Central corneal thickness: will one measurement suffice?
OBJECTIVE
To evaluate the measurement of central corneal thickness (CCT) in a cohort of glaucoma patients over a 3-month period. Measurements were then applied to the criteria described in the Ocular Hypertension Treatment Study (OHTS).


METHODS
Cohort study.


METHODS
Fifty-one patients were recruited from a glaucoma clinic at Moorfields Eye Hospital. Central corneal thickness was measured using an ultrasonic handheld pachymeter by a trained observer. Patients' CCTs were measured at 2 consecutive clinic visits.


METHODS
Mean central corneal thickness.


RESULTS
The readings showed clear fluctuation over the 3-month period, with a mean difference in corneal thickness of 9.6+/-26.9 microm in the right eye and 19.0+/-29.2 microm in the left eye. In addition, there was a systematic bias towards increased corneal thickness being recorded at the second reading in both eyes. This reached statistical significance in both the right eye (P = 0.02) and the left eye (P = 0.0003). The criteria used to categorize the risk of patients developing glaucoma in the OHTS were then applied to these results. On the basis of the second reading, 32% of eyes required recategorization in both the right and left eyes.


CONCLUSIONS
Measurements of CCT taken within a clinical setting by a trained observer may show significant variability. For CCT to become a valuable addition to the assessment of glaucoma suspects, more than one reading may be required. Failure to do so may result in misclassification and, thus, an inaccurate assignment of risk.
Wickham
Louisa
L
Moorfields Eye Hospital, London, United Kingdom. louisa.w@tiscali.co.uk
Edmunds
Beth
B
Murdoch
Ian E
IE
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000959:Antihypertensive Agents / Q000627:therapeutic use; D015982:Bias; D001837:Body Weights and Measures; D015331:Cohort Studies; D003315:Cornea / Q000000981:diagnostic imaging / Q000473:pathology*; D018450:Disease Progression; D005260:Female; D005901:Glaucoma / Q000175:diagnosis* / Q000188:drug therapy; D006801:Humans; D007429:Intraocular Pressure; D008297:Male; D008875:Middle Aged; D009798:Ocular Hypertension / Q000175:diagnosis / Q000188:drug therapy; D015203:Reproducibility of Results; D012189:Retrospective Studies; D018570:Risk Assessment; D014065:Tonometry, Ocular; D014463:Ultrasonography
D000959:Antihypertensive Agents