The Open Ophthalmology Journal




ISSN: 1874-3641 ― Volume 13, 2019

Clinical Findings Among Nigerian Paediatric Glaucoma Suspects During A School Eye Health Survey



Abdulkabir Ayansiji Ayanniyi1, *, Fatai Olasunkanmi Olatunji1, Abdulraheem Olarongbe Mahmoud1, Rashidat Oluwafunke Ayanniyi2
1 Department of Ophthalmology, University of Ilorin Teaching Hospital, Ilorin, Nigeria
2 Department of Pharmacology and Therapeutics, University of Ilorin, Nigeria

Abstract

Objective

To report clinical findings suspicious of glaucoma among primary school children in Ilorin, Nigeria.

Methods

A cross sectional survey of ocular health among 1,393 school children carried out between July 2005 and January 2006. Criteria for suspecting glaucoma included a cup disc ratio (CD) of > 0.5, a CD asymmetry between the fellow eyes of > 0.2, and/or intraocular pressure (IOP) > 21mmHg by applanation tonometry.

Results

Eleven (6 boys and 5 girls) of 1,393 pupils (0.8%), aged between 7 and 13 years, had ocular findings suspicious of glaucoma. Twenty two eyes of 11 pupils had a CD ratio ≥ 0.6, and among these 5 eyes had IOP > 21. Three of the pupils had a CD asymmetry of > 0.2.

Conclusion

A significant proportion of these Nigerian school pupils had clinical signs suggestive of glaucoma. A functional school health programme with eye health component coupled with efficient referral system is advocated.

Keywords: School eye screening, glaucoma suspect, referral system.


Article Information


Identifiers and Pagination:

Year: 2008
Volume: 2
First Page: 137
Last Page: 140
Publisher Id: TOOPHTJ-2-137
DOI: 10.2174/1874364100802010137

Article History:

Received Date: 9/7/2008
Revision Received Date: 23/7/2008
Acceptance Date: 25/7/2008
Electronic publication date: 2/9/2008
Collection year: 2008

Article Metrics:

CrossRef Citations:
0

Total Statistics:

Full-Text HTML Views: 1262
Abstract HTML Views: 650
PDF Downloads: 197
Total Views/Downloads: 2109

Unique Statistics:

Full-Text HTML Views: 436
Abstract HTML Views: 408
PDF Downloads: 146
Total Views/Downloads: 990
Geographical View

© Ayanniyi et al.; Licensee Bentham Open

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.5/), which permits unrestrictive use, distribution, and reproduction in any medium, provided the original work is properly cited.


* Address correspondence to this author at the Department of Ophthalmology, University of Ilorin Teaching Hospital, Ilorin, Nigeria; Tel: +2348058548765; E-mail: ayanniyikabir@yahoo.com




INTRODUCTION

Glaucoma is a dreaded blinding eye disease yet vision can be preserved if detected early and necessary intervention employed. Glaucoma has characteristic features that give away its diagnosis such as progressive visual field loss and optic nerve head damage among others [1Bourne RRA. Glossary The optic nerve head in glaucoma Community Eye Health J 2006; 19: 44- 45., 2Thomas R, Parikh RS. How to assess a patient for glaucoma Community Eye Health J 2006; 19: 36-7.]. However, the presence of these characteristic features implies certain degree of visual loss. The prospect of preserving lifetime useful vision in glaucomatous eyes lies in early diagnosis and intervention.

At its very early stage the diagnosis of glaucoma is not only difficult but also requires sophisticated resources [2Thomas R, Parikh RS. How to assess a patient for glaucoma Community Eye Health J 2006; 19: 36-7., 3Kanski JJ. Clinical Ophthalmology Glaucoma Optic nerve head In: China Elsevier Butterworth-Heinemann. 6. 2007; pp. 371-440.]. This is a challenge for screening for glaucoma more especially in resource limited economy. The limitation notwithstanding, there are ocular clinical features that can arouse suspicion of glaucoma once they are found during eye examination. Although these clinical features alone may not necessarily confirm glaucoma, they would be found useful in situations where sophisticated resources are not available more especially where rapid screening is required. This implies that individuals with eyes examination findings suspicious of glaucoma would be referred appropriately for further ophthalmic evaluation at ophthalmic clinic.

