Pituitary macroadenoma: a case report and review.

Pituitary adenomas are the most common tumours of the sellar region. They generally have a slow but severe impact on vision due to compression of the optic nerves, optic chiasm and cavernous sinus. This case report reviews the clinical presentation, management and treatment of the major classifications of pituitary adenoma. As Australian optometrists perform over 300,000 visual field assessments per year, it is vital they are aware of this important cause of visual field loss.

Retinitis pigmentosa: visual function and multidisciplinary management.

Retinitis pigmentosa (RP) is a leading cause of blindness and visual disability in younger people. Optometrists have a major role in detecting RP and in reducing the visual disability associated with RP. This review summarises the literature relating to visual function in people with RP, with particular attention given to night-blindness, visual acuity decrease and visual field contraction. The range of low vision aids available for people with RP is reviewed and suggestions given on aids that have been found to be most successful. Most importantly, this review overviews the range of services available to people with RP and emphasises how optometrists need to work with a network of professionals to ensure the best possible visual outcomes for people with RP. Particular mention is made of current findings relating to orientation and mobility training, driving, sensory substitution and adaptive technology. The modern optometrist needs to be aware of the multiple needs of people with RP and have the ability to link them with the professionals best able to help them.

The Proview Eye Pressure Monitor: influence of clinical factors on accuracy and agreement with the Goldmann tonometer.

PURPOSE: To investigate (i) the effect of probe position on the lid when using the Proview Eye Pressure Monitor (Proview) and (ii) the accuracy of the Proview and its agreement with the Goldmann applanation tonometer (GAT) in a normal population. METHODS: Intraocular pressure (IOP) measurements were performed on 107 control subjects (mean 25 years) using the Proview and the GAT. The Proview probe was applied to two locations on the eyelid (superior nasal and superior temporal). The IOPs measured with both instruments were compared. RESULTS: A total of 4.6% of young normal eyes could not perceive the phosphene. The mean Proview reading using the recommended nasal lid position was significantly higher (+2.5 mmHg) than that measured using the GAT. The position of the probe application was significant, with temporal lid application giving statistically significantly higher IOP readings than the recommended nasal lid application. The repeatability of Proview measurements was lower than the GAT (coefficients of repeatability of GAT and Proview nasal were 0.96 and 4.21 mmHg respectively). The limit of agreement between the GAT and the Proview nasal was low at +/-7.95 mmHg. CONCLUSION: This study shows that the position of probe application can influence the measurements taken using the Proview. Application of the probe to the nasal superior lid (as recommended) gives the more repeatable and accurate results. Overall however the data indicate that the Proview is neither sufficiently accurate nor repeatable to be used in the detection and management of glaucoma. More work is needed in developing this interesting product.

Effects of hyperglycaemia on ocular development in rabbit: refraction and biometric changes.

AIM: To determine the effect of acute and chronic hyperglycaemia on the refraction and development of the rabbit eye. METHODS: Ocular dimensions of five alloxan-induced hyperglycaemic and six control rabbits were measured over 9 weeks using A scan biometry. Refraction was measured using retinoscopy. The animals were 10 weeks of age at the start of the experiment. RESULTS: The acute onset of hyperglycaemia was associated with a fast and stable 2 D hyperopic shift in refraction. Lens thickness increased during the first 2 weeks of hyperglycaemia, returned to near normal thickness after 3-5 weeks of hyperglycaemia and then decreased in thickness in the last 4 weeks of the study. The hyperopic refraction remained unchanged during changes in lens thickness. Nine weeks of hyperglycaemia was associated with a 25% reduction in the growth of both the globe and the lens and a 17% decrease in body mass compared with the controls. CONCLUSION: The hyperopic refraction change of acute hyperglycaemia is likely to be because of a change in the refractive index of the cortical fibres of the lens and is the probable source of the fluctuating refraction seen in diabetic patients. Chronic hyperglycaemia reduced the axial development of the eye and is the probable source of the chronic hyperopic refraction seen in children with Type I diabetes.

Optometry and WebCT: a student survey of the value of web-based learning environments in optometric education.

