Epidemiological Assessment of Keratoconus in Yazd Province in 2008-2009

1. Epidemiological Assessment of Keratoconus in Yazd Province in 2008-2009 H.Ziahi MD MR. Jafarinasab MD HM.Katibeh MD F. Karimian MD MR. Shojah MD M.Mahdavi MD MA. Javadi MD Ophthalmologic Reserch Center Shahid Beheshti University(MC)

2. Background Keratoconus is a non-inflammatory, progressive, and usually bilateral disease. Slowly progressive thinning of the cornea is observed and ultimately manifests as corneal ectasia.

3. Background • In recent years, and with regard to etiologies resulting in corneal transplantation, the importance of this disease as one of the most important reasons of corneal blindness, it seems necessary to initially evaluate the current circumstances of the disease in terms of time of diagnosis, demographic information, incidence and prevalence, and signs and symptoms, for national planning to achieve the objectives of the Vision 2020 project.

4. The Incidence of Keratoconus • Few studies have been conducted regarding the estimation of incidence and prevalence of this disease. Presumably, because of the low incidence and prevalence rates, and method of diagnosis which requires much time and is costly, such projects are met with many difficulties.

5. Main Objective • Determining the incidence rate of keratoconus in the Yazd province during one year.

6. Methods • First, necessary information was obtained of the referral centers for suspected patients with keratoconus all over the Yazd province. In addition, the possibility to use hospital and clinical files from previous years was assessed. Then, by referring to clinics, private centers, and referral hospitals for ophthalmology throughout the province, a list was made of specialists and optometrists.

7. Methods • Subsequently, a workshop was assembled for specialists in which study methods, participation approaches, and the project managers were introduced and necessary explanations were provided.

8. Methods • Coordination was made with the local specialists for referral of patients with clinically suspected keratoconus throughout the study period ( 1 year) and they were asked to fill specific forms given to them These forms include • Identification information, • Demographic information, • Results of the patient clinical examination.

9. Methods Referral criteria included one or more of the following problems: • Family history for KCN • VKC • High astigmatism • Best corrected visual acuity lower than 20/20 • Scissor reflex • Vogt stria • Fleischer’s ring, • Corneal thinning

10. Topography

11. Methods • Topographic evaluation was done by two anterior segment experts ophthalmologist at ophthalmic research center and definite or suspected cases were asked to attend in the second eye examination by two anterior segment fellowships and their clinical singes were assessed completely.

12. Results • During the study period 685 patients out of 990818 (0.00066) in Yazd province were selected by ophthalmologists or optometrists • 99 cases were excluded because they had a known KCN in advance • 547 cases entered the study

13. Results • Response rate was 95% (28 patients did not attend for the first topographic evaluation) • Loss to F/U was occurred in 39 patients (7%). They did not attend in the second eye examination after topographic evaluation.

14. Results • After reading topographic images and re-examined patients by anterior segment fellowships, the incidence of KCN and KCN suspect in this province was 22 and 7.8 per 100,000 population respectively.

15. Results

16. Discussion: USA Recent American studies show an incidence and prevalence of 2 and 54.5 persons per 100,000 respectively. Rabinowitz YS. Major Review (Keratoconus). Surv Ophthalmology 1998;42:297-319

17. Discussion: Denmark In a study in 2007 in Denmark, the annual incidence of keratoconus was 1.3 per 100,000 persons and the prevalence was estimated to be 86 per 100,000. Nielsen K, Hjortdal J, Aagaard Nohr E, Ehlers N. Incidence and prevalence of keratoconus in Denmark. Acta Ophthalmol Scand 2007;85:890-2

18. Discussion: UK In 2000, Pearson et al performed a study on the effect of ethnicity on the occurrence and severity of keratoconus. From the hospital files of an area with a 900,000-person population (87% white, 11% Asian, and 2% other) examined over a 10-year period (1989-1998) the following results were obtained. In the 10-44 year age group, the prevalence of keratoconus was 229 and 57 per 100,000 for asians and whites respectively, which demonstrates a relative prevalence of 4 to 1. The annual incidence of keratoconus for the same age group was 19.6 and 4.5 per 100,000 respectively, showing a relative incidence of 4.4 to 1.

19. Discussion: UK A study by Georgion et al in 2004 was conducted to investigate the effect of ethnicity on the occurrence of keratoconus and its relation to atopic diseases. In this retrospective study, new cases of diagnosed keratoconus referred from 1994 to 2000 were included. These patients lived in an area in Yorkshire, UK, with a population of 176,774. The ethnical profile of the population consisted of 82% white, 17% Asian, and 1% other. Among 74 cases, keratoconus was found to be 25 per 100,000 (1 in 4,000) in Asians, compared to 3.3 per 100,000 (1 in 30,000) for whites (p<0.001).

20. Conclusion • The annual incidence of keratoconus in YAZD province is similar to other Asian populations.

21. Acknowledgments Ophthalmic Research Center and Labbafinejad Medical Center,of Shaheed Beheshti University of Medical Sciences. Yazd University of Medical Sciences. All ophthalmologists and Optometrists of Yazd province .