Symptomatic posterior vitreous detachment and the incidence of delayed retinal breaks: case series and meta-analysis

PURPOSE

To establish the necessity for an early follow-up examination after an initial funduscopic examination with negative results for patients with acute, symptomatic posterior vitreous detachment (PVD).

DESIGN

Retrospective case-control study and meta-analysis.

METHODS

Records were reviewed of patients seeking treatment over a 4.5-year period who were diagnosed with an acute, symptomatic PVD. A MEDLINE search to identify all published observational case studies reporting vitreoretinal pathologic features after acute, symptomatic PVD.

RESULTS

The incidence of retinal tears in eyes with a symptomatic PVD was 8.2%. The overall rate of retinal break in the meta-analysis portion of the study was 21.7%. In total, 1.8% of patients had retinal tears that were not seen on initial examination. Of the 29 patients with delayed-onset retinal breaks, 24 (82.8%) had at least one of the following: vitreous hemorrhage at initial examination, hemorrhage in the peripheral retina at initial examination, or new symptoms.

CONCLUSIONS

If the results of an initial examination of a patient with an acute, symptomatic PVD are negative for retinal tears, the necessity of early follow-up may be best determined by the presence of pigmented cells in the vitreous, vitreous hemorrhage, or retinal hemorrhage. Most patients with symptomatic PVD may not need an early follow-up examination.

Vitreopapillary traction: Cost-effective diagnosis by optical coherence tomography

CASE REPORTS

A prospective, noncomparative, observational case series. Three patients, aged 76 to 81, all referred to subspecialty services for evaluation of optic disc elevation, and all were found to have optic disc (vitreopapillary) traction as verified by optical coherence tomography.

COMMENTS

Vitreopapillary traction is a recently recognized syndrome characterized by incomplete posterior vitreous detachment. The use of optical coherence tomography is helpful in the diagnosis of this syndrome, preventing many costly, unwarranted evaluations.

Visualization of vitreomacular tractions with en face optical coherence tomography

BACKGROUND

In vitreomacular traction syndrome, an incomplete vitreous detachment with persistent vitreous traction on the macula is present. This condition may determine formation of epiretinal membranes, macular puckering, macular oedema, and traction macular detachment. Recently introduced en face optical coherence tomography (OCT) provides not only longitudinal B-scan but also coronal C-scan images of the retina.

METHODS

Fifteen eyes of 11 non-diabetic patients presenting vitreomacular traction syndrome have been evaluated with en face OCT (OTI, Toronto, Ontario, Canada).

RESULTS

In 12 eyes, cystoid macular oedema was detectable at fundus examination and was associated with a broad-based adherence of the posterior hyaloid to the macula. In three eyes, foveal detachment appeared to be associated with focal foveal vitreoretinal traction. In all eyes, the lateral extent of the hyaloidal tractions on the macula was clearly detectable at coronal C-scan. They appeared as sigmoid hyper-reflective bands in the hyporeflective vitreous chamber. Overlay of C-scans on red-free confocal images allowed the visualization of the edges of the adherences in relation to the structures of the posterior pole.

CONCLUSIONS

The C-scan images allowed clear visualization of the total extension of the posterior vitreomacular adherences and their relationships with the vascular arcades, the optic disc, and the fovea.

[The incidence of retinal tears in patients with posterior vitreous detachment]

Posterior vitreous detachment (PVD) is a common finding in older patients, characterized by detachment of the posterior hyaloid membrane (PHM) from the retinal surface. The detachment of PHM normally occurs without complications, however, one has to be aware that retinal tear is its most common complication.

AIM

The aim of the study was to determine the incidence of retinal tears in eyes with PVD.

PATIENTS AND METHODS

A series of 40 patients (70 eyes) with PVD were included in this retrospective study. Eyes with a history of ocular trauma, surgery or intraocular inflammation were excluded. Patient charts were reviewed to collect the following information: age, sex, profession, type and duration of symptoms, best corrected visual acuity, refractive status, prior ocular disease, coincidental retinal pathology-lattice degeneration, number, type and location of retinal tears and treatment. Statistical analysis was done with the SPSS 11.0.3 software (SPSS Inc., USA). Besides descriptive statistics, Student's t-test and chi2-test were used.

RESULTS

Among all study eyes with PVD, 34 (48.6%) were myopic, 24 (34.3%) hypermetropic and 12 (17.1%) emetropic; statistical analysis showed a significant difference (chi2 = 10.40, df=2, p < 0.01). In 6 (8.6%) eyes with PVD lattice malignant degeneration of peripheral retinal was diagnosed. Thorough examination of the fundus periphery revealed 16 (22.8%) eyes with PVD were found to have retinal tears, 11 (15.7%) had only one retinal tear and 5 (7.1%) two retinal tears. All retinal tears were treated with argon laser photocoagulation. Superotemporal eye quadrant was the most common localization of retinal tears (56.25%).

CONCLUSION

These results indicate that thorough fundus periphery examination should be done in all patients with PVD because it can cause rather rarely though retinal tears that represent a potentially sight threatening condition.

Spontaneous resolution of macular microhole

PURPOSE

To report a case of spontaneous resolution of macular microhole.

DESIGN

Observational case report.

METHODS

Clinical examination and optical coherence tomography (OCT) evaluation of a patient who experienced spontaneous resolution of a macular microhole.

RESULTS

A 62-year-old woman with decreased vision was found to have a full-thickness macular microhole with posterior vitreous detachment and an operculum on fundus biomicroscopy and OCT. Spontaneous resolution of the microhole was documented on clinical examination and OCT 3 weeks after the examination when the patient returned with improved vision and a small central floater.

CONCLUSIONS

Macular microholes can be associated with posterior vitreous detachment. Spontaneous closure of macular microholes can occur.

Clinical features and surgical management of retinal detachment secondary to round retinal holes

AIMS

The majority of rhegmatogenous retinal detachments result from pathological posterior vitreous detachment (PVD) and secondary horseshoe or giant retinal tears. Retinal detachment without PVD is usually associated with either retinal dialysis or round retinal holes. This study characterises the features, surgical outcome, and incidence of bilateral involvement of detachment associated with round retinal holes.

METHODS

In all, 110 retinal detachments from 96 consecutive patients with retinal detachment secondary to round retinal holes were studied. Analysis of patient age, sex, refraction, preoperative visual acuity, presented symptoms, position and extent of detachment, number and distribution of holes present, posterior hyaloid membrane status, surgical management, outcome of surgery, and postoperative visual acuity were studied.

