Indian Journal of Ophthalmology

ARTICLES
Year
: 1979  |  Volume : 27  |  Issue : 4  |  Page : 144--149

Pattern of amblyopia and fixation after keratoplasty


Gubax Singh Bhinder, Gopal Varma, Mohinder Singh Sanghi 
 Guru Nanak Eye Centre, New Delhi-110002, India

Correspondence Address:
Gubax Singh Bhinder
Associate Professor of Ophthalmology, Guru Nanak Eye Centre, New Delhi
India




How to cite this article:
Bhinder GS, Varma G, Sanghi MS. Pattern of amblyopia and fixation after keratoplasty.Indian J Ophthalmol 1979;27:144-149


How to cite this URL:
Bhinder GS, Varma G, Sanghi MS. Pattern of amblyopia and fixation after keratoplasty. Indian J Ophthalmol [serial online] 1979 [cited 2020 May 29 ];27:144-149
Available from: http://www.ijo.in/text.asp?1979/27/4/144/32606


Full Text

With the increase in the facilities of perform­ing keratoplasty majority of corneally blind patients attend corneal clinics with the hope of restoration of vision. Sometimes the patient may not regain vision after a successful corneal graft due to associated amblyopia. In India such situation is encounted more frequently be­cause of corneal opacities due to keratomalacia, keratoconjunctivitis and small pox which occur commoly in early childhood and corneal graft­ing in these eyes could not be performed due to the lack of medical facilities. Hence it became extremely importont to select cases for surgery in order to avoid disappointment and check against the waste of valuable donor material.

To substantiate the above statement, data has been collected from the cases of corneal clinic, Irwin Hospital where corneal grafting was performed without giving consideration to the age of onset of the opacity and its duration. This gave us the opportunity to study the density of amblyopia in cases who had clear media post-operatively.

 Materials and Methods



Forty cases of corneal grafts which remained opti­cally clear for at least three months postoperatively with clear optical media were selected from the coneal clinic of Irwin Hospital. Cases having any pathology in the media, retina or in the visual pathways which could explain the low visual acuity in these cases were discarded.

Cases were devided into two groups according to the age of onset of anomalies. Cases with onset of anomaly before 5 years and after 5 years of age were labelled as group A and B respectively. Each group comprised of 20 cases [Table 1],[Table 2].

Visual acuity was determined after proper refractive correction, utilizing Snellen's whole line optotypes. In cases of corneal opacity where visual acuity did not improve satisfactorily with the glasses decause of irregu­lar astigmatism, contact lens trial was given to find out the maximum visual improvement. Fixation pattern was determined with the help of the projectoscope after full mydriasis. Type of fixation and the degree of eccentricity were graded according to the classification of Malik et al. (1969).

 Observations



All the cases in group A had associated squint of varying degree whereas most of the cases in group B were orthophoric, only few cases in this group held small degree of squint.

Refractive state in both the groups showed astigmatism in almost all cases. The degree and type of refractive error in two groups were camparable [Table 3].

Most of the cases selected for corneal graft­ing in both the groups had very poor visual acuity ranging from accurate projection of light to counting fingers. Postoperative visual gain in individual cases of group A and group B have been shown in [Figure 1],[Figure 2] respec­tively. In group A, 16 cases (80%) did not show any visual gain postoperatively. 4 cases (20%) showed slight to moderate improvement. Out of these 4 cases, in 3 cases the operated eye was the only eye, the other eyes had corneal opacity (case No. 8,9, and 10 [Table 1]). In one case (Case No. 1) visual acuity improved from 3/60 to 6/18 postoperatively. Corneal opacity in this case developed just at the age of 5 years and operated one and a half years later. In group B, 19 cases (95%) had visual improve­ment after corneal grafting, only in one case (case No. 1, [Table 2]) visual acuity did not improve. This patient was a 31 years old male and held developed corneal leucoma in right eye at the age of 17-18 years following injury with a hockey ball. Corneal grafting was done 12-13 years after, the graft was clear for the last two years, having clear media and ophthal­moscopically normal fundus. The patient had divergent squint and divergent type of fixation in this eye.

