Falsely nonrecordable flash visual evoked cortical potentials in a diabetic eye with severe vitreous hemorrhage

The examination of visual evoked cortical potentials (VECPs) prior to vitrectomy has been proposed for selection of patients with good chances for a favorable outcome following surgery. A missing single flash VECP has been considered a contraindication for further surgical treatment. A 64-year-old woman with proliferative diabetic retinopathy suffered from an intensive vitreous hemorrhage in one eye. Preoperatively, the flash VECP was nonrecordable. Intraoperatively, a dense vitreous hemorrhage and retrohyaloidal blood was found. The retina was attached. Postoperatively, the flash VECP was similar in both eyes with normal latencies. The visual acuity improved from light perception to 0.05. Severe vitreous hemorrhage may interfere with preoperative VECP recordings. A nonrecordable VECP has to be judged cautiously so as to prevent false-negative responses in eyes that could regain vision following vitrectomy and removal of the hemorrhage.

[Evolution of blood glucose control and retinopathy during long-term treatment of insulin-dependent diabetes mellitus with intraperitoneal infusion of insulin]

To evaluate the efficacy on blood glucose control of long-term peritoneal insulin infusion and its consequences on the evolution of diabetic retinopathy, we analyzed retrospectively the values of glycosylated haemoglobin measured quarterly and the retinal angiograms obtained after 1, 5 and 9 years from seventeen insulin-dependent diabetic patients treated by this technique during 9.0 +/- 2.2 years. Blood glucose control was significantly improved from the first year of treatment (p < 0.01). Seventy-one per cent of patients had a level of glycosylated hemoglobin below one standard deviation of normal values after five years and ninety-two per cent of 12 patients treated up to nine years remained in the same near-normal range. Glycaemic excursions below 0.5 g/l and over 2 g/l were limited to 5-7% and 15-17% of four times-daily capillary glucose measurements respectively, along the whole IP insulin infusion period. Among 7 patients with no retinopathy (n = 1) or with mild to moderate nonproliferative retinopathy, requiring no specific ophthalmological treatment, (levels 20 to 40 on worse eye according to a simplified version of ETDRS classification, n = 6), 3 remained stable, 2 improved and 2 impaired although remaining under level 50 of the classification, after 5 to 9 years. Nine patients with severe nonproliferative (level 50, n = 1) or proliferative (level 65, n = 8) retinopathy, all treated by panretinal photocoagulation before initiation of IP treatment, improved and one patient with severe nonproliferative retinopathy, incompletely treated by laser photocoagulation, remained stable, after 5 to 9 years. No macular edematous reaction or impairment of existing macular edema occurred after panretinal photocoagulation under IP treatment. These data indicate that a sustained near-normal blood glucose control can be achieved under long-term peritoneal insulin infusion, without significant impairment of diabetic retinopathy when an initial ophthalmological evaluation, and a specific treatment if necessary, are performed.

Cost-benefit analysis of diabetic eye disease

Diabetic retinopathy is the main cause of blindness in adults 25-74 years of age in Western countries. At 100% diagnosability and 100% treatability, with laser photocoagulation vision can be retained in at least one eye in 73% of patients with proliferative retinopathy and in 67% of patients with diabetic maculopathy. The cost-benefit analysis draws a comparison of the costs incurred through benefits granted to a blind diabetic and those incurred through proper screening, examination and treatment to avoid blindness as much as possible. These calculations are valid for the State of Tyrol in Austria. The anticipated annual costs for blindness are thus ATS 19,000,000, of which ATS 14,600,000 could be avoided through an optimal screening, examination and therapy program. The maximum costs for examination and therapy amount to ATS 10,700,000, thus giving a minimum saving of ATS 3,900,000 in favor of preventive medicine.

