Örebro University Medicine
Bachelors thesis, 15 credits
May 2020
Giant retinal tears vs primary rhegmatogenous
retinal detachments
A study with the purpose of comparing postoperative results and complications Version 2
Author: Albert Pettersson
Supervisor: Prof. Sven Crafoord Department of ophthalmology Örebro university hospital
Abstract
Introduction
Giant retinal tears (GRT) are rare and difficult to treat. Today, there are seven centers in Sweden where this complicated form of rhegmatogenous retinal detachment (RRD) can be treated. Despite the technical and surgical advances in the last decades, the ideal treatment is still unknown. In the end, the choice is made by an individual surgeon, without much research to back it up.
In contrast, a mild form of RRD is considered easier to handle. Previous studies describe a single surgery success rate of over 90% for this form of RRD. This is higher compared to giant retinal tears, where the rate is 70-90%.
Purpose
The purpose of this study was to compare the postoperative results and complications of giant retinal tears with a mild type of rhegmatogenous retinal detachment.
Method
This is a retrospective cohort study of 18 patients with GRT treated at USÖ between 2013-2017. The GRT sample was matched with the same number of patients with a mild form of RRD treated at USÖ between 2011-2019. The period before, under and after surgery were investigated to compare results and complications.
Results
Several factors with statistical significance were found: the single surgery success rate is higher in GRT; the number of reoperations is less when an outlier has been removed; the frequency of glaucoma and residual silicone oil are higher in GRT; the rate of preoperative epiretinal membranes is higher in RRD, and the portion of preoperative proliferative vitreoretinopathy (PVR) is higher in GRT.
Conclusion
Somewhat surprisingly, the results present a higher single surgery success rate in GRT than the mild form of RRD. Compared to literature the rate for RRD is relatively low, but the rate for GRT is among the best compared to other studies. However, this may be due to the small sample size and potential bias in the matching. Before surgery GRT presents with worse preoperative visual acuity and higher rate of complications. These differences seem to shrink after surgery. The exception being glaucoma, which is more common in GRT.
3
Abbreviations
BCVA - best corrected visual acuity
GRT - giant retinal tear
IOP - intraocular pressure
OCT - optical coherence tomography
PFCL - perflourocarbon liquid
PPV - pars plana vitrectomy
RPE - retinal pigment epithelium
RRD: - rhegmatogenous retinal detachment
USÖ - Örebro University Hospital
Table of contents Abstract ... 2 Introduction ... 2 Purpose ... 2 Method ... 2 Results ... 2 Conclusion ... 2 Abbreviations ... 3 Introduction ... 5
Rhegmatogenous retinal detachments ... 5
Giant retinal tears ... 7
Who are affected by giant retinal tears? ... 7
Why do they occur? ... 7
Proliferative vitreoretinopathy ... 8 Process ... 8 Risk factors ... 9 Epiretinal membranes ... 9 Treatment of GRT ... 9 Aim ... 11
Material and method ... 11
Study design ... 11 Method ... 11 Inclusion criteria ... 11 Exclusion criteria ... 11 Material ... 11 Visual acuity ... 11 Surgical results ... 12 Postoperative complications ... 12 Statistical analysis ... 13 Ethical discussion ... 13 Results ... 14 Discussion ... 18 Strengths ... 20 Weaknesses ... 20 Conclusion ... 21 Acknowledgements ... 21 References ... 22
5
Introduction
Retinal surgery has long been at the forefront of medical technology. For example: the first use of laser in clinical practice was in ophthalmology. The latest innovation is in retinal imaging. Better visualization of the retina would allow more precise surgical intervention of this delicate tissue forming the basis of sight. [1]
Rhegmatogenous retinal detachments
The retina derives from the embryonal structure as the optic cup. The inner layer later becomes the neurosensory retina, and the outer layer the retinal pigment epithelium (RPE). Between these two layers a space may be created since they are only connected together with small fibers and cellular adhesion. The photosensitive rods and cones stick down in the microvilli which projects from the RPE. This creates a loose connection which our sight depends upon. [2]
A rhegmatogenous retinal detachment in the upper wavy segment. (2)
Retinal breaks may occur due to vitreous degeneration and subsequent retinal traction, fluid from liquified vitreous humor mixed with chamber fluid could accumulate subretinally in this potential space. This creates a rhegmatogenous (Greek, rhegma = rupture / tear) retinal detachment. [3]
Retinal detachments are hazardous because the RPE no longer supplies the rods and cones with nutrients. The vision is threated, and the detachment can progress and involve the macula, leading to severe visual impairment [4]
Rhegmatogenous retinal detachments are relatively rare. The incidence of RRD in Sweden is 1000-2000 cases per year. The presentation of RRD varies greatly and range from mild, with a single break and focal detachment, to multiple and large ruptures with total detachment, including the macula. GRT are on the far end of this spectrum. These are even more rare with only 15-30 cases per year. The technical and surgical progress in treating GRT has improved single surgery success rate, visual acuity, and decreased the frequency and severity of
complications. [5]
There are seven centers that treat GRT in Sweden today. One of these is at USÖ in Örebro. The USÖ center treats patients from six different regions: Örebro, Sörmland, Västmanland, Gävleborg (Hälsingland), Värmland and Dalarna. Therefore, a significant number of operations are performed on patients from other regions than Örebro.