RESULTS

The mean age for patients was 34 years with a marked female preponderance (64%) and myopia (83%). The posterior hyaloid membrane remained attached in 95 eyes (86%). In all, 45% patients had bilateral pathology, of which 33% had 'mirror image' distribution. Detachments were predominantly shallow (93%) and slow in progression (17%). A total of 100 detachments were repaired with cryotherapy and scleral buckling, eight with cryotherapy alone, and one with laser retinopexy. In all, 99% detachments were successfully reattached with a single procedure. The mean follow-up period was 2 years. There were no instances of redetachment.

CONCLUSIONS

Round hole detachments are slowly evolving detachments with attached vitreous gel in young, predominantly female myopes. Examination of the fellow eye should be mandatory as there is a high incidence of bilateral pathology. Scleral buckling procedures remained highly effective in this selected group of patients.

FREQUENCY AND ASSOCIATIONS OF A TAUT THICKENED POSTERIOR HYALOID, PARTIAL VITREOMACULAR SEPARATION, AND SUBRETINAL FLUID IN PATIENTS WITH DIABETIC MACULAR EDEMA

PURPOSE

To determine prospectively among patients with diabetic macular edema (DME) the frequency of a clinically evident taut thickened posterior hyaloid (TTPH), optical coherence tomography (OCT) signs suggestive of partial vitreomacular separation (PVMS), and OCT evidence of subretinal fluid (SRF) and to investigate for associations between these findings.

METHODS

In a prospective case series, patients with DME despite previous laser treatment were examined for the presence of a TTPH. OCT was performed to investigate for PVMS and SRF.

RESULTS

One hundred forty patients and eyes were included in the study. A TTPH was present in six patients (4%). PVMS was present in 14 (10%) of 140 patients with DME, of whom 5 also had a TTPH. SRF was present in 15 (11%) of 140 patients, of whom 4 had TTPH. OCT showed that 66% of patients with SRF and DME had neither a clinical TTPH nor partial posterior hyaloid separation.

CONCLUSION

A TTPH was found in 4% of subjects with DME. Partial posterior hyaloid separation and SRF may be found in patients who do not have a TTPH. SRF in patients with DME may not be tractional.

Rapid Spontaneous Resolution of Vitreomacular Traction Syndrome Documented by Optical Coherence Tomography

A 48-year-old woman presented with a 2-week history of metamorphopsia and reduced vision in her left eye. Visual acuity was 20/30 OS. Slit lamp biomicroscopy fundus evaluation revealed a dull foveal reflex. Optical coherence tomography (OCT) showed attachment of the posterior hyaloid to the macula and significant macular elevation. One month after presentation, visual complaints disappeared. OCT revealed complete posterior vitreous detachment and normal foveal thickness. Although rare, rapid spontaneous resolution of vitreomacular traction syndrome can occur. OCT is a helpful diagnostic tool for following these patients.

Tractional cystoid macular edema: a subtle variant of the vitreomacular traction syndrome

PURPOSE

To describe clinical characteristics and treatment outcomes in a series of patients with tractional cystoid macular edema, a subtle variant of the vitreomacular traction syndrome.

DESIGN

Retrospective, uncontrolled, observational, and interventional case series.

METHODS

PATIENT POPULATION

Ten consecutive patients (11 eyes) with multicystoid foveolar thickening caused by localized perifoveal vitreous detachment.

EXPERIMENTAL PROCEDURES

Slit-lamp biomicroscopy and fluorescein angiography; confirmation of vitreomacular relationship with B-scan ultrasonography, optical coherence tomography (OCT), or both. Vitrectomy with peeling of posterior hyaloid in 8 eyes with pretreatment visual acuity <or=20/60.

MAIN OUTCOME MEASURES

Visual acuity and resolution of cystoid macular edema at final follow-up.

RESULTS

The median age of symptom onset was 71 years (range 48-81 years). Shallow perifoveal vitreous detachment was detectable on biomicroscopy in 8 of 11 eyes (73%) and with ultrasound and OCT in all eyes. Fluorescein angiography revealed no leakage from perifoveal capillaries in 8 eyes (73%). After a mean postoperative follow-up of 26.0 months (range 3-84 months), the final visual acuity had improved by 2 or more Snellen lines and measured 20/40 or better in 8 (100%) of 8 operated eyes. Cystoid foveal thickening resolved in all operated eyes.

CONCLUSION

Subtle, localized perifoveal vitreous detachment may cause anterior traction on the foveola, resulting in multicystoid foveal thickening without macular hole formation or capillary leakage. OCT and ultrasound imaging are useful in detecting the detached posterior hyaloid when clinically invisible. Foveal thickening resolves and visual acuity typically improves after the relief of vitreofoveolar traction.

Optical coherence tomography assessment of the vitreoretinal relationship in diabetic macular edema

PURPOSE

To study the vitreoretinal relationship in diabetic patients with and without diabetic macular edema (DME) using optical coherence tomography.

DESIGN

Retrospective case-control study.

METHODS

setting: Institutional practice. patients: Thirty-five consecutive diabetic patients (49 eyes) with DME and 35 sex- and age-matched diabetic control patients without DME (49 eyes). observation procedure: All patients had Early Treatment Diabetic Retinopathy Study visual acuity measurement and biomicroscopic examination of the vitreoretinal interface. OCT was performed to obtain cross-sectional images of the vitreoretinal interface of the macular region. Posterior vitreous detachment (PVD) was staged from 0 to 3 as follows: stage 0: absence of PVD; stage 1: perifoveolar PVD with foveolar attachment; stage 2: incomplete PVD with residual attachment to the optic nerve; and stage 3: complete PVD. Retinal thickness was measured using OCT mapping software in all cases. main outcome measures: Prevalence of the different PVD stages in both groups of eyes.

RESULTS

The mean age of the patients was 60 years in both groups. Of the eyes with macular edema, 19 (38.8%) were stage 0, 26 (53.0%) stage 1, 1 (2.0%) was stage 2, and 3 (6.2%) were stage 3. In eyes without DME, the corresponding figures were, respectively, 34 (69.4%), 11 (22.4%), 1 (2.0%), and 3 (6.2%). The prevalence of perifoveolar PVD with foveolar attachment was significantly higher in the group of eyes with DME (P =.006).

CONCLUSIONS

These results show the high prevalence of perifoveolar PVD with foveolar attachment in diabetic patients with macular edema. Even though PVD is not the main factor involved in the pathogenesis of DME, perifoveolar PVD may have a role in the development of this complication.

