Chylack Classification Essay

Encouraging online participation?

Suzanne Ho
School of Design
Curtin University of Technology
How do you encourage or facilitate online participation? What constitutes effective participation? This paper firstly examines selected theories about encouraging effective online participation and secondly, meta-surveys a range of qualitative and quantitative methods for assessing the effectiveness of students' online participation. The author aims to make informed recommendations on strategies to encourage online participation and relevant criteria for assessing participation in online discussions, based on an extensive literature review. Within the scope of this paper, online participation will be analysed in the context of discussions within online learning environments only.

Introduction

Online learning software packages often include online discussion tools (Comparison of online course delivery software products, 1999). However, does access to these tools and the knowledge that one's participation will be assessed, encourage students' online participation? Where discussion is considered a necessary learning method (Maznevski, 1996), the challenge is to facilitate effective student participation. Learning through discussion and interaction is an aspect of Bandura's (1971) "social learning theory" - where understanding is acquired through modelling the behaviours, attitudes, and reactions of others, with participation as the process where learners are actively engaged in online, text based communication (Davis, 1999). Effective participation occurs where this communication facilitates the development of a deep understanding of the material through sharing and critically evaluating ideas, and where connections are made between elements of the learning material (Klemm and Snell, 1996).

In analysing how students approach learning, Laurillard (1993) identified the "Conversational framework" - where learning is mediated by the educator who persuades students to make sense of various phenomena using the accepted norms of their discipline (Laurillard as cited in Entwistle, 1995). For many educators, "courses must feature ongoing and substantive interaction" (Mabrito, 2000), articulating the ideas of Bandura, Vygotsky, Piaget, Dewey and Pask. Vygotsky (1978) states that social interaction plays a fundamental role in the development of cognition. Collaborative learning enables students to analyse, synthesise and evaluate ideas cooperatively. Vygotsky's theory is complementary to Bandura's (1971) social learning, and "situated learning" theory - where learning is an act of participation within communities of practice (Lave and Wenger, 1991). Piaget (1970) maintains that cognitive structures change through assimilation and accommodation. There are connections between the theories of Piaget and Bruner (1966), where educator and learner are engaged in active dialogue and information is arranged in a spiral manner so that the learner continually builds upon their existing knowledge. The fundamental idea of Pask's "conversation theory" (1975) is that learning occurs through conversations which serve to clarify and formulate understanding.

Ultimately, proponents view discussion as integral to developing understanding and facilitating good learning outcomes. Decisions about incorporating online discussions into curricula should not made lightly (Hopper and Harmon, 2000). Bunker and Ellis (2001) outline seven reasons (relating to the theories discussed) for making online discussions part of a learning program. Entwistle (1995) cautions that success depends on the context and the individuals concerned, emphasising the need to first identify teaching goals, students' prior knowledge and their intellectual stage of development, to enable the selection of appropriate teaching methods.

Contextualising effective online participation

Online discussions can be structured with defined topics and procedures or allow students to 'freely' express ideas. The structure of discussions and facilitation of participation vary according to the norms of specific disciplines. Anderson (as cited in Entwistle, 1995) describes excellence in Social Science teaching as facilitating a "climate in which misunderstanding is accepted as a necessary step... towards understanding". Often in postgraduate level discussions, the emphasis is on peer interaction and challenging hegemony. However, multiple interpretations cannot be accepted in the case of factually incorrect explanations (Jones et alia, 2000). Thus discussion can act as the locus of shared knowledge, or as a forum within which diverse beliefs and values are negotiated. Nevertheless, an online discussion brings practical relevance to a unit of study because it approximates professional teamwork and collaborative writing (Mabrito, 2001). Some educators assert that collaboration and participation increases online, because communication is more student centred and egalitarian than face to face situations (Brown, 1997; Bunker and Ellis, 2001). Such arguments assume that the medium is of paramount importance, and ignore critical features such as the aim of online discussions in a particular teaching context and how the discussion is structured (Entwistle, 1995; Gosper, undated).

