose objects: the ineffective lens causes light to focus behind the retina, causing poor vision of near objects. Presbyopia usually begins at around age of 45 and affects everyone, although patients with low myopia may have fewer difficulties in the first years following the onset of presbyopia if they use their naked eyes to view near objects. Around the age of 65, the eyes have usually lost most of the elasticity needed to focus near objects, although it is still possible to read with the help of appropriate prescribing. The most frequent signs and symptoms associated with presbyopia include the following:  The need to hold reading material farther from the eyes.  Problems in seeing near objects.  Headaches.  Eye strain. Fig 2.1. Normal eye3 Fig 2.2.Presbyopic eye3 Physiologically, a presbyopic eye is different from a younger eye. It may be found to have a smaller pupil size, a lower tear volume, a loss of elasticity of the eyelid and of corneal transparency and mechanical sensitivity and an increasing appearance of conjunctival redness. In addition, the presbyopic eye needs more oxygen to maintain a proper metabolism and may present an increase in positive spherical aberrations (conversely, the young lens is able to compensate for the positive spherical aberration the cornea) and light scatter (glare) due to the presence of intraocular opacities, particularly with the onset of cataracts. 9 Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados The most important physiological change, resulting in a negative impact on the presbyopic patient, is the progressive reduction in tear volume that occurs with age. Discomfort due to dryness has been found to be the primary cause of contact lens wear abandon4. Du Toit and co-workers5 found that, whereas 28% of presbyopic patients reported dryness prior to contact lens wear, 68% reported dryness after six months of lens wear. Besides, it has been noted that a reduction in tear production of 50% occurs at 50 years of age, further decreasing to 75% at 80 years. Hormonal factors, relevant in post-menopausal women, have also been reported to result in dry eye. Tear volume can be assessed with either the Schirmer tear test or the phenol red threat test. Tear quality, on the other hand, may be evaluated with the tear break-up time test, in which fluorescein is instilled to detect tear film instability and break-up. In addition, if signs are observed of Meibomian gland dysfunction or blepharitis, these conditions must first be managed prior to fitting the presbyopic patient with contact lenses. 2.2. OPTICAL COMPENSATION FOR PRESBYOPIA 2.2.1. Spectacles Spectacles are the simplest, safest and most commonly used means of correcting presbyopia. Spectacles may include glasses with a multifocal correction or glasses for reading (just near vision), depending on the needs of the patient. Nowadays, spectacles with bifocal or progressive addition lenses (PALs) are the most frequently fitted. A bifocal optical system has two points of focus: the main part of the spectacle lens contains a prescription for distance vision, while the lower portion of the lens holds the stronger near prescription, or addition, for close work. Progressive addition lenses, on the other hand, are similar to bifocal lenses, but they offer a more gradual visual transition between the two prescriptions, with no visible line between them and without losing intermediate vision. Reading spectacles are another choice, consisting in convex lenses with the suitable power between 1 and 3 dioptres. Unlike bifocals and PALs, which most people wear all day, this correction is worn only during close work. Reading spectacles are praised by users for their comfort, lack of need for special care and easy of handling. It may be noted that as the human lens continues to change until 65 years of age, the presbyopic prescription will need to be adjusted and increased over time as well. Therefore, the lenses of the glasses will need to be changed until the stabilization of presbyopia. 16 Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados The most important concern with this system is its dependence on pupil size. Paradoxically, pupillary miosis when fixing at near will decrease the percentage of light energy entering the eye the lens area devoted to near vision. Fig 2.13. Centre-distance design To illustrate possible multifocal lens designs based on the centre-distance principle, two examples are provided: Fig 2.14. Centre-distance design (Example 1) This manufacturer offers a contact lens design (Figure 2.14) in which there is the more negative power (for distance vision) at the centre of the lens, whereupon this power progressively increases toward the periphery of the lens for near vision. The fitting guide suggests that the dominant eye should wear this design in cases of myopia or low hyperopia (<1.00D). 