Intravitreal triamcinolone staining observation of residual undetached cortical vitreous after posterior vitreous detachment

AIMS

To study the pattern of residual undetached cortical vitreous (RCV) after posterior vitreous detachment (PVD) in eyes with rhegmatogenous retinal detachment (RRD) and to examine the relationship between RCV and the development of epiretinal membrane (ERM).

METHODS

A prospective study was conducted in 33 consecutive patients with clinically evident PVD who underwent pars plana vitrectomy for RRD. During vitrectomy, triamcinolone acetonide (0.2 cm(3), 10 mg/cm(3)) was applied to stain the RCV. The pattern of the staining were recorded. The formation of postoperative ERM was correlated with the staining pattern of RCV. Each case was followed for at least 6 months.

RESULTS

In all, 23 of the 33 patients had RCV of variable size, with a single stain patch observed in 13 patients and multiple patches in seven patients. Large circumferential areas of staining at the mid-periphery were noted in three patients. A total of 10 cases had staining over the fovea and five patients had staining over the disc. ERM developed in seven patients during follow-up. None corresponded to RCV.

CONCLUSION

RCV is common in eyes with PVD and RRD. The macula and disc area are the most frequent locations for these vitreous islands. The relationship between RCV and ERM remains to be investigated.

Symptoms and findings predictive for the development of new retinal breaks

OBJECTIVE

To validate the conclusion of our previous prospective study of 250 patients with isolated posterior vitreous detachment: follow-up visits are only necessary if patients mention symptoms of flashes in combination with multiple floaters or a curtain or cloud at the initial examination, or an increase in number of floaters after the initial examination.

METHODS

Prospective study of 270 consecutive patients with symptomatic isolated posterior vitreous detachment. All patients completed a questionnaire detailing their symptoms and had a full eye examination at the initial examination and at follow-up visits. Logistic regression with backward elimination was used for statistical analysis. We also performed pooled analysis of our previous and present study data.

RESULTS

New retinal breaks developed in 10 patients (3.7%). Multiple floaters, a curtain or cloud, hemorrhages (retinal or vitreous) at the initial examination, and an increase in the number of floaters after the initial examination were found to be predictive factors for the development of new retinal breaks. These factors were also the only significant predictors after pooled analysis of both studies (520 patients, 23 breaks).

CONCLUSIONS

We assume we can formulate a safe policy for scheduling patients with isolated posterior vitreous detachment: only patients with multiple floaters, a curtain or cloud, or hemorrhages (retinal or vitreous) at the initial examination should be scheduled for reexamination. All other patients should return only if the number of floaters increases.

Gaze-evoked amaurosis from vitreopapillary traction

PURPOSE

We report four patients with gaze-evoked amaurosis attributable to incomplete posterior vitreous detachment and ensuing vitreopapillary traction. We present these cases to illustrate and extend the spectrum of vitreopapillary syndromes and to draw attention to vitreopapillary traction and its expected manifestations in both optic disk appearance and optic nerve and retinal function.

DESIGN

This is a retrospective observational case series culled from tertiary neuro-ophthalmology practice.

METHODS

Patients were evaluated with direct and indirect ophthalmoscopy, Hruby (precorneal) lens, three-mirror Goldmann contact lens, macular contact lens, formal perimetry, fundus photography, fluorescein angiography, and orbital ultrasound.

RESULTS

Four patients with gaze-evoked amaurosis had disk edema associated with a partial posterior vitreous separation. These patients were young and had atypical posterior vitreous detachments characterized by persisting vitreopapillary attachments.

CONCLUSIONS

Gaze-evoked amaurosis is a rare visual obscuration precipitated by changes in volitional gaze, usually associated with an underlying orbital mass. We extend its etiologies to implicate the vitreous through traction expressed at the optic disk. In our cases, vitreopapillary traction elevated the nerve head and eye movements precipitated transient visual phosphenes followed by gaze-evoked amaurosis caused by traction transmitted from the vitreous to superficial nerve fibers of the retina and disk.

Perifoveal vitreous detachment and its macular complications

PURPOSE

To evaluate the vitreoretinal relationship in eyes with idiopathic macular disorders putatively caused by vitreomacular traction associated with early stages of age-related posterior vitreous detachment (PVD).

METHODS

Retrospective observational case series of 43 eyes of 40 patients diagnosed with one of several idiopathic vitreomacular conditions. Included patients had no biomicroscopic evidence for complete PVD on presentation and underwent a specific clinical assessment of the vitreoretinal relationship. Affected eyes were evaluated with slit-lamp biomicroscopy, B-scan ultrasonography, optical coherence tomography, and/or intraoperative examination of the posterior hyaloid.

RESULTS

By one or more examination techniques, 41 (95.3%) of the 43 study eyes had evidence of vitreous detachment from the perifoveal macular region and the remaining two eyes had complete PVD. When measurable, the size of the vitreomacular adhesion varied by diagnosis. Of 31 eyes with perifoveal vitreous detachment seen in follow-up, only three (9.7%) showed progression to complete PVD over an average preoperative or total follow-up period of 30.0 months (range, 2 to 237 months). Surgical or spontaneous separation of the residual vitreomacular adhesion in 16 eyes was followed in 15 (93.8%) by partial or complete resolution of the symptoms and signs of macular traction.

CONCLUSIONS

Age-related PVD appears to be an insidious, chronic event that begins in the perifoveal macula and evolves over a prolonged period of time prior to vitreopapillary separation. Though usually asymptomatic, its early (perifoveal) stages may be complicated by one of several macular pathologies, determined in part by the size of the residual vitreomacular adhesion.

Anomalous posterior vitreous detachment: a unifying concept in vitreo-retinal disease

Posterior vitreous detachment (PVD) is the consequence of changes in the macromolecular structure of gel vitreous that result in liquefaction, concurrent with alterations in the extracellular matrix at the vitro-retinal interface that allow the posterior vitreous cortex to detach from the internal limiting lamina of the retina. Gel liquefaction that exceeds the degree of vitro-retinal dehiscence results in anomalous PVD (APVD). APVD varies in its clinical manifestations depending upon where in the fundus vitreo-retinal adhesion is strongest. At the periphery, APVD results in retinal tears and detachments. In the macula, APVD causes vitreo-macular traction syndrome, results in vitreoeschisis with macular pucker or macular holes, or contributes to some cases of diabetic macular edema. At the optic disc and retina, APVD causes vitreo-papillary traction and promotes retinal and optic disc neovascularization. Unifying the spectrum of vitreo-retinal diseases into the conceptual frame-work of APVD underscores that to more effectively treat, and ultimately prevent, these disorders it is necessary to replicate the two components of an innocuous PVD, i.e., gel liquefaction and vitreo-retinal dehiscence. Pharmacologic vitreolysis is designed to mitigate against APVD by chemically breaking down vitreous macromolecules and weakening vitro-retinal adhesion to safely detach the posterior vitreous cortex. This would not only facilitate surgery, but if performed early in the natural history of disease, it should prevent progressive disease.