Of the fifteen research articles on analysing participation surveyed, eight utilise Bloom's Taxonomy (1956) to interpret online discussions. Participation is determined by reading and categorising messages using six objectives - knowledge, comprehension, application, analysis, synthesis and evaluation (Gearhard, 1999). Knowledge requires basic recall of facts, procedures or rules. Comprehension is demonstrated through the interpretation of information. Application requires information to be used in a different context to that where it was learnt. Analysis is demonstrated through the discrimination of information. Synthesis requires combining information to find solutions to unfamiliar problems and evaluation involves the formulation of judgements about theories and methods for a given purpose. Levenburg and Major (2000) found a direct and positive relationship between the amount of time students spent in online discussions and their achievement of course objectives because they utilised higher level cognitive skills - analysis, synthesis and evaluation. This assumes that learners read and interpret postings, as well as formulate and articulate their own opinions. Without focus, high levels of participation creates confusion and information overload for learners (Muirhead, 2000). Furthermore "participation inequality" (Nielsen, 1997) diminishes the intellectual rigour of the discussions (Klemm and Snell, 1996) and the learning experience for students (Jones et al, 2000).

Eleven of the fifteen research articles use content analysis to study online discussions. McKenzie and Murphy (2000) and McLoughlin and Luca (1999) utilise Henri's content analysis model, which is based on the quality of messages and focuses on participation levels within the group. Discussions are analysed according to four educational dimensions - interactive, social, cognitive and meta-cognitive - as well as the frequency, structure and type of online participation. The content analysis methods in Jones et alia (2000), Lindeman (2001), Nelson (1998), Northcote and Kendle (2000) and Owen (2000), have similarities to both Henri's and Bloom's models. All approaches involve classifying comments from discussion transcripts. Content analysis can present implementation problems, McLoughlin and Luca (1999) found Henri's model unsuitable to constructivist student centred discussions - a view supported by McKenzie and Murphy (2000). Also, content analysis is subjective and interpretations may not be easily justified when challenged, limiting the validity of evaluation. McKenzie and Murphy (2000) found difficulties in assessing levels of critical thinking and meta-cognition because of Henri's vague description of their attributes. Frequency and duration of participation can be obtained using online learning software packages (Landon, 2000), and when used with content analysis - provides a reasonably accurate interpretation of participation.

Facilitating online participation

Scaffolding or structuring is used by numerous educators to facilitate online participation (Klemm and Snell, 1996; Owen, 2000). Morgan (2000) cautions against over-structuring to the point of limiting communication to "a set of serial monologues" and proposes a social argument framework. This reflects an experiential and situated learning approach, where "arguments... are subject designed experiments [to] try out hypotheses and evaluate results " (Willard, as cited in Morgan, 2000).

Another technique is to negotiate online guidelines with students' (Dereshiwsky, 2001). Explaining the expected level of participation, acceptable mode of communication and providing constructive feedback are some of the strategies to facilitate online participation (Muirhead, 2000). Other approaches include logic structures or concept maps, as a stimulus for discussion (Klemm and Snell, 1996) and social or group contracts (Severn, 1998). Concept maps can help students to define their educational goals, as well as stimulating group discussions. Group contracts enable students and educators to develop a formal, written agreement about learning objectives, assessment procedures and measures, and methods of conflict resolution (Murphy et alia, 2000).

Levenburg and Major (2000) identify two reasons for assessing participation - to recognise students' workload and time commitment, and to encourage students to participate. Maznevski (1996) finds participation assessment useful - behavioural indicators can be evaluated more objectively than personality traits, such as enthusiasm, and can be assessed at frequent intervals, unlike final output. Schwartz and White, as cited in Dereshiwsky (2001) recommend that assessment be directed towards the informational needs of students and avoid focusing on individual personalities. Nelson (1998), Maznevski (1996) and Lindeman (2001) use behavioural indicators as evaluation criteria, in fact, of the fourteen articles on assessing online participation surveyed, all recommend the use of evaluation criteria. The benefits include providing guidelines for learning outcomes and quality of work - thus aligning learners and educators towards similar goals (Jones et alia, 2001). Dennen (2000) found that evaluation criteria contributed to students' extrinsic motivation and clarified tasks and deadlines, improving their performance and learning outcomes. However, Barrie et alia (1999) emphasise the need for educators to have a shared understanding - inconsistent and multiple interpretations of evaluation criteria creates difficulty in providing consistent advice to students about using criteria to direct their learning.

Some educators award grades for participation (Muirhead, 2000; Mabrito, 2000), based on predetermined standards, rather than in comparison to the performance of other students (Morgan, 2000; Nelson, 1998). Barnett and Maznevski (1996) use interim feedback, to provide students with options on improving participation, including increasing the intellectual depth of comments through critical analysis, and responding to peers' comments.

