KEY CONCEPTS

• •
  

  Both anterior and posterior chamber phakic intraocular lenses (PIOL) are safe and effective options for visual rehabilitation in patients with stable, mild-moderate keratoconus (KC).

  
  
• •
  

  In cases of progressive KC, corneal cross-linking (CXL) should be performed to halt the progression of the disease, prior to considering PIOL implantation. The timing between CXL and PIOL implantation should be individualized, usually after confirmed topographic and refractive stabilization.

  
  
• •
  

  Intrastromal corneal ring segment (ICRS) implantation may be combined with PIOL implantation for correction of moderate-high refractive error in eyes with nonadvanced KC and significant irregular astigmatism.

  
  
• •
  

  Phakic IOLs are safe and effective in correcting postkeratoplasty ametropia in KC eyes in the mid/long term.

Introduction

The two most important goals in the management of keratoconus (KC) are halting disease progression and visual rehabilitation. Visual rehabilitation in KC patients is a challenge, usually requiring a stepwise approach: first stabilizing the disease if progression is present; then regularizing the corneal shape; and, finally, correcting the spherocylindrical error. ^, Phakic intraocular lenses (PIOLs) have been increasingly used for the correction of moderate-high levels of myopia and regular astigmatism in KC eyes, and reduction of the refractive difference between both eyes. By reducing the degree of anisometropia, PIOLs improve binocularity, as retinal images become more similar. In addition, PIOLs provide a larger image size compared with spectacles. Finally, PIOLs in KC eyes do not affect the corneal surface, unlike other strategies such as intrastromal corneal ring segments (ICRSs) or photorefractive keratectomy (PRK).

Studies of PIOLs in eyes with KC include anterior chamber (AC) iris-claw PIOLs and posterior chamber (PC) PIOL ( Table 30.1 ). In appropriately selected patients with KC, PIOL implantation has shown a good efficacy index (postoperative uncorrected distance visual acuity [UDVA]/preoperative corrected distance visual acuity [CDVA] ratio), as well as a good safety index (postoperative CDVA/preoperative CDVA ratio), with low rates of complication ( Tables 30.2 and 30.3 ). ^{, ,} Iris-claw AC PIOLs (Artisan and Artiflex, Ophtec BV, Groningen, The Netherlands) are fixated anteriorly to the iris by enclavation, effectively correcting spherocylindrical error. In our experience, advantages of the iris-claw concept include centration, fixation, positioning in the AC, and respect for the anatomy of the anterior segment. ^, We use Toric Artiflex in most cases of stable, mild-to-moderate KC, and only consider the polymethyl methacrylate (PMMA) Artisan PIOL if spherical power is less than −14.50 D and/or cylinder power is greater than 5.00 D. Aiming for emmetropia or slight undercorrection results in significant improvement of cylinder and manifest refraction, as well as significant improvement in both UDVA and CDVA in eyes with stable, nonadvanced KC. Most patients gain ≥1 lines of CDVA ( Table 30.2 ). The Visian ICL (EVO Visian ICL, STAAR Surgical Co., Monrovia, CA, USA) is a PC PIOL with a superior postoperative visual performance and with high safety and effectiveness profiles for the correction of moderate-high ametropia. Long-term visual and refractive stability has been demonstrated after implantable collamer lens (ICL) implantation in eyes with stable, mild-to-moderate KC, with most eyes reaching UDVA ≥20/40, and a high percentage of eyes reaching UDVA in the 20/25 to 20/20 range (see Table 30.3 ).

Patient Selection

Potential candidates for PIOL implantation include patients with stable or stabilized mild-moderate KC who have moderate-high ametropia and who do not have satisfactory best-corrected visual acuity (BCVA) ( Fig. 30.1 ). The term “satisfactory BCVA” has been adopted to differentiate patients who achieve good corrected vision but are unable to tolerate or wear optical correction for long periods of time, including contact lenses (CL). Exclusion criteria for PIOL implantation include low endothelial cell counts (ECC), according to patient age and for each PIOL; short AC depth; abnormal iris or pupil function; and a scotopic pupil size >6.00 mm ( Box 30.1 ). Preoperative CDVA should be ≥20/50, as keratoplasty may achieve superior visual outcomes in these cases. It has been suggested that KC patients with ECC of 2000 cells/mm ² or slightly below may still be candidates for PIOL implantation, as a measure to delay or prevent the need for penetrating keratoplasty (PK). However, with the increasing experience with deep anterior lamellar keratoplasty (DALK) and given the advantages of DALK over PK in KC, our group usually excludes patients with ECC <2300 cells/mm ² for PIOL implantation, as these patients may fare better with DALK. In cases of documented progression, halting disease progression must be addressed before considering PIOL implantation either by corneal cross-linking (CXL) or by corneal transplantation (DALK or PK) (see Chapter 8). Commonly used criteria to determine progression include clinical and topo-tomographic parameters ( Box 30.2 ); consistent changes over two consecutive examinations spaced 6 to 12 months apart are needed to determine progression. However, no clear definition of progression is available.