PURPOSE: Improvements in information and communication technology and the need for off-campus delivery have led to the increased use of web-based learning tools in optometry schools around the world. This study compared student-reported preferences for traditional lecture-based learning with their preferences when using a web-based learning tool. METHODS: One hundred and thirteen second and third year students from the School of Optometry and Vision Science at the University of New South Wales were surveyed. All students had worked with WebCT for at least two years. Students were asked to rank a range of learning tools in perceived usefulness and also to state how often they used the particular learning tools. RESULTS: The students rated notes (lecture or WebCT delivered) and clinical laboratory sessions as their most useful learning tools. The use of specific learning tools was more diverse, with students reporting that they often used notes (lecture or WebCT delivered), the WebCT calendar tool and the WebCT discussion tool. This result highlights the valuable contribution of the communication aspect of WebCT to fostering learning communities. The least used learning tools were textbooks, websites mentioned in lectures and library print resources. Interestingly, the purchase of textbooks was high with 77 per cent of students on average reporting they had bought the recommended textbooks. CONCLUSION: Notes were the preferred learning tool of the optometry students at UNSW, suggesting that passive learning of content was the preferred learning style. It is hoped that the introduction of web-based learning environments may allow students and staff to reflect on their preferred teaching and learning styles. Web-based learning tools, such as WebCT, provide a powerful method to facilitate independent deeper learning in students with active learning styles. The current encouragement of student-based active learning methods should see increased use of independent learning platforms, such as WebCT, in optometry schools.

An application of threshold-versus-intensity functions in automated static perimetry.

Increment thresholds were measured over a range of adapting illuminances using a modified automated static perimeter. The data were fitted to a threshold versus intensity model (logT - logT(0) + log((A + A(0))/A(0))n) and the values logT(0) and logA(0) estimated. The effect of eccentricity and age on logT(0) and logA(0) was examined in normal subjects. A small group of patients with ocular disease were then assessed. Macular degeneration appeared to act as disease processes acting near the photoreceptor (d1 model). Glaucoma seemed to act near the site of retinal gain (d3 model). This analysis method may be of value in developing light adaptation strategies in people with ocular disease.

Quantification of dark adaptation dynamics in retinitis pigmentosa using non-linear regression analysis.

PURPOSE: Non-linear regression analysis was used to determine dark adaptation indices in people with retinitis pigmentosa and in control subjects. METHODS: Dark adaptation data were collected for 13 people with retinitis pigmentosa and 21 controls using the Goldmann-Weekers Dark Adaptometer. Data were analysed using an exponential non-linear regression model and dark adaptation indices derived. The results were compared to age-related values. RESULTS: The mean cone threshold of the group with RP (4.73 +/- 0.19 log units) was significantly greater than that found in the control group (3.69 +/- 0.12 log units). The rate of cone dark adaptation in the RP group was not significantly different from that of the control group. The a break in the RP group (6.46 +/- 0.70 minutes) was delayed when compared to the control group (4.29 +/- 0.21 minutes) and the rate of rod dark adaptation in the RP group was slower (10 +/- 2 per cent per minute) than that of the control group (15 +/- 1 per cent per minute). CONCLUSIONS: This study has shown that a relatively simple data analysis can provide a more quantitative and intuitive description of dark adaptation rates in people with retinal disease. This technique will enable more effective use of dark adaptometry as a supplement to objective electrophysiology, when monitoring people with retinitis pigmentosa.

Conversion factor for comparison of data from Humphrey and Medmont automated perimeters.

Background: Clinical experience has shown that the sensitivity indices reported by the Humphrey Field Analyser (HFA) are generally higher than those given by the Medmont Automated Perimeter (M600). It is the purpose of this paper to determine a conversion factor for the two perimeters and to confirm this prediction using clinical data. Theory predicted that HFA(sensitivity) - 5 dB = M600(sensitivity). Methods: Sensitivity versus eccentricity profiles were measured over the central visual field on 10 young subjects using both perimeters. Results: Both the HFA and the M600 operate within the realms of the Weber law and measure similar Weber fractions. The sensitivity profiles had similar slopes (about -0.2 dB/degree) and were separated by about six decibels with the HFA reporting higher sensitivity values. This result confirmed the theoretical prediction. Conclusion: The difference in threshold sensitivities between the two perimeters is a result of differences in scaling factors and instrument luminances. A suggested clinical conversion factor is to subtract 5 dB from the HFA data to approximate those of the M600.