Optical coherence tomography (OCT) of rhegmatogenous retinal detachment. Notice the separation of the neurosensory retina from the RPE to the right. (2)
7 Giant retinal tears
Giant retinal tears (GRT) are defined as a rupture or tear in the retina of 90° or more. [6]
Who are affected by giant retinal tears?
The majority of cases are idiopathic, however research points to a few risk factors. Men are more often affected than women. This may be explained by their greater risk for ocular trauma. The mean age is around 40 years. A study “Risk factors for giant retinal tears” showed that risk factors include trauma, high myopia, aphakia, pseudophakia, and young age. The most important being age. [6] [7]
Why do they occur?
The reason giant retinal tears occur is still not completely understood. A simple explanation may be: liquefaction of the central vitreous body, combined with condensation of its edges, leads to traction of the vitreous base, which gives a tear in the underlying neuroretina. Patients with hereditary syndromes affecting connective tissue such as: Ehlers-Danlos syndrome and Sticklers syndrome are at increased risk. Patients with high myopia have thinned retinal edges, which may increase the risk for breaks. [7]
A giant retinal tear with a folded retinal flap. (8)
Proliferative vitreoretinopathy
The most common and feared complication of retinal surgery is proliferative
vitreoretinopathy (PVR). Currently there does not exist an effective treatment to cure PVR. It is in every surgeons interest to minimize it from happening.
PVR grade A-C. [8]
The neuroretina adheres weakly to the underlying retinal pigment epithelium. When separated the supply of oxygen from the choroid is impaired with the increased distance to the
neuroretina. The absence of oxygen leads to necrosis of the inner photoreceptor layer. This stimulates an inflammatory response with proliferation of Müller cells.
Fibroblasts is thought to produce the collagen, which forms membranes on the inner and outer surfaces of the retina. The most common form is the epiretinal membranes. Surgical peeling can get rid of the membranes, however this is complicated and not always successful. [9]
Process
Retinal detachment often comes along with contraction and micro trauma of the retina. This leads to activation of glia which releases cytokines and ATP. RPE cells migrate towards the
9 gradient into the subretinal space and vitreous. Together with glia RPE cells de-differentiate and adhere to epi- and endoretinal surfaces. The cells begin synthesizing collagen, which builds a membrane.
When the retina is reattached during surgery the uveoretinal barrier breaks down. This allows monocytes and leukocytes to enter the vitreous. The monocytes mature into macrophages which stimulate the proliferation of fibroblasts.