Usually the diagnosis of glaucoma heralds fear, anxiety and hopelessness when first detected at an advanced stage. However, studies have shown that detection of glaucoma at an early stage and institution of appropriate intervention can ensure preservation of a lifetime useful visual function [4Wormald R. What is new in glaucoma treatment? Community Eye Health J 2006; 19: 33-5., 5Maier PC, Funk J, Schwarzer G, Antes G, Falck-Ytter YT. Treatment of ocular hypertension and open-angle glaucoma meta-analysis of randomized controlled trials BMJ 2005; 331(7509): 134-7.].

Many ocular problems that are amenable to interventional measures (including glaucoma) are detected through vision screening of selected population such as school children [6Faderin MA, Ajaiyeoba AI. Refractive errors in primary school children in Nigeria Nig J Ophthalmol 2001; 9: 10-4.-8Abubakar S, Ajaiyeoba AI. Screening for eye disease in Nigeria school children Nig J Ophthalmol 2001; 9: 6-9.]. Eye surveys have potential to promote normal vision, preserve healthy eyes and prevent blindness [9Johnson GJ, Foster A. Prevalence, incidence and distribution of visual impairment In: Johnson GJ, Minassian DC, Weale RA, West SK, Eds. Epidemiology of eye disease. 2 . London: Arnold publishers 2003; pp. 3-28.]. The aim of this paper is to report clinical findings suspicious of glaucoma among primary school children in Ilorin, Nigeria, with the view that such features can serve as basis for referral especially during epidemiological eye surveys to ophthalmic clinics where further evaluation to confirm or rule out glaucoma can be done.

MATERIALS AND METHODS

This study formed part of a large ocular health survey among school children in Ilorin, Nigeria. It was a cross-sectional descriptive study carried out between July 2005 and January 2006 in 10 randomly selected non-residential primary schools within Ilorin, an urban city in Nigeria. One thousand three hundred and ninety three sampled pupils from the selected schools were surveyed. The population of school children in Ilorin metropolis was approximately 166,000 as at July 2005.

Ethical clearance for the study was obtained from University of Ilorin Teaching Hospital. There were initial advocacy visits to the local school board and the selected schools to convey the objectives and importance of the study with a view to gaining support and permission to carry out the study.

The sample size of surveyed pupils was determined using the equation: n = z2pq/d2. Where n is the desired sample size, z is the standard normal deviate (z is taken as 1.96 which corresponds to the 95% confidence level), p is the proportion (prevalence) of the children population estimated to have visual problem and d is the degree of accuracy. The prevalence (p) of ocular pathology among school children from previous studies in Nigeria [10Isawumi MA. Ocular disorders among school children in Osun State, Nigeria Dissertation for the award of Fellowship Diploma of the National Postgraduate Medical College of Nigeria in Ophthalmology 2003., 11Ugochukwu CIO. Survey of eye health status of primary school children in Nkanu West Local Government Area of Enugu State, Nigeria Dissertation for the award of Fellowship Diploma of the National Postgraduate Medical College of Nigeria in Ophthalmology 2002., 12Onyekwe LO. Visual impairment among school children in Jos, Plateau State, Nigeria Dissertation for the award of Fellowship Diploma of the National Postgraduate Medical College of Nigeria in Ophthalmology 1995.]was 17%. Thus p = 0.17, q = 1.0 – p = 0.83 and d was set at 2% (i.e. 0.02). Thus the calculated minimal sample size (n) was 1355. However, the study was carried out on 1393 pupils.

Multistage random sampling technique was employed to select the pupils. Generated random numbers were used to select 10 primary schools from a list of 184 primary schools within Ilorin metropolis. Each studied primary school had 6 classes and each class was subdivided into a number of arms. Using the calculated minimal sample size as well as the number of pupils in each class as a guide, a predetermined number of 30 pupils was randomly selected for the study from each class. Through the assistance of class teachers, all available pupils in all the arms of a particular class were assembled and each pupil was asked to pick a numbered wrapped paper. The pupils who picked the first 30 numbers were selected from each class for the study and thus a total number of 180 pupils from each school and an overall 1800 from 10 schools. The exclusion criteria included age 16 year and above, lack of guardian consent for pupil to participate, inability to cooperate with the examination process, failure of a child’s guardian to complete relevant sections of the proforma, and earlier participation in the preceding pilot study.

