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.

Analysis of Spectral Domain - Optical Coherence Tomography and Fundus Autofluorescence in Typical Retinitis Pigmentosa.

Purpose: To study fundus autofluorescence (FAF) and spectral domain-optical coherence tomography (SD-OCT) characteristics in patients with typical retinitis pigmentosa (RP) and correlate them to visual acuity. Design: Retrospective observational case series. Methods: 110 eyes of 56 RP patients were included. FAF and SD-OCT imaging were done for all eyes. Extent of the autofluorescence ring, central foveal thickness, photoreceptor outer-segment length (PROS), foveal outer segment pigment epithelial thickness (FOSPET), and inner segment-outer segment (IS-OS) extent were defined and measured and correlated to logMAR best corrected visual acuity (BCVA) using linear regression. Results: Study included 110 eyes of 56 patients (34 male and 22 female). Mean BCVA was 0.33 logMAR with no difference between genders. The mean age of patients was 15.4 ± 15.1 years. Mean autofluorescence extent was 3590 ± 1994 μm horizontally, and 2880 ± 1836 μm vertically. These values were significantly correlated with preserved IS/OS junction extent (mean values horizontally = 2865 μm and vertically = 2464 μm). Mean central retinal thickness (218.74 μm) and PROS (44.85 μm) were significantly correlated to BCVA with correlation coefficient r = –0.189, P = 0.015; and r = –0.874, P = 0.0001, respectively. FOSPET (mean = 71.15 μm) did not show a significant correlation with BCVA, independent of PROS. Conclusions: Retinal microstructural changes as studied on SD-OCT, especially PROS length can be used as a surrogate marker to monitor degenerative diseases such as RP. Further, studies are required to clearly delineate the microstructuralfunctional relationship in the human retina.

Perioperative optic neuropathy in patients undergoing off‑pump coronary artery bypass graft surgery.

Aims and Objectives: Perioperative optic neuropathy (PON) is a rare, but devastating complication following coronary artery bypass graft surgery (CABG). We performed a retrospective study of PON associated with off‑pump CABG (OPCABG) to identify possible risk factors. Materials and Methods: 1442 patients underwent OPCABG over a 10‑month period from October 2008 to August 2009; PON was identified in four (0.28%) patients. A retrospective review of the charts was done to identify the patient characteristics, pre‑operative status, intra‑operative details, and ophthalmic examination details. Friedman test was used to compare the hematocrit (Hct) and the mean arterial pressure (MAP) values across the three time periods: Pre‑, intra‑ and post‑operative periods. Results: All four patients were male, diabetic, and in the age range 51‑69 years. All patients noted unilateral or bilateral severe visual loss in the immediate post‑operative period, which was permanent. All the four patients had statistically significant decrease in the Hct (P < 0.039) and mean arterial blood pressure (P < 0.018) in the intraoperative and post‑operative period when compared to pre‑operative value. Conclusions: PON is a rare but definite possibility in patients undergoing OPCABG. Diabetes mellitus may be a risk factor. Perioperative hemodynamic abnormalities like decrease in MAP and anemia may play a role in the development of PON in OPCABG.

Adaptive optics imaging of the retina.

Adaptive optics is a relatively new tool that is available to ophthalmologists for study of cellular level details. In addition to the axial resolution provided by the spectral-domain optical coherence tomography, adaptive optics provides an excellent lateral resolution, enabling visualization of the photoreceptors, blood vessels and details of the optic nerve head. We att empt a mini review of the current role of adaptive optics in retinal imaging. PubMed search was performed with key words Adaptive optics OR Retina OR Retinal imaging. Conference abstracts were searched from the Association for Research in Vision and Ophthalmology (ARVO) and American Academy of Ophthalmology (AAO) meetings. In total, 261 relevant publications and 389 conference abstracts were identified.

Endophthalmitis caused by Acinetobacter calcoaceticus. A profile.

PURPOSE: To report the clinical and microbiological profile of endophthalmitis caused by Acinetobacter calcoaceticus. METHODS: A retrospective study of case series of Acinetobacter calcoaceticus endophthalmitis. Outcome measures included ability to sterilise the eye, anatomical result (clear media and attached retina) and visual recovery (visual acuity > 6/60). RESULTS: Of the 20 cases studied, 10 were cases of postoperative endophthalmitis, 3 were posttraumatic, 6 were endogenous and one was bleb-related endophthalmitis. Specific features of interest observed were relative chronicity of presentation and absence of any obvious predisposing factor in endogenous endophthalmitis cases. All cases could be sterilised except one, which needed evisceration. Cases with postoperative endophthalmitis had better anatomical outcome (7/10 with attached retina and clear media) and visual outcome (4/10 regained vision > 6/18). Higher smear positivity was seen in vitreous samples (72.2%) compared to aqueous samples (37.5%). Culture positivity was higher from the vitreous cavity compared to aqueous. The organism was sensitive to ciprofloxacin in a high percentage (88.9%) of cases. CONCLUSIONS: Visual recovery in Acinetobacter calcoaceticus endophthalmitis is modest. Ciprofloxacin is the antibiotic of choice.