17 Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados Conversely, the fitting guide for the following lens design (Figure 2.15) recommends wearing it in both eyes in cases of low additions (<1.75D). Thus, it may be a good alternative for myopic users (regardless of addition) if they want to enhance distance vision. However, when near vision needs to be enhanced, this lens should be worn in the dominant eye. Fig 2.15. Centre-distance design (Example 2) ii. Centre-near: the optical principle is the same described above for the centre-distance lens, although lens areas, and consequently ray paths, are inverted. Thus, it is the central part of the lens which focuses near objects and the periphery which focuses distance objects (Figure 2.16). These designs were introduced to solve the problem of pupillary contraction while working at near. Fig 2.16. Centre-near design 18 Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados Two examples of centre-near lens designs are also provided to illustrate the principle behind this type of simultaneous vision contact lenses: Fig 2.17. Centre-near design (Example 1) The manufacturer of this contact lens offers a design (Fig.2.17) in which the centre has a positive power (for near vision). As we move away from the apex of the lens to the periphery, a progressive decrease in power occurs until the distance power is reached in the periphery. It is suggested that the non-dominant eye should use this design in cases of myopia or low hyperopia (<1.00D). In cases of hyperopia >0.75 D, the fitting guide recommends wearing the same lens design in both eyes. In the second example of centre-near designs (Fig.2.18), the manufacturer recommends wearing this lens in front of the non-dominant eye in cases of advanced presbyopia (additions>2.00D). Fig 2.18. Centre-near design (Example 2) 19 Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados 2.3.3.3. Modified monovision Monovision may be considered a type of simultaneous vision, as one eye is devoted to distance and the contralateral eye to near vision. Provided that in monovision the reading addition is not too high, the depths-of-focus of each eye allow reasonable acuity to be achieved at far, intermediate and near distances. However, there may be a loss in stereopsis and increased difficulty with more critical distance and near tasks, particularly when higher reading additions are used. For these reasons a variant of monovision, called “modified monovision” has been proposed. With modified monovision (Figures 2.19 and 2.20), the dominant eye usually wears a distance-biased design, while the non-dominant eye wears a near-biased design. Modified monovision offers the advantages of monovision while also providing some multifocal function. In addition, some lens designs offer an aspheric translation zone between the near and distance zones which should allow for a certain degree of intermediate vision. Fig 2.19. Centre near aspheric Fig 2.20. Centre distance aspheric Several manufacturers and contact lens practitioners have taken advantage of the modified monovision principle to allow for some interesting combinations (Table 2.1)17: Dominant eye Non-dominant eye Rotational multifocal (centre distance) Simultaneous multifocal (centre near) Rotational multifocal (centre distance) Near single vision lens Distance single vision lens Simultaneous multifocal (centre near) Rotational multifocal (centre near small) Rotational multifocal (centre near large) Rotational multifocal (centre distance-small) Rotational multifocal (centre distance large) Table 2.1: Possible combinations resulting from the “modified monovision” principle17 20 Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados 2.3.3.4. Considerations regarding pupil diameter As noted above, all simultaneous vision lens designs rely on pupil diameter to provide the required amount of light energy for distance or near vision, depending on the visual demands of each particular task. In turn, pupil diameter varies with lighting conditions and is a vertex of the “near vision triad” involving accommodation, convergence and miosis. Furthermore it is important to take into account that pupil diameter