The examinations were carried out in the classrooms in broad daylight. The presence of the class teachers ensured the co-operation of most pupils with the examination process. Visual acuity (VA) determination and a pin hole test was done for pupils with VA of 6/9 or worse. With the aid of the pen torch the eyelids, the conjunctiva, the cornea, the anterior chamber, the iris and the pupil of each eye were examined. Other tests including colour vision test, Hirschberg test and cover-uncover test among others were also carried out. Reports of these are subject of another paper under consideration for publication elsewhere. With the aid of direct ophthalmoscope the posterior segment of the eyes of each pupil was examined in a darkened corner of the classroom (achieved by closing few windows). The eye was dilated with 0.5% tropicamide drops whenever mydriasis was required for fundoscopy.

The intra ocular pressure (IOP) of pupils whose ocular findings were suspicious of glaucoma was measured with a Perkins applanation tonometer. The criteria for suspecting glaucoma as used in the study included a cup disc ratio (CD) of > 0.5, a CD asymmetry between the fellow eyes of > 0.2, and/or intraocular pressure (IOP) > 21mmHg by applanation tonometry. Confrontation visual field test was carried out to detect gross visual field defects. Standard perimetry to detect visual field defects could not be carried out at the schools.

The pupils were referred to the University of Ilorin Teaching Hospital, for further review/ management/ follow up as appropriate. Post survey advocacy visits to sampled schools were carried out to meet the guardians of affected pupils in order to encourage them to follow their wards to referral hospital for further review/ management and to express appreciation to the school communities.

Data entry and analysis were done with Statistical Package for Social Scientist (SPSS) version 12.0.1.

RESULTS

One thousand three hundred and ninety three sampled pupils from 10 sampled schools including 689 (49.4%) boys and 704 (50.6%) girls (M: F=1:1) were examined. The age range was between 4 and 15 years. The mean and modal ages were 10.16 ± 2.5 and 10 respectively. Eleven (6 boys and 5 girls) out of 1,393 pupils (0.8%), aged between 7 and 13 years, had ocular findings suspicious of glaucoma (Table 1).

Table 1

Demographic Characteristics and Ocular Findings Among 11 Pupils




Six of the 22 eyes (3 pupils) had clinical findings such as pale disc with cup to disc ratio (CD) ranging between 0.6–0.9, nasalised vessels, intraocular pressure (IOP) of 19mmHg in an eye and between 22 and 30mmHg in 5 eyes. The visual acuity (VA) was 6/6 in 5 eyes and Perception of Light (PL) in an eye. The pupils included 2 boys and a girl whose ages were 7, 8 and 13 years (Table 1).

The findings among remaining 16 eyes (8 pupils) included: CD of 0.6 in 13 eyes (with nasalised vessels in 2 of the eyes), and 0.7 in 3 eyes. The VA of the 16 eyes included 6/5 in 3 eyes, 6/6 in 11 eyes and 6/9 in 2 eyes. All the 16 eyes had IOP ranging between 11 and 16mmHg.

Although there was no history suggestive of glaucoma among the pupils’ first-degree relatives, all the pupils were Blacks.

DISCUSSION

The finding of a prevalence of 0.8% for pupils with clinical features suspicious of glaucoma is significant. The cup to disc (CD) ratio of >0.5 as used in the study as a clinical feature suspicious of glaucoma was borne out of the fact that established glaucoma is usually associated with high CD ratio [1Bourne RRA. Glossary The optic nerve head in glaucoma Community Eye Health J 2006; 19: 44- 45., 2Thomas R, Parikh RS. How to assess a patient for glaucoma Community Eye Health J 2006; 19: 36-7., 3Kanski JJ. Clinical Ophthalmology Glaucoma Optic nerve head In: China Elsevier Butterworth-Heinemann. 6. 2007; pp. 371-440.]. Diagnosis might further be strengthened if the subject had any or combination of positive family history of glaucoma, raised intraocular pressure and disc pallor [3Kanski JJ. Clinical Ophthalmology Glaucoma Optic nerve head In: China Elsevier Butterworth-Heinemann. 6. 2007; pp. 371-440.]. A relatively high CD ratio may also be found among non-glaucomatous conditions such as myopes, some familiar cases, and generally among members of the Black race when compared to their Caucasian counterparts [3Kanski JJ. Clinical Ophthalmology Glaucoma Optic nerve head In: China Elsevier Butterworth-Heinemann. 6. 2007; pp. 371-440.]. Though all the members of our cohort were Blacks, a history of glaucoma among the pupils’ first degree relations could not be elicited. It is conceivable that poor health infrastructure and lack of awareness of glaucoma might have rendered the pupils’ relations unaware of glaucoma among those who might have the disease.