Finally, the mature membrane is contractable which gives the characteristic star folds in retinal visualization. [9]
Risk factors
The risk factors for PVR can be separated into three categories: preoperative, during operation and adjuvant treatment. “Pre-operative risk factors include the existence of large retinal tears, a longstanding retinal detachment, vitreous hemorrhage, aphakia, pseudophakia, trauma, and choroidal detachment”. [9] During operation an incomplete vitrectomy, cryotherapy or excessive laser coagulation could increase the risk for PVR. [9]
Epiretinal membranes
Just like PVR, it is though that fibroblasts produce collagen, which creates membranes on the retina. Epiretinal membranes can be seen as a mild form of PVR. They often lead to impaired visual acuity. However, they are relatively easily treated surgically, by peeling the epiretinal membrane off the retinal surface. The risk factors include
intraocular surgery, retinal tears and detachments. Therefore, they may occur before and after retinal surgery. [10]
Treatment of GRT
This rare condition still poses a great challenge to the surgeon. Despite the advancement of surgical instruments and techniques. Small sample sizes, differences in the study population and surgical techniques, makes it difficult to compare the available studies. Therefore, the best treatment of GRT is mostly based on clinical experience and skill. [11]
Epiretinal membranes with the characteristic shiny appearance. (12)
The attachment rate has increased from 58-94% since the introduction in the 1990s of
perfluorocarbon liquids (PFCL), improved intravitreal maneuvers and instruments. [7] PFCL has the ideal characteristics for retinal surgery: as it is heavier than water, has low viscosity which makes injection and removal through small gauge instruments easier, as well as being immiscible with water and blood. [12]
Today, the methods used are laser photocoagulation, pars plana vitrectomy, silicone oil or gas tamponade. The gas is naturally absorbed, but the oil is not, and has to be removed surgically. Residual oil increases the risk for elevated IOP. If the pressure is not controlled with
medication or surgery, it may lead to glaucoma. A chronic disease with increased IOP and progressive deterioration of VA and visual field. [7]
The vitreous has to be removed to access the retina. This increases the risk for postoperative cataract formation which is often caused by pars plana vitrectomy (PPV). (8) Proliferative retinopathy is a late complication, and since it cannot be handled with drugs, it leads to reoperation.
Patients who have suffered GRT are at higher risk for developing GRT in the fellow eye. They are usually offered prophylactic treatment in the healthy eye where the retina is anchored with 360° laser photocoagulation. (9)
11
Aim
The purpose of this study is to compare the postoperative results and complications of GRT with a mild type of RRD.
Material and method
Study design
This study is a retrospective cohort study with 36 patients in total. Between 2013-2017 USÖ operated 21 patients for GRT. With three excluded GRT patients the total number is 18. These patients have been matched to 18 patients with mild RRD.
Method
The patients with RRD are identified by diagnosis code H33.0, combined with the KVÅ-code for vitrectomy. According to the inclusion and exclusion criteria below, patients with mild RRD were selected.
Inclusion criteria
Originally the inclusion criteria were the same gender and age ± 3 years. The patients who did not participate in the study had to be replaced. However, due to a limited sample of patients who fulfill the requirements for mild RRD this could not be done. The inclusion criteria were changed to: ± 9 years and with no respect to gender.
Exclusion criteria
Patients with diabetes type I and II are excluded due to the risk for developing diabetic retinopathy. Those with long-standing retinal detachments, macular hole detachment, large retinal ruptures, or more than two ruptures are also excluded.
Material
Visual acuity
There are several ways to measure visual acuity (VA). The most common way to describe VA is in decimal or Snellen. However, these are unprecise when used in research settings.
LogMar has the advantage of a linear progression, which makes comparisons of VA possible. Due to the design a smaller value indicates better visual acuity, the value 0.0 is considered perfect vison. The values 0.3 and 1.0 are special and used to compare GRT with RRD. 0.3 being the upper limit for a category B driving license, and 1.0 is the lower limit for legal blindness. [13] [14]
Stenopeic glasses with pinholes of 1 millimeter may be used test visual acuity. However, the result is of no use outside the clinic. Stenopeic holes are only used during testing and not as a permanent device for visual improvement. (3)
The functional success is defined as a sight LogMAR 1.6 and better.
Surgical results
The result of the surgery is evaluated with four parameters:
1) Anatomical success: anatomical success is when the retina adheres fully after surgery. Single surgery success means one operation is needed. If there are redetachments, the number of reoperations is noted.
2) Visual acuity: the visual acuity is compared pre- and postoperative at least six to twelve months after surgery. However, in some cases, after up to 4 years. Visual acuity is converted from decimal and Snellen to LogMAR.
3) Glaucoma: the patient is considered to have glaucoma if treated with pressure controlling medication after the last control. Surgical treatment of glaucoma do also confirm the diagnosis.
