Efstathios T. Detorakis

Ocular rigidity: biomechanical role, in vivo measurements and clinical significance.

Ocular rigidity (OR) refers to the relationship between pressure and volume changes in the eyeball. Since the description of the differential tonometry method for the calculation of an OR coefficient by Friedenwald, several other methodologies have been proposed to measure OR, including the anterior chamber manometry, axial length (AL) changes, measurement of pulse amplitude and fundus pulse, ultrasound elastography and evaluation of corneal hysteresis. However, most of these methodologies suffer from deficiencies, such as invasive nature, poor accuracy or reproducibility or technical complexity. Nevertheless, it is possible that OR affects the pathogenesis and clinical course of a variety of ocular conditions, including glaucoma, age‐related macular degeneration, presbyopia, corneal changes following refractive surgery as well as the accuracy of IOP measurements by many tonometers. Thus, the future development of non‐invasive and easy‐to‐use methodologies for the accurate measurement of OR in the every‐day practice would be clinically important.

Central Corneal Mechanical Sensitivity in Pseudoexfoliation Syndrome

Purpose: Corneal involvement and disturbances of the tear film have been reported in pseudoexfoliation syndrome (PEX). Tear film deficiencies are correlated with changes in corneal sensitivity. The present study aims at evaluating central corneal mechanical sensitivity (CCMS) in PEX. Methods: Patients with unilateral or bilateral PEX findings constituted the study group (SG). Age- and gender-matched patients without PEX in either eye constituted the control group (CG). Patients with conditions affecting corneal sensitivity were excluded. CCMS and central corneal thickness (CCT) were measured (using a Cochet-Bonnet esthesiometer and an ultrasonic pachymeter, respectively). Schirmer (ST) and break-up time (BUT) tests were also performed. Results: The SG included 40 patients (24 male, 60%). The CG included 38 patients (25 male, 65.78%). ST scores were significantly lower in the SG compared with the CG (11.45 ± 2.52 mm and 14.27 ± 1.18 mm, respectively, P = 0.04). BUT scores were also significantly lower in the SG compared with the CG (7.64 ± 2.37 mm and 12.43 ± 3.14 mm, respectively, P = 0.03). CCMS was significantly (P = 0.02) reduced in the SG compared with CG (4.54 ± 0.23 cm and 5.73 ± 0.44 cm, respectively). Differences in CCT between the SG and the CG were not statistically significant. Conclusions: The decrease in CCMS in PEX eyes may be related to decreased BUT and ST scores in PEX, as previously described. However, a direct involvement of sensory nerves may also participate. The reduction in CCMS may have implications for the clinical management of PEX patients.

Ocular rigidity, ocular pulse amplitude, and pulsatile ocular blood flow: the effect of axial length.

PURPOSE Previous studies have shown a negative correlation between axial length (AL) and pulsatile ocular blood flow (POBF). This relation has been questioned because of the possible confounding effect of ocular volume on ocular rigidity (OR). The purpose of this study was to investigate the relation between AL, as a surrogate parameter for ocular volume, and OR, ocular pulse amplitude (OPA), and POBF. METHODS Eighty-eight cataract patients were enrolled in this study. A computer-controlled device comprising a microdosimetric pump and a pressure sensor was used intraoperatively. The system was connected to the anterior chamber and used to raise the intraocular pressure (IOP) from 15 to 40 mm Hg, by infusing the eye with a saline solution. After each infusion step, the IOP was continuously recorded for 2 seconds. Blood pressure and pulse rate were measured during the procedure. The OR coefficient was calculated from the pressure volume data. OPA and POBF were measured from pressure recordings. RESULTS Median AL was 23.69 (interquartile range 3.53) mm. OR coefficient was 0.0218 (0.0053) μL(-1). A negative correlation between the OR coefficient and AL (ρ = -0.641, P < 0.001) was documented. Increasing AL was associated with decreased OPA (ρ = -0.637, P < 0.001 and ρ = -0.690, P < 0.001) and POBF (ρ = -0.207, P = 0.053 and ρ = -0.238, P = 0.028) at baseline and elevated IOP, respectively. CONCLUSIONS Based on manometric data, increasing AL is associated with decreased OR, OPA, and POBF. These results suggest decreased pulsatility in high myopia and may have implications on ocular pulse studies and the pathophysiology of myopia.