decreases with age. Pupil diameter is normally measured in predefined illumination conditions. However, it is obvious that illumination conditions will vary in real daily life situations, resulting in different ratios of pupil and contact lens areas than those estimated in controlled conditions during lens fit assessment. Pupil diameter may be assessed with various techniques, with diverse levels of accuracy and of intrusion on normal viewing conditions. Thus, the most accurate and less intrusive methods include photography or video, whereupon, if taking advantage of infra-red radiation, it may be performed in complete darkness, allowing for the measurement of scotopic pupil diameter. The Colvard pupillometer (Oasis Medical Inc., Saint Dimas, CA, USA) is an example of such an instrument. Alternatively, pupil diameter may also be measured non-intrusively with a rule, although this method is not very accurate. Similarly, and also not very accurate and only useful for photopic lighting conditions, an easy and fast method to measure pupil diameter consists in comparing the pupil with a semicircle of known diameter as reference (Figure 2.21) Fig 2.21. Reference pupil diameters 2.3.3.5. Success with multifocal lenses There are some studies which analyse the success with multifocal lenses. Thus, in 2003, one study assessed quality of vision with both monovision and bifocal contact lenses. The findings of this study revealed that, whereas stereopsis was reduced with monovision, bifocal contact lenses resulted in an improvement in binocularity. All aspects of vision and overall patient satisfaction were superior with bifocal lenses, particularly when patients were asked about driving at night and depth perception. The authors concluded that adapted monovision wearers could be successfully refitted into bifocal lenses. Besides, bifocal lenses were preferred to monovision by most subjects after six months of use.18 In 2006 another study was conducted in which the authors fitted 38 presbyopes with no experience in presbyopic contact lens correction. They were randomized into either multifocal contact lens or monovision for one month, at which time they switched modalities and the study was repeated. At the end of the wearing time, vision was equal at distance and near for both modalities but 76% of participants preferred monovision.19 These findings, however, were in disagreement with those of a previous study in which patients wore GP monovision 21 Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados lenses for six weeks followed by six weeks in a GP aspheric multifocal. At the conclusion of this study, 75% of the participants preferred the multifocal design.20 Indeed, in several comparative studies in which patients had to make a forced choice between the two modalities, the bifocal/multifocal was preferred to monovision. A recent study from 201121 revealed the effect of visual demand, observation distance and contact lens design on the visual satisfaction of multifocal contact lens wearers. The authors concluded that a thorough exploration of each patient's habitual tasks in terms of visual demand, observation distance and time dedication could prove beneficial when selecting lens design in order to increase future visual satisfaction and wearing success. Actual pupil diameter and working distance for each patient were not evaluated, however, with tasks being classified only in terms of far, intermediate and near vision. This study included 22 presbyopic subjects who followed two 14-day trial periods in which they were alternatively and randomly fitted with two types of multifocal lenses. Subjects graded visual satisfaction with each pair of lenses and each habitual task at different times during each trial. Overall satisfaction was evaluated after completion of the two trial periods. Wearing success was determined by the percentage of subjects opting to continue multifocal lens wear and by the number of subjects still wearing their lenses six months later. Although 78 % of subjects decided to continue lens wear following the completion of the trial, only one subject was wearing them on a daily basis 6 months after the completion of the study. Insufficient quality of vision was reported as the main reason for multifocal contact lens discontinuation. Additionally, it was noted that multifocal contact lenses wear required a higher level of commitment from the patient than monofocal designs, being often associated with patients with a higher motivation. 