A C T A 0 P H T H A L M 0 L O G IC A
70 (1992) 111-114
Keratoconus in the mentally retarded Olav H. Haugen Department of Ophthalmology,University of Bergen, Norway
Abstract. Among 212 institutionalized mentally retarded, there were 16 patients with keratoconus (7.5%). Eight of the keratoconus cases were unilateral. The possible role of eye rubbing as well as other etiological factors are discussed. Key words: keratoconus syndrome.
-
mental retardation - Down’s
There is a well known association between keratoconus and mental retardation. While the prevalence of keratoconus in a normal population is about 1/1000, several authors have reported a prevalence of 5-15%among the mentally retarded. In particular, the increased frequency of keratoconus among patients with Down’s syndrome has been well documented since the first report by Rados (1948). The exact cause of this increased prevalence of keratoconus in mentally retarded people is not known. Genetic alterations leading to structural or biochemical changes in the cornea, and extensive eye rubbing are the two main hypotheses. In this paper the prevalence of keratoconus in an institution for mentally retarded people is reported together with other ophthalmological features among this group of patients.
Material and Methods During March-April 1989 212 persons (92 females and 120 males) were examined. This comprised all the inhabitants of the institution. The mean age of the patients was 46 years (range 15-90).The causes of mental retardation are listed in Table 1. Prior to examination, the staff at the institution answered a
questionnaire for each patient, giving their impression of the patients’ visual function and interest in ‘visual’ activities, such as TV,cartoons and newspapers. All the patients underwent an examination including the position and motility of the eyes, a thorough inspection of the anterior segment, indirect ophthalmoscopy and retinoscopy in cycloplegia. Different tests were used to assess the visual acuity (Table 2). The diagnosis of keratoconus was based upon inspection of the cornea with focal illumination, slit-lamp examination (whenever possible), the presence of an abnormal red reflex indicative of keratoconus and retinoscopy in cycloplegia (irregular astigmatism). All examinations were carried out at the institution by the author. Keratometry was not available. The keratoconus patients were examined with regard to structural changes of the iris, especially translucency, using paraxial illumination through the dilated pupil with the slit-lamp. Diascleral transillumination was not possible to perform. Six years prior to this study, patient no. 1 (Table 3) underwent a penetrating keratoplasty in the right eye. The corneal transplant remained transparent for 4 years, thereafter it was thickened and gradually opacified, probably due to trauma. None of the other keratoconus patients had undergone corneal surgery. To evaluate the possible role of eye rubbing in the etiology of keratoconus, a quantification of the eye rubbing was estimated by the institution staff both in the keratoconw patients and in a control group. Mantel-Haenszel’stest was applied for statistical analyses. 111
Diagnosis
patients
Down’s syndrome Neonatal asphyxia CNS-infection in infancy Hydrocephalus Prematurity Microcephalus Head trauma Metabolic disease - Felling‘s disease - Galactosemia - Cretinism - Spielmeyer-Vogt’sdisease Intracranial haemorrhage Prenatal infection Identified clinical syndromes Kernicterus Unknown
I
30 15 9 6 5 5 4 1 1 1 1 3 3 2 1 125
Age
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
F M M M M F F M F M M M M F F F
60 41 30 51 36 31 82 32 50 69 46 46 52 32 74 47
Diagnosis
Unknown Unknown Unknown Down Unknown Down
*
Down Unknown Unknown Unknown Down Down Unknown Down Unknown
104 57
Total
212
17 34
Results Prevalence of keratoconus
Keratoconus was found in 16 (6 males and 10 females) of the 212 inhabitants (7.5%).Clinical information about these patients is summarized in Table 3. The keratoconus was unilateral in 8 pa-
212
Sex
Chart tests (Snellen, 0sterberg) Non-symbol test (smarties at 1 m, ‘hundreds-and-thousands’) Fixation pattern/follow movements (hand-doll) Unable to test
4
Total
Patient no.
