Structure-function relationship in early diabetic retinopathy: a spatial correlation analysis with OCT and microperimetry.

PurposeTo study the correlation of the local ganglion cell layer-inner plexiform layer (GCL-IPL) thickness with corresponding retinal sensitivity as studied with microperimetry in patients with Type 2 diabetes and no signs of diabetic retinopathy.Patients and methodsWe analyzed 35 healthy subjects (68 eyes) and 26 Type 2 diabetic patients (48 eyes) with no signs of diabetic retinopathy. We tested best corrected visual acuity (BCVA), monocular and binocular constrast sensitivity (CS, Pelli - Robson chart) and retinal sensitivity with microperimetry, and acquired dense macular SD-OCT scans. We then studied the correlation between local GCL-IPL thickness and local sensitivity.ResultsMean BCVA was 1.09 (±1.03) decimals in diabetic subjects and 1.02 (±0.15) decimals in healthy subjects. Only binocular CS was significantly higher in healthy subjects (1.18±0.42 for healthy subjects, 1.62±0.63 for diabetic subjects). In both local and global analysis we observed higher GCL-IPL thickness and higher sensitivity in normal compared with diabetic subjects, but no difference reached significance (p<0.05). Using a mixed multivariate linear model, we found a significant correlation between retinal sensitivity and the correspondent GCL-IPL thickness in diabetic subjects (0.022±0.006 dB/µm, p=0.0007) but not in healthy subjects (-0.002±0.006 dB/µm, p=0.77).Conclusiondespite close similarities between the two groups, we found a significant difference in the structure-function relationship in diabetic subjects without diabetic retinopathy, suggesting that diabetes might act as an additional effect in the normal deterioration of the visual function related to the inner retina.

Subretinal neovascularization after naphthalene damage to the rabbit retina.

PURPOSE: To examine the retinotoxic effect of naphthalene, a powerful oxidative agent and a well-known cataractogenic agent. METHODS: A 10% solution of naphthalene dissolved in paraffin oil was given every other day by gavage to 31 pigmented rabbits for 5 weeks, at a dose of 1 g/kg body weight. Four rabbits who received only paraffin oil served as controls. The eyes were clinically followed up by means of ophthalmoscopy and retinal fluorangiography. At selected intervals, the eyes were examined with light microscopy and transmission electron microscopy. RESULTS: The first lesions were focal and appeared in the periphery of the fundus about 3 weeks after the beginning of treatment and tended to spread over the entire retina. Histologically, there was a degeneration of photoreceptors, accompanied by a reaction and proliferation of retinal pigment epithelium (RPE) that phagocytized the damaged visual cells. After about 3 months, the proliferation of RPE was followed by subretinal neovascularization (SRN). Both mature fenestrated and thick-walled non-fenestrated capillaries penetrated Bruch's membrane, enveloped by abundant fibrous extracellular matrix and accompanied by pericytes. As a consequence of this process, the retina was focally transformed into a "neovascular complex" in which a vascular plexus was intermingled with pseudo-acinar cavities lined by RPE. There were no signs of SRN at retinal fluorangiography, possibly because of the dense microenvironment of extracellular matrix and RPE cells of the neovascular complexes. CONCLUSIONS: Naphthalene degeneration of the rabbit retina appears to be a simple model of photoreceptor vulnerability in the first stages of SRN thereafter. The close chronologic and topographic relationship between the appearance of the anomalous vessels and RPE alteration and the close resemblance with previous models of experimental SRN may support the hypothesis of an experimental model of SRN triggered by the RPE.

Experimental short-term tolerance to perfluorodecalin in the rabbit eye: a histopathological study.

PURPOSE: Perfluorocarbon liquids are largely used in vitreoretinal surgery, but their permanence into the eye is considered harmful and early withdrawal is routinely performed by most of the surgeons. We undertook this investigation to evaluate the effects of Perfluorodecalin (PFD) tamponade following vitrectomy in the rabbit eye. METHODS: Twenty-four rabbits underwent vitrectomy of the right eye according with a standard procedure. Eighteen rabbits received PFD and 6 control rabbits received Balanced Salt Solution (BSS) as vitreous substitute. The eyes were examined with light microscopy and transmission electron microscopy after two, four and six days after tamponade and thirty days after the withdrawal of PFD. RESULTS: The tamponade lasting four or more days caused irreversible retinal damage involving the photoreceptors and retinal pigment epithelium. Peculiar impressions were formed in the inner retina at the site of the gravitational effect of PFD droplets. CONCLUSIONS: Based on the results of this study we suggest that the tamponade with PFD lasting more than two days is detrimental to the retina, at least in the case of the rabbit. Damage seems to be related only to the high specific gravity of PFD.

Trends in cataract surgery in Milan (Italy) from 1956 to 1987. Relationship to age and visual acuity.

In order to test whether the mean age at cataract surgery has changed over the course of the last 30 years, a hospital series of 5443 patients undergoing cataract extraction between 1956 and 1987 is reviewed. All cases attended the same University Eye Clinic of Milan and most were resident in the same geographical area. Cases with macular or optic nerve diseases were excluded. Results show that mean age at cataract surgery progressively increased from 67.5 to 71.5 years (slope = +0.096 years of age per year, p = 0.0001) as did visual acuity at surgery (patients with visual acuity levels greater than or equal to 1/10 at time of cataract surgery rose from 3.2% to 47.9%). These results can be interpreted in terms of a change in age composition of the Italian population, improved access to health services for the elderly, and an improvement in surgical and rehabilitation techniques.