Detection of retinal lesions after telemedicine transmission of digital images.

PURPOSE/BACKGROUND: To assess whether loss of image resolution or colour and subsequent telemedicine transmission of digital images affects the accuracy of retinal lesion detection by ophthalmologists when compared with the original transparencies. METHODS: Fifteen ophthalmologists of different experience independently scored 11 retinal images for pathological signs. The images were presented as either transparencies or colour and monochrome digital images, which had been transmitted via telephone lines to a geographically remote location. One patient's eye was also imaged using scanning laser ophthalmosocopy (SLO) which produced a dynamic black and white digital image. ANOVA analysis was performed. RESULTS: Total scores were higher for transparencies than colour (p = 0.0003) or black and white digital images (p = 0.00006). Expert observers (n = 5) considered separately showed no significant difference of accuracy between transparencies and either colour digital (p = 0.09) or monochrome digital images (p = 0.11). Experts were better than trainees at detecting pathology from less familiar images: total score (p = 0.02), colour digital (p = 0.03), monochrome digital (p = 0.02) and SLO images (p = 0.004). CONCLUSION: Experienced observers can identify sight-threatening retinal pathology from poorer-resolution digital images that have been transmitted by telemedicine. They can also adapt to viewing less familiar images such as black and white digital or SLO images.

A comparative study of the duration and efficacy of tetracaine 1% and bupivacaine 0.75% in controlling pain following photorefractive keratectomy (PRK).

OBJECTIVE: To evaluate if topical bupivacaine 0.75% provides better pain control after excimer laser over topical tetracaine 1% without affecting corneal wound healing, refractive outcome of visual function. DESIGN: A prospective, double-masked trial was conducted in which 38 patients were randomized to receive either tetracaine or bupivacaine every 30 minutes for 24 hours post-operatively. Pain was recorded over a four day period using a Visual Analogue Pain Scale. The rate of epithelial healing was assessed during digitized retro-illumination photography. Visual performance was recorded using best corrected Snellen acuity, objective measurements of haze, halo and glare over a six month period. RESULTS: Tetracaine afforded better pain control (p = 0.05). Full epithelial closure occurred in all patients within 72 hours and no statistically significant difference was recorded in any of the parameters measured. CONCLUSIONS: Contrary to our expectation, the longer acting anaesthetic, bupivacaine, was inferior to tetracaine. Limited and supervised use of topical anaesthetics is recommended in controlling pain following photorefractive keratectomy.

Effect of ablation profile on wound healing and visual performance 1 year after excimer laser photorefractive keratectomy.

BACKGROUND: Early photorefractive keratectomy ablations were of limited diameter and depth to maintain the integrity of the globe and to minimise postoperative haze. This study evaluated the effects of deeper, larger diameter wounds on refractive stability and corneal haze, and investigated the effects of ablation profile on wound healing and visual performance. METHODS: One hundred patients undergoing -3.00D and -6.00D corrections were randomised to receive 5 mm, 6 mm, or multizone treatments. The multizone treatment was 6 mm in diameter, but only the depth of the 5 mm treatment. Outcome was measured by Snellen visual acuity, residual refractive error, objective techniques for haze and halos, pupil diameter, subjective night vision, and requirement for retreatment. RESULTS: Overall, the results of 6 mm treatments were superior to those of 5 mm and multizone treatments: they had a smaller hyperopic shift (p < 0.01), a more predictable (p < 0.001) and stable refractive outcome, less haze (p < 0.05), smaller halos (p < 0.05), fewer subjective night vision problems, and fewer patients required retreatment. CONCLUSIONS: Analysis of these data and a literature review of corneal wound healing demonstrated that the improved outcome associated with the 6 mm beam did not relate to the depth of ablation. The factor with greatest apparent influence on the development of haze and regression was the slope of the wound surface over the entire area of the ablation. Tapering the wound edge provided no additional benefit, and contributed to night vision problems. It is, therefore, recommended that small diameter or multizone treatments should not be used in low and moderate myopia.

Effects of ablation diameter, depth, and edge contour on the outcome of photorefractive keratectomy.

PURPOSE: To investigate the effects of the ablation diameter, depth, and edge contour on the outcome of excimer laser photorefractive keratectomy (PRK). METHODS: A prospective study was conducted in which 60 patients (60 eyes) were randomly allocated to 5.00-mm, 6.00-mm, or 5.00 to 6.00-mm multizone treatment groups. All eyes underwent a -6.00 diopter (D) correction using a Summit Omnimed excimer laser. RESULTS: In eyes treated with 6.00-mm diameter zones, the initial hyperopic shift was reduced, with significant differences at 1 and 4 weeks (p < 0.01). At 6 and 12 months, the refractive changes were closer to the intended correction with 6.00-mm diameters. The predictability of PRK was improved with 6.00-mm zones, with a significant reduction in variance of the refractive changes, at all stages postoperatively (p < 0.05 to p < 0.001). Objective measurements of haze were significantly less at 1, 3, and 6 months with 6.00-mm ablations (p < 0.05). There were no differences between the 5.00-mm and the 5.00- to 6.00-mm multizone groups. Computerized measurements of "night" halo were significantly smaller in the 6.00-mm treatment group at 1 week and 1 month (p < 0.05). At 12 months, two patients treated with 5.00-mm zones and three with the 5.00- to 6.00-mm multizone complained of severe night vision disturbances. No 6.00-mm eyes were similarly affected. CONCLUSIONS: Treatment with a 6.00-mm spherical ablation diameter produced less initial overcorrection, improved predictability, and was associated with a reduction in postoperative halos and night vision disturbances. Creating a superficial blend zone with a 5.00- to 6.00-mm multizone treatment had no beneficial effect on the outcome.

Retinal laser lenses: magnification, spot size, and field of view.

Proper use of ophthalmoscopic contact lenses for retinal photocoagulation requires knowledge of their comparative magnification, spot size, and field of view. We determined these parameters for four commonly used lenses, using data measured from optical components of the lenses and a commonly used photo-coagulator slit-lamp and spot size changer. A Krieger lens has 8% more working field of view and 29% less magnification than a Goldmann lens. A Panfundoscope lens has 84% more working field of view and 24% less magnification than a Goldmann lens. A Mainster lens has 58% more working field of view and 3% more magnification than a Goldmann lens. For Goldmann, Krieger, Panfundoscope, and Mainster lenses, respectively, retinal spot size is 8%, 53%, 41%, and 5% greater than photo-coagulator spot size settings. The field of view of each lens is increased in myopic and decreased in hyperopic patients. Anterior segment irradiance is higher than retinal irradiance for 1000 microns spot size settings with a Panfundoscope or Mainster lens, and this setting should be avoided, especially in patients with hazy ocular media.

A slitlamp comparator system for macular photocoagulation.

A slitlamp comparator device has been developed to project the image of a 35mm angiogram frame into the field of view of a standard slitlamp during macular photocoagulation. The image may be varied in brightness, magnification, and position, and viewed either on a black background or superimposed on a slitlamp fundus image. The comparator is a useful alternative to conventional angiogram projection systems and suggests the utility of more sophisticated "heads-up" display devices.