Time course of development of posterior vitreous detachment in the fellow eye after development in the first eye

PURPOSE

To determine when posterior vitreous detachment (PVD) develops in the fellow eye after development in the first eye.

DESIGN

Prospective, observational case series.

PARTICIPANTS

Fifty-one patients with acute unilateral PVD participated in the study.

METHODS

All patients underwent a comprehensive ocular examination, including a dynamic vitreous examination using biomicroscopy with and without a preset lens and retinal examination with scleral depression, every 3 months at least until PVD developed in the fellow eye.

RESULTS

Posterior vitreous detachment developed in 4 eyes (8%) within 6 months, 12 eyes (24%) within 1 year, 24 eyes (47%) within 18 months, 33 eyes (65%) within 2 years, 41 eyes (80%) within 30 months, and 46 eyes (90%) within 3 years. In 5 eyes (10%), PVD did not develop during the follow-up period of more than 3 years.

CONCLUSIONS

Posterior vitreous detachment develops frequently in the fellow eye from 6 months to 2 years after development in the first. These findings are useful for the management of patients with unilateral PVD.

Determination of the incidence and clinical characteristics of subsequent retinal tears following treatment of the acute posterior vitreous detachment-related initial retinal tears

PURPOSE

To determine the incidence of subsequent retinal tears (SRT) in patients who were previously treated for acute posterior vitreous detachment (PVD)-related retinal tears.

DESIGN

Retrospective chart review.

METHODS

A retrospective chart review of 155 eyes of 137 consecutive patients treated for acute PVD-related retinal tears was performed.

RESULTS

During a median follow-up of 13 months (range 3 to 157 months) after treatment, SRT developed in 19 (12.2%) of 155 treated eyes. Most of the SRT occurred during the first 6 months (12 of 19 eyes) after initial treatment. Subsequent vetinal tears developed within the first 12 months in 15 of 19 treated eyes, however only six of 15 of these eyes were symptomatic. Of those patients who developed SRT after 12 months, all had new visual symptoms.

CONCLUSION

Patients who present with acute PVD-related retinal tears are at a low but significant risk for developing SRT. A significant number of patients treated for PVD-associated retinal tears present within 1 year with SRT without symptoms.

Relation of diabetic macular edema to cytokines and posterior vitreous detachment

PURPOSE

To investigate whether angiotensin II (AII) or vascular endothelial growth factor (VEGF) is related to diabetic macular edema (DME) in patients with and without posterior vitreous detachment (PVD).

DESIGN

A case-control study.

METHODS

Vitreous fluid samples were obtained at vitreoretinal surgery from 28 eyes of 28 DME patients without PVD, 8 eyes of 8 DME patients with PVD, 14 eyes of 14 nondiabetic patients, and 8 eyes of diabetic patients without retinopathy. The VEGF levels in vitreous fluid and plasma were determined by enzyme-linked immunosorbent assay, while AII levels were measured by radioimmunoassay.

RESULTS

The vitreous levels of AII and VEGF were significantly higher in DME patients with or without PVD than in nondiabetic patients or diabetic patients without retinopathy (without PVD: P < .0061, P < .0001, P = .0261, and P < .0001; with PVD: P < .0012, P < .0001, P = .0473, and P < .0001, respectively). There was no significant difference in the vitreous levels of AII or VEGF between patients with or without PVD (P = .4948 and P = .6642, respectively). The vitreous level of AII significantly correlated with that of VEGF in DME patients without PVD (P = .576) or with PVD (P = .488). AII and VEGF levels in vitreous fluid were significantly higher than the respective plasma levels.

CONCLUSIONS

We found that the vitreous levels of AII and VEGF were elevated in DME patients irrespective of the status of PVD. Angiotensin II and VEGF may be induced in the eyes and be related to the pathogenesis of DME.

Resolution of diabetic cystoid macular edema associated with spontaneous vitreofoveal separation

PURPOSE

To report spontaneous resolution of diabetic cystoid macular edema (CME) associated with spontaneous vitreofoveal separation.

DESIGN

Interventional case series.

METHODS

Optical coherence tomography (OCT) was performed on three eyes of three diabetic patients with CME before and after vitreofoveal separation.

RESULTS

In all three eyes, OCT showed cystic changes at the fovea with a slightly detached posterior hyaloid, which remained attached to the optic disk and the fovea. After spontaneous separation of the hyaloid at the fovea, there was resolution of the cystic cavities and restoration of the foveal depression.

CONCLUSIONS

In some eyes of diabetic patients, CME is caused by a vitreous traction. Resolution of CME may occur after spontaneous vitreofoveal separation.

[Retinal complications of posterior vitreous detachment: retrospective analysis of 3 clinical cases]

Posterior vitreous detachment is an irreversible consequence of vitreal aging and will be encountered even more frequently as the population grows older. Because vitreous detachments are not always complete and clean, associated retinal complications may develop. Patients should be carefully examined at initial symptoms in order to diagnose and treat possible retinal injuries as soon as possible. Here we report a retrospective analysis of three different retinal complications of posterior vitreous detachment.

Posterior vitreous findings in cases of spontaneous retinal reattachment

PURPOSE

To describe the posterior vitreous findings in two patients with retinal detachment who experienced spontaneous retinal reattachment.

DESIGN

Two observational case reports.

TESTING

Biomicroscopic and high-resolution echographic evaluation of the vitreoretinal relationships.

MAIN OUTCOME MEASURES

Retinal reattachment and echographic vitreoretinal relationships.

RESULTS

Two patients, one with a rhegmatogenous retinal detachment and one with a tractional retinal detachment, were noted to have a partial posterior vitreous detachment with vitreoretinal adherence at the time of presentation. Spontaneous retinal reattachment occurred in both cases, with echography showing complete vitreous separation from the retina.

CONCLUSIONS

Complete posterior vitreous detachment may release tractional components in retinal detachment and contribute to spontaneous retinal reattachment.

[The vitreous and vitreoretinal interface: natural history and associated retinal diseases]

Such significant correlations have been found between vitreal changes and retinal breaks that retinal detachment is now considered as a vitreoretinal disease. Concerning this issue, not only the posterior vitreous detachment seems to play an important role in the occurrence of rhegmatogenous retinal detachment but also the vitreoretinal interactions themself seem to be important in the pathogenesis of cystoid and diabetic macular edema, proliferative diabetic retinopathy, age-related macular degeneration, macular pucker, idiopathic macular hole and macular disease associated with optic disk pit. It seemed therefore useful to the author an updated review on alterations of the vitreoretinal interface and associated ocular diseases.