No. of patients
Visual acuity test
Keratoconus unilateral/ bilateral bilateral bilateral bilateral bilateral bilateral unilateral unilateral bilateral unilateral unilateral bilateral bilateral unilateral unilateral unilateral unilateral
Ability Staff’s general to Visual impression commuof visual tests2 nicate’ function 1 2 3 3 3 3 2 2 3 3 2 2 3 1 3 1
impaired normal impaired normal normal impaired impaired impaired normal uncertain impaired impaired impaired normal impaired normal
1 1 2 4 3 2 1 1 2 4 2 1 3 1 3 1
Visual acuityg
Therapeutic measurements
2 1 2 0 0 2 1 2 2 0 2 2 3 1 4 1
none glasses epikeratophakia O.S. none keratoplasty 0.d. glasses glasses epikeratophakia 0.d. none none epikeratophakia O . S . none none none
**
none
’ 1=normal language, 2 =single words/signs, 3 =no language.
‘ 1=chart test (Snellen or asterberg), 2
= non-symbol tests (smarties, ‘hundred-and-thousands’), 3=fixation pattern, follow movements using a hand doll, 4=unable to evaluate. 1= 2 6/18, 2 = 6/24-6/60, 3 = 6/60 - cf. 1m, 4 = cf. 1m - cf. ad oc., 5 =light perception, 6 = amaurosis, 0 =impossible to classify. * Intracranial haemorrhage. ** Considered for cataract extraction, but refuse.
112
tients, bilateral in 8. Six of the patients had Down’s syndrome. Hence, the prevalence of keratoconus among the 30 patients at the institution with Down’s syndrome was 20%.Ten of the 182 mentally retarded without Down’s syndrome (5.5%)had keratoconus. One of these patients had a history of intracranial haemorrhage at the age of one year, while the causes of mental retardation in the remaining 9 patients were unknown. A chromosome analysis of all the non-Down’s syndrome keratoconus patients showed a normal karyotype. Table 4 shows the refraction of the fellow eye in the unilateral cases.
Patient no.
Keratoconus eye (R/L)
6
Refraction of the fellow eye 0”-4.5+5 0”-3.0--8 Emmetropia 60”- 1 .O- 1 .0 impossible due to cataract+l.O +1.0 impossible due to cataract 160“-1.0
7 9 10 13 14 15 16
Structural changes of the iris
One of the keratoconus patients without Down’s syndrome had a bilateral speckling of the iris colour. Three of the 6 keratoconus patients with Down’s syndrome had Brush field spots. Apart from these changes, the iris appeared normal in the keratoconus patients as judged with focal illumination and/or slit-lamp examination. In 6 patients it was possible to examine for translucency of the iris, but with negative result. Eye rubbing
Table 5 shows that the keratoconus patients really did rub their eyes more often than the other mentally retarded, both among patients with and without Down’s syndrome ( P = 0.008 in both groups). Treatment
Four of the bilateral keratoconus patients were operated. Epikeratophakia was performed in three cases, while a penetrating keratoplasty was done in the fourth patient.
Discussion The prevalence of keratoconus among patients with Down’s syndrome has usually been reported to be 2-15%(Skeller & 0ster 1951; Cullen & Butler 1963; Levy 1984; Shapiro & France 1985; Riise 1986; Prokesova et al. 1990). Thus, the prevalence of 20% in our material is high compared with earlier reports. However, Jacobson (1988) has reported an exceptionally high prevalence of keratoconus (30%)among 50 patients with Down’s syndrome, but of the above mentioned authors, only Jacobson performed keratometry in a number of her patients. This fact could in part explain the high figure of keratoconus in her material. Our study also revealed a remarkably high prevalence (5.5%)of keratoconus among the mentally retarded without Down’s syndrome. This could indicate a common, but yet unknown cause for the mental retardation and the corneal defect.
Table 5. Frequency of eye rubbing in 46 mentally retarded patients.
