Prevalence and risk factors for diabetic retinopathy among Omani diabetics

AIMS—To study the prevalence of diabetic retinopathy in a population of patients attending a diabetic clinic and to evaluate the medical risk factors underlying its development.
METHODS—500 randomly selected diabetic patients attending the diabetes clinic in Al Buraimi hospital were referred to the ophthalmology department where they were fully evaluated for the absence or presence of retinopathy. Any retinopathy present was graded as mild non-proliferative retinopathy (NPR), moderate-severe NPR, and proliferative retinopathy. Several risk factors were then evaluated in order to delineate those related to occurrence of retinopathy in general as well as to the different grades of retinopathy in particular.
RESULTS—Diabetic retinopathy was detected in 212 patients (42.4%), with mild NPR present in 128 patient (25.6% of the total population), moderate-severe NPR in 20 patients (4%), and proliferative diabetic retinopathy present in 64 patients (12.8%). Factors significantly related to occurrence of retinopathy were age of the patient, duration of diabetes, presence of ischaemic heart disease, presence of hypertension, a high fasting capillary glucose level as well as elevated serum levels of urea, creatinine, cholesterol, and triglycerides. After adjustment for covariates, it was found that duration of diabetes was the only risk factor associated with mild NPR, while high diastolic blood pressure and high levels of serum creatinine, cholesterol, and triglycerides were significantly associated with the occurrence of proliferative retinopathy.
CONCLUSIONS—In addition to glycaemic control, lowering of blood lipids as well as diastolic blood pressure (in hypertensive patients) may be effective in lowering the incidence of retinopathy in compromised patients.

Keywords: diabetic retinopathy; Oman; diabetics     

VEGF localisation in diabetic retinopathy

AIM—To determine the staining pattern of vascular endothelial growth factor (VEGF) at different stages of diabetic retinopathy (including post-laser photocoagulation) and to compare staining in excised fibrovascular and fibrocellular (non-diabetic) preretinal membranes.
METHODS—Immunohistochemical localisation of VEGF, using antibodies raised against VEGF₁₆₅ and VEGF_121,165,189, was carried out on specimens of normal human retina (n=15), diabetic retinas ((a) with no overt retinopathy (n=19), (b) with intraretinal vascular abnormalities but no proliferative retinopathy (n=6), (c) with active proliferative retinopathy (n=6), (d) with no residual proliferative retinopathy after photocoagulation therapy (n=15)), excised diabetic fibrovascular membranes (n=19), and non-diabetic fibrocellular membranes (n=7). The degree and pattern of immunostaining was recorded.
RESULTS—In general, VEGF was absent from the majority of normal retinas. VEGF staining was apparent in most diabetic tissues but the staining pattern was dependent on both the specificity of the antibody used and the category of tissue. Staining with the VEGF₁₆₅ antibody was generally confined to endothelial cells and perivascular regions while the VEGF_121,165,189 antibody was also associated with extravascular components of the inner retina. Intensity of immunostaining of diabetic eyes was dependent on the severity of retinopathy being least in diabetics with no overt retinopathy and greatest in retinas with proliferative retinopathy. Interestingly, the intensity of immunostaining in diabetic retinas which had undergone laser surgery for proliferative retinopathy was reduced to basal levels. Moderate to intense immunostaining was observed in all fibrovascular and fibrocellular membranes examined.
CONCLUSIONS—This study supports a circumstantial role for VEGF in the pathogenesis of both the preclinical and proliferative stages of diabetic retinopathy.

