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Long-term effect of YAG laser iridotomy on corneal endothelium in primary angle closure suspects: a 72-month randomised controlled study
  1. Chimei Liao1,
  2. Jian Zhang1,
  3. Yuzhen Jiang2,
  4. Shengsong Huang1,
  5. Tin Aung3,
  6. Paul J Foster4,
  7. David Friedman5,
  8. Mingguang He1,6
  1. 1State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
  2. 2Moorfield Eye Hospital NHS Foundation Trust, London, UK
  3. 3Singapore Eye Research Institute and Singapore National Eye Center, Singapore
  4. 4NIHR Biomedical Research Center at Moorfields Eye Hospital and UCL Institute of Ophthalmology, London, UK
  5. 5Massachusetts Eye and Ear, Harvard Medical School Department of Ophthalmology, Boston, Massachusetts, USA
  6. 6Center for Eye Research Australia, University of Melbourne, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia
  1. Correspondence to Dr Mingguang He, State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou 510060, China; mingguanghe{at}


Purposes To evaluate the effect of YAG laser peripheral iridotomy (LPI) on corneal endothelial cell density (ECD) and morphology in primary angle closure suspects (PACS) over 72 months.

Methods The Zhongshan Angle Closure Prevention Trial is a single-centre randomised controlled trial. Subjects with bilateral PACS received YAG LPI prophylactic treatment in one eye randomly, while the fellow eye served as control. Central corneal ECD and morphology were assessed using non-contact specular microscopy (SP-2000P, Topcon) at baseline, 6, 18, 36, 54 and 72 months postoperatively. Mixed model analysis was conducted to compare the difference between treated and fellow eyes.

Results A total of 875 participants were included, with a mean age of 59.3±5.0 years and 83.5% female. The ECD declined significantly (p<0.001) over time in both treated and fellow eyes, but the treated eyes showed more progressive cell loss with increasing time (p<0.001). The difference in ECD loss between LPI-treated and fellow eyes was not significant at each follow-up until 72 months (4.9% in LPI eyes vs 4.2% in non-LPI eyes, p=0.003). Mean cell areas increased significantly over time in both treated and fellow eyes (p<0.001), but no longitudinal change was observed for hexagonality. In LPI-treated eyes, no significant correlation was found between age, gender, ocular biometrics, intraocular pressure and laser settings with endothelium change, except for time effect (p<0.01).

Conclusion ECD decreases over time primarily due to ageing effect. YAG LPI does not appear to cause clinically significant corneal endothelial damage over 72 months after treatment.

Trial registration number ISRCTN45213099.

  • treatment lasers
  • glaucoma
  • cornea

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  • PJF, DF and MH are joint senior authors.

  • Contributors CL and JZ: data analysis and interpretation, manuscript preparation. YJ and SH: data acquisition and research execution. TA: research design. PJF, DF and MH: research design and manuscript revision. PJF, DF and MH authors take joint credit and responsibility.

  • Funding This work is supported by the Fight for Sight (grant no. 1655) (UK), the Sun Yat-sen University 5010 Project Fund (grant no. 2007033) (China), the National Natural Science Foundation of China (grant no. 81420108008) (China), Special Trustees of Moorfields Eye Hospital (via Fight for Sight), Johns Hopkins University and Fundamental Research Funds of the State Key Laboratory in Ophthalmology (China). Professor MH receives support from the University of Melbourne Research at Melbourne Accelerator Program Professorship. The Centre for Eye Research Australia receives operational infrastructural support from the Victorian government. Dr YJ and Professor PJF supported by a grant from the British Council for Prevention of Blindness (UK). Professor PJF received additional support from the National Institute for Health Research (NIHR) Biomedical Research Centre at Moorfields Eye Hospital, London, UK (NIHR-BRC2 009; Moorfields/UCL-IOO), Special Trustees of Moorfields Eye Hospital (since renamed Moorfields Eye Charity) and the Richard Desmond Charitable Foundation (via Fight for Sight UK).

  • Disclaimer These funding sources did not play any role in the design and conduct of the study; in the collection, management, analysis or interpretation of the data; or in the preparation, review, approval of the manuscript or decision to submit the manuscript for publication.

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Ethics approval This trial was approved by the Ethical Review Board of Sun Yat-sen University, the Ethical Committee of Zhongshan Ophthalmic Center and the Moorfields Eye Hospital (via the London School of Hygiene & Tropical Medicine) and Johns Hopkins University institutional review boards. The study was conducted in accordance with the tenets of the Declaration of Helsinki.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement Data are available on reasonable request. Deidentified participant data that underlie the results reported in this article and statistical analysis code are available immediately following publication with no end date. Researches who provide a methodologically sound proposal can send proposal directed to To gain access, data requestors need to sign a data access agreement.

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