Both Davis (1999) and Lacoss and Chylack (1998) state that awarding grades for participation does not facilitate good learning outcomes. Students do not perceive "forced participation rules" to be of value, because students are "just talking for credit" (Lacoss and Chylack, 1998). Students are motivated to participate in discussions where free conversation is encouraged, as opposed to "passive answers" to educator directed questions - a concern shared by Davis (1999). Moreover, participation grades disadvantage introverted students (Davis, 1999). However, neither researcher paper present compelling empirical evidence to support their claims - Davis's (1999) contentions are reported without supporting research, and Lacoss and Chylack's study (1998) consisted of only nine students and it is unclear how they were selected. Further research into the effects of assessment on participation levels could help identify factors affecting students' motivation to participate in discussions.

The decision to grade participation will depend on the aims of the online discussions (Gosper, undated). Stecher et alia (1997) state that those who choose to participate, are often more engaged in the learning experience. Voluntary participation indicates a commitment to the task and often signals a high motivation to do well. On the other hand, Hallett and Cummings (as cited in Muirhead, 2000) found that students did not participate in online discussions beyond the assessed tasks. Also, compulsory participation can provide useful results for comparison - as a performance and accountability measure within the learning program (Stecher et alia, 1997).

Conclusion

I believe the critical issue in online discussions is cooperation between educators and students. Extreme individualism and a refusal to perform within accepted norms can de-rail online discussions. Not surprisingly then, all the reviewed authors embrace collaboration and interaction. However, what is not clear is whether students place similar value on these activities. More pre and post testing of attitudes of students towards collaboration and interaction would provide their perspective on the relevance of discussion in facilitating good learning outcomes.

Of the material on online discussion reviewed, all authors subscribe to the idea structuring assists students in maximising learning outcomes. The level of structuring depends on the appropriate discourse within a discipline. The question of whether online participation assessment stimulates participation is yet to be answered with certainty. I concur with Entwistle (1995) that planning prior to course commencement is crucial to ensure pedagogical and technical goals are met. Further experiments in the use of group learning contracts and concept maps to guide students will allow for more accurate comparisons between structuring techniques.

Usage statistics and content analysis are the only assessment procedures proposed in the material surveyed. McKenzie and Murphy's study (2000) involved thirty-eight participants, the intricacy of content analysis seems unfeasible for larger classes. Content analysis presents a considerable increase in workload for educators. Peer assessed content analysis would simply shift this workload to students, although Zariski (1996) suggests that peer assessment immerses students in "the standards by which relevant and valuable contributions to disciplinary knowledge are identified". I propose that personal reflection tasks requiring students to evaluate their participation against the aims of the online discussion, perform similar functions to content analysis. Assessing this would be less burdensome for educators and has the added benefit of promoting students' deeper learning through synthesis and reflection.

References

Bandura, A. (1971). Social learning theory. New York: General Learning Press.

Barrie, S. et al. (1999). Qualitatively different conceptions of criteria used to assess student learning. [viewed 7 Jul 2001] http://www.aare.edu.au/99pap/bre99209.htm

Barnett, M. A. (Date unavailable). Encouraging students' participation in discussions. [viewed 7 Jul 2001 at http://minerva.acc.virginia.edu:80/~trc/Encourage.html] [verified 17 Dec 2001 at http://trc.virginia.edu/tc/1999/Encouraging.htm]

Bloom, B. (1956). Taxonomy of educational objectives: The classification of educational goals. Handbook I, Cognitive domain. New York: Longman

Brown, A. (1997). Designing for learning: What are the essential features of an effective online course? Australian Journal of Educational Technology, 13 (2), 115-126. http://www.ascilite.org.au/ajet/ajet13/brown.html

Bruner, J. (1966). Toward a theory of instruction. Cambridge, Massachusetts: Harvard University Press.

