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 Table of Contents  
CASE REPORT
Year : 2023  |  Volume : 3  |  Issue : 1  |  Page : 38-41

Photorefractive keratectomy with collagen cross-linking in grade 2 progressive keratoconus


1 Department of Cornea, Ruby Eye Hospital, Govinda Vihar, Berhampur; Department of Cornea, Hitech Medical College, Bhubaneswar, Odisha, India
2 Department of Cornea, Ruby Eye Hospital, Govinda Vihar, Berhampur, Odisha, India
3 Department of Cornea, Capital Hospital, Rourkela, Odisha, India

Date of Submission25-Apr-2022
Date of Acceptance29-Aug-2022
Date of Web Publication20-Jan-2023

Correspondence Address:
Praveen Subudhi
Ruby Eye Hospital, Govinda Vihar, Berhampur, Ganjam, Odisha
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijo.IJO_1030_22

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  Abstract 


A 24-year-old male with slowly progressing vision loss over six months came to our hospital. On clinical evaluation, his unaided visual acuity was 3/60, which improved to 6/60 with spherocylindrical correction. His lenticular status and posterior segment were within normal limits. On Pentacam evaluation, there was gross evidence of keratoconus. Over the next two months, his Pentacam scan showed a progressive increase in keratoconic parameters. Hence, he was scheduled for topography-guided photorefractive keratectomy (PRK) with full-threshold collagen cross-linking (CXL). After PRK with CXL, the inferior cone was obliterated, providing a stable corneal surface. His unaided visual acuity at three and six months was 6/12 and 6/9p, respectively. His visual acuity remained at 6/9p at the end of 2 years.

Keywords: Collagen cross linking, hypotonic riboflavin, photorefractive keratectomy


How to cite this article:
Subudhi P, Patro S, Pattanayak S, Rao Subudhi B N, Sitaram S. Photorefractive keratectomy with collagen cross-linking in grade 2 progressive keratoconus. Indian J Ophthalmol Case Rep 2023;3:38-41

How to cite this URL:
Subudhi P, Patro S, Pattanayak S, Rao Subudhi B N, Sitaram S. Photorefractive keratectomy with collagen cross-linking in grade 2 progressive keratoconus. Indian J Ophthalmol Case Rep [serial online] 2023 [cited 2023 Feb 1];3:38-41. Available from: https://www.ijoreports.in/text.asp?2023/3/1/38/368116



Keratoconus is the most enigmatic condition of the eye. The progression of keratoconus is mostly encountered in adolescent age groups.[1] The pathology of progression is still unknown, with no evidence of a single identifiable cause.[2] Allergic conjunctivitis with recurrent rubbing of the eyes has some association with progression. Once progression sets in, it needs to be controlled as it may grossly reduce vision and may eventually lead to acute hydrops.[2]


  Case Report Top


A 24-year-old male came to our hospital with complaints of progressing vision loss. His presenting uncorrected visual acuity (UCVA) in the right eye was 6/12 and that in the left eye was 3/60. On clinical examination and slit-lamp evaluation, the right eye anterior segment and posterior segment were within normal limits. On slit-lamp evaluation of the left eye, it was observed that the patient had conical protrusion with thinning in the paracentral area. Pentacam evaluation at an interval of three months revealed signs of progression of conical protrusion, suggestive of progressive keratoconus [Figure 1]. The patient had no history of any other medical abnormalities. Blood analysis for Down's syndrome was performed, but it was negative. Subjective refraction of the patient was − 3.5 D spherical with a − 3.0 D cylinder at 160°. However, the patient's best-corrected visual acuity (BCVA) was 6/60.
Figure 1: (a) Topometric parameters of the cornea at the time of presentation. (b) Topometric maps after 3 months with signs of progression of keratoconus

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Intraoperative procedure

The patient was scheduled for topography-guided photorefractive keratectomy (PRK) with collagen cross-linking (CXL). Topography-guided PRK was performed by exporting topography maps to the workstation through a topo link. Manual entry of keratometric data was performed, followed by the entry of the pachymetric data of all the quadrants of the cornea. Sagittal data maps were evaluated, and five similar-looking maps were included to create an accurate ablation profile followed by an assessment of Zernike numerical aberrometry. Higher-order aberration (HOA, z4) and defocus (z12) were matched by dividing the z12 component by 1.51, and the resulting number was added to the spherical component of the refractive correction. Here, we added − 0.28 to the spherical correction of − 0.25. The total amount of corneal surface alteration performed was − 0.53 sphere and − 2.50 D cylinder at 160°. The optical zone of correction was 6 mm, and the residual stroma after ablation was 360 mm [Figure 2]. To a de-epithelialized cornea, photoablation was performed with excimer laser, followed by application of 0.45% riboflavin drops in two-minute intervals for 15 minutes to increase the corneal thickness. As the corneal thickness increased beyond 400 microns as assessed by pachymetry, 0.9% riboflavin drops were administered every two minutes for the next 15 minutes. Next, exposure to a UVA light bearing a wavelength of 365 nm was applied to the photosensitized corneal surface with an intensity of 9 mW/cm2 for 10 minutes, amounting to a total of 5.4 millijoules of energy. Finally, the surface of the cornea was washed with copious saline irrigation, and a bandage contact lens was placed.
Figure 2: Demonstration of ablation profile and amount of refractive error corrected

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Postoperative assessment

The patient had significant discomfort with chemosis and congestion on the first postoperative day. However, the inflammation began to subside with topical anti-inflammatory therapy, but there was a persistent epithelial defect for two weeks. The patient had a bandage contact lens for the same period. After careful medical treatment with close follow-up, the epithelial defect healed.

