Performance of the PT100 noncontact tonometer in healthy eyes

Turki M AlMubradCornea Research Chair, Department of Optometry, College of Applied Medical Sciences, King Saud University, Riyadh, Kingdom of Saudi ArabiaBackground: The purpose of this study was to assess the repeatability and reproducibility of the PT100 noncontact tonometer and to compare its consistency with the Goldmann applanation tonometer (GAT) in measuring intraocular pressure (IOP).Methods: Triplicate IOP measurements were obtained on two separate occasions using the PT100 and GAT from randomly selected eyes in 66 healthy volunteers aged 22 ± 1 years. The repeatability and reproducibility of each techniques was assessed. Agreement between the techniques was statistically quantified using intrasession repeatability for each technique as the basis for comparison.Results: Both techniques returned equal IOP values in the first measurement session (15 ± 3 mmHg). The second session showed a mean difference in average IOP (1 ± 0.71). The 95% limits of agreement between the techniques were –5.2 to 5.5 mmHg and –4.0 to 4.7 mmHg (sessions 1 and 2, respectively). These mean differences were not statistically significant (P > 0.05, paired t-test), with the PT100 underestimating IOP measurement by 1.00 mmHg. The mean intrasession IOP for GAT sessions 1 and 2 was 0 ± 0.90 mmHg and 0.04 ± 1.06 mmHg, respectively, and the corresponding mean IOP measurement difference for the PT100 was –0.06 ± 0.96 and –0.39 ± 0.94 mmHg (sessions 1 and 2, respectively; P > 0.05, paired t-test). Repeatability coefficients for the GAT IOP measurements were 1.8 mmHg and 2.1 mmHg for sessions 1 and 2, while the PT100 repeatability coefficient was 1.9 mmHg and 1.8 mmHg for sessions 1 and 2, respectively. The intrasession repeatability coefficient of both techniques for test–retest differences were within ±5 mmHg.Conclusion: The PT100 noncontact tonometer produced greater repeatability than the GAT in assessment of IOP, whereas GAT resulted in more reproducible results. Both techniques showed a close level of agreement on comparison, with the PT100 underestimating IOP measurement by 1.0 mmHg only, although this was not clinically or statistically significant. Of importance is that the IOP measurements using these techniques could be interchangeable in the IOP range studied here.Keywords: Goldmann applanation tonometer, intraocular pressure, Reichert PT100, noncontact tonometer, repeatability, reproducibilit

Collagen Fibrils and Proteoglycans of Peripheral and Central Stroma of the Keratoconus Cornea - Ultrastructure and 3D Transmission Electron Tomography

Keratoconus (KC) is a progressive corneal disorder in which vision gradually deteriorates as a result of continuous conical protrusion and the consequent altered corneal curvature. While the majority of the literature focus on assessing the center of this diseased cornea, there is growing evidence of peripheral involvement in the disease process. Thus, we investigated the organization of collagen fibrils (CFs) and proteoglycans (PGs) in the periphery and center of KC corneal stroma. Three-dimensional transmission electron tomography on four KC corneas showed the degeneration of microfibrils within the CFs and disturbance in the attachment of the PGs. Within the KC corneas, the mean CF diameter of the central-anterior stroma was significantly (p ˂ 0.001) larger than the peripheral-anterior stroma. The interfibrillar distance of CF was significantly (p ˂ 0.001) smaller in the central stroma than in the peripheral stroma. PGs area and the density in the central KC stroma were larger than those in the peripheral stroma. Results of the current study revealed that in the pre- Descemet\u27s membrane stroma of the periphery, the degenerated CFs and PGs constitute biomechanically weak lamellae which are prone to disorganization and this suggests that the peripheral stroma plays an important role in the pathogenicity of the KC cornea