Ocular blood flow velocities in patients with proliferative diabetic retinopathy after scatter photocoagulation. Two years of follow-up

PURPOSE

Color Doppler imaging allows for simultaneous two-dimensional anatomic imaging and Doppler measurement of blood flow velocity. Because hemodynamic changes have been seen in diabetic patients after photocoagulation by other techniques, the authors compared 25 eyes with proliferative diabetic retinopathy before, 6 months after, 1 year after, and 2 years after panretinal photocoagulation with a matched control group of 30 healthy volunteers (55 eyes).

METHODS

The ophthalmic artery, short posterior ciliary artery, central retinal vessels, and vortex veins of all patients were examined, and the systolic, and diastolic, and mean arterial velocities were measured. Panretinal photocoagulation was performed with these parameters: 800-1000 spots, 0.1 second, 500-microns argon laser.

RESULTS

Student's t test revealed that the perfusion velocity was significantly lower in diabetic patients than in healthy controls (V systolic in the ophthalmic artery: 31.7 +/- 6.7 cm/s vs. 36.6 +/- 7.0 cm/s, respectively, P = 0.03). After treatment, blood flow velocities were significantly lower than before photocoagulation (V systolic in the ophthalmic artery: 6 months after treatment, 26.9 +/- 7.2 cm/s, P = 0.018; 1 year after photocoagulation, 25.5 +/- 7.0 cm/s, P = 0.009; and 2 years after photocoagulation, 25.7 +/- 6.8 cm/s, P = 0.01). No statistically significant differences were found between 6 months, 1 year, and 2 years after panretinal photocoagulation. No significant correlations were found between patient age and blood velocities in diabetics and healthy volunteers.

CONCLUSIONS

Eyes with proliferative diabetic retinopathy showed lower ocular perfusion velocities than controls. Photocoagulation resulted in a reduction in ocular blood flow velocities; these values did not change during 2 years of follow-up.

[Vitrectomy in ocular complications of diabetes. I. Early and late results of vitrectomy]

Results of 168 pars plana vitrectomies (ppV) of 144 diabetics are presented. In 26.2% of eyes before surgery, vitreous hemorrhage without detachment of the retina was present. In the remaining eyes, different stages of tractional detachment occurred. Visual acuity worse than 1/50 was observed in 83.9% of eyes before surgery. Results of ppV were evaluated on the 7th day and after the 3rd, 6th, 12th and 18th month following the procedure. Anatomical and functional success was achieved in about 80% and 67% of treated eyes, respectively, over the whole follow-up period.

Early photocoagulation in patients with either type I or type II diabetes

OBJECTIVE

To determine the benefits of early photocoagulation in patients with type I versus type II diabetes.

DESIGN

One eye of each of 3,711 patients was randomly assigned to early photocoagulation; the other was assigned to deferral of photocoagulation, with follow-up visits scheduled every 4 months and photocoagulation to be carried out promptly if high-risk proliferative retinopathy developed. Patients were categorized by age and type of diabetes.

MAIN OUTCOME MEASURES

Best corrected visual acuity was measured at each study visit scheduled at 4-month intervals. Stereoscopic fundus photographs were taken and evaluated at baseline, 4 months, and yearly thereafter. Retinopathy severity was assessed from fundus photographs. Severe visual loss was defined as visual acuity of worse than 5/200 for at least two consecutive study visits.

RESULTS

Previously published results of the Early Treatment Diabetic Retinopathy Study (ETDRS) demonstrated a statistically significant benefit of early photocoagulation in preventing severe vision loss. Further analyses demonstrate that this benefit of early photocoagulation is greater in patients with type II diabetes than in those with type I. The relative benefit of early photocoagulation in patients with type II diabetes is also seen for other outcomes (development of high-risk proliferative retinopathy, development of the combined end point [severe visual loss or vitrectomy], development of moderate visual loss, or development of legal blindness). The patients most likely to benefit from early photocoagulation had severe nonproliferative retinopathy or early proliferative retinopathy. Analyses from the Diabetic Retinopathy Study confirm the relative benefit of scatter photocoagulation for type II patients. Because of the high correlation between age and type of diabetes, analyses sub-grouped by age show similar results.

