A Clinical Study of Keratoconus in Asian Patients and Assessment of Different Topographic Patterns of Keratoconus in Asian Patients
A clinical study of keratoconus in Asian Patients and assessment of different topographic patterns of keratoconus in Asian patients
|Study Design:||Observational Model: Case Control
Time Perspective: Cross-Sectional
|Study Start Date:||September 2003|
|Estimated Study Completion Date:||March 2005|
This hospital-based observational prospective study was designed to describe the characteristics of patients with keratoconus in an Asian population, Patients with keratoconus and keratoconus suspects presenting to the Singapore National Eye Centre who met the eligibility criteria are were recruited for this study. The following data were assessed:
- Demographic characteristics of patients with keratoconus
- Quality of life assessment in patients with keratoconus
- Visual Outcome and management of keratoconus in terms of contact lens fitting
- Corneal topographic patterns of patients with keratoconus
- Aberrometry studies with regards to diagnosis of keratoconus and quality of vision in patients with keratoconus.
The patients not wearing contact lenses completed the study within one visit whereas the patients wearing contact lenses required 2 visits (one with contact lens wear and one without contact lens wear) to complete the study. For patients wearing contact lenses, they were advised to stop soft or rigid contact lens wear for 3 days before the initial visual acuity, subjective refraction, keratometry, Tomey and Orbscan II topography examinations and Wavefront aberrometry tests were performed.
Informed consent was obtained from all subjects after the nature of the study had been fully explained. The study gained approval from the Ethics Committee of the Singapore Eye Research Institute .
Each study participant was asked to answer the demography questionnaire form regarding their daily habit, medical history, economic and educational level and vision-related quality of life, and the Visual Function Index (VF-14).
Visual acuity was assessed in each eye using a logMAR chart. The visual acuity with manifest refraction was deemed the best corrected visual acuity(BCVA) for those patients who did not wear contact lenses, and the visual acuity with over-refraction (refraction over their contact lenses) for contact lens wearers.
Contrast sensitivity was examined only in patients with their habitual contact lenses in each eye using the Vision Contrast Test System (VCTS) chart (VCTS 6500 contrast sensitivity Chart) in 6 spatial frequencies.
Slit lamp evaluation and contact lens fit assessment were performed. Type of contact lens wear was recorded.
Corneal topography was performed using Tomey keratoconus screening system (Topographic Modeling System, software version 2.4.2J) without pupil dilation and without contact lens wear and the Orbscan II corneal topography system (Bausch &Lomb Surgical).
Ocular wavefront aberrations were measured across the central 6-mm dilated pupil (1% Tropicamide) of each eye with the Bausch and Lomb Technolas Zywave aberrometer with Zywave software version 4.45 (ZYOPTIX Diagnostic Workstation, Bausch & Lomb).