Repeatability and Diurnal Variation of Tear Ferning Test

This is a non-final version of an article published in final form in: Masmali, A. M., Al-Bahlal, J. M., El-Hiti, G. A., Akhtar, S., Purslow, C., Murphy, P. J., & Almubrad, T. (2015). Repeatability and Diurnal Variation of Tear Ferning Test: Eye & Contact Lens: Science & Clinical Practice, 41(5), 262–267. https://doi.org/10.1097/ICL.0000000000000116Objectives: To investigate tear ferning (TF) test repeatability between sessions by observing changes in the tear fern pattern during the day. Methods: Twenty-three healthy young adults (15 men and 8 women), ranging in age from 20 to 32 years (mean±SD: 22.9±3.3 years) without signs or symptoms of dry eye disease, ocular disease, or contact lens wear were enrolled in the study. Schirmer I, tear break-up time (TBUT) test, and McMonnies questionnaire were used to screen volunteers. Schirmer I and TBUT tests were applied to both eyes in each subject. Four samples of tear fluid were collected from the right eye of each subject using glass capillaries at set intervals during a single day (9 AM, 11 AM, 2 PM, and 4 PM). The TF patterns obtained from samples were classified according to the Masmali TF grading scale to increments of 0.1. Results: The median values obtained from the McMonnies, Schirmer, and TBUT tests were 4.0±2.0, 30.0±7.0 mm (OD), and 16.0±10.0 sec (OD), respectively. There were no statistically significant differences between the TF grades for tear samples collected at different times of the day (Wilks' Lambda, P=0.351). The majority (84.8%) of TF grades was between 0.0 and 1.5; the remaining 15.2% of subjects had TF between grades 1.6 and 1.9. The overall mean grade for the TF was 1.1±0.3. There were small insignificant correlations between TF grades and the McMonnies questionnaire (r=0.1.30) and TBUT (r=0.248) and a negligible correlation with Schirmer test (r=−0.046). Conclusions: The results found no significant differences within the TF for tear samples collected at different times of the day, suggesting that there is little diurnal variation evident.The authors extend their appreciation to the College of Applied Medical Sciences Research Center and the Deanship of Scientific Research at King Saud University for its funding of this research

Nott and MEM dynamic retinoscopy: Can they be used interchangeably?

Introduction: Previous studies suggest that monocular estimate method (MEM) and Nott retinoscopy yield identical results in the assessment of the accommodative lag. However, two recent studies suggested that the accommodative lag measured with MEM retinoscopy is twice that with Nott. This study was designed to re-evaluate the agreement of MEM and Nott retinoscopy techniques. Material and methods: One hundred and thirty (130) subjects aged between 18 and 30 years (22±3 years – mean ±SD), with no history of contact lens wear, ocular and systemic disease or ocular surgery, participated in the study. Nott and MEM Retinoscopy were used to assess the lag of accommodation through the Corrected Ametropia Most Plus (CAMP) subjective refraction at 40 cm. Results: The mean difference between both sessions for Nott retinoscopy was 0.01±0.1 D (mean ±SD). The mean difference between both sessions for MEM retinoscopy was – 0.002±0.11 D (mean ±SD). The mean difference between Nott and MEM dynamic retinoscopy was 0.01±0.13 D (mean ±SD) with 95% limits of agreement ranging between +0.26 and -0.25 D. For both Nott and MEM, there was no significant difference (P>0.05) of the measured lag between the four measurement sessions and no significant difference (P>0.05) was found between both methods. Conclusions: We conclude that in normal healthy subjects with normal accommodative and binocular function, MEM and Nott dynamic retinoscopy techniques may be used, interchangeably, to assess the lag of accommodation at 40 cm

ORGINAL PAPER<br>Nott and MEM dynamic retinoscopy: Can they be used interchangeably?

Introduction: Previous studies suggest that monocular estimate method (MEM) and Nott retinoscopy yield identical results in the assessment of the accommodative lag. However, two recent studies suggested that the accommodative lag measured with MEM retinoscopy is twice that with Nott. This study was designed to re-evaluate the agreement of MEM and Nott retinoscopy techniques. Material and methods: One hundred and thirty (130) subjects aged between 18 and 30 years (22±3 years – mean ±SD), with no history of contact lens wear, ocular and systemic disease or ocular surgery, participated in the study. Nott and MEM Retinoscopy were used to assess the lag of accommodation through the Corrected Ametropia Most Plus (CAMP) subjective refraction at 40 cm. Results: The mean difference between both sessions for Nott retinoscopy was 0.01±0.1 D (mean ±SD). The mean difference between both sessions for MEM retinoscopy was – 0.002±0.11 D (mean ±SD). The mean difference between Nott and MEM dynamic retinoscopy was 0.01±0.13 D (mean ±SD) with 95% limits of agreement ranging between +0.26 and -0.25 D. For both Nott and MEM, there was no significant difference (P>0.05) of the measured lag between the four measurement sessions and no significant difference (P>0.05) was found between both methods. Conclusions: We conclude that in normal healthy subjects with normal accommodative and binocular function, MEM and Nott dynamic retinoscopy techniques may be used, interchangeably, to assess the lag of accommodation at 40 cm