Bunker, A. and Ellis, R. (2001). Using bulletin boards for learning: What do staff and students need to know in order to use boards effectively? In A. Herrmann and M. M. Kulski (Eds), Expanding Horizons in Teaching and Learning. Proceedings of the 10th Annual Teaching Learning Forum, 7-9 February 2001. Perth: Curtin University of Technology. http://lsn.curtin.edu.au/tlf/tlf2001/bunker.html

Comparison of online course delivery software products (1999). [viewed 24 Sep 2001] http://www.marshall.edu/it/cit/webct/compare/index.htm

Davies, J. (1999). Early history of research on group processes. [viewed 24 Sep 2001] http://www.ualberta.ca/~jedavies/edse502/theory-history.htm

Davis, B. G. (1999). Encouraging student participation in discussion. [viewed 21 Aug 2001] http://www.uga.berkeley.edu/sled/bgd/participation.html

Dennen, V. P. (2000). Task structuring for online problem based learning: A case study. Educational Technology & Society, 3(3). [viewed 16 Jun 2001] http://ifets.ieee.org/periodical/vol_3_2000/d08.html

Dereshiwsky, M. I. (2001). 'A' is for assessment: Identifying online assessment practices and perceptions. Education at a Distance, 15(1). [viewed 7 Jul 2001] http://www.usdla.org/ED_magazine/illuminactive/JAN01_Issue/article02.html

Entwistle, N. (1995). The use of research on student learning in quality assessment. [viewed 21 Aug 2001] http://www.lgu.ac.uk/deliberations/ocsd-pubs/islass-entwistle.html

Gearhard, (1999). Assessment in online course: A case study. [viewed 7 Jul 2001] http://homepages.dsu.edu/gearhard/course_assessment.htm

Gosper, M. (undated). Assessment of online participation: Summary of the issues raised by the CFLTOM group. [viewed 4 Oct 2001] http://online.mq.edu.au/pub/CFLTOM/assess.html

Hopper, K. and Harmon, S. (2000). A multiple-case study of exemplary Internet courses. Education at a Distance. [viewed 20 Apr 2001] http://www.usdla.org/ED_magazine/illuminactive/SEP00_Issue/PDF/EdMagazine_SEP00.pdf

Jones, A. et al. (2000). Conferencing in communities of learners: Examples from social history and science communication. Educational Technology & Society, 3(3). [viewed 16 Jun 2001] http://ifets.ieee.org/periodical/vol_3_2000/c02.html

Kearsley, G. (2001). Explorations in learning and instruction: The theory into practice database. [viewed 21 Aug 2001] http://tip.psychology.org/index.html

Klemm, W. R. and Snell, J. R. (1996). Enriching computer-mediated group learning by coupling constructivism with collaborative learning. Journal of Instructional Science and Technology, 1(2). [verified 21 Aug 2001] http://www.usq.edu.au/electpub/e-jist/docs/old/vol1no2/article1.htm

Lacoss, J. and Chylack, J. (1998). What makes a discussion section productive? [viewed 7 Jul 2001 at http://minerva.acc.Virginia.EDU:80/~trc/discprod.htm] [verified 17 Dec 2001 at http://trc.virginia.edu/tc/1998/Discussion.htm]

Landon, B. (2000). Online educational delivery applications: A web tool for comparative analysis. [viewed 24 Sep 2001] http://www.c2t2.ca/landonline/compare2.html [revised URL 19 Oct 2002] http://www.edutools.info/

Laurillard, D. (1993). Rethinking university teaching. London: Routledge.

Lave, J. and Wenger, E. (1991). Situated learning: Legitimate peripheral participation. Cambridge, UK: Cambridge University Press.

Levenburg, N. and Major, H. (2000). Motivating the online learner: The effect of frequency of online postings and time spent online on achievement of learning goals and objectives. [viewed 16 Sep 2001] http://as1.ipfw.edu/2000tohe/papers/Levenburg/levenburg.htm

Lindeman, M. (2001). Student assessment in online courses: discussion rubric. [viewed 24 Sep 2001] http://illinois.online.uillinois.edu/online/assessment/discussionRubric.html

Mabrito, M. (2000). Facilitating and evaluating student interaction in an online business writing course. [viewed 24 Sep 2001] http://as1.ipfw.edu/2000tohe/papers/mabrito.htm

Maznevski, M. (1996). Grading class participation. [viewed 7 Jul 2001 at http://www.virginia.edu/~trc/tcgpart.htm] [verified 17 Dec 2001 at http://trc.virginia.edu/tc/1996/Grading.htm]

McLoughlin, C. and Luca, J. (1999). Lonely outpourings or reasoned dialogue? An analysis of text-based conferencing as a tool to support learning. Proceedings ASCILITE '99. [viewed 2 Aug 2001] http://www.ascilite.org.au/conferences/brisbane99/papers/mcloughlinluca.pdf