Proposed decision tree for the management of keratoconus. CDVA, Corrected distance visual acuity; CL, contact lens; CXL, corneal cross-linking; DALK, deep anterior lamellar keratoplasty; ECC, endothelial cell count; ICRS, intrastromal corneal ring segments; KC, keratoconus; PIOL, phakic intraocular lens; PK, penetrating keratoplasty; PRK, photorefractive keratectomy; RGPCL, rigid gas-permeable contact lens; RLE, refractive lens exchange; SE, refractive spherical equivalent; TP, thinnest point in corneal pachymetry; VA, visual acuity. (Adapted from Güell et al . and Gore et al . )

In patients with stable, nonadvanced KC and with low CDVA and/or high irregular astigmatism, ICRS implantation should be considered before PIOL implantation. Although a number of tomographic indices allow quantification of irregular astigmatism, clinically significant irregular astigmatism is considered if CDVA with spectacles is ≤1 Snellen line worse than CDVA with rigid gas-permeable CL. ^,

Combined Corneal Cross-Linking Plus Phakic Intraocular Lens Implantation

In progressive KC, PIOL implantation alone would not provide stable refractive results in the mid/long term. CXL is the only technique with proven effect on halting progression of KC. CXL can be combined with other treatments for visual rehabilitation, including sequential or simultaneous CXL + topography-guided PRK (Athens protocol), combined transepithelial phototherapeutic keratectomy + CXL, combined CXL + ICRS, and combined CXL + PIOL.

Combined CXL + PIOL implantation is a safe and effective strategy in eyes with progressive KC with moderate-high refractive error, regular astigmatism, and good CDVA, providing stabilization of the cone, as well as visual and refractive improvements comparable to those of non-KC eyes for up to 3 years after surgery ( Table 30.4 ). ^, However, there is still no consensus on the appropriate interval between CXL and PIOL implantation. The minimum interval between CXL and PIOL implantation should be individualized. In our experience, after a minimum of 3 months following CXL, we consider PIOL implantation once both manifest refraction and tomography scans are stable at two different time points at least 2 months apart ( Fig. 30.2 ). Both Izquierdo et al. and our group have found that combined CXL + iris-claw PIOL implantation significantly improved UDVA and CDVA, with high predictability of the refractive error in addition to a good safety profile. ^, Combined CXL + ICL implantation has shown similar outcomes in terms of effectiveness and safety in the long term. A recent study showed that the combined Athens protocol and PIOL implantation was also safe and effective.

TABLE 30.4

Reported Outcomes and Complications of Combined Corneal Cross-Linking and Phakic Intraocular Lens Implantation in Keratoconus

Preoperative Data

Post-CXL, Pre-PIOL Data

Author

Publication (Year)

Eyes (n)

PIOL

UDVA (logMAR)

CDVA (logMAR)

Sphere (D)

Cylinder (D)

RSE (D)

K max /K min (D)

ECC (cells/mm 2 )

CDVA

RSE (D)

Cylinder (D)

K max /K min (D)

ECC (cells/mm 2 )

Time Between CXL and PIOL (Months)

Izquierdo et al.

2011

11

Artiflex

1.40 ± 0.40

0.14 ± 0.06

−5.70 ± 1.21

−1.32 ± 0.86

−6.36 ± 1.09

48.20 ± 3.47 / 43.94 ± 2.92

2759.6 ± 159.8

1.16 ± 0.46

−5.90 ± 1.14

−1.30 ± 0.67

46.93 ±3.49 / 44.17 ± 1.64

2739.1 ± 157.0

6

Kymionis et al.

2011

1

Visian ICL

CF

0.7

−10

−5

−12.5

63.51 / 57.24

N/R

0.5

−14.25

−4.5

61.72/57.17

N/R

12

Güell et al.

2012

17

Artiflex

N/R

0.10 ± 0.09

−5.25

−3.54 ± 1.39

−6.99 ± 3.20

46.11 ± 1.17/43.29 ± 1.17

2847

0.10 ± 0.09

−6.93 ± 3.09

−3.51 ± 1.93

46.17 ± 1.26 /43.60 ± 1.26

2868

3.9 ± 0.7

Fadlallah et al.

