The graft survival evaluation after subtotal penetrating keratoplasty in the long-term postoperative period

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Abstract


Introduction. Until the 2000s, in diseases leading to corneal blindness, it was expediently to perform subtotal keratoplasty in order to provide an organ-sparing effect and restore visual functions. Such procedures were not widely spread due to a great number of problems; they were performed with extended depressurization of the eye, and had a high risk of intraoperative complications. Nowadays, many ophthalmologists face the remote consequences of subtotal keratoplasty.

Aim. The purpose is to evaluate the transplant after subtotal penetrating keratoplasty (SPK) and visual functions in the remote postoperative period.

Materials and methods. We have examined 14 patients (14 eyes), aged from 28 to 81 years, at 6-10 years after SPK. Visual acuity (VA) testing, autorefractometry and confocal microscopy (Confoscan 4) were performed.

Results. According to visual acuity testing results, patients were divided into 3 groups: 1st group with high VA (more than 0.2 – in 7.2% of patients), 2nd group with medium VA (from 0.2 to 0.005 – in 21.4% of patients), and 3rd – low VA (less than 0.005 – in 71.4% of patients). Before the SKP, VA was 0.004-0.7. After the SKP, the indices varied from light sensation with correct light projection to 1.0. High rate was in 21.5%, medium – in 35.7%, low in 42.8% of cases. According to autorefractometry data, the cylindrical component was in average 6.5 ± 3.0. Most often, astigmatism was revealed in the low (up to 3) and high degree (more than 6). According to confocal microscopy data, the average density of endothelial cells was 1700 ± 50 cells/mm2.

Conclusion. More than a half of patients has preserved good visual functions and a transparent transplant at 6-10 years after the SKP, and this significantly improves the quality of patients´ life.


Introduction

In 2004, the estimated number of people with visual impairment and blindness in the Russian Federation reached 500,000, with 18% of them having corneal disorders [8, 10]. According to the WHO, corneal blindness is the third most common cause of blindness after lens diseases [3]. Corneal blindness is a significant social problem because it affects the working age population. Approximately 5.9% of the adult population in Russia and 4%–5% of the adult population worldwide suffer from corneal blindness; approximately 9% are disabled because of blindness [9]. The most frequent diseases leading to corneal blindness include keratoconus (33%–54%), corneal scarring and opacities (21%), corneal ulcers (9%), primary and secondary corneal dystrophy (6%), and postoperative bullous keratopathy and herpetic keratitis (12.3%) [1, 5]. There is an increasing need for rehabilitation of patients with end-stage pseudophakic or aphakic bullous keratopathy. Until the beginning of the 21st century, subtotal penetrating keratoplasty (SPK) was considered as the most appropriate treatment method for the recovery of visual functions in such patients. SPK includessimultaneous removal of retrocorneal and epilens membranes, separation of the anterior and posterior synechiae, and removal of cataract [12, 13].

The most common SPK complication in the early postoperative period is corneal graft failure caused by inflammation, secondary glaucoma, severe xerosis, and systemic autoimmune diseases. Several studies have demonstrated that graft failure occurs in <10% of SPK cases [7, 6, 14].

According to the literature, successful corneal engraftment during the first year postoperatively is observed in 95% of patients with keratoconus, 82% with posttraumatic corneal scarring, 75% with bullous keratopathy, 72% with keratitis, and 11%–38% with burn leukomas [4, 12].

High graft survival rates post SPK were observed in patients with keratoconus and Fuchs’ corneal dystrophy. Patients with aphakia showed low graft survival rates post SPK [16].

SPK is being widely used globally, and many ophthalmologists now have to deal with the long-term outcomes of the surgery in their routine clinical practice.

The aim of this study was to assess the long-term outcomes of SPK through the evaluation of visual functions and corneal graft transparency.

Materials and Methods

We examined 14 patients (14 eyes) who underwent SPK 6–10 years ago (2007–2011). The study population comprised nine males and five females aged 26–81 years.

Prior to SPK, all patients complained of poor vision.

The most common indications for SPK were stage 3 leukomas (according to the Filatov–Bushmich classification) and stage 3–4 keratoconus (according to the Amsler classification) (Table 1).

 

Table 1. Patients distribution according to nosological forms

Таблица 1. Распределение больных по нозологическим формам

Disease

Number of patients, abs. (%)

Vascularized leukoma

5 (35.7)

Chronic progressive keratoconus

4 (28.6)

Acute keratoconus

1 (7.1)

Pseudophakic bullous keratopathy

1 (7.1)

Corneal ulcer with perforation

2 (14.4)

Endothelial-epithelial corneal dystrophy

1 (7.1)

 

A majority of the patients presented with concomitant ocular pathology that ultimately affected the SPK outcomes (Table 2). Some patients simultaneously underwent phacoemulsification, anterior vitrectomy, or intraocular lens implantation.

 

Table 2. Concomitant ophthalmic pathology

Таблица 2. Сопутствующая офтальмологическая патология

Concomitant ocular pathology

Number of patients, abs. (%)

Glaucoma

1

Pseudophakia

1

Aphakia

2

Immature cataract

2

Hemophthalmus

3

 

Results

All patients underwent autorefractometry, visual acuity testing, biomicroscopy with a slit lamp, and microscopic examination of endothelial cells using a confocal microscope Confoscan 4 (Nidek Technologies, Japan).

Although this microscope allows real-time in vivo examination of all corneal layers, the presence of corneal opacity may hamper endothelial cell visualization.

The density of epithelial cells in the late postoperative period post SPK varied between 1,492 and 1,942 cells/mm2, with a mean density of 1,700 cells/mm2. It is well-known that the loss of endothelial cells is unavoidable in keratoplasty [15, 16]. However, our patients suffered only 10%–15%loss of endothelial cells during 2–10 years post SPK.

