title: Keratometry device for surgical support.
abstract: BACKGROUND
  High astigmatisms are usually induced during corneal suturing subsequent to tissue transplantation or any other surgery which involves corneal suturing. One of the reasons is that the procedure is intimately dependent on the surgeon's skill for suturing identical stitches. In order to evaluate the influence of the irregularity on suturing for the residual astigmatism, a prototype for ophthalmic surgical support has been developed. The final intention of this prototype is to be an evaluation tool for guided suture and as an outcome diminish the postoperative astigmatism.
  
  
  METHODS
  The system consists of hand held ring with 36 infrared LEDs, that is to be projected onto the lachrymal film of the cornea. The image is reflected back through the optics of the ocular microscope and its distortion from the original circular shape is evaluated by developed software. It provides keratometric and circularity measurements during surgery in order to guide the surgeon for uniformity in suturing.
  
  
  RESULTS
  The system is able to provide up to 23D of astigmatism (32D - 55D range) and is +/- 0.25D accurate. It has been tested in 14 volunteer patients intraoperative and has been compared to a commercial keratometer Nidek Oculus Hand-held corneal topographer. The correlation factors are 0.92 for the astigmatism and 0.97 for the associated axis.
  
  
  CONCLUSIONS
  The system is potentially efficient for guiding the surgeon on uniformity of suturing, presenting preliminary data indicating an important decrease on the residual astigmatism, from an average of 8D - for patients not submitted to the prototype guidance - to 1.4D - for patients who have actually been submitted to the prototype guidance - after the first 24 hours post-surgery and in the subsequent weeks. It also indicates that the surgeon should achieve circularity greater or equal to 98% in order to avoid postoperative astigmatisms over 1D.
  
  
  BACKGROUND
  
  
  
  BACKGROUND
  CAAE - 0212.0.004.000-09.
authors.affiliation: Dept of Elect Engineering USP (Ophthalmic Instrumentation Division), Av Trabalhador sao-carlense 400, S Carlos, SP 13566-590, Brasil. lilianeventura@usp.br
authors.forename: Liliane
authors.initials: L
authors.lastname: Ventura
authors.forename: Jean-Jacques
authors.initials: JJ
authors.lastname: De Groote
authors.forename: Paula
authors.initials: P
authors.lastname: Saia
authors.forename: Sidney J
authors.initials: SJ
authors.lastname: Faria e Sousa
mesh_terms: D000465:Algorithms; D001251:Astigmatism / Q000517:prevention & control*; D003199:Computer Systems; D003315:Cornea / Q000033:anatomy & histology* / Q000601:surgery; D019781:Corneal Topography / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D006801:Humans; D007091:Image Processing, Computer-Assisted; D011183:Postoperative Complications / Q000517:prevention & control*; D012984:Software; D016683:Supine Position; D025321:Surgery, Computer-Assisted / Q000295:instrumentation* / Q000379:methods; D013536:Suture Techniques / Q000009:adverse effects