Glial and Neural Response in Short-term Human Retinal Detachment

Histopathological changes following acute retinal detachment have been well documented in animal models.^1-3 To date, however, the changes that follow an acute human retinal detachment are not well characterized owing to the difficulty in obtaining retinal specimens. When retinal detachment is complicated by proliferative vitreoretinopathy, samples obtained from patients undergoing retinectomy provide an insight into the pathologic abnormalities of more chronic stages of retinal detachment. These changes include glial cell intermediate filament up-regulation, glial extensions into epiretinal and subretinal membranes, photoreceptor outer and inner segment disorganization, opsin redistribution, photoreceptor axon retraction and neurite extension, and second- and third-order neurone remodeling.⁴ In this histopathological case report, we extend our previous studies to the analysis of a patient with a short-term retinal detachment.

A 74-year-old woman was admitted to Manchester Royal Eye Hospital with a 10-day history of visual loss in her right eye. She had noted increasing floaters in this eye for approximately 1 month prior to this. She was found to have a bullous superotemporal rhegmatogenous retinal detachment involving the macula. She had no previous history of ophthalmic disease but had asthma and hypertension. Before retinal surgery could be undertaken, she had a cardiac arrest and died on the ward. With the relatives' consent, the eyes were obtained for analysis.

The right eye was fixed in formalin within 6 hours of death. Retinal tissue was sampled from various sites within the detachment both adjacent to the retinal break and in areas further removed from this region. Samples were embedded in agarose and cut as 100-μm sections. Retinal sections were then double-labeled for immunohistochemistry by using antibodies to retinal glia (glial fibrillary acid protein), photoreceptors (rod opsin, M and S cone opsins), horizontal cells (calbindin D), synaptic vesicle protein (synaptophysin), and retinal pigment epithelium cells (cellular retinaldehyde binding protein). Secondary antibodies were conjugated to Cy2(green) or Cy3(red) and viewed using a BioRad 1024 confocal microscope (Bio-Rad Laboratories, Hercules, Calif). The techniques used and antibody sources have been detailed previously.⁴ TUNEL staining was performed to identify apoptotic cells.⁵

Macroscopically, retinal breaks were identified within the area of detachment. Samples of retinal tissue selected from foci adjacent to the retinal breaks demonstrated more advanced degenerative changes when compared with tissue from areas more distant from the breaks.

In the retina immediately adjacent to the retinal breaks, there was obvious loss of normal retinal architecture with extensive glial cell hypertrophy forming a confluent scar around the break edge (Figure 1). In this area, there was marked loss of neural retinal elements, including photoreceptor inner and outer segments and redistribution of rod opsin to rod cell bodies. There was also evidence of rod axon extensions toward the ganglion cell layer (Figure 1D).

In areas of detachment remote from the retinal breaks, pathological changes were less extensive with residual (though disorganized) rod and cone outer segments (Figure 2). Photoreceptor inner segments were preserved, and there was redistribution of opsins to photoreceptor cell bodies. Very occasional apoptotic photoreceptor cells were observed (TUNEL data not shown). Irregular synaptophysin immunostaining was seen in the outer plexiform layer. Marked glial fibrillary acid protein up-regulation and evidence of internal limiting membrane disruption suggested early glial epiretinal membrane formation (Figure 2). Calbindin labeled horizontal cells (and cones).

This case demonstrates a range of glial and neural retinal pathologic abnormalities. The pathological changes observed in areas of detachment remote from the retinal breaks were consistent with those observed in animal models of acute retinal detachment. In the feline model, a 3-day detachment shows degeneration of the rod and cone outer segments, redistribution of opsins to the photoreceptor cell bodies, withdrawal of rod synaptic terminals toward their cell bodies, outgrowth of rod bipolar and horizontal-cell neurites, and Müller cell proliferation and hypertrophy.³ Photoreceptor apoptosis has also been demonstrated in acute retinal detachment,^6-8 which peaks at around day 3 or 4 after retinal detachment but then decreases dramatically.⁸ This is consistent with our results; we found little evidence of apoptosis, which suggests that at 10 days after detachment the major wave of apoptosis has already passed.

The potential for long-term sequelae following an acute retinal detachment in humans is demonstrated in this case by the observation of areas of early neural circuitry change (photoreceptor neurite extension and synaptic remodeling), photoreceptor disorganization, and early epiretinal membrane formation (Figure 1B and C)—changes analogous to those seen in animal models.¹

There was advanced glial scarring and marked loss of photoreceptors adjacent to the retinal breaks (Figure 1). This is more consistent with the findings observed in a 28-day retinal detachment in the feline model.² The severity of this pathologic abnormality may be attributed to a localized peripheral retinal detachment having been present around the retinal tear for longer than the 10-day history of visual loss. The initial retinal break may well have occurred at the time of onset of floaters 1 month (or longer because the history was vague) before visual loss. Alternatively, the effect of the trauma of the retinal tear and/or ischemic disruption of the local inner retinal circulation may induce necrotic (including apoptotic) cell death and marked gliosis in the surrounding retina.⁹ In animal models, retinal detachment induction is highly controlled with a micropipette; this differs from the clinical pattern of events in which acute retinal tears of variable size are induced by vitreoretinal traction at the time of posterior vitreous detachment. It is possible that retinal tearing may act as a more potent stimulus for cellular disorganization, loss, and remodeling, leading more rapidly to the advanced pathologic abnormalities usually seen following longer periods of retinal detachment in animal models.

The nature of the observed pathologic abnormalities in this case is consistent with those found previously in animal models and is similar to, but less advanced than, the changes seen in human proliferative vitreoretinopathy.⁴ The similarities to this and other human studies emphasizes the validity of the animal models currently used in the investigation of the cellular and molecular events that follow retinal detachment.

Correspondence: Dr Wickham, Vitreoretinal Research, Moorfields Eye Hospital, City Road, London EC1V2PD, England (louisa.w@tiscali.co.uk).

Financial Disclosure: None reported.