4) Residual silicone oil: presence of residual drops after oil evacuation, or absence of evacuation.
Postoperative complications
There are two types of postoperative complications:
1) Epiretinal membranes: the presence of pre- and postoperative epiretinal membranes are noted.
2) PVR: the presence and grade of PVR is noted. USÖ uses the classification from 1983. The same classifications is used to assign a grade to a patient based on key words from the journals. [15] The terminology from newer classifications has to be converted to the corresponding grade in the old.
13 The classification of PVR by the Retina Society Terminology Committee. [16]
Statistical analysis
The analyzes were made in SPSS by IBM, version 25. The continuous, non-normal distributed variables, pre- and postoperative visual acuity, and months to follow up in LogMAR were analyzed by a Wilcoxon Signed-Ranks test. The nominal variables, first operation success, number of reoperations, glaucoma, residual oil and presence of pre- and postoperative epiretinal membranes were analyzed by McNemar’s test. The ordinal variables, pre- and postoperative PVR were analyzed by a sign test. P-values of 0.05 or less are
considered as significant.
Ethical discussion
The participants are anonymous, and no data is presented which may be used to expose a patients identity.
Results
With the purpose of finding differences in postoperative results and complications, the journals for GRT and RRD patients were examined. The findings are presented below in two tables and three figures.
Table 1. The postoperative results for GRT and RRD compared, with p-value and significance.
Table 1 presents the postoperative results for GRT and RRD. The first operational anatomical success is higher in GRT (83.3%) than RRD (72.2%). The number of reoperations is higher in RRD (27.8%) compared to GRT (16.7%). However, after exclusion of an RRD outlier the difference is lowered, but still higher in RRD (24.5%) than GRT (17.6%). Glaucoma is more common in GRT (22.2%) than RRD (0%). So is residual oil, GRT (27.7%) compared to RRD (5.6%). The mean preoperative visual acuity is better in RRD (0.33) than GRT (0.54).
However, the difference is smaller after surgery, RRD (0.24) compared to GRT (0.41). The mean number of months to follow up is higher in RRD (15.00) compared to GRT (12.78).
GRT N = 18 RRD N = 18 Difference P (Z) Significant
First operation anatomical success, n (%) 15 (83.3) 13 (72.2) 11.1% 0.021 Yes
Number of reoperations N = 18, n (%) N = 17, n (%) (excluding outlier) 3 (16.7) 3 (17.6) 5 (27.8) 4 (24.5) 11.1% 6.9% 0.687 0.031 No Yes Glaucoma, n (%) 4 (22.2) 0 22.2% 0.000 Yes
Residual oil, n (%) 5 (27.7) 1 (5.6) 22.2% 0.002 Yes
Visual acuity
Preoperative, mean, median (SD) Postoperative, mean, median (SD) Months follow up, mean, median (SD)
0.54, 0.20 (0.63) 0.41, 0.25 (0.35) 12.78, 12.00 (6.71) 0.33, 0.20 (0.20) 0.24, 0.10 (0.31) 15.00, 9.00 (15.41) 0.21 0.17 2.22 0.25 (-1.14) 0.14 (-1.47) 0.512 No No No
15 Table 2. The postoperative complications for GRT and RRD compared, with p-value and significance.
GRT N = 18 RRD N = 18 Difference P (Z) Significant Epiretinal membrane Preoperative, n (%) Postoperative, n (%) 1 (5.6) 7 (38.9) 3 (16.7) 5 (27.7) 11.2% 11.2% 0.003 0.21 Yes No PVR Preoperative None, n (%) A, n (%) B, n (%) C, n (%) Postoperative None, n (%) A, n (%) B, n (%) C, n (%) 2 (11.1) 6 (33.3) 9 (50.0) 1 (5.6) 11 (61.1) 2 (11.1) 0 5 (27.8) 6 (33.3) 10 (55.6) 0 2 (11.2) 12 (66.7) 2 (11.1) 3 (16.7) 1 (5.6) 22.2% 23.3% 50% 5.6% 5.6% 0 16.7% 22.2% 0.035 0.453 Yes No
Table 2 presents the complications for GRT and RRD. The rate of preoperative epiretinal membranes is higher in RRD (16.7%) than GRT (5.6%). This increases after surgery in both GRT (38.9%) and RRD (27.7%), thus GRT has higher rate of postoperative epiretinal membranes. Preoperative, absence of PVR is more common in RRD (33.3%) compared to GRT (11.1%); PVR grade A is more common in RRD (55.6%) than GRT (33.3%); PVR grade B is more common in GRT (50%) than RRD (0%); and PVR grade C is more common in RRD (11,2%) than GRT (5.6%). Postoperative, absence of PVR is still more common in RRD (66.7%) than GRT (61.1%), however the difference is diminished; GRT and RRD has decreased rate of PVR grade A, both resulting in 11.1%; PVR grade B is more common in RRD (16.7%) than GRT (0%); and PVR grade C has increased in GRT (27.8), but decreased in RRD (5.6%).