2013

16

Visian ICL

1.67 ± 0.49

0.15 ± 0.06

−8.56 ± 3.90

2.64 ± 1.28

−7.24 ± 3.53

52.59 ± 4.79 / 46.00 ± 3.58

N/R

0.15 ± 0.06

−7.16 ± 3.58

2.45 ± 1.19

51.33 ± 4.41 / 46.02 ± 2.99

N/R

6

Shafik Shaheen et al.

2014

16

Visian ICL

N/R

0.56 ± 0.13 (decimals)

−6 ± 4.0

−5 ± 1.5

−8.5 ± 4.0

N/R

2850

N/R

N/R

N/R

N/R

N/R

12

Antonios et al.

2014

30

Visian ICL

1.57 ± 0.50

0.17 ± 0.08

−8.37 ± 3.89

2.95 ± 1.40

−6.96 ± 3.68

53.08 ± 5.17 / 46.52 ± 3.72

N/R

0.15 ± 0.06

−6.81 ± 3.48

2.74 ± 1.33

52.01 ± 4.87/46.23 ± 3.21

N/R

6

Doroodgar et al.

2017

40

Visian ICL

1.28 ± 0.37

N/R

N/R

N/R

N/R

N/R

N/R

0.19 ± 0.11

−7.55 ± 4.22

−3.57 ± 1.56

N/R

2426.6 ± 107.6

≥12

Emerah et al.

2019

14

Visian ICL

0.77 ± 0.20

0.18 ± 0.10

−3.7 ± 1.9

−2.3 ± 1.6

−4.48 ± 2.25

N/R

N/R

71.4% of eyes had CXL before ICL implantation

Postoperative Data

Follow-Up (Months)

UDVA (logMAR)

CDVA (logMAR)

Spherical Error (D)

Cylinder (D)

Final RSE (D)

%RSE within ± 0.50 D

%RSE within ± 1.00 D

%eyes UDVA ≥ 20/40

%eyes gain ≥ 1 lines CDVA

%eyes loss ≥ 2 lines CDVA

%ECL

Complications

6

0.16 ± 0.06

0.04 ± 0.05

−0.27 ± 0.52

−0.91 ± 0.61

−0.727 ± 0.66

45.5%

63.6%

100.0%

63.6%

0%

3.3%

Mild haze (18.1%)

3

0.3

0.2

−0.25

−0.5

−0.5

100.0%

100.0%

100.0%

100.0%

0%

N/R

None reported

36.9 ± 15.0

0.17 ± 0.13

0.10 ± 0.09

0.06 ± 0.26

−0.62 ± 0.39

−0.22 ± 0.33

82.4%

94.1%

94.1%

30.0%

0.0%

0.1%

Mild giant cell reaction (11.7%)

12

0.17 ± 0.06

0.12 ± 0.04

−1.47 ± 0.99

1.16 ± 0.64

−0.89 ± 0.76

75.0%

87.5%

81.0%

N/R

0%

N/R

None reported

36

N/R

0.88 ± 0.18 (decimals)

0.00 ± 0.18

−0.05 ± 0.14

Final RSE < −0.25

100.0%

100.0%

81% had UDVA ≥ 20/25

N/R

0.0%

8.89%

None reported

12

0.17 ± 0.06

0.11 ± 0.05

−1.36 ± 0.94

1.03 ± 0.60

−0.83 ± 0.76

N/R

63.3%

60% had UDVA ≥ 20/30

43.0%

0.0%

N/R

None reported

48

0.11 ± 0.13

−0.14 ± 0.13

N/R

Mean change = 2.79 ± 1.78

Mean change = 7.44 ± 4.75

82.5%

97.1%

100.0%

82.5%

0.0%

≤5%

None reported

6

0.15 ± 0.10

0.15 ± 0.10

−0.20 ± 0.50

−0.60 ± 0.50

Final RSE decreased 74% from preoperative

65% of eyes within ± 0.75 D

85.0%

N/R

42.9%

0%

N/R

None reported

Only gold members can continue reading. Log In or Register to continue

Share this:

• Click to share on Twitter (Opens in new window)
• Click to share on Facebook (Opens in new window)

Related

Related posts:

1. Contact Lenses for Keratoconus
2. Differential Diagnosis of Keratoconus
3. Scheimpflug Imaging for Keratoconus and Ectatic Disease
4. Anatomy of Intracorneal Ring Segments for the Treatment of Keratoconus and Other Corneal Ectasias

Stay updated, free articles. Join our Telegram channel

Join