Another clinical feature that heightened suspicion of glaucoma among the pupils was the presence of cup disc asymmetry in 3 pupils. The cup disc asymmetry in the presence of other risk factors for glaucoma heightens suspicion of glaucoma and such pupils need further evaluation. Nasalised vessels were also an important feature found among the cohort that could suggest glaucoma.

High IOP is a strong risk factor for glaucoma. Individuals with persistent raised IOP even in the absence of visual field and optic nerve defects are regarded as glaucoma suspects as they often show glaucomatous features over time [1Bourne RRA. Glossary The optic nerve head in glaucoma Community Eye Health J 2006; 19: 44- 45., 3Kanski JJ. Clinical Ophthalmology Glaucoma Optic nerve head In: China Elsevier Butterworth-Heinemann. 6. 2007; pp. 371-440., 13Ashaye AO. Clinical features of primary glaucoma in Ibadan Nigeria J of Ophthalmol 2003; 11: 70-5.]. Three of the pupils had IOP between 19 and 30mmHg, pale disc, high CD ratio ≥ 0.6 and one eye was already blind (VA of PL) from glaucoma. Though in the cohort, most had IOP in the acceptable normal range, glaucoma could not be totally ruled out in them in view of other findings suspicious of glaucoma. Studies have shown that IOP rises with age. Apart from this fact, IOP that is within statistical normal limits may be too high for an individual eye as found in normal/low tension glaucoma [3Kanski JJ. Clinical Ophthalmology Glaucoma Optic nerve head In: China Elsevier Butterworth-Heinemann. 6. 2007; pp. 371-440., 14Mwanza JC. Primary open-angle glaucoma in Sub-Saharan Africa Nigeria J of Ophthalmol 2006; 14: 22-6., 15Jerald AB, Robert JN, Emily P. Glaucoma, Primary Open Angle Emedicine 2005 Aug; [Acessed on emedicine 7th June,[2008]];, 16Hollows FC, Graham PA. Intra-ocular pressure, glaucoma and glaucoma suspects in a defined population Br J Ophthalmol 1966; 50: 570.].

We acknowledged that our method used in the case detection of the glaucoma suspects had its limitations. The use of measurement of intraocular pressure alone has been shown to be a poor predictor of glaucoma [17Jackson C, Bullock J, Pitt M, Keogh J, Glasson W, Hirst L. Screening for glaucoma in a Brisbane general practice-the role of tonometry Aust N Z J Ophthalmol 1995; 23: 173-8.]. However, the combination of tonometry and fundoscopy that we used in our study had been shown to increase the sensitivity and specificity further to 61% and 84% respectively [18Tielsch JM, Katz J, Sing K, et al. A population-based evaluation of glaucoma screening The Baltimore Eye Survey Am J Epidemiol 1991; 134: 1102-10.].

All eyes except one member of the cohort have normal visual acuity (VA). VA is not a good criterion for diagnosing glaucoma as it may be normal in advanced glaucoma [3Kanski JJ. Clinical Ophthalmology Glaucoma Optic nerve head In: China Elsevier Butterworth-Heinemann. 6. 2007; pp. 371-440.].

Glaucoma is better diagnosed very early in order to preserve sight; hence the need for regular eye examination in the cohort of pupils before the signs become so obvious and the damage irreversible [19Olurin O. National Postgraduate Medical College of Nigeria. Third Faculty of Ophthalmology lecture Glaucoma Revisited 18th August 2000 18; 3-8.]. Controlling blindness from glaucoma requires early detection, life-long treatment and compliance of the patients [20Kocur I. What's new at the back of the eye? Community Eye Health J 2006; 19: 1-3.].The guardians of the cohort of pupils with ocular features of glaucoma were informed of the findings and they were appropriately referred for further review/follow up in the ophthalmic clinic.

Concluding, a significant proportion of pupils during a routine school eye health survey had clinical signs suggestive of glaucoma. A functional school health programme with eye health component coupled with efficient referral system is advocated.

