Through multiple discussions and testing, it was agreed that the current diagnostic tool is unsatisfactory at this point in the project as such this summer it is my goal to improve the diagnostic process. This week I researched different alternatives to our diagnostic tool and found multiple solutions (one being remarkably similar because as I found out, the diagnostic tool design is based upon a device called the focometer). Anyways while researching I found that most groups who have the same goals as ProSEC have attempted to address the issue of creating access to affordable eye-care by bringing in ophthalmologists and other doctors for 2-3 day camps to prescribe and then make as many glasses as time allows for the people of underdeveloped areas. Despite the success of these programs, we aim for a solution that allows for the locals to learn how to diagnose and make the glasses without the ophthalmologists and so that the locals can create and sustain a business out of our solution.
Considering the shortcomings of our device, I looked into other diagnostic tools that similar programs have used. The three ‘most common’ solutions include a device called the focometer, AdSpecs, predetermined lens refraction and traditional subjective refraction of course.
The focometer is the device upon which our telescope diagnostic device is based. It only uses two lenses to measure the refractive error of a patient’s eyes through a large range. The advantage to a design like this is that only two lenses are necessary. However, the problem is that we are having trouble teaching the patients to distinguish/recognize when the chart is in focus which then throws off the diagnosis. In my opinion, the focometer represents the ‘best case scenario’ for our telescope device because of the way it is made. The focometer is probably (again this is simply my assumption) the most accurate any device of its kind can achieve. One study performed by a group that traveled to Nicaragua with the focometer indicated that the focometer was the best alternative to traditional subjective refraction as performed by an ophthalmologist in the clinical trial in the United States. However, when the same study was performed in Nicaragua, the focometer was not the superior alternative. This made me reconsider our current tool and the results of the trip to Guatemala. It made me think that perhaps we are exploring the wrong type of device; despite the fact that I think that our telescope is a strong design and that we can improve in our accuracy by changing the procedure and directions, there is a limit to how good we can actually get with the telescope device.
Taking into consideration that subjective refraction by a doctor has proved to be the best at determining the refractive error of a patient’s eyes, perhaps it is a good idea to find a process that more closely resembles this procedure as compared to the telescoping device. One idea that has been proposed is to make our own phoropter or simple a single sided set of trial lenses with a series of lenses which additively can cover a range of prescriptions (negative and positive). To save money and lenses, it may be a better idea to have a ‘single eyed’ device design. Making two single eye devices is an option; one can contain negative lenses while the other has all positive. One possible idea is to use a rough method of having a patient read the Snellen chart from different distances and asking for clarity whether one distance is superior to another. Another option for this method to determine near sighted or far-sighted is to do the first scan of retinoscopy (look for with or against motion) and then choosing the appropriate set. With the help of the diagnostician, the patient will go through the set of lenses to see which allows for optimal vision. With regard to astigmatism, the clock can still be used just as it was for the scope device; the lens which brings the first line into focus is the spherical error and the difference between the second lens diopter power (lens brings the line perpendicular to the first into focus) is the cylindrical error. The orientation of the second line is noted to give the astigmatic axis for the glasses. It should be noted that there will most likely be ‘stack up error’ as the lenses will be additive to save money (less lenses are needed with a specific combination of lenses- i.e. have a -1 and -2 lens in order to achieve a -3 prescription). I predict that the error caused by the stack up will be minimal but still will be a factor of concern. The fine tuning of this device will be in the form of a smaller powered diopter (one at let’s say +0.5 diopters and the other -0.5) that will be in each single eye device that can be added or subtracted at the end based upon the patient’s preference. The other advantage to a device like this is that we can account for malingering using a plano lens.
Nicaragua study : http://www.neco.edu/library/theses/KSmithThesisMay08.pdf