|Year : 2021 | Volume
| Issue : 2 | Page : 280-282
Open-angle glaucoma in a case of cornea plana with unilateral microcornea: A cloud on the horizon
Meena Menon1, N Shreeshruthi1, Priyanka Sudhakar1, Anand Balasubramaniam2
1 Department of Glaucoma, Sankara Eye Hospital, Bengaluru, Karnataka, India
2 Department of Cornea, Sankara Eye Hospital, Bengaluru, Karnataka, India
|Date of Submission||06-May-2020|
|Date of Acceptance||01-Dec-2020|
|Date of Web Publication||01-Apr-2021|
Dr. Meena Menon
Sankara Eye Hospital, Varthur Road, Munnekollal, Bengaluru - 560037, Karnataka
Source of Support: None, Conflict of Interest: None
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 2022 Dec 9];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. 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., 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|| |
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].
| Discussion|| |
Cases of cornea plana have been reported with a strong genealogical occurrence in isolated areas across the world. 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. 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., However, there can be an association of open-angle glaucoma with this entity, similar to that seen in our patient., Further, the pedigree charting supports the recessive nature of the disease in this scenario [Figure 4].
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. 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., IOP measurements obtained using a rebound tonometer, similar to GAT, are more influenced by overall corneal biomechanics. 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.
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|| |
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
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]