CONCLUSION

These analyses suggest that patients with type II diabetes, or older patients with diabetes, are more likely to benefit from early scatter photocoagulation than patients with type I diabetes. The current standard of care is to initiate scatter photocoagulation as the severity of retinopathy approaches or reaches the high-risk stage, Provided careful follow-up is possible, ETDRS data do not show that initiating scatter photocoagulation prior to the development of high-risk proliferative diabetic retinopathy in patients with type I diabetes will reduce the risk of severe visual loss. ETDRS analyses do indicate that for patients with type II diabetes, it is especially important to consider scatter photocoagulation at the time of the development of severe nonproliferative or early proliferative retinopathy.

Reversible loss of light perception after vitreoretinal surgery

PURPOSE

We studied reversible loss of light perception after vitreoretinal surgery to show that functional vision can return in some patients.

METHODS

We reviewed the medical records of seven patients who had postoperative reversible loss of light perception in the eye that underwent vitreoretinal surgery. Differences in the postoperative courses and interventions were studied.

RESULTS

Five of the seven patients had diabetes mellitus but none had hypertension. The indications for vitreoretinal surgery were severe proliferative diabetic retinopathy in five patients and retinal detachment with advanced proliferative vitreoretinopathy in two patients. Seven patients had reversible loss of light perception within the first three postoperative days. Six of the seven patients had an intraocular pressure greater than 26 mm Hg at the time the eye had no light perception. Decreasing the intraocular pressure was associated with return of light perception in five of seven patients. Return of useful vision was gradual. Four of seven patients had a visual acuity of 20/400 or better one month after surgery, and all seven had a visual acuity of 20/400 or better three months after surgery. Visual acuity in four eyes improved further to 20/70 or better at six months or more after surgery.

CONCLUSION

Reversible loss of light perception after vitreoretinal surgery does occur in some patients. Monitoring vision and intraocular pressure is important because prompt treatment may assist in the recovery of functional vision.

Retinal and choroidal responses to panretinal photocoagulation: an ultrastructural perspective

BACKGROUND

There have been few histological or ultrastructural studies of the outer retina and choriocapillaris following panretinal photocoagulation therapy. This investigation examines the long-term morphological effects of panretinal photocoagulation in two patients with type II diabetes who had received laser treatment more than 6 months prior to death.

METHODS

Regions of retina and choroid from each patient were fixed in 2.5% glutaraldehyde, dissected out and examined using light microscopy and scanning and transmission electron microscopy.

RESULTS

After removing the neural retina, scanning electron microscopy of non-photocoagulated areas of the eye cups revealed normal cobblestone-like retinal pigment epithelial (RPE) cells. Regions with laser scars showed little RPE infiltration into the scar area, although large rounded cells often appeared in isolation within these areas. Sections of the retina and choroid in burn regions showed a complete absence of the outer nuclear layer and photoreceptor cells, with the inner retinal layers lying in close apposition to Bruch's membrane. Non-photocoagulated regions of the retina and choroid appeared normal in terms of both cell number and cell distribution. The RPE layer was absent within burn scars but many RPE-like cells appeared markedly hypertrophic at the edges of these regions. Bruch's membrane always remained intact, although the underlying choriocapillaris was clearly disrupted at the point of photocoagulation burns, appearing largely fibrosed and non-perfused. Occasional choroidal capillaries occurring in this region were typically small in profile and had plump non-fenestrated endothelium.

CONCLUSIONS

This study outlines retinal and choroidal cell responses to panretinal photocoagulation in diabetic patients and demonstrates an apparent reduction in the capacity of these tissues to repair laser damage.