Keywords: vascular endothelial growth factor; VEGF; diabetes; diabetic retinopathy     

Evidence that upregulation of serum IGF-1 concentration can trigger acceleration of diabetic retinopathy

BACKGROUND—Acute reduction of chronic hyperglycaemia can accelerate early diabetic retinopathy. In adolescent patients with Mauriac's syndrome, this phenomenon is related to an upregulation of subnormal serum IGF-1 levels.
AIM—To obtain longitudinal data on serum IGF-1 and retinopathy status in poorly controlled adult insulin dependent (type 1) diabetic patients without Mauriac's syndrome, in whom hyperglycaemia is reduced by intensive insulin therapy.
METHODS—Four patients with chronic severe insulin deficiency and early microangiopathy were studied prospectively. Changes in plasma glucose, HbA_1c, serum IGF-1 levels, proteinuria, retinopathy, and clinical status were followed up closely.
RESULTS—Reducing hyperglycaemia from >16 mmol/l (equivalent to HbA_1c >11%) to <10 mmol/l (HbA_1c <8%) within 5 months increased serum IGF-1 levels by 70-220%. While proteinuria and symptomatic neuropathy regressed, retinopathy progressed from the mild to the severe non-proliferative stage with maculopathy (n=4), and to the proliferative stage (n=1). Laser coagulation was commenced upon the appearance of sight threatening macular oedema (n=4).
CONCLUSION—Upregulation of serum IGF-1 preceding retinal deterioration in these patients suggests a cause-effect relation, consistent with earlier experimental and clinical data.

Keywords: diabetes mellitus; macular oedema; metabolic control; intensive therapy; glycated haemoglobin A_1c; growth factors     

Diabetic retinopathy in Down's syndrome

AIM—To determine the prevalence of diabetic retinopathy in patients with Down's syndrome and diabetes mellitus.
METHOD—Nine patients with Down's syndrome and diabetes mellitus were assessed. Factors recorded included type and duration of diabetes, level of diabetic control, blood pressure, urinalysis, and results of ophthalmological examination.
RESULTS—The duration of diabetes ranged from 8 to 41 years (mean 17.6 years). All had satisfactory glycaemic control and blood pressure measurements on the low side of normal (mean 106.6/70 mm Hg). One patient had early background diabetic retinopathy. The remainder had no evidence of diabetic retinopathy.
CONCLUSION—The low prevalence of diabetic retinopathy in these Down's syndrome patients, despite the long duration, is an interesting finding. It suggests some inherent protective factor against the development of diabetic retinopathy in this patient subgroup.

Keywords: Down's syndrome; retinopathy; diabetes; hypertension     

Serum total renin, an independent marker of the activity and severity of retinopathy in patients with IDDM

BACKGROUND/AIMS—Recent studies have demonstrated marked renin and prorenin concentration gradients between ocular tissues and blood, and local expression of the renin-angiotensin system (RAS) in the eye. The authors determined whether serum total renin, which mostly consists of prorenin, is a marker of the activity and severity of diabetic retinopathy independent of other microvascular complications.
METHODS—Total renin concentrations (TRC) were measured with a time resolved immunofluorometric assay in 38 patients with IDDM (age 34 (SD 7) years, duration of disease 22 (7) years, serum creatinine 95 (15) µmol/l, urinary albumin excretion rate (UAER) 207 (829) µg/min, HbA_1c 8.5% (1.2%)), and in 13 matched normal subjects. All subjects were carefully characterised with respect to the presence and severity of retinopathy (RP score), nephropathy, and neuropathy using seven different tests of autonomic neuropathy.
RESULTS—Serum TRC was on average twofold higher in IDDM (396 (SE 211) ng/l) than in normal subjects (201 (88) ng/l, p<0.001). It was nearly twofold higher in patients with preproliferative or active proliferative retinopathy requiring careful follow up or therapy (TRC 596 (268) ng/l, n=11) compared with those with quiescent proliferative retinopathy after laser treatment (TRC 338 (183) ng/l, p<0.01, n=5); moderately severe non-proliferative retinopathy (337 (106) ng/l, p<0.01, n=13), no retinopathy, or only minimal non-proliferative retinopathy (270 (43) ng/l, p<0.001, n=9). In multiple linear regression analysis, RP score (p<0.01), but not the UAER or any index of autonomic neuropathy, was an independent determinant of serum TRC, and explained 32% of its variation (R=0.57, p<0.005).
CONCLUSIONS—Serum TRC in patients with diabetic retinopathy is increased independent of renal function and autonomic neuropathy, especially in those with severe active changes requiring careful follow up or treatment. These findings support the idea that diabetic retinopathy is the most important determinant of serum TRC in patients with IDDM, and that TRC is produced when retinopathy is active.