8
Acta Ophthal. 70.1
Normal
Often
Very often
(Yo)
(04
(Yo)
113
It is interesting that pathology of the iris and the pupil has been reported in association with keratoconus (Urrets-Zavalia1963; Bertelsen & Seim 1974; Davies & Ruben 1975; Baumann & Insler 1985). Embryologically,the corneal endothelium, the corneal stroma and the iris stroma are derived from the same tissue, namely, the neural crest cells. Thus, it is not surprising that iris pathology may be encountered in keratoconus patients. In our material 6 of the 16 patients with keratoconus cooperated sufficiently to be examined for translucency of the iris, but this phenomenon could not be demonstrated. Keratoconus is usually a bilateral disorder. With the exception of Walsh (1981), the prevalence of unilateral cases is generally estimated to be 10-15Yo (Amsler 1961; Ihalainen 1986). In contrast, 50% of the keratoconus cases in the present material were unilateral. In six of these unilateral cases the refractive state of the fellow eye could be assessed by retinoscopy, thus ensuring that these cases were truely unilateral. Eye rubbing occurred significantly more frequently in the keratoconus group than among the other mentally retarded patients. This may indicate an etiological significance of eye rubbing in the development of keratoconus in patients both with and without Down’s syndrome. However, as commonly experienced during keratoplastic surgery, the consistency and mechanical properties in the conical cornea in patients with Down’s syndrome, as well as in a number of other mentally retarded, appear to differ from those present in a ‘normal’ keratoconus cornea. Hence, the cornea of the mentally retarded patients is probably more vulnerable to mechanical trauma. Therfore, there is obviously not one single causal factor in the pathogenesis of keratoconus, but both genetic and environmental factors are probably of importance.
References Amsler M (1961): Quelques donnees du probleme. Bull SOCBelge Ophthalmol 129: 331-354. Baumann J & Insler M S (1985):Pupillary abnormalities in keratoconus. AM Ophthalmol 17: 766-767. Bertelsen T I & Seim V (1974):The cause of irreversible mydriasis following keratoplasty in keratoconus: a preliminary report. Ophthalmic Surg 5: 56-58. Cullen J F & Butler H G (1963):Mongolism (Down’s syndrome) and keratoconus. BrJ Ophthalmol47: 321-330. Davies P D & Ruben M (1975):The paretic pupil: its incidence and aetiology after keratoplasty for keratoconus. Br J Ophthalmol59: 223-228. Ihalainen A (1986):Clinical and epidemiological features of keratoconus. Genetic and external factors in the pathogenesis of the disease. Acta Ophthalmol (Copenh). Suppl 178: 1-66. Jacobson L (1988): Ophthalmology in mentally retarded adults. Acta Ophthalmol (Copenh) 66: 457-462. Levy B (1984):Incidence of oculo-visual anomalies in an adult population of mentally retarded persons. Am J Optom Physiol Opt 61: 324-326. Prokesova V, Kriz S, Berg L & Halvorsen I (1990):0yeunders~kelsehos psykisk utviklingshemmede i sentralinstitusjon. Tidsskr Nor Laegeforen 110: 1659-1662. Rados A (1948): Conical cornea and mongolism. Arch Ophthalmol40: 454-478. Riise R (1986): Synsfunksjonen ved Down syndrom. Tidsskr Nor Laegeforen 106: 317-319. Shapiro M B & France T D (1985):The ocular features of Down’s syndrome. Am J Ophthalmol99: 659-663. Skeller E & aster J (1951):Eye symptoms in mongolism. Acta Ophthalmol (Copenh)29: 149-161. Urrets-Zavalia A (1963):Fixed, dilated pupil, iris atrophy and secondary glaucoma. A distinct clinical entity following penetrating keratoplasty in keratoconus. Am J Ophthalmol 56: 257-264. Walsh S Z (1981): Keratoconus and blindness in 469 institutionalised subjects with Down’s syndrome and other causes of mental retardation. J Ment Defic Res 25: 243-251. Received on May 27th, 1991. Author’s address:
Acknowledgment This study was carried out with financial support from Riksforeningen mot blindhet og svaksyn.
114
Olav H. Haugen, Department of Ophthalmology, University of Bergen, N-5021 Bergen, Norway.