Nd:YAG vitreolysis and pars plana vitrectomy: surgical treatment for vitreous floaters

PURPOSE OF STUDY

To determine the efficacy of Nd:YAG vitreolysis and pars plana vitrectomy in the treatment of vitreous floaters.

METHODS

This is a single centre retrospective study of 31 patients (42 eyes) who underwent 54 procedures, Nd:YAG vitreolysis or pars plana vitrectomy, for the treatment of vitreous floaters between January 1992 and December 2000. Main outcome measures were percentage symptomatic improvement following treatment and incidence of post-operative complications. Statistical analysis was performed using the Fisher exact test.

RESULTS

Posterior vitreous detachment was the primary cause of floaters in all 42 eyes with co-existing vitreous veils in three eyes and asteroid hyalosis in two eyes. Thirty-nine of 42 eyes received Nd:YAG vitreolysis. Thirty-eight percent found Nd:YAG vitreolysis moderately improved their symptoms while 61.5% found no improvement. After an average of 14.7 months follow-up no post-operative complications were recorded. Fifteen eyes underwent a pars plana vitrectomy, one with combined phacoemulsification and posterior chamber implantation and 11 following unsuccessful laser vitreolysis. Pars plana vitrectomy resulted in full resolution of symptoms in 93.3% of eyes. One patient developed a post-operative retinal detachment which was successfully treated leaving the patient with 6/5 VA.

CONCLUSION

Patients' symptoms from vitreous floaters are often underestimated resulting in no intervention. This paper shows Nd:YAG vitreolysis to be a safe but only moderately effective primary treatment conferring clinical benefit in one third of patients. Pars plana vitrectomy, while offering superior results, should be reserved for patients who remain markedly symptomatic following vitreolysis, until future studies further clarify its role in the treatment of patients with floaters and posterior vitreous detachment.

Incidence of retinal detachment and visual outcome in eyes presenting with posterior vitreous separation and dense fundus-obscuring vitreous hemorrhage

PURPOSE

To determine visual outcomes and the incidence of retinal detachment in eyes presenting with posterior vitreous separation and dense fundus-obscuring vitreous hemorrhage.

DESIGN

Retrospective consecutive noncomparative interventional case series.

PARTICIPANTS

Thirty-six eyes (15 right eyes and 21 left eyes) of 34 patients (18 female and 16 male) ranging in age from 42 to 94 years. Mean follow-up was 14 months.

METHODS

A comparison of the best-corrected initial visual acuities versus final visual acuities after spontaneous resolution of vitreous hemorrhage or surgical intervention. The number of eyes that were found to have retinal tears or that had a rhegmatogenous retinal detachment develop was documented. Logarithm of the minimum angle of resolution-converted visual acuities was used for comparison. Categorical data were analyzed by Fisher's exact test, and population means were compared by Student's t test.

MAIN OUTCOME MEASURES

Final mean visual acuities, number of eyes with at least one retinal tear, location of retinal tears, number of eyes that had retinal detachment develop, and the number of eyes repaired with scleral buckling surgery and/or pars plana vitrectomy.

RESULTS

Twenty-four of 36 eyes (67%) were found to have at least one retinal break (range, 0-4 breaks), with 88% of breaks located in the superior retina. Eleven eyes (31%) had more than one retinal break. Fourteen of 36 eyes (39%) had a rhegmatogenous retinal detachment develop that was repaired with pars plana vitrectomy and scleral buckling. An additional 14 eyes (39%) underwent vitrectomy for nonclearing vitreous hemorrhage. The incidence of retinal detachment in eyes with a history of retinal detachment in the contralateral eye was 75% (P = 0.04). Seven of 14 eyes (50%) with retinal detachment had coexisting proliferative vitreoretinopathy. Most retinal breaks and detachments occurred in emmetropic or myopic eyes. For all 36 eyes the mean preoperative visual acuity was 20/1233, and the mean final visual acuity was 20/62 (P < 0.0001). Eyes that had a macula-off retinal detachment develop had worse final visual outcomes (20/264; P = 0.01), as did eyes that had proliferative vitreoretinopathy develop (20/129; P = 0.04).

CONCLUSIONS

Acute, spontaneous, nontraumatic posterior vitreous separation with dense fundus-obscuring vitreous hemorrhage is associated with a high incidence of retinal tears and detachment. Close follow-up with clinical examination and ultrasonography is necessary, because many of these eyes may eventually require surgical intervention. Aggressive management with early vitrectomy should be considered when there is a history of retinal detachment in the contralateral eye.

Optic disc, foveal, and extrafoveal damage due to surgical separation of the vitreous

OBJECTIVE

To evaluate the morphologic outcomes resulting from surgical vitreoretinal separation in young adult primates.

MATERIALS AND METHODS

Vitrectomy and mechanical separation of the vitreous from the internal limiting lamina (ILL) of the posterior retina and surface of the optic disc were performed on 25 young adult cynomolgus monkey eyes in vivo. Lectin histochemical studies were used to evaluate the vitreoretinal interface. Morphologic outcomes were tabulated.

RESULTS

In 11 of 25 eye regions, residual vitreous remained attached to the ILL in some of the regions. Localized ILL breaks or separation of the ILL from the neural retina was noted in 9 eyes. Retinal tissue loss, including avulsion of the ganglion cell, inner plexiform, or inner nuclear layers, was observed in 7 eyes. Avulsion of axon bundles in the optic disc was noted in 9 eyes. Significantly, partial- or full-thickness foveal tears were noted in 11 eyes. Based on the surgeons' intraoperative observations, small superficial optic disc or retinal hemorrhages were observed in 3 of 25 eyes. None of the eyes on which a vitrectomy alone was performed showed ILL damage, or retinal or optic disc tissue loss.

CONCLUSION

Damage may occur to the optic disc, fovea, and extrafoveal retina as a result of surgical separation of the vitreous from the retina in young adult primates.

CLINICAL RELEVANCE

These data support the contention that surgically induced damage at the level of the vitreoretinal interface may help explain the visual field defects noted after surgery to close full-thickness macular holes. These data also support the need for developing additional modalities to assist in vitreous separation, thereby reducing the risk of traumatic complications associated with purely mechanical procedures.

