Comparison of central corneal thickness measurement by scanning slit topography, infrared, and ultrasound pachymetry in normal and post-LASIK eyes.

OBJECTIVES: To compare central corneal thickness (CCT) measurements by scanning slit topography (SST), infrared pachymetry (IRP), and ultrasound pachymetry (USP), and their agreement in normal and post-laser in situ keratomileusis (LASIK) eyes. METHODS: Sixty normal and 35 post-LASIK subjects were recruited. Only one eye from each subject was analyzed. Non-contact pachymetry was performed first, and the order for SST (Orbscan IIz) and IRP (Tonoref III) was randomized for each patient, to be followed by contact USP (Echoscan US-4000). Pearson's correlation, paired t test, and Bland-Altman plots were used to investigate association, difference, and agreement among different instruments respectively. RESULTS: The measurements obtained with the instruments were highly correlated. Compared to CCT determined by USP (CCTUSP), CCT determined by SST (after correction with acoustic factor) (CCTSSTC) was thicker by 7 µm in normal eyes (P < 0.001). There was no significant difference between CCTSSTC and CCTUSP (P = 0.128), but a thickness-dependent deviation in post-LASIK eyes (P = 0.003). The CCT determined by IRP (CCTIRP) was thicker than CCTUSP in normal (P < 0.001) and post-LASIK eyes (P < 0.001) and demonstrated proportional overestimation with thinner corneas, with less predictable ultrasonic equivalent corneal thickness in normal eyes. Conversely, CCTIRP significantly underestimated CCT compared to CCTSST and showed increasing underestimation with thinner corneas in both normal and post-LASIK eyes (both P < 0.001). CONCLUSION: Central corneal thickness determined by SST, IRP and USP were not interchangeable or interconvertible, probably attributed to difference in methodologies. Compensation with algorithms may improve agreements amongst instruments.

Paraneoplastic pemphigus: an uncommon cause of chronic cicatrising conjunctivitis.

We report a case of paraneoplastic pemphigus (PNP) as an uncommon but severe cause of cicatrising conjunctivitis. Initially diagnosed as drug eruptions, the patient's condition did not improve despite cessation of chemotherapy. Immunohistological confirmation of PNP has led to the use of combined oral prednisolone and intravenous immunoglobulin. Her ocular conditions stabilised with complete recovery of vision. PNP is a rare disease that can present with ocular involvement. Ophthalmologists should play an active role in monitoring and treatment of ocular surface complications such as symblepharon formation, severe dry eye and epithelial breakdown. Vigorous and prompt treatment is the key to successful prevention of irreversible and blinding complications. The atypical feature in this case is the presence of eosinophilic infiltration on histology that is a feature of allergic aetiologies rather than classical PNP.

Waiting time for cataract surgery and its influence on patient attitudes.

PURPOSE: To characterize willingness to pay for private operations and preferred waiting time among patients awaiting cataract surgery in Hong Kong. METHODS: This was a cross-sectional survey. Subjects randomly selected from cataract surgical waiting lists in Hong Kong (n = 467) underwent a telephone interview based on a structured, validated questionnaire. Data were collected on private insurance coverage, preferred waiting time, amount willing to pay for surgery, and self-reported visual function and health status. RESULTS: Among 300 subjects completing the interview, 144 (48.2%) were 76 years of age or older, 177 (59%) were women, and mean time waiting for surgery was 17 +/- 15 months. Among 220 subjects (73.3%) willing to pay anything for surgery, the mean amount was US$552 +/- 443. With adjustment for age, education, and monthly household income, subjects willing to pay anything were less willing to wait 12 months for surgery (OR = 4.34; P = 0.002), more likely to know someone having had cataract surgery (OR = 2.20; P = 0.03), and more likely to use their own savings to pay for the surgery (OR = 2.21; P = 0.04). Subjects considering private cataract surgery, knowing people who have had cataract surgery, using nongovernment sources to pay for surgery, and having lower visual function were willing to pay more. CONCLUSIONS: Many patients wait significant periods for cataract surgery in Hong Kong, and are willing to pay substantial amounts for private operations. These results may have implications for other countries with cataract waiting lists.