The level of cell pleomorphism varied between 21.9% and 70%, with a mean value of 34.7%, whereas the level of polymegethism varied between 21.3% and 57.8%, with a mean value of 46.1%.

Table 3 illustrates the outcomes of confocal microscopy examination of 12 patients; in the remaining two patients, we failed to obtain a reliable visualization of the endothelial cells. We divided the patients into the following three groups based on the results of visual acuity testing: patients with high (>0.2), medium (0.2–0.005), and low (<0.005) visual acuity (Table 4). Prior to SPK, visual acuity was between 0.004 and 0.7. Post SPK, it varied from light perception with correct projection (one patient) to 1.0.

 

Table 3. Endothelial cell density after SPK

Таблица 3. Плотность эндотелиальных клеток (ПЭК) после субтотальной сквозной кератопластики

Patient

Postoperative period (years)

Density of epithelial cells (cells/mm2)

Pleomorphism (%)

Polymegethism (%)

1

7

1524

21.9

21.3

2

4

1799

70

28

3

2

1467

26.6

31.2

4

7

1535

35.4

42

5

7

1679

36

44.7

6

6

1905

54

38.3

7

10

1754

31.8

36.1

8

10

1974

27.5

65

9

6

1442

35.7

57.8

10

10

1895

27.3

57.5

11

6

1719

25.6

59.3

12

6

1930

25.0

71.9

 

Table 4. Visual acuity before and after the SPK

Таблица 4. Результаты визометрии до и после субтотальной сквозной кератопластики

Maximum uncorrected visual acuity

High (>0.2), abs. (%)

Medium (0.2–0.005), abs. (%)

Low (<0.005), abs. (%)

Prior to SPK

1 (7.2)

3 (21.4)

10 (71.4)

Post SPK

3 (21.5)

5 (35.7)

6 (42.8)

 

The results of visual acuity testing were lower than expected, which was associated with the development of postoperative astigmatism. Autorefractometry revealed that the mean cylindrical component in patients post SPK was 6.5 ± 3.0 D. Approximately 80% of patients presented with postoperative astigmatism up to 3.0 D or >6.0 D, whereas the remaining 20% of patients were diagnosed with astigmatism of 3.0–6.0 D.

In this study, two of the 14 patients (14.3%) were found to have nontransparent engraftment upon biomicroscopic examination. One among them was an 81-year-old male patient who underwent SPK for pseudophakic bullous keratopathy and developed bacterial ulcer of the cornea 1 year postoperatively. His visual acuity reduced to light perception with correct light projection.

The second patient with a nontransparent graft was an 81-year-old male who underwent SPK in 2007. One year postoperatively, he developed herpetic keratitis and anterior uveitis. Currently, he has visual acuity of light perception with correct light projection. In both patients, we were unable to evaluate the density of epithelial cells because of the opacity of the graft.

Nevertheless, a majority of the patients (n = 9) had successful corneal engraftment (Figure 2). Figure 1 demonstrates a microscopic image of the endothelial cells of a transparent graft.

 

Fig. 1. Confocal microscopy. Endothelial cell density – 1930 cells per mm2, pleomorphism – 25.0%, polymegathism – 71.9%

 

Fig. 2. Transparent transplant engraftment in a patient operated for chronic progressive keratoconus

 

Three patients had nontransparent engraftment because of keratitis and eyeball contusions in the early postoperative period. Figures 3 and 4 demonstrate nontransparent engraftment.

 

Fig. 3. Semi-transparent transplant engraftment in a patient with keratitis in the early postoperative period

 

Fig. 4. Semi-transparent transplant engraftment in a patient operated for chronic progressive keratoconus

 

Nonetheless, more than 50% of the patients expressed their satisfaction with the outcomes of SPK 10 years postoperatively.

Discussion

For many decades, SPK has been considered as an effective method for the treatment of irreversible corneal changes. Our results suggest that SPK achieves good functional outcomes in more than 50% of the patients. We found that the long-term graft survival rate post SPK was quite high. In some patients (42.8%), visual acuity was lower than expected, which is associated with the need for additional surgical interventions, graft diseases, or inflammatory complications.

In addition, postoperative astigmatism contributes to decreased visual acuity. Several patients with astigmatism, which could not be corrected with eyeglasses, were recommended excimer laser correction or scleral lenses.

The high density of epithelial cells with their insignificant loss postoperatively and the moderate morphological changes in the corneal epithelium 10 years post SPK suggest satisfactory graft survival.

Conclusions

  1. Our findings suggest that visual acuity remains satisfactory in more than 50% of the patients 10 years post SPK.
  2. Visual acuity was found to be lower than expected in patients with successful corneal engraftment, which can be attributed to postoperative astigmatism (up to 6.5 D).
  3. In addition, the 10-year graft survival rate post SPK was 64.3% and a majority of the patients showed high density of epithelium (1,700 cells/mm2).
  4. Changes in the graft endothelium depend on the concomitant ocular pathology and postoperative complications.

Nigina N. Berdieva

Academician I.P. Pavlov First St. Petersburg State Medical University

Author for correspondence.
Email: alsabvel@mail.ru

Russian Federation, Saint Petersburg

student. Medical Faculty

Eleonora V. Shapovalova

Academician I.P. Pavlov First St. Petersburg State Medical University

Email: pousse2008@mail.ru

Russian Federation, Saint Petersburg

student. Medical Faculty

Inna A. Riks

Academician I.P. Pavlov First St. Petersburg State Medical University

Email: riks0503@yandex.ru

Russian Federation, Saint Petersburg

MD, PhD, assistant. Ophthalmology department

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