Figure 1. Presenting the best corrected visual acuity (BCVA) for GRT and RRD pre- and postoperative.
Each dot represents a patient. Preoperative BCVA on the x-axis, and postoperative BCVA on the y-axis. Values below the line indicates better BCVA after surgery, the opposite for values over the line Overlapping values are separated with a small space.
Visual acuity expressed in LogMAR is better the lower the value is. Perfect vision is represented by the number 0.0. In general, visual acuity is better after surgery. However, certain patients have worse postoperative VA. For example, an RRD patient presents 0.10 preoperative and 1.0 postoperative. Despite this, the majority of patients is situated below the line, indicating better VA after surgery.
0,00 0,20 0,40 0,60 0,80 1,00 1,20 1,40 1,60 1,80 2,00 0,00 0,20 0,40 0,60 0,80 1,00 1,20 1,40 1,60 1,80 2,00 Po st op er at iv e Lo gM AR Preoperative LogMAR
17 Figure 2. Presents the distribution of PVR-grade for GRT and RRD
preoperative.
Figure 3. Presents the distribution of PVR-grade for GRT and RRD
postoperative.
The figures above illustrate the distribution of PVR in GRT and RRD pre- and postoperative. As discussed above in table 2, the number of patients without PVR increases after surgery. The difference between GRT and RRD is diminished postoperative. Aside from PVR grade C, which is more common in GRT postoperative, there are fewer cases of PVR grade A-C in both GRT and RRD after surgery.
Discussion
The purpose of this study is to compare GRT and a mild form of RRD, with respect to postoperative results and complications. Several factors with statistical significance were found. The single surgery success rate is higher in GRT, the number of reoperations is less when an outlier has been removed, the frequency of glaucoma and residual oil are higher in GRT, the frequency of preoperative epiretinal membranes is higher in RRD, and the
frequency of preoperative PVR is higher in GRT.
In this study a high anatomical success rate of 83.3% was achieved after first surgery. Other studies have shown rates between 70-90%. [6] Despite not being supported in literature, GRT has a higher single surgery success rate than RRD. The rate for RRD is relatively low, 72.2%. Which has been shown to be over 90% since the introduction of microincision vitrectomy surgery. [1]
However, these results are questionable, despite the significant p-value. The small sample size and the potential bias in matching could explain the better result for GRT. Examples of bias are: grade of myopia, a skewed selection of RRD participants, or simply due to chance. This explanation would be more probable than RRD having worse postoperative results.
Extensive preoperative PVR could explain the relatively low single surgery success rate for RRD. The preoperative PVR grade C in RRD is 11.2%. A high number compared to literature, which is between 5-10%. For GRT the rate is 5.6%, which is lower than the 11-17% presented in other studies. Preoperative PVR grade B is absent in RRD, and occurs in 50% of cases in GRT, the latter being in line with the rate of over 50% in literature. [6]
There is a large difference in the rate of preoperative PVR. 88.9% in GRT compared to 38.9% in RRD. Despite this, the postoperative frequency is almost the same, 38.9% in GRT
compared to 33.3% in RRD. This means that fewer RRD patients than GRT patients have been cured of their PVR completely. However, this cannot be proven statistically. The frequency of postoperative PVR grade C is higher in GRT than RRD, 27.8% compared to 5.6%. Maybe, this could be explained by the high rate of preoperative PVR grade B in GRT patients.