Macular star associated with posterior hyaloid detachment

PURPOSE

To report a patient with a Leber's idiopathic stellate neuroretinitis-like lesion that was caused by vitreous traction accompanying a posterior hyaloid detachment.

METHODS

We present a 49-year-old woman who showed segmental optic disc edema, peripapillary retinal detachment, and a macular star.

RESULTS

An incomplete posterior hyaloid detachment was present, and the posterior hyaloid membrane was attached to the nasal margin of the optic disc. Fluorescein angiography revealed a bent retinal artery on the upper margin of the optic disc, and leakage of fluorescein was observed from this area.

CONCLUSION

Vascular damage to the optic disc due to vitreous traction should also be considered as a mechanism for the ophthalmoscopic appearance of the fundus when lesions suggestive of Leber's idiopathic stellate neuroretinitis are present in an adult.

Perifoveal vitreous detachment is the primary pathogenic event in idiopathic macular hole formation

OBJECTIVE

To evaluate the relationship between the posterior vitreous cortex and the posterior retina in eyes with early stages of idiopathic macular hole formation.

METHODS

Twenty-six eyes of 26 consecutive patients with stage 1 or stage 2 idiopathic macular hole underwent complete ophthalmologic examination, contact lens biomicroscopy, and B-scan ultrasonography or vitreoretinal surgery or both. In eyes that were operated on, the posterior cortical vitreous layer was meticulously examined with a silicone-tipped cannula prior to inducing a posterior vitreous detachment.

RESULTS

In 25 (96%) of 26 eyes, one or more examination techniques revealed a shallow, localized detachment of the perifoveal vitreous, typically extending to the level of the vascular arcades. Among these 25 eyes, the posterior hyaloid membrane separation was detectable biomicroscopically in 4 (16%) of 25 eyes, ultrasonographically in 17 (74%) of 23 eyes, and intraoperatively in 23 (100%) of 23 eyes. Persistent vitreous adherence to the foveola was evident in 6 (100%) of 6 eyes with a stage 1 hole and in 12 (92%) of 13 eyes with a stage 2 hole but no operculum.

CONCLUSIONS

These findings suggest that localized perifoveal vitreous detachment (an early stage of age-related posterior vitreous detachment) is the primary pathogenic event in idiopathic macular hole formation. We postulate that detachment of the posterior hyaloid from the pericentral retina leads to foveal dehiscence by exerting anterior traction on the foveola and by localizing into the foveola the dynamic vitreous traction associated with ocular rotations.

Acute posterior vitreous detachment: the predictive value of vitreous pigment and symptomatology

AIM

To establish whether the presence of a retinal break can be predicted either by the presence of a positive Shafer's sign (pigment granules in the anterior vitreous) or symptomatology in patients presenting with an acute posterior vitreous detachment (PVD).

METHODS

200 eyes of 200 phakic patients with a symptomatic PVD of less than 1 month's duration underwent documentation of symptomatology and examination of the anterior vitreous for the presence of pigment granules. Indentation ophthalmoscopy was then carried out by an experienced vitreoretinal surgeon with no knowledge of the symptomatology or anterior vitreous gel examination findings. A second prospective group of 115 consecutive patients were assessed in a similar manner before primary rhegmatogenous retinal detachment repair.

RESULTS

In 200 eyes presenting with an acute PVD, 25 were found to have an associated retinal break, 23 of which were also Shafer positive. In 115 eyes presenting for retinal detachment repair, 111 had an associated PVD and were found to be Shafer positive. Symptomatology was not predictive of an associated retinal break in the PVD group or in those presenting with a retinal detachment.

CONCLUSION

The increased use of Shafer's sign is recommended as a valuable aid in determining which patients require urgent referral for an expert retinal examination. It is not possible to predict those patients with a retinal break secondary to PVD on the basis of symptomatology alone.

Diagnosis of vitreoretinal adhesions in macular disease with optical coherence tomography

PURPOSE

To compare the relative incidence of vitreoretinal adhesions associated with partial vitreous separation within the macula diagnosed with optical coherence tomography (OCT) with that of those diagnosed with biomicroscopy.

METHODS

The authors obtained linear cross-sectional retinal images using OCT in patients with selected macular diseases. Additional studies included biomicroscopy, fundus photography, fluorescein angiography, and B-scan ultrasonography.

RESULTS

Optical coherence tomography was performed on 132 eyes of 119 patients. Vitreoretinal adhesions within the macula were identified using OCT in 39 eyes (30%) with the following diagnoses: idiopathic epiretinal membrane (n = 13), diabetic retinopathy (n = 7), idiopathic macular hole (n = 7), cystoid macular edema (n = 7), and vitreomacular traction syndrome (n = 5). Biomicroscopy identified vitreoretinal adhesions in only 11 eyes (8%). Two distinct vitreoretinal adhesion patterns were identified with OCT, each associated with partial separation of the posterior hyaloid face: focal (n = 25) and multifocal (n = 14).

CONCLUSIONS

Optical coherence tomography is more sensitive than biomicroscopy in identifying vitreoretinal adhesions associated with macular disease.

Spontaneous closure of macular hole after posterior vitreous detachment

Macular holes can be treated with surgically-induced vitreous detachment and gas tamponade. The authors report a case of a macular hole that closed spontaneously after the development of posterior vitreous detachment (PVD). Optical coherence tomography (OCT) revealed a small full-thickness macular hole with perifoveal cystic changes in a 25-year-old female with a central scotoma at her initial visit. There was no evidence of PVD. Five months later, PVD was observed and the macular hole disappeared. OCT performed three months later showed macular hole closure and resolution of the perifoveal cystic changes. The physiologic pit was restored in the fovea. OCT is useful to detect and monitor the morphologic changes of a macular hole.

Dome-shaped detachment of premacular vitreous cortex in macular hole development

PURPOSE

To clarify the role of the posterior vitreous cortex in macular hole development, we evaluated the follow-up findings of clinical observations and optical coherence tomography (OCT) images of macular holes in early stage.

METHODS

The vitreoretinal tomography was examined and followed in eyes with stage 1 and 2 macular holes with OCT.

RESULTS

The posterior cortical vitreous was identified in 12 of 17 eyes with early-stage macular holes by OCT (71%). In these eyes, the detached posterior vitreous appeared to be merged to the fovea and the disc. The vitreoretinal separations showed typically dome-shaped. A long scan along the papillomacular axis also delineated the posterior vitreous face as dome-shaped perifoveal vitreous detachment with adhesion to the fovea and disc. Repetitive OCT examinations clearly demonstrated the course of development of the macular hole.