Evaluation of the acoustic function in pseudoexfoliation syndrome and exfoliation glaucoma: Audiometric and tympanometric findings

Purpose Previous studies have reported increased audiometric thresholds in patients with pseudoexfoliation syndrome (XFS), compared with normative data. This study examines mean audiometric thresholds and tympanometric peak values in patients with XFS and in a control group. Methods This is a prospective, nonrandomized control case study. Patients with XFS in one or both eyes constituted the study group (SG). Patients without XFS in either eye constituted the control group (CG). Patients with a history of conditions affecting hearing function were excluded. The SG and the CG included 54 and 48 patients, respectively. Pure tone hearing thresholds levels were measured at 0.25, 1, 2, 3, and 8 kHz. Tympanometric peak values were also recorded. Differences in audiometric mean threshold values and tympanometric peak values between SG and CG, as well as between glaucomatous and nonglaucomatous eyes, were examined. Results Bone and air audiometric thresholds were significantly increased in SG for 3 kHz and 8 kHz but not for 0.25 kHz, 1 kHz, and 2 kHz. Tympanometric peak values were significantly lower in SG compared with CG. In SG, glaucomatous patients had significantly higher air-conduction thresholds for 3 kHz and 8 kHz. Differences in bone and air audiometric findings as well as tympanometric findings between glaucomatous and nonglaucomatous patients were statistically not significant in CG. Conclusions The results agree with previous reports on sensorineural hearing loss in XFS. The reduced tympanometric peak values in SG imply impairment in the elastic properties of the middle ear in XFS. The findings provide additional evidence for the systemic nature of XFS.

Lower eyelid laxity in functional acquired epiphora: evaluation with quantitative scintigraphy.

Purpose: The examination of lacrimal drainage is often based on qualitative criteria. This study uses quantitative scintigraphy to evaluate “functional” epiphora. Methods: Thirty-two patients with functional epiphora (no morphologic abnormalities of the conjunctiva and eyelids, a patent nasolacrimal duct on irrigation, and no anatomical stenosis on dacryocystography) were studied (study group, SG). Twenty-two individuals without epiphora were also examined (control group, CG). Fifty microliters of Technetium-99m was instilled into the conjunctival cul-de-sac. Time-activity curves were then constructed, and conjunctival lacrimal clearance (CLC) at 2.5, 5, 7.5, and 10 minutes was calculated. Differences in CLC between the SG and the CG and correlations between CLC and horizontal and median tendon laxity and eyelid length in the SG were examined. Results: The SG had significantly reduced CLC at 2.5 and 5 minutes, compared with the CG (p = 0.01 and p = 0.04, respectively), whereas respective differences at 7.5 and 10 minutes were not statistically significant. In the SG, CLC at 2.5 and 5 minutes was significantly correlated with horizontal and median tendon laxity. The respective correlation with eyelid length was not statistically significant. Furthermore, in the SG, CLC at 2.5 and 5 minutes was significantly correlated with patient age (p = 0.03 and p = 0.04, respectively). Differences in CLC between men and women were not statistically significant at all intervals. Conclusions: The correlation between eyelid laxity and CLC supports the role of the eyelid “pump” in lacrimal drainage. CLC at 2.5 and 5 minutes may be used to decide treatment methods for functional epiphora.

Crete, Greece glaucoma study.

Purpose: To investigate the prevalence of primary open‐angle glaucoma (POAG) in a randomized sample of the inhabitants of the island of Crete. Patients and Methods: In 18 different villages in all four prefectures of the island of Crete, patients were randomly selected from 1993 through 1998, and an in situ study was accomplished. The sampling fraction (covered by the 1991 census) in each village was approximately 5%. Patients were considered to have POAG when the morphologic aspect of a glaucomatous optic disc was present, and/or a nerve fiber layer defect and a visual field defect was present. The presence of Pseudoexfoliation syndrome (PEX) and pseudoexfoliative glaucoma (PEXG) was also investigated. Results: The prevalence of glaucoma in Crete was 2.80%. Of those diagnosed with POAG, 9.67% had an intraocular pressure (IOP) under 21 mm Hg, and 25.80% had PEX. The prevalence of simple ocular hypertension without glaucoma was found in 6.58% of the patients. The ratio of subjects with hypertensive glaucoma to those with simple ocular hypertension was 1:2.6. Conclusion: The prevalence of POAG and exfoliation glaucoma appears to be quite high in Crete. Further research will be needed to set more accurate criteria for earlier diagnosis and to enable more efficient organization of the health care system.

Microbiological Examination of Bandage Soft Contact Lenses Used in Laser Refractive Surgery

BACKGROUND Disposable soft contact lenses are known to be colonized by bacteria and play a key role in bacterial keratitis pathogenesis. Such lenses, commonly used after laser refractive surgery procedures in which postoperative corneal infiltrations are sometimes observed, are potentially a substrate for bacterial inoculation. This study evaluates the extent of such a contamination. METHODS Sixty disposable lenses collected from 60 eyes of patients who underwent photorefractive keratectomy (PRK), photoastigmatic refractive keratectomy (PARK), or laser in situ keratomileusis (LASIK) for the treatment of myopia or hyperopia were collected under sterile conditions over 4 months and cultured in various media. Results were statistically analyzed and the correlation with clinical and epidemiological data was examined. RESULTS Eleven (18.3%) of the examined lenses were contaminated with Staphylococcus epidermidis. No other bacteria or fungi were found. Contamination was significantly more common among female patients (P = .036). Correlation with the other clinical or operative parameters examined was statistically insignificant. CONCLUSIONS Contamination was independent of the surgical procedure and females who were frequent users of eyelid cosmetics displayed higher contamination frequencies, suggesting that bacteria possibly originate from eyelid flora. The isolation of Staphylococcus epidermidis requires close postoperative surveillance, since it is a known cause of keratitis. Prophylactic postoperative treatment with tobramycin, gentamycin, or sulphonamides could be indicated.