McKenzie, W. and Murphy, D. (2000). "I hope this goes somewhere": Evaluation of an online discussion group. Australian Journal of Educational Technology, 16 (3), 239-257. http://www.ascilite.org.au/ajet/ajet16/mckenzie.html

Morgan, M. (2000). Guiding online discussions: A social argument framework. [viewed 10 Apr 2001] http://as1.ipfw.edu/2000tohe/papers/morgan.htm

Muirhead, B. (2000). Enhancing social interaction in computer-mediated distance education. [viewed 5 May 2001] http://grouper.ieee.org/groups/ltsc/ifets/discussions/discuss_sept2000.html

Murphy, K. et al. (2000). Role of contracts in enhancing community building in web courses. Educational Technology and Society, 3(3). [viewed 7 Jul 2001] http://ifets.ieee.org/periodical/vol_3_2000/e03.html

Nelson, G. (1998). Online evaluation: Multiple choice, discussion questions, essay and authentic projects. [viewed 16 May 2001] http://leahi.kcc.hawaii.edu/org/tcon98/paper/nelson.html

Nielsen, J. (1997). Community is dead; long live mega-collaboration. [viewed 7 Apr 2001] http://www.useit.com/alertbox/9708b.html

Northcote, M. and Kendle, A. (2001). Communication skills for online students: An evaluation of a website. In A. Herrmann and M. M. Kulski (Eds), Expanding Horizons in Teaching and Learning. Proceedings of the 10th Annual Teaching Learning Forum, 7-9 February 2001. Perth: Curtin University of Technology. http://lsn.curtin.edu.au/tlf/tlf2001/northcote1.html

Owen, M. (2000). Structure and discourse in a telematic learning environment. Educational Technology & Society, 3 (3). [viewed 20 Apr 2001] http://ifets.ieee.org/periodical/vol_3_2000/b04.html

Pask, G. (1975). Conversation, cognition, and learning. New York: Elsevier.

Peat, M. (2000). Online assessment: The use of web based self assessment materials to support self directed learning. In A. Herrmann and M.M. Kulski (Eds), Flexible Futures in Tertiary Teaching. Proceedings of the 9th Annual Teaching Learning Forum, 2-4 February 2000. Perth: Curtin University of Technology. http://lsn.curtin.edu.au/tlf/tlf2000/peat.html

Piaget, J. (1970). The science of education and the psychology of the child. New York: Grossman.

Severn, K. (1998). Group learning contracts. [viewed 7 Jul 2001] http://disted.tamu.edu:8000/classes/glcontracts.html

Stecher, B. et al. (1997). Using alternative assessments in vocational education. [viewed 7 Jul 2001] http://nccte.com/publications/ncrve/mds-09xx/mds-946.html

Vygotsky, L. (1978). Mind in society. Cambridge, Massachusetts: Harvard University Press.

Zariski, A. (1996). Student peer assessment in tertiary education: Promise, perils and practice. In Abbott, J. and Willcoxson, L. (Eds), Teaching and Learning Within and Across Disciplines, p189-200. Proceedings of the 5th Annual Teaching Learning Forum, Murdoch University, February 1996. Perth: Murdoch University. http://lsn.curtin.edu.au/tlf/tlf1996/zariski.html

Author: Suzanne Ho, Lecturer, Curtin University of Technology. Email: h_suzanne@iinet.net.au

Please cite as: Ho, S. (2002). Encouraging online participation? In Focusing on the Student. Proceedings of the 11th Annual Teaching Learning Forum, 5-6 February 2002. Perth: Edith Cowan University. http://lsn.curtin.edu.au/tlf/tlf2002/ho.html


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Created 18 Dec 2001. Last revision: 19 Oct 2002. HTML: Roger Atkinson [ rjatkinson@bigpond.com ]

1. Introduction

Visual impairment and blindness are important issues in public health systems around the world. Visual impairment is defined as a corrected visual acuity of 6/18 or worse in the better-seeing eye, and is estimated to affect approximately 285 million individuals worldwide [1]. Blindness is believed to affect 39 million of the total visually impaired population, and is defined as a corrected visual acuity of 3/60 or worse in the better-seeing eye [2]. The global issue of visual impairment and blindness is felt in New Zealand with close to 125,000 New Zealanders aged 40 or over (6.1% of the population in that age group) facing a form of visual impairment [3]. Of this population, 12,000 New Zealanders suffer from blindness and 86% of these cases occur among individuals aged 70 or over. The number of people aged 40 and over suffering from visual impairment is expected to rise to 174,000 by 2020, and those suffering from blindness will rise to 18,300 [1,2].