70 (1992) 111-114
Keratoconus in the mentally retarded Olav H. Haugen Department of Ophthalmology,University of Bergen, Norway
Abstract. Among 212 institutionalized mentally retarded, there were 16 patients with keratoconus (7.5%). Eight of the keratoconus cases were unilateral. The possible role of eye rubbing as well as other etiological factors are discussed. Key words: keratoconus syndrome.
-
mental retardation - Down’s
There is a well known association between keratoconus and mental retardation. While the prevalence of keratoconus in a normal population is about 1/1000, several authors have reported a prevalence of 5-15%among the mentally retarded. In particular, the increased frequency of keratoconus among patients with Down’s syndrome has been well documented since the first report by Rados (1948). The exact cause of this increased prevalence of keratoconus in mentally retarded people is not known. Genetic alterations leading to structural or biochemical changes in the cornea, and extensive eye rubbing are the two main hypotheses. In this paper the prevalence of keratoconus in an institution for mentally retarded people is reported together with other ophthalmological features among this group of patients.
Material and Methods During March-April 1989 212 persons (92 females and 120 males) were examined. This comprised all the inhabitants of the institution. The mean age of the patients was 46 years (range 15-90).The causes of mental retardation are listed in Table 1. Prior to examination, the staff at the institution answered a
questionnaire for each patient, giving their impression of the patients’ visual function and interest in ‘visual’ activities, such as TV,cartoons and newspapers. All the patients underwent an examination including the position and motility of the eyes, a thorough inspection of the anterior segment, indirect ophthalmoscopy and retinoscopy in cycloplegia. Different tests were used to assess the visual acuity (Table 2). The diagnosis of keratoconus was based upon inspection of the cornea with focal illumination, slit-lamp examination (whenever possible), the presence of an abnormal red reflex indicative of keratoconus and retinoscopy in cycloplegia (irregular astigmatism). All examinations were carried out at the institution by the author. Keratometry was not available. The keratoconus patients were examined with regard to structural changes of the iris, especially translucency, using paraxial illumination through the dilated pupil with the slit-lamp. Diascleral transillumination was not possible to perform. Six years prior to this study, patient no. 1 (Table 3) underwent a penetrating keratoplasty in the right eye. The corneal transplant remained transparent for 4 years, thereafter it was thickened and gradually opacified, probably due to trauma. None of the other keratoconus patients had undergone corneal surgery. To evaluate the possible role of eye rubbing in the etiology of keratoconus, a quantification of the eye rubbing was estimated by the institution staff both in the keratoconw patients and in a control group. Mantel-Haenszel’stest was applied for statistical analyses. 111
Diagnosis
patients
Down’s syndrome Neonatal asphyxia CNS-infection in infancy Hydrocephalus Prematurity Microcephalus Head trauma Metabolic disease - Felling‘s disease - Galactosemia - Cretinism - Spielmeyer-Vogt’sdisease Intracranial haemorrhage Prenatal infection Identified clinical syndromes Kernicterus Unknown
I
30 15 9 6 5 5 4 1 1 1 1 3 3 2 1 125
Age
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
F M M M M F F M F M M M M F F F
60 41 30 51 36 31 82 32 50 69 46 46 52 32 74 47
Diagnosis
Unknown Unknown Unknown Down Unknown Down
*
Down Unknown Unknown Unknown Down Down Unknown Down Unknown
104 57
Total
212
17 34
Results Prevalence of keratoconus
Keratoconus was found in 16 (6 males and 10 females) of the 212 inhabitants (7.5%).Clinical information about these patients is summarized in Table 3. The keratoconus was unilateral in 8 pa-
212
Sex
Chart tests (Snellen, 0sterberg) Non-symbol test (smarties at 1 m, ‘hundreds-and-thousands’) Fixation pattern/follow movements (hand-doll) Unable to test
4
Total
Patient no.