[The relationship between diabetic retinopathy and cataract extraction with intraocular lens implantation in diabetics]

47 diabetics (71 eyes) having undergone cataract extraction with intraocular lens (IOL) implantation were examined and followed up. The results show that there is significant difference in the last post-operative visual acuities between the diabetic group and non-diabetic group (P < 0.01). The main cause affecting the post-operative visual acuities of the diabetics is diabetic proliferative retinopathy (P < 0.001). There is no significant difference in the post-operative visual acuities between diabetic group with or without simple diabetic retinopathy and non-diabetic group (P > 0.05). The intra- and post-operative complications in the diabetic and non-diabetic group were also investigated and there was no significant difference. IOL implantation should be guarded for diabetics with proliferative retinopathy especially when complicated with maculopathy.

[Endotamponade with silicon oil in severe proliferative retinopathy with attached retina]

Silicone oil as endotamponade in cases with attached retina is only indicated in a few very selected cases. These are cases with a high risk of intravitreal hemorrhage and a need for quick visual rehabilitation. We examined 23 patients, who had undergone pars plana vitrectomy and silicone oil filling. All patients were diabetics with proliferative retinopathy and recurrent intravitreal hemorrhage. In 14 cases it was the only eye; 11 eyes previously had a vitrectomy. We analyzed these cases for visual acuity, rubeosis, bleeding tendency, reproliferations, cataract development and glaucoma. The follow-up time was 32 months. In 22 of 23 eyes quick visual rehabilitation was achieved, and the patients had at least ambulatory vision within the first week. In one case poor visual acuity was due to exudative maculopathy. No relevant bleeding occurred. In 14 of 16 phacic patients we observed a cataract. Seven patients developed glaucoma, which was due to neovascularization in 5 cases. It was successfully treated in all cases and no visual loss occurred. In 5 cases we observed a peripheral traction retinal detachment, in one case a traction retinal detachment at the posterior pole. In selected cases silicone oil can prevent recurrent intravitreal hemorrhage, allowing rapid visual recovery. Considering the complications, the silicone oil should be removed as soon as possible.

Membrane delaminating wedge

Iatrogenic retinal tears may complicate procedures to treat proliferative vitreoretinal diseases. To decrease the risk of this complication, we developed a new instrument, the membrane delamination wedge, that allows the surgeon to separate the proliferative membranes from the retina effectively and safely.

[Long-term outcome after silicone oil removal]

In order to reduce the incidence of postoperative complications in silicone-filled eyes, many authors recommend that silicone oil should be removed from the eye as soon as a stable retinal situation is achieved. Even in the eyes with completely attached retina and a clinically stable situation there is a risk of retinal redetachment and other complications after silicone oil removal. In a retrospective study we analyzed 324 cases after silicone oil removal regarding the postoperative redetachment rate and risk of complications from this procedure. The indication for primary surgery was retinal detachment with PVR in 167 (51.5%) cases, proliferative diabetic retinopathy in 87 cases (26.8%), complications of penetrating ocular injuries in 48 cases (14.8%), giant tear retinal detachment in 9 cases (2.7%) and retinal detachment with a central hole in 13 cases (4%). At the time of silicone oil removal retina was completely attached in 277 eyes. Local retinal redetachment central to the encircling band existed in 47 eyes at the time of silicone removal. Follow-up time ranged from 6-63 months. Silicone oil removal was combined with a cataract operation in 42 cases (12.9%), penetrating keratoplasty in 9 cases (2.8%) and membrane peeling in 54 eyes (16.7). In the postoperative period the retina detached in 39 (12%) eyes. In the eyes with preoperatively completely attached retinas, redetachment occurred in 23 eyes (8%), whereas in the group of eyes with an unstable preoperative retinal situation, the retina redetached in 16 eyes (34%). The duration of the silicone oil tamponade had no effect on the redetachment rate. In the group of eyes with an unstable preoperative retinal situation, preoperative laser photocoagulation at the cerelage buckle, as well as central to the local detachment, reduced the incidence of redetachment after silicone oil removal significantly (25% vs. 53%). In the group of eyes with a preoperatively stable retinal situation, this effect was not significant. Our results show that in eyes with completely attached retinas, the risk of complications and redetachment after silicone oil removal is relatively low. In selected cases, even in eyes with incompletely attached retinas, silicone oil could be removed. Nevertheless, a relatively high risk of postoperative complications has to be taken into consideration. In eyes with an incompletely attached retina, preoperative laser photocoagulation at the cerclage buckle, as well as central to the local redetachment significantly reduced the incidence of redetachment after silicone oil removal.

