Glyn Walsh

Clinical comparison of the Keeler Pulsair 2000, American Optical MkII and Goldmann applanation tonometers

The aim of our study was to evaluate the performance of both the Keeler Pulsair 2000 and the American Optical (AO) MkII non-contact tonometers (NCT) and compare these to the reference Goldmann standard using the same group of patients. Forty-five patients (89 eyes) receiving medical treatment for primary open angle glaucoma had their intraocular pressure (IOP) measured with each instrument in a random order using five experienced observers. In the IOP range of the sample (6-27 mmHg) the difference between means for each tonometer was small. The Pulsair 2000 (mean = 19.06 mmHg, SD 6.28) read slightly higher than Goldmann (mean = 18.01 mmHg, SD 4.88), whereas the AO MkII read slightly lower (mean = 16.27 mmHg, SD 5.93). However, all differences were statistically significant (P < 0.001, repeat measures ANOVA). Correlation coefficients for Pulsair 2000 versus Goldmann was r = 0.82 and for AO MkII versus Goldmann was r = 0.85. In addition, the repeatability for each NCT was assessed using 10 consecutive measurements on a further 10 subjects. The Pulsair 2000 showed significantly greater variation of IOP (mean SD 3.43 mmHg) than the AO MkII (mean SD 1.76 mmHg), confirming the need for taking at least four readings per eye with the Pulsair 2000. These variations are greater than that generally observed with Goldmann, and possible explanations why this occurs are discussed. In conclusion, subject to these limitations, both NCTs should be useful for measuring IOP as part of a screening protocol for glaucoma.

Contrast and glare sensitivity in diabetic patients with and without pan-retinal photocoagulation

Patients with diabetes mellitus often have ophthalmic dysfunction, as diabetic eye disease can affect the majority of the ocular structures. The present study investigated contrast sensitivity (experiment 1) and glare sensitivity (experiment 2) using Pelli-Robson and Bailey-Lovie charts in normal and diabetic patients with a range of degrees of ischaemic retinopathy (n = 220). Contrast sensitivity thresholds reduced and glare sensitivity progressively increased throughout the range from normal to advanced stages of diabetic eye disease. However, the reduction in contrast sensitivity between adjacent groups was not significant (P > 0.10). Conversely, glare sensitivity was found to be greater in those diabetic patients who had received laser treatment (P = 0.001). The potential use of both tests is discussed.

Materials and allergens within spectacle frames: a review

The materials that have been reported as causing allergic contact dermatitis within spectacle frames are identified, and their most likely location on the frame is highlighted. The lack of any real control over spectacle frame quality and content is indicated to be a problem, as is the difficulty in determining the true source of many frames. Much of the information must be obtained from anonymous sources in the industry, historical ‘common knowledge’ of indeterminate source or reports of dermatological problems.

Free surface nickel in CE-marked and non-CE-marked spectacle frames

Three hundred and ninety‐five new frames were tested for evidence of nickel release using dimethylglyoxime and ammonia. For areas of CE‐marked frames in direct contact with the skin a considerable improvement was found over the previous such survey by the authors, carried out before the widespread introduction of CE marking. However, free nickel was found in 6.5% of CE‐marked metal frames (excluding titanium and titanium alloy) in such areas and a majority of half joints. Some titanium alloy frames also tested positive for nickel in areas in contact with the skin.

Optical dispensing: the science of vision or blind faith?

The evidence for the basic optometric function of optical dispensing is discussed in terms of the basic principles of scientific debate. The degree of rigour applied to product testing and evaluation of most other medically related areas is lacking in the dispensing of spectacles. There has been much debate on the place of religious faith in our society. Religious belief masquerading as science has come in for particular scrutiny. However, little attention has been paid to the equally contentious issue of non‐religious belief, within scientific disciplines, masquerading as science. It could be argued that optical dispensing is, to a significant degree, such a case.

The leaching of nickel from new and used metal spectacle frames

Fifty “used” and 373 new spectacle frames were tested for evidence of nickel release using dimethylglyoxime and ammonia. Nearly all the “used” frames (96%) tested positive. A lower proportion (24.5%) of new frames showed evidence of nickel leaching. It is suggested that this is evidence of non‐conformance with the current British Standard (British Standard 6625, 1985) although all our suppliers believed that their frames conformed with BS 6625 (1985).

Reliability and validity studies of a new computer-assisted crossed-cylinder aberroscope

Purpose. We assessed the reliability and validity of a new computer-assisted crossed-cylinder aberroscope technique which measures the monochromatic optical aberrations of the human eye. Methods. Intra-image variability, the variability occurring when the same image is repeatedly measured, and inter-image variability, the variability occurring when different images collected from the same eye are measured, were assessed using 10 repeated measures on each of 10 different subjects. We compared the measurements made using the computer-assisted technique with manual measurements made when a human operator performed all the aberroscope grid intersection location tasks. Results. One-way repeated measures analyses of variance (ANOVA) on the inter-image and intra-image variability showed that the mean of the measurements made was statistically independent of the occasion on which a group of subjects was measured, and inter-image variability was larger than intra-image variability. A two-way repeated measures ANOVA comparing computer-assisted results with manual results showed that the means of the measurements made with the two methods are not statistically different from one another. The manual results showed greater variability than computer-assisted measurements. Conclusions. The technique is reliable and valid compared to earlier objective crossed-cylinder aberroscopic techniques.

Effect of the menstrual cycle on corneal curvature

The purpose of this research was to determine if a clinically significant variation in corneal curvature occurs with the menstrual cycle. The EyeSys Corneal Analysis System (CAS) was used to measure corneal curvature of a test group of three normally menstruating female subjects over three cycles and compared with a control group of three males, for three pseudocycles of 28 days. Measurements were taken on days 1, 4, 8, 15 and 22 of each of three menstrual cycles, with four CAS images taken on each day. Four points (along 45, 135, 225 and 315 degrees) were selected for each of rings 1, 3, 6 and 8, and the average curvature for each of these rings was calculated. The results showed that no detectable temporal effect occurred with the menstrual cycle, thus demonstrating that either cyclic variation in corneal topography was too small to be identified by this system or it did not take place.

A simple new method for the construction of a ptosis crutch

A technique by which a ptosis crutch can be fitted in minutes, using readily available and inexpensive materials and tools, is described. No specialist skills are needed and the device can be fitted to existing frames and lenses.

The weight of spectacle frames and the area of their nose pads

The current international standard for spectacle frames recommends that frames weighing up to 25 g should have a minimum nose‐pad contact area of 200 mm2 and that those weighing over 25 g should have a minimum contact area of 250 mm2. It is shown that these recommendations are being almost universally ignored for frames with separate pads on arms. The information on frame materials in manufacturers’ literature is woefully inadequate but, from the information available, there was little difference in weight between stainless steel frames and those from unnamed materials.