Mitsugu Shimmyo

The relationship between corneal hysteresis and the magnitude of intraocular pressure reduction with topical prostaglandin therapy

Aims To evaluate corneal hysteresis (CH) and intraocular pressure (IOP) before and after IOP lowering with prostaglandin analogue (PGA) therapy in medication-naïve eyes. Methods In this retrospective study, we included records from 57 consecutive patients with open angle glaucoma who were initiated on PGA. Patients underwent ocular response analyser measurement with IOP assessment at baseline (untreated) and at follow-up (treated). Results Median follow-up time between IOP measurements was 1.4 (range 0.4–13.5) months. IOP was reduced by 3.2 mm Hg (18.8%) from 17.0 to 13.8 mm Hg (p<0.001). CH increased by 0.5 mm Hg (5.2%) from 9.7 to 10.2 mm Hg (p=0.02). Baseline CH (but not baseline central corneal thickness) was a significant predictor of the magnitude of IOP reduction, with patients in the lowest quartile of CH (mean 7.0 mm Hg) experiencing a 29.0% reduction in IOP while those in the highest CH quartile (mean 11.9 mm Hg) experienced a 7.6% reduction in IOP (p=0.006). A multivariate analysis controlling for baseline IOP demonstrated that baseline CH independently predicted the magnitude of IOP reduction with PGA therapy in both per cent (ß=3.5, p=0.01) and absolute (ß=0.6, p=0.02) terms. Conclusion Although CH is influenced by IOP, baseline CH is independently associated with the magnitude of IOP reduction with PGA therapy.

Evaluation of agreement between intraocular pressure measurements using Goldmann applanation tonometry and Goldmann correlated intraocular pressure by Reichert's ocular response analyser

PurposeTo compare agreement of intraocular pressure (IOP) measurements using Goldmann applanation tonometry (GAT) and Goldmann correlated intraocular pressure generated (IOPg) by the Reichert ocular response analyser (ORA).MethodsConsecutive patients presenting for glaucoma evaluation underwent ORA assessment followed by examination including GAT. For each ORA assessment, measurements were taken until a waveform score (WS) of 6.5 was obtained or until five measurements were obtained per eye. The relationship between GAT and IOPg and the influence of the WS upon this relationship was evaluated. A Bland–Altman plot and linear regression were used to determine agreement between GAT and IOPg.ResultsA total of 518 eyes of 260 patients were included in the final analysis. Increasing WS was found to predict a smaller difference between GAT and IOPg (β=−0.2, P⩽0.001). Selecting the highest WS among ORA assessments of each eye, WS continued to predict concordance between GAT and IOPg (β=−0.2, P=0.006). The mean IOP difference between methods was 0.1 mm Hg (±0.3), which was found to be statistically insignificant (P=0.391). This relationship between GAT and IOPg was successfully validated using a second distinct data set of 100 eyes. GAT and IOPg measurements varied by 2 mm Hg or less in 53.9% of eyes and 5 mm Hg or less in 92.3% of eyes.ConclusionIn clinical practice IOPg is strongly related to GAT. Although higher WS is indicative of greater IOPg/GAT concordance, its influence is minimal. This study does not support the use of a specific WS cutoff to determine quality of an IOPg measurement.

Goldmann applanation tonometry compared with corneal-compensated intraocular pressure in the evaluation of primary open-angle Glaucoma