Keywords: diabetes; prorenin/total renin; retinopathy; nephropathy; neuropathy     

Retinal vessel dilatation and elongation precedes diabetic macular oedema

AIMS/BACKGROUND—Retinal vessel dilatation is a well known phenomenon in diabetes. In this study, the theory of whether excessive changes in diameter and length of retinal vessels occur in the development of diabetic macular oedema was tested, supporting a hypothesis that the development of diabetic macular oedema may be linked to hydrostatic pressure changes described in Starling's law.
METHODS—From fundus photographs of diabetic patients attending a regular eye screening programme, the diameter and segment length of retinal vessels were measured in three retinopathy groups (12 patients each) with diabetic macular oedema (DMO), background retinopathy and no retinopathy, over a period of approximately 4 years, ending at the time of diagnosis of diabetic macular oedema in the DMO group.
RESULTS—A statistically significant dilatation and elongation of retinal arterioles, venules, and their macular branches was found before the diagnosis of macular oedema in the DMO group. No significant changes were found in the other two groups.
CONCLUSION—It is suggested that Starling's law applies to the formation of oedema in the retina as in other tissues.

     

Detection of eicosanoids in epiretinal membranes of patients suffering from proliferative vitreoretinal diseases

AIM—Arachidonic acid is metabolised via lipoxygenase to 15-HETE (15-hydroxyeicosatetraenoic acid) and 15-HPETE (15-hydroperoxyeicosatetraenoic acid), which are believed to influence proliferation in tissue culture. 15-HETE is the reduction product of 15-HPETE. Cell proliferation is believed to be decreased by 15-HPETE and increased by 15-HETE. The aim of this study was to investigate epiretinal membranes for the presence of these lipoxygenase products and to compare membranes from different disease processes.
METHODS—Epiretinal membranes of 15 patients suffering from proliferative vitreoretinopathy (PVR, n=7) and proliferative diabetic retinopathy (PDR; n=8) were removed during vitrectomy and analysed by means of thin layer chromatography. The plates were evaluated by digital image analysis.
RESULTS—Both 15-HETE and 15-HPETE were identified in membranes from eyes of patients with PVR and PDR with HETE values significantly higher (p<0.05) than HPETE values (HETE/HPETE ratio = 5.2).
CONCLUSION—This study demonstrates that eicosanoids are present in the epiretinal membrane tissue of patients with PVR and PDR. Considering that HETE increases cell proliferation while HPETE inhibits it, it is conceivable that eicosanoids are an additional factor contributing to the regulation of membrane growth in proliferative retinal disorders. Thus, inhibition of lipoxygenase could be a therapeutic approach in these diseases.

     

Retinal thickness variation in the diabetic patient measured by the retinal thickness analyser

AIM—To evaluate the potential of the retinal thickness analyser (RTA) as an objective tool for assessment and follow up of diabetic macular oedema.
METHODS—A prototype of the RTA that operates on the principle of laser slit biomicroscopy was used. Retinal thickness was obtained in 41 eyes of 41 diabetic patients. The clinical diagnosis was cystoid macular oedema (CMO) in 10 eyes, clinically significant macular oedema (CSMO) without retinal cysts in 21 eyes, and "dry" macula following grid pattern laser treatment in 10 eyes. The control group consisted of 46 eyes of age matched healthy volunteers.
RESULTS—In normal eyes (46 eyes), the foveal thickness measured was 178 (SD 44) µm and the macular thickness around the fovea was 311 (51) µm. The eyes with CMO displayed the largest foveal thickening, 875 (287) µm (390% increase compared with normal values). The average thickness of the fovea in the non-cystoid CSMO group was 427 (175) µm (144% increase compared with normal fovea). The average thickness of the foveal centre in eyes judged as having "dry" macula after laser treatment was 315 (71) µm (77% increase compared with normal value and a 26% decrease in thickness compared with the CSMO eyes). Statistically significant differences were found in central thickness between these four groups (p = 0.0001). The average thickness at 500 µm surrounding the fovea was 566 (202) µm in the CSMO eyes compared with 311 (51) µm in normal eyes (80% increase). The "dry" macula group (after undergoing laser treatments) had an average thickness of 414 (94) µm (27% decrease compared with CSMO eyes and a 33% increase compared with eyes of healthy controls).
CONCLUSIONS—RTA is a system for quantifying macular thickness and imaging of macular pathology. The system can be a useful tool for diagnosis of macular diseases and for evaluation of the effect of treatment modalities.

