Purpose
To examine the optical coherence tomography (OCT) and histologic features of Descemet membrane detachment (DMD) to ascertain the involvement of the pre-Descemet layer (PDL).
Design
Retrospective, observational case series.
Methods
Clinical, histopathologic, and OCT features of a cohort of 41 cases with diagnosis of DMD from 4 centers were studied. OCT images were evaluated independently by 3 observers for number of detached layers (1 or 2), reflectivity, configuration (straight line or wavy), distance from posterior stroma, and presence or absence of a tear with any scrolling of the torn edges. Five had a histology specimen. The main outcome measure was the involvement of the PDL in DMD and its confirmation by histology.
Results
Three types of DMD were identified: type 1, where the PDL and DM were detached together; type 2, where only the DM was detached; and mixed, where the PDL and DM were detached but also separated from each other. These were further found to be rhegmatogenous or nonrhegmatogenous depending on the presence of absence of a tear in DM or both layers. Histology confirmed involvement of PDL in all 5 cases and showed it to be infiltrated by cells in 3 of 5 cases.
Conclusions
The PDL is involved in DMD. This fact significantly changes our understanding of DMD and could have implications for management. The detached PDL can be infiltrated with cells. A prospective study in relation to etiology and types of DMD is needed.
Highlights
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Descemet membrane (DM) detachment (DMD) is not always the detachment of the DM alone.
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The pre-Descemet layer (PDL) often also detaches with the DM.
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The PDL and DM may detach but remain attached to each other (type 1 detachment).
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The DM may detach by itself (type 2 detachment) or with PDL but separated from it (mixed type).
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Recognition of detachment of PDL is important in understanding DMD and its management.
Descemet membrane detachment (DMD) has been recognized as a pathology of the posterior cornea, occurring especially after complicated or multiple intraocular surgery, for close to a hundred years. The first cases with this condition were described by Fuchs as recorded by Samuels in his thesis. Persistent edema of the overlying corneal stroma and epithelium is the hallmark clinical feature. Vision is affected when edema involves the pupillary area. There have been several attempts at classifying DMD based on pathology, clinical features, and imaging techniques. , The first reported classification was based on pathology and described 3 types of DMD: active (pushed back), passive (pulled back and torn away), and a third type due to difference in elasticity of DM and the anterior parenchyma. Mackool and Holtz described DMD as planar where the distance of the DMD from the posterior stroma was 1 mm or less and nonplanar where the separation was greater than 1 mm. These were further subdivided into peripheral (peripheral 3 mm of the cornea) and/or central. A contemporary classification based on anterior segment (AS) optical coherence tomography (OCT) has been proposed by Jacob and associates, who divided DM detachment into rhegmatogenous, tractional, bullous, and complex and suggested treatment protocols based on the classification proposed.
DMD is reported to be most common following cataract and other intraocular surgery, especially when associated with intraoperative complications or multiple surgeries. , Besides an iatrogenic etiology, DMD can be secondary to trauma or occur spontaneously. Both iatrogenic and traumatic DMD can occur early or late after the event. , , , Spontaneously occurring DMD is seen in acute hydrops associated with ectatic corneal disorders, especially keratoconus.
The demonstration of the pre-Descemet layer (Dua’s layer, PDL), recently also termed the Dua-Fine layer by the American Association of Ocular Oncologists and Pathologists, has added another dimension to DMD. None of the descriptions and classifications of DMD take into consideration the PDL. Dua and Said reported a case where the PDL and the DM detached independent of each other, with the latter showing a tear and scrolled edge. We undertook a retrospective analysis of anterior segment OCT images, clinical history, and histology of DMD to ascertain the association of PDL detachment in DMD and report novel findings that enhance our understanding of DMD, with diagnostic and potential therapeutic implications.
Methods
Sample Collection
Forty-one cases with a diagnosis of DMD, from the OCT database over a period of 5 years, were retrospectively studied. Twenty-three cases were from the All India Institute of Medical Sciences, New Delhi, India; 14 from the Queens Medical Centre, Nottingham, UK; 3 from Narayana Nethralaya, Bangalore, India; and 1 from the Optimed Eye and Laser Clinic, Queenswood, South Africa. Twenty-nine patients had DMD following cataract surgery (phacoemulsification [26] and small-incision cataract surgery [3]); 5 had corneal transplants (4 failed penetrating keratoplasty [PK] and 1 failed Descemet stripping endothelial keratoplasty (DSEK); 4 had corneal ectasia with acute hydrops (3 keratoconus and 1 pellucid marginal degeneration), and 3 had history of descemetocele following corneal infections. Patient details are given in the Table . All cases had OCT performed at presentation. Those from Nottingham and the case from Queenswood had OCT with the anterior segment attachment to the Heidelberg Spectralis OCT, wavelength 870 nm (Heidelberg Engineering GmbH, Heidelberg, Germany) and the rest had it with the RTVue, wavelength 840 ± 10 nm (Optovue, Inc, Fremont, California, USA). High-resolution vertical and horizontal OCT sections were obtained. Scans were performed to cover the area of detachment. Each of the 41 patients had between 20 and 45 high-resolution scans in both the vertical and horizontal orientations. As the study was retrospective in nature, it was categorized as an audit of patient notes with no direct involvement of patients.
