Isaac Avni

Central corneal thickness measurement with the Pentacam Scheimpflug system, optical low-coherence reflectometry pachymeter, and ultrasound pachymetry

PURPOSE: To assess the intraoperator repeatability and interoperator reproducibility of central corneal thickness measurements by the Pentacam Scheimpflug imaging system (Oculus) and the optical low‐coherence reflectometer (OLCR) pachymeter (Haag‐Streit) and to compare them with those of ultrasound (US) pachymetry. SETTING: Assaf Harofe Medical Center Ophthalmology Outpatient Clinic, Zerifin, Israel. METHODS: Repeatability was determined from 10 successive measurements in each of 4 healthy patients. Reproducibility for the Pentacam Scheimpflug system was determined from measurements by 2 operators in each of 24 patients; in these 24 patients, central corneal thickness measurements were compared between the Pentacam and US pachymetry. For the OLCR pachymeter, reproducibility was determined from measurements by 2 operators in each of 16 patients, in whom central corneal thickness was also measured with the Pentacam. RESULTS: Mean coefficient of repeatability was 0.84% for the Pentacam Scheimpflug system and 0.33% for the OLCR pachymeter. For the Pentacam, the coefficient of interoperator reproducibility was 1.10% and the 95% limits of agreement were −10.2 μm to +11.9 μm. Mean difference between Pentacam and US was 6.09 μm. For the OLCR pachymeter, the coefficient of interoperator reproducibility was 0.59% and the 95% limits of agreement were −5.4 μm to +7.0 μm. Mean difference between central corneal thickness values obtained with the OLCR pachymeter and Pentacam Scheimpflug system was 1.7 μm. CONCLUSIONS: Objective, noncontact measurement of central corneal thickness with the Pentacam Scheimpflug system and OLCR pachymeter was convenient and yielded excellent intraoperator repeatability and interoperator reproducibility. Central corneal thickness values obtained with the Pentacam were similar to those obtained with both the OLCR pachymeter and an US pachymeter. Further research is needed to corroborate whether central corneal thickness measurements by the Pentacam and OLCR devices can be used interchangeably and are more clinically useful than US pachymetry.

Effect of diabetes mellitus on biomechanical parameters of the cornea.

PURPOSE: To compare parameters of biomechanical response of the human cornea measured as corneal hysteresis (CH) and corneal resistance factor (CRF) in patients with diabetes mellitus and healthy control subjects. SETTING: Department of Ophthalmology, Assaf Harofeh Medical Center, Zerifin, Israel. METHODS: In the right eye of each participant, the CH, CRF, Goldmann‐correlated intraocular pressure (IOPg), and corneal‐compensated intraocular pressure (IOPcc) were measured with the Ocular Response Analyzer. Central corneal thickness (CCT) was measured by ultrasonic pachymetry and intraocular pressure by Goldmann applanation tonometry (IOP GAT). Findings were compared between the 2 groups (control and diabetic). RESULTS: Forty diabetic patients (17 women, 23 men) and 40 healthy subjects (19 women, 21 men) were prospectively recruited. The mean CH was 9.3 mm Hg ± 1.4 (SD) and 10.7 ± 1.6 mm Hg and the mean CRF was 9.6 ± 1.6 mm Hg and 10.9 ± 1.7 mm Hg in the control group and diabetic group, respectively (both P < .0001). Diabetic corneas were significantly thicker (P = .019); the mean CCT was 530.3 ± 35.9 μm in the control group and 548.7 ± 33.0 μm in the diabetic group. The CH and CRF remained significantly different in multivariate analysis that included CCT. There was no statistically significant difference between the 2 groups in IOPcc, IOPg, or IOP GAT measurements. CONCLUSIONS: Diabetes mellitus affected biomechanical parameters of the human corneas, including increased CH, CRF, and CCT. Whether this observation has implications in the clinical management and understanding of corneal ectasia and glaucoma requires further study.

Topical Tacrolimus 0.03% Ointment for Intractable Allergic Conjunctivitis: An Open-Label Pilot Study

Purpose: To evaluate the feasibility of tacrolimus 0.03% dermatological ointment (Protopic) in the treatment of intractable allergic conjunctivitis. Methods: Twenty patients (mean age 10.8 years, range 6–26) with intractable allergic conjunctivitis were enrolled in an open-label study. Tacrolimus 0.03% ointment was applied into the conjunctival sac of both eyes twice daily for 8 weeks, followed by a 2-week washout period. Other ocular medications were discontinued. Conjunctivitis severity was recorded with a composite subjective/objective score (chemosis, tarsal papillary size, corneal staining, tearing, itching, and photophobia) at baseline, week 8, and after washout. Tacrolimus blood levels were measured at 2 weeks. Results: Statistically significant improvement in all categories of the conjunctivitis score was observed between baseline and the week 8 examination (p < 0.001). Adverse events were limited to local burning in one patient who discontinued treatment. Blood tacrolimus levels were mostly undetectable. Conclusions: Application of tacrolimus 0.03% dermatological ointment into the conjunctival sac appears to be effective, well tolerated, and safe in the treatment of allergic conjunctivitis refractory to traditional treatment.