Keywords: diabetic retinopathy; retinal thickness; macular oedema; retinal imaging     

Ocular abnormalities in thin basement membrane disease

AIM/BACKGROUND—Alport syndrome is an X linked disease that results in renal failure, deafness, and ocular abnormalities including a dot and fleck retinopathy and anterior lenticonus. The ultrastructural appearance of the glomerular basement membrane in thin basement membrane disease (TBMD) resembles that seen in some patients with Alport syndrome, and in some cases this disease is inherited too. The aim of this study was to determine whether patients with TBMD have any ocular abnormalities.
METHODS—The eyes of 17 unrelated individuals with TBMD were studied by slit-lamp, including biomicroscopic fundus examination with a 78 D lens, by direct ophthalmoscopy, and by fundal photographs. The findings were compared with those in patients with IgA glomerulonephritis or Alport syndrome, and in normals.
RESULTS—No patient with TBMD had a dot and fleck retinopathy or anterior lenticonus. A corneal dystrophy (n = 2) or pigmentation (n = 1), and retinal pigment epithelial clumping and maculopathy (n = 1) were noted. Corneal, lens, and retinal dots were found in five (29%), three (18%), and 16 (94%) patients, respectively, but these were also demonstrated in individuals with other renal diseases and in normal individuals.
CONCLUSIONS—The dot and fleck retinopathy and anterior lenticonus typical of Alport syndrome do not occur in TBMD. The protein abnormality and genetic defect in TBMD are not known, but the lack of ocular lesions suggests that the abnormal protein in this disease is more sparsely distributed or less important in the basement membranes of the eye than of the kidney. Alternatively, the protein may be less affected by the mutations responsible for TBMD.

     

Longer term visual outcome of eyes with retinopathy of prematurity treated with cryotherapy or diode laser

AIMS—Visual outcome of 66 eyes in 37 patients who had undergone treatment with either cryotherapy or diode laser for threshold retinopathy of prematurity was assessed.
METHODS—17 patients, representing 30 eyes treated with cryotherapy, were examined at between 56 and 98 months corrected age (median 68 months). 20 patients representing 36 eyes treated with diode laser, were examined at between 30 and 66 months corrected age (median 51 months). Structural outcome was categorised as: optimal—flat posterior pole; suboptimal—macular ectopia, optic nerve hypoplasia, retinal fold involving the macula, and retinal detachment involving the macula.
RESULTS—Optimal structural outcome was, in the absence of amblyopia, associated with optimal visual acuity (of 6/12 or better) in all cases, with most eyes achieving a visual acuity of 6/9 or 6/6. Suboptimal structural outcome was invariably associated with suboptimal visual acuity. Amblyopia was present in eight out of 20 cryotherapy treated eyes and in five out of 26 laser treated eyes with an optimal structural outcome. Refractive errors were significantly less in laser treated eyes as was the incidence of anisometropic amblyopia.
CONCLUSION—Eyes treated with either cryotherapy or diode laser for threshold retinopathy of prematurity with optimal structural outcome are associated with development of optimal visual acuity—that is, 6/12 or better. Treatment with either cryotherapy or laser does not in itself reduce the visual potential of these eyes.