There are three primary causes of visual impairment, including: cataracts (CAT), age-related macular degeneration (AMD), and glaucoma (GLA) [1]. These three ocular diseases induce damage to the eye through mechanisms of oxidative stress [3]. The pathogenesis of CAT is poorly understood; however, oxidative stress appears to aid the progression of age-related cataracts by facilitating damage to cellular components and accumulating advanced glycation end products (AGEs). AGEs induce conformational changes within the lens, causing increased opacity. With regards to AMD, patients with AMD exhibited a greater amount of oxidative modifications to proteins and DNA in the Bruch’s membrane, drusen, and retinal pigment epithelium compared with age-matched controls. Human retinal pigment epithelium cells exposed to a regimen of reactive oxygen species showed an increased concentration of drusen, which are associated with a poor AMD prognosis. Oxidative stress may have a role in the pathogenesis of GLA, through degradation of the trabecular network, or through direct damage to the retinol ganglion cells. Degradation of the trabecular meshwork results in increased intraocular pressure due to a build-up of aqueous humour. An in-depth discussion of the pathophysiology of oxidative stress and ocular disease (CAT, AMD and GLA) is beyond the scope of this publication, and is discussed elsewhere [3].

Antioxidants represent the first line of defence against oxidative stress and are obtained through the diet and produced internally [3]. In the eye, the major antioxidants that have a protective role are ascorbic acid, reduced glutathione, and superoxide dismutase-catalase [3]. Ascorbic acid is found in high concentrations in various areas that include the cornea, central corneal epithelium, lachrymal film, vitreous humour and aqueous humour [3], suggesting an important role in antioxidant protection in ocular health.

Early research by Cao and colleagues [4] suggested that the plasma antioxidant capacity can be increased with consumption of a diet rich in sources of antioxidants, such as fruit and vegetables. The Age-Related Eye Disease Study (AREDS 1 and 2) clearly demonstrated the ability of antioxidant therapy to reduce the progression of AMD by 25% [5]. Although diets rich in antioxidants have been identified in several studies to reduce the incidence of oxidative stress-related eye diseases, various antioxidant supplement studies provided conflicting findings [6,7,8,9]. In contrast, the intake of other food groups such as meat and related micronutrients such as cholesterol has been identified in various studies to increase the risk of oxidative stress-related eye conditions [10,11,12,13]. The impact of dietary antioxidant intake on the risk of oxidative stress-related eye diseases has been examined previously [13], but typically the studies addressed the effect of antioxidant supplements or fruit and vegetables in isolation, rather than the total dietary intake [14].

With regards to CAT, the evaluation of the literature indicates a higher dietary consumption of fruit and vegetables and vitamin C (including supplementation) appears to be associated with the most consistent risk reduction [13,14]. Vitamin E dietary intake and supplementation was also consistent with risk reduction in the majority of studies; however, findings on vitamin E supplementation suggested no observed differences in the rate of cataract extraction and lens characteristics between groups [5]. Higher dietary intakes of meat conversely appeared to increase the risk of CAT. With regards to vitamin A, findings by Theodoropoulou and colleagues [13] identified a harmful association (OR = 1.47) with higher intakes of retinol and a protective association with carotene (OR = 0.56). However, it may be possible that the harmful association identified with retinol may be related to dietary meat intake as retinol is the form of vitamin A found in animal products such as liver, kidneys, and eggs, and dietary meat intake was further identified in this study to increase the risk of CAT (OR 1.46).

Far less research has been conducted on AMD, with currently little evidence that dietary intake of fruit and vegetables or dietary antioxidants influence disease risk [3]. Human retinal pigment epithelium cells exposed to a regimen of reactive oxygen species showed an increased concentration of drusen, which are associated with a poor AMD prognosis [15,16]. The dietary intake of meat, in contrast, appeared to increase the risk of AMD when consumed frequently and in large quantities [12].

Oxidative stress is thought to degrade the trabecular network or cause damage to the retinol ganglion cells. Degradation of the trabecular meshwork results in increased intraocular pressure due to a build-up of aqueous humour [16]. However, due to the low number of published studies, the evidence regarding the prevention of GLA through higher consumption of antioxidant supplements and/or vegetables and fruit is currently unclear [3].