No. of patients
Visual acuity test
Keratoconus unilateral/ bilateral bilateral bilateral bilateral bilateral bilateral unilateral unilateral bilateral unilateral unilateral bilateral bilateral unilateral unilateral unilateral unilateral
Ability Staff’s general to Visual impression commuof visual tests2 nicate’ function 1 2 3 3 3 3 2 2 3 3 2 2 3 1 3 1
impaired normal impaired normal normal impaired impaired impaired normal uncertain impaired impaired impaired normal impaired normal
1 1 2 4 3 2 1 1 2 4 2 1 3 1 3 1
Visual acuityg
Therapeutic measurements
2 1 2 0 0 2 1 2 2 0 2 2 3 1 4 1
none glasses epikeratophakia O.S. none keratoplasty 0.d. glasses glasses epikeratophakia 0.d. none none epikeratophakia O . S . none none none
**
none
’ 1=normal language, 2 =single words/signs, 3 =no language.
‘ 1=chart test (Snellen or asterberg), 2
= non-symbol tests (smarties, ‘hundred-and-thousands’), 3=fixation pattern, follow movements using a hand doll, 4=unable to evaluate. 1= 2 6/18, 2 = 6/24-6/60, 3 = 6/60 - cf. 1m, 4 = cf. 1m - cf. ad oc., 5 =light perception, 6 = amaurosis, 0 =impossible to classify. * Intracranial haemorrhage. ** Considered for cataract extraction, but refuse.
112
tients, bilateral in 8. Six of the patients had Down’s syndrome. Hence, the prevalence of keratoconus among the 30 patients at the institution with Down’s syndrome was 20%.Ten of the 182 mentally retarded without Down’s syndrome (5.5%)had keratoconus. One of these patients had a history of intracranial haemorrhage at the age of one year, while the causes of mental retardation in the remaining 9 patients were unknown. A chromosome analysis of all the non-Down’s syndrome keratoconus patients showed a normal karyotype. Table 4 shows the refraction of the fellow eye in the unilateral cases.
Patient no.
Keratoconus eye (R/L)
6
Refraction of the fellow eye 0”-4.5+5 0”-3.0--8 Emmetropia 60”- 1 .O- 1 .0 impossible due to cataract+l.O +1.0 impossible due to cataract 160“-1.0
7 9 10 13 14 15 16
Structural changes of the iris
One of the keratoconus patients without Down’s syndrome had a bilateral speckling of the iris colour. Three of the 6 keratoconus patients with Down’s syndrome had Brush field spots. Apart from these changes, the iris appeared normal in the keratoconus patients as judged with focal illumination and/or slit-lamp examination. In 6 patients it was possible to examine for translucency of the iris, but with negative result. Eye rubbing
Table 5 shows that the keratoconus patients really did rub their eyes more often than the other mentally retarded, both among patients with and without Down’s syndrome ( P = 0.008 in both groups). Treatment
Four of the bilateral keratoconus patients were operated. Epikeratophakia was performed in three cases, while a penetrating keratoplasty was done in the fourth patient.
Discussion The prevalence of keratoconus among patients with Down’s syndrome has usually been reported to be 2-15%(Skeller & 0ster 1951; Cullen & Butler 1963; Levy 1984; Shapiro & France 1985; Riise 1986; Prokesova et al. 1990). Thus, the prevalence of 20% in our material is high compared with earlier reports. However, Jacobson (1988) has reported an exceptionally high prevalence of keratoconus (30%)among 50 patients with Down’s syndrome, but of the above mentioned authors, only Jacobson performed keratometry in a number of her patients. This fact could in part explain the high figure of keratoconus in her material. Our study also revealed a remarkably high prevalence (5.5%)of keratoconus among the mentally retarded without Down’s syndrome. This could indicate a common, but yet unknown cause for the mental retardation and the corneal defect.
Table 5. Frequency of eye rubbing in 46 mentally retarded patients.
