Efficacy of intacs intrastromal corneal ring segment relative to depth of insertion evaluated with anterior segment optical coherence tomography

To evaluate the effect of implantation depth of Intacs microthin prescription inserts [Addition Technology Inc, Fremont, California] on visual and topographic outcomes in patients with post- laser-assisted in situ keratomileusis [LASIK] ectasias. Retrospective, observational case series. In this case series, 16 eyes of 12 patients were evaluated. All cases were post-LASIK ectasia that had undergone intrastromal corneal ring segment [ICRS] implantation. The planned insertion depth was 70% of stromal thickness using a manual dissector. At least 12 months postoperatively, all eyes underwent Visante [Carl Zeiss Meditec] AS-OCT to determine insertion depth. Cases were categorized into 3 groups based on the measured implantation depth: 40-59% thickness; 60-79% thickness; and >/= 80% thickness. Visual, refractive and topographic outcomes were evaluated relative to implantation depth. The lowest improvement in the study parameters ocurred when the implantation depth was >/= 80%. In this group, uncorrected visual acuity [UCVA] and best spectacle corrected VA [BSCVA] improved less than 0.5 lines. Manifest refractive spherical equivalent [MRSE] and mean keratometry [Km] change was less than 0.5 diopters [D]. The greatest improvements were observed with implantation depth of 60-79% where UCVA and BSCVA increased by 4.5 and 2.5 lines respectively, and MRSE and Km changed by approximately 2.00 D. Less improvement was found when ICRS were implanted between 40-59% of stromal thickness. Implantation of ICRS greater than 80% of stromal thickness may have no effect on visual and topographic status

Prevalence of calibration errors in Goldman applanation tonometers

To determine the prevalence of calibration errors in Goldmann applanation tonometers at Farabi Eye Hospital. This cross-sectional study was performed on all tonometers in use at Farabi Eye Hospital. All Haag-Streit Goldmann applanation tonometers were checked according to the manufacturer's method by two independent observers and by a third observer in case of mismatched results. Calibration errors were classified into 6 categories of +/- 0.5, +/- 1, +/- 1.5, +/- 2, +/- 2.5 and more than +/- 2.5 mmHg. Overall, 43 Goldmann tonometers were evaluated. There were 3 [7%], 10 [24.3%], 16 [38.3%], 24 [56.9%], 31 [72.1%] and 12 [27.9%] tonometers within calibration errors of +/- 0.5, +/- 1, +/- 1.5, +/- 2, +/- 2.5 and more than +/- 2.5 mmHg respectively. Goldmann tonometers were not within the manufacturer's recommended range [ +/- 0.5 mmHg] in 93%, and not within the acceptable range of +/- 2.5 mmHg in 28% of checked devices. Further study is needed to demonstrate the correlation between calibration errors and clinical errors

A reappraisal of the capsulorhexis:tearing angle in capsulorhexis / 国际眼科杂志(Guoji Yanke Zazhi)

ATM:To determine the tearing angle and tearing force,and effects of associated pressures in tearing of various materials and human lens capsule in continuous curvilinear capsulorhexis(CCC).METHODS:Tearing was done on different materials such as aluminum Iaminated paper,different types of thin transplant plastics and human Iens capsule with blunt tip needle.During the procedure,angle and direction of force were measured.Effects of increased underlying pressure on tearing of tearable materials and effect of anterior chamber depth and vitreous pressure on 24 postmortem hunlan eyes with different ages (range from10 to 75 years),was evaluated.RESULTS:Tearing angle in every material was unique for that material.Angle and force of tearing was decreased reversely with increasing age (from 85 degree in a 10-years-old to 10 degree in older than 50 years).Increasing vitreous pressure and decrease in AC depth causes higher pressure on point of tearing.Safe methods in controlling CCC are discussed jn the context.OONCLUSION:Understanding the physics and vector of forces during CCC is necessary in good performance and avoidance of radial tears.Onange in capsular properties between difierent ages and different type of cataract causes different tearing angle and tearing force that should be considered during CCC.