[Retinopathy and perinatal outcome in diabetic pregnancy]

Sixty patients with diabetes mellitus (DM) antedated pregnancy were enrolled; seven had proliferative retinopathy, 13 had simple retinopathy, and 40 were intact. Diet and/or insulin was prescribed to adjust their glucose control at fasting to < 100 mg/dl, as well as at 2 hours postprandial to < 120 mg/dl. Glycohemoglobin (Hemoglobin A1c) levels ranged between 5.4% and 6.4% in the third trimester in three groups. Incidences of pregnancy complications (toxemia, hydramnios, urinary tract infection and cesarean section) and neonatal complications (low Apgar score, hypoglycemia, jaundice, polycythemia, respiratory distress syndrome and anomaly) did not differ significantly with the grade of retinopathy. Compared with the intact group, the duration of DM was significantly longer in the retinopathy groups and the incidence of fetal distress was significantly higher in the proliferative retinopathy group. In ten of 60 patients (16.7%) the grade of retinopathy progressed during pregnancy. In four patients photocoagulation was performed for neovascularization, and proved to be effective. There was a tendency for those whose retinopathy progressed to the proliferative stage during pregnancy to have larger decreases in glycohemoglobin and for their retinopathy to worsen after delivery. With tight maternal glucose control and intensive fetal surveillance, we obtained good perinatal outcome in pregnancies with diabetic retinopathy, as compared to diabetic pregnancy without diabetic microangiopathy. Careful and frequent monitoring of retinal changes should be required during pregnancy and the postpartum period.

[Panretinal photocoagulation with argon laser--material from the Eye Clinic in Wroclaw in 1991-1994]

PURPOSE

To evaluate the results of PRK performed between 1990 and 1994 in Wroclaw University Eye Clinic.

MATERIALS AND METHODS

PRK was performed in 630 eyes with: (1) PDR--451 immediately treated eyes (moderate PDR--184 eyes, with "high-risk" characteristics--227 eyes, PDR advanced--after cryopexion--40 eyes); (2) severe NPDR--119 eyes (with PDR in fellow eye or with ME) and (3) less severe DR--60 eyes treated with immediate or delayed, full or mild scatter coagulation (with macular edema, both eye moderate NPDR, other systemic risk factors). Follow-up treatment: Additional scatter or local photocoagulation was performed in 34 cases increasing activity of neovascularisation or increase in frequency/extend of vitreous hemorrhage.

RESULTS

In a period 3 to 36 months of follow-up (mean period = 25 months) in the group of 451 eyes with PDR 28.2% of eyes showed visual improvement, 48.3% of eyes showed no change and 23.5% of eyes worsened. In the group of 119 eyes with severe NPRD 75.6% showed visual improvement and 24.4% showed no change. In the group of 60 eyes with less severe DR 27.8% showed improvement, 36.7% showed no change and 35.5% worsened.

CONCLUSION

Our results are relatively good and in agreement with other studies.

[Proliferative retinopathy--pathogenesis and classification from the aspect if indications for laser photocoagulation, and its incidence in materials of the Eye Clinic in Wroclaw]

PURPOSE

To evaluate the incidence of different stages of DR, especelly the incidence of the PDR, in the materials of the Wroclaw University Eye Clinic.

MATERIALS AND METHODS

We performed our study from 1991 to 1994 in 478 subjects with diabetes mellitus--84 with diabetes type I and 394 with diabetes type II. In the older-onset group there were 64% of patients taking insulin. Mean age of the group was 61 years and mean period of duration of diabetes was 16 years. The methods of ophthalmological examination included stereoophthalmoscopy and fluorescein angiography.