The majority of studies investigating the effect of diet on ocular disease incidence are conducted in European countries, and our aim was to study the association in a country that typically follows a Western diet.

2. Materials and Methods

A case-control study design was conducted to investigate the impact of dietary intake on the outcome of oxidative stress related eye-conditions: glaucoma, cataracts, and age-related macular degeneration within the New Zealand population. Participants with and without ocular disease were invited to complete a nutritional survey. Our study examined the association between the intake of specific food items, food groups, and micronutrients in the diet with ocular disease diagnosis.

Participants were sought from the University of Auckland Optometry and Vision science, and Hearing Tinnitus clinic database. Clients of the optometry clinic were designated as our sample case population, while clients of the hearing and tinnitus clinic were designated as our sample control population. Designation of hearing and tinnitus clients as our control population was as they were best matched for age, ethnicity, and population base.

Eligible participants were identified by clinic administrative staff by extending invites to clients aged 18 and over who had attended either clinic in the past 12–18 months. Optometry administrative staff further contacted clients who met the criteria above and asked for consent to be contacted by the researcher. A total of 588 eligible clients from the optometry clinic, and 522 from the hearing and tinnitus clinic were identified and contacted regarding the study. The researchers did not participate in the sampling process, to prevent coercion.

A total of 1110 letters were sent to identified participants comprised of: an invitation from the overall clinic manager, an invitation from the optometry department, participants information sheet, consent form, dietary intake survey including demographic questions, and a pre-paid return envelope. The research team collated the invitation packs for clinic staff to post. Participants were able to respond by sending completed forms through the pre-paid return envelope, or through an electronic version of the survey [17] with a link available on the information sheet.

A total of 280 responses were received after a one month period coinciding with the given deadline for submissions to be eligible to enter a prize draw. This is equivalent to a response rate of 25%. Of the 280 responses, 53 were excluded due to either: a lack of consent form, incomplete forms, or incorrectly completed forms. 227 responses were examined, and of this 149 participants self-reported as controls, while 78 participants self-reported as cases. Participants were classified as either a control or a case based on their response to the question “Do you currently, or have you ever required medical assistance for any eye related diseases?” Those responding with “no” were classified as controls and their validity was not further investigated. Those responding with “yes” were classified as cases and were further investigated by examining their clinical records and obtaining their visual acuity and ocular diagnosis. Those specifying yes but did not meet the case criteria were excluded. As a result a further 36 people were excluded, giving us a final case population of 42 people. Participant surveys and optometry files (if required) were recorded together and coded sequentially (i.e., the first completed participant will be coded as 1) to maintain anonymity.

Cases were any participant diagnosed with either: cataracts, age-related macular degeneration, primary open-angle glaucoma, or a combination of the three. Cases should have had no previous ocular surgery in both eyes (with the exception of cataract surgery). Although visual acuity score was obtained, it was not part of the exclusion criteria as removal of participants who did not meet the cut off would have impacted the associations derived from our research.

Controls were identified as participants with no prior medical conditions or treatments related to oxidative stress related eye conditions, or previous ocular surgeries. Controls were excluded if they had history of medical conditions or treatments known to be related to ocular conditions in the past. For the current study we chose to invite all clinic participants over a period of 12 to 18 months.

This study was approved by the University of Auckland Human Participants Ethics Committee on the 17th of February 2015 for three years, and has been performed to the ethical standards. Written informed consent was obtained from study participants.

2.1. Dietary Intake Questionnaire

All cases and controls completed a semi-quantitative food-frequency questionnaire; either by hand or electronically. The dietary questionnaire asked participants to indicate their average frequency of consumption of 31 food items or beverages per day, per week, per month, per year, and never. The questionnaire design was based on a prior study performed on the Australian population, examining the reliability of a 19-item food frequency questionnaire in assessing dietary antioxidant intake on health outcomes [18]. Meat and nuts are grouped together in the questionnaire, as major sources of protein. The questionnaire was modified alongside the New Zealand Adult Nutrition Survey, adding 13 more food items that were more commonly consumed in the New Zealand population [19]. The food items added/modified were green beans, oranges, mushrooms, potatoes, kumara, tea, coffee, white bread, wholemeal bread, alcohol, fish oil, multivitamins and other supplements. A pilot study was conducted on the final questionnaire of similar age to the clinic attendees for verification of comprehension of the New Zealand adapted version of the antioxidant questionnaire. Participants were correctly able to identify additional food and supplement items.