CONCLUSIONS

The dome-shaped vitreoretinal separation seen with OCT gives rise to an idea that the posterior vitreous cortex may not be taut but slack, and would not cause a continuous tractional force even in early-stage macular holes. This finding brings us an idea that the tangential traction at the fovea may be generated by fluid movements, rather than by contraction of the cortical vitreous.

[Slit-lamp perimetry: a new diagnostic technique]

AIM OF THE STUDY

To test a novel diagnostic technique, slit-lamp perimetry.

PATIENTS AND METHODS

Slit-lamp perimetry is performed during a normal slit-lamp examination by projecting a small, round light mark onto the fundus. The light mark is moved and consecutively the patient is asked, if the light moved towards or away from the scotoma. Using the patients feedback the light mark can be placed exactly onto the retinal region corresponding to the scotoma. This method was tested on a patient with a microinfarction of a small retinal arteriole and on two patients with small preretinal parapapillary vitreous floaters.

RESULTS

Slit-lamp perimetry correctly localized preretinal vitreous floaters and a fresh cotton wool spot missed on an dilated fundus examination.

CONCLUSION

Slit-lamp perimetry is a novel rapid diagnostic technique to localize retinal and preretinal pathologies reponsibles for scotomas.

Role of the vitreous in age-related macular degeneration

PURPOSE

To investigate the relationship between posterior vitreous detachment (PVD) and age-related macular degeneration (AMD).

METHODS

The condition of the vitreous was examined by slit-lamp funduscopy and ultrasonography in 93 eyes of 50 patients with AMD (exudative or dry) and 100 eyes of 50 controls.

RESULTS

There was complete PVD in 31 of the 93 eyes (33.3%) of 50 patients with AMD and the posterior vitreous was attached in 62 of these eyes (66.6%). In the control group, in 50 eyes (50%) of 50 subjects there was posterior vitreous detachment. The prevalence of PVD in eyes with macular degeneration was significantly lower (P < .05). There was no statistically significant difference between the exudative and the nonexudative groups in respect to PVD.

CONCLUSIONS

PVD may have a protective role against the development of AMD. Chronic vitreomacular traction and/or continuous exposure to free radicals and cytokines may possibly be one of the causes of AMD in eyes with attached vitreous.

Papillofoveal traction in macular hole formation: the role of optical coherence tomography

OBJECTIVES

To determine the validity of the assumption that optical coherence tomographic scans of macular holes have a discrete linear signal (DLS) that represents a detached posterior vitreous face, and to analyze the DLS in macular hole pathogenesis.

METHODS

Optical coherence tomographic scans were taken of 3 situations in which the vitreous conditions were known: (1) dissected intact vitreous, (2) clinically evident Weiss rings, and (3) maculae before and after saccades in eyes without a biomicroscopic posterior vitreous detachment. In addition, 70 eyes of 35 patients with macular holes underwent clinical examination and optical coherence tomographic scanning that passed through the optic disc and the fovea or macular hole.

RESULTS

Spatial properties of the DLS matched those of the posterior vitreous face in the situations examined. Of the 70 eyes, 16 (23%) had a biomicroscopic posterior vitreous detachment, whereas a DLS was demonstrated in 40 (57%). Of the 54 eyes without a biomicroscopic posterior vitreous detachment, 18 (33%) had a DLS attached focally to the optic disc margin and the fovea or macular hole. All 7 of the "can opener" holes examined had a nasally "hinged" central flap, 6 with a focally attached DLS.

CONCLUSIONS

The DLS corresponds to the posterior vitreous face. Anteronasal papillofoveal traction may generate some macular holes.

Retinal detachment associated with a macular hole in severely myopic eyes

PURPOSE

To investigate factors associated with extensive retinal detachment in severely myopic eyes with a macular hole.

METHOD

Fifty-two consecutive eyes with a macular hole and severe myopia were retrospectively studied.

RESULTS

An extensive retinal detachment, defined as extending beyond the cuff of subretinal fluid, was observed in 37 eyes (71%). Extensive retinal detachment developed in 36 (95%) of 38 eyes with a posterior staphyloma and in one (7%) of 14 eyes without a posterior staphyloma (P<.0001). Extensive retinal detachment also developed in 32 (89%) of 36 eyes with complete posterior vitreous detachment and in five (31%) of 16 eyes without posterior vitreous detachment (P<.0001).

CONCLUSION

Posterior staphyloma rather than anteroposterior vitreomacular traction may contribute to the development of retinal detachment associated with a macular hole in severely myopic eyes.

Preservation of vision through Weiss ring after dense vitreous hemorrhage

PURPOSE

To report an unusual case of retained vision through a Weiss ring in the setting of dense vitreous hemorrhage.

METHOD

Case report of a 55-year-old woman with a 23-year history of type 1 diabetes mellitus who presented with new onset of blurred vision in the left eye as a result of a dense vitreous hemorrhage.

RESULTS

The patient had received full scatter laser photocoagulation for proliferative diabetic retinopathy in the right eye several years earlier and reported previous resolving episodes of vitreous hemorrhage in the left eye. Best-corrected visual acuity in the left eye was hand motions at 3 feet. However, with careful head positioning visual acuity improved to 20/40 through a small clear central island. Examination of the left fundus showed a dense vitreous hemorrhage with a clear, mobile opening in the posterior hyaloid corresponding to the Weiss ring. The retina could be partially visualized only through the area of the Weiss ring.

CONCLUSIONS

This unusual case demonstrates the anatomical relationship between the posterior hyaloid and Weiss ring.

Treatment of retinal tears and lattice degenerations in fellow eyes in high risk patients suffering retinal detachment: a prospective study

BACKGROUND/AIMS

Fellow eye prophylaxis for retinal detachment (RD) is still a controversial issue since opinions are not unanimous regarding the kind of lesions to be treated or the method of treatment. This prospective clinical study aimed to follow the course of vitreoretinal conditions in 150 high risk fellow eyes.

METHODS

150 consecutive patients with unilateral rhegmatogenous RD were included in this study. Inclusion criteria were good explorability of fellow eye retinal periphery and one of the following conditions in the fellow eye-aphakia, pseudophakia with capsulotomy, high myopia (>-6D), contralateral eye to a giant retinal tear. Prophylactic treatment (photocoagulation or scleral buckling) was performed in the presence of retinal tears and lattice degenerations. The state of the vitreous body was determined at the beginning of the study and at the end, when RD occurred.