22 Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados 3. OBJECTIVES AND HYPOTHESIS The number of wearers of multifocal contact lenses has experienced a significant growth in recent years. For this reason, it is important to evaluate their designs in order to select the best contact lens for each patient based on their visual demands. The main objective of the present study was to determine the working distance and pupil diameter of presbyopes while conducting their habitual tasks in normal lighting conditions. For this purpose, several specific goals were considered as relevant:  To determine the most common habitual tasks in a group of presbyopes.  To measure working distance and pupil diameter while participants performed their habitual task in their usual environmental conditions.  To describe some frequently employed multifocal lens designs based on the simultaneous vision principle in terms of lens areas devoted to distance, near and intermediate vision.  To explore the best lens design for each habitual task. It was the hypothesis of the present study that a better understanding of pupil parameters during habitual tasks would benefit contact lens practitioners when selecting the best lens design for each particular patient. Although actual lens fitting and follow-up visits were considered beyond the scope of the present study, that is, no conclusions shall be possible regarding changes in multifocal lens success arising from this new strategic approach based on careful preliminary measurements and detailed clinical history, it should nevertheless be evident whether pupil diameters and working distances, when measured in real life conditions, differ from those commonly explored in the contact lens office, prior to lens selection by the practitioner. 23 Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados 4. SUBJECTS AND METHODS 4.1. STUDY SAMPLE A total of 59 presbyopic subjects took part in the study, which took place in Terrassa (Spain) between October and January of 2013. Inclusion criteria were age between 45 and 65 years (inclusive), previous monofocal contact lens wearers and non-wearers. Any patients manifesting any eye disease, injury or abnormality of the cornea, strabismus or amblyopia or a clinically significant anisocoria were excluded from the study. All participants provided written informed consent after the nature of the study was explained to them (Annex I). The study was conducted in accordance with the Declaration of Helsinki tenets of 1975 (as revised in Tokyo in 2004). Given the purpose of the present study, it was critical to aim at building a sample which could be considered a good representative of the population of presbyopic patients in terms of visual demands and habitual tasks (both at home and at the workplace). Besides, it was similarly important that those tasks involved a variety of lighting conditions and working distances. 4.2. METHODS Subjects were first interviewed regarding their visual demands with the aid of an ad hoc questionnaire (Annex II) in which they indicated the number of hours per week that they allocated to two habitual tasks, at home or at the workplace, and they also reported the visual satisfaction while undertaking each of these tasks. Visual satisfaction was graded with a vertical visual analogue scale ranging from 0 to 100 mm (100 mm was defined as “maximum visual satisfaction”). Participants were also asked about their job details or main occupation and about their computer use and reading habits. Previous contact lens use was investigated, both with monofocal or multifocal lenses. Participants reporting not using multifocal lenses were inquired about the reason for not trying this type of visual correction. Similarly, past multifocal lens wearers were asked to describe the reason that led them to abandon lens wear. After completing the questionnaire, pupil diameter of each participant while conducting each of their described habitual tasks was determined. Pupillary diameter was assessed by capturing a picture with the mobile phone (Figure 4.3 and Figure 4.4), and placing a ruler under or over the eye for later reference during image analysis (Figure 4.5 and Figure 4.6). In addition, working distance was determined with a measuring tape (Figure 4.7) and the illumination that reached the pupil during each of the different tasks was measured, in lux, with a light meter (Figure 4.8). 