Standardized pachymetry-assisted manual lamellar dissection for Descemet stripping endothelial keratoplasty

Purpose: To present an alternative technique (Pachy-DSEK) for the manual preparation of thin endothelial lamellae in Descemet stripping endothelial keratoplasty (DSEK), as well as to evaluate its visual and anatomic outcomes. Methods: A retrospective chart review was conducted in 15 cases who underwent DSEK at a private eye clinic in Brazil (INOB, Brasília) from June 2017 to December 2019. All patients had ocular comorbidities and relative contraindications to Descemet membrane endothelial keratoplasty (DMEK). All endothelial lamellae were manually prepared by using a standardized technique. Best corrected visual acuity (BCVA), tomographic parameters and graft’s thickness were evaluated preoperatively and at 6 months. Endothelial cell counts were evaluated preoperatively and at 12 to 24 months. Results: During preparation there was one case (6%) of peripheral tear and no tissue was lost. At 6 months, the median BCVA improved from 1.60 to 0.40 logMAR ( p = 0.0009). There was no significant change in anterior ( p = 0.507) and posterior astigmatism ( p = 0.483), anterior ( p = 0.683) and posterior mean keratometry ( p = 0.767), and total corneal power ( p = 0.952). The median central graft thickness at 6 months was 80 µm. Ultrathin grafts (<130 µm) were achieved in 80% of cases. At 12 to 24 months endothelial cell count decreased significantly. Graft’s detachment occurred in two cases (13%) and endothelial rejection in one case (6%). Conclusion: By using ultrasonic pachymetry intra-operatively and standardizing graft preparation, most manually dissected endothelial lamellae were ultrathin. Pachy-DSEK was safe and effective for treating endothelial disfunction in eyes with ocular comorbidities. It may be a cost-effective alternative to automated dissection methods.

Influence of Central Corneal Thickness (CCT) on the Intraocular Pressure (IOP) Measurements Taken From Goldmann Applanation Tonometer, Tonopen, and Airpuff Tonometer.

Introduction: Intraocular pressure (IOP) is one of the basic and most important investigations. Central corneal thickness influences IOP measured by various devices. Objective: In this study, we attempt to determine the agreement and influence of the central corneal thickness in the measurement of IOP obtained by Goldman applanation tonometer, Airpuff tonometer and tonopen. Methodology: A cross-sectional analytical study of Central corneal thickness (CCT) was done using Ultrasonic pachymetry. IOP was adjusted using Ehler's formula. Mean and the standard deviation was measured using the observed and predicted values for each instrument for its accuracy irrespective of the CCT. Results: 200 eyes of 100 patients were included in the study. Mean IOP measured was 16mmHg (SD 4). Tonopen was found to have closer observed values when compared with the predicted values to IOP obtained by Goldmann's applanation tonometer after CCT adjustments with Mean difference of 0.0134 mmHg with SD of 0.814. Air Puff tonometer was found to be the least accurate with Mean difference -2.08mmHg and SD of 4.704. Linear regression analysis also predicted that while the tonopen tend to underestimate the IOP levels by 5 %, Airpuff tonometer had a tendency to overestimate the IOP by 13%.(p<0.05). Conclusion: Tonopen had the greatest agreement and significant correlation with the GAT over a range of IOP and CCT and replicate measurements that are closest to the values obtained by using GAT after CCT adjustments. CCT adjustments may not even be required or has very little influence on IOP when using Tonopen.

CENTRAL CORNEAL THICKNESS

Objectives: To compare central corneal thickness in myopic and keratoconuseyes by ultrasound pachymetry and pentacam HR. Study Design: Cross sectional study.Setting: Qassim University, Optometry Clinics, Kingdom of Saudi Arabia. Period: October2016 to April 2017. Methodology: One hundred myopic and keratoconus participants. CentralCorneal Thickness (CCT) were measured with two techniques by ultrasonic pachymetry andpentacam HR in two groups. Group one consisted of 80 myopic participants and group two of 20Keratoconuspatients.Pentacamreadings were recorded first. CCT were compared and analyzedstatistically using unpaired t-test and histogram. Results: One hundred participants (100) wereincluded in which 80 participants were myopic and 20 with keratoconus. Both eyes (200) of allthe participants were examined. Age of the myopics ranged from 18-30 years (Mean=23.03).The mean value with ultrasound pachymetery was 555μm (SD±32.021) and with pentacam566μm (SD±37.367). We observed a tendency of overestimation of CCT measurements withpentacam. Statistically a significant difference of reading between two devices (P<0.001) wasfound. In keratoconus participants, the mean age was 23.7 years (21- 26). The mean CCT takenwith Pentacam HR and US Pachymetry was 476μm (SD± 16.980) and 465μm (SD± 35.868)respectively. The t-test showed no statistical difference between thepentacam HR andultrasound pachymetry (p>0.214). Conclusion: Measurements of central corneal thicknessdone with Ultrasound Pachymeter and Pentacam HR are closely related to each other andare interchangeable when used in normal refractive error cases. While in Keratonus patientsultrasound pachymetry is preferred because of its reliability.