Keywords: retinopathy of prematurity; cryotherapy; laser; visual acuity     

Use of eye care services by people with diabetes: the Melbourne Visual Impairment Project

AIM—The use of eye care services by people with and without diabetes was investigated in the Melbourne Visual Impairment Project (VIP), a population based study of eye disease in a representative sample of Melbourne residents 40 years of age and older.
METHODS—A comprehensive interview was employed to elicit information on history of diabetes, medication use, most recent visit to an ophthalmologist and optometrist, and basic demographic details. Presence and extent of diabetic retinopathy was determined by dilated fundus examination.
RESULTS—The Melbourne VIP comprised 3271 people who ranged in age from 40 to 98 years; 46.2% of them were male. Of 3189 people who had the fundus examination and knew their diabetes status, 162 (5.1%) reported having been previously diagnosed with diabetes and, of these, 37 (22.2%) were found to have diabetic retinopathy. Seven people (4.3%) had developed diabetes before age 30. The mean duration of diabetes was 9.2 years. People with diabetes were significantly more likely to have visited an ophthalmologist ever or in the past 2 years than people without diabetes. However, 31.8% of people with diabetes had never visited an ophthalmologist. The proportion of people who had never seen an ophthalmologist was 47.1% for people without diabetes, 34.2% for people with diabetes but without diabetic retinopathy, and 25% for people with diabetic retinopathy. Sixty one per cent of people with diabetic retinopathy had seen an ophthalmologist in the past year and a further 3% within the past 2 years. People with diabetes were not significantly more likely to have visited an optometrist than people without diabetes (p=0.51). Overall, 37.7% of people with diabetes and 32.9% of people without diabetes had visited an optometrist within the past year (χ²=2.25, 1 df, p=0.13). Information concerning retinal examinations was available for 135 individuals (83.3% of people with diabetes). Only 74 (54.8%) could recall ever having a dilated fundus examination; 10 (14%) by an optometrist, 62 (86%) by an ophthalmologist, and five (7%) by a general practitioner. Of those 68 people who had seen an ophthalmologist in the past 2 years, 48 (71%) reported a dilated fundus examination during that time. This compares with 28 (43%) reported dilated fundus examinations in the 65 people who had seen an optometrist in the past 2 years. This finding is statistically significant (χ²=10.2, 1 df, p<0.005).
CONCLUSION—These results indicate that nearly half of people with diabetes in Melbourne are not receiving adequate screening or follow up for diabetic retinopathy, despite universal health care.

Keywords: diabetes; diabetic retinopathy; screening guidelines     

Three year visual outcome for treated stage 3 retinopathy of prematurity: cryotherapy versus laser

BACKGROUND/AIMS—In the management of retinopathy of prematurity (ROP), several studies have demonstrated laser photocoagulation to be as effective as cryotherapy in reducing the incidence of unfavourable structural outcome. However, few data are available on the functional outcome. The 3 year visual acuity outcome of infants treated with laser or cryotherapy in a neonatal unit is presented.
METHODS—The case notes of 34 infants (64 eyes) treated with cryotherapy, between 1989 and 1992, and 32 infants (59 eyes) treated with laser, between 1992 and 1995, were reviewed.
RESULTS—In the cryotherapy group 69% of eyes had a favourable structural outcome. Of these structurally successful eyes 62.5%, 35.0%, and 33.3% of eyes had visual acuities within normal limits at the 12 month, 24 month, and 36 month corrected age milestones respectively. In the laser group 93% of eyes had a favourable structural outcome. Of these structurally successful eyes 96.4%, 66.7%, and 59.5% of eyes had visual acuities within normal limits at the 12 month, 24 month, and 36 month corrected age milestones respectively.
CONCLUSION—In the management of ROP, when laser photocoagulation induces a structurally successful result, the potential for normal visual acuity development at 3 years is high. Whether the poorer functional outcome of the eyes treated with cryotherapy is an artefact of the historical nature of the study or as a result of an adverse effect of the destructive transcleral application is unknown.