2.2. Data Entry

For purposes of statistical analysis, the frequency of consumption of different food items was quantified in terms of the number of times a food item was consumed per month. Therefore daily consumption was multiplied by 30, weekly consumption was multiplied by four, yearly consumption was divided by 12 and foods never consumed were given a value of 0. Food items were considered individually, and as groups as seen in other similar nutritional epidemiological [19]. Individual values for monthly consumption were added and the sums were approximately distributed into quintiles, based on the distribution of the entire study population. The food groups that were formed include; Meat and nuts, fruit and vegetables, dairy, breads and cereals, non-alcoholic beverages, alcohol, oil and added lipids, and supplements. Meat and nuts included: eggs, red meat, chicken, liver, kidney, nuts and seeds. Fruit and vegetables included: oranges, carrots, pumpkin, spinach, raw tomatoes, green beans, mushrooms, potatoes and kumara. Dairy included: skim or whole milk, cheese and yoghurt. Breads and cereals included: breakfast cereals, white bread and wholemeal bread. Non-alcoholic beverages included: tea and coffee. Alcohol as a group contained only alcohol. Oil and added lipids included: margarine and vegetable oils. Supplements included: fish oil, multivitamins, other vitamin supplements, and any other supplements. Specific items such as oil or added lipids were also considered individually due to the hypothesis of possible specific importance. Fats and lipids were labelled macronutrients, all remaining nutrients were labelled micronutrients including cholesterol.

Nutrient intakes for participants were estimated by multiplying the nutrient contents of the listed portion size for each specified food item by the frequency that the food item was consumed and summing the food items. The portion sizes specified were based off an earlier study in the Australian population examining the validity of a short food frequency questionnaire on ocular research [18]. The micronutrients examined in this analysis were retinol, β-carotene, vitamin C and vitamin E (α-tocopherol equivalents) as well as cholesterol. Values for the micronutrients per portion size were determined by the Foodworks (Xyris Ltd, 7th edition, Australia) dietary analysis software. Flavonoid intake was examined using data provided by the United States department of agriculture database for the flavonoid content of selected foods [20]. Flavonoid content from the classes: flavan-3-ols, flavones, flavonols, flavanones and anthocyanidins, were totaled for oranges, spinach and tea individually, and multiplied by their respective portion sizes and average monthly consumption per participant. Total flavonoid content was then determined by summating the three items. Oranges, spinach and tea were chosen as primary determinants of flavonoid content as they had the highest concentration of flavonoid per 100 mg.

2.3. Statistical Methods

Univariate analyses were initially performed to compare the frequency of intake distribution between the cases and controls by marginal quintiles of intake. We examined the association between dietary intake and glaucoma, age-related macular degeneration and cataracts by multiple logistic regression models. We controlled for several confounding factors, including age (ordinal in three age-groups as ≤59 years, 60–69 years, ≥70 years), sex (dichotomous, male vs female), secondary school qualifications (in eight groups as No secondary school qualifications, NZ School Certificate or National Certificate level 1 or NCEA level 1 or National Certificate level 1 or NCEA level 1, NZ Sixth Form Certificate or National Certificate level 2 or NZ UE before 1986 or NCEA level 2, NZ Higher School Certificate or NZ Higher School Certificate or NZ University NZ Higher School Certificate or NZ University NZ Higher School Certificate or NZ University Entrance from NZ Bursary or National Certificate level 3, NCEA (National Certificate of Educational Achievement) level 4, other NZ Secondary school qualification (specified), overseas secondary school qualification, don’t know, I do not wish to answer this question), body mass index (BMI) (ordinal in four categories as under-weight as ≤18.5, normal weight as between 18.5–25, overweight as ≥25–30, obese as ≥30), smoking habits and duration of smoking (as ex-smoker (yes or no) and pack-years among ex-smokers, current smoker (yes vs. no) and past years (among current smokers). The analysis was carried out taking glaucoma, cataracts and age-related macular degeneration as a general outcome, and then, alternatively, by glaucoma, cataracts, and age-related macular degeneration individually to explore whether the associations were specific to the type of oxidative stress-related ocular condition. All analyses were conducted using the MATLAB statistical toolbox (MathWorks, version R2016b, Portola Valley, CA, USA).

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