24 Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados Fig 4.3. Image capture during real conditions (work) to determine pupil diameter Fig 4.4. Image capture during real conditions (reading) to determine pupil diameter 25 Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados Fig 4.5. Image capture of eye with reference rule to determine pupil diameter Fig 4.6. Pupil diameter measurement through digital image analysis It must be assumed that this is not the most accurate method for measuring pupil diameter. However, given the goals of the present study, it was critical to measure pupil diameter (as well as working distance and illumination) in exactly the same conditions in which each participant conducted the reported habitual tasks. Therefore, a compromise in precision was considered the lesser evil when compared with a real approach to normal conditions. Pupil diameter was later examined under photopic and scotopic conditions in the optometric practice, while conducting a routine visual examination. 32 Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados Fig. 5.2. Correlation between pupil diameter and illumination (expressed as log Illumination) Fig. 5.3. Pupil diameter (in mm) while performing 4 common habitual tasks 33 Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados Fig. 5.4. Illumination conditions (in lux) while performing 4 common habitual tasks Fig. 5.5. Working distance (in cm) while performing 3 common habitual tasks (sports is omitted as all sports involved far vision, with the exception of 2 participants) 34 Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados The analysis of the associations among the various parameters under study for each of these 4 habitual tasks uncovered some relevant and statistically significant correlations (Table 5.6). Task Variables under analysis Correlation coefficient (rho) p Computer Pupil diameter - Illumination -0.86 <0.001 Pupil diameter - Distance -0.954 <0.001 Illumination - Distance 0.887 <0.001 Sewing Hours/week - Illumination -0.768 0.001 Pupil diameter - Satisfaction 0.536 0.039 Illumination - Distance 0.574 0.025 Reading Illumination - Distance 0.619 <0.001 Sports No significant correlations Table 5.6. Correlations between study variables for each habitual task Although some of these correlations were not unexpected, for instance those regarding pupil diameter and illumination, it is interesting to note that, while using the computer, an increase in working distance also resulted in an increase in illumination, and a resulting reduction in pupil diameter. In addition, participants reporting sewing as a habitual task also noted better visual satisfaction with larger pupils. These findings, however, may be interpreted with caution as these subgroups within the study sample were probably not large enough to allow for a conclusive statistical approach. Finally, the Wilcoxon test for related samples disclosed statistically significant differences between the measured photopic and scotopic pupil diameters and those obtained while participants were conducting their habitual tasks (all p < 0.001), that is, in a significant number of participants, pupil diameter, as measured during routine visual examination, was different from actual pupil diameter while participants performed their habitual tasks. 35 Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados 6. DISCUSSION One of the aims of the present study was to investigate the different designs offered by manufacturers of simultaneous vision multifocal contact lenses. Indeed, many manufacturers produce simultaneous lens designs with rotational symmetry in which power increases (in centre near lenses) from the centre to the periphery of the lens, either in concentric steps or as a smooth transition. With this information at hand, and with the experimental findings uncovered in the study sample of presbyopic participants, the last task of this research would have been to determine which lens design had the highest probability of success for each patient, in terms of the measured pupil diameter and working distance while performing habitual tasks. Unfortunately, after contacting contact lens manufacturers (or distributors) located in Spain, it was discovered that commercial secrecy prevented them to divulge details of their lens designs and power profiles. This difficulty is not unreported in the literature. In effect, in a recent work by Plainis and colleagues15, the authors resort to advance instrumentation to measure the power profiles of 4 commonly used simultaneous vision multifocal contact lenses: Air Optix AQUA multifocal (Alcon, Fort Worth, TX, USA), PureVision