Keywords: retinopathy of prematurity; laser; cryotherapy; visual outcome     

Altered retrobulbar vascular reactivity in early diabetic retinopathy

AIM/BACKGROUND—In diabetic eye disease the factors leading to compromised circulation and the resulting loss of visual function are poorly understood. Although retinal circulation has been widely investigated, it accounts for only a fraction of total eye blood flow. Blood flow was investigated in the larger vessels feeding the eye in patients with early diabetic retinopathy.
METHODS—Eleven patients with early diabetes with minimal or no retinopathy and 11 healthy controls were evaluated for retrobulbar blood flow velocity using colour Doppler imaging for the ophthalmic and central retinal arteries. Patients and subjects were tested while breathing room air and again under conditions of isocapnic hyperoxia.
RESULTS—Hyperoxia induced a significant change in the central retinal artery end diastolic velocity (EDV) (p = 0.008) and resistance index (RI) (p = 0.032) in normal subjects, but not in diabetic patients. Consequently, during hyperoxia, the diabetic patients were significantly higher for EDV (p = 0.006) and significantly lower for RI (p = 0.002) compared with normal controls. Hyperoxia caused no significant change in either group in the ophthalmic artery; nevertheless, under isocapnic hyperoxia conditions the diabetic patients had lower peak systolic velocity (p = 0.05) and lower RI (p = 0.05) than normal subjects.
CONCLUSIONS—Imposition of isocapnic hyperoxia produces significant differences in the ophthalmic and central retinal artery blood flow velocities in diabetic patients with early disease when compared with normal subjects. These results demonstrate that diabetic patients with minimal or no retinopathy suffer from irregular ocular vascular function in the major vessels feeding the eye.

     

Bilateral involvement by age related maculopathy lesions in a population

AIMS—To describe the influences of age and sex on the frequency of bilateral age related macular degeneration (AMD) and age related maculopathy (ARM) lesions.
METHODS—The Blue Mountains Eye Study examined 3654 older Australians, 82% of permanent residents living in an area west of Sydney. Stereo macular photographs were graded for AMD (neovascular maculopathy and geographic atrophy) and early ARM lesions (soft drusen, reticular drusen, hyperpigmentation, and hypopigmentation).
RESULTS—Among 230 gradable cases of AMD or early ARM, 183 (80%) were bilateral. For AMD, 39/69 cases (57%) were bilateral, while for early ARM, 123/161 cases (77%) had signs in both eyes. Of the individual lesions, reticular drusen (91%) and indistinct soft drusen (79%) were most frequently present in both eyes. Geographic atrophy was bilateral in 56%, neovascular AMD in 40%, and distinct soft drusen in 47%, while hyperpigmentation was bilateral in 38% and hypopigmentation in only 28% of cases. A consistent age related increase in bilateral distribution was observed for most lesions. After adjusting for effects of age, current smoking, and AMD family history AMD and ARM component lesions, except for soft drusen, were more frequently bilateral in women. This sex difference was significant only for neovascular AMD, odds ratio 7.7 (95% confidence intervals 1.3-46.7). An AMD family history was more frequently reported in cases with bilateral involvement.
CONCLUSIONS—This study has documented differences in the age related bilaterality of individual ARM components with higher bilateral rates for reticular or indistinct soft drusen compared with other lesions. The increased bilaterality of most ARM lesions among women is likely to contribute to the increased age adjusted risk of AMD blindness found in women.

Keywords: age related maculopathy; age related macular degeneration; drusen     

Sensitivity and specificity of a new scoring system for diabetic macular oedema detection using a confocal laser imaging system

