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 Table of Contents  
CASE REPORT
Year : 2021  |  Volume : 1  |  Issue : 2  |  Page : 280-282

Open-angle glaucoma in a case of cornea plana with unilateral microcornea: A cloud on the horizon


1 Department of Glaucoma, Sankara Eye Hospital, Bengaluru, Karnataka, India
2 Department of Cornea, Sankara Eye Hospital, Bengaluru, Karnataka, India

Date of Submission06-May-2020
Date of Acceptance01-Dec-2020
Date of Web Publication01-Apr-2021

Correspondence Address:
Dr. Meena Menon
Sankara Eye Hospital, Varthur Road, Munnekollal, Bengaluru - 560037, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijo.IJO_1324_20

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  Abstract 


Cornea plana is a rare congenital condition, usually occurring bilaterally, characterized by flat cornea and low refractive power. Glaucoma due to angle closure is a more common association owing to the shallow anterior chamber. We report a case of an elderly lady with bilateral cornea plana with immature cataract and open-angle glaucoma, and unilateral microcornea. The patient is visually rehabilitated. Her glaucoma is stable, maintained on a single anti-glaucoma medication. In conclusion, IOP measurement in these patients can be biased due to varied corneal morphology. However, with proper evaluation, these challenging cases can be well managed.

Keywords: Cornea plana, intra-ocular pressure, microcornea, open-angle glaucoma


How to cite this article:
Menon M, Shreeshruthi N, Sudhakar P, Balasubramaniam A. Open-angle glaucoma in a case of cornea plana with unilateral microcornea: A cloud on the horizon. Indian J Ophthalmol Case Rep 2021;1:280-2

How to cite this URL:
Menon M, Shreeshruthi N, Sudhakar P, Balasubramaniam A. Open-angle glaucoma in a case of cornea plana with unilateral microcornea: A cloud on the horizon. Indian J Ophthalmol Case Rep [serial online] 2021 [cited 2021 Jul 29];1:280-2. Available from: https://www.ijoreports.in/text.asp?2021/1/2/280/312325



Cornea plana, a rare anomaly of anterior segment dysgenesis, has two hereditary forms, with the gene for both mapped on the long arm of chromosome 12.[1] The autosomal-dominant form has a near-normal visual acuity, clear cornea, with the corneal power about 38-42D. The recessive form, on the other hand, is more severe, with the corneal power being strongly reduced to about 25–35D.[1],[2] Other features include microcornea, deep central corneal opacities, widened limbus, an early arcus, high hyperopia, and a shallow anterior chamber (AC). We hereby report an interesting case of cornea plana and open-angle glaucoma, with unilateral microcornea.


  Case Report Top


A 59-year-old lady presented to us with complaints of blurred vision in both eyes for five years, with a history of use of topical anti-glaucoma medication in both eyes for six months. Three of her brothers were also on treatment for glaucoma.

On examination, best-corrected visual acuity (BCVA) was counting fingers at six feet in both her eyes, with a refraction of +8.50Ds/-2.50Dc at 150 in her right eye while that in her left eye was +6.50Ds/-2.00Dc at 80. Slit-lamp examination [Figure 1]a and [Figure 1]b and corneal topography [Figure 2] revealed the presence of flat cornea in both her eyes along with features of micro cornea in her left eye. Her AC depth was adequate (Van Herrick grade 3), with senile immature cataract in both eyes.
Figure 1: (a and b): Slit lamp image of the right and left eyes respectively. (c and d) show open angles on gonioscopic examination of the right and left eyes respectively

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Figure 2: (a and b): Anterior corneal curvature maps representing flat cornea of the right and the left eyes respectively. (c and 2d) represent the corneal pachymetry maps of the right and the left eyes respectively

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Keratometry reading was 34.44 at 136/37.41 at 46° in her right eye, and 36.26 at 77/37.22 at 167° in the left. The axial length (AL) measurements in her right and left eyes were 23.66 mm and 23.51 mm, respectively, while the white-to-white (WTW) diameter were 11.93 mm in her right eye and 9.84 mm in the left. All the biometric measurements were obtained on Lenstar 900. Pachymetry reading (TOMEY Pachymeter SP3000) was 422μ in the right eye and 429μ in the left. Intra-ocular pressure (IOP) measured with Goldmann applanation tonometer (GAT), was 10 mm Hg and 12 mm Hg in right and left eyes respectively. Comparable values were obtained with Non-contact tonometer (NCT) and Tonopen.

Gonioscopy in both eyes showed open angles (Shaffer grade 3) in all the quadrants in the presence of prominent iris processes [Figure 1]c and [Figure 1]d A detailed fundus evaluation revealed large disc in both eyes with vertically oval cup with cup to disc ratio (CDR) of 0.7 in her right eye, while the left eye had a CDR of 0.8 with bipolar thinning of the neuro-retinal rim.

The patient underwent phacoemulsification with foldable posterior chamber intraocular lens (PCIOL) implantation in both the eyes.