multifocal (Bausch & Lomb, Rochester, NY, USA), Acuvue OASYS for Presbyopia (Vistakon, Division of Johnson & Johnson Vision Care, Jacksonville, FL, USA) and Biofinity multifocal (Cooper Vision, Fairport, NY, USA). It may be observed, from Figure 6.1 and Figure 6.2, that power profiles show considerable variations between the different brands of lenses and also with the add power of the contact lens, with all lenses under examination (except for PureVision) offering three different add powers to choose from. In that study, all these lenses had no power for distance vision. Fig. 6.1. Power profiles of Air Optix AQUA multifocal (AO) and PureVision multifocal (PV) with different add powers as measured with a Phase Focus Lens Profiler by Plainis et al15 36 Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados Fig. 6.2. Power profiles of Acuvue OASYS for Presbyopia (OASYS) and Biofinity multifocal (BF) with different add powers as measured with a Phase Focus Lens Profiler by Plainis et al15 Following a complex mathematic approach, these authors revealed that, for low add power Air Optix AQUA multifocal and PureVision multifocal, the power of the lens did not fall to zero (distance correction) until 1.9 mm from the centre of the lens, that is, a minimum pupil diameter of 3.8 mm was required for patients to take advantage of the simultaneous vision design. This value was of 3.4 mm and 4.8 mm for the high add power Air Optix AQUA multifocal and PureVision multifocal, respectively. It is therefore evident that pupil diameter measurement is critical to ensure that a particular lens design is suitable for an individual patient. A small pupil, in a centre near lens, may result in serious difficulties when using that lens for distance vision, mainly in those lens designs in which the distant vision area of the lens is located far from its geometrical centre. Similarly, a large pupil (such as may occur while driving at night), might give rise to abundant photic phenomena, such as glare, if the patient is wearing a lens design with a power profile favouring near vision over a large area of its geometry. However, even though practitioners frequently inquire patients regarding their motivation, wearing habits, expectations, type of indoor and outdoor activities, etc., it is nevertheless common practice to perform in-office measurements of pupil diameter. It may be estimated that routine pupil diameter measurements are conducted under 3500 lux of illumination for photopic conditions, and 20 lux of illumination for scotopic conditions. The present findings revealed that, when illumination was measured while participants conducted their habitual tasks in real life conditions, values were very different from those in-office values and, in 37 Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados consequence, pupil diameter, and area of theoretical lens coverage, also presented relevant differences. Pupil diameter may be considered a very dynamic parameter, notably influenced by several factors, most importantly age and illumination conditions. Changes in pupil diameter with age are depicted in Figure 6.3, from the work of Winn and co-workers22, noting a decrease in pupil diameter with age, when measurements were conducted under the same illumination conditions (actually, luminance from a 10 degree field of view stimulus was evaluated instead of illumination), as well as an overall decrease in diameter at highest levels of illumination. Fig. 6.3. Pupil diameter in different luminance conditions (the stimulus subtended a 10 degree field of view)22 In agreement with this and other previous works, the present findings revealed a statistically significant negative correlation between pupil diameter and illumination. In addition, however, pupil diameter is also governed by the “near vision triad”, that is, convergence, accommodation and miosis. Observation distance is therefore another important factor to be considered when selecting the best lens design for each patient, not only for its influence on pupil diameter, but also for the correct determination of the required add power of the lens. Indeed, working distances when using the computer or when reading were found to range from 40 to 60 cm and from 30 to 50 cm, respectively. A change from 50 to 30 cm is equivalent to a change in 1D of add power, that is, it may require a modification in lens selection, for example, from low to mid add power (in a lens design with three possible add powers). It is certainly not sufficient to ask patients whether they enjoy reading and assume that all patients read at a distance of exactly 40 cm. The present results give support to the need to perform real life measurements of pupil diameter and working distance prior to lens selection. 