Watery eye following patent external DCR: an MR dacryocystography study.

Purpose: To examine patients with persistent watery epiphora following patent external dacryocystorhinostomy (DCR) with magnetic resonance imaging dacryocystography (MR-DCG). Methods: Patients with unobstructed nasolacrimal irrigation following external DCR were included. Five patients with watery epiphora constituted the study group (SG). Five patients without epiphora constituted the control group (CG). All patients underwent MR-DCG following the instillation of artificial tears in the conjunctival fornix. The osteotomy site was identified in T1-weighted coronal images. Lacrimal flow was assessed with modified T2-weighted (True Fast Imaging Steady State Pulse, “TrueFISP”) coronal images before and 10 min after repeated blinking. Signal intensities at three regions of interest (ROIs), corresponding to the eyeball (ROI-1), conjunctival sac (ROI-2), and anastomotic site (ROI-3) were measured. Results: Differences in the diameter of both osseous and soft tissue ostia between SG and CG were statistically not significant. A post-blink increase in signal intensity at ROI-3 was noted in both groups, whereas differences in signal intensity for ROI-1 and ROI-2 were statistically not significant. The post-blink signal intensity increase in ROI-3 was significantly more pronounced in the CG, compared with the SG. Conclusions: The fact that signal intensity increase at ROI-3 was less pronounced in the SG, compared with CG, implies a compromised “lacrimal pump” mechanism in the former group. The methodology presented may be used for the evaluation of post-DCR epiphora.

MRI Evaluation of Lacrimal Drainage After External and Endonasal Dacryocystorhinostomy

Purpose: External and endonasal dacryocystorhinostomy (EX-DCR and EN-DCR, respectively) affect the tear drainage mechanism. This study evaluates the preservation of “lacrimal pump” function in both procedures. Methods: Cases of successful EN-DCR (4 patients) and EX-DCR (4 patients) were included. All patients underwent MRI of the rhinostomy areas, at least 6 months postoperatively. The vertical diameter of rhinostomy (both osseous and soft-tissue apertures) was measured in T1-oriented images, whereas the signal intensity levels were examined for 3 regions of interest (ROIs) in T2-oriented (true fast imaging steady state pulse) images with instillation of normal saline to the conjunctival fornices, both before and after blinking (activation of the “lacrimal pump”). ROI 1 corresponded to the globe (control), ROI 2 corresponded to the inferior conjunctival fornix, and ROI 3 corresponded to the rhinostomy site. Results: Signal intensity in ROI 3 (rhinostomy) was significantly increased after blinking in both EX-DCR and EN-DCR cases. The increase was significantly higher in the latter. Signal intensity changes in ROI 3 were significantly correlated with rhinostomy size in both groups, whereas the respective correlations with the postoperative interval were not statistically significant. Conclusions: Findings imply that the “lacrimal pump” is active following DCR and may be better preserved in the EN-DCR than in the EX-DCR group. Persistent epiphora after patent DCR may thus be attributed to a defective “pump” function and treated accordingly.

Corneal topography in involutional ectropion of the lower eyelid: preoperative and postoperative evaluation.

Purpose: The shape and position of the eyelids affect corneal topography. This study evaluated preoperative and postoperative corneal topography in involutional ectropion of the lower eyelid. Methods: Eighteen patients with unilateral involutional lower eyelid ectropion underwent ophthalmic examinations and corneal topography before surgical correction and at the 6-month postoperative interval. Corneal topographies were evaluated with the Holladay Diagnostic Summary package. The fellow eyes served as controls. Parameters evaluated included the regularity of astigmatism (RA), steep refractive power (SRP), flat refractive power (FRP), and total astigmatism (TA). Results: Preoperatively, RA was found significantly decreased in the eyes with ectropion compared with the fellow eyes, whereas differences in other parameters were statistically nonsignificant. Postoperatively, RA was significantly increased, whereas SRP was significantly reduced. The percentage of eyes with with-the-rule astigmatism (WTRA) was increased postoperatively, although astigmatic axis changes were not systematic. Conclusions: Postoperative topographic changes may be related to either restoration of symmetry in the upper and lower lid apposition on the cornea or to rearrangement of the tear film. Further research will be required to assess whether corneal topographic findings could be used as an index of the severity of eyelid laxity and to evaluate the effects of topographic changes on corneal and total optical aberrations.