A meta-analysis to study the effect of pan retinal photocoagulation on retinal nerve fibre layer thickness in diabetic retinopathy patients

Authors: Wadhwani M, Bhartiya S, Upadhaya A, Manika M.

Geographical coverage: UK, South Korea, Iran, Turkey, Singapore

Sector: Biomedical

Sub-sector: Laser photocoagulation treatment, safety

Equity focus: Not specified

Study population: Diabetic patients with proliferative diabetic retinopathy

Review type: Other review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background:

While laser treatment, pan retinal photocoagulation (PRP) is a mainstay of treatment for proliferative diabetic retinopathy (PDR) and severe non-proliferative diabetic retinopathy (severe NPDR) and can reduce vision loss, it can cause irreversible changes to other inner retinal layers of the eye and to retinal nerve fibre layer (RNFL) thickness. Thus, damage to other retinal layers and RNFL thickness are serious potential complications of PRP requiring critical evaluation.

Objectives:

To assess changes in peripapillary retinal nerve fibre layer thickness in patients with PDR who have undergone PRP treatment, using optical coherence tomogram (OCT).

Main findings:

Ten studies that contained 377 eyes of PDR patients were included. The studies included were interventional that sought to investigate longitudinal changes in RNFL thickness pre and six months post PRP treatment in patients with PDR. Studies were conducted in the United Kingdom, South Korea, Iran, Turkey and Singapore. The meta-analysis results found that there was no significant effect of PRP on average RNFL thickness (0.249, 95% CI: -0.985 to 1.483) using OCT.

The findings of this review did not show any significant effect of PRP on RNFL thickness. As diabetes itself can cause reduction in RNFL via apoptosis of neuronal cells, it is not clear what the impact of PRP is on RNFL thickness independently, confounding the evaluation of nerve fibre layer damage and its progression. The authors warned that the assessment of peripapillary RNFL thickness in this specific group of patients could produce inaccurate and unpredictable outcomes, adding complexity to the assessment of nerve fibre layer damage and its progression. In addition, the authors proposed further research, particularly multicentre studies with a larger sample size, to help understand the complexity of RNFL changes following PRP.

Methodology:

The search was conducted on PubMed, Medline, OVID and Google Scholar to retrieve relevant articles published in English from January 2000 to October 2018. The studies were included if they included PDR patients treated with PRP, with RNFL thickness measured using OCT pre and six months post PRP. Two reviewers selected studies for inclusion based on the inclusion criteria. Data extraction was done by two independent reviewers. The quality of included studies was assessed using the Newcastle-Ottawa scale (NOS), and carried out by two reviewers.

The findings were synthesised using meta-analysis and presented as average RNFL thickness pre and post PRP with the weighted mean difference and standard deviation. Heterogeneity of the studies was calculated using I2 statistics. A fixed-effect analysis was used if heterogeneity was not significant, otherwise a random-effect model was applied. Sensitivity analysis was performed leading to one study exclusion. Publication bias was assessed using a funnel plot.

Applicability/external validity:

The authors did not specifically discuss the external validity of the results.

Geographic focus:

Included studies were conducted in the UK, South Korea, Iran, Turkey and Singapore. However, the authors do not report how findings of their review may be applicable to low and middle income settings.

Summary of quality assessment:

Overall, a low confidence was attributed to the conclusions of this review. There is a lack of clarity and information on the search strategy used to identify studies for inclusion in the review, and the risk-of-bias assessment of included studies were not sufficiently detailed in the study. In addition, authors did not clearly report the methods employed to carry out their analysis and differences between the results were not adequately discussed or explained. Lastly, there was no discussion of differing risk of bias in the included studies.

Publication Source:

Wadhwani, M, Bhartiya, S, Upadhaya, A, & Manika, M. (2020). A meta-analysis to study the effect of pan retinal photocoagulation on retinal nerve fibre layer thickness in diabetic retinopathy patients. Romanian Journal of Ophthalmology, 64(1), 8. https://doi.org/10.22336/rjo.2020.3

Downloadable link https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7141917/