Dr. Sandhya Jeria, Dr. Prabhat Nangia, Dr. Vinay Nangia
Suraj Eye Institute, Nagpur
Case description
A male, 17 years of age, came to us with chief complaints of diminution of vision in left eye (OS) since 2 years. Diminution of vision was gradual in onset and progressive in nature. Patient had a history of recurrent cold and cough which may have been due to respiratory allergy, and a history of eye rubbing. On examination uncorrected visual acuity was 6/6, N6 in right eye (OD) and 6/36, N12 in the left eye. On auto refraction, values were -3.25DSph/ +1.25DCyl @121° in the right eye and -10.50DSph/ +4.25 DCyl @78° in left eye. However, there was no improvement with glasses. Slit-lamp examination showed central corneal thinning, Vogt’s striae, prominent corneal nerves and Fleischer ring in OS. Anterior segment examination of right eye was within normal limits. Intraocular pressure by Goldmann applanation tonometry was 13 mmHg in OD and 10 mmHg in OS. Fundus examination of both eyes was within normal limits. Anterior Segment Optical Coherence Tomography (AS-OCT) was performed.d ischemic heart disease, had undergone coronary artery bypass surgery, and was on anticoagulants.
Fig.1(a): Left eye parellelepiped examination showing Vogt’s striae (red arrow)
Fig.2(a): Left eye under diffuse illumination showing apparently normal cornea
In left eye (figure 3), the anterior curvature map showed steep cornea (black arrows) with steep K value 54.18 D and flat K 48.64D (black circle). Kmax was 63.85 D (green arrow). Thinnest pachymetry was 415 microns (yellow cross mark) and posterior elevation at this point was 100 microns.
| Discussion Keratoconus is a progressive corneal disorder characterized by thinning and steepening of the cornea, leading to irregular astigmatism and visual impairment. Collagen cross-linking (CXL) has emerged as a key therapeutic intervention to halt or slow down the progression of keratoconus. During CXL, a photosensitizing agent, typically riboflavin (vitamin B2), is applied topically to the cornea. The cornea is then exposed to ultraviolet-A (UVA) light, which activates the riboflavin and initiates a series of photochemical reactions. These reactions lead to the formation of new covalent bonds or cross-links between the collagen fibrils in the corneal stroma. The cross-links created during the CXL process result in the stiffening and strengthening of the corneal tissue. Although CXL has shown promising results in stabilizing the disease, it is essential to recognize that a minority of patients may still experience progression. This imagewise aims to illustrate the progression of keratoconus in a patient following collagen cross-linking. On 9 months follow up, BCVA of right eye was 6/6p with refractive error of -1.5Dsph/+1.25Dcyl@ 140° and left eye 6/9p with -4Dsph. There were changes in the BCVA and refractive error in both eyes. Right eye showed increase in keratometry values and reduction in corneal thickness suggestive of progression. Left eye also showed similar changes despite having undergone collagen cross-linking previously. The patient was advised CXL in the right eye and close follow up for left eye. The possible need for OS repeat CXL in the next few months was also clearly explained to the patient, if the current trend was seen to persist on serial tomography. The most widely used tomographic criterion for progression of keratoconus is recognized as increase in maximal keratometry (Kmax) by 1 or more diopters (D) in 2 consecutive measurement using same imaging method and decrease in pachymetry by more than 20 microns within a span of 12 months. For post CXL, progression has been defined as an increase in Kmax of more than 1 diopter along with possible deterioration of BCVA after the first 6 postoperative months and an indication for repeat CXL if there are no contraindications. Failure rate of CXL vary in different studies and have been reported to range from 0% to 23%. Factors for progression of keratoconus included young age, neurodermatitis, allergic conjunctivitis, eye rubbing and preoperative Kmax more than 58D. Significant risk factors for progression after the initial CXL treatment include eye rubbing and preoperative Kmax >58.0 diopters. Our patient was young, had history of eye rubbing and left eye Kmax was more than 58D at baseline. Both eyes showed progression at the same time despite being stable post CXL in left eye. Therefore in such cases, risk of progression should be discussed with the patient before CXL is performed. Due to the infrequency of progression following CXL, available literature on repeat CXL is widely dispersed and lacks consistency. Repeat CXL appears to be safer and highly effective in arresting any further advancement due to its additive flattening effect. However, there are certain constraints associated with its implementation. It is likely that the cornea will become thinner as a result of the effects of CXL on collagen fibers and potential ongoing progression. Furthermore, the potential hyperopic impact of CXL should always be considered when contemplating repeat treatments. ReadWise: 1. Tzamalis A, Diafas A, Vinciguerra R, Ziakas N, Kymionis G. Repeated corneal cross-linking (CXL) in keratoconus progression after primary treatment: updated perspectives. Seminars in Ophthalmology. 2021 Oct 3; 36(7): 523-530. doi: 10.1080/08820538.2021.18937622. Kuechler SJ, Tappeiner C, Epstein D, Frueh BE. Keratoconus Progression After Corneal Cross-Linking in Eyes With Preoperative Maximum Keratometry Values of 58 Diopters and Steeper. Cornea. 2018 Nov;37(11):1444-1448. doi: 10.1097/ICO.0000000000001736. PMID: 30157048. 3. Antoun J, Slim E, El Hachem R, Chelala E, Jabbour E, Cherfan G, Jarade EF. Rate of corneal collagen crosslinking redo in private practice: risk factors and safety. J Ophthalmol. 2015;2015:690961. doi: 10.1155/2015/690961. Epub 2015 Mar 19. PMID: 25874118; PMCID: PMC4383466. 4. Maskill D, Okonkwo A, Onsiong C, et al. Repeat corneal collagen cross-linking after failure of primary cross-linking in keratoconus. British Journal of Ophthalmology Published Online First: 21 June 2023. doi: 10.1136/bjo-2023-323391 Correspondence Dr. Prabhat Nangia DNB, FICO, FMRF, FAICO Department of Cornea and Ocular surface Suraj Eye Institute, Nagpur Email – education@surajeye.org QuizWise : 1. Which of the following statements regarding collagen cross-linking (CXL) is true? A) CXL is a surgical procedure used to correct refractive errors. B) CXL involves the use of a photosensitizing agent and ultraviolet-A (UVA) light. C) CXL is primarily used to treat cataracts. D) CXL is only effective in improving visual acuity in patients with myopia. 2. Indications for CXL include: A) An increase of 1.00 diopter (D) or more in the steepest keratometry measurement in 12 months. B) An increase of 1.00 D or more in the manifest cylinder in 12 months. C) An increase of 0.50 D or more in the manifest refraction spherical equivalent in 12 months. D) All of the above. 3. Risk factor for progression of keratoconus includes A) Young age B) Eye rubbing C) Preoperative Kmax more than 58D D) All of the above 4. Riboflavin 0.1% without Dextran on the cornea every 2 min for 10 min is used in A) Conventional Corneal Collagen CXL (C-CXL) B) Accelerated Corneal Collagen CXL (A-CXL) C) Iontophoresis (I-CXL) D) All of the above |
ReadWise
Correspondence
Dr Prabhat Nangia
DNB, FICO, FMRF, FAICO
Department of Cornea and Ocular surface
Suraj Eye Institute, Nagpur
Email – education@surajeye.org