RESULTS

We found in 930 examined eyes: RD absent--13 eyes, early NPDR--138 eyes, moderate NPDR--32 eyes, moderately severe NPRD--60 eyes, severe NPDR (preproliferative)--136 eyes, moderate PDR--186 eyes, "high risk" characteristics PDR--227 eyes and advanced PDR--138 eyes.

CONCLUSION

The study indicated in our materials the incidence of PDR and its severity very high.

A case of severe diabetic retinopathy in pregnancy

Proliferative retinopathy is a recognized long-term complication of diabetes and the commonest cause of blindness in young people. There is, however, some uncertainty regarding counselling given on the continuation of pregnancy when it is complicated by retinopathy. This case is used to highlight this difficulty and to discuss management based on literature review.

[Incidence of and treatment outcome for diabetic maculopathy--material from the Eye Clinic in Wrocçaw in 1991-1994]

PURPOSE

To evaluate the incidence of ME, its characteristics, and results of its treatment with laser coagulation.

MATERIAL AND METHODS

In the analysed group there were 478 subjects with diabetes mellitus--84 with a diagnosis before 30 years of age and 394 with a diagnosis at 30 years of age or older. In the older-onset group there were 64% taking insulin. Mean age of the group was 61 years and mean period of duration of diabetes was 16 years. The methods of ophthalmological examination included stereoophthalmoscopy and fluorescein angiography. In 845 examined eyes there were 832 eyes with mild-to-severe nonproliferative and moderate-to-high risk proliferative diabetic retinopathy.

RESULTS

The incidence of macular edema was 81.6%. These data suggest high incidence of macular edema and its high severity (V < 0.2 = 47%) over the 15-years period of duration of diabetes. Treatment included focal coagulation, macular grid and PRK performed with argon laser.

CONCLUSION

The results of laser coagulation demonstrated that focal photocoagulation was effective in reducing the risk of moderate visual loss. When macular edema was more severe, macular grid before scatter (panretinal) photocoagulation for proliferative retinopathy decreased the frequency of persistent ME.

Focal photocoagulation treatment of diabetic macular edema. Relationship of treatment effect to fluorescein angiographic and other retinal characteristics at baseline: ETDRS report no. 19. Early Treatment Diabetic Retinopathy Study Research Group

OBJECTIVE

To determine whether the efficacy of photocoagulation treatment of diabetic macular edema may be influenced by degree of capillary closure, severity or source of fluorescein leakage, extent of retinal edema, presence of cystoid changes, or severity of hard exudates.

PATIENTS

Patients with mild to moderate nonproliferative diabetic retinopathy and macular edema definitely or questionably involving the center of the macula.

DESIGN

One eye of each patient was assigned to early photocoagulation; the other was assigned to deferral of photocoagulation, with follow-up visits scheduled every 4 months and photocoagulation to be carried out promptly if high-risk proliferative retinopathy developed. In this report, the beneficial effect of photocoagulation was examined in subgroups defined by severity of the characteristics specified above.

RESULTS

We found no subgroup in which eyes that were assigned to immediate focal treatment had a less favorable visual acuity outcome than those that were assigned to deferral (ie, no qualitative interaction).

CONCLUSIONS

Focal photocoagulation should be considered for eyes with clinically significant macular edema, particularly when the center of the macula is involved or imminently threatened. Trends for treatment effect to be less in eyes with less extensive retinal thickening and less thickening at the center of the macula support our previous recommendation that, for such eyes, an initial period of close observation may be preferable to immediate treatment, particularly when most of the leakage to be treated arises close to the center of the macula, increasing the risk of damage to it from direct treatment or subsequent migration of treatment scars.

