A modified model of glaucoma filtering surgery in Sprague-Dawley rats

Animal models are useful in glaucoma research to study tissue response to wound healing. Smaller animals such as rats offer additional advantages in terms of availability of detection antibodies and microarrays with cheaper maintenance costs. In this study, we describe a glaucoma filtering surgery (GFS) model in adult Sprague–Dawley rats by performing a sclerostomy using a 26?G needle and additionally placing a silicone tube (27 G) connecting the anterior chamber to the subconjunctival space to maintain a patent fistula for the flow of aqueous humor, thus providing a more definitive bleb. This technique will be useful in identifying and modifying newer targets in the wound healing process in order to improve surgical outcomes following GFS

Reproducibility of retinal nerve fiber layer measurements across the glaucoma spectrum using optical coherence tomography.

Purpose: The purpose was to determine intra-session and inter-session reproducibility of retinal nerve fiber layer (RNFL) thickness measurements with the spectral-domain Cirrus optical coherence tomography (OCT)® (SD-OCT) in normal and glaucomatous eyes, including a subset of advanced glaucoma. Materials and Methods: RNFL measurements of 40 eyes of 40 normal subjects and 40 eyes of 40 glaucomatous patients including 14 with advanced glaucoma were obtained on the Cirrus OCT® (Carl Zeiss Meditec, Dublin, CA, USA) five times on 1-day (intra-session) and on five separate days (inter-session). Intraclass correlation coefficient (ICC), coefficient of variation (COV), and test-retest variability (TRT) values were calculated for mean and quadrant RNFL in each group separately. Reproducibility values were correlated with age and stage of glaucoma. Results: For intra-session reproducibility, the ICC, COV, and TRT values for mean RNFL thickness in normal eyes were 0.993, 1.96%, and 4.02 μm, respectively, 0.996, 2.39%, and 3.84 μm in glaucomatous eyes, and 0.996, 2.41%, and 3.70 μm in advanced glaucoma. The corresponding inter-session values in normal eyes were 0.992, 2.16%, and 4.09 μm, 0.995, 2.62%, and 3.98 μm in glaucoma and 0.990, 2.70%, and 4.16 μm in advanced glaucoma. The mean RNFL thickness measurements were the most reproducible while the temporal quadrant had the lowest reproducibility values in all groups. There was no correlation between reproducibility and age or mean deviation on visual fields. Conclusions: Peripapillary RNFL thickness measurements using Cirrus OCT® demonstrated excellent reproducibility in normal and glaucomatous eyes, including eyes with advanced glaucoma. Mean RNFL thickness measurements appear to be the most reproducible and probably represent the best parameter to use for longitudinal follow-up.

Evaluation of the anterior chamber angle in Asian Indian eyes by ultrasound biomicroscopy and gonioscopy.

PURPOSE: To compare the ultrasound biomicroscopic measurement of the anterior chamber angle in Asian Indian eyes, with the angle width estimated by gonioscopy. MATERIALS AND METHODS: Participants: Patients with open and closed angles attending a glaucoma clinic were recruited for the study. OBSERVATION PROCEDURES: Temporal quadrants of the angles of patients were categorized by gonioscopy as Grade 0 to Grade 4, using Shaffer's classification. These angles were quantified by ultrasound biomicroscopy (UBM) using the following biometric characteristics: Angle opening distance at 250 micro (AOD 250) and 500 micro (AOD 500) from the scleral spur and trabecular meshwork-ciliary process distance (TCPD). The angles were further segregated as "narrow angles" (Schaffer's Grade 2 or less) and "open angles" (Schaffer's Grade 3 and 4). MAIN OUTCOME MEASURES: The UBM measurements were computed in each case and analyzed in relation to the gonioscopic angle evaluation. RESULTS: One hundred and sixty three eyes of 163 patients were analyzed. One hundred and six eyes had "narrow angles" and 57 eyes had "open angles" on gonioscopy. There was a significant difference among the mean UBM measurements of each angle grade estimated by gonioscopy (P < 0.001). The Pearson correlation coefficient between all UBM parameters and gonioscopy grades was significant at the 0.01 level. The mean AOD 250, AOD 500 and TCPD in narrow angles were 58+/-49 micro, 102+/-84 micro and 653+/-124 respectively, while it was 176+/-47 micro, 291+/-62 micro and 883+/-94 micro in eyes with open angles (P < 0.001) respectively. CONCLUSIONS: The angle width estimated by gonioscopy correlated significantly with the angle dimensions measured by UBM. Gonioscopy, though a subjective test, is a reliable method for estimation of the angle width.