Following cataract surgery, visual field analysis (HFA 24-2 SITA standard) showed few depressed points in the nasal field of her right eye and an inferior arcuate scotoma in her left eye [Figure 3].
Figure 3: (a and b): HFA of the right and the left eyes respectively

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  Discussion Top


Cases of cornea plana have been reported with a strong genealogical occurrence in isolated areas across the world.[2] Developmental arrest of the corneal curvature relative to the sclera is the proposed pathogenesis in this entity. Mutations in KERA gene have been attributed to the recessive forms.[3] Our patient had features of bilateral flat cornea and OAG however, with only a unilateral presence of microcornea, which is a rare entity, with no documentation of such an association, especially in an Indian population. Shallow AC in patients with cornea plana is an attributable risk factor for development of ACG.[3],[4] However, there can be an association of open-angle glaucoma with this entity, similar to that seen in our patient.[2],[5] Further, the pedigree charting supports the recessive nature of the disease in this scenario [Figure 4].
Figure 4: Pedigree charting

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Tonomtery is another challenge in these patients, owing to the influence of extreme values of corneal curvature in obtaining reliable IOP. We measured the IOP with the available NCT, GAT and tonopen, which are calibrated using normal corneas, leading easily to erroneus results. All the 3 instruments recorded a mean of 10-12 mm Hg. However, considering the fact that our patient had a CCT lower than that of a normal average of 520μ, there could be an underestimation of recorded IOP by around 6 mm Hg.[6] Though there is no single tonometer available to measure the perfect intra-ocular pressure in all the conditions, researchers have proposed that Dynamic contour tonometry and the ocular response analyzer provide useful alternatives to GAT in patients with abnormal cornea.[7],[8] IOP measurements obtained using a rebound tonometer, similar to GAT, are more influenced by overall corneal biomechanics.[9] In agreement with our study, Hafner A et al. obtained the corrected IOP by addition of 1 mm Hg to GAT value for every 3D decrease in corneal power.[10]

Our patient has been maintained on a single anti-glaucoma medication (Travoprost eye drops once at night) in both her eyes with a GAT corrected IOP of 9 mm Hg and BCVA of 20/30 on her last visit. In addition, her visual fields have also remained stable since the past six months with no features of progression. A genetic analysis, however, could have further added to our knowledge in this scenario. However, family members have been educated regarding genetic counseling.


  Conclusion Top


There is paucity of literature on association of open-angle glaucoma with cornea plana. More so, this combined entity with the presence of unilateral microcornea is a unique triad of findings. Measurement of IOP in these set of eyes can be challenging due to the influence of corneal morphology. Despite the ocular comorbidities, these patients do well with proper visual rehabilitation in addition to early diagnosis and management.

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.
Tahvanainen E, Sigler-Villanueva A, Forsius H, Salo P, de la Chapelle A. Dominantly and recessively inherited cornea plana congenita map to the same small region of chromosome 12. Genome Res 1996;6:249-54.  Back to cited text no. 1
    
2.
Forsius H, Damsten M, Eriksson AW, Fellman J, Lindh S, Tahvanainen E. Autosomal recessive cornea plana: A clinical and genetic study of 78 cases in Finland. Acta Ophthalmol Scand 1998;76:196-203.  Back to cited text no. 2
    
3.
Liu CY, Birk DE, Hassell JR, Kane B, Kao WWY. Keratocan-deficient mice display alterations in corneal structure. J Biol Chem 2003;278:21672-7.  Back to cited text no. 3
    
4.
Kumari D, Tiwari A, Choudhury M, Kumar A, Rao A, Dixit M. A novel KERA mutation in a case of autosomal recessive cornea plana with primary angle-closure glaucoma. J Glaucoma 2016;25:106-9.  Back to cited text no. 4
    
5.
Sahin BO, Seymenoglu G, Baser EF. Cornea plana associated with open-angle glaucoma: A case report Int Ophthalmol 2011;31:505-8.  Back to cited text no. 5
    
6.
Whitacre MM, Stein RA, Hassanein K. The effect of corneal thickness on applanation tonometry. Am J Ophthalmol 1993;115:592-6.  Back to cited text no. 6
    
7.
Andreanos K, Koutsandrea C, Papaconstantinou D, Diagourtas A, Kotoulas A, Dimitrakas P, et al. Comparison of Goldmann applanation tonometry and Pascal dynamic contour tonometry in relation to central corneal thickness and corneal curvature. Clin Ophthalmol 2016;10:2477-84.  Back to cited text no. 7
    
8.
Clement CI, Parker DG, Goldberg I. Intra-ocular pressure measurement in a patient with a thin, thick or abnormal cornea. Open Ophthalmol J 2016;29:35-43.  Back to cited text no. 8
    
9.
Brown L, Foulsham W, Pronin S, Tatham AJ. The influence of corneal biomechanical properties on intraocular pressure measurements using a rebound self-tonometer. J Glaucoma 2018;27:511-8.  Back to cited text no. 9
    
10.
Hafner A, Seitz B. Primary open angle glaucoma in cornea plana masked by false normal applanation tonometry (Goldman)—a case report. Klin Monatsbl Augenheilkd 2001;218:621-5.  Back to cited text no. 10
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]



 

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