The Value of Trichiasis Surgery in the Gambia: Contrasting the Willingness to Pay and Human Capital Approaches
Kevin D. Frick, Johns Hopkins University-U.S.A.
Trichiasis is a condition in which the eyelashes turn inwards and can scrape the cornea. Trichiasis is a long-term sequela that results from repeated episodes of active trachomatous infection. Trachomatous infection is caused by Chlamydia trachomatous. This is very similar to the organism that causes the sexually transmitted disease, chlamydia, although the serovar types are different. If the trichiasis is untreated, this will eventually lead to corneal opacity and blindness. Trichiasis can be treated with a simple surgical procedure that can be performed by trained ophthalmic nurses.
Studies over time have shown that the demand for trichiasis surgery is generally limited. The reasons for this are not entirely clear and may be as much cultural as economic. The individuals who have trichiasis are rarely asked to pay the full opportunity cost for surgery. However, trachoma and its sequelae are generally found in the most remote areas of the developing countries in which it remains prevalent. Historically, surgery for trichiasis has been available only at regional health centers. Recently, several governments have designed experiments to determine whether or not the individuals who have trichiasis will be more likely to take-up surgery if it is available at a site within the village rather than at a regional health center. The primary motivation for this is decreasing the opportunity costs of time and travel costs that are necessary in order to obtain surgery.
The Gambia is one country in which the utilization of local surgery has been tested. The study was conducted by researchers at the International Centre for Eye Health, the National Eye Care Programme of The Gambia, the London School of Hygiene and Tropical Medicine, and the Medical Resource Council Laboratories (Gambia), with approval from the Gambian Government Ethical Committee. The Johns Hopkins School of Hygiene and Public Health Committee on Human Research has approved the willingness to pay analysis.
The study was designed as a randomized trial. Eight pairs of villages were randomized so that in one of the villages in each pair ophthalmic nurses came to the village to perform surgery, and in the other village in the pair the villagers with trichiasis were required to go to a regional health center for surgery. Individuals were not required to pay the small nominal fee usually required for trichiasis surgery. Prior research has established the existence of a significant difference between the utilization of surgery in the villages in which surgery was available locally and the villages in which individuals had to travel to a regional health center for surgery.
This analysis builds on the original analysis by calculating an "access cost" of surgery for the individuals who need surgery. The travel time and cost of public transportation (where necessary) were provided for all of the 158 villagers with trichiasis in the 16 villages being studied. There was sufficient within village variation to make identification of an access cost effect feasible. The time required for surgery is approximately 20 minutes per eye. Data were available on whether each individual with trichiasis had unilateral (one eye) or bilateral (two eyes) trichiasis. The total access cost was the sum of the public transportation cost, and the total time multiplied by an approximate hourly value of the time of an individual with trichiasis. The initial hourly figure was the average annual value added per agricultural worker (a figure published by the World Bank) converted into dalasis (Gambian currency) and divided by 2000 work hours. Sensitivity analyses are planned that will examine the effect of diminishing the value of the time of individuals with trichiasis based on their visual impairments.
The results of a probit regression indicate a statistically significant and negative relationship between access cost and the utilization of trichiasis surgery. These results are used to calculate the willingness to pay for surgery. The willingness to pay is quite low, around 1% of the annual average value added per agricultural worker. If the individuals are impaired the productivity value that could be gained from surgery that improves their eyesight and productivity is likely to be higher. Neither of these methods considers the externalities that are imposed by the individuals with trichiasis needing either constant care or specific types of eye care from friends and relatives.
The very low willingness to pay could be a function of cultural factors or could be a function of tight credit constraints.