To examine resource consumption and the direct costs of treating glaucoma at different disease severity levels. Design: Observational, retrospective cohort study based on medical record review. Participants: One hundred fifty-one records of patients with primary open-angle or normal-tension glaucoma, glaucoma suspect, or ocular hypertension (age Ն18 years) were randomly selected from 12 sites in the United States and stratified according to severity based on International Classification of Diseases, Ninth Revision, Clinical Modification codes. Patients had to have been followed up for a minimum of 5 years. Patients with concomitant ocular disease likely to affect glaucoma treatment-related resource consumption were excluded. Methods: Glaucoma severity was assessed and assigned using a 6-stage glaucoma staging system, modified from the Bascom Palmer (Hodapp-Anderson-Parrish) system. Clinical and resource use data were collected from the medical record review. Resource consumption for low-vision care and vision rehabilitation was estimated for patients with end-stage disease based on specialist surveys. For each stage of disease, publicly available economic data were then applied to assign resource valuation and estimate patientlevel direct costs from the payer perspective. Main Outcome Measures: Average annual resource use and estimated total annual direct cost of treatment were calculated at the patient level and stratified by stage of disease. Direct costs by specific resource types, including ophthalmology visits, glaucoma surgeries, medications, visual field examinations, and other glaucoma services, were also assessed. Results: Direct ophthalmology-related resource use, including ophthalmology visits, glaucoma surgeries, and medication use, increased as disease severity worsened. Average direct cost of treatment ranged from $623 per patient per year for glaucoma suspects or patients with early-stage disease to $2511 per patient per year for patients with end-stage disease. Medication costs composed the largest proportion of total direct cost for all stages of disease (range, 24%-61%). Conclusions: The study results suggest that resource use and direct cost of glaucoma management increase with worsening disease severity. Based on these findings, a glaucoma treatment that delays the progression of disease could have the potential to significantly reduce the health economic burden of this chronic disease over many years.

Noise-intensity discrimination was studied as a function of both signal and masker bandwidth. Five bandwidths of noise—ranging from 100 to 10 000 Hz—were employed. Maskers were presented at each of three spectrum levels (5, 25, and 45 dB re 0.0002 μbar). Discrimination thresholds were relatively unaffected by changing bandwidth over a two-decade range when the signal and masker were filtered together, with either continuous or gated presentation of the masker. When the masker bandwidth was greater than that of the signal, the reciprocity between signal power density and signal bandwidth was found to be 5 dB per log unit of bandwidth with continuous maskers and 5–10 dB (depending upon level) with gated maskers. The results were compared with predictions of energy-detector models of noise-intensity discrimination. Modifications of simple energy-detection schemes were discussed. Subject Classification: [43]65.58, [43]65.75, [43]65.50; [43]50.70.

ConclusionOptimal therapy for glaucoma would involve IOP control throughout the 24-h period. However, not all therapies are equally efficacious at all times of the day and night. Understanding of the mechanisms of action of different therapies, along with the knowledge of the circadian changes in aqueous humor dynamics, allows us to predict the therapies that will provide the most consistent IOP reduction. As well, understanding of aqueous humor dynamics may help in the development of future therapies with consistent 24-h IOP control. Bibliography

Intensity discrimination functions were determined for tone bursts at four test frequencies: 250, 1,000, 4,000, and 7,000 Hz. Slopes of best-fitting lines (~l in dB SL vs I in dB SL) indicate a "near-miss" to Weber's law at all four frequencies. The use of information provided by harmonics of the stimulus is discussed; it is concluded that-at least for high-frequency tones-such cues are not the basis for the improved acuity found at higher sensation levels.