19 not reflect well in literature where the average rate of postoperative PVR in GRT is between 8-14%. [12]
Although the older classification of PVR is easier to use, there are several shortcomings. There is no distinction between anterior and posterior PVR. In addition, grade D does not reflect the severity of PVR, because the definition lacks distinction between active, where cells are proliferating, and passive PVR. The newer classification may be more precise, however it is more difficult to apply in clinical practice. [17]
Although the eventual anatomic success is 100% in both groups, the number of reoperations is higher in RRD than GRT. Five cases to three. This difference is not statistically significant. Which may be due to an RRD outlier patient with three reoperations. Therefore, this patient was excluded in statistical analysis of 17 patients, where statistical significance was achieved. Despite the difference between GRT and RRD being smaller in the new analysis, the patients with RRD still has more reoperations.
The postoperative best corrected visual acuity (BCVA) is fairly good in both groups,
however, with no statistical significance. LogMAR 0.3 or better is achieved in 56% of GRT patients, and 16.7% have 1.0 or worse. This is fairly good compared to literature where LogMAR 0.3 or better is achieved in 0-50% of cases, and 10-58% have 1.0 or worse. [18] The median postoperative BCVA for RRD is 0.1, compared to 0.3-0.4 in literature. [1] [19]
The absence of macular engagement in RRD patients in this study, could result in better vision compared to studies where macula is detached. Macular engagement in GRT could explain the difference in preoperative BCVA, illustrated by figure 1.
The difference between GRT and RRD in mean BCVA shrinks after surgery. This could be explained by higher frequency and severity of preoperative PVR in GRT. After surgery, the difference in cases without PVR is smaller, which could explain the convergence of
postoperative BCVA. Maybe, the worse postoperative BCVA in GRT could be explained by a higher rate of epiretinal membranes. 38.9% in GRT compared to 27.7% in RRD. Shunmugam et al [12] states that epiretinal membranes are one of the most common reasons for reduced vision.
However, all 36 patients achieve functional success, which can be defined as a BCVA of LogMAR 1.6 or better. The worst postoperative BCVA is 1.0 in both groups. According to a study by Idrees et al [17] anatomic and functional success are maintained long term after three years. The majority of patients in this study are not followed that long, therefore, it is unclear whether the anatomic and functional success will be maintained long term.
With a total of four cases, making up 22.2% of cases of GRT, glaucoma is significantly more common in GRT. The proportion of GRT patients who receives silicone oil is 72%. Slightly lower compared to a previous study, 75.8%, but higher than 68%, in a study from Helsinki with 80 eyes. [6] [20] With 22.2% of RRD receiving silicone oil during operation, it is used more frequently in GRT.
No data about the IOP has been extracted from the journal. Therefore, transient changes of IOP are missed. However, a temporary shift in IOP is no sign of glaucoma, which is a lifelong disease.
Strengths
According to Idrees et al [17] the majority of postoperative PVR appear within 30-45 days. In this study the patients journals cover the postoperative period well. Including 30-45 after surgery. Therefore, no cases of PVR were lost.
Weaknesses
A weakness is the small number of patients included in the study. To achieve statistical significance, a larger sample is needed for comparison of visual acuity, postoperative PVR and postoperative epiretinal membranes.
Another weakness is the subjective judgement of PVR made by the author. As well as potential bias, discussed above.
21
Conclusion
Somewhat surprisingly, the results present a higher single surgery success rate in GRT than the mild form of RRD. Compared to literature the success rate for RRD is relatively low, but the rate for GRT is among the best. However, this may be due to the small sample size and potential bias in the matching. Before surgery GRT presents with worse preoperative visual acuity and higher rate of complications. These differences seem to diminish after surgery. The exception being glaucoma, which is more common in GRT. Even if our results point to better anatomic results after surgery for GRT compared to RRD we are not postulating this is actually the correct interpretation of the data. However, we seem to have support that in our material the results of treatment of GRT seems to be as good as those for RRD. For further evaluation a prospective study could be beneficial.
Acknowledgements
I want to thank Professor Sven Crafoord for inspiring and supporting me throughout the project. A big thank you to secretary Jessica Eriksson for all the help along the way. Finally, this would not be possible without all the patients who agreed to participate in the study, thank you.
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