Retinal Oximetry: The Indian Experience in Healthy and Diseased Eyes.

To study the alterations in retinal oxygen saturations in healthy and diseased eyes. Patients presenting to our hospital underwent an additional non-invasive procedure to measure oxygen saturation in their retinal vessels. After dilatation, oximetry was done using the Oxymap T1 retinal oximeter (Oxymap hf, Reykjavik, Iceland). Normal patients and patients with arteriolar and venous occlusions, retinal dystrophies and glaucoma, were evaluated. Arteriolar, venous and arteryvenous saturation difference (AVSD) values were determined for each of the groups. In the normal subjects (n = 98), the average arteriolar saturation was 90.3 ± 6.5, and the venous saturation was 56.9 ± 6.3. The average AVSD was 33.4 ± 5.0. In arterial occlusions (n = 10), we have seen an initial fall in arteriolar (85.8%) and venous (49.7%) saturations in the acute stage in eyes with central retinal artery occlusion with subsequent increase in saturations. In venous occlusions (n = 18), there was an initial increase in all global saturation parameters in the acute stage (arteriolar: 105.8%, venous: 62.7%, AVSD: 43.3%), followed by a gradual decrease in saturations in the chronic stage (arteriolar: 99.8%, venous: 60.1%, AVSD: 39.8%). Eyes with retinitis pigmentosa (n=62) showed higher saturations (104.15%) and higher AVSD (44.15%) compared to macular dystrophies (n = 23) (96.7% and 41.61%) and normal controls (90.6% and 33.3%). Macular dystrophies showed higher global arteriolar values and AVSD but comparable venous values to the control group. In glaucoma (n = 44), we have seen raised arteriolar and AVSD values. Oximetry is sensitive in picking up changes in diseased eyes that are distinct from normal values. In the future, it may prove to be useful in pre-clinical screening studies and in therapeutic decision making.

Comparison of intraocular pressure measurement with Scheimpflug‑based noncontact tonometer with and without hydrogel contact lenses.

Objectives: The objective was to determine the repeatability of intraocular pressure (IOP) measurements made through a soft contact lens (CL) using the Scheimpflug noncontact tonometry in healthy subjects. Methods: This prospective, randomized, single‑center study included one eye of 88 subjects (40 male and 48 female). Only participants without glaucoma or any other ocular pathology were included in this study. Three consecutive IOP measurements by the Scheimpflug noncontact tonometry were performed with and without daily disposable hydrogel CLs (−0.50 DS) (Dailies‑nelfilcon A, 69% water, 8.7 mm base curve, 14 mm diameter, center thickness 0.10 mm) by a single operator. To avoid any bias arising from diurnal variation, all measurements were made at a similar time of day (11 am ± 1 h). The repeatability of IOP measurements using the Scheimpflug noncontact tonometry with and without CLs was evaluated using Pearson’s correlation analysis. Bland–Altman plotting was used to assess the limits of agreement between the measurements with and without CLs. Results: The mean (± standard deviation) IOPs with and without CL were 13.80 ± 2.70 and 13.79 ± 2.54 mm of Hg respectively. The mean difference was 0.01 ± 0.16 (95% confidence interval, +1.97 to − 2.00) mm Hg. Statistical analysis via paired t‑test showed no statistical difference between the two groups with (P = 0.15). A good correlation was found for IOP measurements with and without CL (r = 0.93, P < 0.001). Good test‑retest reliability was found when IOP was measured with and without CL. Conclusion: There was no significant difference between IOP measured with and without CLs by Scheimpflug noncontact tonometry.

Five-year risk of progression of ocular hypertension to primary open angle glaucoma. A population-based study.

PURPOSE: To report the progression of ocular hypertension (OHT) to primary open angle glaucoma (POAG) during a 5-year follow up of a population-based sample. METHODS: Twenty-nine patients diagnosed to have OHT and 110 randomly selected normals from a population-based study in 1995 were invited for ocular examination in 2000. All patients underwent a complete ophthalmic examination; including the daytime diurnal variation of intraocular pressure (IOP) and measurement of central corneal thickness (CCT). The "corrected" IOP was used for analysis. Progression to POAG was based on typical optic disc changes with corresponding field defects on automated perimetry. RESULTS: Twenty-five of the 29 persons with OHT who could be contacted were examined. After correcting for CCT, two persons were reclassified as normal. Four of 23 (17.4%; 95% CI: 1.95-32.75) had progressed to POAG. One person amongst the 110 normals progressed to normal tension glaucoma (NTG). The relative risk of progression amongst OHT was 19.1 (95% CI: 2.2-163.4). All those who progressed had bilateral OHT. The mean and peak IOP in those who progressed was 25.4 mm Hg and 29.3 mm Hg compared to 23.9 mm Hg and 25.7 mm Hg in those who did not. Those who progressed had more than 8 mm Hg diurnal variation. The diurnal variation was less than 6 mm Hg in those who did not progress. No patient developed blindness due to glaucoma. CONCLUSION: The 5-year incidence of POAG amongst OHT in this population was 17.4% (3.5% per year). Bilateral OHT, higher peak IOP and large diurnal variation may be the risk factors for progression.