|Year : 1982 | Volume
| Issue : 4 | Page : 357-361
Acquired keratoconus posticus
G Mukherjee, N Patnaik, M Mohan
Dr. Rajendra Prasad Centre for Ophthalmic Sciences, Ansari Nagar, New Delhi, India
Dr. Rajendra Prasad Centre for Ophthalmic Sciences New Delhi-29
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Mukherjee G, Patnaik N, Mohan M. Acquired keratoconus posticus. Indian J Ophthalmol 1982;30:357-61
Thinning of cornea at the expense of posterior layers with normal anterior carvature, a rare conditions, in keratoconu; posticus. Adequate emphasis have been laic on congenital generalised keratoconus posticus in the literature. Stray case reports are available on acquired keratoconus posticus. Congenital keratoconus posticus basically is the result of developmental arrest of cornea] mesoderm, whereas the aetiopathogenesis of acquired keratoconus posticus is not well known. An attempt has been made in this study to report a series of well documented cases of acquired keratoconus posticus and to throw lights on the aetiopathogenesis.
| MATERIALS, METHODS AND OBSERVATIONS|| |
12 cases of keratoconus posticus attended the cornea clinic during last 4 years. Two cases were of congenital and other 10 cases were of acquired type. One case of congenital type had binocular lesion and other 1 I cases had uniocular involvement, A total of 13 eyes, were studied in details and documented according to Mohan et all. [Figure - 1]. Special investigations e.g. refraction keratometry, contact lens trial, pachometry etc. were carried out besides routine detailed examination.
In our series males (7 : 5) were predominently affected with wide variation in age group (from 20 years to 72 years excluding two cases of congenital type). The Visual acuity without correction, with spectacle correction and finally with contact lenses is shown in [Table - 1]. Refractive status and biometry of cornea of these eyes are tabulated in Table.,
Most of our acquired cases had history of and or evidence of healed corneal or anterior segment pathology [Table - 4]. One case of congenital keratoconus posticus was associated with anterior lenticonus whereas other case had persistent pupillary membrane in right eye and anterior polar cataract in the left eye.
Two corneal buttons from acquired cases removed during penetrating keratoplasty were studied in details with light microscope. There were marked thinning almost half in thickness of the posterior layers of cornea at the site of the cone. The conical zone covered with two to four layer thick corneal epithelium, irregularly arranged. The Bowman's layer was fibrotic and absent in it's most part. The stromal lamellae were irregularly arranged with fibroblastic reaction. There were very few vessels in the corneal stroma. The Descemets membrane was thicker than the normal, no discontinuity seen. No secondary deposits or degeneration seen. Corneal nerves were normal in the peripheral part of the button.
Congenital keratoconus posticus though relatively uncommon corneal condition but reports are available in the literature, where as acquired type is really a rare condition, only few scattered reports are available in the literature. We studied well documented 10 cases of acquired keratoconus posticus and 2 cases of congenital keratoconus pesticus. Congenital cases as reported are bilateral noninfiammatory and are associated with congenital defects of the anterior segment. We also noted the similar pattern, in our series. Ophthalmic literature has adequately covered the incidence, pathogenesis. clinical picture and its variations. We concentrated ourselves on the problem of acquired keratoconus posticus in this study.
We made the following clinical observations on acquired keratoconus posticus
(1) Most of these cases are unilateral
(2) Suffers from gross visual loss.
(3) Mostly myopic with regular astigmatism.
(4) Evidence of burnt out corneal lesion i.e. corneal opacity with mild to moderate vascularisation.
(5) Anterior corneal curvature either normal or slightly toric
(6) Slit lamp examination clinches the diagnosis; thinning of cornea at it's posterior layers without anterior protru sion of cornea [Figure - 1]
(7) No or very little improvement with contact lenses.
Histopathology of congenital keratoconus posticus is totally different from typical keratoconus. Adequate emphasis has been laid on the light and electron microscopic picture But the histopathology of acquired keratoconus posticus is different. Corneal buttons studied revealed more of stromal collagenous reaction in the surrounding areas of cone suggesting burntout corneal pathology with minimal vascularization. Neither hyaline thickening of descemets membrane nor endothelial changes were seen as reported earlier [Figure - 2]
Many theories,, have been proposed to explain the pathogenesis of congenital keratoconus posticus but no report is yet available on the pathogenesis of acquired variety. Trauma has been blamed to cause keratoconus
posticus by many authors,. Good majority of cases in our series had history of trauma but we feel trauma as a predisposing of factor for corneal ulceration rather than a primary factor. So we feel the pathogenesis of acquired keratoconus posticus can be devided into four stages [Figure - 2]
I. Stage of Acute Ulceration : Active infiltration with ulceration resulting in necrosis of corneal stroma with little or no anterior protrusion of the Descemet's membrane. The intraocular pressure (I.O.P.) is normal. If the infective process is in progress or under control the dead tissues are thrown off resulting in thinning of cornea with anterior protrusion of the descemet's membrane.
II. Stage of Descemetocele with Subacute Ulceration : The stromal reaction and infectitve process slows down. The I.O.P. is either high or normal but not high enough to result in perforation.
III. Stage of Healing : The repairative process start with repair of epithelial defects as usual, laying down of stromal fibers and fibroblasts anterior to the descemets membrane, At this stage if quantity and strength of stromal lamellae are not adequate to push the Descemets membrane back to its original place as the natural tendency of the corneal stroma to retain its shape and structures or if the I.O.P. remains high or and healing process slows down, then this stage passes on to final stage as Acquired Keratoconus i.e. Stage IV .
The density and thickness of corneal opacity is dependent on the corneal vascularization to some extent as reported earlier by Mohan et al. Cases of acquired keratoconus posticus in our series, there were minimal vascularisation of cornea, so we agree to the hypothesis of Mohan et all. We consider acquired keratoconus posticus as a sequale of corneal ulcer and it is a condition similar to corneal fascets as seen on the epithelial side following corneal ulcer.
Conservative management of such cases are difficult as they do not improve with spectacle correction or contact lenses, penetrating keratoplasty is the only solution and can successful be done.
| Summary|| |
A series containing well documented 12 cases of keratoconus posticus has been presented in this article. 10 cases were of acquired type and two cases were of congenital type. Acquired cases had history of and, or burnt out signs of corneal ulceration. We feel acquired keratoconus posticus is a sequale of corneal ulcer and passes through four stages. Management of such cafes are surgical as conservative therapy has no beneficial effect.
| References|| |
Mohan, M., Mukherjee, G., and Angra, S.K., 1980, Ind, J. Ophthalmol 28 : 2..
Krachmer, J.H. and Rodriges Merlyn, M. 1978, A.M.A. Arch. Ophthalmol.96:10-1867.
Butler, T.H., 1930, Trans. Ophthalmol. Soc. U.K. 50 : 551.
Greene, P.B.. 1945, A.M.A. Arch. Ophthalrnol 34 : 432.
Jacobs H.B. 1957, Brit. J. Ophthalmol. 41 : 31.
Angra S.K. and Mohan M. 1969. Orient. Arch. Ophthalmol 7 : 370.
Jacobs, H.B. 1957, Brit. J. Ophthalmol. 41 : 40.
[Figure - 1], [Figure - 2]
[Table - 1], [Table - 2], [Table - 3], [Table - 4]