Dye laser treatment in proliferative diabetic retinopathy and maculopathy

The aim of this study was to compare the efficacy of various dye laser wavelengths in different forms of retinopathies. The study material consisted of 292 eyes of 210 diabetic retinopathy patients treated with dye laser photocoagulation between 1990 and 1992. All the patients were followed for at least 6 months after photocoagulation. Non-proliferative changes (maculopathy and/or preproliferative retinopathy) were present in 135 (46.3%) and proliferative retinopathy in 157 (53.7%) of the eyes undergoing photocoagulation. Of the 157 eyes with proliferative retinopathy, 60 (20.5%) had disc neovascularization, 71 (24.3%) had retinal neovascularization and 26 (8.9%) had retinitis proliferans. Yellow dye laser (580 nm) was applied in 92 (31.5%) eyes, red dye laser (630 nm) in 120 (41.1%) eyes and both yellow and red dye lasers in 80 (27.4%) eyes. There was no significant difference between the different wavelength groups with regard to visual acuity changes before and after treatment (p < 0.01). Overall, the visual acuity was maintained in 56.2% and improved in 25.0% of the eyes. After panretinal photocoagulation, disc neovascularization regressed partially or completely in 47 (78.3%) of the eyes. There was no significant difference among the various laser wavelengths with regard to treatment efficacy judged by the disappearance or regression of disc neovascularization (p < 0.01). All retinal neovascularizations regressed completely with laser treatment, but in 7 eyes (9.9%) new retinal neovascularizations in previously untreated areas developed. Dye laser has not resulted in any complications. It requires lower power settings compared to argon laser and thus facilitates photocoagulation. Another advantage of dye laser is the ability to use yellow and red wavelengths sequentially.

[Electroretinogram before and after panretinal photocoagulation in diabetic retinopathy]

Visual acuity and visual fields with the Goldmann perimeter were measured, and electroretinograms (ERGs) were recorded in 25 eyes of 16 patients with pre-proliferative diabetic retinopathy who underwent panretinal photocoagulation (PRP) before PRP and one, three, and six months after PRP. ERGs were recorded with the use of a corneal contact lens electrode. With Ganzfeld stimulation, stimulating flashes were given from the dimmest flash to the maximum 2.0 J white flash, using neutral density filters. Visual acuity was significantly decreased more than two lines and visual field defects by isopter I/4 were found one month after PRP. ERGs showed a significant prolongation of a-and b-wave peak latency and a significant reduction of wave amplitude in both waves. From the analysis of the b-wave amplitude-stimulus intensity function, using the Naka-Rushton equation, the sensitivity parameter (K) was increased one month after PRP in comparison to before PRP. Namely, threshold sensitivity was attenuated. The sensitivity recovered three months after PRP. By examining two factors (i.e., the maximum amplitude of the b-wave and the sensitivity parameter (K)), within the range of the Naka-Rushton equation, this result showed that PRP reduced the sensitivity of the retina quantitatively.

Early vitrectomy and endolaser photocoagulation in patients with type I diabetes with severe vitreous hemorrhage

PURPOSE

To determine if adjunctive endolaser photocoagulation has further improved the outcome of early vitrectomy for severe vitreous hemorrhage in young patients with type I insulin-dependent diabetes.

METHOD

The authors reviewed clinical records and fundus photographs of all primary diabetic vitrectomies performed at the Yale Eye Center between July 1986 and June 1993. Only young patients with type I diabetes who underwent vitrectomy within 6 months of vitreous hemorrhage were included.

RESULTS

Of 197 vitrectomies for diabetic retinopathy, 12 eyes of ten patients met the Diabetic Retinopathy Vitrectomy Study Group criteria. Patients ranged in age from 24 to 29 years (mean, 27.3 years) and had 11 to 21 years (mean, 17.2 years) of history of diabetes. Preoperative visual acuity was 5/200 in seven eyes, 2/200 in three eyes, hand motions in one eye, and light perception in one eye. The duration of vitreous hemorrhage was approximately 1 month in two eyes, 1 to 3 months in five eyes, and 3 to 6 months in five eyes. Neovascularization was documented in 12/12 eyes. Preoperatively, all patients had received panretinal photocoagulation with 1937 to 5328 burns (mean, 4126). Postoperative follow-up ranged from 12 to 38 months (mean, 24.6 months). Best-corrected postoperative visual acuity was 20/40 or better in 7 eyes (58.33%) and 20/70 or better in 11 eyes (91.66%). Neovascularization involuted in 11/12 eyes and remained so till the last follow-up.