AIM—To assess the use of the Heidelberg retina tomograph (HRT) in screening for sight threatening diabetic macular oedema in a hospital diabetic clinic, using a new subjective analysis system (SCORE).
METHODS—200 eyes of 100 consecutive diabetic patients attending a diabetologist's clinic were studied, all eyes had an acuity of 6/9 or better. All patients underwent clinical examination by an ophthalmologist. Using the HRT, one good scan was obtained for each eye centred on the fovea. A System for Classification and Ordering of Retinal Edema (SCORE) was developed using subjective assessment of the colour map and the reflectivity image. The interobserver agreement of using this method to detect macular oedema was assessed by two observers (ophthalmic trainees) who were familiarised with SCORE by studying standard pictures of eyes not in the study. All scans were graded from 0-6 and test positive cases were defined as having a SCORE value of 0-2. The sensitivity of SCORE was assessed by pooling the data with an additional 88 scans of 88 eyes in order to reduce the confidence interval of the index.
RESULTS—12 eyes in eight out of the 100 patients had macular oedema clinically. Three scans in three patients could not be analysed because of poor scan quality. In the additional group of scans 76 out of 88 eyes had macular oedema clinically. The scoring system had a specificity of 99% (95% CI 96-100) and sensitivity of 67% (95% CI 57-76). The predictive value of a negative test was 87% (95% CI 82-99), and that of a positive test was 95% (95% CI 86-99). The mean difference of the SCORE value between two observers was -0.2 (95% CI -0.5 to +0.07).
CONCLUSIONS—These data suggest that SCORE is potentially useful for detecting diabetic macular oedema in hospital diabetic patients.

     

Plasminogen in proliferative vitreoretinal disorders

OBJECTIVE—Intravitreal fibrin formation is a frequent observation after vitrectomy performed for a variety of vitreoretinal disorders including proliferative vitreoretinopathy (PVR), proliferative diabetic retinopathy (PDR), and endophthalmitis. Plasminogen activators (PA) have been used for the management of this postoperative complication. This approach requires the presence of plasminogen, the substrate for PA mediated fibrinolysis, in the vitreal cavity.
METHODS—Quantification of plasminogen in the vitreous of 60 patients with PVR, PDR, and macular pucker was performed by streptokinase mediated activation using a chromogenic substrate. The presence of immunoreactive plasminogen was confirmed by immunoblot analysis of vitreal proteins and immunocytochemistry of surgically removed epiretinal membranes.
RESULTS—Plasminogen levels were dramatically increased in the vitreous of PVR and PDR patients compared with macular pucker patients and normal controls. Staining for plasminogen in epiretinal membranes was confined to the extracellular matrix. Predominant staining of perivascular areas in PDR specimens indicated that breakdown of the blood-retinal barrier is an important source of intravitreal plasminogen in that condition.
CONCLUSION—Plasminogen may play a role in traction membrane formation in PVR and PDR. Our biochemical analysis of presurgical vitreous indicates that there may be abundant substrate for PA mediated fibrinolysis in the vitreous cavity after vitrectomy.

     

Ophthalmological long term follow up of preterm infants: a population based, prospective study of the refraction and its development

BACKGROUND—Numerous studies have reported an increased risk of refractive errors in prematurely born infants, but only few have been long term and strictly population based.
METHODS—A 3.5 year ophthalmological long term follow up of 248 preterm infants was performed. The infants had been included in a previous epidemiological study of retinopathy of prematurity (ROP) (birth weight  1500 grams). The incidence of refractive errors and development of refraction were studied, based on retinoscopies at 6 and 30 months of corrected age.
RESULTS—The overall incidence of myopia was 8% at 6 months, of which 35% was transient, and 10% at 30 months. Of the cryotreated infants, 30-40% were myopic at both retinoscopies. The incidence of astigmatism was 52% at 6 months and 26% at 30 months. Astigmatism was associated with ROP, but not with cryotreated ROP itself. Astigmatism "against the rule" was commoner than astigmatism "with the rule". Anisometropia occurred in 6.5% of the infants at 6 months and in 8.4% at 30 months. The incidence of anisometropia was higher in eyes with ROP, particularly in cryotreated eyes, which tended to have high and persistent anisometropia.
CONCLUSION—The risk of refractive errors is higher in preterm infants than in infants born at term, and also prematurely born infants without ROP do run an increased risk of having myopia and anisometropia. We recommend follow up examinations with retinoscopy for all infants included in screening programmes for ROP.

Keywords: prematurity; prospective study; retinopathy of prematurity; refraction     

Do patients with age related maculopathy and cataract benefit from cataract surgery?