ACKNOWLEDGEMENTS

Our special appreciation goes to the local School Authority (Kwara State Universal Basic Education Board), the sampled schools, the guardians and cohort of pupils who were subjects of the study.

REFERENCES

[1] Bourne RRA. Glossary The optic nerve head in glaucoma Community Eye Health J 2006; 19: 44- 45.
[2] Thomas R, Parikh RS. How to assess a patient for glaucoma Community Eye Health J 2006; 19: 36-7.
[3] Kanski JJ. Clinical Ophthalmology Glaucoma Optic nerve head In: China Elsevier Butterworth-Heinemann. 6. 2007; pp. 371-440.
[4] Wormald R. What is new in glaucoma treatment? Community Eye Health J 2006; 19: 33-5.
[5] Maier PC, Funk J, Schwarzer G, Antes G, Falck-Ytter YT. Treatment of ocular hypertension and open-angle glaucoma meta-analysis of randomized controlled trials BMJ 2005; 331(7509): 134-7.
[6] Faderin MA, Ajaiyeoba AI. Refractive errors in primary school children in Nigeria Nig J Ophthalmol 2001; 9: 10-4.
[7] Wedner S, Dineen B. Refractive errors Trop Doc 2003; 33: 207-9.
[8] Abubakar S, Ajaiyeoba AI. Screening for eye disease in Nigeria school children Nig J Ophthalmol 2001; 9: 6-9.
[9] Johnson GJ, Foster A. Prevalence, incidence and distribution of visual impairment In: Johnson GJ, Minassian DC, Weale RA, West SK, Eds. Epidemiology of eye disease. 2 . London: Arnold publishers 2003; pp. 3-28.
[10] Isawumi MA. Ocular disorders among school children in Osun State, Nigeria Dissertation for the award of Fellowship Diploma of the National Postgraduate Medical College of Nigeria in Ophthalmology 2003.
[11] Ugochukwu CIO. Survey of eye health status of primary school children in Nkanu West Local Government Area of Enugu State, Nigeria Dissertation for the award of Fellowship Diploma of the National Postgraduate Medical College of Nigeria in Ophthalmology 2002.
[12] Onyekwe LO. Visual impairment among school children in Jos, Plateau State, Nigeria Dissertation for the award of Fellowship Diploma of the National Postgraduate Medical College of Nigeria in Ophthalmology 1995.
[13] Ashaye AO. Clinical features of primary glaucoma in Ibadan Nigeria J of Ophthalmol 2003; 11: 70-5.
[14] Mwanza JC. Primary open-angle glaucoma in Sub-Saharan Africa Nigeria J of Ophthalmol 2006; 14: 22-6.
[15] Jerald AB, Robert JN, Emily P. Glaucoma, Primary Open Angle Emedicine 2005 Aug; [Acessed on emedicine 7th June,[2008]];
[16] Hollows FC, Graham PA. Intra-ocular pressure, glaucoma and glaucoma suspects in a defined population Br J Ophthalmol 1966; 50: 570.
[17] Jackson C, Bullock J, Pitt M, Keogh J, Glasson W, Hirst L. Screening for glaucoma in a Brisbane general practice-the role of tonometry Aust N Z J Ophthalmol 1995; 23: 173-8.
[18] Tielsch JM, Katz J, Sing K, et al. A population-based evaluation of glaucoma screening The Baltimore Eye Survey Am J Epidemiol 1991; 134: 1102-10.
[19] Olurin O. National Postgraduate Medical College of Nigeria. Third Faculty of Ophthalmology lecture Glaucoma Revisited 18th August 2000 18; 3-8.
[20] Kocur I. What's new at the back of the eye? Community Eye Health J 2006; 19: 1-3.

Endorsements



"Open access will revolutionize 21st century knowledge work and accelerate the diffusion of ideas and evidence that support just in time learning and the evolution of thinking in a number of disciplines."


Daniel Pesut
(Indiana University School of Nursing, USA)

"It is important that students and researchers from all over the world can have easy access to relevant, high-standard and timely scientific information. This is exactly what Open Access Journals provide and this is the reason why I support this endeavor."


Jacques Descotes
(Centre Antipoison-Centre de Pharmacovigilance, France)

"Publishing research articles is the key for future scientific progress. Open Access publishing is therefore of utmost importance for wider dissemination of information, and will help serving the best interest of the scientific community."


