Clinical measurement and categorization of optic disc in glaucoma patients.

Background: Assessment of optic disc size is an important component of optic nerve head examination. Agreement between different methods of disc size measurements is not very good. Purpose: To assess the agreement between the disc size assessed by Heidelberg retina tomograph (HRT) and stereobiomicroscopy with a 90 diopter (D) lens. To report the clinical (measured by biomicroscopy) disc diameters of small, average and large optic discs categorized by HRT disc areas. Setting and Design: Observational study of subjects examined in the glaucoma clinic of a tertiary eye institute. Materials and Methods: Seventy-five eyes of 75 glaucoma subjects were studied. Disc diameter was measured using stereobiomicroscopy and HRT. The agreement between the two sets of measurements was assessed by intraclass correlation coefficient (ICC). Discs were classified into small (<1.6 mm2), average (1.6-2.6 mm2) and large (>2.6 mm2) depending on cutoffs provided by the manufacturers of HRT. The means (95% CI) of the corresponding vertical disc diameter in these groups were assessed. Statistical Analysis: ICC, Bland and Altman plots. Results: ICC for measurements of clinical and HRT horizontal disc diameter was 0.518 and for vertical disc diameter measurement was 0.487. The mean difference between the clinical and HRT measurements as analyzed by the Bland and Altman plot was 0.17 (95% CI, 0.13- 0.47) for horizontal and 0.22 (95% CI, 0.11- 0.54) for vertical disc diameter. Of the 75 eyes, 3 eyes had small discs, 54 average and 18 large discs. The mean clinical vertical disc diameter for small discs was 1.55 mm (95% CI, 1.2-1.7), for average discs was 1.91 mm (95% CI, 1.87-1.96) and for large discs was 2.15 mm (95% CI, 2.03–2.27). Conclusion: The agreement between clinical and HRT disc diameter measurements is moderate. Disc diameter measurement on stereobiomicroscopy can be used to categorize discs into small, average and large discs.

Planimetric optic disc parameters in normal eyes: a population-based study in South India.

PURPOSE: To study the optic disc parameters of normal eyes in a population-based south Indian study. METHODS: One hundred and fifty three subjects from a population-based sample of 1060 included in the Andhra Pradesh Eye Disease Survey (APEDS) were enrolled in the optic disc study. The male-female ratio, the refractive error and distribution of other ocular parameters in the disc study subjects and the APEDS were not significantly different. Magnification corrected morphometry of optic disc photographs obtained by Zeiss telocentric fundus camera was carried out in one randomly chosen eye of each of these 143 subjects. RESULTS: The mean optic disc parameters with the 95% confidence intervals for the distribution were: disc area 3.37 mm2 (2.04 - 4.7), vertical disc diameter 2.12 mm (1.67 - 2.57), vertical cup to disc ratio 0.37 (0.19 -0.55) and neuroretinal rim area 2.8 mm2 (1.76 - 3.84). The disc area, the vertical cup to disc ratio and the rim area showed a normal distribution. The cup to disc ratio correlated with the vertical disc diameter but the association was not strong. CONCLUSION: The disc area, the vertical cup to disc ratio and the neuroretinal rim area are normally distributed in the South Indian population. The normal optic disc parameters would form a basis for future comparisons in different forms of glaucoma.

Optic disc size in ocular hypertension.

PURPOSE: To study the optic disc size in eyes with ocular hypertension (OHT) in comparison to primary open-angle glaucoma (POAG) and normals. METHODS: Optic disc photographs obtained with the Nidek 3dx NM camera were digitized (Nikon coolscan) and disc area calculated using Littmann correction in a randomly chosen eye of 28 OHT, 42 POAG and 30 normal subjects. OHT was defined as increased intraocular pressure with no disc or field changes suggestive of glaucoma with open angles. RESULTS: The optic disc area in OHT was 9.47 +/- 1.09 mm2; 12.27 +/- 2.87 mm2 in POAG; and 12.11 +/- 2.83 mm2 in normal individuals. CONCLUSION: Using magnification corrected morphometry and the criteria for OHT diagnosis, the optic disc area in OHT was significantly smaller (p < 0.0001) in POAG and normals.

Ocular toxicity of tamoxifen.

Tamoxifen is an antioestrogen drug used widely in the management of oestrogen-dependent metastatic breast carcinoma. A number of ocular complications have been described secondary to tamoxifen therapy. We report two patients, one of whom had superior ophthalmic vein thrombosis and the other who had painful proptosis and acute angle-closure glaucoma with choroidal detachment secondary to tamoxifen therapy, both of which have not been reported earlier. In both patients the signs and symptoms resolved rapidly after the discontinuation of tamoxifen therapy. Awareness of the ocular toxicity of tamoxifen is essential as prompt withdrawal can result in resolution of most of the complications.

Post-penetrating keratoplasty glaucoma.

To study the risk factors in the development of glaucoma following penetrating keratoplasty, we retrospectively analysed 190 eyes of 185 consecutive patients who had undergone surgery during 1990. The donor button was larger by 0.2 mm and 0.5 mm in phakia and aphakia/pseudophakia patients, respectively. Over a mean follow-up period of 14.5 months, 52 of the 190 eyes (27.4%) either developed glaucoma de novo or had worsening of preexisting glaucoma. Of these 52 eyes, 38 were managed medically and 14 required surgery. From our study, aphakia (37%), pseudophakia (24%), preexisting glaucoma (81.8%), and regrafting (43.18%) were found to be the significant risk factors in the development of glaucoma following penetrating keratoplasty.