11 cases in group A in whom no visual gain was observed postoperatively had eccentric fixation mostly centrocaecal to paracaecal type, out of these 6 cases had divergent and 5 cases convergent squint. Only one case had diver­gent type of fixation with associated divergent type of squint. 4 cases in this group which had associated divergent squint and nystagmus failed to show any particular retinal point of fixation. They however, had the areas of fixation very widely eccentric. Case No. I [Table 1] had parafoveal type of fixation and had shown a visual gain from 3/60 to 6/ 18 postoperatively. All the three cases of bilateral corneal opacity mentioned earlier had central fixation in the grafted eye.

In group B, 18 cases (90%) had central fixation and 2 cases (10%) had eccentric fix­ation. Fixation pattern in the grafted eye in the two groups have been shown in [Figure 3].

 Discussion



It has been known that the anatomic struc­ture of the peripheral organ of vision are almost complete at birth but vision develops only gradually and it depends to a certain extent on adequate stimulation of retina by light or form vision during early infancy and childhood. When it is deprived of such stimulation to the eyes by opacity in the ocular media earlier in life a condition of irreversible loss of visual acuity develops which is termed as amblyopia ex-anopsia or stimulus deprivation ambly­opia by Von Noorden[6]. In experimental studies by Chow, Risen and Newell[1], Wiesel and Hubel[10],[11]; Von Noorden et al[7]; Goswamy et al[2] reported severe irreversible amblyopia in animals when their eyes were occluded (either by suturing the lids or by plastic occluder or by producing corneal scarification) during the first few months of life. No comparable visual defect was observed when these experiments were repeated in adult animals. Though such data cannot be transferred to human without reservation, the observation appears to be very closely appli­cable to clinical observation.

The present study reveals that when corneal opacity is unilateral and occurs before 5 years of age and corneal grafting is delayed until adulthood, a severe amblyopia develops. If however, the corneal opacities are bilateral, the amblyopia is not very dense at least in one eye and good visual improvement takes place (case No. 9, [Table 1]). Von Noorden et al (1968) too noted the similar observations in 3 cases. He did not get improvement in unilateral corneal opacity case, but some visual improvement was seen in rest of two cases of bilateral corneal opacity. Picetti and Fine (1965) also observed good visual gain in two cases of bilateral con­genital corneal dystrophy even though these two cases were operated at 7 years of age.

In the present series all the cases of unilateral corneal opacity before 5 years of age developed eccentric fixation but if the corneal opacity is bilateral, then in the relatively better eye foveal fixation is preserved and visual gain is expected (case No. 8,9, and 10 [Table 1]).

The present series also clearly indicates that when corneal opacity develops after 7 years of age, it has no significant influence on the deve­lopment of amblyopia and fixation pattern irrespective of the duration of the opacity be­fore surgery. However if the corneal opacity is unilateral and develop around the border line age of 5 and 7 years (case No. 1, [Table 1]) and case No. 7, [Table 2]) there is less improvement in visual acuity with parafoveal type of eccentric fixation.

 Summary



Forty cases of clear corneal grafts in two groups in patients who developed corneal opa­cities either before or after 5 years of age were investigated for pattern of amblyopia and fix­ation. Severe irreversible form of amblyopia with eccentric fixation observed in cases of uni­lateral corneal opacity when the anomlay occur­ed before 5 years of age and corneal grafting was delayed until 2nd or 3rd decade of life. If corneal opacity is bilateral although onset was before 5 years of age yet the improvement in visual acuity after corneal grafting occurs in relatively better eye with foveal fixation. Good visual result was seen after corneal grafting when opacity occured after 5 years of age. Foveal fixation was also observed in most of these cases.[12]

References

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