AIMS—To assess the benefits of cataract extraction in patients with age related maculopathy (ARM).
METHODS—1073 randomly selected cataract operations were reviewed and 99 cases of preoperatively recognised ARM were identified for investigation. Data relating to visual function were retrieved from case notes, and patient responses to a questionnaire were analysed.
RESULTS—98% had dry or unspecified ARM. Only 2% had exudative maculopathy. 81% of cases had an improvement in best distance acuity; mean change 0.44 logMAR (change of 6/36 to 6/12). 65% responded to the questionnaire; 67% felt that the operation had been worthwhile, 17% had mixed feelings, and 17% thought it not worthwhile.
CONCLUSION—This study, which is the first of its kind to be reported, shows a clear benefit from cataract surgery in the majority of patients with ARM. However, the prevalence of ARM in this study is lower than expected, suggesting that some patients with both ARM and cataract were not listed for surgery. The design of a prospective study to quantify the subjective and objective benefits of cataract surgery in these patients is outlined and predictors of successful outcome identified. This will promote the development of guidelines for the surgical management of this group of patients.

Keywords: age related maculopathy; cataract; cataract surgery; outcome assessment; questionnaire     

Partial reversal of protan and tritan colour defects with inhaled oxygen in insulin dependent diabetic subjects

AIMS—Abnormalities in colour perception occur early in the development of diabetic retinopathy. Whether these changes can be influenced by increasing circulating oxygen saturation was studied in comparison with non-diabetic controls.
METHODS—Protan and tritan colour thresholds were measured using a computer graphics system in 37 insulin dependent diabetic subjects, with no or minimal background retinopathy, and 27 matched controls. Colour thresholds were performed after subjects inhaled either gaseous air or 100% oxygen for a minimum of 5 minutes.
RESULTS—Diabetic subjects had higher colour vision thresholds when inhaling air when compared with controls (protan (mean 3.93 (SEM 0.39), v 2.36 (0.16), p<0.0002) and tritan (8.15 (0.62) v 5.42 (0.31), p <0.002)). The colour vision thresholds observed in diabetic subjects inhaling air fell when they inhaled oxygen (protan (3.93 (0.39) v 3.57 (0.33), p <0.025) and tritan (8.15 (0.62) v 7.35 (0.59), p<0.005)). No fall in colour thresholds was seen in non-diabetic controls who inhaled oxygen.
CONCLUSION—A small improvement in the colour vision thresholds was observed using computer graphics in diabetic subjects, with minimal or no retinopathy, who inhaled oxygen. This study supports a hypothesis that reduced retinal oxygenation contributes to the colour vision defects in diabetes.

     

Effects of 0.5% apraclonidine on optic nerve head and peripapillary retinal blood flow

AIMS—To examine the effects of 0.5% apraclonidine on optic nerve head (ONH) and peripapillary retinal blood flow by scanning laser Doppler flowmetry (SLDF).
METHODS—ONH and peripapillary retinal blood flow of 17 healthy subjects were measured by SLDF before and 1 hour and 3 hours after unilateral administration of 0.5% apraclonidine. The fellow eyes were treated with balanced salt solution and the examiners were masked as to which eye was treated with apraclonidine. On each occasion, three scans were obtained and haemodynamic variables (volume, flow, and velocity) were analysed at eight locations, four in the neural rim and four in the peripapillary retina, avoiding ophthalmoscopically visible vessels. The statistical significance of changes from the baseline value of variables and the differences in the measured quantities between apraclonidine treated eyes and fellow eyes at each time point were evaluated using Wilcoxon signed rank test.
RESULTS—The intraocular pressure was reduced significantly in apraclonidine treated eyes by 15.0% (p=0.001) at 1 hour and 30.0% (p=0.000) at 3 hours after administration. In the volume, flow, or velocity of ONH and peripapillary retinal blood flow, there were no significant changes from the baseline values at 1 hour and 3 hours after apraclonidine administration in either apraclonidine treated eyes (p >0.4) or fellow eyes (p >0.2). Also, no significant differences were found in the measured quantities between apraclonidine treated eyes and fellow eyes at each time point (p >0.1).
CONCLUSION—A single dose of topical apraclonidine 0.5% in healthy subjects does not have adverse effects on the ONH and peripapillary retinal blood flow.