BackgroundTo better understand the role of corneal properties and intraocular pressure (IOP) in the evaluation of primary open-angle glaucoma (POAG); and to determine the feasibility of identifying glaucomatous optic neuropathy (GON) using IOP corrected and uncorrected for corneal biomechanics.MethodsRecords from 1,875 eyes of consecutively evaluated new patients were reviewed. Eyes were excluded if central corneal thickness (CCT) or Ocular Response Analyzer (ORA) measurements were unavailable. Presence or absence of GON was determined based on morphology of the optic disc, rim and retinal nerve fiber layer at the time of clinical examination, fundus photography and Heidelberg Retinal Tomography. Goldmann-applanation tonometry (GAT) in the untreated state was recorded and Goldmann-correlated (IOPg) and corneal-compensated IOP (IOPcc) were obtained using the ORA. Glaucomatous eyes were classified as normal or high-tension (NTG, HTG) using the conventional cutoff of 21 mm Hg. One eligible eye was randomly selected from each patient for inclusion.ResultsA total of 357 normal, 155 HTG and 102 NTG eyes were included. Among NTG eyes, IOPcc was greater than GAT (19.8 and 14.4 mm Hg; p < 0.001) and the difference between IOPcc and GAT was greatest for this subgroup of patients with NTG (p ≤ 0.01). The maximum combined sensitivity and specificity for detection of GON occurred at 20.9 mm Hg for GAT (59%, 90%) and 18.4 mm Hg for IOPcc (85%, 85%) and the area under the curve was greater for IOPcc (0.93 vs. 0.78; p < 0.001).ConclusionsIOPcc may account for measurement error induced by corneal biomechanics. Compared to GAT, IOPcc may be a superior test in the evaluation of glaucoma but is unlikely to represent an effective diagnostic test.

Change in corneal hysteresis over time in normal, glaucomatous and diabetic eyes

Corneal hysteresis (CH) is lower in glaucomatous eyes. The aim of this study was to determine and compare the change in CH over time between normal, open angle glaucoma (POAG) and diabetic subjects.

Corneal hysteresis following descemetorhexis with endokeratoplasty: early results.

The corneal biomechanical properties following descemetorhexis with endokeratoplasty (DXEK) and in normal subjects were studied in 100 eyes (12 DXEK and 88 age-matched normal subjects). Corneal hysteresis measurements were significantly lower in DXEK vs normal subjects. DXEK has a direct effect on corneal hysteresis and corneal biomechanical properties of the human cornea.

Association between corneal hysteresis and the magnitude of intraocular pressure decrease after cataract surgery

Purpose To evaluate the relationship between baseline corneal hysteresis (CH) and the change in intraocular pressure (IOP) before and after cataract extraction in patients without glaucoma. Setting Private practice, New York City, New York, USA. Design Retrospective cohort study. Methods Charts of consecutive patients who had phacoemulsification cataract extraction with posterior chamber intraocular lens implantation were analyzed. All included patients had preoperative and postoperative measurements with the Ocular Response Analyzer 2 to 4 months and 10 to 12 months postoperatively. Data collected included age, baseline CH, baseline central corneal thickness (CCT), and IOP. Results Thirty nine (65 eyes) of the 230 patients met the inclusion criteria. The mean patient age was 70.8 years ± 8.6 (SD). The mean preoperative, 2‐ to 4‐month and 10‐ to 12‐ month postoperative IOP values were 14.8 ± 3.5 mm Hg, 11.9 ± 3.4 mm Hg, and 12.6 ± 3.1 mm Hg, respectively (P < .05 for comparisons with preoperative IOP). The baseline CH was not predictive of the IOP reduction at 2 to 4 months (&bgr; = −0.3; 95% confidence interval [CI], −0.7 to 0.01; P = .06). However, the baseline CH (but not the baseline CCT) was statistically associated with the magnitude of IOP reduction at 10 to 12 months when controlling for patient age (&bgr; = −0.5; 95% CI, −0.8 to −0.1; P = .01). Conclusion A low baseline CH was associated with a larger magnitude of IOP reduction after cataract extraction. Financial Disclosure Dr. Radcliffe is a consultant to Reichert Technologies and Glaukos Corp.; a consultant to and speaker for Allergan, Inc., Alcon Laboratories, Inc., Iridex Corp., Merge Healthcare, Carl Zeiss Meditec AG; and a speaker for Merck Pharmaceuticals. No other author has a financial or proprietary interest in any material or method mentioned.