38 Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados It must be acknowledged that this study was not devoid of limitations. Thus, the relevance of the findings would have been improved if patients had been actual multifocal lens wearers, and had been able to grade visual satisfaction with their lenses, while performing the reported habitual tasks. This aspect of our investigation shall be the subject of a future study. Also, although the study sample was large and it was considered representative enough of the population of presbyopic patients, once subgroups were defined (such as participants reporting a particular habitual task), the number of subjects in many of these subgroups prevented any proper statistical approach to be performed to the data, thus limiting the validity of the conclusions. Finally, the main limitation of this study was not being able to correlate each individual participant with a particular lens design, given the secrecy involving actual lens parameters. 39 Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados 7. CONCLUSIONS The main findings of the present research may be summarized as follows: 1. There is a lack of information about multifocal contact lenses. 2. Multifocal contact lenses are addressed to presbyopic users and these users are people from the 45 years. So there are many different users, they can have different ages, different jobs or hobbies and different customs of lighting and working distance. It is important to take in count because all this parameters influence in the pupil diameter and in the add required. 3. The pupil diameter and working distance of two users doing a same task may be different. A difference of 20 cm is equivalent to change 1D of add power so it may require a modification in lens selection. Furthermore note that there is a relation between age and pupil size, pupil size decreases while age increases. 4. The photopic and scotopic pupil diameters measured during routine visual examination and those obtained while users were conducting their habitual tasks are different. 5. Measure the pupil diameter while participants conducted their habitual tasks is critical to ensure that a particular lens design is suitable for an individual patient. It is also important to considered observation distance to select the best lens design for each patient, it not just influence on pupil diameter, also can help to select the required add power of the lens. 40 Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados 8. ARTICLE An article based on this research, with the title of PUPIL DIAMETER, WORKING DISTANCE AND ILLUMINATION DURING HABITUAL TASKS. IMPLICATIONS FOR SIMULTANEOUS VISION CONTACT LENSES FOR PRESBYOPIA is being considered for publication at the journal Eye & Contact Lens. 41 Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados 9. REFERENCES 1. INE: Instituto Nacional de Estadística, 2010. 2. Suplemento de la revista Gaceta Óptica Mayo 2006; 404:2. 3. Facts about Presbyopia. U.S. Department of health and human services. National Institutes of Health. National Eye Institute. 4. Young G, Veys J, Pritchard N, Coleman S. A multi-center study of lapsed contact lens wearers. Ophthalmic Physiol Opt 2002; 22: 516-527. 5. Du Toit R, Situ P, Simpson T, Fonn D. The effects of six months of contact lens wear on the tear film, ocular surfaces, and symptoms of presbyopes. Optom Vis Sci 2001; 78: 455-462. 6. Evans BJW. Monovision: a review. Ophthalmic Physiol Opt 2007; 27: 417-439. 7. Jain S, Arora I, Azar DT. Success of monovision in presbyopes: review of the literature and potential applications to refractive surgery. Surv Ophthalmol 1996; 40: 491-499. 8. Collins MJ, Goode A. Interocular blur suppression and monovision. Acta Ophthalmol Scand 1994; 72: 376-380. 9. Alió JL, Chaubard JJ, Caliz A, Sala E, Patel S. Correction of presbyopia by technovision central multifocal LASIK (presbyLASIK). J Refract Surg 2006; 22: 453-460. 10. Sorbara L, Woods C. Correction of Presbyopia with GP Contact Lenses. The center for Contact Lenses Research. School of Optometry, University of Waterloo, Ontario, Canada. 2008; 18-19. 11. Sorbara L, Woods C. Correction of Presbyopia with GP Contact Lenses. The center for Contact Lenses Research. School of Optometry, University of Waterloo, Ontario, Canada. 