THE DEVELOPMENT OF PHOTOKERATOSCOPE PROTOTYPE FOR ASTIGMATISM DETECTION

• Main Author: Nurftri - Nim: 13313034, Dewi
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/26560
• Institution: Institut Teknologi Bandung

<p align="justify">Astigmatism is a refractive error in which the cornea experiences a change in curvature, causing the image to land on multiple focal point and lead to blurry visions. If not treated accordingly, astigmatism may lead into more serious disease. In order to diagnose astigmatism, topographical information of the cornea is required to analyze the curvature and diopter of the eye. Many innovations of technology have been develop for better diagnosis, one of them is the photokeratoscope. Photokeratoscope is a topographical mapping method that uses a pattern of concentric rings or commonly known as the Placido disk, which is reflected by the cornea and recorded manually or automated for diagnosis. Symmetry and ring space consistency are the main playing factor in photokeratoscopy diagnosis. The healthier the eye, the more symmetrical the reflected Placido pattern and the more consistent the ring spaces. In this study, a photokeratoscope prototype was developed. The image processing algorithm of the prototype was developed to detect: (1) the correlation coefficient K which signifies the symmetry of the reflection and (2) the ring space zr that signifies the ring space consistency. There were 10 different Placido patterns, which were designed independently and tested on 9 different healthy corneas and 2 astigmatic corneas. The B2 pattern showed the best results with K > 0.5 for healthy eyes and K < 0.5 for astigmatic eyes. This pattern also had a ring space zr variation coefficient under 20 %, indicating uniformity and consistency of images from acquisition. The B3 pattern yielded the worst results, where K = 0.625 for the healthy corneas and K = 0,751 for the astigmatic corneas. With B2, the mean of calculated optical power was P = +55.560 ± 1.202 D. This suggests that the optical power calculation is precise, but it still has error compared to the medical standard of optical power in healthy eye, which is +46 D. To alleviate the error, the optical power is multiplied by correction factor, fkoreksi = 0.828. Therefore, the new appropriate optical power was Pkoreksi = +46.000 ± 0.999 D. Overall both the prototype’s hardware and software requires further refinery. However, with the great performance of symmetry calculation algorithm and precise optical power calculation, its clear that this prototype has potential for further development.<p align="justify">