CONCLUSION

Patients with type I diabetes with severe vitreous hemorrhage benefit from early endolaser photocoagulation combined with current vitrectomy techniques. The authors' findings are consistent with those of the Diabetic Retinopathy Vitrectomy Study Group, and patients can expect both improved visual acuity and anatomic success.

Automatic exposure control in retinal laser therapy

Retinal laser spots are often over- or underexposed due to inhomogeneities of fundus pigmentation or variations in the radiation power impinging on the retina. We developed a method to control the exposure time of each individual spot of retinal laser photocoagulation in real time. The laser light reflected from the spot area is recorded by a detector. The intensity of this light increases during the exposure due to bleaching of the retinal pigment. If the reflected light reaches a predefined level, the laser apparatus is immediately stopped by a computer, which controls the whole process. The procedure was tested in enucleated porcine eyes. After verification of the proper function, a pilot study in a small collective of 19 patients (20 eyes, 25 sessions) with clear optical media was performed. In all cases, the apparatus worked safely. Visible indications for overexposed spots, particularly bleeding in extreme cases, did not occur. However, about 2%-5% of the spots were underexposed, mainly due to eye movements of the patient during the coagulation. Large variations in the automatically controlled exposure time confirm the difficulty in properly adjusting this parameter without such an automatic device. However, to be applicable to patients with opaque optical media, the method must be improved.

How much blame can be placed on laser photocoagulation for failure to attain driving standards?

One hundred consecutive patients who underwent bilateral pan-retinal photocoagulation (PRP) for proliferative diabetic retinopathy were assessed in accordance with the UK Driver and Vehicle Licensing Agency (DVLA) guidelines. Visual acuity was documented, and visual fields were assessed using the Esterman test. Among the 30% of patients who failed to reach the visual standards required for a driving licence, three groups were identified: those who failed to attain either the required binocular visual acuity (n = 4), or visual fields (n = 9), or both (n = 17). Previous studies reveal a large variation in DVLA field test failure following PRP treatment for proliferative diabetic retinopathy. Our results show a 19% failure rate solely attributable to treatment, which is at the lower end of previously reported studies (20-80%). The reasons for this discrepancy are discussed. We conclude that modern treatment procedures for proliferative diabetic retinopathy may be undertaken with the knowledge that in the majority of cases a patient's driving licence is unlikely to be revoked.

Continuous wave Nd:YAG laser photocoagulation in proliferative diabetic retinopathy

AIMS

The therapeutic efficacy of the continuous wave (CW) Nd:YAG laser (working in the free running mode) was investigated in proliferative diabetic retinopathy (PDR) comparing it with a conventional laser source such as the krypton laser.

METHODS

Twenty four eyes of 12 patients affected with bilateral PDR were included and divided in two groups. The right eyes were treated with a red krypton laser and the left eyes with a CW Nd:YAG laser.

RESULTS

Three months after krypton photocoagulation 10 eyes showed a reduction or a complete regression of PDR and two eyes were unchanged. In the CW Nd:YAG laser group no eyes showed any regression of new vessels, in seven eyes the angiographic features were unchanged, and in five eyes they worsened. All the eyes of the second group underwent retreatment with the krypton laser after 3 or 6 months. After a mean follow up of 13 months all eyes in the krypton group showed a reduction or complete regression of PDR; in the retreated group 10 eyes improved and two were unchanged.

CONCLUSIONS

The statistical analysis showed a highly significant difference (p = 0.001) between krypton and CW Nd:YAG laser which indicated the lack of efficacy of the latter in the treatment of PDR. In the krypton laser group no significant difference (p = 0.05) after the retreatment was found confirming the efficacy of this treatment.