8
Acta Ophthal. 70.1
Normal
Often
Very often
(Yo)
(04
(Yo)
113
It is interesting that pathology of the iris and the pupil has been reported in association with keratoconus (Urrets-Zavalia1963; Bertelsen & Seim 1974; Davies & Ruben 1975; Baumann & Insler 1985). Embryologically,the corneal endothelium, the corneal stroma and the iris stroma are derived from the same tissue, namely, the neural crest cells. Thus, it is not surprising that iris pathology may be encountered in keratoconus patients. In our material 6 of the 16 patients with keratoconus cooperated sufficiently to be examined for translucency of the iris, but this phenomenon could not be demonstrated. Keratoconus is usually a bilateral disorder. With the exception of Walsh (1981), the prevalence of unilateral cases is generally estimated to be 10-15Yo (Amsler 1961; Ihalainen 1986). In contrast, 50% of the keratoconus cases in the present material were unilateral. In six of these unilateral cases the refractive state of the fellow eye could be assessed by retinoscopy, thus ensuring that these cases were truely unilateral. Eye rubbing occurred significantly more frequently in the keratoconus group than among the other mentally retarded patients. This may indicate an etiological significance of eye rubbing in the development of keratoconus in patients both with and without Down’s syndrome. However, as commonly experienced during keratoplastic surgery, the consistency and mechanical properties in the conical cornea in patients with Down’s syndrome, as well as in a number of other mentally retarded, appear to differ from those present in a ‘normal’ keratoconus cornea. Hence, the cornea of the mentally retarded patients is probably more vulnerable to mechanical trauma. Therfore, there is obviously not one single causal factor in the pathogenesis of keratoconus, but both genetic and environmental factors are probably of importance.
References Amsler M (1961): Quelques donnees du probleme. Bull SOCBelge Ophthalmol 129: 331-354. Baumann J & Insler M S (1985):Pupillary abnormalities in keratoconus. AM Ophthalmol 17: 766-767. Bertelsen T I & Seim V (1974):The cause of irreversible mydriasis following keratoplasty in keratoconus: a preliminary report. Ophthalmic Surg 5: 56-58. Cullen J F & Butler H G (1963):Mongolism (Down’s syndrome) and keratoconus. BrJ Ophthalmol47: 321-330. Davies P D & Ruben M (1975):The paretic pupil: its incidence and aetiology after keratoplasty for keratoconus. Br J Ophthalmol59: 223-228. Ihalainen A (1986):Clinical and epidemiological features of keratoconus. Genetic and external factors in the pathogenesis of the disease. Acta Ophthalmol (Copenh). Suppl 178: 1-66. Jacobson L (1988): Ophthalmology in mentally retarded adults. Acta Ophthalmol (Copenh) 66: 457-462. Levy B (1984):Incidence of oculo-visual anomalies in an adult population of mentally retarded persons. Am J Optom Physiol Opt 61: 324-326. Prokesova V, Kriz S, Berg L & Halvorsen I (1990):0yeunders~kelsehos psykisk utviklingshemmede i sentralinstitusjon. Tidsskr Nor Laegeforen 110: 1659-1662. Rados A (1948): Conical cornea and mongolism. Arch Ophthalmol40: 454-478. Riise R (1986): Synsfunksjonen ved Down syndrom. Tidsskr Nor Laegeforen 106: 317-319. Shapiro M B & France T D (1985):The ocular features of Down’s syndrome. Am J Ophthalmol99: 659-663. Skeller E & aster J (1951):Eye symptoms in mongolism. Acta Ophthalmol (Copenh)29: 149-161. Urrets-Zavalia A (1963):Fixed, dilated pupil, iris atrophy and secondary glaucoma. A distinct clinical entity following penetrating keratoplasty in keratoconus. Am J Ophthalmol 56: 257-264. Walsh S Z (1981): Keratoconus and blindness in 469 institutionalised subjects with Down’s syndrome and other causes of mental retardation. J Ment Defic Res 25: 243-251. Received on May 27th, 1991. Author’s address:
Acknowledgment This study was carried out with financial support from Riksforeningen mot blindhet og svaksyn.
114
Olav H. Haugen, Department of Ophthalmology, University of Bergen, N-5021 Bergen, Norway.