Brief posturographic test as an indicator of fatigue

Abstractu2003 The purpose of the present paper was to analyze the efficiency of an abbreviated, albeit objective posturographic test as an indicator of fatigue. Posturography was measured in 10 healthy adults (age 18–33u2003years, male/female 7/3). Baseline posturographic measurements were taken for each subject. Later, a shorter (3‐min) posturographic test was administered 12 times during 25u2003h of sleep deprivation. This was correlated with subjective assessment of fatigue using a questionnaire and cognitive performance assessed with a reaction time test (Psychomotor Vigilance Test). Although showing significant individual differences, the score of the abbreviated posturographic examination, normalized to each subject’s baseline performance (‘fatigue index’) had a pronounced circadian pattern with a peak of instability in the early morning hours. Fatigue index was highly correlated with the cognitive test (ru2003=u20030.80–0.90). A substantial, albeit weaker correlation was found between the fatigue index and the subjective fatigue scores (ru2003=u20030.59–0.75). Fourier spectral analysis showed that low median sway (0.10–0.50u2003Hz), considered to be an expression of vestibular control, was most affected by fatigue. The study demonstrates that cognitive deterioration caused by fatigue can be objectively predicted by an abbreviated postural test of ≤3u2003min. This test is promising to be valid, reliable, and practicable, while being significantly correlated with physiological markers and validated cognitive measures of fatigue obtained by substantially more time‐consuming and less convenient methods.

Light intensity modulates corneal power and refraction in the chick eye exposed to continuous light

Continuous exposure of chicks to light was shown to result in severe hyperopia, accompanied by anterior segment changes, such as severe corneal flattening. Since rearing chicks in complete darkness results only in mild hyperopia and minor changes in corneal curvature, we hypothesized that light intensity may play a role in the development of refractive changes under continuous light illumination. To test this hypothesis, we examined the effects of rearing chicks under various continuous light intensities. More specifically, we investigated the refractive parameters of the chicks eyes, and avoided light cycling effects on ocular development. To this end, thirty-eight chicks were reared under 24-h incandescent illumination, at three different light intensities: 10,000 lux (n=13), 500 lux (n=12), and 50 lux (n=13). Their eyes underwent repeated retinoscopy, keratometry, and ultrasound biometry, as well as caliper measurements of enucleated eyes. Both refraction and corneal refractive power were found to be correlated with light intensity. On day 90 after hatching, exposure to light intensities of 10,000, 500, and 50 lux resulted in hyperopia of +11.97+/-3.7 (mean+/-SD) +7.9+/-4.08 and +0.63+/-3.61 diopters (D), respectively. Under those intensities, corneal refractive power was 46.10+/-3.62, 49.72+/-4.16, and 56.88+/-4.92D, respectively. Axial length did not differ significantly among the groups. The vitreous chamber was significantly deeper in the high than in the low-intensity groups. Thus, during the early life of chicks exposed to continuous lighting, light intensity affects the vitreous chamber depth as well as the anterior segment parameters, most notably the cornea. The higher the intensity, the more severe was the corneal flattening observed and the hyperopia that developed, whereas continuous illumination at low intensities resulted in emmetropia. Thus, light intensity is an important factor that should be taken into account when studying refractive development.

Drug Modification of Angiogenesis in a Rat Cornea Model

PURPOSEnTo evaluate the influence of some widely used antiglaucoma agents on angiogenesis in a novel rat cornea model.nnnMETHODSnAngiogenesis was induced in 32 rats by slow-release polymer pellets containing basic fibroblast growth factor (bFGF) placed in a corneal micropocket. Angiogenesis was later measured and compared in groups of rats given one of four antiglaucoma drug therapies and one control group. The drugs were commercially available preparations of prostaglandins, beta-blockers, alpha-2 agonists, and carbonic anhydrase inhibitors given for 7 days in a manner similar to that used in humans. Growth was measured by calculating the maximum linear vessel growth divided by pellet-limbus distance.nnnRESULTSnBiomicroscopic observation disclosed that all tested animals showed an induction of neovascular reactions in their corneal stroma. The growth index results for the control, latanoprost, dorzolamide, brimonidine, and timolol malate groups were 1.65 +/- 0.16, 1.98 +/- 0.18, 1.85 +/- 0.19, 2.03 +/- 0.38, and 1.65 +/- 0.14, respectively, confirming the hypothesis that topically delivered antiglaucoma drugs modify the normal angiogenic response. Of them, the prostaglandins showed the most prominent angiogenic stimulatory effect (P = 0.03).nnnCONCLUSIONSnThis modified micropocket assay of corneal angiogenesis in rats demonstrated the stimulatory effect of several widely used topically delivered antiglaucoma medications on the angiogenic process. The results indicate that the selection of drugs for treating different ophthalmic diseases should take into account their influence on angiogenic processes.