2008; 20-21. 12. Sorbara L, Woods C. Correction of Presbyopia with GP Contact Lenses. The center for Contact Lenses Research. School of Optometry, University of Waterloo, Ontario, Canada. 2008; 22-23. 13. Plakitsi A, Charman WN. Comparison of the depths of focus with the naked eye and with three types of presbyopic contact lens correction. J Br Contact Lens Assoc 1995; 18: 119-125. 14. Legras R, Behard Y, Rouger H. Through-focus visual performance measurements and predictions with multifocal contact lenses. Vision Res 2010; 50: 1185-1193. 15. Plainis S, Atchison DA, Charman WN. Power Profiles of Multifocal Contact Lenses and Their Interpretation. Optom Vis Sci 2013; 90: 1066-1077. 48 Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados AGE (years) SEX PUPIL - PHOTOPIC CONDITIONS (mm) PUPIL - SCOTOPIC CONDITIONS (mm) TASK 1 47 0 2 5 Gym 46 1 2 5 Sewing 62 0 2 5 Pilot 49 1 2 5 Reading 50 1 2 5 Sewing 51 0 2 6 Reading 51 1 3 6 Piano 50 1 4 5 Sewing 54 0 2 5 Driving 54 1 2 5 Computer 48 1 3 6 Computer 56 0 2 5 Computer 59 1 4 6 Reading 54 0 3 6 Gym 47 0 2 6 Driving 54 0 3 5 Reading 51 1 2 6 Reading 49 1 3 5 Sewing 48 0 2 5 Computer 52 0 2 5 Theater 57 1 2 5 Reading 62 0 2 5 TV 57 0 3 5 Reading 48 0 2 5 Reading 56 1 2 5 Reading 63 1 3 6 Computer 46 0 2 5 Computer 49 1 2 6 Reading 52 1 2 6 Sewing 51 1 3 6 Computer 64 0 2 5 Home 47 0 2 4 Computer 53 1 3 6 Reading 52 0 2 5 TV 62 1 2 5 Reading 47 1 2 5 Reading 50 0 3 6 Reading 52 1 2 5 Reading 54 0 2 5 Computer 56 1 2 5 Computer 56 1 2 6 Computer 55 1 2 5 Reading 56 0 2 5 Reading 45 1 3 5 Reading 57 1 2 4 Computer 50 0 2 5 Reading 49 1 3 6 Reading 56 0 3 7 Sports 56 0 2 6 Sports 54 1 3 5 Reading 45 1 3 5 Computer 49 0 2 7 Reading 57 0 2 6 Sports 54 1 2 5 Reading 50 1 2 6 Reading 52 0 3 7 Reading 48 0 2 7 Driving 53 0 2 6 Sports 60 0 2 5 Reading 49 Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados HOURS/WEEK - TASK 1 (hours) SATISFACTION TASK 1 (From 1 to 10) PUPIL φ - TASK 1 (mm) ILLUMINANCE - TASK 1 (lux) 50 9 4 404 8 8 4 285 15 8 4 3300 5 9 3 646 3 2 3 3300 4 1 3 3300 6 7 4 3300 3 9 3 3300 20 9 2 1850 22 7 3 217 40 10 3 217 56 9 4 217 10 6 4 217 12 10 3 217 25 7 2 1850 18 5 3 217 21 5 3 217 15 5 3 217 40 6 2 3400 10 9 4 120 15 6 3 217 20 8 5 2,7 20 7 3 217 18 6 3 3400 21 6 3 217 25 8 2 3400 25 8 2 3400 20 9 3 217 15 7 3 217 50 8 2 3400 14 7 2 1850 42 8 2 3400 6 8 3 217 10 9 5 2,7 14 5 3 217 7 6 3 3400 16 7 3 3400 7 5 3 217 7 7 2 3400 15 7 2 3400 40 6 2 3400 10 9 4 217 7 6 3 217 10 5 3 3400 50 8 2 3400 6 8 3 217 14 6 3 3400 3 10 3 1850 21 9 3 217 10 7 4 217 30 8 2 3400 10 5 3 217 8 10 2 1850 14 9 3 217 10 6 3 217 30 8 4 217 40 9 3 1850 6 10 5 250 10 9 3 3300 50 Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados DISTANCE - TASK 1 (mm) TASK 2 HOURS/WEEK - TASK 2 (hours) SATISFACTION TASK 2 (From 1 to 10) 6000 Reading 4 7 40 Piano 4 9 50 Sports 6 9 40 Sewing 4 7 35 Home 14 10 40 Computer 3 6 50 Cooking 15 9 33 Computer 30 9 6000 Computer 14 6 40 Reading 5 7 40 Sports 5 10 40 Driving 30 9 40 Computer 40 6 40 Reading 48 8 6000 Writing 12 4 33 TV 10 8 40 Sewing 10 3 33 Home 30 7 60 Sports 10 8 6000 Reading 9 7 33 Sewing 25 4 200 Home 40 6 33 TV 10 8 40 Driving 30 8 33 Sewing 14 5 60 Reading 14 6 60 Sports 14 9 33 Sewing 30 7 33 Cooking 20 8 60 Drawing 20 8 6000 Reading 10 7 60 Sports 5 9 33 Sewing 6 7 200 Playing Cards 8 6 33 Sewing 20 4 40 Sewing 15 8 40 Sports 14 9 33 Computer 30 7 60 Restoring Furniture 10 6 60 Sports 15 9 60 Reading 20 5 50 Computer 45 7 33 Reading 14 6 40 Sports 14 9 60 Sewing 7 7 33 Sports 15 10 40 Computer 7 9 6000 Computer 15 5 6000 Sports 4 9 33 Sports 6 10 60 Sports 5 10 33 Sports 8 10 6000 Computer 40 6 33 Sports 4 9 33 Sewing 7 4 45 TV 15 8 6000 Playing Cards 8 5 6000 Reading 10 6 40 Restoring Furniture 30 6 51 Facultat d’Òptica i Optometria de Terrassa © Universitat Politècnica de Catalunya, año 2015. Todos los derechos reservados PUPIL φ - TASK 2 (mm) ILLUMINANCE - TASK 2 (lux) DISTANCE - TASK 2 (mm) 3 120 30 4 285 60 4 285 60 4 3300 35 3 3300 50 2 3400 60 3 217 60 4 3400 45 3 3300 40 3 217 33 3 217 6000 2 1850 6000 5 120 50 4 285 40 4 3400 45 5 2,7 200 3 217 33 4 217 60 2 1850 6000 3 217 33 3 217 33 3 330 40 5 2,7 200 2 1850 6000 3 217 33 3 3400 40 3 217 6000 3 217 33 4 217 60 3 3400 50 3 217 33 3 217 6000 4 3400 35 4 217 55 3 217 33 4 217 60 4 217 6000 2 3400 60 3 3400 30 2 1850 6000 3 3400 40 2 3400 60 5 217 50 4 217 6000 3 217 33 3 217 6000 2 3400 60 2 3400 60 3 217 6000 3 217 6000 3 1850 300 2 1850 6000 2 3400 60 3 217 6000 3 217 33 3 2,7 300 5 217 42 4 217 36 3 3400 50