| Diagnosis | Number of Cases | Age Range/Median | Sex, F/M | DMD | Duration to Diagnosis | Comments | ||
|---|---|---|---|---|---|---|---|---|
| Type 1 | Type 2 | Mixed | ||||||
| Cataract | 45-83/62 | 10 | 13 | 6 | Day 1 to 12 weeks | Treated with intracameral injection of air or C3F8, or conservatively. DSEK in 2 cases and DMEK in 1 case. | ||
| Phacoemulsification | 26 | 12/14 | ||||||
| SICS | 3 | 1/2 | ||||||
| Acute hydrops | Within 1 week | Treated conservatively with hypertonic saline and carmellose drops. One patient subsequently had PK. | ||||||
| Keratoconus | 3 | 24-30/24 | 1/2 | 3 | ||||
| PMD | 1 | 62 | 1/0 | 1 | ||||
| Descemetocele | 3 | 71-83/80 | 2/1 | 2 | 1 | 1 week to 3 weeks | Treated with cyanoacrylate glue and PK in 1 case | |
| Failed corneal graft | ||||||||
| PK for keratoconus | 2 | 24, 52 | 0/2 | 2 | >1 month | Treated with repeat PK | ||
| PK for corneal scar | 2 | 71, 76 | 0/2 | 2 | >2 months | Treated with repeat PK | ||
| DSEK | 1 | 82 | 1/0 | 1 | 1 week | Treated with PK | ||
Clinical Evaluation and OCT Analysis
The clinical history, treatment offered, and clinical notes including slit-lamp and OCT images were reviewed in the context of the knowledge of the posterior corneal anatomy with regard to the Descemet membrane (DM) and PDL. All scans were independently reviewed by 3 of the authors (H.D., D.S., and A.R.) and types of DMD recorded. The distance between the detached layer(s) and the posterior surface of the cornea was measured at the point of greatest separation. Statistical analysis was performed using the Statistical Package for Social Sciences for Windows, version 19 (SPSS Inc, Chicago, Illinois, USA). Differences between observers were analyzed using 1-way analysis of variance.
Histologic Examination
Tissue was available for histologic examination from 5 cases: 2 subjects had DMD post phacoemulsification (1 was treated with Descemet membrane endothelial keratoplasty [DMEK] and 1 with DSEK); 2 had PK for failed previous full-thickness grafts with DMD; and 1 had PK post resolution of acute hydrops. Full-thickness corneal tissue samples (3 specimens) were cut in 2 halves; and tissue removed by stripping during endothelial keratoplasty (2 specimens) was flattened on paper. All samples were fixed in formalin and paraffin embedded (1 was resin embedded), and sections of 7-10 μm were mounted on glass slides and stained with hematoxylin-eosin (resin sample was stained with toluidine blue) for light microscopy. Sections were scanned with the Nanozoomer Digital Pathology Microscopy System (Hamamatsu, Hamamatsu City, Japan) at 40× magnification and examined for number of detached layers and cellular infiltration (4 samples) and by light microscopy at 40× (1 sample).
Results
Clinical History and Management
All cases with DMD following cataract surgery were diagnosed within 4 weeks of surgery, except for 2 that presented after 2 and 3 months, respectively. All cases were treated with intracameral injection of air or perfluoropropane. Three required endothelial keratoplasty (2 DSEK and 1 DMEK). All 4 cases with acute hydrops were managed conservatively with 5% sodium chloride drops and topical lubricants (carmellose 0.5% 4-6 times a day) until the hydrops resolved in 4-6 months. One of these required PK subsequently. All 4 cases with DMD associated with failed PK were treated with repeat PK and the 1 case with failed DSEK had rebubbling and subsequently a PK. The 3 cases with descemetocele were following bacterial keratitis and nonhealing epithelial defects. These were glued with cyanoacrylate glue and 1 was followed by PK. Clinically all patients had corneal edema. DMD was seen on slit-lamp examination but visibility depended on the extent of overlying corneal edema ( Figure 1 ).
Anterior Segment OCT Findings
ASOCT of DMD showed 3 patterns:
- (1)
A straight taut DMD, like the chord of a circle, made of a thick hyperreflective strand, which at places showed a double contour. This was termed type 1 DMD ( Figures 2-5 ). The straight taut hyperreflective strand represented the detachment of the PDL and DM from the posterior stroma but with each remaining attached to the other. At times the DM presented as a double contour line on the posterior aspect of the PDL. Type 1 DMD was seen in a total of 15 cases, including 10 with post–cataract surgery DMD, all 4 cases of DMD associated with failed previous PK, and 1 with failed DSEK.
Figure 2
Anterior segment optical coherence tomography (ASOCT) images of the 3 types of Descemet membrane detachment (DMD) for comparison. Top. Type 1; the DMD is a straight line and “taut,” like the chord of a circle. This is the separation of the pre-Descemet layer (Dua’s layer, PDL) together with the Descemet membrane (DM), which remain attached to each other (Heidelberg Spectralis OCT). Middle. Type 2; the DMD is undulating and is made of 2 parallel hyperreflective lines separated by a narrow dark space. This is the characteristic OCT appearance of the DM (RTVue, Optovue OCT). Bottom. Mixed; the DMD has 2 components, an anterior hyperreflective band representing the PDL (long thin arrow) and a posterior undulating band made of 2 fine hyperreflective lines separated by narrow dark space representing the DM (short thick arrows), as in the top image (Heidelberg Spectralis OCT).
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