RESULTS

Follow up ranged from 36 to 132 months. 95 fellow eyes were subjected to laser treatment; five eyes underwent prophylactic surgical treatment. Initially, in the treated group posterior vitreous detachment (PVD) was present in 100 eyes (100% of cases), but as a complete PVD only in 42 of them (42%). 10 eyes in the treated group developed RD during the follow up period. In five of these cases the partial PVD had progressed and a retinal tear in a previously healthy area was the cause of the retinal detachment. In the other five eyes RD apparently developed from previously treated lesions. Progression of PVD was evident in four out of these five eyes. The untreated eyes had no visible degenerative lesions. During follow up eight eyes developed RD. These eyes had no PVD at the beginning of the study, but showed a partial PVD at the time of the diagnosis of RD.

CONCLUSION

Fellow eyes with pre-existing retinal tears and PVDs can go on to retinal detachment in spite of laser prophylactic treatment. When PVD is not detectable or a partial PVD is present, the progression of posterior vitreous separation can account for retinal tears and RDs arising in formerly healthy areas.

Differential diagnosis of common etiologies of photopsia

BACKGROUND

Photopsia is a relatively common symptom reported by patients in primary eye care settings. Although there are many possible etiologies, photopsia (light flashes) is usually associated with one of the following: (1) posterior vitreous detachment, (2) migraine with aura, (3) migraine aura without headache, and (4) retinal break or detachment. Each of these clinical conditions has symptoms and physical findings that will usually render the diagnosis apparent.

METHODS

It is important from a clinicolegal standpoint that specific procedures be performed to differentially diagnose the responsible condition and deliver appropriate follow-up care.

Modifying factors related to asymmetric diabetic retinopathy

PURPOSE

To identify the modifying factors related to the development of proliferative diabetic retinopathy (PDR).

METHODS

Thirty-eight eyes of 19 non-insulin-dependent diabetes mellitus (NIDDM) patients with maintained asymmetric PDR were retrospectively reviewed.

RESULTS

Five patients with ipsilateral carotid stenoses > or = 90% had PDR. Four patients with high myopia over 6 dioptres and 4 patients with optic atrophy and at least a quadrant defect in the visual field had non-proliferative diabetic retinopathy. Of 6 patients with unilateral asteroid hyalosis, 5 had no posterior vitreous detachment (PVD) and PDR.

CONCLUSION

Two factors reached statistical significance as factors modifying PDR: carotid occlusive disease and PVD. Optic atrophy and high myopia showed trends of being a protective influence.

The posterior vitreous detachment clinic: do new retinal breaks develop in the six weeks following an isolated symptomatic posterior vitreous detachment?

PURPOSE

Symptomatic posterior vitreous detachment (PVD) is sometimes associated with sight-threatening retinal tears or retinal detachment. Patients are usually reviewed twice because it is believed that retinal breaks may develop within 6 weeks of a PVD and as such the management of a PVD consumes significant resources. The aim of this study was to find the frequency of retinal breaks developing within 6 weeks of an isolated PVD using the same experienced examiner at both visits.

METHOD

Patients presenting to the eye casualty with symptomatic PVD were examined by the casualty staff. Those with a retinal break or retinal detachment were referred directly for treatment and those with only a PVD were seen within 8 days in the PVD clinic. They were examined by a vitreo-retinal Fellow using indirect ophthalmoscopy and a 20 D lens with scleral indentation. The position and nature of any retinal abnormalities were noted and compared with those described in the casualty notes. Those with sight-threatening breaks were referred for treatment and the remainder were reviewed 5 weeks later when the presence of any new breaks was noted.

RESULTS

One hundred and seven patients were referred to the PVD clinic over a 6-month period, of whom 2 did not have a PVD. At the first visit to the PVD clinic 6 patients had round holes anterior to the equator, 2 had equatorial horseshoe tears and 1 had lattice with holes. At the second visit, 2 additional patients had round holes anterior to the equator but in both the retina had been obscured by vitreous haemorrhage at the first visit. No patient in whom a full examination was possible at the first visit developed further retinal pathology.

CONCLUSION

These results demonstrate the need to perform a full examination of the peripheral retina with scleral indentation at the time of presentation and emphasise the importance of finding a vitreous haemorrhage following a symptomatic PVD. If no retinal breaks are detected by thorough examination at presentation, further reviews, in the absence of increasing symptoms, may not be necessary.

[Iridoschisis--case report]

A case of 54-year-old man with a rare degenerative condition of the iris stroma is presented. Described iridoschisis has developed in superior part of iris. Open-angle glaucoma and degeneration of vitreous was associated.

Vitrectomy for proliferative diabetic retinopathy with asteroid hyalosis

PURPOSE

To characterize the clinical features of proliferative diabetic retinopathy (PDR) with asteroid hyalosis treated by pars plana vitrectomy.

METHODS

Vitrectomy was performed in 26 eyes with PDR accompanied by asteroid hyalosis (7 eyes with vitreous hemorrhage, 6 eyes with tractional retinal detachment with vitreous hemorrhage, and 13 eyes with tractional retinal detachment without vitreous hemorrhage). We observed the occurrence of posterior vitreous detachment intraoperatively and evaluated the clinical characteristics retrospectively.

RESULTS

In 24 eyes, posterior vitreous detachment was slight, necessitating artificial detachment. Of the 26 eyes, 20 experienced iatrogenic retinal breaks and 6 (23%) experienced postoperative retinal detachment due to iatrogenic breaks. Three cases worsened to anterior proliferative vitreoretinopathy and retinal reattachment could not be achieved.

CONCLUSIONS

In vitrectomy for PDR with asteroid hyalosis, and in cases of simple vitreous hemorrhage, surgery should be performed with full understanding of the anatomic characteristics. Notably, if posterior vitreous detachment is not present, the occurrence of iatrogenic retinal breaks is more likely.

An optical explanation of the entoptic phenomenon of 'clouds' in posterior vitreous detachment

The purpose of this work is to investigate in detail the optics of the shadow cast by vitreous opacities and its effects in the perception of related entoptic phenomena. The optics of the eclipse has been used as a model. The various parameters affecting the shadow, i.e. the diameter of the opacity, its distance from the retina and the overall distance between the pupillary plane and the retina, have been taken into account in the calculations. A mathematical function has been derived and curves defining the density of the penumbra have been plotted for various distances of an opacity from the retina. An area of uniform partial illumination of the retina behind the opacity has been defined, outside of which the density of the penumbra falls rapidly. It is concluded that the sensation of 'cloud' or 'smoke' reported by the patient stems from this uniform area of penumbra behind the opacity, whose extent depends on the above mentioned parameters. Thus, the optics of the eclipse explains this entoptic phenomenon. Of course, 'clouds' can also be due to semi-transparent vitreous floaters.