2.1 The guideline development group
Members of the guideline development group represented ophthalmology, medicine
and epidemiology.

2.2 Gathering the evidence
Literature searches were undertaken with the assistance of the Cochrane Eyes And
Vision Group.
Databases searched were
Cochrane Library
Medline
Embase
Keywords, literature search strategies and full reference list are available on request
from the Scientific Department, Royal College of Ophthalmologists. Key references
only are included in the guidelines.

2.3 Assessing the evidence and forming recommendations

Relevant literature was identified and the level of evidence graded. Evidence was
then assessed for consistency, applicability, and clinical impact.
Recommendations for a good standard of practice were formed using the following
categories (i.e. strength of the evidence) and included in the text of the guidelines.

 At least one meta-analysis, systematic review, or good quality randomised
control trial (RCT) directly applicable to the target population; or a body of
evidence consisting principally of RCTs, directly applicable to the target
population, and demonstrating overall consistency of results.

 A body of evidence including high quality systematic reviews of case-control or
cohort studies, directly applicable to the target population, and demonstrating
overall consistency of results; or extrapolated evidence from RCTs.

 A body of evidence including studies rated as well conducted case control or
cohort studies with a low risk of confounding or bias and a moderate
probability that the relationship is causal, directly applicable to the target
population and demonstrating overall consistency of results; or extrapolated
evidence from studies rated as high quality systematic reviews of case-control
or cohort studies.

 Evidence from non-analytic studies, e.g. case reports, case series or expert
opinion

2.4 Consultation process
The guideline development group invited comments on this guideline from all UK
consultant ophthalmologists and Royal College of Ophthalmologists Patient Advisory
Committee prior to publication.