Patrice Talaga
(UCB S.A., Belgium)

"Open access journals are a novel concept in the medical literature. They offer accessible information to a wide variety of individuals, including physicians, medical students, clinical investigators, and the general public. They are an outstanding source of medical and scientific information."


Jeffrey M. Weinberg
(St. Luke's-Roosevelt Hospital Center, USA)

"Open access journals are extremely useful for graduate students, investigators and all other interested persons to read important scientific articles and subscribe scientific journals. Indeed, the research articles span a wide range of area and of high quality. This is specially a must for researchers belonging to institutions with limited library facility and funding to subscribe scientific journals."


Debomoy K. Lahiri
(Indiana University School of Medicine, USA)

"Open access journals represent a major break-through in publishing. They provide easy access to the latest research on a wide variety of issues. Relevant and timely articles are made available in a fraction of the time taken by more conventional publishers. Articles are of uniformly high quality and written by the world's leading authorities."


Robert Looney
(Naval Postgraduate School, USA)

"Open access journals have transformed the way scientific data is published and disseminated: particularly, whilst ensuring a high quality standard and transparency in the editorial process, they have increased the access to the scientific literature by those researchers that have limited library support or that are working on small budgets."


Richard Reithinger
(Westat, USA)

"Not only do open access journals greatly improve the access to high quality information for scientists in the developing world, it also provides extra exposure for our papers."


J. Ferwerda
(University of Oxford, UK)

"Open Access 'Chemistry' Journals allow the dissemination of knowledge at your finger tips without paying for the scientific content."


Sean L. Kitson
(Almac Sciences, Northern Ireland)

"In principle, all scientific journals should have open access, as should be science itself. Open access journals are very helpful for students, researchers and the general public including people from institutions which do not have library or cannot afford to subscribe scientific journals. The articles are high standard and cover a wide area."


Hubert Wolterbeek
(Delft University of Technology, The Netherlands)

"The widest possible diffusion of information is critical for the advancement of science. In this perspective, open access journals are instrumental in fostering researches and achievements."


Alessandro Laviano
(Sapienza - University of Rome, Italy)

"Open access journals are very useful for all scientists as they can have quick information in the different fields of science."


Philippe Hernigou
(Paris University, France)

"There are many scientists who can not afford the rather expensive subscriptions to scientific journals. Open access journals offer a good alternative for free access to good quality scientific information."


Fidel Toldrá
(Instituto de Agroquimica y Tecnologia de Alimentos, Spain)

"Open access journals have become a fundamental tool for students, researchers, patients and the general public. Many people from institutions which do not have library or cannot afford to subscribe scientific journals benefit of them on a daily basis. The articles are among the best and cover most scientific areas."


M. Bendandi
(University Clinic of Navarre, Spain)

"These journals provide researchers with a platform for rapid, open access scientific communication. The articles are of high quality and broad scope."


Peter Chiba
(University of Vienna, Austria)

"Open access journals are probably one of the most important contributions to promote and diffuse science worldwide."


Jaime Sampaio
(University of Trás-os-Montes e Alto Douro, Portugal)

"Open access journals make up a new and rather revolutionary way to scientific publication. This option opens several quite interesting possibilities to disseminate openly and freely new knowledge and even to facilitate interpersonal communication among scientists."


Eduardo A. Castro
(INIFTA, Argentina)

"Open access journals are freely available online throughout the world, for you to read, download, copy, distribute, and use. The articles published in the open access journals are high quality and cover a wide range of fields."


Kenji Hashimoto
(Chiba University, Japan)

"Open Access journals offer an innovative and efficient way of publication for academics and professionals in a wide range of disciplines. The papers published are of high quality after rigorous peer review and they are Indexed in: major international databases. I read Open Access journals to keep abreast of the recent development in my field of study."


Daniel Shek
(Chinese University of Hong Kong, Hong Kong)

"It is a modern trend for publishers to establish open access journals. Researchers, faculty members, and students will be greatly benefited by the new journals of Bentham Science Publishers Ltd. in this category."


Jih Ru Hwu
(National Central University, Taiwan)


Browse Contents



Webmaster Contact: info@benthamopen.net
Copyright © 2019 Bentham Open