Corneal topography post-procedure

Mean keratometry after three months showed a reduction of 5.3 D compared to its preoperative measurement. The corneal surface appeared more regular with an absolute decrease in inferior steepening. The index of surface variation and index of height asymmetry parameters also showed significant reductions of 40 and 20 units, respectively. Additionally, the index of height decentration was also reduced to 0.016 (normal range). Furthermore, the index of vertical asymmetry and the index of height decentration were significantly reduced. However, there was no change in the curvature of the posterior corneal surface [Figure 3]a. Regression of keratoconus and worsening of Pentacam parameters such as inferior steepening was noted at 12 months [Figure 3]b; however, his unaided visual acuity was 6/12. Nonetheless, his Pentacam parameters showed marginal improvement at the end of 24 months with no signs of further progression, and his final unaided visual acuity recorded was 6/9p [Figure 3]c.
Figure 3: (a) Postoperative topometric map showing obliteration of inferior cone with significant reduction in keratometry in the second month. (b) Postoperative topometric map at 12 months showing regression of keratoconus. (c) Postoperative topometric map at 24 months showing stable parameters with mild improvement of keratometry from 12 months post operation

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  Discussion Top


With our understanding of the pathogenesis of keratoconus, newer treatment modalities and algorithms are being tried to stabilize the cornea to avert progression and provide a better quality of vision.[3] Surface ablation procedures are a noteworthy introduction for the management of progressive keratoconus in addition to collagen cross-linking. The corneal surface in keratoconus is very irregular, with peripheral flattening and a very steep paracentral area. The patient's poor vision is basically due to high astigmatism, and the quality of images perceived is not clear for near and distance. PRK not only normalizes the corneal surface but also creates a tough superficial fibrous scar that prevents further weakening of the cornea. PRK in combination with collagen cross-linking helps to create stronger covalent bonds between the corneal lamellae, making the cornea tougher, more regular, and rigid.[4] A maximum of 50 microns is utilized to normalize the corneal surface while keeping the spherical power untouched.[5] After collagen cross-linking, the cornea assumes a hyperopic shift due to collagen shrinking, thus neutralizing residual myopia.[6] This patient responded to the procedure in a predictable manner, and the patient had a good visual outcome in comparison to his preoperative vision and obtained long-term stability.


  Conclusion Top


Progression of keratoconus is an alarming complication leading to highly aberrated and irregular cornea, providing poor quality of vision. Hence a combination of photorefractive keratectomy with collagen cross-linking (Athens protocol) not only provides a good quality of vision but also creates a tough and smooth anterior corneal surface which prevents long-standing complications of progressive keratoconus such as acute hydrops. To the best of our knowledge, this is the first case to be reported from this region having a clear documentation of the topographic progression of the cornea managed successfully with topography-guided PRK with CXL. However, accurate treatment protocols are deemed necessary for adopting this management into regular clinical practice.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Rabinowitz YS. Keratoconus. Surv Ophthalmol 1998;42:297-319.  Back to cited text no. 1
    
2.
Mas Tur V, MacGregor C, Jayaswal R, O'Brart D, Maycock N. A review of keratoconus: diagnosis, pathophysiology, and genetics. Surv Ophthalmol 2017;62:770-83.  Back to cited text no. 2
    
3.
Tan DT, Por YM. Current treatment options for corneal ectasia. Curr Opin Ophthalmol 2007;18:284-9.  Back to cited text no. 3
    
4.
Bardan AS, Lee H, Nanavaty MA. Outcomes of simultaneous and sequential cross-linking with excimer laser surface ablation in keratoconus. J Refract Surg 2018;34:690-6.  Back to cited text no. 4
    
5.
Chen X, Stojanovic A, Xu Y, Zhou W, Raeder S, Enayati S, et al. Medium- to long-term results of corneal cross-linking for keratoconus using phototherapeutic keratectomy for epi-thelial removal and partial stromal ablation. J Refract Surg 2017;33:488-95.  Back to cited text no. 5
    
6.
Padmanabhan P, Rachapalle Reddi S, Rajagopal R, Natarajan R, Iyer G, Srinivasan B, et al. Corneal collagen cross-linking for keratoconus in pediatric patients-long-term results. Cornea 2017;36:138-43.  Back to cited text no. 6
    


    Figures

  [Figure 1], [Figure 2], [Figure 3]



 

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