Riboflavin/UVA photochemical therapy for severe infectious keratitis

Purpose To describe the antibacterial activity of treatment with riboflavin and ultraviolet A light (UVA) in cases of severe infectious keratitis. Methods A retrospective analysis was performed of an interventional case series in which 6 eyes of 6 patients with severe infectious keratitis, all of whom were refractive to multidrug conventional therapy, were treated with riboflavin/UVA. The procedure was conducted according to the standardized protocol of corneal collagen crosslinking (CXL) for keratoconus. Best spectacle-corrected visual acuity and clinical outcomes were evaluated before and during the follow-up period. Results Five of the 6 patients showed rapid reduction in symptoms and decreased infiltrate size after riboflavin/UVA photochemical therapy. Signs of infection and inflammation mostly resolved within 1 to 2 weeks after the treatment. Despite this therapy, one patient continued to deteriorate, and penetrating keratoplasty was performed. Conclusions The adjunctive use of riboflavin/UVA photochemical therapy has a positive effect on refractory infectious keratitis. The treatment seems to be safe and effective and should be considered as part of the first-line therapy in severe cases of infectious keratitis.

Correlation between reading skills and different measurements of convergence amplitude

Purpose. To find correlations between convergence amplitude and reading ability, as assessed in various methods. Methods. Convergence of 66 children aged 8-10 years was evaluated using 1) Non-accommodative target at near and distance; 2) A near computerized stereogram; and 3) Measurement of near point of convergence (NPC). Reading ability was examined by: 1) a reading comprehension test and 2) the Developmental Eye Movement Test (DEM), which evaluates saccadic speed and accuracy. Results. Convergence amplitudes on a distant target and on a near stereogram were correlated with the DEM score (P = 0.005/0.02, r = –0.38/–0.32 and P < 0.001/0.002, r = –0.53/–0.53 for break/recovery respectively), while NPC and convergence on a near non-accommodative target did not. Reading comprehension test score was not correlated with any of the convergence measurements. Conclusion. Convergence amplitude measured while accommodation is controlled was correlated with the DEM score, which evaluates saccadic speed and accuracy. Further study to evaluate whether improvement in vergence control improves DEM scores is needed.

Trabeculectomy and phaco-trabeculectomy with and without peripheral iridectomy

Purpose To compare the 1-year outcome of trabeculectomy and combined phaco-trabeculectomy that were performed with or without a peripheral iridectomy (PI). Methods In a large tertiary glaucoma clinic, with a single surgeon performing all surgeries, 47 patients scheduled to undergo either a primary trabeculectomy or phaco-trabeculectomy were prospectively randomized to surgery with or without peripheral iridectomy. Other than the inclusion (PI group) or omission (no PI group) of a PI, surgical technique and postoperative care were identical for the two groups. The two groups were compared for intraocular pressure (IOP), success rates, visual acuity (VA), and complication rates. Complete and qualified success rates were defined as IOP 18 mmHg or less with or without medications, respectively. Results The 1-year complete and qualified success rates were comparable for both groups. Complete success was observed in 70% of cases, and qualified success in more than 90%. One patient (4.3%) from the no-PI group developed an iris incarceration into the internal sclerectomy site on postoperative day 1, requiring surgical intervention. No other significant complications (blebitis, endophthalmitis, or choroidal hemorrhage) were encountered in any of the study patients. Conclusions This randomized prospective small scale study explored the possibility of sparing the need to perform a routine PI in trabeculectomy and phaco-trabeculectomy. These preliminary results suggest that the outcomes in the two groups are comparable, paving the way to a larger scale study evaluating the need for PI in modern trabeculectomy surgery.

Spontaneous resolution of Descemet membrane detachment following big-bubble deep anterior lamellar keratoplasty.

Purpose To report 2 cases of delayed spontaneous Descemet membrane (DM) reattachment following big-bubble deep anterior lamellar keratoplasty (DALK). Methods A 21-year-old man with keratoconus and a 36-year-old woman with corneal macular dystrophy underwent big-bubble DALK. No injury to DM was noted intraoperatively or postoperatively. Postoperatively, the patients developed central DM detachment with double anterior chamber formation. A nonsurgical conservative approach (waiting technique) was adopted. Results Three weeks postoperatively, the double anterior chamber resolved spontaneously with complete DM reattachment and a clear donor cornea. Conclusions DM detachment and double anterior chamber following big-bubble DALK may resolve spontaneously.